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Equalizer APO, REW and Rephase WOW!
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Old 19th March 2018, 09:57 PM   #91
KaffiMann is offline KaffiMann  Norway
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It is not that "low frequencies are more affected". All filters are equally affected. It is just easier to notice it on subs because the wavelengths are longer. Once you know what to "hear for" you can find it on higher frequencies too.

I have not found a steep filter that does "all the magic" with no bad sides. I go mostly 48db/oct under 7-900hz, maybe 24db/oct up to nearly 2khz, but often end up with 12db/oct bessel.
Combinations of different topologies and orders/slopes for HP/LP can work really well. I like Butterworth combined with Bessel, got to mix'n'match the frequencies a bit.
Legendre-Papoulis filters can be fun to try, they are steeper than Butterworth.
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Old 19th March 2018, 10:32 PM   #92
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by 33Polkhigh View Post
Kaffiman, thanks. I wouldn't go steep on a sub anyways since low frequencies are more affected and overlap isn't an issue (unless you have distortion problems). Do you think a variable slope that gets steeper and steeper would help with the potential ringing? I was looking into this.
1st or 2nd order Neville-Thiele linear-phase FIR as offered eg by the Acourate(tm) toolbox is a very good compromise in that it has infinite steep slopes yet the "knee" is very soft (hence considerable overlap) and correspondingly the (off-axis) ringing is quite moderate for such a steep filter.
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Old 19th March 2018, 11:05 PM   #93
33Polkhigh is offline 33Polkhigh  United States
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Quote:
Originally Posted by KSTR View Post
1st or 2nd order Neville-Thiele linear-phase FIR as offered eg by the Acourate(tm) toolbox is a very good compromise in that it has infinite steep slopes yet the "knee" is very soft (hence considerable overlap) and correspondingly the (off-axis) ringing is quite moderate for such a steep filter.
Thanks I will look into it or try to emulate it with equalizer apo.

Question, does ringing only occur off axis? I thought it is signal timing issue?

Also why do some crossover models show them meeting at -6db? I thought to sum flat all crossovers must meet at -3 db (coherent source)?
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Old 20th March 2018, 12:14 AM   #94
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by 33Polkhigh View Post
Thanks I will look into it or try to emulate it with equalizer apo.

Question, does ringing only occur off axis? I thought it is signal timing issue?

Also why do some crossover models show them meeting at -6db? I thought to sum flat all crossovers must meet at -3 db (coherent source)?
When the transfer function are in phase (0 phase offset between ways, like in a Linkwitz-Riley) then they are 6dB down at the intersect, both drivers supply one half of the output, their outputs add directly (scalar addition). If there is phase offset, the intersect is at a higher level because the outputs add less than perfect. For a 90 offset (as seen with eg a Butterworth crossover) each way supplies 0.72x of the output (vector addition). Any phase offset (except a straight 180) is possible but beyond 120 the addition is destructive, each way supplies more that the sum. Not very useful, for a variety of reasons.

A proper crossover is designed to sum to flat frequency response and the ringing of the ways fully cancel at least on-axis, off-axis the cancelling isn't perfect mainly because of the time-of-flight differences. There is no way to correct this electrically.
This is not to be confused with the typically non-zero phase response of the total (summed) transfer function which adds another kind of "ringing". The higher the order the stronger the phase shifts and corresponding smearing of the transient response. But this is a one-dimensional effect and can be corrected by applying an overall phase correction to give a linear phase response.
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Old 20th March 2018, 03:10 AM   #95
33Polkhigh is offline 33Polkhigh  United States
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Quote:
Originally Posted by KSTR View Post
When the transfer function are in phase (0 phase offset between ways, like in a Linkwitz-Riley) then they are 6dB down at the intersect, both drivers supply one half of the output, their outputs add directly (scalar addition). If there is phase offset, the intersect is at a higher level because the outputs add less than perfect. For a 90 offset (as seen with eg a Butterworth crossover) each way supplies 0.72x of the output (vector addition). Any phase offset (except a straight 180) is possible but beyond 120 the addition is destructive, each way supplies more that the sum. Not very useful, for a variety of reasons.

A proper crossover is designed to sum to flat frequency response and the ringing of the ways fully cancel at least on-axis, off-axis the cancelling isn't perfect mainly because of the time-of-flight differences. There is no way to correct this electrically.
This is not to be confused with the typically non-zero phase response of the total (summed) transfer function which adds another kind of "ringing". The higher the order the stronger the phase shifts and corresponding smearing of the transient response. But this is a one-dimensional effect and can be corrected by applying an overall phase correction to give a linear phase response.
I don't understand phase and crossovers as well as you do. It sounds like you're saying that you can't just use a decibel (logarithmic) calculator to sum the slopes of the crossover.

It sounds like your saying the change in phase changes how the slopes sum. IOW in phase will have mutual coupling and out of phase will have total cancellation.

So then what's the best way to set a slope for a driver using equalizer apo? I believe its a minimum phase equalizer. So then I have to calculate phase? This almost seems irrelevant because at every position other than equal distant between the two drivers there is going to be a different phase relationship?

The set-up I have now (I use the equalizer slopes to make a steep slope crossover) seems to sound good, but some people here have questioned what I am doing is really a legitimate crossover or an out of phase mess

Sorry for all the questions and thank you for clearing things up.

Last edited by 33Polkhigh; 20th March 2018 at 03:13 AM.
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Old 11th April 2018, 09:52 AM   #96
arcgotic is offline arcgotic  Romania
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Anybody here has experience with active crossover done with EqAPO and second with VST using ASIO layer?
Considering the same FIR filters loaded in EqAPO and VST+ASIO, is there a difference in perceived sound quality?
Thanks!
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Old 4th May 2018, 06:45 PM   #97
ronkuper is offline ronkuper
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Great thread guys!

Just found it now after playing with eAPO for software-based system-wide bass management (not doing BM upstream so that I can then use Room-Correction software to correct the sub channel).

Questions -
1. I used the LR-4 coefficient filter provided here to replace the built-in eAPO filters. I saw that it takes the sampleRate as an input. Isn't that a bit problematic for different content?

2. Is rePhase relevant for sub integration as well? Will it replace the need for LR-4/HPF/LPF filters in eAPO? Will it replace the need for summing?

3. Regarding summing for 2.0 --> 2.1 - is SUB=0.5R+0.5L correct? I see how this is good for a sine wave of equal level played on both channels but what if the channels contain uneven Stereo bass content? Is that an issue/limitation of using a subwoofer? Any alternatives? rePhase?

4. Any tips to setup/research/measure for Sub integration for Stereo music with eAPO/REW/rePhase?



Quote:
Originally Posted by jiiteepee View Post
Equalizer APO, REW and Rephase WOW!


LP | HP+LP | HP

Code I use is taken from here.
The pic is from eAPO analyzer or a different software? If it is from eAPO, how did you combine the channels on the graph?


A small contribution -

1. eAPO is generally deployed as an APO, meaning it passes the windows OS Mixer. There is another option, as eAPO also implemented support for VoiceMeeter API client which can used in exclusive mode end-to-end thus bypassing the OS Mixer, I shared details here: HOWTO: VSTs & Loudness & Virtual Zones & Exclusive mode & System/Notifications/Other Apps Sounds - All together! Oh and Dirac is there too ^_^8 - Roon Software - Roon Labs Community

It has some quirks, like Loudness filter not getting the correct volume, etc. If there's a C++ person in the crowd maybe he can take the challenge

2. Haven't seen mentioned in this thread but if moving eAPO stage to pre-mix an inputChannelCount condition can be used to set different configs automatically based on channel count:
Code:
Stage: pre-mix
If: inputChannelCount == 2
    # Upmix 2.0 to 2.1 with Crossovers 
ElseIf: inputChannelCount == 6
	# Bass Management for 5.1 content (10dB LFE, summing, etc) 
EndIf:
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Old 5th May 2018, 07:40 PM   #98
jiiteepee is offline jiiteepee  Finland
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Quote:
Originally Posted by ronkuper View Post
...

Questions -
1. I used the LR-4 coefficient filter provided here to replace the built-in eAPO filters. I saw that it takes the sampleRate as an input. Isn't that a bit problematic for different content?

...

The pic is from eAPO analyzer or a different software? If it is from eAPO, how did you combine the channels on the graph?
#1 It depends.
IIRC, EqualizerAPO don't recognize samplerate change done through system options or through software features ... and worst is that you can't see which samplerate EqualizerAPO uses (I have suggested Jonas to add support for samplerate change and a (Editor) GUI field for to display the current fs ... so maybe someday ...).

Captures from Config Editor and the final pic is combined using Windows Paint (there's this transparent option when inserting images).

Last edited by jiiteepee; 5th May 2018 at 07:42 PM.
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Old 6th May 2018, 04:29 PM   #99
ronkuper is offline ronkuper
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Asking again specifically (TLDR), for Stereo music is this summing formula correct?
Code:
SUB=0.5R+0.5L
(Taken from eAPO forums)

I see how this is good for a sine wave of equal level played on both channels but what if the channels contain uneven Stereo bass content?
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Old 22nd May 2018, 09:50 PM   #100
jiiteepee is offline jiiteepee  Finland
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FYI, I prepared Linkwitz Crossfeed -preset for headphone use - Equalizer APO / Discussion /
General Discussion:Linkwitz Crossfeed preset


Is that 700Hz (suggested in paper) as corner/cutoff frequency too low value or OK?
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