# Sound stage pinned to a-pillars



## Orion525iT (Mar 6, 2011)

I tried to look into this, but i could find what i was looking for with a search.

I finally got my car pc in the car. It's not fully installed yet, but it allowed me to run optical out of pc to my mini dsp 2x8. I was playing around with speaker angle and location, and was running into some issues with some songs. 

Midbass are in pods in lower front of door 150-1000hz. Mids are dual aura whispers wired parallel in the kicks 1000-5000hz. Tweets are Dayton Amtpod-4 running 5-20khz. All are 24 db/Oct slopes. I haven't run any sweeps with REW yet. TA was set up with tape measure.

The issue I am having is that the stage seems pinned to the a-pillars at the tweeter location. It doesn't do this with vocals, but only with some instruments on some songs. I am getting good stage height, and when this happens the full range seems to come from the tweeter position. 

Anybody encounter this before? It just might be the way the tracks are mixed, but i am wondering if it is something that will work itself out during tuning? I have tried different tweeter locations like a-pillar and sail panel and tried different angles, and it doesn't seem to change much, the stage just gets pinned to the new location. I have towels around the tweeters to absorb as much reflections as possible.


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## BlackHHR (May 12, 2013)

Yes I have heard this before in cars brought to us to tune. 
Have you tried to eq and adjust for phase related problems? If not dust off the old RTA and get some type of base curve. 
From past experience, out of phase track the vocals are pinned far left and far right. In phase tracks are centered up nice under the rear view mirror. You may be experiencing a phase issue that can be corrected with some tuning. A simple reversing polarity in the processor may correct the affected pair of drivers. 

Greg


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## Orion525iT (Mar 6, 2011)

BlackHHR said:


> Yes I have heard this before in cars brought to us to tune.
> Have you tried to eq and adjust for phase related problems? If not dust off the old RTA and get some type of base curve.
> From past experience, out of phase track the vocals are pinned far left and far right. In phase tracks are centered up nice under the rear view mirror. You may be experiencing a phase issue that can be corrected with some tuning. A simple reversing polarity in the processor may correct the affected pair of drivers.
> 
> Greg


I don't think it is a phase issue. Let me explain again. Vocals, and other instruments that are supposed to be centered are centered (and nicely). Male and female vocals are where they are supposed to be. But other elements are pinned hard to the pillars. I can get a cymbal crash from the right that seems pinned far right and at the same time get an acoustic guitar from the left that is pinned hard to the left a-pillar. In the recordings, I am sure these instruments are intended to be in that location. But it's almost like everything is too condensed to far left and far right.


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## BlackHHR (May 12, 2013)

If you are in the area, come by the shop and lets take a listen. I am always up to sitting back and enjoying some tunes. 
I would like to hear it as it is.


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## kyheng (Jan 31, 2007)

Tweeter should crossed higher, say 10KhZ onward. Let your mid do more work and you will be amazed.
Looks for me is level matching and setting the crossovers problem.


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## mmiller (Mar 7, 2008)

Sounds like a phase issue to me as well. Since you're using the Aura whispers, playing with different X/over points on the drivers might not be a bad idea either.


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## Orion525iT (Mar 6, 2011)

BlackHHR said:


> If you are in the area, come by the shop and lets take a listen. I am always up to sitting back and enjoying some tunes.
> I would like to hear it as it is.


Thanks for the invite. You are pretty far away from me, but at some point it would be nice to get another set of ears on it, especially since some of the system design is a bit out of the norm. So it would be cool to see how it stacks up and i would like to get a less myopic opinion. Really, I have a crap ton more work to do on the car. Futzing with tweeter and mid location/angle should be the final parts to the build. It's just the first time I have had the amps and all the equipment in the car. I still need to get my power supplies for both the 2x8 and the PC, since they are both running off an extension cord routed through a body plug in the trunk.

I'll try to get measurement tonight or tomorrow. I don't have the door panels on right now, and the sub hits are lighting up the doors a bit, so the measurements won't be accurate down low until I get the doors treated. But I think the issue is high frequency. 



kyheng said:


> Tweeter should crossed higher, say 10KhZ onward. Let your mid do more work and you will be amazed.
> Looks for me is level matching and setting the crossovers problem.


I feel I have a lot of wiggle room built into the system. So I will try to run the auras higher. The issue is that they will get into beaming because I am using 2 per side in the kicks. I am also wondering if it is a level matching issue. It might be that the tweeters are a bit hot somewhere in their passband.


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## kyheng (Jan 31, 2007)

Orion525iT said:


> Thanks for the invite. You are pretty far away from me, but at some point it would be nice to get another set of ears on it, especially since some of the system design is a bit out of the norm. So it would be cool to see how it stacks up and i would like to get a less myopic opinion. Really, I have a crap ton more work to do on the car. Futzing with tweeter and mid location/angle should be the final parts to the build. It's just the first time I have had the amps and all the equipment in the car. I still need to get my power supplies for both the 2x8 and the PC, since they are both running off an extension cord routed through a body plug in the trunk.
> 
> I'll try to get measurement tonight or tomorrow. I don't have the door panels on right now, and the sub hits are lighting up the doors a bit, so the measurements won't be accurate down low until I get the doors treated. But I think the issue is high frequency.
> 
> ...


That's the advantage(at the same time disadvantage) of a 3-way front setup. You need to test it out to get the sweet point.


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## Patrick Bateman (Sep 11, 2006)

Can you elaborate on what the problem is?

From what you posted, it sounds like the soundstage is defined by the width of the tweeters.

But this is fairly normal; it's really difficult to get width that's wider than the car, unless you resort to processing, or use some tricks.

And both of those things depend on the same thing; they add energy to the top octaves that not in-phase with the initial wavefront.

You can experiment with this yourself easily; get a system that has a really solid center. Then flip the polarity. The soundstage will sound spacious and undefined.

Another possible thing that you're saying is that the sound is "pinned" to the pillars, IE, *you have a hole in the center.*

If that's the case, well that's stereo for you, it's really hard to get a good center when using a stereo triangle.

One other thing, is that low order slopes definitely sound more "spacious." Here's why this happens:

When you have low order slopes, you have two speakers covering the same range. For instance, if you have a midrange playing from 80hz to 2000hz, and a tweeter playing from 2000hz to 20khz, *there's a few octaves that both are covering.*

And in those octaves, you're going to hear sound radiating from both sources. So you'll end up with some octaves sounding particularly "spacious" because you literally are hearing the same sound coming from two seperate points in space.

This is A Very Bad Thing because it means that the stereo image is going to vary from octave to octave.

There are two ways to fix this problem:

1) Put the drivers very very close together. If you can put the drivers within one quarter wavelength, they'll basically act like a single unit. This is challenging to do; with a 2khz xover point you'd be looking at a center-to-center spacing of 4.25cm, or less than 2"!

2) Another option is to put them exactly one wavelength apart. This is a lot easier to do, and this is what most loudspeakers do. The problem with putting them one wavelength apart is that it creates an interference pattern off-axis. And since we listen off-axis in a car, it's an iffy solution.

3) the last solution is the one that most people do, which is to use steep slopes. Steep slopes work, but they also reduce the 'spaciousness' that you get with low order slopes, and steep slopes ring like ****. I personally believe that the latter problem is why Siegried Linkwitz invented the 4th order LR slope, but doesn't actually use it in his own loudspeakers. (He used to.)


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## Elgrosso (Jun 15, 2013)

Sub! I'm curious to learn here.
I had kind of the same issue before but a bit different, wide stage and anchored center, but everything in between center and pillars was sometime too much "steered" to the pillars. Just not distributed equally.


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## oabeieo (Feb 22, 2015)

I would start a slope downwards from about 1k to 20 k about 3db per oactave so by time you get to 20k the tweets are about -10db plus or minus, it's a tuning thing for sure if your stuck on using that tweeter location , the speaker location will only get at its best and so go after the best result that location can provide 
Let the mid be a dominant sound, if you like lots of sparkle try using a diffrent location , a pillar has so much reflection going on you are probably hearing multiple reflections as well, I would use a dash mat and turn down tweets 
Get the tweets turned down and the mid to blend with a lowered tweet and it will sound better and also make singer sound farther away


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## Orion525iT (Mar 6, 2011)

^ In the vocals, or center instruments there is good focus and center with some spaciousness. Center vocals and instruments "appear" about the size of a softball or slightly larger.

Instruments panned hard left and hard right are squashed Into a golf ball sized sliver, slightly taller than wide right at the tweeter location near the pillar. The sound is very concentrated and bright. Though bass frequencies seem wide with good ambience, higher frequencies stop dead at the pillar. Again, it is very apparent with acoustic guitar that is panned hard.

I guess you can say there is a bit off a hole in the center.

I'll try to draw a picture to help visualize if it still unclear.


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## oabeieo (Feb 22, 2015)

Maybe just try a dash mat before you do anything extra


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## sqnut (Dec 24, 2009)

The issue is too much delay between L&R side.

Listen to the tweeters only. Do they pull to the sides? To reduce the delay between them either add delay on the left and reduce on right in equal steps, or vice versa till the image snaps to the centre. Then repeat playing only the mids.


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## SkizeR (Apr 19, 2011)

sqnut said:


> The issue is too much delay between L&R side.
> 
> Listen to the tweeters only. Do they pull to the sides? To reduce the delay between them either add delay on the left and reduce on right in equal steps till the image snaps to the centre. Then repeat playing only the mids.


im going to try this for mine. i have this problem but not as bad as the op says his is. mine is somewhat subtle


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## oabeieo (Feb 22, 2015)

Orion525iT said:


> ^ In the vocals, or center instruments there is good focus and center with some spaciousness. Center vocals and instruments "appear" about the size of a softball or slightly larger.
> 
> Instruments panned hard left and hard right are squashed Into a golf ball sized sliver, slightly taller than wide right at the tweeter location near the pillar. The sound is very concentrated and bright. Though bass frequencies seem wide with good ambience, higher frequencies stop dead at the pillar. Again, it is very apparent with acoustic guitar that is panned hard.
> 
> ...


Yeah I get what your saying, so your tweets are in the a pillars correct? If so I still think it's a tuning thing either delays are wrong and tweets are too loud and reflections, I have played with delays on tweeters a lot and the tape measure trick doesn't always work so well because it's so hard to hear delay working with a tweeter, I would start with no delay between them and pad the dash with a towel and use some test tracks to add delay and listen for it, you may be delaying a reflection that is where your taking special cues from , or not , you might try running the tweeter down to 1.5k on very very low low low power and set your delays that way so you can actually hear it center up , but I'm still convinced your tweeter is up too high and there's some tuning problems with the mid, also if you have a door mid and a pillar tweet you will want that tweet turned down a lot, I bet female "s" es go right to a pillar ,


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## oabeieo (Feb 22, 2015)

Me ght also want to turn down left side about 2db more than right on a compact car and up to 8 db on wide full size truck ,


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## Patrick Bateman (Sep 11, 2006)

Orion525iT said:


> ^ In the vocals, or center instruments there is good focus and center with some spaciousness. Center vocals and instruments "appear" about the size of a softball or slightly larger.
> 
> Instruments panned hard left and hard right are squashed Into a golf ball sized sliver, slightly taller than wide right at the tweeter location near the pillar. The sound is very concentrated and bright. Though bass frequencies seem wide with good ambience, higher frequencies stop dead at the pillar. Again, it is very apparent with acoustic guitar that is panned hard.
> 
> ...


In three octaves, you have sound radiating from two sources:
The midbasses and the midranges. 

This is because you have a three octave overlap between the two drivers. 

And then at high frequency, you don't have this overlap. 

Let's take a second and think about how we locate sounds:

Below 1khz, it's phase. 
Above 1khz, it's amplitude.

Now think about this:

What will happen if you have two sources playing the same thing below 1khz?

The answer is: your brain will perceive that there's two sources. IE, it will sound "spacious"

This is what you are experiencing in your car. In the midrange you're hearing "spaciousness" because there's multiple sources. But as you go higher in frequency it sounds smaller. Because it is. (There's only one source.)


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## SkizeR (Apr 19, 2011)

Patrick Bateman said:


> In three octaves, you have sound radiating from two sources:
> The midbasses and the midranges.
> 
> This is because you have a three octave overlap between the two drivers.
> ...


at what slope? or what if you space out the crossovers? i find that most people do this, and honestly its worked damn well for me so far. i have my midbass at 200hz @ -18db (or possibly -12, i forget right now), and midrange at 250 @ -12db


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## ErinH (Feb 14, 2007)

What's the width like with the tweeters off?


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## sqnut (Dec 24, 2009)

In a car if you want tonality and imaging, steep slopes work better. At 1/3 oct we dont have enough eq power to make 6 or 12 db slopes work. 24 db slopes typically means the overlap zone in real terms is just about an octave ~800-1500. To keep the sound stable in this range and not have the sound pull towards your speakers or smear around, you need both timing and L/R response to match. 

The over lap zone between mid and tweet is about 3.5-6khz and in this zone L/R balance is more important, but timing still counts. If you listen to the tweeters with the timing between L&R out of whack, you will never get the tweeters to center under your rear view. They will always be skewed left or right, or like in the op's case pull to the sides.


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> at what slope? or what if you space out the crossovers? i find that most people do this, and honestly its worked damn well for me so far. i have my midbass at 200hz @ -18db (or possibly -12, i forget right now), and midrange at 250 @ -12db


I'm a moron I misread OP.

I thought he had the midbasses in the door and the auras in the kicks playing at the same time, from 150hz to 1khz.

Never mind.


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> In a car if you want tonality and imaging, steep slopes work better. At 1/3 oct we dont have enough eq power to make 6 or 12 db slopes work. 24 db slopes typically means the overlap zone in real terms is just about an octave ~800-1500. To keep the sound stable in this range and not have the sound pull towards your speakers or smear around, you need both timing and L/R response to match.
> 
> The over lap zone between mid and tweet is about 3.5-6khz and in this zone L/R balance is more important, but timing still counts. If you listen to the tweeters with the timing between L&R out of whack, you will never get the tweeters to center under your rear view. They will always be skewed left or right, or like in the op's case pull to the sides.


Tonality has little to do with slopes, and steep slopes wreck your phase response.

Even the inventor of the LR24 slope doesn't use it.

Steep slopes are great if you have two loudspeakers separated by more than one wavelength at the xover point. Steep slopes are a band aid that fixes the off-axis problems that occur when you have two drivers spaced more than one WL apart.

But they come with a bevy of problem, particularly because they introduce a 360 degree phase shift at the xover point. That's a massive delay, and it varies with phase, so you can't fix it with a miniDSP. (You *can* fix it with rephase, which is why rephase is so cool.)

If you're in love with high order slopes, check out LeCleach's solution, it's does far less damage to the phase response.


BTW, if you don't care about phase, ignore everything I said. But keep in mind that phase is literally how we detect the location of sounds below 1khz.


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## SkizeR (Apr 19, 2011)

Patrick Bateman said:


> Tonality has little to do with slopes, and steep slopes wreck your phase response.
> 
> Even the inventor of the LR24 slope doesn't use it.
> 
> ...


so the phase shift at crossovers is due to timing? or it just shifts phase? both?


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> so the phase shift at crossovers is due to timing? or it just shifts phase? both?


All crossovers introduce a phase shift at the xover point.

The reason that first order slopes are in-phase is because the delay of the first order low pass is complementary to the delay of the first order high pass.

All of the slopes higher than first order introduce a commensurately higher delay, and the delay is frequency dependent.

The higher the slope, the more the delay.

If you've ever listened to a nice stereo, and it had that "sterile" hifi sound, where it's clean but there's no ambience or imaging, you're hearing the sound of high order slopes.

I really hate them; I think they're possibly the number one reason that so many expensive stereos sound lifeless. On the converse, I think the lack of xovers is the reason that full-range speakers frequently are more involving than two-ways or three ways. It's not some magic unobtanium in the drivers; it's a lack of a xover in the midrange.

I am currently using high order slopes in my "main" system, the one I listen to all day. To avoid the sonic wreckage of high order slopes, I used 8th order. Basically my reasoning is that high orders suck, but if I'm going to use them I'll limit the suckiness to a very narrow band of sound. (An 8th order slope reduces the output by 48db in one octave; so hopefully all the nasty artifacts are "confined" to a fraction of an octave.)

All of this is complicated by the fact that the phase response is a combination of the filter's phase and the naturall rolloff of the driver. IE, if you're driver is already falling off at 12dB/octave, a 2nd order slope will yield a 4th order rolloff, with all of the phase issues that entails.


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## SkizeR (Apr 19, 2011)

I know that theres phase shift at the crossovers. i just didnt know if it was from delay at the crossover point, or just a random phase shift


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> I know that theres phase shift at the crossovers. i just didnt know if it was from delay at the crossover point, or just a random phase shift


Basically you start with a first order slope. *If your mid and your tweet are first order, you have symmetry, and you wind up with zero delay.*

Now increase the slope, and each order creates more delay.

If you've ever felt like your tweeters seem "disconnected" from everything else, that's what you're hearing.

You can see the disconnect really easy in a phase measurement; at the xover the phase just goes nuts.

An optical analogy might be the focus on a picture; if you're focus isn't right, only part of the image is in focus. The rest is blurred.


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## Orion525iT (Mar 6, 2011)

I want to try a few different things tonight with the most offending tracks. But it's been raining, so that may prevent me from getting too far.

I will say that I have been a pretty big advocate for kick panel only installs. It's worked well for me, and everything sounds more cohesive out of the box. But, in this car, everything staged too low when I tried it. So, I moved the tweets up to the pillars, and stage height was much improved. I tried the auras up there too, but this car has no room. Tiny dash, tiny pillars, tiny sail panel. 

As far as the current situation. The surrounding area of the tweeters is well covered with towels. I even covered part of the lower windshield and the door glass near the sails. It actually made things worse in a way. Without the towels, the stage issues I have at the pillars was less pronounced and more diffuse. But it sounded gross and busy (as expected).

I need to take another listen because I feel I am running too much off of memory right now. I'll also try to get the mic up and running for a few measurements. The issue is that the car pc is headless, so I will be running the minidsp plugin and REW through Chrome Remote Desktop on my phone (it's a bit tedious, but it works).


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## Orion525iT (Mar 6, 2011)

Patrick Bateman said:


> That's a massive delay, and it varies with phase, so you can't fix it with a miniDSP. (You *can* fix it with rephase, which is why rephase is so cool.)


Getting a bit OT, but I need look into that. I don't know anything about it, but having a car PC adds even more flexibility than the minidsp by itself. I assume there is a trade off? There is always a trade off. 





Patrick Bateman said:


> BTW, if you don't care about phase, ignore everything I said. But keep in mind that phase is literally how we detect the location of sounds below 1khz.


More OT, but this is part of the reason why my midbass run from 150-1000hz, which is a rather odd bandpass.


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## ErinH (Feb 14, 2007)

if you find yourself in the Decatur, AL area, give me a shout.


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## Orion525iT (Mar 6, 2011)

ErinH said:


> if you find yourself in the Decatur, AL area, give me a shout.


Will do

I didn't do any RTA tonight. I kept all my TA settings the same based on tape measure. No alterations to slopes.

I listened for a bit without changing anything to remind myself of the issues. I then disconnected the tweeters. The result was slightly lower stage but mostly rainbowing and obvious lack of upper frequencies. After listening to that over a few tracks, I removed the low pass on aura arrays (arranged horizontally and toed inward). There was still edges to the stage at about the a-pillar, but the rainbow effect limited that hard boundary to a few notes on some songs. I then attenuated everything the same amount except for the auras (tweeters still disconnected), and the rainbow angle decreased somewhat. 

I then added back the low pass on the auras, but raised it to 7000hz. I added back the tweeters attenuated the same amount as the midbass and subs, and ran the tweeters from 7k-20K.

End result; The hard edge at the pillars is gone with more space and ambiance. I made the mistake of making two changes at once in that I changed the mid to tweeter xover and also attenuated the tweeter at the same time, so I don't know for sure what made the difference, but I am 90% certain it was mostly a level mismatch. I still have more issues though, of course. The stage is now pulled to the left (drivers side) and I can detect a little warbling between the tweeter and auras, but the hard edge is gone.


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## sqnut (Dec 24, 2009)

Here we go again



Patrick Bateman said:


> Tonality has little to do with slopes, and steep slopes wreck your phase response.




I mentioned tonality and imaging. Steep slopes have _everything_ to do with imaging. In a car phase is little more than timing and using matching slopes, thanks to all the reflections and the fact that speakers are mounted at different heights. Even if you get the timing right the phase angles will never match with drivers at different heights and axis, unless you put all the drivers next to each other, not very practical in a car. Getting fixated with phase is a car is a waste of time imho, ymmv. 



Patrick Bateman said:


> Even the inventor of the LR24 slope doesn't use it.




Remember he is making speakers for a totally different room..........



Patrick Bateman said:


> Steep slopes are great if you have two loudspeakers separated by more than one wavelength at the xover point. Steep slopes are a band aid that fixes the off-axis problems that occur when you have two drivers spaced more than one WL apart.




Agree 100%, but hey we're talking about listening in a sardine can. Compromises and band aids are a way of life here. Rules of what works in a car and a room are different. I keep going back to the Magic Bus, please explain how the 4th order slopes in the bus negatively affects the sound?



Patrick Bateman said:


> But they come with a bevy of problem, particularly because they introduce a 360 degree phase shift at the xover point. That's a massive delay, and it varies with phase, so you can't fix it with a miniDSP. (You *can* fix it with rephase, which is why rephase is so cool.)




As long as you're keeping matching slopes both LP and HP driver will have a 360 degree shift. One leads and the other lags but the net effect is 0.





Patrick Bateman said:


> BTW, if you don't care about phase, ignore everything I said. But keep in mind that phase is literally how we detect the location of sounds below 1khz.


Phase or locating sound is down to timing and the angle of the wave. In a car while you can control the timing of the direct sound you have no control on that of the reflected sound. In a car 90% of what we hear is reflected energy. The phase has already gone for a toss. Drivers at different heights and angles further compound the problem.


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## Patrick Bateman (Sep 11, 2006)

"Fourth-order Linkwitz–Riley crossovers (LR4) are probably today's most commonly used type of audio crossover. They are constructed by cascading two 2nd-order Butterworth filters. Their steepness is 24 dB/octave (80 dB/decade). The phase difference amounts to 360°, i.e. *the two drives appear in phase, albeit with a full period time delay for the low-pass section.*

^^

Let me translate that into English. A LR4 crossover delays the signal one wavelength at the xover point.

Go and do some phase measurements and you'll see. 

It's impossible to get two drivers in phase with a LR4. (Unless you use rephase.)

If your speakers are far apart, fixing the phase is impossible anyways. 

But if they're close; like mine usually are; it's very doable. 

Phase is literally how we perceive the location of sound below 1khz. That's why LR4 speakers have that "HiFi" sound. 

A lot of people haven't heard a speaker that can really image. As I've argued numerous times on here, I'm not even a big fan of imaging, because my recordings suck. You're not going to hear an accurate soundstage unless you use good recordings.

TLDR: below 1khz, phase is how we localize sound. The most popular xover filter wrecks the phase at the xover point. IMHO, this is why most stereos sound sterile and HiFi.


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## Patrick Bateman (Sep 11, 2006)

Oh, as far as "directed vs reflected", well duh 

Why do you think I use synergy horns with first order slopes?

Fixes every issue I mentioned.


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## oabeieo (Feb 22, 2015)

sqnut said:


> In a car if you want tonality and imaging, steep slopes work better. At 1/3 oct we dont have enough eq power to make 6 or 12 db slopes work. 24 db slopes typically means the overlap zone in real terms is just about an octave ~800-1500. To keep the sound stable in this range and not have the sound pull towards your speakers or smear around, you need both timing and L/R response to match.
> 
> The over lap zone between mid and tweet is about 3.5-6khz and in this zone L/R balance is more important, but timing still counts. If you listen to the tweeters with the timing between L&R out of whack, you will never get the tweeters to center under your rear view. They will always be skewed left or right, or like in the op's case pull to the sides.


I didn't know this about shallow slopes , do you care to elaborate I am curious on this because I am using 6db slopes every chance I can with better results on imaging than 18 or higher , how does power play into this , maybe I have enough to power but I can get the center to work way easier with 6db . I am thinking its a phase thing at cutoff , do you have a link to share on this or can u explain how. Thanks


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> TLDR: below 1khz, phase is how we localize sound. The most popular xover filter wrecks the phase at the xover point. IMHO, this is why most stereos sound sterile and HiFi.


I agree 100% maybe it's just my car is suck for get phase correct which could be the case because it was one of the harder ones for me to get right , but I do have horrible problems with relative phase track with 24db slopes I go to 6db and the track goes center and out of phase goes far left and right EVENLY , I think getting it center is only half the feat. Getting out of phase conditions for a stereo image can be equally as important, tonality and evenness between left and right. When I hear a out of phase part in a track mostly backup vocals or whatnot and instead of going far left and right it goes off more to one side or is uneven it bugs me just as much as not having the center defined or having it diffuse .


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## sqnut (Dec 24, 2009)

oabeieo said:


> I agree 100% maybe it's just my car is suck for get phase correct which could be the case because it was one of the harder ones for me to get right , but I do have horrible problems with relative phase track with 24db slopes I go to 6db and the track goes center and out of phase goes far left and right EVENLY , I think getting it center is only half the feat. Getting out of phase conditions for a stereo image can be equally as important, tonality and evenness between left and right. *When I hear a out of phase part in a track mostly backup vocals or whatnot and instead of going far left and right it goes off more to one side or is uneven it bugs me just as much as not having the center defined or having it diffuse .*


Ok, what does out of phase sound like? What do you mean by the bolded portion? How can a part of the track be in phase and the other out of phase unless it's recorded that way.


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## SkizeR (Apr 19, 2011)

sqnut said:


> Ok, what does out of phase sound like? What do you mean by the bolded portion? How can a part of the track be in phase and the other out of phase unless it's recorded that way.


i dont think "out of phase" would be the correct term for what hes trying to say.


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> Ok, what does out of phase sound like? What do you mean by the bolded portion? How can a part of the track be in phase and the other out of phase unless it's recorded that way.


I think that what he's saying is that when he flips the polarity on the speakers (putting them out of phase) the image doesn't go out-of-phase like it's supposed to.

This is a common problem in car stereo; ideally a mono signal should be centered on the dash, and an out-of-phase signal should be diffuse, but frequently we wind up with something in-between with BOTH settings.

IE, no matter if polarity is in-phase or out-of-phase, the sound is somewhat out-of-phase.

The reason that this happens is due to pathlength. For instance, 500hz is .68meters long. If you were *absolutely* equidistant between two loudspeakers playing 500hz, and the signal was in-phase, you would hear a phantom image between the loudspeakers.

But due to the fact that we're NOT equidistant between the loudspeakers, you wind up with an image that's neither diffuse nor solid. This is due to the pathlength difference.

That's why people use DSP delay to fix this. The pathlengths are still wrong, but delay can fix it so the signal arrives at the same time.

And all of this is complicated by the xover used, because xovers introduce a phase shift.

Does your head hurt yet lol?

It took me a while to wrap my brain around this stuff.


By the way, the math should make it obvious why phase isn't relevant at high frequency. For instance, at 2khz a 90 degree phase shift takes just 4.25cm (less than 2".) So you can see that phase shift at high frequency isn't a big deal; if it was the sound would change when you moved your head a fraction of an inch.

Where phase becomes an issue is below 1khz, and IMHO it's particularly important in the two octaves between 250hz and 1khz. That's because those two octaves are in the 'sweet spot' where the wavelengths are long enough for us to perceive a phase shift, but not so long that they're bigger than the "room" itself. (100hz is longer than the width of the car itself.)

If you want to play around with this, get some cheap computer speakers and hook them up to your car stereo. Now try putting them in various locations, and notice how audible it is if you shift the location a few inches. You may be surprised to find that cheap computer speakers image better than two-way speakers. This is because cheap computer speakers have a single sealed woofer, and sealed boxes without xovers have near-perfect phase response. Personally, I keep a pair of Cambridge Soundworks satellites around for this type of experimentation. You can find them on CL for cheap. Logitech speakers would probably be ok too, as long as they're sealed and there's no tweeter.


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## oabeieo (Feb 22, 2015)

sqnut said:


> Ok, what does out of phase sound like? What do you mean by the bolded portion? How can a part of the track be in phase and the other out of phase unless it's recorded that way.


When it's recorded that way , like backup vocals are often out of phase in the mix , or other sounds but most noticeably vocals , like some recordings have the main singer In phase and backup singers or other parts of music out of phase 

You have A way to listen to music on your phone on your system you tube 
" Mary chapin carpenter come on come on" listen to that track you will hear her voice is center and backup vocals are out of phase to appear like they are panned left and right simultaneously, it's a recording trick , not all music uses vocals to do this some use simple panning but some use phase to get the image ,

It's easy to tell which ones do it if you know what to look for, they could mix down another left or right and copy it to the feed but polarity reversal does the job


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> I think that what he's saying is that when he flips the polarity on the speakers (putting them out of phase) the image doesn't go out-of-phase like it's supposed to.
> 
> This is a common problem in car stereo; ideally a mono signal should be centered on the dash, and an out-of-phase signal should be diffuse, but frequently we wind up with something in-between with BOTH settings.
> 
> ...



No but I have heard that as well , lol . Like track 3 on IASCA, shows in phase and out of phase , well music has in phase information and out of phase information, I was referring to the out of phase Information, we focus so hard on getting a center image and loose focus of other phase conditions that make music sound good not what a rta reads or a impulse response, like getting a nice rta curve is great but if the combined left and right sound makes the phantom image sound not sound good I find it problematic. I like the sound I preceive as a phantom image to have good tonality, and so I want out of phase sounds to sound good as well, it's a balance , ok I'm confused myself now, but phase is tricky little devil, getting a center is hard enough let alone other phase issues in a car with reflection , I was just saying I have the best results with 6db slopes getting in phase or relative polarity in phase ( solid center) and out of phase ( outer boundarys of stage) to sound right relative to the listening position. 

Sometimes I say In phase as mono L+R

I think some recording engineers use out of phase mono on background singers and diffrent sounds may because you can have amplitude high and make it sound farther away than a panned left and right which would sound more forward, and maybe some effects on top of it sure,


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## oabeieo (Feb 22, 2015)

SkizeR said:


> i dont think "out of phase" would be the correct term for what hes trying to say.


Yes my terminology is not well defined , 
When I say in phase I mean L+R mono 
And out of phase L+R mono with reversed polarity both sides


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## oabeieo (Feb 22, 2015)

This post tells a lot of what I'm sayin there a post by Robb in post #13 that's very good at explaining it . Check it out 

https://www.gearslutz.com/board/rap...on/79556-bad-use-reverse-polarity-effect.html

He talks about using out of phase mono and adding a delay or some other effect , and he says in the right environment it's cool but in the wrong environment, one side seems louder. And I agree , if I listen to IASCA track 3 and when she says " my voice is now out of phase and should sound diffuse and be difficult to locate and may loose low frequency responce" ; listen to how it sounds in your car, it's a mono mix with out of phase left and right . You will see her voice does not sound evenly diffused , so my point , some music has some of that out of phase information mixed down , and in a car when I hear it it can sound lopsided , and with steep slopes as Patrick points out in the mid and low mid it worsens, i believe my system sounds better when I have a strong center , and a articulate left and right in and out of phase. And 6db slopes work so much better!!! If I was strictly worried about a phantom center well I believe the sterile sound comes into play because depth is not maximized because stage depth is so phase dependent .


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## sqnut (Dec 24, 2009)

When the timing and L/R balance is right, the in phase voice should be from a golf ball size area under the rear view. The out of phase should image slap bang at the speakers on the L&R. It's the same with these in phase / out of phase tracks on all tuning disks.


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## SkizeR (Apr 19, 2011)

so the real question is, why arent most dsp's equip with FIR filters? dont they have no phase shift ?


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## oabeieo (Feb 22, 2015)

sqnut said:


> When the timing and L/R balance is right, the in phase voice should be from a golf ball size area under the rear view. The out of phase should image slap bang at the speakers on the L&R. It's the same with these in phase / out of phase tracks on all tuning disks.


Should be at speakers yes! Unless TA is not set correctly or having some other phase issues or 4ways and so many arrival times and reflections , and like OP was saying could get vocals right but the tweetes are not right, with a 6 tweets it's a lot easier and achieve able but some of these systems it's off to one side more than other , . But to get back on track the OP was having issues with his tweeters and I still believe it's phase or timing related but more importantly because it's short wavelengths amplitude related ,

And I like my vocal center to be much further forward than under mirror , I shoot for center at dash line next to windshield. And yes on golf ball , I want to know where singers lips are , not just a big diffused center that's all over them middle , But that's a whole different can of worms ,


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## oabeieo (Feb 22, 2015)

SkizeR said:


> so the real question is, why arent most dsp's equip with FIR filters? dont they have no phase shift ?


Phase shift honestly does almost nothing , well nothing beneficial, unless you could correct phase at roll off only well I don't know if there is such thing , I'm sure there is in some of the fancy stuff but I have yet to play with that sort of feature.


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## SkizeR (Apr 19, 2011)

oabeieo said:


> Phase shift honestly does almost nothing , well nothing beneficial, unless you could correct phase at roll off only well I don't know if there is such thing , I'm sure there is in some of the fancy stuff but I have yet to play with that sort of feature.


FIR filters..


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## oabeieo (Feb 22, 2015)

SkizeR said:


> FIR filters..


Hmmmmmm , I need to try these out in my next dsp , who uses them ?


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## SkizeR (Apr 19, 2011)

oabeieo said:


> Hmmmmmm , I need to try these out in my next dsp , who uses them ?


i dont think anyone. i heard minidsp has something for them or with them, but i didnt look into it


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## SkizeR (Apr 19, 2011)

FIR Filter Properties | dspGuru.com


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## seafish (Aug 1, 2012)

oabeieo said:


> Hmmmmmm , I need to try these out in my next dsp , who uses them ?


The Clarion DRZ9255 HU uses them for its DSP…another reason I chose to use it in my upcoming build.


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## oabeieo (Feb 22, 2015)

sqnut said:


> When the timing and L/R balance is right, the in phase voice should be from a golf ball size area under the rear view. The out of phase should image slap bang at the speakers on the L&R. It's the same with these in phase / out of phase tracks on all tuning disks.


I like to use many noise tracks when setting eqs normal stereo pink , mono pink , filtered pink , out of phase pink , mostly just stereo pink , but I do have uses for other noises when setting eq and ta, as well as sweeps and tones in phase and out of phase , I will actually tweak drivers position by inches in direction until I get that location optimized , I have plates in my doors now that shim the speakers torward the footwell about 10deg and up about 10deg . It cuts down reflections on console and reinforces phase at the pass band of that driver, I am planning a new pod build to get the dash speakers to fire straight forward to cut down cross talk and windshield reflections, to get a deeper stage , it's all fun and my system has fantastic stage now but I'm never satisfied completely.


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## sqnut (Dec 24, 2009)

Phase coherence in a car is an oxymoron whichever way you dice it. Angling woofers to avoid reflections doesn't do much cause the wavelengths are too long. Worrying about angling mid ranges and tweeters to reduce reflections or for a better response, is again a bit of a waste of time in the big picture. Just keep the speakers in their omni directional range and you are done. The only speaker I would worry about angling would be a 2" wide bander if I was running without a tweeter. A dashmat is simpler to implement and is better at reducing reflections of the higher frequencies, than angling your tweeter. 

Patrick mentioned he is not fussy about imaging, but if you listen to a lot of well recorded music with imaging cues then a 6db slope on your drivers will not give you a realistic mouth _ever_ no matter what you do with timing and response. Lastly on this Holy Grail of phase coherence, no one has really managed to explain what out of phase speakers sound like. What's the point of splitting hairs on a theory if you can't explain how it sounds?


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> Phase coherence in a car is an oxymoron whichever way you dice it.


This is generally how most people deal with the issue.
In audio, particularly car audio, most people say "I don't care about phase and I'm not going to try and address it."









My favorite example of the phase phenomenon is the JBL Control Now. I own four of these. For the money, they're spectacular, as good as speakers at two or three times the cost.

*But there's absolutely no soundstage with these speakers.*

And here's my "hunch" on why this is:
Due to the "tilt" of the Control Now, the upper midbass is about 10cm behind the lower midbass.

Due to this 10cm gap, *the wavefront of the two midbasses arrives out-of-sync, and they always will.* There is absolutely no way to get those drivers in sync, short of mounting them like the speaker in the bottom left here:










I hope that explanation makes sense. I think that people see home speakers where the baffle is carefully tilted, and they think that it was done for aesthetics. It wasn't; *there is a specific distance required to get the tweeter and the woofer in phase at the xover point.* For instance, with a 2khz xover point, a pathlength shift of just 4.25cm (1.67") will make a noticeable change in phase. Isn't that mind-blowing? *A shift of 1.67" makes a difference.*

In car audio, people tend to ignore phase, and simply put the loudspeakers where they'll fit.



sqnut said:


> Angling woofers to avoid reflections doesn't do much cause the wavelengths are too long. Worrying about angling mid ranges and tweeters to reduce reflections or for a better response, is again a bit of a waste of time in the big picture. Just keep the speakers in their omni directional range and you are done.


I don't spend much time worrying about angle. I *do* spend a lot of time worry about pathlengths.



sqnut said:


> The only speaker I would worry about angling would be a 2" wide bander if I was running without a tweeter. A dashmat is simpler to implement and is better at reducing reflections of the higher frequencies, than angling your tweeter.
> 
> Patrick mentioned he is not fussy about imaging, but if you listen to a lot of well recorded music with imaging cues then a 6db slope on your drivers will not give you a realistic mouth _ever_ no matter what you do with timing and response. Lastly on this Holy Grail of phase coherence, no one has really managed to explain what out of phase speakers sound like. What's the point of splitting hairs on a theory if you can't explain how it sounds?


If you have everything dialed in, a system in phase produces a solid center above the dash. When you flip the phase, the sound is diffuse. In car audio, due to pathlength problems, many cars can't meet that criteria.

It's true that a lot of this is academic, and I've started to move away from getting everything in-phase, because my recordings suck.


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## oabeieo (Feb 22, 2015)

sqnut said:


> Phase coherence in a car is an oxymoron whichever way you dice it. Angling woofers to avoid reflections doesn't do much cause the wavelengths are too long. Worrying about angling mid ranges and tweeters to reduce reflections or for a better response, is again a bit of a waste of time in the big picture. Just keep the speakers in their omni directional range and you are done. The only speaker I would worry about angling would be a 2" wide bander if I was running without a tweeter. A dashmat is simpler to implement and is better at reducing reflections of the higher frequencies, than angling your tweeter.
> 
> Patrick mentioned he is not fussy about imaging, but if you listen to a lot of well recorded music with imaging cues then a 6db slope on your drivers will not give you a realistic mouth _ever_ no matter what you do with timing and response. Lastly on this Holy Grail of phase coherence, no one has really managed to explain what out of phase speakers sound like. What's the point of splitting hairs on a theory if you can't explain how it sounds?


I don't spend allot of time angling , but I am silly tho , and I have tryed it just out of sheer curiosity and have had some good benefit but it's so minuscule, eeh , like I said earlier it's just for fun ,

I can hear out of phase sounds but I also mix tracks for fun and I'm not a expert but I do enjoy trying to have fun with it . I guess I was just conversing for fun and spinning my wheels a bit there sorry


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## sqnut (Dec 24, 2009)

Patrick Bateman said:


> This is generally how most people deal with the issue.
> In audio, particularly car audio, most people say "I don't care about phase and I'm not going to try and address it."




No it's not like that. For me phase has two components timing and the angle at which the sound hits your ears. In a car you have control over the first but thanks to reflections and speakers at different distances and heights the angles on the direct sound will always be different. One can't do anything about the other. Is this something that is audible once you have dialed in the timing and response? Imho, no it isn't.

When we talk about using phase to locate sound we are talking about three things our ability to tell left from right, front from back and higher or lower. Front to back and left to right is about 70hz and up, while higher lower is ~800 and up. 

Now when we split the signal across two drivers, even if we time the drivers properly, the delta change in phase angles will be different. This difference is handled either by spreading it gradually over a wide area via shallow slopes or over a narrow range aka steep slopes. The moot question is which is more audible and I think this is where we differ. I'm sure you love the Dyn home speakers.

For me phase in a car is correct timing and running matching xover and slopes between LP and HP for a combined phase shift of 0. At the end of the the combined effect is what we're hearing. We are not hearing the phase shift of individual drivers because we're listening to two drivers.

In a car I know I have phase issues if:



sqnut said:


> - The sound pulls towards the drivers. If I can't locate the drivers based on what I'm hearing or if I can look at a driver not 'feel/hear' the sound from it, I know I don't need to worry about phase.
> 
> - I know I have phase issues if the vocals sound stretched and no amount of eq helps.
> 
> ...





Patrick Bateman said:


> *there is a specific distance required to get the tweeter and the woofer in phase at the xover point.* For instance, with a 2khz xover point, a pathlength shift of just 4.25cm (1.67") will make a noticeable change in phase. Isn't that mind-blowing? *A shift of 1.67" makes a difference.*




Agree which is why timing on your drivers is so important and why measured distances are only a starting point. You have to tweak from there, the phase difference of a 0.02 ms change on timing on your mids and tweets is very audible in the response. 



Patrick Bateman said:


> If you have everything dialed in, a system in phase produces a solid center above the dash. When you flip the phase, the sound is diffuse. In car audio, due to pathlength problems, many cars can't meet that criteria.


Agree, which is also why parts of music recorded out of phase will pull towards at speaker. Sometimes engineers do this while recording.


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## sqnut (Dec 24, 2009)

oabeieo said:


> I don't spend allot of time angling , but I am silly tho , and I have tryed it just out of sheer curiosity and have had some good benefit but it's so minuscule, eeh , like I said earlier it's just for fun ,
> 
> I can hear out of phase sounds but I also mix tracks for fun and I'm not a expert but I do enjoy trying to have fun with it . I guess I was just conversing for fun and spinning my wheels a bit there sorry


It's all good my post was more general in nature


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> No it's not like that. For me phase has two components timing and the angle at which the sound hits your ears. In a car you have control over the first but thanks to reflections and speakers at different distances and heights the angles on the direct sound will always be different. One can't do anything about the other. Is this something that is audible once you have dialed in the timing and response? Imho, no it isn't.












Phase isn't that complex.

When you have two loudspeakers in phase, both loudspeakers are playing the same waveform at the same time.

*That's all there is to it.*

Filters like the LR4 can obscure the phase issue, because they're a full wavelength out of sync. IE, you can get flat amplitude response with a LR4 filter because both of the speakers are playing at the same point in that wave, *but one wave is delayed an entire wavelength.*

Does that make sense? We get the flat response that we want, but the phase response is borked because it's delayed by an entire wavelength.

"one wavelength" might not sound like a lot, but we're insanely sensitive to timing problems. If I played you an EDM track at 140bpm, and varied the bpm by just 1% you could detect the change in timing. Timing problems are very VERY noticeable to the auditory system.

Here's a real world example of this:

Last night I'm driving down the Las Vegas strip, and I'm stuck in traffic. I hear cars playing their music as they pass me. I can literally tell who has an aftermarket stereo, because the aftermarket stereos have that weird artificial HiFi signature that you get with LR4 filters. It's clean and it's pristine and the timing is all ****ed up.

For my money, I'd take a two-way speaker with high harmonic distortion and phase-correct filters over a two-way speaker with low harmonic distortion and LR4 filters. Heck, any filters over 2nd order are pretty awful, Butterworth included. I'm singling out LR4 because it's a curse on the high fidelity industry, and Linkwitz himself stopped using them.

But, again, all of this is academic. There's a dead-simple solution, LeCleach filters. It's too bad all the papers are in French and the inventor died before anyone really noticed what a great solution he had.



TLDR: phase is really simple. We want two speakers to play the same waveform in sync. Angling the speaker doesn't affect the phase if you're using appropriately sized mids and tweeters. Pathlengths make a *tremendous* difference in phase. IMHO, LR4 filters are a curse and a bandaid used to make the frequency response flat, while creating a sterile HiFi sound that's incredibly fatiguing and "unmusical."


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## sqnut (Dec 24, 2009)

Patrick Bateman said:


> IMHO, LR4 filters are a curse and a bandaid used to make the frequency response flat, while creating a sterile HiFi sound that's incredibly fatiguing and "unmusical."


That is a generalisation. I find shallow slopes even in home auio like Dyns gives diffused imaging and a bit closed, dark sound. Wilsons on the other hand.....


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> That is a generalisation. I find shallow slopes even in home auio like Dyns gives diffused imaging and a bit closed, dark sound. Wilsons on the other hand.....


I don't think most people realize how shallow a first order slope is. It's REALLY shallow.

That's what creates that 'diffuse' sound you're hearing; even an octave or two below the xover point, *the other driver is still generating significant SPL.*


















Here's an example. This is a Dynaudio Evidence. The midrange and the woofer are crossed over at 180hz, *but see how both are playing quite loudly outside of their passband.*

So you get a little 'taste' of that giant spacious image that you get with line arrays, but not to the same extreme.

















By comparison's sake, here's a Wilson Sophia.

We see the same crossover point - about 180hz. But the SPL radiated by the woofer and the midrange out-of-band is significantly less than the Dynaudio.



By the way, this brings us right back to the original post. Because OP was talking about how the sound was "stuck" to the speaker location and it was small. *And a great deal of that is due to the filter choice.* For instance, when the Dynaudio plays something, a great deal of the sound is radiation from both the midrange *and* the woofer. And yes, that will lead to the "diffused imaging" that you describe.

I hear it too. Whether you prefer it is definitely a personal thing. I own Vandersteens, which share the same design philosophy as Dynaudio, Sonus Faber, Dunlavy and Thiel.

Here's a subjective comparison:
When I hear a Dynaudio, I *do* hear a big diffuse soundstage. I find that they're one of the few speakers with a soundstage that extends past the bounds of the location. It's like a big amorphous blob and I like that.
Wilsons sound completely different. Brighter, more analytical.

Now some would say, "if Dynaudios are so big and spacious, why does anyone buy Wilsons?" And I think a lot of that will probably boil down to "cleanness" and pinpoint accuracy. The big diffuse soundstage of a Dynaudio comes at a price - which is pinpoint imaging. It's not that a Dynaudio *can't* do pinpoint imaging, but it's going to be a challenge when there's a full range signal. The reason for this is simple: if a Dynaudio is playing a signal that spans five or six octaves, *a significant amount of sound is going to be radiating from more than one driver.* This is just the nature of first order filters.

If you've been to those dumb audiophile shows, you'll see the vendors cheating constantly. The vendors favorite trick is to play some garbage like Nora Jones. A Nora Jones track only covers about five octaves of sound, from around 500hz to 8khz. *So nearly all of the sound in a Nora Jones track is radiating from the midrange and the tweeter.* And the midrange isn't even doing much; even a crummy midrange can do 500hz.

If you really want to give a loudspeaker a workout, put on something like Fleetwood Mac, where you have male voices, female voices, and the instrument that seperates the good loudspeakers from the great : drums.

TLDR: The first order filters in a Dynaudio and the 4th order filters in a Wilson will both sound dandy with a Nora Jones record. Put on something more challenging, like Fleetwood Mac, and you'll notice dramatic differences in the soundstage and intelligibility, which occur due to the filter choice. Different folks, different strokes,etc.


By the way, if any of the readers find this discussion interesting, check out the rec.audio wars of the 1990s. John Dunlavy and Albert Von Scheweikert had raging debates about this same subject. Both of them do it much better justice than I can. It's great reading, maybe the best way to learn about crossover filters.


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## cajunner (Apr 13, 2007)

does the doppler distortion more accurately imitate the natural harmonics of instruments, or should we clamp off each speaker so tightly that no harmonics are a result of ringing?

I noticed ErinH decided to swap out the Kef concentrics for a two-puddle approach and he says it is better, so I don't know what to think about that.

the relative benefit of low order slopes may be overestimated in a car, but most people will take a coax approach as the lower standard of care, versus the component system with added roll-off in the crossovers.

I can't say I would go so far as to say "hifi-sounding" is a bad thing, since it's clarity that carries the day in my search for the speakers I'd put in my car.

Which, is weird because at home I like to listen to some little planar drivers with a little sub, which is all wrong based on the logistics of what I should want. 

then you get into just how many drivers are needed to span the 20-20 bandwidth, with low distortion and for most it's taken as a given that adding purpose built parts will help overall, but then you get in front of a high efficiency set up and the back loaded horns booting in the bass, you'd swear that sounds more natural even with doppler distortion crashing the whizzer cone's output on the higher frequencies.


so, phase is relative and crossover design is complex, when you consider that it's not an even fix just to invert, because it's a rotating angle, just because you are 180 degrees out of phase at say, 500 hz on your crossover setting, you don't realize that you might be only 90 degrees out of phase by the time you're at 125 hz, or whatever.

and it seems like the only really viable chance most armchair speaker designers have using passive components is to just go 12 db/oct and let the drivers sum at the crossover point, any fiddling around with odd order and higher order derivatives only brings pain...

but luckily the DSP revolution has brought about an evening out of the playing field, and the end result is that with patience and perhaps a little prodding even a blind squirrel eventually finds a sweet spot after point and click, dragging sliders.

would it be fair to say that phase doesn't matter in a car, since it's all early reflecting and you can't cover the glass with room treatments?

I don't think so, I also don't believe very many people actually ever get their system to sound natural, because the offset room decay, isn't fixed by time aligned drivers. And we can tell, since we're equipped with some really good measuring devices.

But, we can control the direct path and it's relatively easy to get it close enough but I can't help but remain impressed by the long-ago design approach used by those first compression driver/ under-dash horns, whether that's Holdaway or Stevens or Clark, because of how many things it gets right, if only it were easier to modify the car to suit the installation...

and the reality that the image of a stage is a psychoacoustic event and it's height from speakers underdash, may sound "on the dash" but is not really, when moving from a car with speakers that are "on the dash" so we still need to work something out, we still need to tamper with that almost there fix of HLCD and mid basses, if the goal is panoramic stage setting from outside the mirrors through the eyeballs horizontal axis, vertically...

now, I haven't had the chance to hear a car that had a full dash rebuild where the drivers were fixed to this height on-axis, I don't know if it is really important, I have read where you wouldn't want the output of a horn to be on-axis anyway, but in the home I think it's okay to bring them to ear level, so I am not sure why that caution exists...


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## Patrick Bateman (Sep 11, 2006)

cajunner said:


> does the doppler distortion more accurately imitate the natural harmonics of instruments, or should we clamp off each speaker so tightly that no harmonics are a result of ringing?


Personally, I'm not convinced that doppler distortion is a problem. If you're worried about it, use larger radiators.



cajunner said:


> I noticed ErinH decided to swap out the Kef concentrics for a two-puddle approach and he says it is better, so I don't know what to think about that.


David Smith, formerly of Kef, hints at this over at Diyaudio. He created a solution at Snell which appears to address the shortcomings of the Kef Uni-Q. (Basically in a UNI-Q you get some diffraction at the throat. The very small tweeter will also create some challenges as far as xover point goes. I am using UNI-Qs at home, and I have measured mine. The tweeter xover is insanely high, likely due to the issues described. The very high xover point likely stretches the midrange drivers right to their limit, and possibly past it. David Smith's Snell solution is neat and I think may well work better than Uni-Q.)



cajunner said:


> the relative benefit of low order slopes may be overestimated in a car, but most people will take a coax approach as the lower standard of care, versus the component system with added roll-off in the crossovers.


Coaxes are great, but introduce a different set of challenges. Someone should clone David Smith's Snell solution. I'd do it myself but I'm working on something else 



cajunner said:


> I can't say I would go so far as to say "hifi-sounding" is a bad thing, since it's clarity that carries the day in my search for the speakers I'd put in my car.


I like intelligibility, but I'm really losing enthusiasm for low distortion. To me, the easiest way to lower distortion is push-pull. But I've even stopped doing that. I'm almost willing to say that low to moderate distortion sounds better than very low distortion. There's something weirdly "lifeless" about ultra low-distortion speakers, particularly at low frequencies.



cajunner said:


> Which, is weird because at home I like to listen to some little planar drivers with a little sub, which is all wrong based on the logistics of what I should want.


I have some Monsoon planars. One of my 'Eureka' moments was when I was measuring their phase response. I couldn't get a good measurement, they had some of the crummiest phase I've ever seen.

And then I realized what the problem was - *the sound radiating from one side of the diaphragm is out of phase with the sound radiation from the center.*

To me, this was HUGE. Because it made me realize that it's not just a question of phase, *it's also a question of what the frequencies are.* IE, does phase matter at 10khz? Does phase matter at 1khz? Does phase matter at 500hz?

The Monsoons can't do phase right if you play them to 20khz.
But - and this is A BIG BUT -
If you limit their response to 10khz or so, they CAN do the phase right.

To me, this is a really interesting question. Our auditory systems can't detect phase at all at high frequencies, but where that cutoff lies is a matter of debate. Is it 10khz? 5khz?

I'm guessing somewhere around 2khz, but that's just a hypothesis.

If you start going down this rabbit hole, you start focusing on getting the phase right at midrange and lower frequencies. Which, luckily enough, is where it's actually pretty easy to get it right! IE, if you have a tweeter and you want to shift it's phase by 90 degrees at 2khz, you move it 4.25cm. And that's not a lot; that's the type of thing where you really have to keep your head in a vise to get it right.

OTOH, if you have a midrange and you want to shift it's phase by 90 degrees at 500hz, you move it 17cm. And that IS quite a bit; that's about seven inches.

When I look at these numbers, I start to see why the location of midranges is so important. 90 degrees of phase shift at 500hz isn't something that's easy to visualize. *But I can definitely tell you that if you move a midrange backwards by seven inches, I can tell it's been moved.*



cajunner said:


> then you get into just how many drivers are needed to span the 20-20 bandwidth, with low distortion and for most it's taken as a given that adding purpose built parts will help overall, but then you get in front of a high efficiency set up and the back loaded horns booting in the bass, you'd swear that sounds more natural even with doppler distortion crashing the whizzer cone's output on the higher frequencies.
> 
> 
> so, phase is relative and crossover design is complex, when you consider that it's not an even fix just to invert, because it's a rotating angle, just because you are 180 degrees out of phase at say, 500 hz on your crossover setting, you don't realize that you might be only 90 degrees out of phase by the time you're at 125 hz, or whatever.


IMHO, what we want to avoid are rapid changes in phase.
Personally, I am not convinced that gentle changes in phase are audible.

I think this may explain why tapped horns with their 90 degrees of phase shift sound better to me than vented boxes with their 180 degrees of phase shift, and why 2nd order filters with their 180 degrees of phase shift don't sound as obnoxious as LR4 filters with their 360 degrees of phase shift.



cajunner said:


> and it seems like the only really viable chance most armchair speaker designers have using passive components is to just go 12 db/oct and let the drivers sum at the crossover point, any fiddling around with odd order and higher order derivatives only brings pain...


Maybe.

Here's a couple of things I think are promising:

1) very steep filters, like 48db/octave or higher. Basically you're going to trash the phase response, but it's limited to a narrow bandwidth.

IE, I'd rather see the phase completely trashed over one half of an octave, than have it trashed over an octave or even two octaves.

If you have a LR4 crossover at 2khz, which is fairly standard, you see massive phase rotation throughout the entire midrange, from 1khz to 4khz.

In my current speakers I'm using 48db/octave filters, but I pushed the xover to 5khz, hopefully up into an octave where destroying the phase response isn't as audible.

IIRC, there's a couple of companies that do this in hi-end audio, I think Joseph Audio is one of them.

In the long run, I'll probably end up doing LeCleach. I need to figure out the math tho, the LeCleach filters can be done with miniDSP but they're not as simple as picking a frequency and a slope, it's a combination of frequency, slope, and delay



cajunner said:


> but luckily the DSP revolution has brought about an evening out of the playing field, and the end result is that with patience and perhaps a little prodding even a blind squirrel eventually finds a sweet spot after point and click, dragging sliders.
> 
> would it be fair to say that phase doesn't matter in a car, since it's all early reflecting and you can't cover the glass with room treatments?


Andy keeps saying this, and I have no idea why.
As noted above, 90 degrees of phase shift at 500hz is equivalent to moving a loudspeaker by 6.75". *If you can't detect if a loudspeaker has been moved 6.75", I'd like to sell you a hearing aid.*

YES, I do think it's possible to move a supertweeter by seven inches, without it being audible, but that's because we're not sensitive to phase at high frequencies. At low frequencies it's a different story. I can easily tell the difference between a midrange speaker mounted in a door, and a midrange speaker mounted in the kick panels.



cajunner said:


> I don't think so, I also don't believe very many people actually ever get their system to sound natural, because the offset room decay, isn't fixed by time aligned drivers. And we can tell, since we're equipped with some really good measuring devices.
> 
> But, we can control the direct path and it's relatively easy to get it close enough but I can't help but remain impressed by the long-ago design approach used by those first compression driver/ under-dash horns, whether that's Holdaway or Stevens or Clark, because of how many things it gets right, if only it were easier to modify the car to suit the installation...
> 
> ...


The think that really impressed me about the SpeakerWorks solution, besides that it sounded great, was how competitive it was with speakers in 2015.

Here's an example of what I mean:
Five years ago I saw Skrillex on this redonkulous PK sound system up in Canada, and it kinda changed my life because I didn't know it was possible to create something that was THAT bone crushing. Dynamic, clean, effortless, it was by far the most amazing PA I'd ever heard.

For the lulz, I did a sim comparing this megabuck system from 2010 to the horn-loaded systems we had in the 90s.

Much to my surprise, the horn-loaded systems were competitive. The PK rig might have a little bit more output, but the 90s systems with a fraction of the speakers and a fraction of the power were very VERY close.

So it turns out it pretty much boils down to Hoffman's Iron Law:

1) use a ****-ton of power and a ****-ton of high excursion speakers like we do now

or 

2) use a modest amount of power, and a whole lotta horn loading, like SpeakerWorks did in the 90s

Either solution will get you there.

In hindsight, a big part of the mind-blowing effect of the 2010 show is that the modern solution can play lower. (A vented sub with 1000 watts and a horn sub with 100 watts may have similar output levels, but the vented sub will play lower. Hoffman's Iron Law.)

This isn't a big problem in the car though, because of cabin gain.


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## oabeieo (Feb 22, 2015)

Doesn't phase constantly change as any given roll off begins from a crossover? A steeper slope has a more radical speed in which phase is changed. As frequency is being increased or decreased ( HP or LP) the phase shift is not fixed and changes as amplitude decreases. The rate at which phase is spun on a 6db slope is much slower vs. a 24 db slope and much less noticeable and almost impossible to pick up by ear on a 6db slope because we can't hear the shift fast enough. A steep slope we can hear the shift because can swirl from 0deg to 01 degrees than 2degrees and onward to 20 degrees and keeps degree by degree up to 180 degrees and eventually back to 360deg over and over again many times during roll off so we do hear at least the first 12db of it. Which could be half a oactave! The shift occurs simply because amplitude has changed. Just by turning the volume up on your deck causes a global phase shift. So in essence , the spiral in which phase is moving on a first order slope is so much less noticeable to the point it's almost imprecivaable. Than you have to deal with the speakers natural spiral of phase shifting which naturally occurring as on top of it and if the combination of the speakers particular point in where it's polar responce doesn't like where your crossover is set could lead to a bad combo ... 
Ok maybe I completely don't understand phase , maybe I'm only half right I d k . But that's how I understood it and please correct me if I'm wrong


As Patrick mentioned ^ moving a driver a few inches shifts it's phase? Why? Because the change in amplitude?


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## oabeieo (Feb 22, 2015)

Cajunner ? What is Doppler ? That's a new one to me. Is that harmonics ?


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## thehatedguy (May 4, 2007)

Doppler distortion:

Doppler Distortion in loudspeakers

Oh there is a spread sheet in the "Quasi optimal crossovers for high efficiency speakers" thread on DIYA that has the JMLC stuff in it. It helps a tad if you can read French...which I can't.


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> Doesn't phase constantly change as any given roll off begins from a crossover? A steeper slope has a more radical speed in which phase is changed. As frequency is being increased or decreased ( HP or LP) the phase shift is not fixed and changes as amplitude decreases. The rate at which phase is spun on a 6db slope is much slower vs. a 24 db slope and much less noticeable and almost impossible to pick up by ear on a 6db slope because we can't hear the shift fast enough. A steep slope we can hear the shift because can swirl from 0deg to 01 degrees than 2degrees and onward to 20 degrees and keeps degree by degree up to 180 degrees and eventually back to 360deg over and over again many times during roll off so we do hear at least the first 12db of it. Which could be half a oactave! The shift occurs simply because amplitude has changed. Just by turning the volume up on your deck causes a global phase shift. So in essence , the spiral in which phase is moving on a first order slope is so much less noticeable to the point it's almost imprecivaable. Than you have to deal with the speakers natural spiral of phase shifting which naturally occurring as on top of it and if the combination of the speakers particular point in where it's polar responce doesn't like where your crossover is set could lead to a bad combo ...
> Ok maybe I completely don't understand phase , maybe I'm only half right I d k . But that's how I understood it and please correct me if I'm wrong
> 
> 
> As Patrick mentioned ^ moving a driver a few inches shifts it's phase? Why? Because the change in amplitude?


Phase and delay both measure the same thing: time.

Here's three examples:

1) Let's say you have a midrange playing a full range signal. You pick up that midrange and you move it 34 centimeters further away. *You just delayed the midrange by one millisecond.*

This is because sound travels 34 centimeters in one millisecond.

2) Let's say you have a midrange playing a full range signal. You delay that midrange with your miniDSP by one millisecond. *You just delayed the midrange by one millisecond, or the equivalent of moving it 34cm away.*

3) Let's say you have a midrange playing a full range signal. You filter that midrange at 1khz with your Linkwitz Riley fourth order crossover. *You just delayed the midrange by 17cm, or 180 degrees at 1khz.*

That last one is a skull crusher I know. I had to read and re-read some articles before I typed that paragraph. At the bottom of this post are some articles that explain what's going on.



Now let's get to the fun stuff:
Once we understand how much phase shift we have, we can translate that phase shift into distances, which are a lot easier to understand. It's hard to comprehend "90 degrees of phase shift at 500hz" but it's easy to understand "500hz is lagging ten centimeters behind the tweeter."









Here's a Linkwitz Riley fourth order lowpass filter. This shows the response and the phase. Based on this graph, we can see the following:
1) at the xover point of 1khz, the filter is creating 180 degrees of phase delay. That's a distance of 17cm, because 1khz is 34cm long. 
2) at 500hz, the filter is creating 90 degrees of phase delay. That's a distance of 17cm, because 500khz is 68cm long. 
3) at 250hz, the filter creating 45 degrees of phase delay. That's a distance of 17cm, because 250hz is 136cm long. 









Here's a Linkwitz Riley fourth order highpass filter. This shows the response and the phase. Based on this graph, we can see the following:
1) at the xover point of 1khz, the filter is creating 180 degrees of negative phase delay. That's a distance of 17cm, because 1khz is 34cm long. 
2) at 2000hz, the filter is creating 72 degrees of negative phase delay. That's a distance of 3.4cm, because 2khz is 17cm long. 
3) I'm not going to bother doing the math on 4khz. The delay is negligible.

This post is not for the faint of heart. I really learned some things typing it up. Took me about an hour. Here's some reading:

http://en.wikipedia.org/wiki/Linkwitz–Riley_filter

graphs courtesy of this site : LADSPA Plugins for Active Loudspeakers | Richard's Stuff

AV: Understanding Relationships: Bringing Clarity To Phase, Frequency And Time - Pro Sound Web


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## Patrick Bateman (Sep 11, 2006)

If you made it through the last post, you're probably seeing something that wasn't obvious to me until 30 minutes ago:

*if you applied a delay to the tweeter, you could fix a great deal of the problems that exist in the Linkwitz Riley fourth order crossover.*

I just generally wrote LR4 off as a terrible idea, but I never noticed until today that the time delay on the low pass is constant in terms of distance.

IE, *the phase delay of the LR4 filter is at it's maximum at the xover point, but due to the fact that sound waves get bigger and bigger as you go lower and lower, you wind up with a constant delay on the low pass.*

This is really cool. This means that you could simply "erase" the inherent delay of the filter with some DSP.


Before anyone writes me a check for my genius invention, note that *your delay will have the effect of flipping the polarity.*

So now we screwed up the frequency response by fixing the phase response 

Audio is such a terrible hobbie lol
Fix one problem and you create another one.

But all is not lost! If you're clever, I think you could juggle time delay and slope and get close to flat amplitude response *and* flat phase response. But before you waste any time doing that, just read the LeCleach paper. I'm pretty sure that's basically what he did. (Don't bother emailing him, he died 


In previous posts about phase, I have noted that Linkwitz has halted the use of Linkwitz filters.

It appears that Linkwitz has also realized the benefits of combining delay with Linkwitz filters. On Linkwitz's page he has the following note:

_" The steep filter slopes make the combined acoustic response less sensitive to magnitude errors in the driver responses, but *phase shift errors usually have to be corrected with an additional allpass network.*_"

(an "allpass network" is a delay network. Before the era of DSP we did it with passive components. In that era, delay networks were called "all pass networks.")


TLDR: Once you realize that the LR4 lowpass filter creates a delay that is constant in terms of time, it becomes clear that you fix many of the filters nasty artifacts by delaying the tweeter. Basically use DSP delay to get the woofer and tweeter in sync in time. I am using the word "in sync" because it won't be "in phase" at the xover. To get close to "in phase" and get close to flat amplitude would require a combination of the right xover slope and the right amount of delay on the tweeter.










Jason Winslow probably noticed that another way to do this, instead of using expensive digital delay, would be to simply put the tweeter behind the woofer. IE, have it further away from you. And that may indeed be what's going on with the filter in the Synergy horn. I can only speculate.

With an xover point of 1500hz you'd want to put the tweeter 11.33cm behind the woofer (4.46") Physically moving it 4.46" back would have the same effect as digitally delaying it 0.33 milliseconds.


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## Patrick Bateman (Sep 11, 2006)

Last post of the night, I promise.

A few years ago Tom Danley emailed me out of the blue.
There's no one I've studied more than Danley, so getting an email was great.

He went into some detail on loudspeaker phase but it COMPLETELY flew over my head. Like he was speaking a foreign language.

I gotta hand it to "oabeieo." His post was the "push" I needed to unravel the phase problem. And now that I wrote posts #67 and #68, *Tom Danley's email about loudspeaker phase makes sense now.* That email was over three years ago, that's a heck of a lot of thinking.

Neat. I think I can make a proper Synergy horn, with a phase coherent crossover and everything. (Many of the DIY "Synergy" horn projects out there only *look* like Synergy horns. Measure the phase and you'll see they're not *quite* there. Mine included, of course. The phase is good, but nowhere near as good as the real thing.)


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## thehatedguy (May 4, 2007)

Well the Quasi Optimal crossover thread talked about a lot of that stuff you typed  They talk about using delays and various slopes to get rid of the group delay from the XO.


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## sqnut (Dec 24, 2009)

So you're basically agreeing that LR4 works in a car as long as you have the ability to time the drivers. With a xover of say 3khz between a woofer and a tweeter on 4th order slopes the woofer is out of phase by one cycle, so just delay the tweeter ~0.3 ms from measured distance. Start by measuring the distance to the speakers and then tweak by ear. It's all down to timing, which is why I couldn't understand why you were so fixated on phase angles and phase on one driver, while both were playing.

In a car use 4th order slopes, set delay according to measurement and then time by ear. Use matching slopes on HP/LP. 

[edit]
My discovery route was not as exciting or high profile as yours. It's something I discovered while tweaking endlessly over years based on hearing small deltas of how it sounds, once I was done with measuring.

I have come to the conclusion that the correct timing between the drivers, left to right and between each set of speakers sub, woofers, mids, tweets require specific timing. Measured distance does well between sub and woofer but when you get into crossing drivers playing ~ 2khz+, measured distances are just starting points. Timing the upper mids and higher so that you hear them just before everything else or with everything else or just after everything else are three very different sounds. [/edit]


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> Well the Quasi Optimal crossover thread talked about a lot of that stuff you typed  They talk about using delays and various slopes to get rid of the group delay from the XO.


My mind is thoroughly ****ing blown. When I woke up this morning I made my poor wife sit there and listen to me while I explained it for 45 minutes.

The main reason I type a lot of this stuff on the Internet is that explaining something to other people frequently forces me to figure out how it works.










One of the big mysteries about phase, was *how do you figure out how much to slant the baffle?* IE, I knew that loudspeaker manufacturers slanted the baffle to put the midrange in phase with the tweeter.

But I always had two unanswered questions:









1) Why does the pathlength difference vary so dramatically? For instance, the midranges in a Thiel or a Vandersteen are less than two inches ahead of the tweeter, *but the midbasses in a Synergy horn are nearly TWO FEET ahead of the tweeter.* That's a CRAZY gap, but the Synergy horn's phase is about as good as it gets. So I never quite understood how Danley got away with these nutty pathlength differences, without all-pass networks or DSP delay.

2) I knew that the crossover filter ****ed up the phase response at the xover point. I *thought* that the effect was basically negligible above and below the xover.
IE, I thought that if you had a xover that sounded like **** at 2khz, you could simply "push" the xover higher, *where the ****tiness was less audible.*

Turns out I was wrong; you might have an xover at 2khz, *but the phase shift is present over six, seven, or even eight octaves!* In a three way you can see phase shift across ten octaves!


Again, mind totally blown.


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## Patrick Bateman (Sep 11, 2006)

sqnut said:


> So you're basically agreeing that LR4 works in a car as long as you have the ability to time the drivers. With a xover of say 3khz between a woofer and a tweeter on 4th order slopes the woofer is out of phase by one cycle, so just delay the tweeter ~0.3 ms from measured distance. Start by measuring the distance to the speakers and then tweak by ear. It's all down to timing, which is why I couldn't understand why you were so fixated on phase angles and phase on one driver, while both were playing.
> 
> In a car use 4th order slopes, set delay according to measurement and then time by ear. Use matching slopes on HP/LP.
> 
> ...


I think there are three possible ways to implement what you are describing, and every possibility has a drawback.

These aren't fightin' words, just evaluating the options here:









1) In the first case we use LR4 on the lowpass, LR4 on the highpass, and the speakers are right next to each other. I can't recall what the delays and xovers are in the Magic Bus, just using the pic as an example of the mounting arrangement.
*In scenario one, we have flat response, but the phase is ****ed*, or as Linkwitz wrote, "The steep filter slopes make the combined acoustic response less sensitive to magnitude errors in the driver responses, but phase shift errors usually have to be corrected with an additional allpass network."

2) In the second case, we use LR4 on the lowpass, LR4 on the highpass, the speakers are right next to each other, *and we delay the midrange one wavelength.* Now we're getting somewhere. *The midrange and the tweeter are in phase.*
There's still a couple problems. First, we still have ninety degrees of phase shift above the xover point. Probably not the end of the world. The bigger problem is that you have to put these pods on the dash, like Jon Whitledge did.









Erin shrunk the footprint by going with a coaxial.
Another nice thing about a coaxial is that the reflected energy is in-phase. IE, with a vertical array like Jon's, you can fix the phase response at the microphone, but you can't fix the phase response in the back seat, or the back of the car. That might not sound like a big problem, but when you realize that a great deal of what we hear in the car is reflections, you'll understand why The Magic Bus is so big. If Jon took the same system and installed it in a Honda Civic, it wouldn't sound the same.

Sorry this is so long winded, but to me, *it seems like the ability to put the midrange IN FRONT of the tweeter, and still have everything in phase, is pretty neat.*

This goes back to another one of the things that Danley talked about. He talked about this idea that you could have a loudspeaker that was a foot and a half deep, and the origin of the sound wasn't clear. Is the sound coming from a meter away? A meter and a half? It's really hard to say.

I had some SH50s in my house for a week, and that was one of very odd things about them, they were humongous speakers and you could barely tell that the sound was coming from them.

My favorite example of this was when our twelve year old daughter was sitting ONE FOOT away from one, she asked "is this one on?"

Literally one foot away from a loudspeaker the size of a small refrigerator, and she wasn't sure if music was coming out of it.

Neat, huh?

So how do I do that in a car...


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## seafish (Aug 1, 2012)

PB, if I am reading you correctly, then the ideal distance between the tweeter and midrange depend on both the chosen XO point as well as the steepness of the XO slope???

If so, are their equations that one could use to determine the ideal XO and slope for a set distance between sources (obviously as long as said sources are capable of operating within the XO range selected) ?? Or viceversa…an equation to determine the ideal distance between tweeter and midrange based on a chosen XO and slope??


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## sqnut (Dec 24, 2009)

Patrick Bateman said:


> So how do I do that in a car...


By timing the drivers two at a time. Start with L&R woofer, then left woofer with left mid next right with right. Left mid with left tweet then right with right. Now play everything and do the final tweaks with all drivers playing. You will get to a point where you can look at a driver and not feel or hear any sound from it. I mentioned it in one of my earlier posts. 

Phase in a car is nothing more than timing. At the end of the day, any audible phase issues will be heard in the response domain. With the right timing you can cure all phasey sounding issues. Very easy to catch in vocals. If you have phase issues the vocals will always sound stretched no matter what you do on the eq.


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## Patrick Bateman (Sep 11, 2006)

seafish said:


> PB, if I am reading you correctly, then the ideal distance between the tweeter and midrange depend on both the chosen XO point as well as the steepness of the XO slope???
> 
> If so, are their equations that one could use to determine the ideal XO and slope for a set distance between sources (obviously as long as said sources are capable of operating within the XO range selected) ?? Or viceversa…an equation to determine the ideal distance between tweeter and midrange based on a chosen XO and slope??


I'm sitting here at Starbucks, but the following appears to be true:

1) If you know the xover point and slope, you can calculate the gap between the midrange and the tweeter
2) If you know the gap between the midrange and tweeter, you can calculate the xover point and slope

The obvious thing to do is to select the xover point and slope based on the loudspeaker location. But I think there's a reason you might choose the *location* based on the xover point and slope.

IE, make the loudspeaker location fit the xover point, not make the xover point fit the loudspeaker location.


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## seafish (Aug 1, 2012)

Patrick Bateman said:


> I'm sitting here at Starbucks, but the following appears to be true:
> 
> 1) If you know the xover point and slope, you can calculate the gap between the midrange and the tweeter
> 2) If you know the gap between the midrange and tweeter, you can calculate the xover point and slope
> ...


PERFECT I was hoping as much…I have a location deep and up on the trucks dash where I will be able to mount both my tweets and midrange in separate spherical pods. In fact, I posted a pic of them on one of your other threads, but may have gotten lost in the otherwise much more interesting discussion. The center to center distance between the tweets and midrange will be as little as 4" and as much as 6" if I am able to push the tweets further back into the corner by cutting the pillar trim back a little. I MAY be able to push the midranges out with them, but I don't think so. That being said, I will also be able to rotate the pods AFTER installation so that I can adjust on/off axis response. I may even be able to crossfire the tweeter on axis, OVER the face of the midrange like I have seen some high end diy home speaker designs do.

At this point in time, I was planning on crossing them at 3 khz, with either an 18 or 24 slope, but I could go as low as 2500 or higher, depending on what is "ideal". 

Are there any equations that will let me know if I am at least in the ballpark for an ideal XO vs on center separation??

Here is the pic of my install mock up I was talking about--


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> Phase and delay both measure the same thing: time.
> 
> Here's three examples:
> 
> ...


Dood thank you!!!i tryed figured out phase off a wiki article I think this makes way more sense and now I understand phase charts a lot better, wow that is fantastic! I didn't loose any of that very understandable, thank you, 

I knew there was something I was missing


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> If you made it through the last post, you're probably seeing something that wasn't obvious to me until 30 minutes ago:
> 
> *if you applied a delay to the tweeter, you could fix a great deal of the problems that exist in the Linkwitz Riley fourth order crossover.*
> 
> ...



So let's just say you have a basic deck that has a high pass at 100hz and its hooked to a amp which also has a high pass at 100hz BOTH are 12db crossovers ; does this now make a 24db crossover or is it still a 12db crossover?


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## oabeieo (Feb 22, 2015)

thehatedguy said:


> Doppler distortion:
> 
> Doppler Distortion in loudspeakers
> 
> Oh there is a spread sheet in the "Quasi optimal crossovers for high efficiency speakers" thread on DIYA that has the JMLC stuff in it. It helps a tad if you can read French...which I can't.


A ahhhh reading ..... I will enjoy it


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## oabeieo (Feb 22, 2015)

Patrick , doesn't increasing amplitude also change its phase a tiny bit as well though? Just globally? On a o scope of you look at a wave form the peaks may be at one point on any particular wave , adding amplitude makes the peaks taller , but also makes the waves wider, and any change in shape is movement in the distance between nodes , distance equals time in the acoustical realm . So isn't it correct that distance changes phase and so does amplitude?

We revert to the term phase as in what phase of development in a duty cycle or cycle , so phase. Is meaning a multitude of things I imagine phase literally means a particular point in a cycles length. So it doesn't matter if we physically move the cycle by its radiating point or alter with electrical manipulation. it's measured point or perceived time by a listener in space in whatever has been done to change the cycle in any way would affect its "phase" .... To include , physically relocating, delaying and changes in amplitude OR frequency


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## thehatedguy (May 4, 2007)

"Quasi-optimal" crossover for high-efficiency loudspeaker system - diyAudio

The link to the spread sheet is at the bottom of post 65.

Notice in all of those, the tweeter is behind the woofer. I even asked later on if you could flip flop things if the tweeter was in front of the woofer and accomplish something similar...II think the answer was either no, or they doubted it. There are several combinations presented in that post that seem to work well.

I would speculate and say the group delay in the crossover up high like in a tweeter could be more audible than a phase shift. We know humans can hear group delay, but the jury is still out on phase, especially considering the speakers being located in a glass house where we have reflections adding to the direct sound field...and no way to really get around that problem.

Then again, I could be completely wrong with that speculation.

But now that I think about it, I have always liked my mids to be in front of the high frequency drivers...dunno why.


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## oabeieo (Feb 22, 2015)

thehatedguy said:


> "Quasi-optimal" crossover for high-efficiency loudspeaker system - diyAudio
> 
> The link to the spread sheet is at the bottom of post 65.
> 
> ...



Good grief! Okay I have to do a LOT more reading to get all of that! I got through 3 pages before my head completely popped off. Now that blood has squirted all over my ego I have to concede that I have no clue what I'm saying. 

I have a question tho , are these guys on that link talking about a passive design with the formulas they are talking about?


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## thehatedguy (May 4, 2007)

You probably could do them passive...but with the delay involved, I thought most were doing them active.

But as long as you have the right offsets and such entered into a passive crossover design program and your transfer functions match up, you probably could do it passive.


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> Dood thank you!!!i tryed figured out phase off a wiki article I think this makes way more sense and now I understand phase charts a lot better, wow that is fantastic! I didn't loose any of that very understandable, thank you,
> 
> I knew there was something I was missing


Thanks to everyone in this thread! I've been trying to figure this stuff out for a few years now.


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## Patrick Bateman (Sep 11, 2006)

oabeieo said:


> Patrick , doesn't increasing amplitude also change its phase a tiny bit as well though? Just globally? On a o scope of you look at a wave form the peaks may be at one point on any particular wave , adding amplitude makes the peaks taller , but also makes the waves wider, and any change in shape is movement in the distance between nodes , distance equals time in the acoustical realm . So isn't it correct that distance changes phase and so does amplitude?
> 
> We revert to the term phase as in what phase of development in a duty cycle or cycle , so phase. Is meaning a multitude of things I imagine phase literally means a particular point in a cycles length. So it doesn't matter if we physically move the cycle by its radiating point or alter with electrical manipulation. it's measured point or perceived time by a listener in space in whatever has been done to change the cycle in any way would affect its "phase" .... To include , physically relocating, delaying and changes in amplitude OR frequency


As I understand it (and I don't understand it well), it doesn't matter how you modify the frequency response, it changes the phase.

IE:

1) if you use an active low pass filter to create a low pass filter, it will introduce a delay

2) if you use a passive low pass filter to create a low pass filter, it will introduce a delay

3) If you have a speaker with absolutely no filter at all, and the response is falling due to it's inductance, it will introduce a delay

IE, doesn't matter how you from point A to point B, if there's a lowpass, you get a delay

I believe this is called "minimum phase" but don't quote me on that 

I know there's some exceptions to the rule:

1) software like Rephase basically allows you to delay the signal by different amounts at different frequencies. IE, instead of delaying the entire output by one millisecond, you could do it over a single octave, or even a fraction of an octave. I heard Bill Waslo's Synergy Horns with Rephase, it sounded great

2) Vented boxes complicate this a great deal, because you're not just talking about the frequency response, you're also complicating with a resonance in the port and the pathlength difference introduced by the distance traveled in the enclosure and the port. You could have two ported boxes, tuned to the same frequency, and the phase could vary because the port diameter and length is different.


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## thehatedguy (May 4, 2007)

Any EQ that you apply will also change phase as well.

Which is another reason why flat phase response in a car will be tough to pull off.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> Any EQ that you apply will also change phase as well.
> 
> Which is another reason why flat phase response in a car will be tough to pull off.


True.

If anyone on the thread wants to see how this works, check out the "filter wizard" in hornresp.

I know hornresp is a tough program to learn, but the filter wizard is pretty straightforward. Just type in the frequency and the slope and it'll show you everything you want to know.

As far as getting "flat phase response" goes, I wouldn't make any effort to fix the phase outside of the first four or five milliseconds. Past that point it's going to be tough to get a clean measurement.

Most of my projects for the last few years have been Synergy horns, so I've simply created the crossover and the measurements outside of the car.


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## gijoe (Mar 25, 2008)

oabeieo said:


> Patrick , doesn't increasing amplitude also change its phase a tiny bit as well though? Just globally? On a o scope of you look at a wave form the peaks may be at one point on any particular wave , adding amplitude makes the peaks taller , but also makes the waves wider, and any change in shape is movement in the distance between nodes , distance equals time in the acoustical realm . So isn't it correct that distance changes phase and so does amplitude?
> 
> We revert to the term phase as in what phase of development in a duty cycle or cycle , so phase. Is meaning a multitude of things I imagine phase literally means a particular point in a cycles length. So it doesn't matter if we physically move the cycle by its radiating point or alter with electrical manipulation. it's measured point or perceived time by a listener in space in whatever has been done to change the cycle in any way would affect its "phase" .... To include , physically relocating, delaying and changes in amplitude OR frequency


Changing amplitude alone will not change phase. When you increase the voltage/amplitude (y-axis of wave) the frequency (x-axis) does not change at all, that wave will still cross the x-axis at the same points. What may be happening however is that your o-scope is automatically adjusting the scale to fit the entire wave on the display. Phase is purely x-axis, you can start with 2 signals of the same frequency and amplitude that are perfectly in phase and if you increase the amplitude of one wave to 100 times (arbitrary number, since any change in amplitude alone will not change the phase relationship) that of the other wave, they will still be perfectly in phase. 

What does happen is that as you increase the amplitude of one signal, you also increase the amplitude of it's harmonics and reflections. But, two pure sine waves of the same frequency will remain in phase regardless of the relative amplitude.


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## oabeieo (Feb 22, 2015)

gijoe said:


> Changing amplitude alone will not change phase. When you increase the voltage/amplitude (y-axis of wave) the frequency (x-axis) does not change at all, that wave will still cross the x-axis at the same points. What may be happening however is that your o-scope is automatically adjusting the scale to fit the entire wave on the display. Phase is purely x-axis, you can start with 2 signals of the same frequency and amplitude that are perfectly in phase and if you increase the amplitude of one wave to 100 times (arbitrary number, since any change in amplitude alone will not change the phase relationship) that of the other wave, they will still be perfectly in phase.
> 
> What does happen is that as you increase the amplitude of one signal, you also increase the amplitude of it's harmonics and reflections. But, two pure sine waves of the same frequency will remain in phase regardless of the relative amplitude.



Dood that makes sense ! I understand that now , 
Aurora Colorado? Why aren't you working In my shop? ( kidding) ok not kidding . Maybe we could talk sometime


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## oabeieo (Feb 22, 2015)

Patrick Bateman said:


> As I understand it (and I don't understand it well), it doesn't matter how you modify the frequency response, it changes the phase.
> 
> IE:
> 
> ...


Okay so I got to start remembering delay and phase . And how they work as one in a filter, and the doppelgänger page I read about phase modulation distortion . I think I'm starting to get it all now , I know I will have to erase a bunch out of my haead and sorta start over and re think it .


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## piyush7243 (Sep 9, 2009)

Phew... that was a long long read for the LeCleach crossovers and other things.Around 25 % was understood and rest all have to be re-read to understand in depth. Few questions

Le Cleach crossovers/filter was designed more in need with tuning the Horns to take care of the ragged frequency range and provide a better imaging

Trying to achieve the same in a car environment is going to be very very tough even if we get a horn setup in a car. More can be found out after measuring the same in a car environment

Also any kind of crossover or phase shift will have a time domain change happening as well and vice versa.

I am still taking a look into rephase and would trouble you once again


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## cajunner (Apr 13, 2007)

oabeieo said:


> Okay so I got to start remembering delay and phase . And how they work as one in a filter, and the doppelgänger page I read about phase modulation distortion . I think I'm starting to get it all now , I know I will have to erase a bunch out of my haead and sorta start over and re think it .


the commercial that GE is using now, with the weird animal that has rainbow tail feathers at the end, pops up as I read your post.

ideas, huh?

on one hand, I think that there are audio savants that don't have to actually read the descriptions before understanding the theory, like the rain man who counts the toothpicks spilled on the floor.

I still see a pile of toothpicks, but sometimes, I can get a few to bunch up, like vibrations in the car body mimics the natural decay of a bass drum's hardware...

and it just moves across playing fields.


Like I once posited long ago, about IEM and how balanced armatures are like ports, and managing them adds or subtracts to bass in the ear canal "enclosure" and you could say, people who like the sound of bandpass boxes should follow the order, and those who have to listen to direct radiators should cringe at the local concert venue, with subs coming out of folded horns...

you can miniature the thing to where it's all in your ear hole, or bring it out a little bit and treat cans with "damping" like applying the golden rule to closed ear headphones, who has done that yet?

haha..


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## oabeieo (Feb 22, 2015)

cajunner said:


> the commercial that GE is using now, with the weird animal that has rainbow tail feathers at the end, pops up as I read your post.
> 
> ideas, huh?
> 
> ...


Lol yes we all have our likes and dislikes and things we find important or not so much , 
In the end what works works and what doesn't doesn't . But I definitely like to keep a open mind and not have a know it all attitude because in my short life on earth and the countless hours I have spent on one hobby seems like right when I think I have something solved and go apply it on a diffrent setup it's complicated and the rules seem to vanish like I learned nothing from the last build. And I have done a ton of installs and I can't think of one that turned out just amazing with the very first try at it. Seems right when I think I understand a cars environment poof . Very Un predictable and the most unexpected setup or configuration may just be "golden" . 

The fight goes on and it won't ever stop. Every day we want to think something is best just because we had good results one time with a certain flavor, can't argue with results now. Or can you ? Lol some seem to think so , some may not but its fun and as much as it frustrates me to have a dip at 125hz I won't ever give up on that dip or speaker location until I have tryed every possible combination of controls and buttons . Why? Because it's fun!


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## sqnut (Dec 24, 2009)

oabeieo said:


> Lol yes we all have our likes and dislikes and things we find important or not so much ,
> In the end what works works and what doesn't doesn't . But I definitely like to keep a open mind and not have a know it all attitude because in my short life on earth and the countless hours I have spent on one hobby seems like right when I think I have something solved and go apply it on a diffrent setup it's complicated and the rules seem to vanish like I learned nothing from the last build. And I have done a ton of installs and I can't think of one that turned out just amazing with the very first try at it. Seems right when I think I understand a cars environment poof . Very Un predictable and the most unexpected setup or configuration may just be "golden" .
> 
> The fight goes on and it won't ever stop. Every day we want to think something is best just because we had good results one time with a certain flavor, can't argue with results now. Or can you ? Lol some seem to think so , some may not but its fun and as much as it frustrates me to have a dip at 125hz I won't ever give up on that dip or speaker location until I have tryed every possible combination of controls and buttons . Why? Because it's fun!


The one idea that will make things fall in place and give you repeatably across cars, is understanding the fact that in a car good sound is, 70% tuning, 20% install and 10% is the equipment used.


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## Orion525iT (Mar 6, 2011)

I had kinda promised to put up some measurements for future reference and to correlate what I was hearing to something more objective. But, it's not gonna happen for a bit. I spent and inordinate amount of time making a box to fit my motherboard and power supply. The box is literally molded to the sheet metal under the rear seat, and trying to get everything to fit in the box, making it so that cabling runs are neat and tidy, making a digital out coax header, making sure that none of the connectivity to the mother board is obstructed, adding fans to keep things cool, making sure that clean runs can be made to the 2x8 ect, ect, ect was a bit more consuming than what I had anticipated..

But anywho,

Since we have brought in the discussion of crossovers, I got a question. What happens when we use two identical drivers in an array and roll one off early in attempt to get better power response higher up? I thought about doing this with the Whispers by using a low pass filter on one of the drivers to get a better match to the AMTs. But, from this discussion it seems that bad things may happen because of the phase shift introduced to the driver that is being rolled off early.

Thoughts?


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## oabeieo (Feb 22, 2015)

thehatedguy said:


> Any EQ that you apply will also change phase as well.
> 
> Which is another reason why flat phase response in a car will be tough to pull off.


True , but a phase responce that promotes good imaging is usually satisfactory, and one that doesn't cancel midbass worce is a added bonus. I've had eq phase shift actually help in some bands as far as phase goes.


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## oabeieo (Feb 22, 2015)

sqnut said:


> The one idea that will make things fall in place and give you repeatably across cars, is understanding the fact that in a car good sound is, 70% tuning, 20% install and 10% is the equipment used.


Oh I have repeatability just fine to the extent your talking about. I was just merely saying I go in and plan a system , choose speakers based off there sensitivity, fs , responce , etc etc put them in do the install and anticipate a certain sound with certain dips and peaks and once it goes in the tune is diffrent than how I had thought it would go. But I always win and tune and get there every time and repeatable? Yes, ..knowing how the car will figh me acoustically , No. 

It's like I go in and measure a car , pick the speakers and amps and dsp. Do the install , set gains, set phase , do signal delays, set eqs to flatten responce. And than right when I think there's going to be minimal smoothing out to do , ha! No ! It takes a while and sometimes a week or more to really get it to sound good. I will keep a customer car for up to a week and drive it home and back until I am satisfied. 

I guess I was referring to I wish it was as easy as setting a responce on a eq and saying " here mr. Coustomer enjoy you half way good sounding system, good luck trying to get it better. I guess I either care too much or just know what the equipment is capable of and it drives me nuts having a car leave un finished to my liking .


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## 14642 (May 19, 2008)

That was a long way to go to get to LR4 + 1 wavelength delay at the crossover on the HP = phase coherence.

The audibility of that additional delay depends a great deal on the content of the recorded material. For steady state signals, it's less audible than it is with transients that span both speaker bandwidths. 

In a car, coupled with all of the reflections from adjacent surfaces and the phase shifts from non-flat magnitude responses from left and right speakers, I don't think it's a big factor in making a car image well.


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## cajunner (Apr 13, 2007)

Andy Wehmeyer said:


> That was a long way to go to get to LR4 + 1 wavelength delay at the crossover on the HP = phase coherence.
> 
> The audibility of that additional delay depends a great deal on the content of the recorded material. For steady state signals, it's less audible than it is with transients that span both speaker bandwidths.
> 
> In a car, coupled with all of the reflections from adjacent surfaces and the phase shifts from non-flat magnitude responses from left and right speakers, I don't think it's a big factor in making a car image well.


but isn't this precisely the process for returning to the *ideal* which is the presentation of time-perfect, infinite points in space delivered in stereo?

and that each successive dilution from the ideal contributes to decay or degeneration of the signal as it is transformed from acoustic, to electronic, and back to acoustic before finally becoming bio-electric signals in the nerves of the ear that at which point, are definitive?

what I mean is, if being able to reconstruct the original phase of the electrical signal is also removing one aspect, one dimensional strata of the reproduction, that is out of alignment or distorted, then it is possibly statistically significant.

have I seen evidence of systems that attempt to put every acoustic signal into perfect phase, no...

are there systems that can do this? I am not aware, but I believe there has been some promotions purporting to be able to do it...


and is there anyone who can definitively say, "I have the ability to do it, via this program <insert program> and I have heard the results of this program on music, and I have determined that I can hear a difference for the better, in a car, and in anechoic, and in a studio, so..."

well, I don't really know about that.

first proving that a signal that has been "treated" for phase by a software manipulation does in fact improve the sound at the ears, appears to be covering a lot of ground that frankly, I'm not sure has been met by scientific process.

I agree though, with your opinion that it's not a big factor, or as lycan used to put it, a small function as opposed to a large function, haha...


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## Patrick Bateman (Sep 11, 2006)

Andy Wehmeyer said:


> That was a long way to go to get to LR4 + 1 wavelength delay at the crossover on the HP = phase coherence.


Phase has always been a bit of a mystery to me. I think 90% of the audiophiles out there don't pay it any mind, or don't understand it.



Andy Wehmeyer said:


> The audibility of that additional delay depends a great deal on the content of the recorded material. For steady state signals, it's less audible than it is with transients that span both speaker bandwidths.


Perhaps I'm sensitive to it. I find the effect unmistakable. I can walk into any stereo store and hear it; the speaker sounds clean and undistorted but the midrange sounds "off." And the reason it's "off" is unmistakable; *the midrange and the tweeter are not reproducing the same sound at the same time.* 

I'm not one of those luddites that's opposed to crossovers, I'm just opposed to crossovers that introduce a millisecond of delay smack dab in the middle of the midrange, where are ears are incredibly sensitive.

I'm using an LR8 xover on my speakers at the moment, and with the xover pushed to 5khz, I don't find the effect as audible.



Andy Wehmeyer said:


> In a car, coupled with all of the reflections from adjacent surfaces and the phase shifts from non-flat magnitude responses from left and right speakers, I don't think it's a big factor in making a car image well.


In software we have a phrase:
"that's not a defect, that's a feature."

And that's my attitude about car stereo. Put the drivers in a location where you can use the boundaries to your advantage. It doesn't take much of a waveguide to do this; a 17cm waveguide will shape a wavefront down to 2khz.

Once we're below 2khz, the wavefronts are so large, the effect of reflections is less and less, and all you need to center the stage is a bit of DSP.


TLDR : A 17cm waveguide, four channels of amplification and some delay will do the job.


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## 14642 (May 19, 2008)

"minimum phase" refers to a system in which the phase is simply a function of the frequency response. That really only exists in one configuration--a single speaker in an anechoic room. An additional driver or a single reflecting surface make the system non-minimum phase. 

In cars, it's mess to attempt to pay a bunch of attention to phase coherence between drivers because for every driver, there are an almost infinite number of apparent drivers (every reflection is an additional driver) and contribute to what we hear at varying times and levels. 

Designing crossovers for cars is simply not the same as developing crossovers for home audio speakers on known baffles in an anechoic chamber. I've found the best method is to set delays with a tape measure, measure the responses of individual drivers from several closely spaced mic positions, average those, shape the responses with filters to match LR4 closely, combine the bands and check the response. 

Occasionally, a little fiddling with the delays is helpful, especially if a first reflection is nearly as loud as the direct sound. 

In any case, the electrical response of the filters doesn't matter much. Only the measured acoustic response needs to be considered carefully. Fortunately, the car is so small and the reflecting surfaces are so close, that we don't hear them as distinctly separate events. Poorly designed crossovers that leave a hole in the response off axis can be a big tuning problem.

And finally, NEVER EQ with both right and left channels playing unless you apply the same EQ to both to change the overall shape.


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## 14642 (May 19, 2008)

Be careful generalizing the problem of the two speakers not playing the same thing at the same time. What matters is whether the sound reaches your ears at the same time. For many baffle configurations, that doesn't happen at most angles off 0-degrees.


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## macming (May 9, 2015)

How much do you usually charge for tuning? I'm about to have a shop to do some work and I'm not sure if I can afford a week worth of tuning @ shop rate. 




oabeieo said:


> Oh I have repeatability just fine to the extent your talking about. I was just merely saying I go in and plan a system , choose speakers based off there sensitivity, fs , responce , etc etc put them in do the install and anticipate a certain sound with certain dips and peaks and once it goes in the tune is diffrent than how I had thought it would go. But I always win and tune and get there every time and repeatable? Yes, ..knowing how the car will figh me acoustically , No.
> 
> It's like I go in and measure a car , pick the speakers and amps and dsp. Do the install , set gains, set phase , do signal delays, set eqs to flatten responce. And than right when I think there's going to be minimal smoothing out to do , ha! No ! It takes a while and sometimes a week or more to really get it to sound good. I will keep a customer car for up to a week and drive it home and back until I am satisfied.
> 
> I guess I was referring to I wish it was as easy as setting a responce on a eq and saying " here mr. Coustomer enjoy you half way good sounding system, good luck trying to get it better. I guess I either care too much or just know what the equipment is capable of and it drives me nuts having a car leave un finished to my liking .


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## oabeieo (Feb 22, 2015)

macming said:


> How much do you usually charge for tuning? I'm about to have a shop to do some work and I'm not sure if I can afford a week worth of tuning @ shop rate.


If a customer buys a full system from us I include it as customer service and self pride of my jobs, for your case , If you want to do it through the shop we charge 85hr but if you have you stuff installed and just need a tune you could just come by my house and I could set you up with a good flat responce for your memory and you can tweak it beyond that I wouldn't charge you to do that , or if you want to bring it down to the shop and leave it for a few days I can spend a hour or so a day on it between jobs , if it's at the shop I have to charge something , we can work something out, I'm down to just do a rta adjustment for you so long as you have everything ready to go and nothing needs to be installed or wired up.

Wouldn't it be a long drive from Dallas though? I'm in Colorado


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## Patrick Bateman (Sep 11, 2006)

Andy Wehmeyer said:


> "minimum phase" refers to a system in which the phase is simply a function of the frequency response. That really only exists in one configuration--a single speaker in an anechoic room. An additional driver or a single reflecting surface make the system non-minimum phase.












Mount your tweeters and your midranges coaxially in the corners of the dash and the windshield functions as a waveguide. Get the crossover and the phase right and you've eliminated issues with reflections and interference patterns from the other drivers down to about 350hz. That's about sixty percent of the audible bandwidth, or six octaves. Neat huh? 



Andy Wehmeyer said:


> In cars, it's mess to attempt to pay a bunch of attention to phase coherence between drivers because for every driver, there are an almost infinite number of apparent drivers (every reflection is an additional driver) and contribute to what we hear at varying times and levels.


Again, is that a defect or is it a feature? Stick the midranges and the tweeters in the corner and those reflections are your friend.



Andy Wehmeyer said:


> Designing crossovers for cars is simply not the same as developing crossovers for home audio speakers on known baffles in an anechoic chamber. I've found the best method is to set delays with a tape measure, measure the responses of individual drivers from several closely spaced mic positions, average those, shape the responses with filters to match LR4 closely, combine the bands and check the response.
> 
> Occasionally, a little fiddling with the delays is helpful, especially if a first reflection is nearly as loud as the direct sound.
> 
> ...


I agree with the rest of this.


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## cajunner (Apr 13, 2007)

so, how about this:

a line array of cone tweeters in the firewall to kick panel corner, using decent drivers in a bandwidth of say, 1600 hz on up. At least 6 of them, 2.5" cones basically touching each other.

the 6.5" door mounted midbass takes the easy push, right up to beaming where the line array just nails depth, width, and whatever else...

but up top you have a center channel.

this center channel will use a single large Sausalito lens to put out from 500 hz up to the sausalito curve's reflected top end at 1600 hz or so, one octave wide... using a compression driver of large width but thin, in height..


so what you end with, is the windshield forming a horn for the center channel, the left/right taken up by line arrays giving spacious stage size at aggressive output levels due to the line array, while the center nails the vocals above the dash for reals.

the door mid bass may need to be developed, to a pro driver status.

the compression driver sitting in a center speaker pod, could take up the same amount of room as a normal center speaker, or it could be sunk into the dash which would help to put the Sausalito further back, using acrylic wings.

I feel like a Sausalito in the center of the dash, does two things, it forces, by dispersion angle, to include the windshield rake and the dash to form a horn that by the time it hits anyone's ears 4 feet back, it will not rainbow with the left/right like most centers do when the left/right mids are in the kicks or lower doors.

The Sausalito lens will limit, by bandwidth propagation, enough of the left/right signal that not a lot of DSP will be needed to control it, and the directionality of the line array will form the huge stage that comes with, with cone drivers that have narrow dispersion patterns as part of their features, instead of negatives. 

maybe someone has tried this combination?

line array cone tweeters, compression driver mid in dash, (large format if possible) and door mid bass?


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## sqnut (Dec 24, 2009)

Andy Wehmeyer said:


> And finally, NEVER EQ with both right and left channels playing unless you apply the same EQ to both to change the overall shape.


I agree that worrying about min phase in a car is a bit of an oxymoron and like a dog chasing its tail. Imho, setting the timing and L/R balance is the easy bit. The real tuning and the toughest bit is getting the car to sound right by eq the response with all drivers playing. This is when you're dialing in tonality. By and large if you have balanced L/R you should boost/cut a frequency equally on both sides. However with almost all cars I've tuned, I find the 1-4khz range is best set by ear for L/R balance.


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## Patrick Bateman (Sep 11, 2006)

cajunner said:


> so, how about this:
> 
> a line array of cone tweeters in the firewall to kick panel corner, using decent drivers in a bandwidth of say, 1600 hz on up. At least 6 of them, 2.5" cones basically touching each other.
> 
> ...


*I find that there's generally no good reason to have more than one driver covering the high frequencies.*

Our perception of location at high frequencies is determined by frequency response. IE, if you have one tweeter that's 3dB louder than the other, it will 'pull' the image towards the louder tweeter.

And this effect is noticeable even if the rise in response is a fraction of an octave.

For instance, I once tried doing a setup in my car where the speakers weren't symmetrical, basically I was trying to put the stage above the steering wheel, instead of in front of the center of the dash. *And it didn't work at all, because the boundary reinforcement was different from one side to the other.* IE, one tweeter was louder than the other, because the two sides weren't symmetrical. I made a half hearted attempt to EQ it, but it never sounded "right."

Long story short: I think using more than one driver for high frequencies is a bad idea.









I think this may be one of the reasons I was so disappointed with the Keele CBT. To me it sounded very "spacious", like a Bose Wave Radio, but there wasn't even a hint of an image. (The CBT has something like a HUNDRED tweeters.)









If you took my idea to an extreme, you'd end up with this.

This is what I listen to when I work on my computer. (I write software, and sit in front of the computer all day.)

This is basically an Opsodis setup, but with one tweeter, not two. That's a bit extreme, but it works oddly well. I tried it with two tweeters but found that the second tweeter didn't improve the imaging, but *did* affect tonality. (You can see this in a frequency response measurement; when measuring a set of speakers in stereo there's a ton of comb filtering caused by the left tweeter interfering with the right tweeter.)

If anyone wants to try this, it's easy to do with miniDSP. It is an evolution of the ideas from here: http://www.diymobileaudio.com/forum...ion/72891-anyone-tried-using-one-tweeter.html
It took me over five years of trial and error to come up with this.

Subjectively, putting the tweeter in the center of the sound stage fills in the "hole" which appears when the left speaker and the right speaker are too far apart. In this respect, *it works like a center channel.* The neat thing is that it doesn't hurt stage width. My Genesis has a center channel (Lexicon Logic 7) and I've noticed that the center reduces stage width. The reason it does this is pretty simple; when you have a center channel playing the same sound as the left or the right, it "pulls" the width towards the center.

The neat thing about the tweeters in the center is that they're not sharing anything with the speakers on the left or on the right, so it doesn't "pull" the stage towards the center. It's as wide as stereo, believe it or not.

Actually, I'd say it's wider, because once you go this route, you can pull the mids really far apart. The only thing keeping me from moving those mids even wider is that there's a wall in the way.


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## maroon (Feb 25, 2015)

Phase interference is easy to actually _see_ (this whole phase business extends to light too). Hold the first two fingers of one of your hands about 1/16” apart. Look through the slit between your fingers, holding them a few inches away, at a brightish object, say, the sky. See the black lines between your fingers? (You may have to vary the size of the slit ever so slightly.) That’s phase cancellation. 

Another way: Imagine dropping a rock into a swimming pool. The resultant rings of ripples (small waves) going away from the point where you dropped it are a pretty much exact analogy of sound waves emanating from a burst of audio (sine waves will be the clearest) played out of a speaker. To see phase interference, drop two rocks a short distance apart at the same time. This will send out two series of waves. When the series of waves intersect, phase interference will occur. Where two peaks or two valleys meet, the result will be phase augmentation- the resultant wave peak or valley will be roughly twice as high or low (the amplitude will increase or decrease, in sound). When a peak meets a valley, the result will be phase cancellation. They will exactly cancel each other out. The water will be flat. There will be no wave (or, there will be no sound.)

A few things: First, whether or not the waves emanating from the two sources (the rocks) are “in phase” IE: dropped at the same time, or as pointed out in a previous post- at exactly the same distance away from you, is irrelevant as to whether you’ll see phase effects when more than one rock is dropped. You will. Wherever series of waves intersect, you will see- and, in a car, hear- phase effects. The patterns of interference will differ, but a pattern of interference will still be there. "In phase" simply centers the pattern.

Second, you’ll also get phase effects if each set of waves are different frequencies, to a certain degree. The interference will be different, but it’ll still be there. It’s an energy thing. Wherever there are intersecting peaks, the volume of water will increase. It must. Ditto for sound, which is after all, just pressure displacement in air instead of water.

Now try it a little differently: put a board all the way across the middle of the pool. The board extends under the surface a foot or two, and above the surface a foot or two. Cut a couple of 1” slits in the board a couple of feet apart extending from below the surface to near the top. And now, so we can see what we’re doing, instead of single rocks, let’s drop a steady stream of rocks (from a giant dump truck) at a constant rate into a spot on one half of the pool. When the energy disturbances- which travel as waves- happening on the surface of the pool hit the board, they will be blocked, except through the slits. When they hit the two slits, they will be allowed through, and we are going to see their effects- a series of ripples, or waves, on the other half of the pool, similar to when we dropped rocks there. We are going to see a series of waves emanating out of each slit, same as before. The only difference is, we can control things a bit. So, first, want to throw things out of phase? Easy. Just make the place where the rocks hit the water closer to one slit than the other (as noted in a previous post). Want to make the pattern of interference more pronounced at the end of the pool? Easy. Vary the distance between the slits. 

So, first, welcome to Quantum Physics- this is the classic ‘split screen experiment’ that started that whole thing off, and that still lies at the very heart of it. (And, no, I don’t know much more about Quantum Physics than that.) Second, ‘diffraction’ is the phenomenon that explains the formation of the ripples in much of the far side of the divided pool. (Everywhere not in a direct line of sight to where the rocks are dropping.)

And now, last, let’s now imagine what happens to all those pretty, clear, phase interference patterns when the leading set of waves from the very first rock hits the closest edge of the pool on the opposite side to where rocks are falling. They bounce back. (And, as per a previous post, ‘become a phantom [or new] source.’) Further, now imagine the interference patterns. Not so clear. Not so pretty. Now imagine the waves hitting the second closest edge of the pool . And the third, the fourth. Now imagine none of those edges are the same hardness (reflectiveness.) Now throw a bunch of softish, irregularly shaped islands in the middle, and around the edges, of the pool. Now think about controlling, or even understanding, the patterns of phase interference. 

Such is car audio.

Wikipedia has a lovely animation that shows how simple phase disturbances generated via diffraction are distributed. Look for 'double slit experiment'. 


From the above, a few of things are clear: 1) any two speakers playing the same signal are going to generate phase interference. (Somewhere.) 2) The amount of this interference is very position-dependent. 3) My conclusion is steep crossover slopes (L-R 4) actually help, as they minimize the bandwidth where different numbers of speakers are generating the same signal at nearly the same amplitude. 4) Don’t overestimate diffraction. Phase interference happens when diffraction is not present.


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