# Let's talk about "proper" rear speaker use.



## 89grand (Nov 23, 2006)

OK, I'm going to come right and say I was wrong about rear speakers, and their potential value. I was right along with nearly everyone else saying "Ditch the rear speakers" whenever the topic came up. I'll admit, I've never done a system using rear speakers, but I do know that loud "rear fill" is a no no, but that doesn't mean proper use of rear speakers is bad.

I came to this realization a few days ago with the stock Boston Acoustics system in my Magnum. The stock setup consists of front 6x9 door woofers (low pass filtered around 200hz If I had to guess), 2 dash mounted 3.5" full range drivers (high pass filtered at around 200hz also) and rear 6x9 speakers running full range (I believe they run full range) and a factory amp running the show. Anyway, I had turned the fader nearly completely to the front back when I first got the car, mostly do to some sort of vibration of the panels from the stock rear speakers, but when I turned the fader closer to the center the other day, but still some what front biased, the whole sound stage opened up, I had better center imaging and just an overall better sound from the stock system with the rear speakers playing at a level reduced enough not to actually call attention to themselves

Now that was with unprocessed rear speakers, and probably not ideal, but even then it still made a big difference in the overall sound quality of the system, and it wasn't just added bass as the front 6x9's have more bass then the rears do, probably do to the door cavity vs the small area of the rear speakers more than anything else.

So anyway, I've been putting together another system for this car and was going to just disconnect the rear speakers altogether like I usually do, but now I'm wondering if that's the best choice. My sig isn't exactly up to date so as it stands now I have The Alpine PDX amps, the RE subwoofer, and the Dayton RS28's, but that's it as far as what's listed there. In addition to that stuff I'll be using DLS IR8's and an Alpine H650 processor with the stock deck. The RS28's will be in the factory 3.5 dash locations, the DLS 8's will be in the stock door locations and the sub in the back of course. Now what can I do with the Alpine H650 in regards to rear speakers to use them effectively and properly, because I have a new found appreciation for rear speakers that I didn't have before. One last note, if I have blending issues between the IR8's and RS28 tweeters, and I may very well, I'm prepared to replace the RS28' with either a small coaxial or wideband driver since I'll have many more crossover options with the H650 vs my old 880PRS deck which wouldn't have allowed that.

So, let's discuss proper use of rear speakers, and their benefits and more specifically what my best options are.


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## Abmolech (Nov 2, 2006)

http://www.diymobileaudio.com/forum/showthread.php?t=22523

Possibly most of what needs to be said is in there.

In a nutshell
Rear speakers:
Can help correct the acoustic crosstalk in a typical car audio setup (read better depth)
Centre the image
Raise the stage height
Provide a much better ambiance (IE it sounds more real)

Downside?
Cost
Open minded
Knowledge

There are a variety of ways of achieving this:
Processor
Balanced line output reconfiguration plus delay.

It possible to simply use a monophonic centre rear, however most processors lack the ability to provide a proper monophonic centre. (IE removing added reverberation)

Consider the use of an ambiophonics rears as better choice for most people, depending on the acoustic crosstalk of the fronts.


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## rockondon (Jan 18, 2008)

So if i understand right. A mix-mono rear ,with a typical Alpine H/U that gives10ms maximum delay. Would be worse off than no rear fill/ambiance.


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## Abmolech (Nov 2, 2006)

Possibly, ideally your looking for around 20 milli seconds.


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## FrankstonCarAudio (Feb 2, 2008)

Abmolech said:


> Possibly, ideally your looking for around 20 milli seconds.


I found in my system, that 25ms was the ideal.. at first I wondered whether I would need to delay given the large distance difference between front and rear (my rears are placed in the rearmost pillars in my wagon, and very off-axis), but the delay was still required.. that surprised me!
I also still needed to attenuate the rears by 5dB, which also surprised me given the same distance difference reason as before..
Any clues Abmo?

Mark


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## Abmolech (Nov 2, 2006)

The delay will help to give more sense of space, the greater the delay the more defined it becomes, however if you start getting into the 40 -60 Milli seconds, you get a strong reverberation effect, somewhat like stone walls of a cathedral etc. Push it into 70 Milli seconds and your into echo territory.

Attenuation?
This depends on speaker sensitivity and power amplifier gain settings. Again, if you shooting for a certain style of space, then it would depend on how much the walls would of attenuated the reflection. (normally there would also be a strong frequency roll off as well).

You can get into some surround sound style recordings that try to put you in the band/orchestra rather than the audience. Personally it sucks, but thats recording and sound producers for you. (They have lower integrity than a used car salesman)


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## FrankstonCarAudio (Feb 2, 2008)

Thanks, the delay answer was what I thought, but you just clarified it..

I thought I read somewhere (may have been in a discussion on the Hybrid site about Hafler effect) where Werewolf recommended around 7dB attentuation regardless of other factors, or that's the way it read to me.. he was making a general statement of the initial starting settings IIRC

To the OP, rear ambience speakers are definitely worth trying in your next system!
I was also of the opinion of "ditch the rears" until I started experimenting with it... worth the effort!

Mark


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## Ge0 (Jul 23, 2007)

89grand said:


> OK, I'm going to come right and say I was wrong about rear speakers, and their potential value. I was right along with nearly everyone else saying "Ditch the rear speakers" whenever the topic came up. I'll admit, I've never done a system using rear speakers, but I do know that loud "rear fill" is a no no, but that doesn't mean proper use of rear speakers is bad.
> 
> I came to this realization a few days ago with the stock Boston Acoustics system in my Magnum. The stock setup consists of front 6x9 door woofers (low pass filtered around 200hz If I had to guess), 2 dash mounted 3.5" full range drivers (high pass filtered at around 200hz also) and rear 6x9 speakers running full range (I believe they run full range) and a factory amp running the show. Anyway, I had turned the fader nearly completely to the front back when I first got the car, mostly do to some sort of vibration of the panels from the stock rear speakers, but when I turned the fader closer to the center the other day, but still some what front biased, the whole sound stage opened up, I had better center imaging and just an overall better sound from the stock system with the rear speakers playing at a level reduced enough not to actually call attention to themselves
> 
> ...


89G,

I've been using rear fill in every system I've owned for the past 10 years. When balanced right it can add to the experince rather than subtract it. This is what I have been preaching since I joined DIYMA over a year ago.

Then I found properly implemented L-R rear fill (read through my thread on the subject for more info). As Foxpro would say "well slap me on the ass and call me Charlie!". Hole-e **** did it make a difference! The sound stage opened up even more and I actually felt like I was witnessing a performance rather than listening to music in a car.

Now I'm taking it one step beyond. I've invested in equipment that will allow me to play with alternate playback methods and various surround formats. I'm hoping to step up music reproduction one more notch.

Seriously though, 99.9% of the car "audiophile" population would be perfectly happy with what they were able to achieve with properly implemented L-R rear fill. So, maybe this would be something to strive for first. It will satisfy me through next year until I'm ready to implement my "ULTIMATE AUDIO PROCESSOR".

Ge0


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## blackwolf (Feb 21, 2008)

Hey, Ge0...might you be up for doing a tutorial on "How to _properly_ implement rear fill in a car environment"? Sort of a condensed version of your very lengthy thread referenced above by Abmolech. IMO, you're certainly the prime candidate for authoring such a tutorial from an experience perspective and you certainly have the skill of articulating your thoughts very well. I think it would be beneficial, but that's just my opinion.


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## Ge0 (Jul 23, 2007)

blackwolf said:


> Hey, Ge0...might you be up for doing a tutorial on "How to _properly_ implement rear fill in a car environment"? Sort of a condensed version of your very lengthy thread referenced above by Abmolech. IMO, you're certainly the prime candidate for authoring such a tutorial from an experience perspective and you certainly have the skill of articulating your thoughts very well. I think it would be beneficial, but that's just my opinion.


I'd be glad to. That and I've been thinking about adding my own "how I tune my system" tutorial seeing how my methods vary from the average guys yet I obtain excellent results.

Ge0


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## Peteski (May 3, 2008)

I would love to see this tutorial as I read all the time like the OP said, he reads about how you have to ditch the rear fill, yet I kind of like it even tho my speakers are very close in back, (350z)


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## rockondon (Jan 18, 2008)

FrankstonCarAudio said:


> I found in my system, that 25ms was the ideal.. at first I wondered whether I would need to delay given the large distance difference between front and rear (my rears are placed in the rearmost pillars in my wagon, and very off-axis), but the delay was still required.. that surprised me!
> I also still needed to attenuate the rears by 5dB, which also surprised me given the same distance difference reason as before..
> Any clues Abmo?
> 
> Mark


What do you use to get 25ms delay.??
It also have a wagon. I tried placing the two rears close together next to the tailgate to aproxamate a mono rear. And using all the Alpine 10ms delay ,plus addjusting the rear volume. Frankly it sounded like ass.

I prefer rear speakers also. Turned way down [almost off]. 
Still i would like to have better sound. Like sitting in the audience. Not on stage.


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## rockondon (Jan 18, 2008)

Also......Mr Abmolech.
Can you give the link to setting up this ambiophonic setup.
I googled it and got book sales. Hmmmmm

And can these things be easily done by people without a carputer. 
I am interested in expanding the listening experience. But like many here ,I have a limited budget.


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## FrankstonCarAudio (Feb 2, 2008)

rockondon said:


> What do you use to get 25ms delay.??
> 
> I prefer rear speakers also. Turned way down [almost off].
> Still i would like to have better sound. Like sitting in the audience. Not on stage.


I used my Alpine H701 processor... What Alpine are you using that only has a max of 10ms?
Rear ambience speakers, if set up , will give you that audience experience, but I found that will only apply to a well recorded/mixed live recording, for normal studio stuff it will enhance the soundstage.. it just takes a lot of time and experimenting.. check out Ge0's link in his post here, and you will get a good idea of what's involved.
It's well worth trying some more.. 

Mark


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## rockondon (Jan 18, 2008)

Thanks 
I have a 9815 alpine. That the screen is going out. So i will likely need a replacement headunit soon anyway. 



I have read Geo's thread. Good read.


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## FrankstonCarAudio (Feb 2, 2008)

rockondon said:


> Thanks
> I have a 9815 alpine. That the screen is going out. So i will likely need a replacement headunit soon anyway.
> I have read Geo's thread. Good read.


Outboard processors are the way to achieve a lot more than some h/units can offer, so I guess that will be the direction you will take?

I hope Ge0 does do a tutorial on this, he has spent more time on this than a lot of us that use rear ambience speakers..

Mark


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## ~thematt~ (Sep 14, 2007)

rockondon said:


> Still i would like to have better sound. Like sitting in the audience. Not on stage.


Unfortunately, unless the music was recorded with the microphone in the audience, thats an effect you'll never get. 

The speakers will reproduce everything the microphone picks up, at the point where the microphone picks it up. If your microphone is right in front of the singer, thats where the singer will be in your replay environment.

Sucks, I know.

I'll be using a standard Alpine deck, with AuxIn from my Arc's Aux out, midrange band from my P90. I think I'll have about 15-20m/s available after I've tapped all options, so it should do dandy until the Carputer is built.....


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## FrankstonCarAudio (Feb 2, 2008)

~thematt~ said:


> Unfortunately, unless the music was recorded with the microphone in the audience, thats an effect you'll never get.
> 
> I'll be using a standard Alpine deck, with AuxIn from my Arc's Aux out, midrange band from my P90. I think I'll have about 15-20m/s available after I've tapped all options, so it should do dandy until the Carputer is built.....


That first remark is so true... unfotunately 

Your way to achieve a delayed/bandpassed signal will mean a lot of interconnects! 

All the best and good luck, from another Aussie!
Mark


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## 89grand (Nov 23, 2006)

OK, with just an Alpine PXE-H650 processor, what can I do with that to properly implement rear speakers? It has an output for rears speakers, but the only thing it offers for them is a high pass crossover (50-200hz), no low pass crossover, some eq and time alignment, but that's it. I'm not really looking to buy more equipment, other than a cheap small amp and some cheap speakers.


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## blackwolf (Feb 21, 2008)

89grand said:


> OK, with just an Alpine PXE-H650 processor, what can I do with that to properly implement rear speakers? It has an output for rears speakers, but the only thing it offers for them is a high pass crossover (50-200hz), no low pass crossover, some eq and time alignment, but that's it. I'm not really looking to buy more equipment, other than a cheap small amp and some cheap speakers.


Well..........., I'm certainly not an expert in these matters, but couldn't a passive bandpassed crossover be built to the proper parameters for the rear fill target that we're looking for? In your case, obviously you are committed to using the H650 and are thus saddled with its' limitations, so the aforementioned crossover might be the ticket for your system. I certainly don't know how to build said crossover, but I'm sure there are a few folks around here who could. What do you think?


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## blackwolf (Feb 21, 2008)

Ge0 said:


> I'd be glad to. That and I've been thinking about adding my own "how I tune my system" tutorial seeing how my methods vary from the average guys yet I obtain excellent results.
> 
> Ge0


Great! I'd be interested in both.


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## lunchmoney (Dec 27, 2007)

The word "proper" keeps being used, meaning proper processing, delay etc...

But I think it's safe to say that the OP's stock rear speakers are not benefitting from any processing... and yet he noticed improvement anyways?


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## br85 (May 2, 2008)

I also would like to try this (I could get properly q corrected speakers on axis right behind my rear seats in my wagon on top of my cabin widthed sub-box!). Someone ought to design and market a small processor specifically for this purpose. The only things it would need would be a variable 15-30ms delay setting, and a haffler/mono(true)/ambiophonic mode setting. 

Maybe a bandpass setting too, but most good HU's and/or amps can already do it, or i could just buy a couple mylar caps and aircore inductors for a 6db/8va sloped bandpass filter. Up to the designer I guess.

K someone do it. I'll pay $1000 for a din unit.


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## br85 (May 2, 2008)

Abmolech said:


> http://www.diymobileaudio.com/forum/showthread.php?t=22523
> 
> Possibly most of what needs to be said is in there.
> 
> ...


Why not haffler Dean?


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## durwood (Mar 7, 2007)

br85 said:


> Why not haffler Dean?


It's already mentioned in that thread he linked.


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## thehatedguy (May 4, 2007)

This is a good little thread.


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## blackwolf (Feb 21, 2008)

lunchmoney said:


> The word "proper" keeps being used, meaning proper processing, delay etc...
> 
> But I think it's safe to say that the OP's stock rear speakers *are not benefitting from any processing... and yet he noticed improvement anyways? :confused*:


And my rear speakers are not benefitting from any processing to speak of either, other than some small eq'ing. All that I've done is connected the negative leads of the rears at the eq, thus squashing the center information that these speakers receive. The result improved my stage height and makes for a more pleasing listening experience. As funds and time allow, I'll be trodding down the path that Ge0 has taken (the "proper" path) since I've seen what even the simplest, most basic step can produce.


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## br85 (May 2, 2008)

I might try this out in the next couple of days, with just the maximum 4 metres worth of T/A (which I think is only 11ms or something but i'm sure it's better than none), L-R, R-L wiring and maybe a cheap bandpass circuit.

Is the ideal frequency range 350-5kz? Sorry but I couldn't find it 

Since I am a bit of a wiring noob I'll only be building 1st order passive butterworth bandpasses (Cap and inductor in series), should I do my lowpass/highpass filters well _inside_ that range? (6db per octave is very little attenuation). Maybe 550hz and 2.5kz?


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## durwood (Mar 7, 2007)

rockondon said:


> Also......Mr Abmolech.
> Can you give the link to setting up this ambiophonic setup.
> I googled it and got book sales. Hmmmmm
> 
> ...


Possible cheap way to try a ambiophonics/dipole processor

Creative/Cambridge PS2000 if you can find one on the cheap.

For cheap delay processors, look at pro audio pedal effects or something similar perhaps. On old alpine headunit or similar that has time delay and an aux input.


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## charlo (Jul 8, 2008)

Hi fellas,
I am new to this forum. I like my music but I am from Trinidad in the Caribbean and it's very expensive to buy top equipt due to high duty. But back to the topic, I presently use an Alpine CDA 9887, MRP-F450 ( 70 watts rms @ 4ohms ). I have some decents 6.5 components up front and some Kicker KS-69 in the rear. With the fader at 4-5 up front the music is fantistic ( I dont like subs I prefer some good 6 by 9 in the back). I have been looking at the DLS R1070 (7 by 10 )- 100 W RMS/150W max 30HZ-20,000 VS Boston Acoustics SL95 (6 by 9 )- 60W RMS/200Wmax 35hz - 20,000. Obviously the DLS looks better but has any one used any of these speakers and what's the opinion in Bass performance. Is the difference very noticable.Which of the set the Alpine Amp will perform better. Will the Amp push the R1070 efficiently and will there be ample head room. By the way, the DLS R1070 was rated as the best 6 by 9 (actual size 7 by 10 ) in a British Magazine a few years ago. These speakers are still available but is replaced by the R1073. These speakers carry some huge magnets whereby the Boston SL95 has the neodymium magnet which is very small but suppose to be 10X more powerful as an ordinary magnet its same size.


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## Attack eagle (Nov 18, 2006)

lunchmoney said:


> The word "proper" keeps being used, meaning proper processing, delay etc...
> 
> But I think it's safe to say that the OP's stock rear speakers are not benefitting from any processing... and yet he noticed improvement anyways?


I spent two weeks in a Magnum on vacation... they fire at the rear floor, so they are somewhat bandpassed and very off axis already. (not a terrible setup in a wagon at all!) 

In my 5 series wagon (roof mounted mids roof mounted forward facing tweets) I got tired of the fader needing to be full forward, and disconnected the rear tweeters, leaving the oem bandpassed mids in place. Made a nice difference IMO as well. Still needs to be faded forward to drop the output some but it does sound more open IMO.

Would I run rears in a two seater or a compact sedan? Probably not, and if I did there would be some serious T/A needed. IN a full size wagon or Large SUV with roof mounted Mids? Sure.

I like to hear some sound behind me... I hear it at a concert, on stage, or when listening at home. Kickpanel or door mounted speakers just don;t seem to have any rear ambience in a large wagon or SUV (Shape of car? length? both?) in my experience.


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## AWC (Mar 31, 2008)

I'm very curious of the impact that Imprint will have on rear speakers. When the h-650 was mentioned it piqued my interest as surely Audyssey has done some homework. Why not install the 650 as is front and rear and see how it souds...I guess I could do the same as it is mostly done anyway (re-install rear amp, flick the three-way switch and re-run the set-up) My rear doors have a pair of Zapco Iforce 6.5 + kappa tweeters though they aren't hooked to anything anymore. Does an7yone have any direct experienceusing the rear speakers with Imprint?


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## BadSS (Feb 2, 2008)

I have a 2-door coupe and run 7” Vifas in the rear seat quarters. Where I have the seat set, the rears are higher and closer to my ears than the 8” front door drivers. I’m running two amps off the midrange out – 50 up and 2.5k down going to both amps. I also have Seas textile tweeters front and rear running off one amp 2.5k up, but with the rear tweeters passively attenuated. 

I guess I got lucky, because it sounds great to me with the same tweeter and midrange TA being sent to the front and rear drivers. I can tune in a strong solid raised center stage while retaining very good stereo separation. It doesn’t sound like there are any rear fills with the TA on, yet the center imagery drops and the system is not as full when I cut off the rear drivers. There’s also little to no sound quality lost when you’re turning you head left or right checking for blind spots,, which I hear a void without the rears. Plus, I don’t have to make excuses to the rear seat passengers,,, since it sounds pretty good sitting in the back seat.

Anyway,,, I’m sure I’d have my ears handed to me in a competitive event, and don't know how "proper" it is,,, but I’m happier with them than without and would think others would be if they ever give rear-fills with TA a chance.


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## AWC (Mar 31, 2008)

So how important is it that the rear speakers have a similar sound to the front stage? I went through the trouble of re-routing, splitting, and over-all having just the sweatiest time just to find our that my rear tweeter had fallen out of the mount an is torn. This was the last thing "the installer" had touched so I'm kinda tickled it happened. but still I'm out of a tweeter and if I'm going to use rear-fill I'll need a new one. 

I have morel elates in the front. the rear were a "set" of 6.5" components comprised of a Zapco I-Force 6.5"S, the zapco passive x-over, and former set of infiniti reference tweeters. If the matching of tweeters aren't that big a deal I'll be in the market for new silkies.


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## jbob (Jan 31, 2008)

I have a Magnum as well, but I havn't had time to install anything yet. I will be doing active in the front via a rockford 3sixty.2. I'm considering experimenting using the center channel out to a very small amp to run the stock rears mono. I won't have a difference signal or anything nice likethat of course, but I will have delay, x-over and eq to play with. I guess we'll see what happens when I start installing stuff.


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