# Let's Phac our Helix Dsp/Any Dsp - how to set Phase degree/AllPass



## Kalmangar (Jan 24, 2021)

so mosconi has a cool calculator of phase degree it's called phac(Phase Control shortcut and it is awesome.
this thing basically adjust the phase degree for getting better imaging and more precise stage.
u can learn more here:





EQ, T/A, isn't everything if u tune a system countless of times u will found everytime the instrument or the vocal doesn't sound natural something is a little bit off, even though everything else is perfect, the solution is for this situation.
most of the helix line up u have phase degree, most of the people don't use this option cuz they don't know how.
This is basically the secret sauce, the last 10% you can get from your system.
This is the closest u can get to FIR.
I was in shock after i tested this method, try and see for yourself, The stage got perfect and i mean perfect, all the sound became natural, the separation was spot on, it is the final destination.
This tutorial is an advancement tuning step, if u don't know all the other basics it won't help you.


So how we do it?
1. Download mosconi dsp tool.
2. Tune your system, Eq, Crossovers, Gains, Polarity check, ETC, (Don't T/A yet)
3. Open mosconi software and chose dsp with more Channels then yours dsp, my got 10 so i will chose aerospace 8/12, Chose work offline.
4. Import the setting from the Helix to the mosconi software - EQ and Crossovers.
5. this is the opne the freq chart
this graph calculate the phase shift after apply all the filter and the eq.









6. then chose the channel so u will see the phase and the phase which mark with red circles.
This is your starting point, before applying any changes, now you can close the cart.









7. The order of phase degree is L + R separate and,
the woofer are our reference.
we start with mids-> woofers
tweeters -> mids
sub -> woofers
we chose "Phase Shifter"
Chose freq in the left i found that 400-1000 works the best but it depends on you settings.









8. The phac window opens, we will attached the mid L(ch3) to woofer L(Ch5) and so on, here u can see we got 81 degree change
WRITE THAT DOWN, everything the phac calculate write it so in the end u will import it to the helix/your dsp.









9.Then ch4->ch6(mids R to woofer R), Write that down and continue with the order from step 7,









10. in the end the result should look like that:
All the even channels are the same and the odd channel are the same(1-2 degree doesn't matter)
* On the subs channel 7-8 i made a mistake u should correcrt the degree to the same, one of the woofer doesn't matter which so be aware, both 7-8 should be 49/59 doesn't matter which degree target u chose.









11. U can check the cart and see the phase is much better(I moddify the graph so u could understand better, after 180 degree the graph start from the top).
As u can see 100hz-3k is look much better alot closer to each other which mean better stagin,
compare this to the graph from step 6.









12. Import the phase degree u write down though the process we just did.
be aware degree bigger then 180 decrease 180
let's say the calculator give you 250 degree shift so you import in the helix 70(since 250-180=70)
Plus the helix tend to make steps of 5.6 degree so chose the closest one.









13. T/A the system, i found that the helix auto T/A works perfect after 3-4 tries, make sure to use a enough volume in the T/A to the bar will be green otherwise it doesn't work that well.
If u have another processor make it manual though REW of Smaart(Or if u short on money - OpenSoundMeter which is like smaart but free and have the thing u need for T/A) But pleaseeee don't use the lame distance caculator it will not give you anything other then disappointment , if you want top natch system make your T/A the right way.
It's what make nice system to amazing system, this is how we connect speakers and make then into sound, a real sound.
I know zapco HDSP also has the phase shifter and I'm think on chaning the dsp soon.
If u know how to tune and u miss something, this is it, the last mile.

If u have any corrections/suggestion feel free.
I don't know anyone else who does this trick other then me.
U will be amazed.

I wrote it before i got to bed so there are some mistake in the tutorial i will fix everything tomrow...


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## SkizeR (Apr 19, 2011)

2 things..

1) you are adjusting phase based off of the electrical signal. To be honestly, I really didn't read through all of this, but based on what it seems like you are doing, you may be correcting something that is just not there. 

2) you can (kinda) do this in the helix software already... see below


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## Kalmangar (Jan 24, 2021)

SkizeR said:


> 2 things..
> 
> 1) you are adjusting phase based off of the electrical signal. To be honestly, I really didn't read through all of this, but based on what it seems like you are doing, you may be correcting something that is just not there.
> 
> ...


1. it works for me... and all my people i know with Mosconi like the phac u can try it out.
it fix the phase shift made of the crossover and eq, plus it helps with the group delay so the result should be better sound stage.





2. I forgot about it i will check it but i don't think it will help u anyways.

Edit:
Checked it and it is not possible though the helix allpass display.

A demo of how it works with smaart:


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## cathul (Jul 2, 2018)

1. PhaC can work
2. The frequency you put in shouldn't be an arbitrary frequency, but the crossover frequency from the drivers you want to align, f.e. when aligning midrange to midwoofers you choose f.e. 300Hz., for tweeter to midrange you type in 3000Hz (when crossing at 300Hz and 3000Hz).
3. PhaC only calculates phase based on driver specific filters. 
3a. If you use the group eq to be able to use 30 bands of EQ for each driver PhaC will not work as it doesn't use the group eqs for calculations!
4. when doing it the "Mosconi way" you have to basically set T/A right at the very beginning (with safety crossovers for midranges/tweeters) with a binaural mic, otherwise results of PhaC may not be that good. I verified that with Frank Miketta.

Reason for 4 is the following:
Frank Miketta rightfully says if you set T/A it's a constant as it accounts for distances and speed of sound for both passband and stopband before you set the crossovers, i.e. the whole range of frequencies of the drivers. Crossovers and driver specific filters alter phase then in the crossover region, but passband phase stays the same, so you only have to adjust phase in the crossover region to get good alignment. All the builtin calculations are programmed for use of a binaural mic basically.

5. you really need to measure and verify it, 'cause sometimes it doesn't really work acoustically (ask me how i know!).


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## cathul (Jul 2, 2018)

SkizeR said:


> 2 things..
> 
> 1) you are adjusting phase based off of the electrical signal. To be honestly, I really didn't read through all of this, but based on what it seems like you are doing, you may be correcting something that is just not there.


And this is one of the reasons why PhaC doesn't always work. In theory it should, but sometimes it just doesn't.


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## Kalmangar (Jan 24, 2021)

cathul said:


> 1. PhaC can work
> 2. The frequency you put in shouldn't be an arbitrary frequency, but the crossover frequency from the drivers you want to align, f.e. when aligning midrange to midwoofers you choose f.e. 300Hz., for tweeter to midrange you type in 3000Hz (when crossing at 300Hz and 3000Hz).
> 3. PhaC only calculates phase based on driver specific filters.
> 3a. If you use the group eq to be able to use 30 bands of EQ for each driver PhaC will not work as it doesn't use the group eqs for calculations!
> ...


I respect everything u wrote and I know that already, but I found this is the best method.
I know the mosconi way, tried is several time,
and I know that they say t/a first but I found that after applying the Phac the center of the stage shifts so you need to t/a again.
and I know it meant for the crossover points but you can utilize it the align the phase as you wish and this works perfect, I don’t tend to follow the line, but try things for myself.

and for me and all myfriend the Phac works.
If you don’t know how to t/a or basic steps of tuning it won’t help you. But it give you some extra if you do.

5. When I will found free time I will try to measure it you are right, but I can ear it for sure.


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## dumdum (Feb 27, 2007)

Phac is purely electrical and not taking any acoustics into account or the influence of the cabin into account, so for me it’s a bit useless unless you happen to place crossovers in a minimum phase area ie the cabin has zero influence over the phase (highly unlikely)

it also assumes speaker phase is flat… it’s not and the midrange of the audio spectrum is always lagging from a driver and the sub bass and treble always leads

for want of a better description if you have a perfectly aligned two way home audio speaker the phase will generally look like a smiley face varying by 180 degrees at either end

So again phac doesn’t take the above into account


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## Kalmangar (Jan 24, 2021)

Yea I agree and this was my original though that it won’t help and you should adjust everything using Smaart which there you can see the impact of the acoustic environment on the phase very precisely.
But I’ve tried it and found that it works, so you can try calculate everything into you head, but something the realty is different.
I want some one with experience to try it and then check the impact it has.


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## dumdum (Feb 27, 2007)

Kalmangar said:


> Yea I agree and this was my original though that it won’t help and you should adjust everything using Smaart which there you can see the impact of the acoustic environment on the phase very precisely.
> But I’ve tried it and found that it works, so you can try calculate everything into you head, but something the realty is different.
> I want some one with experience to try it and then check the impact it has.


If your using smaart it’s far more accurate and you don’t need to calculate everything in your head, just adjust it live and place crossovers very accurately, the above that I mentioned are not an issue when using smaart
Jl tun allows you to do a similar thing and model all pass filters based on crossovers, and again in reality it doesn’t change the fact that it’s not reflected in the real world due to phase not being perfectly flat from a driver or combination of drivers


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## cathul (Jul 2, 2018)

Kalmangar said:


> I respect everything u wrote and I know that already, but I found this is the best method.
> I know the mosconi way, tried is several time,
> and I know that they say t/a first but I found that after applying the Phac the center of the stage shifts so you need to t/a again.
> and I know it meant for the crossover points but you can utilize it the align the phase as you wish and this works perfect, I don’t tend to follow the line, but try things for myself.
> ...


I tried it myself with the PICO 8/10 in my Mustang and afterwards i told Frank Miketta it didn't work as expected (at least for competitors).
Stage was good, no doubt, but stage was above the steering wheel when done as intended and this doesn't work out for a competition where the stage is expected to be in the middle of the dash (slightly left to the windscreen from a left hand drivers point of view). So i went back to my way of doing T/A with impulse responses and phase alignment via impulse measurements and stuff.

But i agree that this is a fast way to align phase, especially if you have a system like OpenSoundmeter or Smaart running on another screen to watch the changes in real time unlike like setting allpass filters by hand.


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## cathul (Jul 2, 2018)

dumdum said:


> If your using smaart it’s far more accurate and you don’t need to calculate everything in your head, just adjust it live and place crossovers very accurately, the above that I mentioned are not an issue when using smaart
> Jl tun allows you to do a similar thing and model all pass filters based on crossovers, and again in reality it doesn’t change the fact that it’s not reflected in the real world due to phase not being perfectly flat from a driver or combination of drivers


If using Smaart PhaC allows you to change phase just with a slider and in real time as the calculated allpass filters are applied in real time to the system.
When watching it in real time in Smaart this is a real good way to set the phase as desired in a very quick way. Way quicker than typing in different allpass filters with bandwiths and stuff like that.
So PhaC can work if you use it a bit outside of the workflow as intended by Frank Miketta.


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## Kalmangar (Jan 24, 2021)

Yea I know JL Tun is awesome this is based of smaart files, confirmed by a friend that works at JL, the licences to implante it cost them a lot.

and to cathul that is why I recommended t/a afterwards cuz the stage shifted from the center To the side from me. I’ve tried all Marks methods and I like him a lot, he is a crazy meniak, but this is just my personal preference.

and yes this is faster and more easy then tries various phase degrees.
If you have the time you can make it better? Absolutely, but this method seems to give me the best stage I have had plus u can done all the tuning in less than 2 hours with it.

anyways there isn’t any decent staging guide over here so I think it can be really helpful.


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## cathul (Jul 2, 2018)

Kalmangar said:


> 7. The order of phase degree is L + R separate and,
> the woofer are our reference.
> we start with mids-> woofers
> tweeters -> mids
> ...


If the phase on any driver is less than the driver you want to alter it to it wont work.
In your example if subs phase is -59° and woofers phase is -49° in phase you cannot use PhaC to adjust the sub to the woofer, but only the other way around, i.e. woofer to sub.


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## Kalmangar (Jan 24, 2021)

cathul said:


> If the phase on any driver is less than the driver you want to alter it to it wont work.
> In your example if subs phase is -59° and woofers phase is -49° in phase you cannot use PhaC to adjust the sub to the woofer, but only the other way around, i.e. woofer to sub.


yep this guide is not dummy-proof u need to use your brain in some cases.


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## dumdum (Feb 27, 2007)

cathul said:


> If using Smaart PhaC allows you to change phase just with a slider and in real time as the calculated allpass filters are applied in real time to the system.
> When watching it in real time in Smaart this is a real good way to set the phase as desired in a very quick way. Way quicker than typing in different allpass filters with bandwiths and stuff like that.
> So PhaC can work if you use it a bit outside of the workflow as intended by Frank Miketta.


The phase slider in helix is designed to give x amount of phase shift at the crossover, so your not guessing anything, helix software does it for you


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## cathul (Jul 2, 2018)

dumdum said:


> The phase slider in helix is designed to give x amount of phase shift at the crossover, so your not guessing anything, helix software does it for you


Same with PhaC.


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## dumdum (Feb 27, 2007)

cathul said:


> If the phase on any driver is less than the driver you want to alter it to it wont work.
> In your example if subs phase is -59° and woofers phase is -49° in phase you cannot use PhaC to adjust the sub to the woofer, but only the other way around, i.e. woofer to sub.


You’d simply add delay to the midbass and everything above equally in that case or adjust the crossover slope and freq of the subwoofer a touch or the midbass, in reality 10 degrees is very little to adjust


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## dumdum (Feb 27, 2007)

cathul said:


> Same with PhaC.


But we are talking about using smaart and other dsp softwares, why do I need phac, what does it offer me

with phac alone unless you can measure phase in the environment it’s not going to help as you will have to adjust after phac for the environment

phac can’t adjust anything automatically for the environment, so your left adjusting manually regardless


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## SkizeR (Apr 19, 2011)

dumdum said:


> Phac is purely electrical and not taking any acoustics into account or the influence of the cabin into account, so for me it’s a bit useless unless you happen to place crossovers in a minimum phase area ie the cabin has zero influence over the phase (highly unlikely)
> 
> it also assumes speaker phase is flat… it’s not and the midrange of the audio spectrum is always lagging from a driver and the sub bass and treble always leads
> 
> ...


This is why I just do it by ear and rta


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## Kalmangar (Jan 24, 2021)

SkizeR said:


> This is why I just do it by ear and rta


And this is why I made this guide - for people without trained ear.
Without 10 years experience.
Now they can make it too…


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## cathul (Jul 2, 2018)

dumdum said:


> phac can’t adjust anything automatically for the environment, so your left adjusting manually regardless


Same with Helix.
Look... i don't use PhaC myself most of the times. But all PhaC does in the end is set a 1st or 2nd order allpass filter with a frequency and in case of 2nd order a bandwith just like the variable phase slider in the Helix software does.
With Helix you move the slider and it automatically calculates the resulting allpass filter, frequency and bandwith, PhaC does the same, you move a slider and it automatically calculates the resulting allpass filter, frequency and bandwith for a frequency that you define. Only difference is, that Helix does this in 5.something degree steps and PhaC in 1 degree steps.
I already agreed with you that you should do that with some other software like Smaart or similar tools to minimize the amount of time needed, because you can see the result in the measurement software.


cathul said:


> When watching it in real time in Smaart this is a real good way to set the phase as desired in a very quick way. Way quicker than typing in different allpass filters with bandwiths and stuff like that.
> So PhaC can work if you use it a bit outside of the workflow as intended by Frank Miketta.


So i don't get it why you're arguing with me now.


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## SkizeR (Apr 19, 2011)

Kalmangar said:


> And this is why I made this guide - for people without trained ear.
> Without 10 years experience.
> Now they can make it too…


But as dumdum and I both said, you are "correcting" based on the electrical signal, which may not be correct acoustically.


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## dumdum (Feb 27, 2007)

cathul said:


> Same with Helix.
> Look... i don't use PhaC myself most of the times. But all PhaC does in the end is set a 1st or 2nd order allpass filter with a frequency and in case of 2nd order a bandwith just like the variable phase slider in the Helix software does.
> With Helix you move the slider and it automatically calculates the resulting allpass filter, frequency and bandwith, PhaC does the same, you move a slider and it automatically calculates the resulting allpass filter, frequency and bandwith for a frequency that you define. Only difference is, that Helix does this in 5.something degree steps and PhaC in 1 degree steps.
> I already agreed with you that you should do that with some other software like Smaart or similar tools to minimize the amount of time needed, because you can see the result in the measurement software.
> ...


I’m saying you can’t use phac alone as it’s pointless… the original post is about this.

phac is an automated system used for ‘correcting’ the phase response based on filters applied not a phase slider like in the helix, it’s a process that doesn’t work in a real world environment, I can’t say that I use the phase slider in helix either… occasionally I will apply an all pass filter, but that’s it as far as phase manipulation goes

the original post is about using phac with other dsps, not smaart. Most people don’t have smaart so phac is pretty much useless for me


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## cathul (Jul 2, 2018)

Well, PhaC is taking into account all the phase shifts from crossovers and driver filters, which the phase slider in Helix doesn’t. In this way PhaC might be more accurate after all. And as the OP outlined you need to transfer everything from the Mosconi to the Helix (or vice versa) to get accurate results, didn’t he?


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## dumdum (Feb 27, 2007)

SkizeR said:


> But as dumdum and I both said, you are "correcting" based on the electrical signal, which may not be correct acoustically.


This^^^ you may actually make it worse using phac as the environment may actually correct the phase without you knowing it


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## Kalmangar (Jan 24, 2021)

SkizeR said:


> But as dumdum and I both said, you are "correcting" based on the electrical signal, which may not be correct acoustically.


I heared that and I’ve answered to that already, check my comments…


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## oabeieo (Feb 22, 2015)

Kalmangar said:


> 1. it works for me... and all my people i know with Mosconi like the phac u can try it out.
> it fix the phase shift made of the crossover and eq, plus it helps with the group delay so the result should be better sound stage.
> 
> 
> ...


it does not !!! Fix phase from crossovers , it’s makes them worse

If you need a sim , I’ll prove it.


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## oabeieo (Feb 22, 2015)

Kalmangar said:


> I heared that and I’ve answered to that already, check my comments…


im new to this thread

oh please say again


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## Kalmangar (Jan 24, 2021)

Admins can u delete this thread?
Seems nobody try it and everybody sure that it is not working without trying…
So if it isn’t helpful delete it.


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## zak (Oct 2, 2007)

I think the comments from all in this thread will be helpful to anyone looking for the same info in the future. 
Dave


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## oabeieo (Feb 22, 2015)

Kalmangar said:


> Admins can u delete this thread?
> Seems nobody try it and everybody sure that it is not working without trying…
> So if it isn’t helpful delete it.


Sorry if you felt like that some of us were being condescending, we did not mean it like that at least I can’t speak for everybody but I didn’t.

around here there’s some very respected names in car audio sound quality. and these are the exact issues that ruffle some peoples feathers because you have engineers that are good engineers but they’re not audio people.

it’s cool to develop a product that can do something, but when it’s counterproductive to our end goals it sure makes trying to help people hard when theremoving backwards instead of forwards

APFs have uses , but not like that. The problem is it can make the passband have a good phase, but the stop band is a catastrophe.

and that’s the part I think the engineers break down and don’t realize that almost everything that we hear is a mix of all the speakers playing.

so when you have detrimental timing discrepancies in the interaction areas there’s no way to come back from that…

And then you hear these catchphrases like, all past filters fix crossover phase twist. Which is actually the exact opposite of what they do, they add more phase twist. They simply move in the wrong direction.

All passes are a good tool to have, just not for this…

so again sorry if you felt like your contribution was under attack, It’s not you it’s the premise and the idea of these bells and whistles that are put in the products that doesn’t work.


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## SkizeR (Apr 19, 2011)

Frank of Mosconi knows exactly what hes doing. That said, I just don't exactly see a point in doing this. Crossovers work properly when used as intended and implemented correctly. No need to correct phase for a tweeter down to 100hz lol


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## dumdum (Feb 27, 2007)

SkizeR said:


> Frank of Mosconi knows exactly what hes doing. That said, I just don't exactly see a point in doing this. Crossovers work properly when used as intended and implemented correctly. No need to correct phase for a tweeter down to 100hz lol


It doesn’t as far as I know, it adjusts the freqs at the top end of the cover by x amount of degrees, if the other end of the all pass filter effects the lower freqs that’s a side effect of the phase shift being tiny, the helix phase shift does the exact same in reality, uses a second order all pass filter

However it still doesn’t change the facts we’ve both mentioned in that it doesn’t take into account any phase shift induced by the vehicle so may improve things or make it worse

the only time it can be handy is if you have two crossovers on a narrow band with driver as they interact and change the phase by more than if they were spaced apart, but again this assumes the driver has perfectly flat phase in the first place

you can model this in jl tun’s newest release or see it also on the helix software if you turn the all pass filters on 👍🏼


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## preston (Dec 10, 2007)

These discussions always confuse me. Any guidance is appreciated - 

If I have two mid-ranges, and they both have proper response, but when played together create a dip, I can play around with an AP filter and try to fix that dip ? 
This is what I do now but its all guesswork, I just play around with a 1st or 2nd order (and inverted or not) AP of different frequencies on one channel until I get better summation and no weirdness elsewhere (and I always follow that up later with a listening test where I turn it on and off).
I understand I can see in Helix what the phase plot is doing when I do this but that it probably won't match what's actually happening in the car.

And moving the phase slider up is moving a 2nd order AP filter up in frequency from the crossover point (unless its the subwoofer channel when you are moving down in frequency, and the phase slider doesn't do anything on the woofer channels)

Is that more or less correct ? 

Where it gets complicated to me is if you've aligned phase between two mids, and now you bring in the woofers or mids. I can use the same trick in the x-over regions to match ie improve the summation between those 2 drivers. But if I apply an AP (or phase slider) between a mid and a woofer, I have now potentially messed up the phase between the mid's again.

Skizer I've heard you say you don't feel like you need a tool like Smaart that you can do it just using REW and summation.
I've never really learned how to use or understand the phase plots in REW and don't know if they're useful or if I need a loopback or more than my Umik-1 to use them.


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## zak (Oct 2, 2007)

preston said:


> Skizer I've heard you say you don't feel like you need a tool like Smaart that you can do it just using REW and summation.
> I've never really learned how to use or understand the phase plots in REW and don't know if they're useful or if I need a loopback or more than my Umik-1 to use them.


Agreed - this would be good to know.
Dave


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## oabeieo (Feb 22, 2015)

preston said:


> These discussions always confuse me. Any guidance is appreciated -
> 
> If I have two mid-ranges, and they both have proper response, but when played together create a dip, I can play around with an AP filter and try to fix that dip ?
> This is what I do now but its all guesswork, I just play around with a 1st or 2nd order (and inverted or not) AP of different frequencies on one channel until I get better summation and no weirdness elsewhere (and I always follow that up later with a listening test where I turn it on and off).
> ...


except the part your asking skizr something ,

if there’s a dip and an allpass helps fill the dip that’s only fixing a frequency responce issue

the problem is the time domain is corrupted. It no longer is in time with everything else especially the other side speaker

without Dirac or an fir that has arbitrary phase correction that can solve the real issue and keep a clean impulse , then it’s pointless and it’s better to just ignore the dip.

Just because the mic shows a dip don’t mean you have to try and fix it, the energy is still there.


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## preston (Dec 10, 2007)

So how/when would you apply an AP filter ? 
I've read some of your tuning posts and they usually leave me baffled so keep it simple


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## SkizeR (Apr 19, 2011)

preston said:


> So how/when would you apply an AP filter ?
> I've read some of your tuning posts and they usually leave me baffled so keep it simple


You can do it in situations as you have mentioned, but you really need to verify that what you are doing isn't just filling a hole in the response. Make sure it is actually making a positive change to what you are hearing. Is that frequency range smeared? If so, did it snap into place? you can also use them to phase-align speakers through crossovers.


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## cathul (Jul 2, 2018)

oabeieo said:


> APFs have uses , but not like that. The problem is it can make the passband have a good phase, but the stop band is a catastrophe.
> and that’s the part I think the engineers break down and don’t realize that almost everything that we hear is a mix of all the speakers playing.
> 
> so when you have detrimental timing discrepancies in the interaction areas there’s no way to come back from that…
> ...


If you talk to Frank Miketta about the theory it totally makes sense to use a tool like PhaC or the Helix phase control for exactly this purpose.
From the workflow point of view with PhaC you are correcting phase differences that are caused by crossovers through the different slopes, especially with odd order crossovers and driver specific filters that all have an effect on phase _after_ you have done the time alignment, and you do the PhaC on both side drivers, not only on one driver, and you do the PhaC on the crossover freqency, not an arbritary frequency that you see fit.
As allpass filters cause a frequency dependant delay they actually can work under these circumstances as you f.e. usually need to delay the highpassed speakers due to the phase shift caused by crossover slopes.
But again, it only works correctly if you're doing the time alignment as the very first step before setting driver specific filters including crossovers.

Problem is, you always have to measure if you really have an actual problem in this area after the car messed around with the acoustical phase due to all the reflections and stuff like that.

I personally listened to cars where the PhaC worked like expected and intended, but i also heared my own car where it didn't really work as expected and intended.


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## cathul (Jul 2, 2018)

dumdum said:


> However it still doesn’t change the facts we’ve both mentioned in that it doesn’t take into account any phase shift induced by the vehicle so may improve things or make it worse


One question (well, actually it's more than one...). Isn't this phase shift of the cars acoustics done to all drivers at the same time? F.e. in the area where you pass over the duty from midrange to tweeter?
If yes, the relative phase would stay the same even due to the induced phase shift by the car, right?
In this case, an allpass filter as created by either PhaC or the Helix phase control would still work as intended.


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## dumdum (Feb 27, 2007)

cathul said:


> One question (well, actually it's more than one...). Isn't this phase shift of the cars acoustics done to all drivers at the same time? F.e. in the area where you pass over the duty from midrange to tweeter?
> If yes, the relative phase would stay the same even due to the induced phase shift by the car, right?
> In this case, an allpass filter as created by either PhaC or the Helix phase control would still work as intended.


Only if both drivers were in the exact same place in the car literally, even 5” centre to centre will change the reflections which will then potentially influence phase

this is why driver positioning and crossover freq have to be chosen very carefully

Playing a midrange below beaming for example doesn’t mean you can mount it anywhere as some people would have you believe, an inch difference… (aiming will change off axis response and also move this centre to surface distance in smaller degrees so does need consideration also) up/down/back/forwards can make a decent sized difference to the response in both phase and also magnitude response 👍🏼


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## cathul (Jul 2, 2018)

dumdum said:


> Only if both drivers were in the exact same place in the car literally, even 5” centre to centre will change the reflections which will then potentially influence phase
> 
> this is why driver positioning and crossover freq have to be chosen very carefully


Yes, but these reflections will be the very same at all times, right? No matter if you set a crossover or driver specific filters, the reflections will be always the same and therefor relative phase will stay stable. It is not like the distance changes between drivers while listening.
Therefor this cannot be the answer. When i set the time alignment without crossovers (in theory that is, of course you need crossovers) the direct sound will all arrive in time, right?
When i set crossovers and driver specific filters arrival times will be changed, especially the lowpassed drivers will lag behind the highpassed drivers, no matter the always existing reflections. When i set an appropriate allpass filter on the highpassed speaker i can bring the arrival time back in time to the lowpassed speaker as the reflections will be stable.

Or is this way of thinking too simple?

Just trying to understand.


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## dumdum (Feb 27, 2007)

cathul said:


> Yes, but these reflections will be the very same at all times, right? No matter if you set a crossover or driver specific filters, the reflections will be always the same and therefor relative phase will stay stable. It is not like the distance changes between drivers while listening.
> Therefor this cannot be the answer. When i set the time alignment without crossovers (in theory that is, of course you need crossovers) the direct sound will all arrive in time, right?
> When i set crossovers and driver specific filters arrival times will be changed, especially the lowpassed drivers will lag behind the highpassed drivers, no matter the always existing reflections. When i set an appropriate allpass filter on the highpassed speaker i can bring the arrival time back in time to the lowpassed speaker as the reflections will be stable.
> 
> ...


Each driver will have its own reflections and phase issues to deal with, they will remain constant yes. The phase shifts and rolls round because of them… but each driver will be unique to its own phase shifts, not every driver will have identical shifts because they aren’t in identical places

move a mid up a pillar and it’s interaction with the car will shift in various ways

it’s why you should always put crossovers where both drivers have no big dips etc

in theory if phase was as it left the speaker then yes phac could work… however the environment skews phase very often and it’s not possible to put crossovers in a perfect textbook place

So we sometimes have to make small adjustments for the phase being out to bring it back in

it’s the environmental phase shift, no matter how constant… that phac can’t possibly predict or correct for, how can software with no idea of if mids are in upper doors or a pillars correct for phase being off or slightly out at the listening position? It also can’t predict the drivers own phase shift, be that big or small

Too many variables to predict with not enough information to predict them

Phase leads or lags with crossovers… it doesn’t change times of arrival or impulse response would change… I had this very discussion with the jl guys because it looks like timing will change, when in fact the phase rotates… it’s a hard concept to get your head around at times


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## oabeieo (Feb 22, 2015)

cathul said:


> If you talk to Frank Miketta about the theory it totally makes sense to use a tool like PhaC or the Helix phase control for exactly this purpose.
> From the workflow point of view with PhaC you are correcting phase differences that are caused by crossovers through the different slopes, especially with odd order crossovers and driver specific filters that all have an effect on phase _after_ you have done the time alignment, and you do the PhaC on both side drivers, not only on one driver, and you do the PhaC on the crossover freqency, not an arbritary frequency that you see fit.
> As allpass filters cause a frequency dependant delay they actually can work under these circumstances as you f.e. usually need to delay the highpassed speakers due to the phase shift caused by crossover slopes.
> But again, it only works correctly if you're doing the time alignment as the very first step before setting driver specific filters including crossovers.
> ...



Again , I’m a mosconi dealer , I tune a LOT of Aeros

it’s sorta works, it’s about the time that you spend about two hours fiddling with it and you get it to sound good, and then you leave the car and come back and turn it on again to a complete disaster because your ears weren’t ready for the mess that you caused…

so yeah like I said before, it makes the passband great, stop the band is a catastrophe (using phac calculator as frank designed)

I’m not a fan of really good coherence that’s narrow banded , then a mess outside of that area

I would rather sum the crossovers properly to have good allpass behavior (as a crossover network sums to be an all pass) and that’s the only time I want to move the phase in a minim phase system

as far as everything else as long as your magnitude is right that phase will fix itself. so there’s no point in trying to fix something that’s not broken when all you need to do is a better job at tuning…..


and as far as the dips again like I said the energy is still there! just because your microphone shows a dip in one spot don’t mean it’s not there , perhaps on the other side of the car…..

If you think about it like this plus take for example a 400 Hz all pass filter, with a Q around .5 or 1

The lagging side of that would be about 4 to 6 ms behind the leading side, that as a group delay why in the world would you want to add group delay 8-12 times!!! that’s an insane premise!

I can see sometimes using one way way way out of band on a driver that’s just not cooperating, and you have nothing left to do. But that’s A single driver!!! I would never ever ever add that to every driver in the networks on a multi way!

i’m surprised it doesn’t start reverberating with all of that wrapping going on!! Jesus Christ, it’s like , “ hey guys let’s intentionally add 8 more phase wraps , because it’s cool” 🤤🤤

Why would you make the compromise and trade should have one tiny part a little bit better in exchange for a very big part to be a complete disaster? Nicht verstehe!!!


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## oabeieo (Feb 22, 2015)

cathul said:


> Yes, but these reflections will be the very same at all times, right? No matter if you set a crossover or driver specific filters, the reflections will be always the same and therefor relative phase will stay stable. It is not like the distance changes between drivers while listening.
> Therefor this cannot be the answer. When i set the time alignment without crossovers (in theory that is, of course you need crossovers) the direct sound will all arrive in time, right?
> When i set crossovers and driver specific filters arrival times will be changed, especially the lowpassed drivers will lag behind the highpassed drivers, no matter the always existing reflections. When i set an appropriate allpass filter on the highpassed speaker i can bring the arrival time back in time to the lowpassed speaker as the reflections will be stable.
> 
> ...


Reflections can be a variety of diffraction (the worst) refraction , and a few other terms which I can’t think of atm (I’m drinking rn so this is off the cuf)

so it depends , most of the time as long as it’s not a compound reflection (a reverbant reflection ) then even simple eq can change the timing between frequencies that can alter the reflection to have different characteristics, which can be beneficial or detrimental….

You just kinda have to remember there almost is no such thing as direct sound in a car…. Most of the frequencies don’t exactly fit in a car…..

I would recommend using The wavelet, you will be able to see the time domain much clearer…

All you really need to do is use an acoustic timing reference and a single point measurement in the center of your ears and do a left and right and you can really see what’s going on… (of course zoom in because a car will never be above 200 ms as far as window size)

pretty much everything I’ve ever tuned was around 190 ms window size, to have a late reflection above 200 ms in a car is pretty much unheard of…

that being said it should be very very easy to see in the wavelet what’s happening…

I would recommend using a 15 cycle window below the Schroeder, and then a 4 to 8 cycle window above that, and then compare and you will see your time domain very clearly and it will become perfectly obvious where your reflections are.

of course it’s always easier to see this with the crossover‘s off and doing single driver measurements, The crossover will alter the time domain and you want that speaker flat baby flat!

You could also take impedance measurements, which is basically the density times the wave speed, z=Pv


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## dumdum (Feb 27, 2007)

oabeieo said:


> Again , I’m a mosconi dealer , I tune a LOT of Aeros
> 
> it’s sorta works, it’s about the time that you spend about two hours fiddling with it and you get it to sound good, and then you leave the car and come back and turn it on again to a complete disaster because your ears weren’t ready for the mess that you caused…
> 
> ...


That reads like all pass adds delay? They don’t add any delay in the signal, the impulse response doesn’t change at all

nor does it change through crossovers either, the phase rotation doesn’t effect time at all above the crossover


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## oabeieo (Feb 22, 2015)

dumdum said:


> That reads like all pass adds delay? They don’t add any delay in the signal, the impulse response doesn’t change at all
> 
> nor does it change through crossovers either, the phase rotation doesn’t effect time at all above the crossover


So , actually it does ,

but I think your just misunderstood

there’s a way you can see it , download JL TUN,

click on the crossovers icon , and it shows what you have going and it shows how many ms that LPF is set back ,

They sum to be an all pass , (that’s what it all passes a low pass in a high pass summed together) look at an all pass , the “low side” is one cycle out of time (for 2nd order) with the “high side” which isn’t out of time

that one cycle equates to a center frequency, depending how much phase (or radians) is in that circle , will dictate the delay of the low side

And it does affect the impulse , if it moves the timing it changes the impulse , whether it does it negatively or positively two different discussions
it’s obviously changing the timing somewhere or we wouldn’t be having this discussion lol

transfer function of an allpass here for example


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## oabeieo (Feb 22, 2015)

The wavelet , like I said , is a good way to see what’s going on 

this is my car for example, nice balance between left and right , linear phase behavior mostly all the way , a GD delay at 30hz and left side has a hole at 80hz


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## dumdum (Feb 27, 2007)

oabeieo said:


> So , actually it does ,
> 
> but I think your just misunderstood
> 
> ...


I was referring to you saying the all pass adds msec to the signal… it doesn’t or the arrival time would move if you applied it to freqs below where the signal is

it does change the impulse shape but not the actual arrival time of the direct sound above the all pass was my point, it literally effects the phase at the freq it’s at ‘if’ there is output at the freqs… it’s why applying a second order all pass at the subwoofer crossover point has zero effect on a tweeter which I’m sure I’ve seen you suggest before


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## oabeieo (Feb 22, 2015)

dumdum said:


> I was referring to you saying the all pass adds msec to the signal… it doesn’t or the arrival time would move if you applied it to freqs below where the signal is
> 
> it does change the impulse shape but not the actual arrival time of the direct sound above the all pass was my point, it literally effects the phase at the freq it’s at ‘if’ there is output at the freqs… it’s why applying a second order all pass at the subwoofer crossover point has zero effect on a tweeter which I’m sure I’ve seen you suggest before


I get ya now 

okay that makes more sense to me sorry dum


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## oabeieo (Feb 22, 2015)

dumdum said:


> That reads like all pass adds delay? They don’t add any delay in the signal, the impulse response doesn’t change at all
> 
> nor does it change through crossovers either, the phase rotation doesn’t effect time at all above the crossover


Exactly, above the crossover…. 
below it is a delay, same with an all pass…. The low side past quadrature is a GD and it’s constant.

so an out of band APF below the passband of a driver , okay so what , depends how out of band were talking , if your trying to move meaningful phase in the passband , it can’t be that far off (like you said about the tweeter)

if it’s not that far off, then most likely it’s in the stop band in the interaction area…..which puts out out of time with the driver below it in the lower stop band…. That’s audible.

I mean, if your only worried about the passband , then by all means. I’ve tried it on a number of cars and wasn’t impressed

there was a tundra that it worked just ok on the right door only…. But not all the speakers

it did make the doors work nice together, but still had artifacts that made me like …… think, “is this really worth it” …….and I removed it and worked around it. It was causing serious issues with dash midrange on the same side…..

Maybe , just not my cup of tea perhaps


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## preston (Dec 10, 2007)

oabeieo - in this thread you seem to be arguing against using AP filters in almost all scenarios 



> I would rather sum the crossovers properly to have good allpass behavior (as a crossover network sums to be an all pass) and that’s the only time I want to move the phase in a minim phase system
> 
> as far as everything else as long as your magnitude is right that phase will fix itself. so there’s no point in trying to fix something that’s not broken when all you need to do is a better job at tuning…..


among other quotes in this thread.

And yet in this previous post of yours, it seems you are saying the opposite, that applying an AP at the x-over frequency and/or using odd xover slopes is a beneficial tool. 









Crossover Phase Shift Explained


I have been asked by a bunch of you to post some illustrations. Here are some things I hope can help. 1st off. The idea of using an APF to get rid of phase shift from a crossover is complete nonsense. The phase shift of the all pass goes in the wrong direction. An out of band all pass can help...




www.diymobileaudio.com





Which is it ?

(I have to vent and admit I've never been so confused as I am about this phase stuff. To me phase is just a frequency dependent displacement in the time domain when a waveform is compared to itself or in our case a similar waveform from a different speaker. It seems to me by the time phase goes around a 360 circle you are now completely out of place with the original waveform unless we are talking about symmetrical sine waves, which in the "learn about phase" tutorials, we always are. But a music waveform isn't a sine wave and while it might be symmetrical for one cycle, it doesn't repeat itself so it seems to me that any phase changes would mean everythign is out of whack. which isn't the case since we're still listening to music. I actually have a EE degree from 1989 and currently work as a software engineer and often think about things in a pretty abstract manner and yet even reading all these posts and watching the videos I still can't seem to create the correct mental image to visualize this stuff, especially the 360 rotation thing. But I have at least decided to purchase some equipment so I can measure and see the phase in my system because after reading all this ******** I will never be able to enjoy listening to it again until I do ha ha).


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## oabeieo (Feb 22, 2015)

preston said:


> oabeieo - in this thread you seem to be arguing against using AP filters in almost all scenarios
> 
> 
> 
> ...


man sorry for confusion

so an APF is fantastic when it’s needed

so , think about what an APF does, it’s a shift from 0 to -360 for second order

boy that sure does seem a lot like a crossover, because it is like a crossover, it changes phase in the exact same manner. Because a crossover a HP and a LP summed together makes an AP2

so why would we want to add more crossover phase shift? We’ll never,

however, using an APF to mimic a crossover so all speakers share the same phase shift is a good thing.

if all the speakers in the system share the same GD it’s mostly inaudible, so in some of my posts i recommended it…. For example

if you can’t cascade crossovers and do the same phase heavy crossover on all drivers as your midbass HP , because dsp don’t allow more then 1 HP per channel but has AP, you can add a AP2 and replicate an LR4 for example phase shift and add the cascade that way

that is one example of proper use of an APF

adding An AP midband or even slightly out of band on one driver in a multi way, like a right midbass for example, and not do it to the left or all the speakers , that is detrimental to the time domain. It might make one part better while messing other parts up

a phase shift by itself is no big deal, it’s when it’s summing with other things that it can wreak havoc.

everything should have the same amount of phase shift caused by AP or you sorta shouldn’t use them….. with rare exceptions,

1 rare exception is a pattern flip from a upright SUV with a midbass low in door , where there is a 180° polarity flip mid band only on one side,

the use of a 1st order AP1 (and a polarity flip) in that scenario could easily fix the problem.

So I apologize for the confusion…

it’s these catchphrases I keep hearing over and over again in my life and on the Internet that drive me crazy because it’s wrong, like , “ using an all pass filter to fix crossover phase shift” (that sir is an impossibility) they both move the same direction in time, The allpass filter would have to be played backwards for that to work…

you would simply need a finite impulse filter (fir)
To complete that task…..

It’s probably partially my fault, because in the past in some of the threads that I may have authored before I knew better, I may have given the wrong ideas that would’ve been about 2016 and older I’m guessing maybe maybe 2017 (I can’t remember)

regardless, it might also be that some folks just think and do one minute of study on and all pass filter and see it “moves phase” and starts down the path I was 10 years ago….

I love helping people, so I guess it’s sort of tough love for me coming out so strongly against them (the use of APs) because I highly highly highly caution the use of one without knowing exactly what you’re doing

Hope that helps and makes sense


and your circle thing , don’t forget the TIME it takes to travel that circle , if it’s a LOW frequencie , it could take many ms to travel (in what we do)…. So one side of the “circle” will be BEHIND the other, that is a GROUP DELAY…. which subsequently puts you out of time with everything else in that portion of the circle and everything before the circle (logmarithically speaking….. if your reference is the wrapping from a constant delay) 

it’s audible, that’s what matters, it needs caution, electrically on a scope, engineers only like to show the ultra narrow band benefit…. Speakers play and are audible way out of band…. Even the most minute changes in air can affect ajacent drivers.. meaning , even if it’s -10db down , it’s interacting a lot, once it’s like -30 to -50db down interaction becomes un-influential.


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## cathul (Jul 2, 2018)

Music is a lot of sine waves at once, which then, when overlayed, creates a not like sine wave looking wave, but still, technically it is all sine waves.
And these waves can be out of phase if played by two speakers, be it left+right or left midrange+left tweeter.
So getting the phase in order is really important in my opinion.
Time aligning the drivers before doing everything else makes sure, that every single frequency arrives at the listening position at the same time (plus/minus a few fractions of a milliseconds).
Adding driver filters to the aligned drivers creates phase problems as every single filter alters the phase at the listening position.
With the LR24dB filters the lowpassed driver is now one cycle behind in phase, but still in time.
Having a tool to bring them back in phase without altering the time alignment is now a handy tool, and allpass filters do exactly that.
If you have no allpass filters you can do the phase alignment also with time alignment, but time alignment then puts every frequency above or below the crossover area, depending which driver you are putting additional delay to, out of time with the frequencies of the other driver, except for the crossover region that is, because there you are back in phase and still in time.

And this is what PhaC (and the Helix phase adjuster) tries to do. It gives you an easy way to manipulate phase at the crossover region without affecting the time alignment of the different drivers.
Debate is on the technical implementation of the tool, not that allpass filters don't work.


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## cathul (Jul 2, 2018)

oabeieo said:


> adding An AP midband or even slightly out of band on one driver in a multi way, like a right midbass for example, and not do it to the left or all the speakers , that is detrimental to the time domain. It might make one part better while messing other parts up


That's not how people should do it.
If you have a phase problem, you should make the good phase side similar to the bad phase side, not the bad phase side similar to the good phase side (as this is almost always impossible to do due to the environment). Result is same bad phase on both sides, which then negates the negatives that might occur when using allpass filters on one side only.
Ideally you wouldn't need an allpass filter, but a car is not an ideal environment, so sometimes you just have to use them.


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## preston (Dec 10, 2007)

Thanks those are helpful explanations.


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## dumdum (Feb 27, 2007)

cathul said:


> Music is a lot of sine waves at once, which then, when overlayed, creates a not like sine wave looking wave, but still, technically it is all sine waves.
> And these waves can be out of phase if played by two speakers, be it left+right or left midrange+left tweeter.
> So getting the phase in order is really important in my opinion.
> Time aligning the drivers before doing everything else makes sure, that every single frequency arrives at the listening position at the same time (plus/minus a few fractions of a milliseconds).
> ...


All pass filter DO NOT correct the rolling around of phase in a 24db slope crossover, they can’t, only fir filters can do that

an all pass and a crossover roll the phase the exact same way, one doesn’t counter the other, @oabeieo is accurate on that part…

If a 24db crossover made the signal one wavelength out of phase adding an all pass can only ever make it more out of phase not bring it back onto phase, yet it doesn’t

that’s not what phac does and not how it works

also all pass and a 24db crossover doesn’t add delay above it, I thought it did, however if you watch the impulse response the timing of the signal doesn’t change, the phase does alone, it’s a big thing to get your head around

I asked the same thing of Nicolas Ames of jl and he showed me with a real signal and applying an all pass to it while measuring its impulse response


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## cathul (Jul 2, 2018)

So you are pretending that it is impossible to have two drivers in phase and time in the crossover region and their passbands, right? Because if the lowpassed driver is lagging one cycle after applying the crossovers to both drivers they are in phase, but one cycle out of time. How do you solve that?
Just trying to understand.


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## SkizeR (Apr 19, 2011)

oabeieo said:


> man sorry for confusion
> 
> so an APF is fantastic when it’s needed
> 
> ...


I made it this far. No offense, but jesus christ you are horrible at explaining things. 

@preston .. do not look at all pass filters like crossovers. It will just confuse you even further. All an all pass filter does is change position/direction of the cone in its cycle in a specified frequency range.


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## dumdum (Feb 27, 2007)

cathul said:


> So you are pretending that it is impossible to have two drivers in phase and time in the crossover region and their passbands, right? Because if the lowpassed driver is lagging one cycle after applying the crossovers to both drivers they are in phase, but one cycle out of time. How do you solve that?
> Just trying to understand.


I was very specific and I didn’t say that… you can’t undo phase rotation in a crossover by using an all pass which adds more phase rotation, an all pass is positive phase rotation, and a crossover is positive phase rotation, one cannot undo the other, they both induce the same phase rotation

take the crossovers off of a mid and tweeter and measure impulse response then align them, now apply a low pass and a high pass respectively and check the timing again… does it change the timing? This is how Nicolas demonstrated it to me from memory, if what your saying is true the tweeter impulse would then move to a later point in time corresponding to a full wavelength worth of time, so if it was a 2.5khz crossover the time period of the time shift would be 0.4msec, but you won’t ever see that time shift with impulse response

for example if you have a tweeter and it has a 2.5khz crossover on it that crossover does not effect the timing of 8khz leaving the driver, toggle it on and off and you will not see 8khz move if you play a tone and measure it’s impulse response and arrival time, toggle the crossover on and off and it will not change in time

You are associating phase change with timing, you get phase shift through a crossover, but it doesn’t delay everything above the crossover

timing can be related to phase, changing time alignment effects phase variably depending on frequency, but changing phase doesn’t effect timing

It why if you change the polarity of a driver and watch it’s impulse response the impulse just flips horizontally. But it’s arrival time doesn’t change if that makes sense

all pass, polarity swaps and crossovers change the phase of the first arrival at the mic of there effected band if measuring impulse response, but not it’s actual arrival time

try it… play something and measure it’s impulse response and then swap polarity and see if the impulse changes in the time domain… it won’t, but if your theory were true it would change the time of arrival at the mic by half a cycle… of all freq which would make for a very out of time freq band


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## cathul (Jul 2, 2018)

Ok, understood...
Another question.
When having a 3-way system with a typical midbass crossed at 60Hz highpass and 300Hz lowpass, do we need to account for the phase shift caused by the lowpass of the midbass in the highpass of the midbass region? When calculating the phase it seems that even with LR24dB filters in the highpass region you have a difference in phase of almost 30 degrees, or even more if you cross the lowpass lower (like in BMWs f.e.).


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## AudioGal (Oct 16, 2019)

I am not going to enter into the discussion another than to offer a resource that should help clear up many points about all pass filters. Meyer Sound has a video about this exact topic and its practical implications including how All Pass impacts phase rotation and delay throughout the audio band including orders, Q selection and the effect center frequency selection has on all those parameters. I found it very informative and a go to resource.

I hope you do to, enjoy!


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## oabeieo (Feb 22, 2015)

Here’s a couple pictures of what I was saying in the tun app
How it shows the group delay of the cross over the low pass has a 6ish ms GD from 0 to 80hz with an 80hz crossover and a bump inGD at 63

so the entire Lowpass is delayed from the high pass, that is a delay caused by the crossover, and it’s constant, constant delays show up in log as a wrap, that’s the circle, the time , 6ms of 80hz isn’t a lot, and it’s almost nothing to 20hz which has like 25ms +/- (can’t remember exactly ) in its cycle

rhe High pass in its crossover starts to delay and becomes more delayed as it rolls off and sums with the low pass

they sum as an all pass (if you did your job properly doing them) so an allpass would behave the same in time domain all things being equal 

any way pics show it


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## Kalmangar (Jan 24, 2021)

This thread became discussion from a guide, I feel so violated. 😰


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## oabeieo (Feb 22, 2015)

Kalmangar said:


> This thread became discussion from a guide, I feel so violated. 😰


that’s how things work at DIYMA, it’s a chat fourm , sorry man but it’s actually packed with good information.


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## Kalmangar (Jan 24, 2021)

oabeieo said:


> that’s how things work at DIYMA, it’s a chat fourm , sorry man but it’s actually packed with good information.


I’m kiddin, does it really sounded serious? 😮
I used to mange dozens of forum I know how things work..

The thing that really funny is that everybody has like daddy issues with APF, wtf it just a tool use it if it fits you needs, the APF can help on a lot of chases.


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## oabeieo (Feb 22, 2015)

Kalmangar said:


> I’m kiddin, does it really sounded serious? 😮
> I used to mange dozens of forum I know how things work..
> 
> The thing that really funny is that everybody has like daddy issues with APF, wtf it just a tool use it if it fits you needs, the APF can help on a lot of chases.


no worries buddy , thank you for understanding then

And yes it can be helpful, but I would dare to say
10 times out of 9 , better tuning would resolve most of any issues. Lol 😝😋🤪


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