# Hey Werewolf, confusion about L-R...



## Ge0

I've read through tons of messages regarding using rear fill with the difference signal of L-R. I like the concept and want to try it.

My confusion. How to create the signal at he input to the Zapco amps. I need to subtract the two signals. How do I get the inverse of the right signal? I've read explainations but am still confused for some fuggin reason.

In my system I am taking the bridged outputs from my factory amp into Zapco BTL line transmitters. Signal goes balanced up to the amp.

It's supposed to be trivial with this setup but I'm having brain farts. Please elaborate. What can I do up front (at the input to the BTL's) to create this signal?

Ge0


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## Oliver

Geo,

I'm not 100% sure on this, so wait for WereWolf 

With balanced lines, you connect both positives,[ left and right ], to the same channel input.
As opposed to connecting left positive and left negative.
Since the processor is going to check the wires coming in for differences and then put out its' signal, it will subtract one signal from the other signal, leaving you with what you desire.


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## drake78

wolfie only comes out when there's a full moon


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## Whiterabbit

we covered this. your balenced signal already contains the inverse signal. A balenced transmission consists of an L+ and an L- signal. likewise R+ and R-.

On the recieving end, the device subtracts the two, giving you L+ - L- = 2L. Any noise that was induced into the cable will be done equally to both legs and is also subtracted: N+ - N+ = 0.

cool!

So to achieve the L-R signal, simply take whatever device recieves the Balenced transmission and converts it to standard. Rather than the standard method of wiring, Wire L+ to the L+ input, but wire R+ where L- would go. When the signals are internall subtracted, you end up with L+ - R+ = L-R

cake


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## matdotcom2000

Honestly I did not understand this until I plugged my home theater speakers in like 4 different ways


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## Oliver

Ge0 said:


> I've read through tons of messages regarding using rear fill with the difference signal of L-R. I like the concept and want to try it.
> 
> My confusion. How to create the signal at he input to the Zapco amps. I need to subtract the two signals. How do I get the inverse of the right signal? I've read explainations but am still confused for some fuggin reason.
> 
> In my system I am taking the bridged outputs from my factory amp into Zapco BTL line transmitters. Signal goes balanced up to the amp.
> 
> It's supposed to be trivial with this setup but I'm having brain farts. Please elaborate. What can I do up front (at the input to the BTL's) to create this signal?
> 
> Ge0


If I understand this concept, plus seeing what Whiterabbit posted.
For you the signal reversal will take place,[ swapping wires ], in between the balanced line transmitter and the amplifier inputs.

Quick question, does "your" amplifier have to come before the signal switch?

I would think that the ideally the signal would come balanced out of something upstream of the BTL, then get subtracteded,{ l+ {-}r+ }going into the BTL! What I'm getting at, is there a brainbox to do the neccessary processing at the point you are attempting to do it downstream?


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## Oliver

The effect is caused by the inherent capability of the balanced device to check both inputs on a channel and make the neccessary adjustments to the signal, normally it would see a negative and a positive input and then what ever was not common to both would be rejected.

In this instance it will reject the portion of the signal that is not common to both left positive and right positive leaving you with left minus right signal information, which you will then need to time delay beyond the Haas !


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## Guest

you guys got it right


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## ErinH

werewolf said:


> you guys got it right


Good. Now, does someone care to explain what this thread is about in the first place? :blush:


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## Xander

bikinpunk said:


> Good. Now, does someone care to explain what this thread is about in the first place? :blush:


I believe they are using a signal for rear fill which consists of a L channel signal - a R channel signal, so it takes out centered vocals and leaves you with some ambience? I'm not sure either?


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## chad

Xander said:


> I believe they are using a signal for rear fill which consists of a L channel signal - a R channel signal, so it takes out centered vocals and leaves you with some ambience? I'm not sure either?


yessir


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## ErinH

Xander said:


> L channel signal - a R channel signal


You mean left (minus) right?

How does this work exactly? I mean, what is the theory here?


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## chad

bikinpunk said:


> You mean left (minus) right?
> 
> How does this work exactly? I mean, what is the theory here?


You combine L in phase with R out of phase, So you are adding (L)+(-R)... Mmm Kay? Now anything that is L+R, or panned dead center will be canceled out because in the summing it will net 0. If something is panned, say 1 dB in one direction then the result of the summing will cause it to have a 1 dB level over the CMRR of the receiving device. Anything panned hard right or left will result in full output. 

But that's not the secret to the sauce. True Reverb is NOT L+R, it may get there in the space-time continuum but most of the time it's all over the place, because of this nearly all reverb in a recording will be reproduced by the front AND rear speakers in this application, anything ambient, that is allowed to float to "widen the stage" will go to the rears.

Remember old-skool first gen Dolby surround? That's it!

Chad


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## Guest

bikinpunk said:


> You mean left (minus) right?
> 
> How does this work exactly? I mean, what is the theory here?


look for the long threads on "rear fill" ... yeah, that "terrible" thing that's often categorically dismissed without understanding its many flavors


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## ErinH

chad said:


> You combine L in phase with R out of phase, So you are adding (L)+(-R)... Mmm Kay? Now anything that is L+R, or panned dead center will be canceled out because in the summing it will net 0. If something is panned, say 1 dB in one direction then the result of the summing will cause it to have a 1 dB level over the CMRR of the receiving device. Anything panned hard right or left will result in full output.
> 
> But that's not the secret to the sauce. True Reverb is NOT L+R, it may get there in the space-time continuum but most of the time it's all over the place, because of this nearly all reverb in a recording will be reproduced by the front AND rear speakers in this application, anything ambient, that is allowed to float to "widen the stage" will go to the rears.
> 
> Remember old-skool first gen Dolby surround? That's it!
> 
> Chad



cool. so, the combination of L+ and R- cancels out center and leaves only the furthest left & right signal, thus creating 'ambience' like Xander said?


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## chad

bikinpunk said:


> cool. so, the combination of L+ and R- cancels out center and leaves only the furthest left & right signal, thus creating 'ambience' like Xander said?



Not just the furthest left or right, think about it this way, A true L-R will end up being 3 dB louder than a hard pan  Hard pan is XV-0=XV L-R int eh recording will Be Xv+XV=2XV and we know that doubling of voltage into a known inpedance will result in twice the power that equates to 3dB.


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## freeride1685

as i was reading through the article werewolf cited, i was under the impression that the gentleman did not suggest switching the two L-R signals out of phase. from what i gathered he suggested against switching phase to keep the bass up but then decorrelating the two rears with the use of different amounts of delay, namely 18 and 26ms if i remember correctly.

i have heard lots of people suggest to switch one signal out of phase and i was wondering if those suggestions were absolutely necessary for this effect.

i suppose switching the signals out of phase and then EQing the bass response could work also....


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## envisionelec

chad said:


> Remember old-skool first gen Dolby surround? That's it!
> 
> Chad


Sort of. Going from memory; Dolby implemented a 7kHz LPF and some additional delay, but that was the gist. My brother designed his own DSD when he was 12 from the guts of a Pioneer Reverb unit and some S-K filters. We were dirt poor, but creative.  The real name of that connection is the Hafler. I remember seeing it in one of my 1968 Radio-Electronics mags and trying it when I was 14. I had a room full of speakers wired series-parallel. I probably had 25 speakers...but just two sounded better than all of them, so I had a garage sale


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## Ge0

Hic said:


> Geo,
> 
> I'm not 100% sure on this, so wait for WereWolf
> 
> With balanced lines, you connect both positives,[ left and right ], to the same channel input.
> As opposed to connecting left positive and left negative.
> Since the processor is going to check the wires coming in for differences and then put out its' signal, it will subtract one signal from the other signal, leaving you with what you desire.


Yes, the front end of a balanced line transmitter is a DIFFERENCE amplifier. The BTL itself passes one straight signal to one of the difference amplifiers inputs, and the INVERSE of the straight signal to the other input to the difference amplifier. This is all internal to the BTL. 

Ge0


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## chad

ezaudio said:


> Sort of. Going from memory; Dolby implemented a 7kHz LPF and some additional delay, but that was the gist.


That makes sense, whew, it's been a while!



ezaudio said:


> My brother designed his own DSD when he was 12 from the guts of a Pioneer Reverb unit and some S-K filters. We were dirt poor, but creative.  The real name of that connection is the Hafler. I remember seeing it in one of my 1968 Radio-Electronics mags and trying it when I was 14. I had a room full of speakers wired series-parallel. I probably had 25 speakers...but just two sounded better than all of them, so I had a garage sale



Ahhh, the memories.... Poverty, second to Necessity, as the mother of invention


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## Guest

yes, the oldest version is known as the "Hafler Matrix" ... Hafler simply connected a single rear speaker across the L+/R+ stereo outputs, with a pad for attenuation.

But we can do better, by not only forming an actively attenuated L-R, but also bandlimiting (like Dolby), and perhaps most importantly ... adding delay to, or beyond, the precedence (Haas) effect (in the vicinity of 20msec). Remember the goal of clever rear fill is NOT to help the back seat passengers, and NOT to "fill the cabin with music" in a way that detracts or smears the front stage, but rather to give the illusion of listening in a larger acoustic space. Proper delay will enhance, not detract from, the front stage.

As far as driving _two_ rear speakers, what we really strive for is some _decorrelation_ between them. Couple easy approximations include : simple inversion (one side is L-R, other is R-L), which will suffer from decreased midbass in the rears, simply adding different delays to the 2 different rears (described in detail in the paper quoted in one of the many long rear fill threads), or getting really fancy ... like a 90 degree phase shift between the rears  Problem is, Hilbert Transformers are not (yet) readily available in most car audio processors


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## freeride1685

werewolf said:


> As far as driving _two_ rear speakers, what we really strive for is some _decorrelation_ between them. Couple easy approximations include : simple inversion (one side is L-R, other is R-L), which will suffer from decreased midbass in the rears, simply adding different delays to the 2 different rears


is it only necessary to do one of these techniques? or would both simultaneously be effective as well?

if only one, which do you recommend as far as effectiveness?


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## Guest

freeride1685 said:


> is it only necessary to do one of these techniques? or would both simultaneously be effective as well?
> 
> if only one, which do you recommend as far as effectiveness?


if you have the processing power to add different delays for each of the two rear speakers, i would definitely try that. But a simple inversion ... or, 180 degree phase shift ... is stupid-easy to try.

So the answer is : this requires lots of experimentation to optimize. First you must create and process the L-R signal. You MUST experiment with proper attenaution, bandlimiting and delay. Guidelines can be offered ... bandlimit to somewhere between 3~7kHz, delay somewhere around 20 msec, attenuate so the effect is subtle, but noticeable. If you have a processor that can give different delays for each of the two rears, give that a try. If not, the simple 180 degree phase shift is easy to do, by simply inverting the leads to the other rear speaker (to be wired in parallel or series with the first rear speaker).


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## backwoods

channel steering on top of the delay is really cool. You can actually "move" the corners of your vehicle to/from. 

It has really been the neatest features and idea's I have played with in quite some time. 

amazingly, you can "shift" the stage to sound as if you are sitting center, or near the left aisle at a show. 

I was playing with phase adjustment the other day between the two rear fill speakers.

One of the great benefits of using the behringer or other PA processors in a car...


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## Whiterabbit

to my knowledge, the behringer phase shifter only works at peak effectiveness at the LP crossover frequency.


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## Guest

backwoods said:


> channel steering on top of the delay is really cool. You can actually "move" the corners of your vehicle to/from.
> 
> It has really been the neatest features and idea's I have played with in quite some time.
> 
> amazingly, you can "shift" the stage to sound as if you are sitting center, or near the left aisle at a show.
> 
> I was playing with phase adjustment the other day between the two rear fill speakers.
> 
> One of the great benefits of using the behringer or other PA processors in a car...


no frikn way !!! 

i mean ... rear fill sux ass !!! 

.... ummm, doesn't it ??? that's what all the car audio experts say  

hee hee, sorry i couldn't resist


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## demon2091tb

And to think i understood everybit of Whiterabbits post, and even moreso Chad's......So is this the key in pulling off the shyed away rear fill, and also moreso what quality of drivers should be USED for this rear fill, since the farthest pans of Extreem right and Extreem left are used, it sounds to me as though the only info that is played on these rear speakers is just a wrap around effect in a sense, But what if your running a 3way upfront and end up putting a wide range driver in the back with a different sonic signature, what happens....and how do you correct it?

Correct me if i'm wrong.

So is it just the far extreem signals and in essence the summed center is phase shifted and cancled so that only the outside is played? Just trying to understand.


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## the other hated guy

well boys...if you want my opinion on this...and I'm sure this isn't going to be a popular one...

not many can get a 2 or 3way frontage right....so why add more variables?


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## freeride1685

as cited in the original article posted by werewolf:

"....Second, the in-room frequency response of each rear speaker needs to be well matched to its corresponding front speaker. This means that the in-room frequency response of the left-rear speaker match the in-room frequency response of the left-front speaker. The right-rear and right-front speakers must be similarly matched...."

obvi, if this was in a house then it would make more sense because you can position them more precisely. but that being said, it will still make a difference for the car environment because processing cannot make up for the difference in speaker design. as was ellaborated in another post, the processing of totally different speakers will not account for the _non-linear_ characteristics of each transducer, thus suggesting that it will be even more important to match fronts and rears in this kind of setup as the whole focus of the surround signal is on subtleties and ambience.

keep in mind, though....that's easy for me to say since before i came to this forum i bought 4 identical speakers since i thought that was the best thing in the whole world to do.   i would suggest to at least stick within the same manufacturer, same model year, etc. to match that sound.


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## Ge0

I understand now. I derive the L-R signal through manipulation of my balanced line stereo pair. I was hoping to get by not chopping up a Symbilink cable or creating a custom break out box. But, it sounds like if I want to play around with this, that's what I'll have to do.

In essence, I am taking a stereo pair, combining it into a L-R monaural signal, then feeding the identical monaural signal into each of the two rear input channels on the amp.

Each rear input channel to the amp recieves L+ on its positive feed and R+ on its negative feed. The differential amplifier at the amp inputs will elimininate common mode stuff which is any signal that is the same between L+ and R+ (namely vocals that are centered) and leaves unique material that would normally go hard right and hard left. 

It helped me to draw this out. L- and R- coming out of the balanced line transmitters are left unterminated. L+ is split and sent to the left and right + inputs on the amp. R+ is split and sent to the left and right - inputs on the amp. 

Does this capture things adequately?

Once I have this I can start to play around with bandlimiting, time delay, and amplitude. All of which are functions my amp can easily manipulate.

Ge0


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## Oliver

If i understand what you're saying, then yes you have it!!


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## Oliver

up !


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## Ge0

Still haven't got ahold of a few Symbilink cables I can chop up to run this experiment. As soon as i see some dirt cheap, or free, I'll pounce on this like white on rice.

I'm wondering something though. If the primary reason for using L-R is to eliminate vocals (which is the primary center information) from the mix, couldn't I run an experiment where I create a damn steep and deep notch filter between say 300Hz and 1KHz to knock out a lot of those vocals? I could then bandlimit, attenuate, and delay using other functions of my amp.

Ge0


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## matdotcom2000

My plan is to run 1 kac-x4r and from the front 1 on my h701 then split signal from the RCAs. So now I have two L/R signals. Then on one of the L/R I am going to make some special RCA cables and do l-r and r-l and hook it up to the amplifier. Because of the flexibility of the amplifier I will be able to crossover and do time alignment for my tweets from the L/R RCA and my rearfill from the l-r and r-l RCA.


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## SSSnake

Unless the DSP in the Kenwood amp gives you the ability to do l-r and r-l those are going to have to be some mighty special RCA cables. RCAs are unbalanced and cannot be combined to provide l-r and r-l signals.

Since this topic has resurfaced... is anyone successfully using the dolby settings in a 701 to pull this off?

Ge0,

Don't waste your time... The filter you mentioned is not going to do what you want. Envision a midbass and tweeter on left and right and a full range center. Not the best solution for imaging.


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## matdotcom2000

I left out I am putting an L-pad on each speaker. So I would be able to adjust everything. I think it will be a +2db to -6db. I think that would be enough to balance the left and right side from each speaker.

BTW I did a little test on my home stereo to try to get ambiant sound this way and it there I figure with a little tweeking I should be able to get it right. I hope. Unless someone knows how to unlock the secrets of the h701 rear channel's dobly digital settings


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## Ge0

Someone with a conventional 2 channel STEREO system try this... No multi-channel Dolby Digital hocus pocus at this time. At first it might be easier to do this at home than in your car if you have that luxury. This is something I tried as a teenager with mom and dads stereo but never really understood. Now that I think about it, this may apply to this thread.

Keep both rear fill channels electrically in phase. Disconnect the negative leads of each speaker at the amp. Tie the negative leads together. The positive leads should still be wired to the amp as normal. Play music through the rears now. What do you hear? Vocals damn near cancel out but ambience is left? You should hear a close proximity of. Voices might have a bit of echo left and sound far off in the distance.

Yes, you will still hear some vocal. This is information unique to one channel or the other, but, not both summed. If your Left and Right channels are not level matched closely you'll hear more voice than if they were level matched perfectly. This is because a perfect cancellation has not occured.

What is going on here? The speakers are bridged across two channels where one channel IS NOT inverted (like they typically are). Any signal that is the same between both speakers is cancelled out while anything that was unique to either channel is played. Lets simplify things by looking at pure sinusoidal tones. If a tone is played at the same amplitude on each channel, and the speaker is tied across the positive feeds for each channel, no potential voltage will form across the speaker. Now, if the left channel plays a tone, and the right channel does not, both speakers in this configuration will play the tone on the left channel. Think about it. Voltage peaks on the left and remains zero on the right. A potential voltage developed across the speakers and they react accordingly. The EXACT same thing applies when you play that tone on the right channel and leave the left channel mute.

Essentially what you wind up with is a mono channel rear fill with L+R information extracted. 

COULD THIS BE L-R WITHOUT FUNKY SIGNAL MANIPULATION!!!

This can get tricky. Those of you wanting to do this with your car amp need to know what you have. Most car amps automatically invert one of the channels in a stereo pair and have you wire the speaker 180 degrees out of phase to make bridging easier. That way they don't need to include a bridging switch on the amp. If your amp DOES NOT have a switch on it to bridge two channels, assume one of the channels is inverted.

You'll need to bridge the channels like you normally would (picture wiring two subs in series across a bridged channel). This will give you a conventional mono bridged output. However, you'll need to invert the input signal upstream on one channel or the other to gain the cancellation affect. This is easy to do for someone with a signal processsor that allows this. It is not so easy for someone without a signal processors that will allow you to invert a channel.

Anybody want to punch a hole in my theory?

Ge0


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## matdotcom2000

Well what I did a few weeks ago I hooked up the speakers keeping the positives as normal on the L and R channels but taking the negative from the R and hooking it up to the left and visversa for the L to the R negative. And I got ambiance but from what I have understood is that you would also need some T/A and a way to Adjust the left and right channel which is where the KAC-X4R comes in with the T/A and the L-pads for adjusting. I was going to do the reversal on the RCAs instead of on the amp because I did not know what effect it would have on the impedance.


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## npdang

I'd be interested in comparing results with anyone whose attempted this.


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## Ge0

npdang said:


> I'd be interested in comparing results with anyone whose attempted this.


What do you mean by comparing results? Have you tried this? 

I'm going to attempt the speaker trick I mentioned later this afternoon. I'll post my findings tonight. But, to do the signal manipulation (with balanced inputs) I'll need a sacrificial Symbilink cable. I just can't see spending $40 on a cable I'm going to cut up. My pockets are empty from Christmas.

The whole reason I use rear fill now is because I like the added ambience it offers. To me, it seems more realistic. The only downfall of using rear fill I encounter now is it seems to draw the centered image more towards me (not behind me like others have suggested). Centered vocals no longer sound as deep. Kind of like they are standing right there on the dash, not out in the middle of the hood. Balancing things carefully by attenuating the rears helps bump the image back out but you loose some of the ambience effect.

I have high hopes for trying this experiment.

Ge0


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## Ge0

matdotcom2000 said:


> Well what I did a few weeks ago I hooked up the speakers keeping the positives as normal on the L and R channels but taking the negative from the R and hooking it up to the left and visversa for the L to the R negative. And I got ambiance but from what I have understood is that you would also need some T/A and a way to Adjust the left and right channel which is where the KAC-X4R comes in with the T/A and the L-pads for adjusting. I was going to do the reversal on the RCAs instead of on the amp because I did not know what effect it would have on the impedance.


The originator of this discussion, Werewolf, mentions that to get the full effect you need to delay the rears from the fronts to some degree (where time alignment comes into play), bandlimit the signal (low pass and high pass crossovers), and attenuate the signal so it will blend well (simple gain adjustments).

I am fortunate enough to have an amp with all these functions a few mouse clicks away. Other methods to achieve the goal exist, they just aren't as straight forward.

The reversal you mention on the RCA's will not work for reasons already mentioned earlier in the thread. I wanted to get by the easy way and try this when I originally started the thread. The affect this has on impedance? Well, you're wiring two speakers in series. The impedance you amps output will see is doubled.

Ge0


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## durwood

Ge0 said:


> Anybody want to punch a hole in my theory?


This theory you speak of is called the "hafler effect" or "hafler circuit". 

It's even easier to do with a headunit or a non-bridgeable amp.

http://sound.westhost.com/project18.htm


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## Ge0

durwood said:


> This theory you speak of is called the "hafler effect" or "hafler circuit".
> 
> It's even easier to do with a headunit or a non-bridgeable amp.
> 
> http://sound.westhost.com/project18.htm


I didn't think a pimply faced teenager screwing around with mom and dads stereo would develop a breakthough in audio engineering. Figures someone has already done this and the idea has been around for years.

Ge0


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## thatvan

Try an older PS/2 cable instead of the Symbilink. 

BTW Geo, are you the lemon of old?


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## durwood

Ge0 said:


> I didn't think a pimply faced teenager screwing around with mom and dads stereo would develop a breakthough in audio engineering. Figures someone has already done this and the idea has been around for years.
> 
> Ge0



 Didn't mean to spoil your revelations, at least you weren't riding around with a stolen dummy strapped to your bike eating skittles.

Ain't that the truth, you stumble upon something interesting and of course some yahoo before you thought of it already.:blush:


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## Ge0

thatvan said:


> Try an older PS/2 cable instead of the Symbilink.
> 
> BTW Geo, are you the lemon of old?


True, I don't believe the BTL's are powered off the Symbilink. I'll have to dig through the 1/2 ton of old and used computer parts I have laying around to see if I have an extension cable (cause I'll need the mating end too).

I have no clue what you are talking about with old Lemons. Guess not...

Thanks for the idea. I forgot about the PS/2 cable trick.

Ge0


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## Ge0

durwood said:


> Didn't mean to spoil your revelations, at least you weren't riding around with a stolen dummy strapped to your bike eating skittles.


Damn Durwood, I think I just pissed myself   ROTFL!!!

Ge0


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## Oliver

Mannequin , not dummy !


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## Ge0

Hic said:


> Mannequin , not dummy !


Yeah, a scantly clad one in Sears sexiest lingerie .

Ge0


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## backwoods

Hic said:


> Mannequin , not dummy !


 
you sure?


which one is doing the pedaling?


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## Ge0

backwoods said:


> you sure?
> 
> which one is doing the pedaling?


Heh, this is probably confusing the piss out of you and everyone else.

To make a long story short, I got snot flying drunk one night a coined this masterpiece:

http://www.diymobileaudio.com/forum/showpost.php?p=255375&postcount=60

I think it was so off the wall that it sticks in peoples memories.

Ge0


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## Ge0

Where is Werewolf by the way? I noticed something funky going on with his user name. Kind of like he is no longer a member? Can't click on it...

Ge0


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## Ge0

My initial impressions after modifying my system to perform L-R rear fill using the speaker output manipulation method (i.e. the Hafler Effect) I mentioned earlier today:

Wiring this up is a breeze. Simply tie the rear fill speakers in series and bridge them across two channels of the amp. Next, use your handy dandy signal proccessor to flip the phase of one channel by 180 degrees to overcome the inversion the amp already made.

Per others recommendations I then set crossovers to bandlimit the signal. The high pass is set to 100Hz at 24db/octave. The lowpass is set to 7KHz at 12db/octave (mMy rear fill plays full range through a mid and tweet combo. So, I don't necessarily need to worry about playing too high of frequencies with my mids). I don't believe there is an exact science on how to set the bandpass. But, I felt this was as good of a starting point as any. If someone wants to offer advice regarding the reason for setting specific crossover points in this application I would appreciate it. 

I did not change any volume levels (front vs. rear) at this time.

Preliminary time delay of the bridged channel was set to 20mS. This will need some manipulation +/- a few milliseconds so I don't cross outside the bounds of the Haas Effect yet still obtain the maximum amount of delay.

What I found. When the gains are dialed in to perfectly match the cancellation of vocals is VERY pronounced. All you hear is a faint echo of vocals in the background. Yet, sounds from either side still retain their original volume level. However, stray a little bit from a perfect balance and the cancellation goes to ****. Same goes for setting time delay and crossovers. They must match as close as possible or the cancellation effect collapses.

At first my front stage level was set well above the rear fill (the same setup I used with conventional rear fill). I noticed no significant change. But, as I increased the level of the rear fill, the front soundstage seemed to open up and come alive. It no longer sounded as if it was sitting in front of me on top of my dashboard. It started to sense that I was in the room of the performance. BTW: I could obtain the same effect with delayed conventional rear fill, but read on... I adjusted the level of rear fill a little higher with respect to the front stage. The front stage started to get deeper!!! I could dial this in to where the vocals seemed to be off in the distance. However, there was a limit to how deep everything on either side (non centered info) could get. Adjust the level of the rear fill even higher yet with respect to the fronts and the stage soon dives backwards. So, there is a delicate balance between how deep you want to get and a total elimination of any benefits this may offer. This is something I could not do with conventional rear fill. 

Ultimately, through level adjustments of the rear fill alone, I decided to place my front stage out just shy of the center of my hood. This was a good balance between the depth of vocals and the rest of the music going on. After all, what performer actually sings 20ft BEHIND the band? 

As stated earlier, you get more than just added stage depth. You get ambience. I don't know how to explain it much more than music just seems more live, more real. Like I said earlier in this post, it sounds like you are sitting in the performance hall, not just listening to it through speakers in front of you.

This was my impression from my first few hours monkeying with L-R rear fill. I hope to do plenty of experimentation with this to squeeze all the performance I can out of it in the weeks to come.

To Sum things up, here is what you will need to try this experiment:

1.) A bridged amp channel with rear fill speakers wired in series across the bridge.

2.) The ability to electronically invert one channel to overcome the inherant inversion that occurs in an amplifier when channels are bridged. Does not apply to amps that are not bridgable or bridge through a switch. Leave the switch off!

3.) The ability to bandpass the bridged channel with highpass and lowpass crossovers.

4.) The ability to add time delay (ranging from 10 to 30 mS I presume) to the bridged channel.

5.) The ability to control the gain of the bridged channel. This should be a no brainer using an amps sensitivity controls.

And that is all for now folks...

Ge0


----------



## SSSnake

Geo you beat me to it. Many years ago I tried this to approach generate a rear fill channel. The approach had promise but in the 90s time delay was unavailable (at least to me) and I never to could get it to quite sound right. I'm glad to see you are having luck with this approach. It looks like I need a few more channels of processing (sounds like an excuse for that in car computer that I've been drooling over).


----------



## matdotcom2000

Ge0, you plugin L/R into the bridged channel but you dont need to have control level of the individual left and right channels as fars as both T/A and volume adjustment?????


----------



## Ge0

matdotcom2000 said:


> Ge0, you plugin L/R into the bridged channel but you dont need to have control level of the individual left and right channels as fars as both T/A and volume adjustment?????


I did not totally understand your question but will do my best to answer.

You DO NOT need independant L/R control over the bridged channel IF the single control allows the channels to track each other dman near perfectly. IF they do not track each other perfectly (i.e. a slight gain mismatch between channels) then the effect will not work.

As little as a 1dB difference between channels will ruin it for you. I've worked on amps quite a bit in my career. I know that channels are rarely perfectly balanced when the amp has a single shared gain control for both channels. Obviously some are better than others. All I am saying that if this is off by too much, you'll never get this to work. You'll sit and scratch your ass, errr, head wondering why.

As far as time delay. I can set time delay for each channel individually. I had my rear fill channels set a few milliseconds apart originally to "align them". I tried to simply add 20mS onto each channel. The cancellation was not working. I eliminated the 2mS difference between channels so they were both set at 20mS exactly and it worked great.

Ge0
Ge0


----------



## matdotcom2000

I understand now thanks, hey if I put a Y cable on balanced outs does the signal become unbalanced???


----------



## Ge0

matdotcom2000 said:


> I understand now thanks, hey if I put a Y cable on balanced outs does the signal become unbalanced???


That all depends on if you use a balanced or non-balanced y-cable.

Ge0


----------



## matdotcom2000

Also can you switch the phaze in the actual wiring of the speaker when wiring in series???


----------



## Ge0

matdotcom2000 said:


> Also can you switch the phaze in the actual wiring of the speaker when wiring in series???


Huh?

Switch phase of the series combo or the phase of an individual driver in the series combo?

ge0


----------



## Ge0

Man I'm being a post whore with this thread...

I found a reason to roll the high end off earlier than 7KHz at 12db/octave this morning on my commute into work. On one track cymbal crashes and other high frequency stuff appeared like it was coming from beside me or behind me, not in front of me. Although this is a neat effect, I still want to maintain a frontal stage. Vocals and center channel info was still locked in front and center.

Ge0


----------



## durwood

Ge0 said:


> Where is Werewolf by the way? I noticed something funky going on with his user name. Kind of like he is no longer a member? Can't click on it...
> 
> Ge0


He left after the HH>Chucknorris (attack on the other hated guy) debacle. I guess he asked Ant to remove his account. There was a thread about it in OT. From what was said, he was also the owner of the Kipple npdang uses and took that as well, so more more kipple....I think. 

/end rumor


----------



## Ge0

durwood said:


> He left after the HH>Chucknorris (attack on the other hated guy) debacle. I guess he asked Ant to remove his account. There was a thread about it in OT. From what was said, he was also the owner of the Kipple npdang uses and took that as well, so more more kipple....I think.
> 
> /end rumor


I did not know about that. I read through some of those dated posts.

Question, it is obvious that this Chucknorris ******* only joined the forum to give Randy a hard time (for what reason who the **** knows). Why wouldn't NPDANG just ban him and be done with it? Why loose a key member to the forum over something so stupid? I'm happy Randy see's this **** for what it is and did not decide to leave too.

It's a shame, I really liked werewolf. I had some ideas I wanted to bounce off him for modular amps. I also wanted his opinions about the Hafler effect.

Oh well, maybe I can catch up with him over at ECA or something...

Ge0


----------



## chad

Ge0 said:


> It's a shame, I really liked werewolf. I had some ideas I wanted to bounce off him for modular amps. I also wanted his opinions about the Hafler effect.
> 
> Oh well, maybe I can catch up with him over at ECA or something...
> 
> Ge0


Yeah no **** man. I don't really hang at ECA, have an account but really don't subscribe to their ideas sometimes. Evidently a lot of the same people, which, I like. Combine that with the knee-jerk mob-mentality that can sometimes happen and my inability to keep my pie-hole shut and you just lit the fuse on a disaster waiting to happen.

Chad


----------



## Ge0

chad said:


> Combine that with the knee-jerk mob-mentality that can sometimes happen and my inability to keep my pie-hole shut and you just lit the fuse on a disaster waiting to happen.
> 
> Chad


Just out of curiosity, is that what prompted the change to your avitar, you know, "keeping your pie-hole shut"  .

Ge0


----------



## GlasSman

Ge0 said:


> Just out of curiosity, is that what prompted the change to your avitar, you know, "keeping your pie-hole shut"  .
> 
> Ge0


 

Nice.


----------



## Oliver

edit:
Haas Effect Also called the precedence effect, describes the human psychoacoustic phenomena of correctly identifying the direction of a sound source heard in both ears but arriving at different times. Due to the head's geometry (two ears spaced apart, separated by a barrier) the direct sound from any source first enters the ear closest to the source, then the ear farthest away. The Haas Effect tells us that humans localize a sound source based upon the first arriving sound, if the subsequent arrivals are within 25-35 milliseconds. If the later arrivals are longer than this, then two distinct sounds are heard. The Haas Effect is true even when the second arrival is louder than the first (even by as much as 10 dB.). In


----------



## Ge0

GlasSman said:


> Nice.


Your  response just made me think of something. People can't see the smirk on your face when you post a light hearted joke on the internet. ****, I hope I didn't send Chad off the deep end.... Did not mean to offend anybody.

Ge0


----------



## Ge0

Hic said:


> edit:
> Haas Effect Also called the precedence effect, describes the human psychoacoustic phenomena of correctly identifying the direction of a sound source heard in both ears but arriving at different times. Due to the head's geometry (two ears spaced apart, separated by a barrier) the direct sound from any source first enters the ear closest to the source, then the ear farthest away. The Haas Effect tells us that humans localize a sound source based upon the first arriving sound, if the subsequent arrivals are within 25-35 milliseconds. If the later arrivals are longer than this, then two distinct sounds are heard. The Haas Effect is true even when the second arrival is louder than the first (even by as much as 10 dB.). In


Okey doke. Got that one handled. So what was your point?

Ge0


----------



## chad

Ge0 said:


> Your  response just made me think of something. People can't see the smirk on your face when you post a light hearted joke on the internet. ****, I hope I didn't send Chad off the deep end.... Did not mean to offend anybody.
> 
> Ge0


Hell No, It's easier for that guy to keep his pie hole shut because someone already knocked all his teeth out 

I've been meaning to PM Werewolf and see how he's doing but just have not for some reason. He's a good guy.

Chad


----------



## Ge0

chad said:


> Hell No, It's easier for that guy to keep his pie hole shut because someone already knocked all his teeth out
> 
> I've been meaning to PM Werewolf and see how he's doing but just have not for some reason. He's a good guy.
> 
> Chad


Hmmm, how to do a group "beg for forgiveness"?Do you think if we all got together and signed a Hallmark card to send to him he would come back? 

Ge0


----------



## chad

Ge0 said:


> Hmmm, how to do a group "beg for forgiveness"?Do you think if we all got together and signed a Hallmark card to send to him he would come back?
> 
> Ge0


No he's an Engineer, the most stubborn of stubborn people


----------



## Ge0

chad said:


> No he's an Engineer, the most stubborn of stubborn people


Hey, watch what you say about engineers sizzle chest...  

Ge0
Professional Engineer / Bullshitter...


----------



## Oliver

No point , geo  

This is what Rane list under Hafler:
Hafler, David (1919-2003) American engineer, inventor and member of the Audio Hall of Fame, considered one of the fathers of high fidelity. He founded Acrosound (1950), Dynaco (1954) and the David Hafler Company (1972). 

As far as a Hafler Effect, my seach revealed Nothing !

I thought that perhaps the Haas effect would suffice.


----------



## Ge0

Hic said:


> No point , geo
> 
> This is what Rane list under Hafler:
> Hafler, David (1919-2003) American engineer, inventor and member of the Audio Hall of Fame, considered one of the fathers of high fidelity. He founded Acrosound (1950), Dynaco (1954) and the David Hafler Company (1972).
> 
> As far as a Hafler Effect, my seach revealed Nothing !
> 
> I thought that perhaps the Haas effect would suffice.


The two are very different things. So far the direction of this thread is to use the Halfer effect to achieve the Haas effect. Look at the link to Elliot Sound Products audio pages Durwood posted earlier in this thread. It describes the Hafler thingy pretty good. You already read up on the Haas Effeect.

Ge0

Ge0


----------



## backwoods

I did the same in my truck, and first took impulse responses to get everything time aligned correctly, then added the 20 ms to the rears, Also, I was running each rear off its own individual channel and was able to match levels equally.

Once everything was equal and aligned, then playing with the delay, and level increments was much easier and quicker. 

There is a fine line as you stated to smearing the stage and also creating a nasty reverb or echo. 

But, once you get that sweet spot, it really is something to behold.

I'm currently trying to figure out a simplistic way to switch in my house from a normal HT into this type of sound for stereo.

Still thinking about how...


----------



## Oliver

OK , i saw where the Hafler Matrix was mentioned and the Hilbert transformer just above this:

So the answer is : this requires lots of experimentation to optimize. First you must create and process the L-R signal. You MUST experiment with proper attenaution, bandlimiting and delay. Guidelines can be offered ... bandlimit to somewhere between 3~7kHz, delay somewhere around 20 msec, attenuate so the effect is subtle, but noticeable. If you have a processor that can give different delays for each of the two rears, give that a try. If not, the simple 180 degree phase shift is easy to do, by simply inverting the leads to the other rear speaker (to be wired in parallel or series with the first rear speaker).

Which I interpret as:

1] create = blt used to make
2] attenuate = lessen output relative to front speakers
3] bandlimiting = definately not full range signal
4] delay = less than an echo and more than reverb
5] delay = ideal with use of a processor, less than ideal [ 180 degree phase shift ], invert positive and negative when hooking up second rearspeaker.


----------



## Ge0

Same bat time, same bat channel.

I've changed things up a little since I last posted. The speaker bridging trick was working. However, it was limiting me. I could not adjust attenuation, EQ, time alignment PER rear fill channel. To obtain ultimate control I needed to break the link.

So, I decided to feed the amp with L-R signals at the input per the advice winslow offered werewolf on ECA nearly a year ago.

Here is how I acheived this. It only applies to people who have balanced inputs on their amp at this time:

Cheap Symbilink cable:









Cut it in half and start soldering to protoboard. The R+ from the other side goes to L- on the amp side. The L+ from the other side goes to R- on the amp side. L- and R- are left unterminated at the other side (non amp side) of the cable:









Once the soldering is done, cut out only the board material needed:









Board material left over:









I love this gunk for a number of reasons. 









It works as a good encapsulant for strain relief:









Once the potting material dries, its time for an environmetal protection barrier. Glue impregnated heat shrink tubing!!!:


















Shrink it up, and pinch the ends off for a good seal:









Completed harness assembly:









Installed:









Well, how do I like this? To tell you the truth, right now it is not much different. I haven't had much of a chance to sit down and tweak it. However, when I get time to play be damn sure I'll post my results.


----------



## Gary S

I'm coming into this post a little late, so I'll just post some general thoughts until I can weave my way into the conversation. 

I was cruising the Ft. Lauderdale strip with matrix surround 20 years ago... even recommended the circuit to JL.. who now have it built-in to their 5-channel amplifier. What would you guys like to know about it  I guess at this age I don't run the risk anymore of competing, so i may as well spill the beans.  

A couple of points:

First of all, you guys are making this way too complicated... slow down! LOL! It's only rear channel matrix surround, as I like to call it. I don't see you guys getting so bent out of shape over your right verses left speaker, LOL!

- I am not sure why you guys feel the need for so much processing... for example... why do you wish to have a delay? You are not going to have more midbass... by it's very nature, the surround channel has very little bass... most of your bass is summed mono... this rear surround signal is an out of phase signal, summed bass automatically cancels. You just need strong midbass up front. Plus, if your goal is simply to ad fill without hurting the front stage, you could simply run the rears in conventional stereo with the delay. Furthermore, the delays built-in to home processors are primarily there as a band-aid for poor speaker placement... many people have the surrounds closer to them than the fronts... only if that's the case do you need delay. (I want to mention something here... dolby pro logic, circle surround, and other processors have extra filters and steering which may give better or worse results than a simple hafler hookup... you would have to try them to find out).

Ideally, the rear speakers should be identical... you would not use different right and left speakers... so why use different speakers in what essentially is a third channel? Do you smell what I'm cooking  That said, you can cheat a little here, at least to start with to get a taste of multi-channel sound in a car... because most of the surround information is midrange, and useful effects are centered around the vocal range, you can use high quality mids without tweeters... you don't want high frequencies out of the rear channel anyway, you won't like it. I think Dolby specs -6db at 7K low-pass filter. Some others have suggested a low-pass as low as 2k. I have had good results with mids that play up to at least 5k.

You are going to hate this, but... speaker placement in the rear is as important as the fronts... this means near-equal path lengths for the rears. If your rear speakers are in rear doors, rear sail panels, or a pick-up truck... delay may help a little but you may still have problems. A coupe with rear package shelf speakers will work well. A hatchback with mids flanking the sub(s) in a box can work... that's the way I do it now... even though my car has rear sails, those locations are poor.

Here is a tip... try setting all EQ's, tone, and boost controls to flat, see if it sounds better that way... especially on the surrounds, but on the front speakers too.

I would recommend equal power on the rears... same power as the fronts.

You definitely want to de-correlate the rears... this helps them to sound non-directional in nature. Even though the surround signal is mono and in theory you could run one speaker/channel, you need two speakers/two channels... one speaker is wired out of phase with the other... the right speaker gets a right-minus-left signal, the left speaker gets an out of phase left-minus-right.

There are many different ways to skin a cat... and to do matrix surround in a car. 

Re-wiring a balanced line or plug is just one way.

The hafler hookup is another... this is the way I have done it for 20 years. Problem is, most of the amps today are tri-mode or bridgeable just by hooking up the wires, because they have a phase inverter in one channel... hafler hookup won't work on those amps... you either need an amp without the phase inverter, or one with a switch to turn it off. Sony has a few 4-channel amps which, on the front channels, have no phase inverter. Perhaps it can be done with these amps. Watch your ohm load on the hafler hookup, it's like bridging... the amp "sees" half the ohm load. best thing to do is series wire, take the two speaker negative wires which would normally go to the amp and wire them together instead.

Head units... some CD players in the past supposedly had dolby processing built-in... I think kenwood and Clarion had one. I think you need dolby pro-logic, NOT Dolby Digital... Dolby Digital is Discrete, that is to say it is five or more encoded tracks, will only work with software which has the five or more encoded tracks, such as DVD's. 

Panasonic has a couple of decks with Circle Surround Automotive, not to be confused with SRS WOW.

As mentioned, JL Audio has a five-channel amp with a LEFT-MINUS-RIGHT switch for the rear channels. Just pop that baby in your car and you are ready to go.

There are also a couple Circle Surround half-din units. 

Lastly... you guys have no idea how good this is... stereo replaced mono back in the 60's/70's... 3 chanel sound is the real macoy... (I don't think you need 4-channel sound in a vehicle with the addition of a center channel... I believe this is more important in a home where you want to anchor the sound to the screen area, and make dialog more inteligable... and in a theater, you are trying to get coverage for seated listeners wall-to-wall... plus, in a car, placement could be an issue... and I never liked the center speaker anyway, it sounds.. well, like a speaker rather than natural sound... I've never bothered with it myself... all your steering affects come from the left, right, and surround channels anyway.) let me tell you what it can do... 

- Raises sound stage

- Helps minimize rainbow effect.

- Adds ambiance

- Widens stereo image... my speakers are in the kicks... my right channel sounds seem to come from the side mirrors, sometimes from outside the window!

- Lowers distortion... the rears carry less information and so inherently have less distortion.

- Gives you a 3-dimensional sound field.

- Not only does it not hurt the front stage, IT ENHANCES IT.

I propose we do a few things:

Make lists of different ways to add surround to vehicles, and different products that can be used, and reviews of these techniques and products... there is very little information or product available, I've been virtually alone on this for twenty years... I'm old now and tired of doing all the legwork, LOL! Need some of you young guns to pick up the ball. I look forward to more discussion.


----------



## Abmolech

Good to see a post of this nature,

Welcome Gary S.

The future is with car computers and this style of format.
http://forum.doom9.org/forumdisplay.php?f=11

May give you anything you need.

I have been pushing the use of rear channels to increase acoustic crosstalk (for stereo) for years. And as you surmise, the resultant increase in width and depth.
It is nice to have a fellow journeyman.

The problem with prologic and logic7 is their dominate matrix for large rooms, you may be following JBL frustration with converting logic7 to be more useful in a car. (MS8)
I believe that site may offer away around them, and allow a format which is trying to deal with the space of a car.

If your adventurous, you may wish to try ambiophonics, and possibly quadraphonics as a viable alternative to stereo in a car. (Also on that site, may I recommend the B format for starters)

If you really want to keep the surround setup, ambisonics (also on that site) will give you a major step towards realistic sound production in a car.
IE you need to change nothing or very little to try it.

All these alternatives will give much better service in a car than stereo.


----------



## Oliver

Ge0 said:


> Same bat time, same bat channel.
> 
> I've changed things up a little since I last posted. The speaker bridging trick was working. However, it was limiting me. I could not adjust attenuation, EQ, time alignment PER rear fill channel. To obtain ultimate control I needed to break the link.
> 
> So, I decided to feed the amp with L-R signals at the input per the advice winslow offered werewolf on ECA nearly a year ago.
> 
> Here is how I acheived this. It only applies to people who have balanced inputs on their amp at this time.
> 
> Well, how do I like this? To tell you the truth, right now it is not much different. I haven't had much of a chance to sit down and tweak it. However, when I get time to play be damn sure I'll post my results.


Wow! This is great !
Thanx Geo !
Waking up right now, all I can say is: i love it, can't wait to see how you align this and create a certain Immersion in the music  

I'm sure that the OP is tickled with the way you fleshed this out !


----------



## matdotcom2000

So Ge0 hooking it up from the amp did not allow you to tell the difference between left and right? BTW has anuone figured out rearfill on the H701????


----------



## Gary S

Abmolech, thank you for the welcome and the info. Can you give me a link to the site you are talking about?


----------



## Oliver

Hey Gary is this interesting to you ?
http://www.diymobileaudio.com/forum/showthread.php?t=26627


----------



## Abmolech

http://forum.doom9.org/forumdisplay.php?f=11


----------



## Gary S

Hic said:


> Hey Gary is this interesting to you ?
> http://www.diymobileaudio.com/forum/showthread.php?t=26627


 - Thank you for the link, Hic. Correct me if I am wrong, but Ambiophonics looks like an interaural crosstalk cancellation system utilizing a conventional stereo pair of speakers. If this is the case, I think a rear surround channel (aka "difference", or L-R) will do the same thing (properly set up), do more, and do it better. I think Ambiophonics would be good in situations/systems where you do not have the option of adding rear speakers and are limited to two speakers.

There are so many incarnations of multi-channel sound it's mind bogling... so many manufacturer's want to try and make a little black box or a computer program to sell, and be able to claim it's proprietary, that you can only get it from them (supposedly). 

I'm betting it's the same as SRS WOW, a processor built-in to some Panasonic head units, and at least one Kenwood head unit.

You can also do that acousticly... simply flank your left and right speakers with additional, identical speakers carrying the difference signal!


----------



## Oliver

Durwood is looking for people to test his ideas !

That thread was started by him and I believe he still has some openings for test subjects.


----------



## Gary S

Abmolech said:


> http://forum.doom9.org/forumdisplay.php?f=11


 - Thank you for the link.


----------



## durwood

Gary S said:


> - Thank you for the link, Hic. Correct me if I am wrong, but Ambiophonics looks like an interaural crosstalk cancellation system utilizing a conventional stereo pair of speakers. If this is the case, I think a rear surround channel (aka "difference", or L-R) will do the same thing (properly set up), do more, and do it better. I think Ambiophonics would be good in situations/systems where you do not have the option of adding rear speakers and are limited to two speakers.
> 
> There are so many incarnations of multi-channel sound it's mind bogling... so many manufacturer's want to try and make a little black box or a computer program to sell, and be able to claim it's proprietary, that you can only get it from them (supposedly).
> 
> I'm betting it's the same as SRS WOW, a processor built-in to some Panasonic head units, and at least one Kenwood head unit.
> 
> You can also do that acousticly... simply flank your left and right speakers with additional, identical speakers carrying the difference signal!


Not quite but it carries some same similarities. Ambiophonics can work with just two speakers, but if you add more ambient speakers you can really imerse yourself in the music. I have not tested that nor will I for a long, long time.

Actually the guy behind ambiophonics is non-profit and pretty much offers everything for free. It's an interesting subject. You really don't need ot buy a fancy black box, just a computer. If you want a stand alone unit, TacT allows you to use what Ralph has put together. If you want to experience it, feel free to email me. I'm doing this out of pocket so it won't cost you a dime. It's not my ideas, it's Ralph's Ideas.


----------



## Abmolech

Depending on the vehicle, ambiophonics is a better option than stereo.
Quadraphonics is better than surround sound, again depending on the vehicle.

Still surround sound is a MAJOR step over stereo,because it seeks to deal with the space.

The site I posted allows you to try, and use ALL the above mediums for free.
Give it a go in your house first.
The VNC (voice in centre) for 5.1 is a major improvement over prologic and logic7, I suggest it is worth your time trying it.
If your adventurous, ambisonics over a surround system (again free) will give another major increase in sound realism.


----------



## Ge0

matdotcom2000 said:


> So Ge0 hooking it up from the amp did not allow you to tell the difference between left and right? BTW has anuone figured out rearfill on the H701????


Hooking it up from the amp (brigded channel) did not allow me to adjust EQ, TA, and gain independant of each other. Doing so would collapse the affect. Creating the signal (L-R) at the amps input gives me many more options. Yet to be explored mind you... Stuck in Southern Mexico now on business. 1000's of miles from my vehicle. No time to tinker with it until I return in a week.

Ge0


----------



## jrhavoc

Here is something that I found recently that is interesting and has some relevance to this (I think). I definitely like the use of analog circuitry to accomplish the delay and such. Gives me ideas...

http://www.niell.org/analog/Analog.html


----------



## Ge0

jrhavoc said:


> Here is something that I found recently that is interesting and has some relevance to this (I think). I definitely like the use of analog circuitry to accomplish the delay and such. Gives me ideas...
> 
> http://www.niell.org/analog/Analog.html


I read through that article years ago. I did not pursue it for a few reasons I can't quite remember. Perhaps the use of an ALL-PASS filter screwing up phase? I love the electromechanical delay solution. Too bad its bandwidth would suck and would be subject to road vibrations.

Ge0


----------



## GlasSman

Ge0 said:


> I read through that article years ago. I did not pursue it for a few reasons I can't quite remember. Perhaps the use of an ALL-PASS filter screwing up phase? I love the electromechanical delay solution. Too bad its bandwidth would suck and would be subject to road vibrations.
> 
> Ge0


Maybe it was the reverb box that killed it.:blush: 

That was enough for me to click right out of that page.


----------



## jrhavoc

You mean you don't like that idea? I was thinking of running some of the big slinkys across the rear deck of the deck... 

In seriousness though, there are some good ideas there. Like I said - some. On the delay though - isn't there a way to make a delay using passive components with an op-amp? I guess this would be for the most part just re-inventing the wheel but it would be slick to have a unit that you could input your source, do an analog time delay to the signals, and then send them out in balanced pairs how you wanted so you could get the rear in the manner that was suggested in this thread. Use some type of rotary encoder or something that would allow you to select which pair you wanted for that channel, whether they be L+/L-, R+/R-, L+/R+, or whatever combination desired.


----------



## Ge0

Progress is going very well on my L-R rear fill experiment. After dialing in the proper amount of attenuation and bandlimiting I now am rewarded with a pretty impressive ambient affect that very noticably increases the size of the sound stage.

If you have the means, or the ambition, to try this then I highly encourage it. It's the best you can do short of adding a PC to your car system that will create these effects via a number potentially superior software based options.

Durwood reminded me of something in another thread:



durwood said:


> For the record,
> 
> most people could try a rear-fill for almost free-no need for fancy processors. I recommended the halfer circuit in GEO's thread on L-R rear-fill.
> 
> all you need is a pair of rear speakers (hell your stocks might even work) and a headunit with built in amp (non-brideagble). Wire your rears in series and only connect the the series speaker to the positive terminals of the headunit's rear channels. You won't have delay, but you at least have fader to attenuate. If you don't like it then at least you tired it.


It is possible to derive L-R using a set of a modern head unit's amplified outputs. Only Durwood had an oversite. You NEED bridged outputs!!! You see, the amplifier outputs of a head unit do not reference ground. They are bridged internally to provide more power to your speakers. Instead of a positive feed and a ground per channel, you get a positive feed and the opposite feed which is 180 degrees out of phase (or a bridged channel). Tie your rear speakers in series then wire them across left channel + and right channel +. That's all you need to get L-R.

However, to get the full affect you'll also need some delay. Otherwise you won't get the same affect. The soundstage won't seem as deep. You CAN tinker with attenuating the rear output and setting crossovers fairly low (limit rear output to approx 3KHz) without delay and start to gain the affect. But, in order to get the sense that you are in a much larger room you'll need delay. Many modern aftermarket head units offer this. So, take a few hours and give it a shot.

P.S. The same thing can be done if you have a spare 4 channel amp you can hook up to the rears only. The amp must be bridgable WITHOUT needing to use a switch to bridge. If you have an amp that you need to flip a switch to bridge then you only need 2 channels. See my comments in an earlier post in this thread regarding the 2 channel amplifier solution. Basically, the same principle applies as with the head unit.

If you are confused about what to do then post to this thread. I'll watch it and attempt to help where I can.

Ge0


----------



## Gary S

Ge0 said:


> It is possible to derive L-R using a set of a modern head unit's amplified outputs. Only Durwood had an oversite. You NEED bridged outputs!!! You see, the amplifier outputs of a head unit do not reference ground. They are bridged internally to provide more power to your speakers. Instead of a positive feed and a ground per channel, you get a positive feed and the opposite feed which is 180 degrees out of phase (or a bridged channel). Tie your rear speakers in series then wire them across left channel + and right channel +. That's all you need to get L-R.


 - That's exactly right... I believe it is also called a BTL amp.

Or, you need an amp WITHOUT a tri-way phase inverter in one of the channels for this Hafler hook-up, aka rear surround channel(s).

I've been using old Soundstream Reference amps in my own systems for years... the reference amps and a handful of others had what they called "coherent stereo"... it was simply a switch to turn the phase inverter on or off... in "stereo" position, the phase inverter is bypassed... in the mono position, the phase inverter would be engaged so you could bridge the amp (summed) mono. However, these amplifiers have not been made for years, and the few that I like that come across ebay from time to time are ridiculously expensive compared to modern amps. Right now, I'm looking at some new amps... some of the sony amps claim to be 4/3 channel only... the front channels are not bridgeable... because they don't have a phase inverter in one channel. See the manuals on these amps for more.

I'm going to try one... if it works, and if it's not enough power for me, I'll get two and vertically biamp, using one pair of channels for each satellite.

If that does not work, there are at least 5 different head units available right now with SRS circle surround ll (cs auto NOT SRS WOW)... 4 Panys and a new Eclipse... but like you, I would rather do it with the amp... that way, I am free to pick and choose from any head unit. Plus, it just makes more sense to me... I mean, we bridge amps "summed mono" all the time... that's a summed, 3rd, matrixed channel, if you will... doesn't it make sense to derive the difference signal from the amplifier also?


----------



## Analog_123

OK, I'm a bit confused by this, but also had an idea.

My HU is a dead head, so no joy there with either balanced outs or amplified outputs.

Here's an idea tho. On ebay or equivalent there are always people selling off cheesy little amps (like 2 x 10 W) that came OEM with their car. These are also very very small. Now, they are probably not bridgeable so in theory you could get the sacred L-R signal from the output of the amp (input fed by appropriately manipulated signal from processor), and then put the (probably attenuated) output from the amp into the amp you are driving your rears with.

Would this work? 

Now, if only i could find a way of getting a cheap delay that didn't involve tying up two of the delay channels on my processor. Sigh.


----------



## Oliver

I don't see why not, give it a try


----------



## matdotcom2000

Ok does anyone know about pro logic II on the h701 and what the surround left/right outputs would be??? Also could someone put up a diagram of the speaker outputs that you all are doing on the amps to get the L - R just want to make sure I am doing it right....


----------



## Ge0

Analog_123 said:


> OK, I'm a bit confused by this, but also had an idea.
> 
> My HU is a dead head, so no joy there with either balanced outs or amplified outputs.
> 
> Here's an idea tho. On ebay or equivalent there are always people selling off cheesy little amps (like 2 x 10 W) that came OEM with their car. These are also very very small. Now, they are probably not bridgeable so in theory you could get the sacred L-R signal from the output of the amp (input fed by appropriately manipulated signal from processor), and then put the (probably attenuated) output from the amp into the amp you are driving your rears with.
> 
> Would this work?
> 
> Now, if only i could find a way of getting a cheap delay that didn't involve tying up two of the delay channels on my processor. Sigh.


You would need to insert a line out converter between the crappy little toy amp and the RCA inputs of the higher power amp you intend on driving the rear speakers with.

The line converter would not be necessary if the larger amp has balanced inputs or high level inputs.

Ge0


----------



## Ge0

matdotcom2000 said:


> Ok does anyone know about pro logic II on the h701 and what the surround left/right outputs would be??? Also could someone put up a diagram of the speaker outputs that you all are doing on the amps to get the L - R just want to make sure I am doing it right....


I believe Durwood posted a link showing how to wire a single speaker to obtain the hafler effect early on in this thread. How do you do this with a pair of speakers you ask?

Well, ever wire two subs in series to run off a single bridged channel? Identical to that!!!

Ge0


----------



## Gary S

I've never made a diagram on the computer, hopefully someone more skilled than I can help. But I can describe it:

1)Picture a 2-channel amp hooked up normally to two speakers in stereo... 

2) Now, take the negative speaker wires out of the amp and splice them together. 

3) What it will look like when you are done: a stereo amp with only positive speaker leads connected to it... the negative amp terminals have no speaker wires connected. The speakers' negative terminals are connected together by a jumper wire.


----------



## durwood

^^^That's pretty clear to me, excellent description. No need for a picture.


----------



## matdotcom2000

DAMN CLEAR thanks, I was hooking it up different from that I was hooking up a little different but basically the same way. 

BTW going to search on pro logic II


----------



## matdotcom2000

Ok I have reinstalled everything and done some tuning. All I have to say is WOW rearfill is excellent with music pro logic II and the rearfill T/A at 20 ms. I like it so I am gonna keep it but I may make some changes to the placement of my rear speakers


----------



## Oliver

matdotcom2000 said:


> Ok I have reinstalled everything and done some tuning. All I have to say is WOW rearfill is excellent with music pro logic II and the rearfill T/A at 20 ms. I like it so I am gonna keep it but I may make some changes to the placement of my rear speakers


sweet, that was the original poster's hope , that it would augment your set-up with some ambience [ read big awesome soundfield ]!


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## Ge0

Hic said:


> sweet, that was the original poster's hope , that it would augment your set-up with some ambience [ read big awesome soundfield ]!


I must admit, for the first time I can say I actually prefer listening to my system with rear fill vs without. It now sounds "better", not just "different". The soundstage gets noticably larger with L-R rear fill enabled. The stage sound bland without it.

You owe it to yourself to at least try this if you have the means. Chances are you can do it with what you have, or, with simple additions/modifications.

Ge0


----------



## Ge0

Well, did I inspire anyone else try try this?

What results did you obtain?

Ge0


----------



## Abaddon

Ge0 said:


> Well, did I inspire anyone else try try this?
> 
> What results did you obtain?
> 
> Ge0


I'm very interested in trying it, and I've been following this thread since the beginning (and the threads that inspired it that week)

I've just had no time to even THINK about trying it...


have you tried listening to it with JUST the L-R Fill enabled? What is it like?


----------



## Soundsaround

Ge0 said:


> Well, did I inspire anyone else try try this?
> Ge0


Soon... very soon.


Abaddon said:


> have you tried listening to it with JUST the L-R Fill enabled? What is it like?


I rigged it up on my desk system here at home. Very cool, lotsa reverb and ambiance effects, almost "ghostly" sounding. Practically no drums or lead vocals on some recordings. You can easily tell that it'll make for a very 3D stage.


----------



## Ge0

Abaddon said:


> I'm very interested in trying it, and I've been following this thread since the beginning (and the threads that inspired it that week)
> 
> I've just had no time to even THINK about trying it...
> 
> 
> have you tried listening to it with JUST the L-R Fill enabled? What is it like?


You mean without time delay? I may have temporarily but did not pay much attention. I'll try it tonight or tomorrow and let you know.

Ge0


----------



## Abaddon

Ge0 said:


> You mean without time delay? I may have temporarily but did not pay much attention. I'll try it tonight or tomorrow and let you know.
> 
> Ge0


Well, i mean without your front stage running.

Soundsaround gave me the answer I was expecting though..


----------



## Ge0

Abaddon said:


> Well, i mean without your front stage running.
> 
> Soundsaround gave me the answer I was expecting though..


Yes, I have definitely tried this. It removes all L+R center channel information. Sounds real wierd. All that is left over is information only intended for hard right and hard left.

Even freakier, fade the fronts back in and then balance the whole system left or right. Now, listen to a recorded voice. You hear a noticable echo. BUT, when balance is set to center, you don't. Your soundstage just sounds much larger.

Ge0


----------



## blackwolf

Geo, yes you did inspire someone to try this. I'm new to the forum and am admittedly WAY behind you and a lot of other members here in knowledge, experience and quality of equipment. Nevertheless, this idea worked in my vehicle. 

I have a '84 Porsche 944 running a hodge podge of old and new pieces. An 8 yr. old Kenwood HU, an Alpine 7-band graphic EQ that I have no clue how old it is (donated by a friend), a 15 yr. old Pioneer component set mounted in custom door pods, relatively new Pioneer 4x6's in the stock rear quarter locations and new RF 8" subs in a custom enclosure. The comps and the rear fill speakers are run off the EQ and the subs are fed their signal from the HU via their own RF 300-1 amp.

Obviously, I have no TA or additional processing other than the EQ, so the result is not what you would call awe-inspiring. But, it did make a significant difference in the overall height of the soundstage and maybe a small increase in width.

I'm just getting back into the things I enjoy in life and my system is crude to say the least at this point. But it's all I've got at this point until I can find my way clear to spend $$$$ on toys. Anyway, thanks to you for this thread and to a couple of the other posters for showing me how to improve what I've got for now.


----------



## Ge0

blackwolf said:


> Geo, yes you did inspire someone to try this. I'm new to the forum and am admittedly WAY behind you and a lot of other members here in knowledge, experience and quality of equipment. Nevertheless, this idea worked in my vehicle.
> 
> I have a '84 Porsche 944 running a hodge podge of old and new pieces. An 8 yr. old Kenwood HU, an Alpine 7-band graphic EQ that I have no clue how old it is (donated by a friend), a 15 yr. old Pioneer component set mounted in custom door pods, relatively new Pioneer 4x6's in the stock rear quarter locations and new RF 8" subs in a custom enclosure. The comps and the rear fill speakers are run off the EQ and the subs are fed their signal from the HU via their own RF 300-1 amp.
> 
> Obviously, I have no TA or additional processing other than the EQ, so the result is not what you would call awe-inspiring. But, it did make a significant difference in the overall height of the soundstage and maybe a small increase in width.
> 
> I'm just getting back into the things I enjoy in life and my system is crude to say the least at this point. But it's all I've got at this point until I can find my way clear to spend $$$$ on toys. Anyway, thanks to you for this thread and to a couple of the other posters for showing me how to improve what I've got for now.



Welcome to DIYMA blackwolf.

Don't fret about the age or grade of your equipment. It's a good start. Read through everything you can get your hands on in this forum and improve the environment (i.e. install) the equipment resides in. Once that is complete to the best of your ability the equipment may start to become a limiting factor. You can think about swapping it out at that time.

The great thing about DIYMA is that it proves you don't need to spend 6 months worth of mortgage payments to achieve good sound. Sure, exotic equipment that is new, nice, and shiney is always desireable. But, not absolutely necessary.

I was in the same boat as you early last spring when I joined DIYMA. I was just getting back into car audio and wanted opinions on doing a few simple things to my vehcile. Well, I caught the fever and am now in way over my head again!!!

Ge0


----------



## blackwolf

Thanks for the welcome, Ge0. And believe me when I say I've been doing LOTS of searching and reading on here. I've generated several text documents for quick reference and study by copying info on various topics from numerous threads and various install photos for that matter. Very time consuming on a dial-up connection, but it has been fun. 

Anyway, thanks again and keep up the great posts. I'll be eagerly watching.


----------



## Soundsaround

Hey Geo(or anyone else that tried this)-
What bandwidth did you settle on for the rears? I have a set of dome mids that I'm going to try, but I'm also placing a PE order and I'm thinking of picking up something cheap that'll cover a broader range.
When I tried this at home, I found that severely limiting the range to 800-1k still got the job done and made localizing the rears nearly impossible. Going much above 1k quickly drew the stage backwards for me, but what about sub 500hz? 
You think it's worth dropping $10 on something that'll get down to 100hz?
I wouldn't even have to build a baffle for these:http://www.partsexpress.com/pe/show...=1&&vReviewPage=5&vReviewRand=2460969#reviews


----------



## Oliver

werewolf said:


> if you have the processing power to add different delays for each of the two rear speakers, i would definitely try that. But a simple inversion ... or, 180 degree phase shift ... is stupid-easy to try.
> 
> So the answer is : this requires lots of experimentation to optimize. First you must create and process the L-R signal. You MUST experiment with proper attenaution, bandlimiting and delay. Guidelines can be offered ... bandlimit to somewhere between 3~7kHz, delay somewhere around 20 msec, attenuate so the effect is subtle, but noticeable. If you have a processor that can give different delays for each of the two rears, give that a try. If not, the simple 180 degree phase shift is easy to do, by simply inverting the leads to the other rear speaker (to be wired in parallel or series with the first rear speaker).


Does this help answer your question ?


----------



## Soundsaround

a$$hole said:


> Does this help answer your question ?


You mean this line?:


werewolf said:


> bandlimit *to* somewhere between 3~7kHz


I agree that you don't need to go very high, but I'm asking about the value of going lower than 500hz.


----------



## Oliver

Ge0 said:


> My initial impressions after modifying my system to perform L-R rear fill using the speaker output manipulation method (i.e. the Hafler Effect) I mentioned earlier today:
> 
> Wiring this up is a breeze. Simply tie the rear fill speakers in series and bridge them across two channels of the amp. Next, use your handy dandy signal proccessor to flip the phase of one channel by 180 degrees to overcome the inversion the amp already made.
> 
> Per others recommendations I then set crossovers to bandlimit the signal. The high pass is set to 100Hz at 24db/octave. The lowpass is set to 7KHz at 12db/octave (mMy rear fill plays full range through a mid and tweet combo. So, I don't necessarily need to worry about playing too high of frequencies with my mids). I don't believe there is an exact science on how to set the bandpass. But, I felt this was as good of a starting point as any. If someone wants to offer advice regarding the reason for setting specific crossover points in this application I would appreciate it.
> 
> I did not change any volume levels (front vs. rear) at this time.
> 
> Preliminary time delay of the bridged channel was set to 20mS. This will need some manipulation +/- a few milliseconds so I don't cross outside the bounds of the Haas Effect yet still obtain the maximum amount of delay.
> 
> What I found. When the gains are dialed in to perfectly match the cancellation of vocals is VERY pronounced. All you hear is a faint echo of vocals in the background. Yet, sounds from either side still retain their original volume level. However, stray a little bit from a perfect balance and the cancellation goes to ****. Same goes for setting time delay and crossovers. They must match as close as possible or the cancellation effect collapses.
> 
> At first my front stage level was set well above the rear fill (the same setup I used with conventional rear fill). I noticed no significant change. But, as I increased the level of the rear fill, the front soundstage seemed to open up and come alive. It no longer sounded as if it was sitting in front of me on top of my dashboard. It started to sense that I was in the room of the performance. BTW: I could obtain the same effect with delayed conventional rear fill, but read on... I adjusted the level of rear fill a little higher with respect to the front stage. The front stage started to get deeper!!! I could dial this in to where the vocals seemed to be off in the distance. However, there was a limit to how deep everything on either side (non centered info) could get. Adjust the level of the rear fill even higher yet with respect to the fronts and the stage soon dives backwards. So, there is a delicate balance between how deep you want to get and a total elimination of any benefits this may offer. This is something I could not do with conventional rear fill.
> 
> Ultimately, through level adjustments of the rear fill alone, I decided to place my front stage out just shy of the center of my hood. This was a good balance between the depth of vocals and the rest of the music going on. After all, what performer actually sings 20ft BEHIND the band?
> 
> As stated earlier, you get more than just added stage depth. You get ambience. I don't know how to explain it much more than music just seems more live, more real. Like I said earlier in this post, it sounds like you are sitting in the performance hall, not just listening to it through speakers in front of you.
> 
> This was my impression from my first few hours monkeying with L-R rear fill. I hope to do plenty of experimentation with this to squeeze all the performance I can out of it in the weeks to come.
> 
> To Sum things up, here is what you will need to try this experiment:
> 
> 1.) A bridged amp channel with rear fill speakers wired in series across the bridge.
> 
> 2.) The ability to electronically invert one channel to overcome the inherant inversion that occurs in an amplifier when channels are bridged. Does not apply to amps that are not bridgable or bridge through a switch. Leave the switch off!
> 
> 3.) The ability to bandpass the bridged channel with highpass and lowpass crossovers.
> 
> 4.) The ability to add time delay (ranging from 10 to 30 mS I presume) to the bridged channel.
> 
> 5.) The ability to control the gain of the bridged channel. This should be a no brainer using an amps sensitivity controls.
> 
> And that is all for now folks...
> 
> Ge0


soundsaround


----------



## Soundsaround

lol!
Your the undisputed king of the quotes my friend  
Only problem is that I had read that previously and it doesn't directly address my question. I know he later wound up dropping the lowpass... how about the highpass?
How important is lower midrange in this scenario?


----------



## Ge0

Soundsaround said:


> lol!
> Your the undisputed king of the quotes my friend
> Only problem is that I had read that previously and it doesn't directly address my question. I know he later wound up dropping the lowpass... how about the highpass?
> How important is lower midrange in this scenario?


Sorry I did not chime in sooner. Totally missed updates to this thread.

Highpass is now set to 80HZ rolled off at 24dB/octave. This is the limit of what my rear speakers are capable of without distorting something fierce. Midbass frequencies are non-directional. The rears help support the fronts in this range. Plus, you'll want to cover the lower midrange. These frequencies are largely present in real room reflections. Lowpass is now set to 3.5KHz at 12dB/octave. I had no real reason for lowering this point beyond a few things that I have read. If you want to more accurately model room reflections at a reasonable distance you'll need to attenuate higher frequencies as they would roll off naturally. This was my first stab at it. Thusfar I have left it. 

Answer your questions?

Ge0


----------



## LastResort

3.5kHz? That gives me hopes of running this with just a 5.25 midbass driver. Now, if I can only find a way dialing in some delay via discrete components.......or perhaps find a head unit with some TA.....


----------



## Soundsaround

Interesting Ge0, you actually lowered your highpass. I'll pick up something with a broader range than my dome mids....thanks.


----------



## CobraVin

i really want to try this, i have read all the links and understand the concept, although im a little confused on how to wire going into my amp, im using a zapco dc350.2 on my rear speakers, its a tundra 4 door and they(8inch quarts)are in the rear doors, 7 inch scan revs in the front doors

can anyone tell me how to cut the symbilink cable and rewire it,i dont even know what wires are in the cable, i just dont want to damage my amp or head unit, i think the dc is a good amp for this because of the dsp, i will play around with the delays and levels and bandwidths, i just want to get the signal going in to be right, diagram would be great, thanks in advance


----------



## Ge0

CobraVin said:


> i really want to try this, i have read all the links and understand the concept, although im a little confused on how to wire going into my amp, im using a zapco dc350.2 on my rear speakers, its a tundra 4 door and they(8inch quarts)are in the rear doors, 7 inch scan revs in the front doors
> 
> can anyone tell me how to cut the symbilink cable and rewire it,i dont even know what wires are in the cable, i just dont want to damage my amp or head unit, i think the dc is a good amp for this because of the dsp, i will play around with the delays and levels and bandwidths, i just want to get the signal going in to be right, diagram would be great, thanks in advance


Go into the user manual for your DC350.2 and get the pinout for the Symbilink connectors.

Start not with a $40+ Symbilink cable. Start with a $3.00 PS-2 extension cable (got it on sale)









Here is my confusing drawing of how to wire this








Input is the side that connects to your Symbilink cable. Output is the side that plugs into the amp. On the input side leave L- and R- open circuit. They do not solder to anything. Route L+ from the input side to R- on the output side. Route R+ from the input side to L- on the output side. Ground from input side should solder to ground on the output side. If your PS-2 cable has an internal shield connect the shield from the input side to the shield from the output side.

Wrap it up nice and you are done. Here are a few pictures of mine.

Cut in half, and strip back insulation to expose an inch or so of each individual wire. Solder wires to a protoboard kind of like this.


















I added strain relief and encapsulated my wiring so it would not come undone if you tugged on it by accident. I then sealed it off using glue impregnated heat shrink tubing to protect it from the environment.













































Here the cable is installed.









Hope this helps. Ask questions if need be.

Ge0


----------



## CobraVin

wow thats great, im on my way to work and i havnt studied the post real well yet but is the circuit board needed?, couldnt you just twist and solder the wires directly

also i am using a ps/2 cable on the dc anyway, but i will still probably pick up the extention, just so i dont have to rerun the cable in case i screw it up, my 2 real symbilink cables are on my c2k's 

thanks again the pics were exactly what i need, its like L-R rear fill for dummies, cant wait to try it

Vinny


----------



## Ge0

CobraVin said:


> wow thats great, im on my way to work and i havnt studied the post real well yet but is the circuit board needed?, couldnt you just twist and solder the wires directly
> 
> also i am using a ps/2 cable on the dc anyway, but i will still probably pick up the extention, just so i dont have to rerun the cable in case i screw it up, my 2 real symbilink cables are on my c2k's
> 
> thanks again the pics were exactly what i need, its like L-R rear fill for dummies, cant wait to try it
> 
> Vinny


No, you do not need to use a circuit board substrate. This is just the way I chose how to do it. I thought that isolating splices in those tiny wires might get tricky (i.e. individually heat shrinking solder connections).

Ge0


----------



## mitchyz250f

Geo:
1) Do you really need an amp as powerful as the one running the front stage? Seems like there is a LOT less information coming from the rears in this set up as compared to the fronts.

Gary S. wrote;
1) Picture a 2-channel amp hooked up normally to two speakers in stereo... 

2) now, take the negative speaker wires out of the amp and splice them together. 

3) What it will look like when you are done: a stereo amp with only positive speaker leads connected to it... the negative amp terminals have no speaker wires connected. The speakers' negative terminals are connected together by a jumper wire.



I have a Soundstream Ref amp. Would the switch be on mono or standard mode in the descirption above?


----------



## Ge0

mitchyz250f said:


> Geo:
> 1) Do you really need an amp as powerful as the one running the front stage? Seems like there is a LOT less information coming from the rears in this set up as compared to the fronts.
> 
> Gary S. wrote;
> 1) Picture a 2-channel amp hooked up normally to two speakers in stereo...
> 
> 2) now, take the negative speaker wires out of the amp and splice them together.
> 
> 3) What it will look like when you are done: a stereo amp with only positive speaker leads connected to it... the negative amp terminals have no speaker wires connected. The speakers' negative terminals are connected together by a jumper wire.
> 
> I have a Soundstream Ref amp. Would the switch be on mono or standard mode in the descirption above?


No, the rear fill amp does not have to be as powerful as what is running the front stage. In my experience, you want the rears to be about 6dB down from the fronts. That's about 1/4 the power required for the fronts given all speaker sensitivities are the same. 

You'll want to keep that reference amp in normal stereo mode.

Ge0


----------



## Whiterabbit

I suspect the gain will depend on the T/A. We can easily add more T/A to simulate larger and larger spaces, but we have to compensate by using a different passband as certain frequencies travel better than others, and the good old inverse square law suggests gain will require reduction as well.

Or increasing, if we are trying to simulate a smaller and smaller room.

I believe we need four times the power to double excursion, by the way


----------



## Whiterabbit

Geo, is your stage a 2 driver or 3 driver stage?


----------



## Ge0

Whiterabbit said:


> Geo, is your stage a 2 driver or 3 driver stage?


Front stage is 2 driver for now. Soon to tinker with 3 way. Just waiting for shipments to come in and the weather to warm up a little.

Ge0


----------



## Whiterabbit

let me know when you have that set up, rearfill and all. I want to compare a few notes with you that will not couple at all unless your stage uses a dedicated midrange.


----------



## CobraVin

whiterabbit can you expound a little on what you mean as i was thinking about adding a mid to my 2 way as well, but unless i get more amp channels mine might be one or the other


----------



## mitchyz250f

bumb


----------



## Whiterabbit

IMO if it is one or the other, the 3-way stage with a dedicated midrange trumps the use of rearfill.


----------



## Fast1one

Whiterabbit said:


> IMO if it is one or the other, the 3-way stage with a dedicated midrange trumps the use of rearfill.


What about using BOTH? 

Just read through the majority of this thread, and it looks mighty intriguing...

Got a couple questions, I remember reading somewhere in the thread that using the same speakers would be beneficial. Basically what I want to do is use a 3 inch midrange in the rear, but I am not sure how I should mount it. 

Do you think it would work well fiberglassed in the rear pillars facing forward off axis? Perhaps firing towards the center of the dash...either way I have the speakers laying around, so i will probably box them and play with positioning, just curious on your input guys


----------



## mitchyz250f

Anyone use the simpler 'Gary S' method using non bridgeble amps, wireing one speaker our of phase?

Has anyone tried the rear off axis?

If not, any update on the would be appreicated.


----------



## Oliver

if your going for easy just buy a 500/5 by jl [ slash ].

It is all done for you!


----------



## blackwolf

mitchyz250f said:


> Anyone use the simpler 'Gary S' method using non bridgeble amps, wireing one speaker our of phase?
> 
> Has anyone tried the rear off axis?
> 
> If not, any update on the would be appreicated.


mitchyz250f, I have. It is the only thing I can do with the rudimentary system I currently have. The result was that it raised my soundstage from just below my knees to just about the top of the dash. 

As I said, my system is simple by comparison to a lot of (or most of) the folks on here, but I tried it and it worked. It is definitely something I will explore once funds will allow me to upgrade things.

By the way, the rears are off-axis, firing straight across at each other from the stock factory locations, although they are not the factory speakers.


----------



## Ge0

Whiterabbit said:


> let me know when you have that set up, rearfill and all. I want to compare a few notes with you that will not couple at all unless your stage uses a dedicated midrange.


DONE. Now, what would you like to talk about?

Ge0


----------



## Whiterabbit

Aligning the rearfill crossover to the midrange crossover.

what crossover points are you using for the rearfill? what crossover points are you using for the midrange?

And what happens if you change the slopes and cutoffs of the rears to match?

I found doing this eliminated the majority of any speakercentric problems that popped up. No ill effects as of yet.

Since you now have the stage and fill set up and tuned, Im curious if you could do some critical listening for room effects only (no stage effects) plus deal-breaker effects like speaker localization etc, the environmental stuff that doesnt change with program material.

And evaluate the differences between the way you have it set now versus using identical crossover points.

Again, not referencing a stage effect, but a room effect, creating the sense of a larger listening space versus changes to system integration.

That's what I'd like to compare notes with.


----------



## mitchyz250f

Blackwolf - Did you reverse the polarity of one of the speakers as Gary suggested?

Whiterabbit - I think you are saying that you have the rears crossed over exactly the same as the front mids. Is ths correct? what does speaker centric mean?


----------



## Oliver

cen·tric [ séntrik ] or cen·tri·cal [ séntrik'l ] 


adjective 

Definition: 

1. at or as middle: located at or constituting the middle of something


----------



## Ge0

Whiterabbit said:


> Aligning the rearfill crossover to the midrange crossover.
> 
> what crossover points are you using for the rearfill? what crossover points are you using for the midrange?
> 
> And what happens if you change the slopes and cutoffs of the rears to match?
> 
> I found doing this eliminated the majority of any speakercentric problems that popped up. No ill effects as of yet.
> 
> Since you now have the stage and fill set up and tuned, Im curious if you could do some critical listening for room effects only (no stage effects) plus deal-breaker effects like speaker localization etc, the environmental stuff that doesnt change with program material.
> 
> And evaluate the differences between the way you have it set now versus using identical crossover points.
> 
> Again, not referencing a stage effect, but a room effect, creating the sense of a larger listening space versus changes to system integration.
> 
> That's what I'd like to compare notes with.


I threw some new midbasses in a few days ago and am trying to get them dialed in properly. I'll hop on this as soon as that is complete.

Right now rears crossed at 3KHz 12dB/octave lowpass. Front midranges crossed at 3KHz 24dB/octave lowpass. 

The crossover point for the rears was a "best guess" based on the natural attenuation of intensity as sound travels through longer distances. Time delay for the rear channels is set at 22mS

The crossover point for the front midranges was chosen on purpose. This is the point right before off-axis plots start to deviate from on-axis plots. 

So far I found that phasing of the rears with respect to each other, and, in comparison to the front stage has a larger impact on the ambient effect. But, will be more than happy to fool around with crossover slopes for the purpose of this experiment. 

Ge0


----------



## blackwolf

mitchyz250f said:


> *Blackwolf - Did you reverse the polarity of one of the speakers as Gary suggested?*
> 
> Whiterabbit - I think you are saying that you have the rears crossed over exactly the same as the front mids. Is ths correct? what does speaker centric mean?


I connected the negative leads of the rear speakers. The positive leads are connected as normal, in my case, at the Alpine EQ I'm running. I currently have no provisions in my system to perform time alignment, etc. So I did the only thing I could, but even this simple manuver helped (in my case).

If your system is more capable, great. If so, do some experimenting and _really_ pay attention to what Ge0 and Whiterabbit are doing. They seem to have this thing pretty well beat into submission.

Good luck.


----------



## mitchyz250f

a$$hole - I am still not getting it. I think the word he used was 'speakercentric' not contcentric.


----------



## Whiterabbit

phenominal geo, that is absolutely perfect. please let me know once the midbass are dialed in what effect steepening the slope does for ambience in your car.


----------



## Ge0

Whiterabbit said:


> phenominal geo, that is absolutely perfect. please let me know once the midbass are dialed in what effect steepening the slope does for ambience in your car.


OK, here we go. Jumped right on this since we both have similar interests.

I used Patricia Barbers Companion CD as an evaluation since this one was recorded live in a small venue. I think the mics were either placed in, or behind the crowd. Its very active with backgound ambience.

Sorry to say it, but I noted NO discernable difference between 12 or 24db per octave slopes. However, decreasing the slope to 6 dB/octave did seem to make a difference. It helped define and set the front stage ever-so-slightly.

The bigger change came when I switched the rear fill back to out of phase with each other, then out of phase with the front stage (if that makes sense). The stage lifted a good 3 inches and kept the excellent frontal soundfield with the same depth.

You know, I'm starting to loose track of what changes do what. I've swapped so many drivers in and out lately and have changed so much in my setup. This is probably close to what I had a few months ago with my stellar 2-way front stage. I lost a little of the L-R rear effect moving to a 3-way front stage and could never quite pinpoint it. Perhaps tonights experiment was it?

I wish i had more to offer you at this time, but, my head is still spinning trying to comprehend what just happened.

if you have a track or two you would like me to try to evaluate your findings please mention it. I'll give it a try.

Ge0


----------



## Candisa

As some may know, if I find nice oldskool stuff for a cheap price, I have hard times to resist the urge of buying it... Some stuff ends up in my car, other stuff ends up against a wall or in a closet untill I find something better to do with it...

Well, I bought a Kenwood KAC-821 amp this week and it has a 4ohm-2ohm-4ohmBridged switch on it. When I put that switch on 4ohm or 2ohm, I guess the amp will act as a non-bridgeable amp, right?

So here is the plan:
- Splitting up the midrange signal (250-3000Hz) to the frontstage midrange-amp and the Kenwood
- Mounting a couple of Visaton FR10's (I have them laying around, when the effect works out well I can replace them by the same mids I use in the front stage) in the back, aimed to the windshield

Now the questions:
- Am I right that I have to connect the positive connection of both speakers to the positive connections of the amplifier and connect the negative connections of the speakers to eachother?
- The amp has a switch on it for 4ohm-2ohm-bridged. I have to use one of the non-bridged positions to let it act as a non-bridgeable amp, when I use 4ohm drivers, I'll have to put it in the 4 ohm position (2 4 ohm speakers in series = 8 ohm, over 2 channels = 4 ohm per channel), but what if I use 8 ohm drivers? Since the amplifier gives the same wattage at 4ohm, 2ohm or bridged, I suppose the 4ohm position is 'high voltage' and the 2 ohm position is 'high current', so I need the 4ohm position to have maximum control over the 8ohm drivers, right?
- I don't use time-alignment on my front stage and I sure won't buy a dsp just to have time-alignment on the rearfill. I read you have to delay the rearfill about 20ms to have the best effect, will it work without the delay?
- The frontstage will be optimised for the drivers seat by left and right seperate equalizing, since the signal for the rearfills also go through the equalizer, won't I hear parts of the L+R signal at the frequencies that are differently equalized, causing a stage that jumps back at those frequencies?

greetz,
Isabelle


----------



## Oliver

Candisa,

The delay coupled with the summation of a left minus right signal which is then bandpassed is all needed to optimize the effect you are trying to achieve. [the various levels of control over bandwidth, arrival time and leaving a signal void of extraneous input , is what you are after].


----------



## Soundsaround

Candisa said:


> - I don't use time-alignment on my front stage and I sure won't buy a dsp just to have time-alignment on the rearfill. I read you have to delay the rearfill about 20ms to have the best effect, will it work without the delay?
> 
> greetz,
> Isabelle


I attempted this and it didn't work out due to equipment failure, namely my delay processor quit. I also had tried it on my home system with all the aspects working properly, and it was a huge difference. To truly achieve what this is capable of you _do need_ the delay.

If you're a fan of regular non delayed/ non l-r rear fill, then I guess it would at least be a step in the right direction. I sure didn't take it that way though... yuck!!!


----------



## Candisa

I really don't want 'normal' rearfill, I want concert sound, 1 stage, in front of me at the right height, right width and right positions of the artists.

I only want rearfill if it opens up my tiny little Clio and makes it sound like a concert hall. 

It seems I cannot achieve this without a delayed rear-fill and I surely won't spend hundreds of Euros/Dollars to make it possible. I just happened to have a non-bridgeable amp and remembered I saw this thread before.

It won't work without spending big money, so be it, I'll stick with frontstage+sub only 

Thanks for the replies!

greetz,
Isabelle


----------



## Ge0

Candisa said:


> I really don't want 'normal' rearfill, I want concert sound, 1 stage, in front of me at the right height, right width and right positions of the artists.
> 
> I only want rearfill if it opens up my tiny little Clio and makes it sound like a concert hall.
> 
> It seems I cannot achieve this without a delayed rear-fill and I surely won't spend hundreds of Euros/Dollars to make it possible. I just happened to have a non-bridgeable amp and remembered I saw this thread before.
> 
> It won't work without spending big money, so be it, I'll stick with frontstage+sub only
> 
> Thanks for the replies!
> 
> greetz,
> Isabelle


I read your earlier posts and most of your assumptions are correct. Just a word of advice. Treat the series speaker load combination across your rear fill amp as if they are wired normally. Two 4 ohm speakers wired in series across two channels will act as a single 4 ohm speaker wired across a single channel with respect to load impedance. Don't worry about 8 ohm drivers vs. 4 ohm. You need to attenuate the rears so much that the difference in impedance is nominal.

Now onto the delay. I find the delay adds to the room effect. There is no rule that I know of as far as how much delay needs to be added. You can add delay one of two ways. Either through physical distance or artifical time delay (via DSP). In my vehicle, my rear speakers are mounted in the door right behind me (about 1/2 meter). I need time delay to "move them back".

If your rears are mounted further back (like in a rear deck) then you may not need as much, or any, delay. Wire it in temporarily and try it out. If you have questions once this is done then just ask.

You MUST try this. It makes a front stage come alive and just feel bigger!!!

Ge0


----------



## Ge0

Candisa said:


> I really don't want 'normal' rearfill, I want concert sound, 1 stage, in front of me at the right height, right width and right positions of the artists.
> 
> I only want rearfill if it opens up my tiny little Clio and makes it sound like a concert hall.
> 
> It seems I cannot achieve this without a delayed rear-fill and I surely won't spend hundreds of Euros/Dollars to make it possible. I just happened to have a non-bridgeable amp and remembered I saw this thread before.
> 
> It won't work without spending big money, so be it, I'll stick with frontstage+sub only
> 
> Thanks for the replies!
> 
> greetz,
> Isabelle


I forgot to add. To me, the real trick behind this form of rear fill is that L-R cancels the vocals out of rear fill and just plays stuff hard right and left. It enhances your front stage regardless of delay. Adding delay simply enlarges the envorinment.

Ge0


----------



## Whiterabbit

the delay and L-R "intelligent" processing is absolutely critical. Cutting out the vocals is a good way to enhance low level midrange without letting the "meat" of the recording overblow it.

The 15-30 second delay is to prevent phase anomalies from screwing with the sound. It's actually 180 degrees out of phase at 33 Hz but we arent playing down that low.

But up high it is so far delayed, so many wavelengths out of whack that it doesn't correlate with the initial waveform., yet not SO delayed it sounds like a second point source of sound. It is between, and the mind interprets this as an echo.

with the crossovers set "right" the sound reinforces the echo effect.

In theory I think the band limiting changes based on room size, as will the level of delay. Thus, in theory with one level of band limiting with short delay we simulate a large room, and changing the cutoffs to frequencies that carry farther and increasing the delay we simulate a cathedral.

That is the theory as I understand it, anyways.


----------



## Whiterabbit

without delay the reafill will simply create endless phase anomalies with the stage, drawing everything rearward.


----------



## ~thematt~

Whiterabbit said:


> ......The 15-30 second delay....


I'm assuming thats a typo  ....


----------



## mitchyz250f

Geo: A little confused with this statement. Can you explain further?

'The bigger change came when I switched the rear fill back to out of phase with each other, then out of phase with the front stage (if that makes sense).'

If the rears were flipped out of phase with each other, than one was in phase (lets say the right rear fill) and one was out of phase (lets say the left rear fill). Then, when you flipped them out of phase with the fronts then the right rear fill would be out and the left in. Please help.

If the rear fills are place as far back as possible in a hatch, do you think time delay is still required?


----------



## Ge0

mitchyz250f said:


> Geo: A little confused with this statement. Can you explain further?
> 
> 'The bigger change came when I switched the rear fill back to out of phase with each other, then out of phase with the front stage (if that makes sense).'
> 
> If the rears were flipped out of phase with each other, than one was in phase (lets say the right rear fill) and one was out of phase (lets say the left rear fill). Then, when you flipped them out of phase with the fronts then the right rear fill would be out and the left in. Please help.
> 
> If the rear fills are place as far back as possible in a hatch, do you think time delay is still required?


I knew this would be confusing. Imagine the rears are in perfect acoustical phase with the front stage. Now, flip the phase on both rears 180 degrees. Finally, flip the phase on the passengers side only 180 degrees again.

This worked in my vehicle given its speaker placements and geometry. Things could be totally different in your vehicle. I highly encourage you to play with phasing of the rears on your own.

As far as the delay. I recommend a minimum of 15ms to obtain a desireable effect. Somewhere between 20 and 25ms is optimal. Each 1ms of delay is equivalent to 1 ft. Lets assume your rear speakers are 5ft behind you. Thats only 4.5ms of delay. You can try it but I don't think you'll experience what this method can really do.

Ge0


----------



## Oliver

just like the 2006 [IASCA]champion , MicWallace , time delaying his sub 

Most people decide first what they think will work [then everything else won't work ], if you doubt me, ask them


----------



## Candisa

Thanks for the answers!

I drive a Renault Clio 3-doors hatchback. Even with the speakers physically pushed back as far as possible, there is no way I could get even close to 20-25ms delay compared to the frontset.

It won't work, so be it, maybe in a next project 

greetz,
Isabelle


----------



## ~thematt~

Is anyone aware of an outboard T/A device for one or two channels? Such that I can connect some RCAs too in order to give me that T/A??

I have all the channels of the Processor going to the front stage and the sub, but the ability to connect another amp to the outputs from the amps (my ArcSE's have output channels) and tap into a midrange signal. From there I can wire up the Hafler circuit, but the delay will be a problem.....


----------



## Candisa

That's exactly my problem. I don't even use TA on my frontset, I'm trying to get a good result by experimenting with positions, angling, phases, crossover points and L/R seperate EQ'ing, so I won't buy an expensive dsp just so I can delay the rear fill speakers.

I'm afraid something simple and cheap that just delay's one pair of signals doesn't exist...

greetz,
Isabelle


----------



## Oliver

werewolf said:


> no frikn way !!!
> 
> i mean ... rear fill sux ass !!!
> 
> .... ummm, doesn't it ??? that's what all the car audio experts say
> 
> hee hee, sorry i couldn't resist


Hehe


----------



## ~thematt~

Candisa said:


> I'm afraid something simple and cheap that just delay's one pair of signals doesn't exist...


Thats what I'm afraid of..... The 360.1 does it, and seems to be the cheapest I can find, but its still a bit pricey. I have the DEQ-P90 on my front stage, but all 8 channels are gone 

Seems like I have to daisy chain the midranges, and then delay the rear outputs to get this to work. Thats step 1. Step 2 is ditching the P90 and just setting up a carputer.....


----------



## Candisa

Can't you combine 2 pairs of drivers that are physically positioned close to eachother to one pair of channels on the P90 and split them up with a seperate analog 2-way active crossover to make 1 pair of channels free for the rear-fills?

I'll be running a carputer, but I'll use only 1 stereo DAC (probably a Hippohifi Bloat) and do only eq and active crossing with a AudioControl EQX and 4XS, no TA, so that combining option can't work for me and buying another DAC or a second hand dsp just to delay the rearfills is a waste of money in my eyes...

greetz,
Isabelle


----------



## ~thematt~

I was seriously contemplating running the midbass in mono (done it before, and you really cant tell a difference if the crossover is low enough) and then just using the other midbass channel for the rear-fill.......

Only problem there is setting up the system is no longer as simple as it normally is with the P90 (its a pinch), and will require some major smarts not to totally balls the entire thing up!!!!

Hmm, if only someone like Audiocontrol made a simple T/A unit like they do Xovers and EQ.


----------



## Candisa

I'm affraid TA is only possible if you process the signal digitally, so that means it would need a A/D convertor, a processor and a D/A convertor. Also, that ADC en DAC has to be of very high quality to make it useable for more than only rear-fills. I guess the cost of such a unit would be so close to that of a multi-channel DSP it just isn't worth producing the damn thing...

greetz,
Isabelle


----------



## Ge0

Candisa said:


> I'm affraid TA is only possible if you process the signal digitally, so that means it would need a A/D convertor, a processor and a D/A convertor. Also, that ADC en DAC has to be of very high quality to make it useable for more than only rear-fills. I guess the cost of such a unit would be so close to that of a multi-channel DSP it just isn't worth producing the damn thing...
> 
> greetz,
> Isabelle


Just a thought for adding time delay on a budget. Find a used head unit that has T/A capabilities, an auxilary input, and powered speaker outputs. Tuck it away somewhere out of site and try this out.

You can get used head units pretty cheap. I haven't followed what is out there in a long time, but, know something MAY be available.

How about some of the older Alpine processors, like the ones that were available before the H700. You could probably snag one of those up dirt cheap.

Remember, you don't need the absolute in quality gear to derive the rear signal. It's being used for ambience. Also, the levels are set low. The bulk of what you hear is all up front.

Ge0


----------



## Candisa

I'll see if something useable shows up for a small price, most important for me is knowing that I can use that Kenwood for rear-fill, but signal delay is a must. I'll focus on the front set for now since I don't have stuff laying around to delay the signal and I'll see what I might find 

greetz,
Isabelle


----------



## danssoslow

I remember David Navone doing an article on time delaying rear fill in CA&E a long time ago. In his Thunderbird he was using a pro sound piece that you would see typically hooked up to a guitar, like a wah-wah peddle or something of that nature. It was most definitely analog. Maybe someone that is into pro sound can chime in here.


----------



## Candisa

Sounds interesting...


----------



## danssoslow

Something like this:
http://www.musiciansfriend.com/product/Ibanez-AD9-Analog-Delay-Effect-Pedal?sku=150345

I don't know how much you can cut the effect of the reverb in something like this; there might be units without reverb completely; but this is the idea.


----------



## Ge0

A good test for L-R rear fill:

A Perfect Circle - Magdelana of the Mer de Noms Album. About 2 minutes 50 seconds into the song they pan background guitars wide. A good L-R setup will produce an imensly wide soundstage.

I've been tinkering with the level of my rear fill in relation to front. Too much makes the soundstage start to wrap around me. Meaning, its wide and the center is deep. However, the left and right outer boundaries of the soundstage seem to encraoch along side you instead of in front of you. Also, the stage drops just a tad.

Too little and the massive soundfield collapses. You loose monster width and the stage appears lifeless and only in front of you again.

Add in the right balance and you get a wide soundstage who's cue's all exist in front of you but you sense abmiance from behind you. Makes you feel like you're in a much larger place than in the boundaries of your small vehicle.

Ge0


----------



## cheesehead

Ge0 said:


> A good test for L-R rear fill:
> 
> A Perfect Circle - Magdelana of the Mer de Noms Album. About 2 minutes 50 seconds into the song they pan background guitars wide. A good L-R setup will produce an imensly wide soundstage.
> 
> I've been tinkering with the level of my rear fill in relation to front. Too much makes the soundstage start to wrap around me. Meaning, its wide and the center is deep. However, the left and right outer boundaries of the soundstage seem to encraoch along side you instead of in front of you. Also, the stage drops just a tad.
> 
> Too little and the massive soundfield collapses. You loose monster width and the stage appears lifeless and only in front of you again.
> 
> Add in the right balance and you get a wide soundstage who's cue's all exist in front of you but you sense abmiance from behind you. Makes you feel like you're in a much larger place than in the boundaries of your small vehicle.
> 
> Ge0


Thanks for the updates!

I have been reading through this entire thread along with some others pertaining to rear fill. I think I am going to give this a try when I install my equipment into my new daily driver!


----------



## mitchyz250f

Any updates?


----------



## psycle_1

danssoslow said:


> Something like this:
> http://www.musiciansfriend.com/product/Ibanez-AD9-Analog-Delay-Effect-Pedal?sku=150345
> 
> I don't know how much you can cut the effect of the reverb in something like this; there might be units without reverb completely; but this is the idea.


You'd be better off using a Boss DD-3 pedal. Set E. Level to max (100% mix), F. Back to min, Mode to S.50ms, and D. Time to whatever you want, probably near the middle.

It runs off a 9V battery, but should run off of 14V without any issues. Only trick would be to mod it to where it would turn on with the remote turn on lead. When you first apply power to the pedal, it defaults to bypass. The switcher AFAIK is a simple FET switching circuit. Should be fairly easy to tap into.


----------



## mitchyz250f

I posted this question on DIYADUIO, 'Is there a simple way to make a 15m/sec sound delay circut. this is for a car.'

It was suggested that the' simplest delay generator is the PT2399 - regrettably the shortest delay it can do is around 30ms. The NJU9702 does 0.5 to 32ms in 0.5ms steps, but you need a small micro to load the timing register (the littlest pic would do)....Googling will find you at least 2 vendors selling in onsies twosies. I bought some off Hongkong Inventory (a trading experience somewhat similar to Russian roulette but without the pleasant bits) but if I was doing what you are doing, I'd use 2 PT2399s, front set for 30ms and rear for 45ms. You'll never notice the 30ms absolute delay. PT2399s are available everywhere (Ebay etc) and are cheap as ch.... oh never mind. BTW a small pic is something like a PIC12F675.

Does this give anyone ideas, I don't really know enough about electricity to comment.


----------



## cheesehead

mitchyz250f said:


> I posted this question on DIYADUIO, 'Is there a simple way to make a 15m/sec sound delay circut. this is for a car.'
> 
> It was suggested that the' simplest delay generator is the PT2399 - regrettably the shortest delay it can do is around 30ms. The NJU9702 does 0.5 to 32ms in 0.5ms steps, but you need a small micro to load the timing register (the littlest pic would do)....Googling will find you at least 2 vendors selling in onsies twosies. I bought some off Hongkong Inventory (a trading experience somewhat similar to Russian roulette but without the pleasant bits) but if I was doing what you are doing, I'd use 2 PT2399s, front set for 30ms and rear for 45ms. You'll never notice the 30ms absolute delay. PT2399s are available everywhere (Ebay etc) and are cheap as ch.... oh never mind. BTW a small pic is something like a PIC12F675.
> 
> Does this give anyone ideas, I don't really know enough about electricity to comment.


Anyone have any thoughts on this?

Would the PT2399's work for rear fill time alignment?

If so it is a cheap alternative to having to buy a additional processor just to delay the rear fill! You can find the PT's for $3.95 here.

http://www.smallbearelec.com/Detail.bok?no=263


----------



## Ge0

cheesehead said:


> Anyone have any thoughts on this?
> 
> Would the PT2399's work for rear fill time alignment?
> 
> If so it is a cheap alternative to having to buy a additional processor just to delay the rear fill! You can find the PT's for $3.95 here.
> 
> http://www.smallbearelec.com/Detail.bok?no=263


At first glance these appear to be intended for cheap "trinket" types of applications. Distortion figures are rather mediocre as is noise and then dismal power supply rejection ratio. But, perhaps this is not the end all be all for this application. After all, this IS for ambient rear fill application right? It does not have to be as accurate as the front stage, or does it???

Now let's look at the inherent flaw in using this device for L-R rear fill. The idea is to take advantage of the precidence effect to create the illusion of being in a larger space. This requires a delay of no greater than 25 to 30 msec from front stage to back. Any larger delay and the rears will no longer blend in with the front, but rather signal from the rear will be heard as echo. You don't want that.

The minimum delay that can be percievably set on the PY2399 is about 31msec. Add a few milliseconds of delay due to the distance between your head and the rear speakers and you have entered echo territory.

Ge0


----------



## cheesehead

Ge0 said:


> At first glance these appear to be intended for cheap "trinket" types of applications. Distortion figures are rather mediocre as is noise and then dismal power supply rejection ratio. But, perhaps this is not the end all be all for this application. After all, this IS for ambient rear fill application right? It does not have to be as accurate as the front stage, or does it???
> 
> Now let's look at the inherent flaw in using this device for L-R rear fill. The idea is to take advantage of the precidence effect to create the illusion of being in a larger space. This requires a delay of no greater than 25 to 30 msec from front stage to back. Any larger delay and the rears will no longer blend in with the front, but rather signal from the rear will be heard as echo. You don't want that.
> 
> The minimum delay that can be percievably set on the PY2399 is about 31msec. Add a few milliseconds of delay due to the distance between your head and the rear speakers and you have entered echo territory.
> 
> Ge0


Thanks Ge0

It's too bad those do not fit the requirements. It would be nice to have something simple and cheap that we could wire in line to achieve the desired delay without spending extra cash on more processors.


----------



## Ge0

cheesehead said:


> Thanks Ge0
> 
> It's too bad those do not fit the requirements. It would be nice to have something simple and cheap that we could wire in line to achieve the desired delay without spending extra cash on more processors.


That depends, do you have time delay capabilities for your front stage? Could always add 10 to 15 milliseconds to everything up front. Then use this cheap little delay circuit to delay from 30msec+ on the rears. The overall delay front to rear would be 15 to 20 msec.

Ge0


----------



## cheesehead

Ge0 said:


> That depends, do you have time delay capabilities for your front stage? Could always add 10 to 15 milliseconds to everything up front. Then use this cheap little delay circuit to delay from 30msec+ on the rears. The overall delay front to rear would be 15 to 20 msec.
> 
> Ge0


Hmm! Yes I do have T/D capabilities for the fronts.

Do you think the spec.s on the delay circuits will cause any problems though?

I guess for the price it's probably worth experimenting with.


----------



## Candisa

Ge0 said:


> That depends, do you have time delay capabilities for your front stage? Could always add 10 to 15 milliseconds to everything up front. Then use this cheap little delay circuit to delay from 30msec+ on the rears. The overall delay front to rear would be 15 to 20 msec.
> 
> Ge0


I don't have time alignment at all in my setup, so this ain't possible for me. I do have a small car, so the rear-fills wouldn't be as far from me as in a sedan/estate and since I don't have a back seat, and rear passengers to care about, I can even mount the rear-fill drivers closer to me than the frontset, I could even do that in an assymetrical way so the path lengts of both rearfills are equal... 
A 30ms delayed L-R signal should simulate the reflections of a 9 meter long room... That is pretty good, but it isn't possible to 'trick' the human ear that much? 
Also, wouldn't the added distortion (including noise) pull the focus of the front stage to the back (the one thing you try to avoid by using a L-R signal on the rearfills), even if it is so much attinuated that it's barely hearable (not hearable as sound, but still hearable enough to change the ambience)?

greetz,
Isabelle


----------



## Ge0

cheesehead said:


> Do you think the spec.s on the delay circuits will cause any problems though?
> 
> I guess for the price it's probably worth experimenting with.


I do think the delay circuits stink for serious audio. However, like I said, this is for ambience affect only. Maybe they will work. By all means experiment. It's worth a shot.

Ge0


----------



## Ge0

Candisa said:


> I don't have time alignment at all in my setup, so this ain't possible for me. I do have a small car, so the rear-fills wouldn't be as far from me as in a sedan/estate and since I don't have a back seat, and rear passengers to care about, I can even mount the rear-fill drivers closer to me than the frontset, I could even do that in an assymetrical way so the path lengts of both rearfills are equal...


A sneaking suspicion tells me you would hear echo rather than ambiance. I don't want to say not to try it. But, I remain skeptical. Better solutions exist.



Candisa said:


> A 30ms delayed L-R signal should simulate the reflections of a 9 meter long room... That is pretty good, but it isn't possible to 'trick' the human ear that much?


You won't know yourself until you try. I can't quantify how big the environment sounds. But, it is defintiely a pleasureable experience. It really does expand the environment. Front stage without L-R rear fill seems lifeless.



Candisa said:


> Also, wouldn't the added distortion (including noise) pull the focus of the front stage to the back (the one thing you try to avoid by using a L-R signal on the rearfills), even if it is so much attinuated that it's barely hearable (not hearable as sound, but still hearable enough to change the ambience)?
> 
> greetz,
> Isabelle


My opinion no. The current solution I have installed does leave some artifacts. You rarely ever notice this. Then, it is only with certain songs. It does not drw the stage back. Rather, anomalies sound like they are in front of you!

Ge0


----------



## Hernan

Ok. I have a 3 way front plus sub, running from the 701. Only one output left: the center channel. To create the L minus right signal, I need two channels stereo.
I'm thinking on using the sub and center channels as a stereo sub channel, with Time delay and HP capabilities. The LP for the bandpass rear channel could be done by the amp XO.
The sub could play from a bypass rca output from the midbass channel (hipassing the midbass at the amp.

All I need is a pair of speakers wired in series with the left speaker positive to the left amp positive and the right speaker positive wired to the right amp positive.

Please, is something wrong with this approach?


----------



## Hernan

Second option: passive xo for the tweters...


----------



## cheesehead

Ge0 said:


> I threw some new midbasses in a few days ago and am trying to get them dialed in properly. I'll hop on this as soon as that is complete.
> 
> Right now rears crossed at 3KHz 12dB/octave lowpass. Front midranges crossed at 3KHz 24dB/octave lowpass.
> 
> The crossover point for the rears was a "best guess" based on the natural attenuation of intensity as sound travels through longer distances. Time delay for the rear channels is set at 22mS
> 
> The crossover point for the front midranges was chosen on purpose. This is the point right before off-axis plots start to deviate from on-axis plots.
> 
> So far I found that phasing of the rears with respect to each other, and, in comparison to the front stage has a larger impact on the ambient effect. But, will be more than happy to fool around with crossover slopes for the purpose of this experiment.
> 
> Ge0


Hey Ge0,

Are you still crossing over your rears and mids like mentioned?


----------



## Ge0

cheesehead said:


> Hey Ge0,
> 
> Are you still crossing over your rears and mids like mentioned?


Yep! Why do you ask?

Ge0


----------



## cheesehead

Ge0 said:


> Yep! Why do you ask?
> 
> Ge0


I am trying to figure out what frequencies are needed for rear fill.

http://www.diymobileaudio.com/forum/showthread.php?t=45432

http://www.diymobileaudio.com/forum/showthread.php?t=45432

:blush:

Here's the deal!

I've been reading about this rear fill for quite a while now. It has always peeked my interest but have never really pursued it due to vehicle and processing restraints. Well I changed vehicles and now have a Pontiac Bonneville SSEI. So I thought before I install my gear I would look into what it would take to do a delayed rear fill on the cheap. I started a thread a while back about cheap alternative processing that would be able to handle the requirements for the delayed rear fill. Here's the thread -

http://www.diymobileaudio.com/forum/showthread.php?t=45432

In the thread it was suggested that I look for a used head unit to handle the processing needs for the rears. I could just use the aux. outs from my main deck to the aux. ins of the secondary deck. Well I failed to do my homework and bought a Alpine 9833. I started looking at everything this last week. And I find out the 9833 is only capable of a 10.0 ms max delay. And the main deck I want to use is a Eclipse 8454. Which is only capable of 5.0ms of delay. And from what I have researched the most success has come from delaying the rears in the range of 15.0ms - 25.0 ms.

So the only way of producing 15.0 ms is to use either the front or rear outs of the Eclipse delayed 5.0 ms to the Alpine's aux. ins. Then I would be able to add an additional 10.0 ms a delay. But doing this I lose a channel of my main deck and lose the ability to control the volume of the rears.

Now this is what I'm considering. I have a pair peerless 3"ers that I could mount in the back deck. I would like to try and mount them in the stock 6x9 locations firing back into the corners of the deck. Then as suggested I would put some kind of shroud on the speaker grills to prevent any direct waves from going towards the front. The Bonneville has a pretty deep deck so I hope to gain enough delay to not confuse the front this way. I would run these of the 9833 delayed at 10.0 ms. This way I do not lose any outs on the front. I'm just afraid from what I have read that this will not be enough delay and will just confuse the front.

Any thoughts?


----------



## Oliver

Would be worth trying 

If you search you'll find out what has worked for others 

experimentation will show you what will work for you.

A 3" driver will limit the frequencies it is capable of playing [ perhaps not detrimental in this instance ].

Think BP , TD , and Left minus Right signal .


----------



## cheesehead

a$$hole said:


> Would be worth trying
> 
> If you search you'll find out what has worked for others
> 
> experimentation will show you what will work for you.
> 
> A 3" driver will limit the frequencies it is capable of playing [ perhaps not detrimental in this instance ].
> 
> Think BP , TD , and Left minus Right signal .


Well that's just the thing. I have searched and found the best results seem to be delayed 15.0 ms - 25.0 ms. I am hoping with the shroud, speaker selection and placement, and vehicle type I can over come the lack of 5.0 ms of delay. 

What could it hurt? Right!


----------



## CobraVin

couple questions

im in the middle of my install in my new car, i plan on using my dc350.2 for my l-r rear fill, im running a drz9255, highs, mids midbass and subs

should i split the mid signal and send it to the rear fill 250hz - 2500?, i had planned to use the slave output of my c2k mid amp to feed my rear fill, any problems with that?

also the stock rear speakers are only like a foot behind the head rests and they face each other, but once i put my subbox in there will only be a foot between the rear speaker grille and the box, think that would be ok or should i look to move the rear speakers, and if so where would be the ideal position?, far corners? facing which way?, i havnt built the box yet so im open to suggestions, its a 05 corvette (hatchback)

all opinions welcome, thanks in advance


----------



## Ge0

CobraVin said:


> couple questions
> 
> im in the middle of my install in my new car, i plan on using my dc350.2 for my l-r rear fill, im running a drz9255, highs, mids midbass and subs
> 
> should i split the mid signal and send it to the rear fill 250hz - 2500?, i had planned to use the slave output of my c2k mid amp to feed my rear fill, any problems with that?
> 
> also the stock rear speakers are only like a foot behind the head rests and they face each other, but once i put my subbox in there will only be a foot between the rear speaker grille and the box, think that would be ok or should i look to move the rear speakers, and if so where would be the ideal position?, far corners? facing which way?, i havnt built the box yet so im open to suggestions, its a 05 corvette (hatchback)
> 
> all opinions welcome, thanks in advance


I'm confused about what you are going to use for rear fill. A DC350.2 or the C2K? If using the DC then don't bother band limiting the signal. The DC will do that work for you. But, if that's the only signal you'll have available then what you suggested will work. If you decide to use the C2K then you'll need to band limit the signal using your head.

As far as you speaker spacing. Leave them in the stock location and try it out. I'm pretty confident it will work. Remember, you are delaying signal to them which is equivalent to moving them back.

Ge0


----------



## CobraVin

i have a c2k on each of my 3way front (c2k-highs, c2k-mids, c2k-midbass)and a bridged blau 4100 for my subs, so im out of channels from my head unit, so i was gonna use the through output of my mid amp since it would be receiving 250-2500 or 3000 from my head unit to feed the dc350 for the rears(rewired before going into the dc), and use the dsp in the dc for t/a
thanks, i cant wait to get this thing done, after dynamating i put a layer of mlv which is attached to closed cell foam through out the inside of the car as well as lining the inside of the wheel wells,doors, etc., all seams taped with lead tape, should be much quieter


----------



## CobraVin

quick question, im wiring up my cable now, i understand that L- and right - from the input side are snipped(not connected) as you (GEO)wrote under the picture on page 6

but are the L+ and R+ on the out put side also disconnected?, if not where do they go

im a little confused cause on page 1 white rabbit wrote this
(quote)
So to achieve the L-R signal, simply take whatever device recieves the Balenced transmission and converts it to standard. Rather than the standard method of wiring, *Wire L+ to the L+ input, but wire R+ where L- would go*. When the signals are internall subtracted, you end up with L+ - R+ = L-R

but on another page you (GEO)wrote.........
It helped me to draw this out. L- and R- coming out of the balanced line transmitters are left unterminated. *L+ is split and sent to the left and right + inputs on the amp. R+ is split and sent to the left and right - inputs on the amp*

im gonna read some old threads to remember which cancels out which but if anyone knows it will save me some time, thanks


----------



## CobraVin

oh well so much for the old werewolf threads, and eca is still down

anyone?

im using a male half of a symbilink cable(originally had rca's on the other end), and the male half of a ps2 extension cable, (male to male din) going from the through output of my c2k mid amp into my dc350 rear fill amp, in case anyone was wondering


----------



## cheesehead

CobraVin said:


> oh well so much for the old werewolf threads, and eca is still down
> 
> anyone?
> 
> im using a male half of a symbilink cable(originally had rca's on the other end), and the male half of a ps2 extension cable, (male to male din) going from the through output of my c2k mid amp into my dc350 rear fill amp, in case anyone was wondering


If I'm understanding the post. you are using the cables to wire the L-R? If so does your dc350 have T/A capabilities(NVM I see that it does...)?

And your thoughts on the rear fill?


----------



## CobraVin

CobraVin said:


> quick question, im wiring up my cable now, i understand that L- and right - from the input side are snipped(not connected) as you (GEO)wrote under the picture on page 6
> 
> but are the L+ and R+ on the out put side also disconnected?, if not where do they go
> 
> im a little confused cause on page 1 white rabbit wrote this
> (quote)
> So to achieve the L-R signal, simply take whatever device recieves the Balenced transmission and converts it to standard. Rather than the standard method of wiring, *Wire L+ to the L+ input, but wire R+ where L- would go*. When the signals are internall subtracted, you end up with L+ - R+ = L-R
> 
> but on another page you (GEO)wrote.........
> It helped me to draw this out. L- and R- coming out of the balanced line transmitters are left unterminated. *L+ is split and sent to the left and right + inputs on the amp. R+ is split and sent to the left and right - inputs on the amp*
> 
> im gonna read some old threads to remember which cancels out which but if anyone knows it will save me some time, thanks


figued id bump my question since its on the previous page, anyone?

cheesehead ill let you know when its hooked up, normal rear fill im not a fan of, but this seems pretty cool


----------



## CobraVin

hello, anyone want to take a shot at the question of how i wire this?, anyone?


----------



## CobraVin

is this thing on tap tap


----------



## MarkZ

You should start a new thread with a concise summary of what's been recommended so far. I, personally, am too lazy to go through the whole page.


----------



## CobraVin

maybe i should, i just figured geo would have this thread bookmarked, i sent him an email

i went through the thread, my only question is which signal wires go where using a balanced din cable(symbilink) into the amp, thats where there seems to be a couple different opinions, which is why i highlighted the quotes in red, hoping to make it easy for someone to answer

but hey thanks for the bump and it beats talking to myself


MarkZ said:


> You should start a new thread with a concise summary of what's been recommended so far. I, personally, am too lazy to go through the whole page.


----------



## MarkZ

CobraVin said:


> maybe i should, i just figured geo would have this thread bookmarked, i sent him an email
> 
> i went through the thread, my only question is which signal wires go where using a balanced din cable(symbilink) into the amp, thats where there seems to be a couple different opinions, which is why i highlighted the quotes in red, hoping to make it easy for someone to answer
> 
> but hey thanks for the bump and it beats talking to myself


Sure. Sorry I can't be of more assistance. I don't know the symbilink pinout. Sometimes things get lost in the fray when it comes to these old threads...


----------



## CobraVin

i have the zapco pin diagram so i know which is which (L- R+), i just dont know what is supposed to get combined so the amp cancels it out, i know it was in the original werewolf thread, and it is mentioned in this thread, there just seems to be some different opinions, cause i know if i just pick one of the suggestions and solder up the wires its gonna turn out to be the other one

although im nearing the end of the install i still have other stuff to work on so im hopefull ill get a definitive answer, thanks


----------



## Ge0

Just caught this one.

Realize what a balanced amp does on each input channel. In this case your left channel and right channel. It subtracts the positive signal from the negative. This is called differential input.

Rdiff = (R+ input) - (R- input) = 2R

Ldiff = (L+ input) - (L- input) = 2L

The result is a left and right signal that is twice the amplitude of the original signal.

I wrote:


> It helped me to draw this out. L- and R- coming out of the balanced line transmitters are left unterminated. L+ is split and sent to the left and right + inputs on the amp. R+ is split and sent to the left and right - inputs on the amp.


Take the Rdiff and Ldiff expressions shown above and make the substitutions I mentioned in the quote:

Rdiff = (L+ input) - (R+ input) = L-R

Ldiff = (L+ input) - (R+ input) = L-R

There you go.

I opted to wire my PS2 cable a little differently (as was seen in the diagram on the photo on page 6):

Rdiff = (R+ input) - (L+ input) = R-L

Ldiff = (L+ input) - (R+ input) = L-R

Why R-L? Well, it is L-R 180 degrees out of phase. I did this to de-correlate the rear outputs without having to remeber to switch phase in the amps software.

-(R-L) = L-R

In either case, L- and R- on the original cable end that would have plugged into the amp are left unterminated. Route the remaining L+ and R+ signals as I mentioned above.

Does this make any sense?

Ge0


----------



## CobraVin

Does this make any sense?

for the most part, i think:blush:

i wired it this way

L- and R- coming out of the balanced line transmitters are left unterminated. L+ is split and sent to the left and right + inputs on the amp. R+ is split and sent to the left and right - inputs on the amp. 

ill just swap phase inside the dc 350 to decorrelate

anyway i wired it up and im finishing my install so i just wanted to thank you for the response and bump the thread, ill update it with my results


----------



## kappa546

ok going to revive this thread for a quick question. regarding the rear fill channels, is one channel wired L-R and the other is R-L? and just to make sure i'm understanding this correctly, is this literally how you connect each speaker ie: RC get +L and -R while the LC get -L and +R?


----------



## Ge0

kappa546 said:


> ok going to revive this thread for a quick question. regarding the rear fill channels, is one channel wired L-R and the other is R-L? and just to make sure i'm understanding this correctly, is this literally how you connect each speaker ie: RC get +L and -R while the LC get -L and +R?


Both rear fill channels should be wired L-R.

I was commenting earlier that I just happened to wire my symbilink converter cable L-R (drivers side) and R-L (passengers side). Perhaps on purpose, perhaps by dumb luck. It's been a while ago. I can't remember.

However, this is easy enough to fix with the Zapco processor or through speaker cable swapping. I simply swapped phase 180 on the passengers side. R-L inverted 180 degrees is -(R-L), or, you guessed it L-R!

Ge0


----------



## mitchyz250f

Hey Geo,

Have you done any more experimenting with your rear fill? What is your current setup with the rear fill, crossover, dealy, are the rear fill over lapping your midbass..?


----------



## 14642

When you do the L-R thing for rear fill, be sure to cross the speakers over outside the range of the midbass. That out-of-phase midbass can wreak havoc on trying to get good midbass and bass placement in the front of the car. I suggest 200Hz and up for rear and side speakers that use phase changes, reversal or dynamic phase stuff for ambience processing--especially in cars.


----------



## Ge0

I've read many articles on L-R rear fill and how to properly implement it. All for home audio use mind you. For the car, the same principles apply, but you can throw standard implementation out the window.

All speakers in my vehicle are in proper acoustical phase at the primary listening position (regardless of electrical phase). This was measured through recommendations from NPdang in his RTA threads in the tutorial section. 

I don't fear midbass cancellation from the rears in regards to the front since I don't have wicked phase based cancellation (and as a result have damn nice up front midbass). Rears are delayed by 23ms (left) and 27mS (right). Crossovers are highpassed at 90Hz 24 db/octave and low passed at 2.5KHz at 6dB/Octave. Left to right frequency spectrum is matched on all speakers. Overall response set as close as possible to my target response given 1/12th octave resolution.

The results are pretty damn pleasing to me. Room for improvement, of course. But, I feel I'm 90% there...

Any specific questions are welcome.

Ge0


----------



## braves6117

Ge0 said:


> Any specific questions are welcome.
> 
> Ge0


Geo, I read the whole thread. Great job and concise help, I appreciate that.

However, no one really touched on the power needs for rear fill. Some of the posts refered to using a 2 channel amp, factory car amp, or even the head unit...thus I'm curious as to what your successful setup uses. Other's are welcome to chime in as well

Additionally, what type of speaker are we talking about? Can an 8in midwoofer suffice (since I have that on hand), or would a 6.5 midwoofer better suit the parameters of the hard left and right signals? 

This is the first reading I have done regarding the rear fill. And yet, I have discounted that option as recommendations for guys asking for help and SQ....That's not smart on my part. What is smart is expanding my mind with ideas such as this.


----------



## Ge0

braves6117 said:


> Geo, I read the whole thread. Great job and concise help, I appreciate that.


Thanks for the good words.



braves6117 said:


> However, no one really touched on the power needs for rear fill. Some of the posts refered to using a 2 channel amp, factory car amp, or even the head unit...thus I'm curious as to what your successful setup uses. Other's are welcome to chime in as well.


This is not necessarily a straight forward question. The idea is to have the rear fill play loud enough just to add an effect, not stand out. You'll know when you have dialed it in just right. Your stage widens like a mother trucker. You feel like you are in a much larger space. Getting the proper balance really all depends on how your front stage is set up. If you have butt loads of power going to the front stage, chances are you should have at least a couple butts of power in the rear.

For example, my front stage is 50x2 for tweets, 100x2 for midranges, and 300x2 for midbasses. Tweets and midranges are in the 90+ efficiency range. midbasses are lucky if they reach 87db. To get the right balance, I drive my rear fill with 100Wx2 with fairly efficient (92db 1W/1M) speakers. I use my head units fader to create the right amount of rear ambience vs. the front. Usually step it back a few notches from center.



braves6117 said:


> Additionally, what type of speaker are we talking about? Can an 8in midwoofer suffice (since I have that on hand), or would a 6.5 midwoofer better suit the parameters of the hard left and right signals?


The midwoofer would work just fine assuming it can play the range from 100Hz or such up to 2KHz or such... No real rocket science here. Just make sure you can tame their frequency response to match the rest of the system. I see you have a Zappy processor so that is a good start.



braves6117 said:


> This is the first reading I have done regarding the rear fill. And yet, I have discounted that option as recommendations for guys asking for help and SQ....That's not smart on my part. What is smart is expanding my mind with ideas such as this.


Never discount anything until you have tried it for yourself and feel confident that you have implemented it properly. I'm going to be honest here. I'd rather see people not try rear fill at all if they are not going to implement it properly. Simply hooking up your head units rear channels does not cut it. You need to perform at least rudimentary L-R processing to gain benefit. Sure, better means exist to expand/improve your soundstage. However, the equipment necessary does not really exist as standard issue gear for the car yet.

By all means try this out if you have the equipment/patience to do so. You will not be disapointed.

Ge0


----------



## balonglong_1979

greetings from singapore.

i'm reallly intrigued by this - and read just about every thread here on L-R rear fill. now i would like to try this, but..

all i have is a bridgeable amp, so i can connect the rear spkrs in series & bridged into mono channel.

but i don't have a processor - is there any other way to get the L-R signal?
can i simply wire the L- to the R+ of the speaker? (and vice versa)

all i have are RCA outputs to the pre-amp (using an Eclipse 7100 hu) 


help


Update : I've wired the rear spkrs in series using bridge mode, (which is effectively a Hafler matrix, right?) & I'm getting mono sound (that's a start)
now the reason i don't get the L-R is because of built-in phase inversion of the amp in bridge mode, right?

SO now im postulating - if i connect the L- to the R+ of the amp output for e.g., will the difference signal be obtained? Will i risk blowing the amp ??


----------



## Ge0

balonglong_1979 said:


> greetings from singapore.
> 
> i'm reallly intrigued by this - and read just about every thread here on L-R rear fill. now i would like to try this, but..
> 
> all i have is a bridgeable amp, so i can connect the rear spkrs in series & bridged into mono channel.
> 
> but i don't have a processor - is there any other way to get the L-R signal?
> can i simply wire the L- to the R+ of the speaker? (and vice versa)
> 
> all i have are RCA outputs to the pre-amp (using an Eclipse 7100 hu)
> 
> 
> help
> 
> 
> Update : I've wired the rear spkrs in series using bridge mode, (which is effectively a Hafler matrix, right?) & I'm getting mono sound (that's a start)
> now the reason i don't get the L-R is because of built-in phase inversion of the amp in bridge mode, right?
> 
> SO now im postulating - if i connect the L- to the R+ of the amp output for e.g., will the difference signal be obtained? Will i risk blowing the amp ??


All the information you require is burried within this thread. Just take a few hours to read through it .

To make a long story short. You can create a Hafler Matrix by wiring the series combination of your rear speakers across the "+" output terminals of the rear fill amp (effectively bridging a set of speakers wired in series) . However, without adequate digital time delay you will not obtain the full affect. Without the required time delay your sound stage will not seem much larger.

Ge0


----------



## partysnatcher

Have I misunderstood this completely, or is the L-R effect a mono signal?
I mean, mathematically, |L-R| = |R-L|..

If not, how is this mathematically for each channel?


----------



## MarkZ

partysnatcher said:


> Have I misunderstood this completely, or is the L-R effect a mono signal?
> I mean, mathematically, |L-R| = |R-L|..
> 
> If not, how is this mathematically for each channel?


Haven't read this thread in a while so I'm not sure about the context but...

I think it depends on how you define "mono". L-R is the same as summing L and the inverted polarity R, which is pretty much an L+R signal. If you consider L+R to be "mono", as many do, then so would L-R.

You can also calculate L-R a little differently. Rather than subtracting one directly from the other, you could subtract out the common spectral components. That's generally how one would go about forming an L,C,R from just an L,R signal. I haven't really seen a good real-time software implementation of this though. I wish someone could point me in the right direction. Maybe time for a new thread...


----------



## partysnatcher

Thanks for the reply!

The context / the reason I am asking; I am programming my own "DIY" DSP rearfill module as a home project. The spectral subtraction (a kind of L-R vocoder?) sounds very cool, but would be a little too complex for me at this point.

Plain old L-R might work, not saying it won't, but I am also considering something like this (from a quick brainstorm earlier today):

L = L * |L-R| / |max diff|
R = R * |L-R| / |max diff|

maybe putting a ceiling on |L-R| so it doesn't go over max diff.

The objective here is some sort of "stereo L-R". While still removing the centre; if a sound plays in the left channel only, it will still only play in the left channel in the rear fill (whereas L-R, as I understand it, would play the sound in both).

I have no idea how this would sound, but I will test both approaches out. The goal is maximum soundstage in my car.


----------



## MarkZ

I'm not really sure what "max diff" means, exactly.


----------



## partysnatcher

Sorry, I meant the biggest achieveable difference between L and R (in 16 bit sound this max difference is 65535).

But now I see that this would "choke" a signal that is played at lower volume.. ehm. I will play with this some more. 

Your spectral / vocoder method would definitely work for stereo L-R though.


----------



## MarkZ

The maxdiff thing would only be normalizing the signal, then. So I don't think it would work the way you're intending.

Ultimately, if you're trying to get what's unique to L, it requires more sophisticated processing. The spectral analysis route is one way to go. Wavelet methods might be another. Seems to me that one of the problems with those methods is that they're acausal -- you'd have to window your data by whatever lag is acceptable (say, 128ms), and then you're performing an FFT (or something like it) on a relatively few number of samples which is problematic itself.

I tried this one VST plugin that tried to do something similar, and it SUCKED. That's why I was wondering if anyone else has run into a way of doing it better.

Or you could just re-record your music files in L/C/R format, which wouldn't require the acausal limitation...


----------



## partysnatcher

Yes, I will look at this some more. I'm sure people have tried most variations of what we're talking about.
That said, "plain" L-R seems good enough, by all means. It is natural that reverberated sound is a little more mono than the original.

The spectral version would definitely work, but the quality would depend on the amount of bands my unit could handle.

I have a second algorithm in store, but I will try it out in practice before I contaminate this thread with more brain farts.


----------



## 14642

Hmmm...sounds like you guys are reinventing the rear channels of PLII or Logic7 or nearly any other matrix processor. Granted, some of them use the same signal for the rear left and right (basically a simple L-R). Later versions have improved left and right rear separation--often that improvement was the design goal. 

I think Wikipedia has a pretty good explanation of this if you look up PLII.


----------



## gijoe

I've asked this in another thread a while ago, but didn't really get any help. Maybe this isn't the appropriate place to ask but...

How can L-R be accomplished without balanced outputs? I've read through most of this thread, and I don't recall seeing an answer. 

If I wanted to do some experimenting with rear fill, what is the minimum equipment that I could get away with. I have an 880prs to a zuki 4 channel for my front stage. I gather that I'll need 2 more channels of amplification, but beyond that I'm lost. It may not even be worth attempting with this setup since any signal I plug into the new amp will have to be split from my main front stage, therefor it'll already be processed with TA.

Oh well, maybe it's just not meant to be right now.


----------



## MarkZ

gijoe said:


> I've asked this in another thread a while ago, but didn't really get any help. Maybe this isn't the appropriate place to ask but...
> 
> How can L-R be accomplished without balanced outputs? I've read through most of this thread, and I don't recall seeing an answer.


I have no idea. I use a computer.

I know the Behringer DCX2496 allowed you to sum. L+R. I bet there are a lot of head units that do it too. I haven't been in the market for a head unit in about 10 years, so I don't really know which ones do what.

Honestly, I have no idea why people want L-R.  L+R, ok. But why phase invert the R? You sure you don't mean L-C? [C is NOT the same as L+R]


----------



## gijoe

MarkZ said:


> I have no idea. I use a computer.
> 
> I know the Behringer DCX2496 allowed you to sum. L+R. I bet there are a lot of head units that do it too. I haven't been in the market for a head unit in about 10 years, so I don't really know which ones do what.
> 
> Honestly, I have no idea why people want L-R.  L+R, ok. But why phase invert the R? You sure you don't mean L-C? [C is NOT the same as L+R]


Well if I understand correctly, C would be the information that is shared between the L and R. In a mono recording this would be everything. L-R is kinda the opposite. You aren't shooting for the standard mono in the rears, you're trying to take out that shared mono info (C) altogether and play the rears without the distinct C, that actually equates to a large percentage of what is on most stereo recordings. Eliminating this leaves only the info that is specific to the L and the information that is specific to the R, without the shared info. This is how you get the ambiance and wider stage.

Correct me if I'm wrong, or if I've over looked something important.


----------



## MarkZ

gijoe said:


> Well if I understand correctly, C would be the information that is shared between the L and R. In a mono recording this would be everything. L-R is kinda the opposite. You aren't shooting for the standard mono in the rears, you're trying to take out that shared mono info (C) altogether and play the rears without the distinct C, that actually equates to a large percentage of what is on most stereo recordings. Eliminating this leaves only the info that is specific to the L and the information that is specific to the R, without the shared info. This is how you get the ambiance and wider stage.
> 
> Correct me if I'm wrong, or if I've over looked something important.


The information that is shared between L and R is not the same as L+R.

L = information common to both + left only
R = information common to both + right only

Therefore...

L+R = (2x) information common to both + left only + right only

I think people are thinking of L-R because you subtract out the information common to both. But then you're left with left only minus right only, which doesn't isolate a single side either. L-R is the same as L plus a phase-inverted R.

So, the point of advanced algorithms is to extract the information common to both, which requires a much more sophisticated approach than the mere addition and subtraction of signals. I don't know how the Dolby matrix algorithm works though. Andy, do you have a link? The wikipedia entry didn't really say much...


----------



## 14642

Try these:

Dolby Pro Logic - Wikipedia, the free encyclopedia
Matrix decoder - Wikipedia, the free encyclopedia


----------



## Oliver

gijoe said:


> Well if I understand correctly, C would be the information that is shared between the L and R. In a mono recording this would be everything. L-R is kinda the opposite. You aren't shooting for the standard mono in the rears, you're trying to take out that shared mono info (C) altogether and play the rears without the distinct C, that actually equates to a large percentage of what is on most stereo recordings. Eliminating this leaves only the info that is specific to the L and the information that is specific to the R, without the shared info. This is how you get the ambiance and wider stage.
> 
> Correct me if I'm wrong, or if I've over looked something important.


You got it right


----------



## MarkZ

Andy Wehmeyer said:


> Try these:
> 
> Dolby Pro Logic - Wikipedia, the free encyclopedia
> Matrix decoder - Wikipedia, the free encyclopedia


So the values in the matrices are supposed to be the coefficients corresponding to each signal? Then you just linearly add them?

It's not clear to me what the phase shift is doing in the "rear" channels.


----------



## BMWTUBED

Hooked this up per GeO's discription. 
Go grab your copy of Pink Floyd Pulse Live,
go to "run like hell" and turn it up to as close
to concert level as you can! I was back at 
the concert (1994ish) from this very simple
mod. Absolutely awsome! I'm going to go 
listen to the entire album now!


----------



## BMWTUBED

BMWTUBED said:


> Hooked this up per GeO's discription.
> Go grab your copy of Pink Floyd Pulse Live,
> go to "run like hell" and turn it up to as close
> to concert level as you can! I was back at
> the concert (1994ish) from this very simple
> mod. Absolutely awsome! I'm going to go
> listen to the entire album now!


Forgot to mention, that concert had "rear fill" speakers!!
Yes, there were speakers to the side and behind us!!!


----------



## Ge0

I've been meaning to post a response to this thread for some time but have not made time to. My bad...

I'm glad that someone has had a favorable experience with trying this flavor of rear fill. It's no joke. Just try it.

Others have been contemplating the physics. Just let me add this:

The whole idea is to enhance the stage, not distract from it. 

L-R rear fill is essentially a differential amplifer that subtracts common mode information (err, vocals) and leaves differential mode information (err, everything else). Add a delay (within your personal threshhold of the precidence effect) into this and you trick your brain into thinking that the rear signal is actually a reverberation off a surface some far away distance behind you. The amount of delay corresponds to how big you want the listening space. But, there is a limit. Don't delay it too much our you'll detect and echo instead. This is bad. The proper delay enhances the size of your listening space. It does not add confusion. While you are at it. Make sure your frequency response is identical (within reason) for all channels or you risk ruining the illusion.

Yes, this is a mono signal (meaning the same information is sent to left and right rear speakers).

You should not be able to detect the rear fill is even there. You should gain the illusion that the stage is bigger, better, wider, and deeper, than you would have ever experienced without the rears.

Why subtract the vocals? Well, everyone wants a well defined center that is far in front of you right? Removing the vocals from a delayed rear does not ruin this frontal illusion. Rather, it enhances it. There is enough information going on elsewhere to trick your brain into thinking that the reverb leftovers it recieves is real enough.

I can't explain this to any degree of technical detail but will just say "it's Psychoacoustics".

I hope I did not leave anything out.

Ge0


----------



## Oliver

Ge0 said:


> The whole idea is to* enhance the stage*, not distract from it.
> 
> You should not be able to detect the rear fill is even there. You should gain the illusion that *the stage is bigger, better, wider, and deeper*, than you would have ever experienced without the rears.
> 
> Ge0


You covered it Geo 

I'll bet most cannot achieve it


----------



## Ge0

a$$hole said:


> You covered it Geo
> 
> I'll bet most cannot achieve it


WTF are you still doing up? I'm not the only one who can't seem to sleep I guess.

THX.

Ge0


----------



## Oliver

I'm a third shifter  

"All Night Long" ~ Lionel Ritchie
"Still" ~ Lionel Ritchie


----------



## tspence73

Ge0 said:


> I've read through tons of messages regarding using rear fill with the difference signal of L-R. I like the concept and want to try it.
> 
> 
> Ge0


This is the precise method used by the SRS processor in my JVC unit, only it's a very controllable processor. It's not really necessary if you have well placed on-axis front speakers. The L-R effect is sometimes good and sometimes not depending on the track. I don't use it anymore now that I have front speakers only. I recommend if you are hell bent on using a L-R rear fill effect that you buy an SRS processing HU. It will turn out MUCH better and allows much more fine tuning.


----------



## tspence73

Andy Wehmeyer said:


> Hmmm...sounds like you guys are reinventing the rear channels of PLII or Logic7 or nearly any other matrix processor. Granted, some of them use the same signal for the rear left and right (basically a simple L-R). Later versions have improved left and right rear separation--often that improvement was the design goal.
> 
> I think Wikipedia has a pretty good explanation of this if you look up PLII.


I just got around to Andy's posts and he's right. But the SRS processor built into some HU's are far more effective at this and give more tuning options for you.


----------



## MarkZ

What's SRS?


----------



## Ge0

tspence73 said:


> This is the precise method used by the SRS processor in my JVC unit, only it's a very controllable processor. It's not really necessary if you have well placed on-axis front speakers. The L-R effect is sometimes good and sometimes not depending on the track. I don't use it anymore now that I have front speakers only. I recommend if you are hell bent on using a L-R rear fill effect that you buy an SRS processing HU. It will turn out MUCH better and allows much more fine tuning.


I know the SRS brand label (available on some television sets). They resell algorithms licensed from others.

It may be similar or the same. Don't know enough to comment. What I can comment on is that if L-R rear fill is tuned in properly (read the physics involved throughout the whole post) it doesn't matter what track you listen to. It enhances all. Understand the concept. Not the marketing tricks/jaron.

Ge0


----------



## less

envisionelec said:


> The real name of that connection is the Hafler. I remember seeing it in one of my 1968 Radio-Electronics mags and trying it when I was 14. I had a room full of speakers wired series-parallel. I probably had 25 speakers...but just two sounded better than all of them, so I had a garage sale


Ahhh. those were the days! You sound like me my friend... played the lamp shade in my brothers band at age 4, had a "radio station" in my closet at age nine, and instead of getting clothes and such, I got speakers or electronics for every birthday and holiday lol.

As for this ambeince enhancement system, I was so stoked by the idea of a "free" surround sound effect (this is back in the days where Quadrophonic was being toyed with too - and idea ahead of its time!), that I HAD to try this out! Honestly, while in concept it was cool, in reality it didn't really make the difference I was hoping for - but maybe in a car....

As for Mr. Hafler, when I finally outgrew that insanely hot looking Kenwood integrated amp, the first real amp I bought was a David Hafler DH200 - hand built of course! MY mom won the thing in a drawing at the local electronics shop and OMG it made my day! I sold the Kwood to buy the matching preamp kit and connected it to my ADS 200 satelittes and M&K sub... then later my ADS 710s for aural bliss!

Sorry for the reminiscing here - but the thread struck a chord! Hope this turns out to be fun for you Geo.

Jim


----------



## mitchyz250f

Has anyone played with how the speaker aimed. I will likely be using the rears from 300 Hz or so to 1500 - 2500 Hz. My 2" or 3" rf speaker will still be omni dorectional. My car is a hatchback and the best location is on the hatch firing straight down into the carpet! What do you guys think.


----------



## Oliver

up again for some great info !


----------



## Oliver

up ^^^


----------



## Candisa

So I decided to do this L-R delayed rear-fill now I have a headunit with TA I can use.
I can do up to 15ms of delay, I guess that should suffice in a Volvo 740 sedan with the rear-fill on the rear-deck.

The problem is the L-R signal...
The amp I'll use for the rear fill does have a switch to choose if you run it bridged or not, but I'm not sure if it works like an non-bridgeable amp if you set the switch to non-bridged, so I rather create the L-R signal before the amp.

The most logical way to do this would be by inverting the phase on the right-rear-channel on the headunit and leave the left-rear-channel alone and then run those 2 together to the bridged amp: L+(-R) = L-R... Perfect...

Well, apparently, the headunit cannot invert the phase of a single channel, only per pair of channels...

So this needs a plan B...

Since interlink between the headunit and amplifier isn't balanced, I can't just swap the +R with the -R cable in the interlink, so the only way to create a -R signal is by swapping the ground cable with the signal cable on 1 end of the right-side of the RCA cable that's between the headunit and the rear-fill amplifier.
The only problem is this would result in shorting and thus blowing out the right-rear-line-output of the headunit, since in most amplifiers ànd amplifiers, the ground of the RCA in-/outputs is shared with the ground of the power supply.

To solve this issue, I would use a ground loop isolator.

Am I thinking correctly that I can build a headunit- ànd amplifier-safe (L)+(R) to (L)+(-R) device (so I don't have to use abnormally wired RCA-cables) by getting a ground loop isolator, open it up and swap the right-out-ground wire with the right-out-signal wire inside?

I suppose any ground loop isolator out there uses a pair of 1:1 transformers?

Isabelle


----------



## tornaido_3927

How much time effort is that going to take Isabelle?
Would it be feasible to maybe buy something like the Zapco RCA - balanced transmitter (_SLDIN-T.F_ I think) and just splice/solder RCAs to it using the inverted signal? It would also be a separate device unlike a plain RCA cable that you would be able to distinguish from other cables so you wouldn't be likely to accidentally use it wrongly?


----------



## Candisa

Well, like I said, I am NOT planning on making a special RCA cable that can be used wrong because it's interchangeable with normal RCA cables.

Since I'll have to use a ground-loop-isolator anyways, I'm planning on inverting the signal inside this ground-loop-isolator (and mark it as being a (L)+(R) to (L)+(-R) convertor, by getting the ground-loop-isolator I need and customizing it by swapping the ground- and signal-wire of the right-output internally.

This way, it will be a separate device, just like you are suggesting, but most likely with a much cheaper "donor"-device. (I guess that Zapco RCA-balanced transmitter costs quite a bit more than a simple ground-loop-isolator?)

I don't think this'll cost me a lot of time to make. It's only a matter of opening up the isolator, unsolder 2 wires, solder them back the other way around and close the isolator again.
I have a Dremel-like tool, a hot-glue-gun and a soldering-station, so this job shouldn't take long (I know I just waked up Murphy by saying this...)

The only thing I have to know for sure to make this work, is if any ground-loop-isolator on the market is using 1:1 line-transformers to isolate the outgoing signal from the ingoing signal, or if some of them (or most of them, or all of them?) use different technologies that also works great as a ground-loop-isolator, but won't work to invert the signal...


----------



## Oliver

Candisa

are you aware the JL Audio Slash 500/5 will do what you want ?

download file from JL Audio site in a PDF format and read what it says 

When you select ambient feature, this allows for L minus R info without detracting from front imaging.


----------



## Candisa

I actually did know that, but I don't own a JL Audio 500/5, and while I actually like the JL Slash series amplifiers, I'm not willing to buy another amp anymore, since we already own a LOT of amplifiers. 
Unfortunately, none of them has this L-R thing built-in and neither does the headunit, so that's why I'm planning on building my own "L-R signal creator".


----------



## XC-C30

Only about 15 if I counted right.....

Or am I missing a few honey? :laugh:


----------



## Candisa

1-4: Genesis Dual Mono
5: DLS Genesis DM200
6: Crunch 600
7: Nakamichi PA-2100
8: Xtant 202m
9: McIntosh MC420M
10: McIntosh MC427
11-12: Clarion APA4300HX
13: Clarion APA4400
14: Clarion APA2100
15: Caliber CA180
16: Caliber CA460

You forgot one honey!

(Sorry for the off-topic)


----------



## mitchyz250f

Can't the old Soundstream D series amps do what you want?


----------



## Candisa

Candisa said:


> ...I'm not willing to buy another amp anymore, since we already own a LOT of amplifiers...


^^This

Sometimes, you just have to say: "I'm gonna work with what I've got"... Since we already own quite a lot of amplifiers and we've just bought a house, this is one of those times for us.

I have this install completely figured out in my head, including what gear I want to use, and I'm sure this is one of my plans I actually want to build...
I'm not thinking of changing this plans again since this might be one of my best plans that combine great sound with a nice and clean looking trunk and no compromise.
Anything I want from an install is in these plans...

I just need a device that converts a (L)+(R) pair of signals into a (L)+(-R) pair of signals, without the risk of destroying expensive and/ore rare gear.

That's why I want to know if any ground-loop-isolator on the market uses a pair of 1:1 transformers to isolate the outgoing pair of signals from the ingoing pair of signals, since I think the best way to invert a line-level signal with full separation is by using 1:1 transformers.

I can't find a pair of affordable 1:1 line-transformers on the West-European market, that's why I'm thinking of modifying a ground-loop-isolator...

Isabelle


----------



## Oliver

Maybe ... there is something here that will help.



Balun



> Balun Transformers
> 
> A Balun is a device which converts balanced impedance to unbalanced and vice versa.
> 
> 
> (Example: Some Mini-Circuits models with prefix TCN and NCS). LTCC baluns are very compact (such as 1206 or 0805 size). Commercial Marchand baluns operate above 600 MHz. Theoretically, they can provide any impedance ratio, but commercially available baluns are generally limited to 1:1, 1:2, 1:3 and 1:4 ratios.


----------



## Candisa

Well, I need 2 transformers like the one in figure 1a of your link. 
I just don't know where to find them at a reasonable price.

I did find a few webshops that carry Lundahl "Interstage-transformers", but those cost about €100 ($130-ish) a piece!

I don't need something very high end, I just need a couple (preferably small) 1:1 ratio transformers that have a high enough primary impedance for the headunit's pre-outputs.

Isabelle


----------



## mitchyz250f

I am not sure exactly what you are trying to do, but Gary S. said in an earlier post the the old SS reference amps could be used to get rear fill. Read post 79 also.




Gary S said:


> - That's exactly right... I believe it is also called a BTL amp.
> 
> Or, you need an amp WITHOUT a tri-way phase inverter in one of the channels for this Hafler hook-up, aka rear surround channel(s).
> 
> I've been using old Soundstream Reference amps in my own systems for years... the reference amps and a handful of others had what they called "coherent stereo"... it was simply a switch to turn the phase inverter on or off... in "stereo" position, the phase inverter is bypassed... in the mono position, the phase inverter would be engaged so you could bridge the amp (summed) mono. However, these amplifiers have not been made for years, and the few that I like that come across ebay from time to time are ridiculously expensive compared to modern amps. Right now, I'm looking at some new amps... some of the sony amps claim to be 4/3 channel only... the front channels are not bridgeable... because they don't have a phase inverter in one channel. See the manuals on these amps for more.
> 
> I'm going to try one... if it works, and if it's not enough power for me, I'll get two and vertically biamp, using one pair of channels for each satellite.
> 
> If that does not work, there are at least 5 different head units available right now with SRS circle surround ll (cs auto NOT SRS WOW)... 4 Panys and a new Eclipse... but like you, I would rather do it with the amp... that way, I am free to pick and choose from any head unit. Plus, it just makes more sense to me... I mean, we bridge amps "summed mono" all the time... that's a summed, 3rd, matrixed channel, if you will... doesn't it make sense to derive the difference signal from the amplifier also?


----------



## I800C0LLECT

I'm not quite sure if this will help...but here's my idea on how to achieve the L-R

http://www.diymobileaudio.com/forum/dumb-question-forum/69956-how-create-difference-sums-l-r-r-l.html


I never implemented it. I played with rear fill and really liked it. Just hard to get around to my projects


----------



## lycan

haven't read this whole discussion, but posts #26 through #29 in this thread may help:

http://www.diymobileaudio.com/forum/diyma-tutorials/81191-rear-fill-speakers-2.html


----------



## Candisa

I asked this question on a dutch diy-home-audio forum too, and in the meanwhile, I've found a webshop that sells cheap ground-loop-isolators (€15/$20 shipping included!) that claim to have transformers inside.
The shop also claims you can use them to convert a balanced signal into an unbalanced signal, so I'm willing to believe they've actually got a pair of 1:1 audio-transformers inside.

I'm planning on buying such a ground-loop-isolator, cut the (plastic) RCA-connectors off and put it in a small metal enclosure with some nice female RCA-connectors, all soldered to the gli normally, except for the right-output, that one will be soldered inverse (ground to signal, signal to ground).

This way:
- I don't have to use special cables (that can blow something when used in a place they can't be used), 
- the phase of the right channel is inverted and
- the headunits rear-right output will have the load of the input-coil of the transformer at all times with no connection to the ground, no matter if the wires on the output-coil are swapped out or not...

Isabelle


----------



## Oliver

lycan said:


> haven't read this whole discussion, but posts #26 through #29 in this thread may help:
> 
> http://www.diymobileaudio.com/forum/diyma-tutorials/81191-rear-fill-speakers-2.html


Thanks Lycan !

Candisa, does this work for you ?

EDCOR - WSM10K/10K

WSM10K/10K
Rohs

Matching Transformer
0.5W, matching transformer, 10,000 Ohms to 10,000 Ohms.

Price: $ 10.23 USD


----------



## Candisa

I live in Europe, so because of shipping costs and import-taxes, is ain't interesting for me to buy stuff from the USA.

I'll give the GLI I've found a try.


----------



## Oliver

Candisa said:


> I live in Europe, so because of shipping costs and import-taxes, is ain't interesting for me to buy stuff from the USA.
> 
> I'll give the GLI I've found a try.


 

*If you are curious....*


EDCOR Electronics will quote prices and delivery according to your request. Please call 575-887-6790 or contact us for more information.

Catalogs:
Catalogs may be downloaded from this website here. These catalogs may assist you in detailing your needs. Our website contains current product information.

Payment terms:
here.
Payment: Any sales outside the USA must be paid with a verified PayPal.com account or by bank wire transfer before manufacturing or shipping of any product.


Orders:
Mail your orders to: *EDCOR Electronics, 7130 National Parks Highway, Carlsbad, NM 88220*.
Phone your order to: 575-887-6790. We are open Monday through Friday 7:00 AM – 4:00 PM (MST).
Fax your order to: 575-887-6880 Fax lines available 24 hours per day, 7 days per week.
*E-mail your order to: To Sales Department.*

Shipping Methods:
Orders will be shipped USPS Flat Rate unless otherwise specified.


----------



## BowDown

Did you ever find a ground loop isolator to do this with? This is very intriguing. I would be willing to follow suit.


----------



## BowDown

Anyone know where I can find a "PhaseAround" by FineLine Audio? 

Looks like this device made in the 90's does exactly what us 'unbalanced' rca people need.


----------



## BowDown

Candisa said:


> I live in Europe, so because of shipping costs and import-taxes, is ain't interesting for me to buy stuff from the USA.
> 
> I'll give the GLI I've found a try.













So you would need 1 per RCA channel. 

Left would be wired straight-thru, Right would be swapped on the output (assuming your amp doesn't have a bridged mode switch which mine does not). What would connect to pin 2/6? Is that for a common terminal like a chassis ground?

Also why do the L+/R+ w/-'s connected on the output of the amp when you could do something similar right after the transformers? Or can't it be done there?

Just bought (2) transformers from Olivers link! Woohoo.


----------



## BowDown

Also one more question. When you speak of delay as being 20-25ms... is that total, or additional on top of the natural delay of being 8ft away?

Ge0.. what are you using to generate this delay? Considering most HU's cap at 10ms...


----------



## BowDown

Got my relays in a week or so ago... Going to wire this up next weekend. Any feedback on the ground loop isolator polarity switch?


----------



## Candisa

I haven't tried this yet, but I'm sure it'll work, since using a GLI and swapping the ground with the signal wire on 1 side at 1 end of the isolator *will* make the amplifier 'see' a signal that is inverse to the signal that goes into the GLI.

Isabelle


----------



## BowDown

Any insight on my question of the wiring chart above? Those are the relays I purchased. Just want to ensure I am wiring them correctly.


----------



## BowDown

Nevermind. I just got off the phone with EDCOR. They said using it with unbalanced input/output you just leave the Center Tap pin alone. SWEET!


----------



## BowDown

Almost got my ground loop isolating/right channel polarity reversing transformer setup done! I canibalized a couple monster Y adapters and crimped some ends on em. The damn wire inside is 16ga! Sweet.

I'm going to coat the crimp connections in hot glue and rivit the transformers to the hobby plate tomorrow. Wont get to testing this until I can find a way to get an additional 20ms delay!


----------



## RattyMcClelland

Sorry to bump this up.

But when doing the L-R of a bridged amp. Then add the bandpass and then the delay. 20ms seems very excessive. Thats like 700cm of delay and looking at headunit specs not many can do this and only go up to about 13ms of delay. the Audison Bitone can do 22ms of delay.

So as i missing something here. 
Obviously the speakers are going to be behind me either in the c pillars (coupe) or on the rear parcel shelf (most likely 6x9 imagine mids or Legatia L6s). So naturally the speakers will be around 70cm to 130cm behind me adding more to the delay..


----------



## RattyMcClelland

???????????


----------



## audiguy

Ratty

You aren't missing anything. The 20-30ms isn't about distance. It is about your brain being able to disassociate the rear sound from the original. You need the delay.


----------



## Oliver

chad said:


> yessir





chad said:


> You combine L in phase with R out of phase, So you are adding (L)+(-R)... Mmm Kay? Now anything that is L+R, or panned dead center will be canceled out because in the summing it will net 0. If something is panned, say 1 dB in one direction then the result of the summing will cause it to have a 1 dB level over the CMRR of the receiving device. Anything panned hard right or left will result in full output.
> 
> But that's not the secret to the sauce. True Reverb is NOT L+R, it may get there in the space-time continuum but most of the time it's all over the place, because of this nearly all reverb in a recording will be reproduced by the front AND rear speakers in this application, anything ambient, that is allowed to float to "widen the stage" will go to the rears.
> 
> Remember old-skool first gen Dolby surround? That's it!
> 
> Chad





chad said:


> Not just the furthest left or right, think about it this way, A true L-R will end up being 3 dB louder than a hard pan  Hard pan is XV-0=XV L-R int eh recording will Be Xv+XV=2XV and we know that doubling of voltage into a known inpedance will result in twice the power that equates to 3dB.





werewolf said:


> yes, the oldest version is known as the "Hafler Matrix" ... Hafler simply connected a single rear speaker across the L+/R+ stereo outputs, with a pad for attenuation.
> 
> But we can do better, by not only forming an actively attenuated L-R, but also bandlimiting (like Dolby), and perhaps most importantly ... adding delay to, or beyond, the precedence (Haas) effect (in the vicinity of 20msec). Remember the goal of clever rear fill is NOT to help the back seat passengers, and NOT to "fill the cabin with music" in a way that detracts or smears the front stage, but rather to give the illusion of listening in a larger acoustic space. Proper delay will enhance, not detract from, the front stage.
> 
> As far as driving _two_ rear speakers, what we really strive for is some _decorrelation_ between them. Couple easy approximations include : simple inversion (one side is L-R, other is R-L), which will suffer from decreased midbass in the rears, simply adding different delays to the 2 different rears (described in detail in the paper quoted in one of the many long rear fill threads), or getting really fancy ... like a 90 degree phase shift between the rears  Problem is, Hilbert Transformers are not (yet) readily available in most car audio processors


*This is what you missed RattyMcClelland  ^^^^*


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## RattyMcClelland

Ok cheers. So when i get my P99 i will have to see how good it will sound with the max of 17ms of delay then.


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## Oliver

G'luck mate !


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## Ludemandan

For anyone looking to do this and thinking it's too complicated, it looks like bikinpunk found a drop-in solution.
http://www.diymobileaudio.com/forum/member-product-reviews/80665-minidsp-excellent-alternative.html

Check out the applications they have for this little DSP. One of them is a L-R delayed rear center channel! I'm buying one and I'll report back with my results in my build log.

Dan


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## Gary S

Update:

Some time ago, I wrote in a post that I was going to test a Sony amp which, in the schematic, claimed the front channels did not have an inverter (current amps have an inverter in one channel to make them trimode... the amp can run a stereo pair and a center channel/sub all at the same time from just two channels - this was made popular by Rockford Fosgate)... long story short, it had the inverter, I could not derive the L-R signal from the amp. I gave the amp away as a Xmas present.

I've been searching for "plug and play" devices I can recommend to my friends and family. There are a couple of current products that will work for surround... one is a Performance Teknique ICBM-5EQ ...It's a half-din preamp with SRS.










There appears to be quite a few car DVD players with different surround formats. Notably, the Sony MEX-DV2200 is a 1-DIN DVD/CD/MP3 player which, according to the manual, has Dolby Prologic ll "music" mode which will work for any stereo source... 










I think I will go with this for my next build, as my Kenwood cd dash unit and the changer are not working very well anymore... and with the Sony, I can add their HD tuner box and a changer.


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