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Sub level and how it effects phase alignment and crossovers
So this is a follow on from Steve Weigner (@captainobvious) and Erins you tube podcast type thing...
someone asked if adjusting sub level would effect phase between the sub and midbass driver...
the answer is... it depends how good your timing/crossover settings are and any phase issues in the area
let me post some pictures of smaart with examples if I can get them to work of my own system...
so I’ve found an example that’s useable, let’s run with it... we have a phase trace of my sub and my right front mid... so as you adjust timing the line pivots around an imaginary point to the far left of the picture
so this pic is the same driver with different delay settings, that’s it, no phase (allpass adjustment in a helix) so as you see the lower the frequency the less effect time delay has on it, this is what your altering at a given frequency when you adjust time alignment
imagine this is a picture of a slice across frequencys of phase at the listening position
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Re: Sub level and how it effects phase alignment and crossovers
So for my next pic this is the midbass added to the picture of the sub set to be in phase with the mid at the crossover region... which looking at these I’d make somewhere between 99.6hz where the crosshairs are and an octave further up around 200ish...
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Re: Sub level and how it effects phase alignment and crossovers
Good so far... ideally you’d want a big overlap of phase at various crossover points as increasing levels changes the crossover relationships
so with the sub on -6db you would end up with a crossover around 125, and as you can see we are in phase here and 1/3 of an octave below it, this would likely mean a good degree of summation at the crossover point...
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Re: Sub level and how it effects phase alignment and crossovers
So as we put the sub to -3db this is now putting the crossover right in the optimum place for the phase to be good above and below... this is where you’d put the crossover for maximum summation through the crossover and give a good impression of upfront bass, the relationship between the two drivers is as good as you can get given this phase relationship... this is good, you would get 6db of summation at the listening position and a good sense of the two drivers being as one and to be pulled to eye level on the dash
you can see the crossover in the bottom window is now moved up to approx 135 but this is a good place
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Re: Sub level and how it effects phase alignment and crossovers
Now with the sub level at 0db you can see the crossover has moved up some more to approx 150hz, this would still give a good summation through the crossover falling off a little bit at the top side where the responses phase drifts apart slightly (I normally aim for 30 degrees each way to get a good crossover...)
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Re: Sub level and how it effects phase alignment and crossovers
The level doesn’t change the timing, frequency to frequency will remain stable to the line in the phase graph for the sub will stay overlaying or running parallel to the midbass drivers trace
now to the rub, I have smaart and can do this because I can see phase live and tweak timing and phase to get it to overlay the midbass phase trace very well!
now then...
let’s try an extreme example... the settings of the first pics other sub angle, we would stand no chance of getting the crossover to work at 125-160 as per above... however imagin we wanted a crossover of approx 172... you adjusted your crossover so you got summation at a set sub level... you get 6db of summation but some funny dips either side (I don’t have a pic of this... but it would look mighty peaky... but this is an example so I’ll run with it...
so you set your crossover at 172 and get a good phase relationship at the freq and it drifts out either side... but you get 6db of summation so it’s good... or so you think...
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Re: Sub level and how it effects phase alignment and crossovers
Now let’s move the sub level up 3db and see what happens...
the crossover point now moves up to 183hz... you now have the phase correct below the crossover point, and drifting out of phase by 70 degrees at the crossover point and so you would then lose any sense of timing (even more above that) and the sub would likely pull to the subs location and you’d hear two different locations for each and they would seem out of time a fraction...
the same result would happen with a lower level away from the good phase crossover point...
the graphs all show the importance of good timing, I guess an easy way to check would be to move the crossover up 20hz and see if you still get 6db of summation... and the same for below... if you do then your timing is pretty good for the crossover...
the other thing worth noting is that in a reflective environment like a car you often get wrinkles and changes in phase as you move up the frequencys, sometimes delay settings are a bit off the charts with smaart, but you can sometimes get away with it by swapping phase and adding less delay or more delay and using a different delay... if I get chance I will show you just that, two good phase relationships... but with the drivers out of phase as we would think of it, but with different timings on each, one will normally be better than the other, but sometimes the phase plot is a gentle curve and you can do it both ways and get a good crossover
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Re: Sub level and how it effects phase alignment and crossovers
I hope this helps, I can’t recall who it was that asked the question... but if they are on here hopefully this helps... it’s always about timing and phase 👍🏼 Get that good and you can then often adjust a sub level and still get a good relationship at the listening position...
As an example I have two front subs and I have the phase and timing of the rear sub nailed... I can add 12db of bass at 20hz tapering down to 0db added around 80hz and it doesn’t pull back at all, only because the phase and timing at the listening positioning is nigh on as good as I can dial in... it drifts a bit at very low frequencys due to one being a 15 and one being a 10” (low frequencys often lag a little I think I have read somewhere more so with some drivers vs others...)
but at low frequencys due to wavelengths concerned it’s harder to get them in phase to a degree as the time has to be much larger and as long as you are within 60 degrees you still get a good amount of summation and don’t miss much...
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Re: Sub level and how it effects phase alignment and crossovers
That is some very nice work.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
I hope this helps, I can’t recall who it was that asked the question... but if they are on here hopefully this helps... it’s always about timing and phase [emoji1360] Get that good and you can then often adjust a sub level and still get a good relationship at the listening position...
As an example I have two front subs and I have the phase and timing of the rear sub nailed... I can add 12db of bass at 20hz tapering down to 0db added around 80hz and it doesn’t pull back at all, only because the phase and timing at the listening positioning is nigh on as good as I can dial in... it drifts a bit at very low frequencys due to one being a 15 and one being a 10” (low frequencys often lag a little I think I have read somewhere more so with some drivers vs others...)
but at low frequencys due to wavelengths concerned it’s harder to get them in phase to a degree as the time has to be much larger and as long as you are within 60 degrees you still get a good amount of summation and don’t miss much...
If you're using Windows 10 on that computer, you can press "Windows button"+Shift+S to take screenshots, full screen, just a window, or a smaller area. It's better than a phone pic.
Currently, I'm using a 160 hz low passed signal (varied by subwoofer level control) that is mixed into my midbass and is also low passed for my subs, it seems to alleviate some of these problems. What are your thoughts on that?
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Re: Sub level and how it effects phase alignment and crossovers
Very cool dumdum, thank you!
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
ckirocz28
If you're using Windows 10 on that computer, you can press "Windows button"+Shift+S to take screenshots, full screen, just a window, or a smaller area. It's better than a phone pic.
Currently, I'm using a 160 hz low passed signal (varied by subwoofer level control) that is mixed into my midbass and is also low passed for my subs, it seems to alleviate some of these problems. What are your thoughts on that?
Are you using virtual channels in a helix dsp? If you mean the bottom end of the midbass level also changes with the sub level then that will make the crossover remain the same as if the sub goes up by 6db so does the adjoining part of the midbass, if that’s what you’ve done it’s a good solution... it means your phase relationship will remain the same as it’s at the same point whatever the sub level is set to 👍🏼
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Re: Sub level and how it effects phase alignment and crossovers
Hey Dumdum, what version of Smaart are you using? Di or V8? Also what microphone(s) and I/O device if you are using one? I am very tempted to finally purchase my own copy and am leaning towards the di version.....
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Re: Sub level and how it effects phase alignment and crossovers
Also, for those that want to play with phase, you can do a little of that with REW and the alignment tool. To get to it, you need a newer version of REW.
Take IR measurements by pressing the measure button (not RTA).
Go to the ALL spl tab and click the gear icon.
Click the alignment tool.
Select the two drivers you want to phase align
Adjust the delay of one or the other to get the phase to match up around the crossover.
If negative delay, the speaker is closer than the other, if positive, it means that speaker is farther away than the other.
You can also see how the FR above is impacted by the delay. This isn't "real time" like Smaart, but you can at least take one measurement of each driver, use the tool, then make a change and see how it works. It used to be every change you had to take another measurement.
YMMV with this, I haven't had great luck using this and setting the delays suggested, the center image is always off when I do.....I am sure it is user error.
Note 1* Unfortunately the dsp I am using for this vehicle has maximum delay of 8ms :(
Note 2* Make sure if you are doing this, you set your sub level appropriately for measuring against a single speaker. My subs are 6db higher than a single speaker but with both mids playing the sub level crosses with both mids at 80hz.
Attachment 15062
This is the generated minimum phase version and levels adjusted (via rew and measurement action button), maybe this is what I need to use ???
Edit* just played around with this, it gave me the same time alignment of ~2.20s for EVERY driver except sub at 0...This would not give me a center image....
Attachment 15063
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Hey Dumdum, what version of Smaart are you using? Di or V8? Also what microphone(s) and I/O device if you are using one? I am very tempted to finally purchase my own copy and am leaning towards the di version.....
Smaart di2 which is a stripped down version of 8 with only two inputs and one transfer function at a time
i use a focusrite 2i2 and a Dayton mic currently, although I am considering an earthworks m23 :)
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
Smaart di2 which is a stripped down version of 8 with only two inputs and one transfer function at a time
i use a focusrite 2i2 and a Dayton mic currently, although I am considering an earthworks m23 :)
Only 1 mic?
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Only 1 mic?
For timing and phase aligning drivers I only want one mic... and for response/eq purposes I don’t use a static mic anyway so multiple mics aren’t required
I just ordered a nice shiny new isemcon emx-7150 :)
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
Are you using virtual channels in a helix dsp? If you mean the bottom end of the midbass level also changes with the sub level then that will make the crossover remain the same as if the sub goes up by 6db so does the adjoining part of the midbass, if that’s what you’ve done it’s a good solution... it means your phase relationship will remain the same as it’s at the same point whatever the sub level is set to [emoji1360]
MiniDSP 8x12, with a physical loopback for both front and subs (both to avoid differing delays from the extra pass through the dsp).
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
Are you using virtual channels in a helix dsp? If you mean the bottom end of the midbass level also changes with the sub level then that will make the crossover remain the same as if the sub goes up by 6db so does the adjoining part of the midbass, if that’s what you’ve done it’s a good solution... it means your phase relationship will remain the same as it’s at the same point whatever the sub level is set to [emoji1360]
I don't think the virtual channels in the Helix allow that, but I don't own one, I just read the manual. It would be nice if that were possible in any dsp's software without the extra external connections.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Also, for those that want to play with phase, you can do a little of that with REW and the alignment tool. To get to it, you need a newer version of REW.
Take IR measurements by pressing the measure button (not RTA).
Go to the ALL spl tab and click the gear icon.
Click the alignment tool.
Select the two drivers you want to phase align
Adjust the delay of one or the other to get the phase to match up around the crossover.
If negative delay, the speaker is closer than the other, if positive, it means that speaker is farther away than the other.
You can also see how the FR above is impacted by the delay. This isn't "real time" like Smaart, but you can at least take one measurement of each driver, use the tool, then make a change and see how it works. It used to be every change you had to take another measurement.
YMMV with this, I haven't had great luck using this and setting the delays suggested, the center image is always off when I do.....I am sure it is user error.
Note 1* Unfortunately the dsp I am using for this vehicle has maximum delay of 8ms :(
Note 2* Make sure if you are doing this, you set your sub level appropriately for measuring against a single speaker. My subs are 6db higher than a single speaker but with both mids playing the sub level crosses with both mids at 80hz.
Attachment 15062
This is the generated minimum phase version and levels adjusted (via rew and measurement action button), maybe this is what I need to use ???
Edit* just played around with this, it gave me the same time alignment of ~2.20s for EVERY driver except sub at 0...This would not give me a center image....
Attachment 15063
Mute one channel of input before the subs are mixed in to get an appropriate level.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
ckirocz28
Mute one channel of input before the subs are mixed in to get an appropriate level.
I much prefer to take six db off one or both if a pair off a mono amp... I use two front subs that are timed as one, the phase is nigh on identical to within +/-3 degrees at the listening position, so to match them to the mids I knock em down and adjust both channels delay as one and to get the crossover roughly where the phase is good for all three drivers (basically I lump the two subs in as one because their phase responses are so similar in my cabin at the listening position
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Re: Sub level and how it effects phase alignment and crossovers
Ooooh ooooh ooooh... so if the picture above is your sub and mids... then your sub is 180 out... however you would need to then adjust delays to get the two aligned, and not nesc in the conventional sense...
so you can see how the phase traces converge to the points between 20hz down to 120hz...
so if you put the sub out of phase the origin at 20hz will move down by 180 degrees... then add some delay to the rest of the system and the mids will then go from 20hz to 120hz downwards, and as the wavelengths are getting shorter the 120 will move down by more and you will have way better alignment through the crossover region I have drawn the red line as a guide as to where it should end up so you can see what it will look like and why it will track better through the crossover region
excuse the red line drawn on the screen of my iPhone 👍🏻
thats an excellent example of how you can do better sometimes with a polarity inversion and more or less delay...
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Re: Sub level and how it effects phase alignment and crossovers
Ideally you could remove delay from the sub, but if there is no delay on it you can then add delay to the midbass if that makes sense as it’s the exact same thing
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
Smaart di2 which is a stripped down version of 8 with only two inputs and one transfer function at a time
i use a focusrite 2i2 and a Dayton mic currently, although I am considering an earthworks m23 :)
Ya, I am thinking a dayton mic to start out (maybe calibrated from cross spectrum if they are actually in stock as it shows out of stock right now) and either the focusrite 4i4 or the motu m4, leaning towards the motu m4 but they are out of stock everywhere. So might fall back on the focusrite. The motu measures (not that it is audible) better than the focusrite and I like the look better.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Ya, I am thinking a dayton mic to start out (maybe calibrated from cross spectrum if they are actually in stock as it shows out of stock right now) and either the focusrite 4i4 or the motu m4, leaning towards the motu m4.
Good mic to start with... I use one currently until the new mic arrives... but point it up so it’s tip is between the ears and the mic is at right angles to the plain of tip to both speakers... otherwise you get way more level from the drivers side and way less from the passenger side... it matches the polar response and puts both drivers at 90 degrees to the tip and not 15 degrees and 50 degrees if you point it forwards ;)
I have a little jig Ive made that just hooks over the headrest legs and sits on, it means I can tune outside the car, jump in, move the mic, then put it back in the exact same place and tune a bit more, very simple, but works exceedingly well! :D
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Ya, I am thinking a dayton mic to start out (maybe calibrated from cross spectrum if they are actually in stock as it shows out of stock right now) and either the focusrite 4i4 or the motu m4, leaning towards the motu m4.
Good mic to start with... I use one currently until the new mic arrives with a focusrite 2i2... but point it up so it’s tip is between the ears and the mic is at right angles to the plain of tip to both speakers... otherwise you get way more level from the drivers side and way less from the passenger side... it matches the polar response and puts both drivers at 90 degrees to the tip and not 15 degrees and 50 degrees if you point it forwards ;)
I have a little jig Ive made that just hooks over the headrest legs and sits on, it means I can tune outside the car, jump in, move the mic, then put it back in the exact same place and tune a bit more, very simple, but works exceedingly well! :D
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
I much prefer to take six db off one or both if a pair off a mono amp... I use two front subs that are timed as one, the phase is nigh on identical to within +/-3 degrees at the listening position, so to match them to the mids I knock em down and adjust both channels delay as one and to get the crossover roughly where the phase is good for all three drivers (basically I lump the two subs in as one because their phase responses are so similar in my cabin at the listening position
If they are fed a L+R signal, and the test tone is mono, simply cutting one channel of input is quite easy, mute, measure, then unmute.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
ckirocz28
If they are fed a L+R signal, and the test tone is mono, simply cutting one channel of input is quite easy, mute, measure, then unmute.
Unless your channels are linked and unlinking/linking messes things up depending on order of what you press (Dayton 408 in this case). Trust me not worth that. Easier to just cut 6 for me. I just forgot to do it in those measurements when I was playing with rew’s phase stuff.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Unless your channels are linked and unlinking/linking messes things up depending on order of what you press (Dayton 408 in this case). Trust me not worth that. Easier to just cut 6 for me. I just forgot to do it in those measurements when I was playing with rew’s phase stuff.
You can't just mute one channel of the input without messing up something? I am talking about the input side of the dsp.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
ckirocz28
You can't just mute one channel of the input without messing up something? I am talking about the input side of the dsp.
Fair enough. You can. It might mess with things though if using a factory HU compared to just cutting -6 depending on factory EQ stuff.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Fair enough. You can. It might mess with things though if using a factory HU compared to just cutting -6 depending on factory EQ stuff.
I guess they both accomplish the same goal, I just prefer the single button method, that I just figured out 2 days ago. :) I found that when using the volume (sub level) control in my MiniDSP, the display in the software doesn't always update correctly, so I have to type in the correct levels, then muting as needed to avoid doing that again. Just recent experience still fresh on my mind.
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Re: Sub level and how it effects phase alignment and crossovers
Haha, I’ve just been called out by an “internet expert” on the other forum who said what I did in the first post isn’t possible...
sometimes I just have to laugh otherwise people would drive me mad...
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
For timing and phase aligning drivers I only want one mic... and for response/eq purposes I don’t use a static mic anyway so multiple mics aren’t required
I just ordered a nice shiny new isemcon emx-7150 :)
How did you make this decision? There are a lot of products on the market.
Ge0
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
Ya, I am thinking a dayton mic to start out (maybe calibrated from cross spectrum if they are actually in stock as it shows out of stock right now) and either the focusrite 4i4 or the motu m4, leaning towards the motu m4 but they are out of stock everywhere. So might fall back on the focusrite. The motu measures (not that it is audible) better than the focusrite and I like the look better.
Why do you need an M4? A Motu M2 will do the trick.
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Re: Sub level and how it effects phase alignment and crossovers
From my understanding of Smaart, if I ever expand to two (or three) microphones, I would need 3 inputs (two microphone and one loopback) and the m2 only has 2 inputs so would only be able to be used with one microphone and then the loopback.
The price difference isn't much either so that was my other reason.
For car purposes I would probably only ever need 1, but my wife also teaches high school theatre and has her own youth theatre company where the more microphones would be fun to play with in the bigger space.
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
From my understanding of Smaart, if I ever expand to two (or three) microphones, I would need 3 inputs (two microphone and one loopback) and the m2 only has 2 inputs so would only be able to be used with one microphone and then the loopback.
The price difference isn't much either so that was my other reason.
For car purposes I would probably only ever need 1, but my wife also teaches high school theatre and has her own youth theatre company where the more microphones would be fun to play with in the bigger space.
OK. Gotcha. You have a good point. BTW, I love my little Motu. It sounds good and has a nifty LED level meter in front :)
Ge0
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
dumdum
...
sometimes I just have to laugh otherwise people would drive me mad...
Be careful mate.
This...
In the second account, he was watching a donkey eat some figs and cried out: "Now give the donkey a drink of pure wine to wash down the figs", whereupon he died in a fit of laughter
.. is from here: https://en.m.wikipedia.org/wiki/Chrysippus
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Ge0
How did you make this decision? There are a lot of products on the market.
Ge0
the smaart users group had a post about measurement mics and the isemcon was declared by lots of people as king of sub 300 dollar mics, I wanted a small capsule (1/4” tip) mic which gives better off axis results, it can have more distortion at higher volumes but that’s a trade I am happy to make
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Re: Sub level and how it effects phase alignment and crossovers
Quote:
Originally Posted by
Jdunk54nl
YMMV with this, I haven't had great luck using this and setting the delays suggested, the center image is always off when I do.....I am sure it is user error.
Attachment 15062
Edit* just played around with this, it gave me the same time alignment of ~2.20s for EVERY driver except sub at 0...This would not give me a center image....
Looking at the image, it says "measurements do not have a timing reference". Would you not need a loopback with a timing reference to make sure you have absolute relative phase between the two drivers measurements? Then, the time shift method might work with good results?
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Re: Sub level and how it effects phase alignment and crossovers
I had an acoustic timing reference setup in the preferences and the measurement window. I am not sure why it was still saying that. I may have just choose measurements for this picture that didn't have that set up. It has been too long now and I use Open Sound Meter (free) or Smaart ($600) now for phase. MUCH MUCH easier!
https://www.caraudiojunkies.com/show...se-ETC-Program