Optimizing subwoofers and integration with mains: multi sub optimizer - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 527 Old 08-17-2015, 10:25 AM - Thread Starter
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Optimizing subwoofers and integration with mains: multi sub optimizer

This software is made for all of those who have trouble setting up their subs. It has been developed by Andy C, also member here. It allows for automatically tweaking the settings of all subwoofers and mains, based on inroom measurements of all individual subs/speakers (multiple positions). The program can be downloaded here. If the chm file shows up empty, please read this. The help section can also be found here. Andy will continue to work on the program and add new features. Opening a .msop file (multi sub optimizer project file) created with a newer version than your own, might not work properly.

I have used it in my own DIY project in which i use 4 subs for a Geddes style multi sub setup. The room is 6x4,2m, well treated for >200Hz but low LF damping due too stiff construction. I had a real hard time getting the subs to play along with each other. All subs have their own dsp channel and amplifier. Just too many degrees of freedom (gain, delay, high/low pass settings, parametric EQs). Spent countless hours without satisfying result.



After entering all values into my Hypex DSPs, i did a measurement to check the accuracy of the simulation and it turned out quite accurate.

Main listening position simulated and measured (had to move mic in between):



Position 5 (left mic standing at same spot):



I'm very pleased with the results, it worked better for me than doing it by trial and error myself. The LF sounds well controlled now and when needed powerful. And there's much less variation when you walk through the room.

The attached image (multisub_optimizer) shows the amplitude response by the red trace at the main listening position. The four other blue traces are the secondary and tertiary positions .
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post #2 of 527 Old 08-17-2015, 11:29 AM
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When I first saw that plot of the main listening position, I thought, "Aargh! Something's wrong!". Then I realized it was 1 dB/div . I took your plot that has all 5 positions on it, then reduced the lower limit of the graph until I got 5 dB/div. Then I put trace offsets on all but the main listening position (I assume that's position 1?). These offsets were in 10 dB increments to set them apart. I ended up with this graph:



Since you have four channels in which there are filters with variable parameters, you can get away with four listening positions, maybe eliminating position 5. I haven't tried this yet with your project, as I'm working on fixing some bugs, and adding the all-pass filter capability.

Edit: I am a little confused about which are the subs in the picture, or if all of them are visible. If they are stacked on top of one another, I'm surprised that this technique doesn't just bomb due to them being too close together to be considered in acoustically unique positions.

Edit 2: I tried deleting the 5th measurement position (green), and re-running the optimization without any changes to filter constraints etc. I did change the trace offsets to 15 dB increments to spread out the traces a bit more. Here's the latest result:

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post #3 of 527 Old 08-18-2015, 09:43 AM - Thread Starter
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Ah, looks much better!! Sub 1 and 2 are underneath the mains. If you look closely you can spot sub 4 right of the right main speaker(+sub2). I also tried putting this sub alongside of the back wall on two different positions, didn't help me back then. Only i didn't have software to help me. Anyway, ill move into a new house soon if all goes well (115 year old house, probably lots more LF damping, probably a lot easier than this concrete box !). And i was standing on sub3 when i took the picture (overview of the room). Sub3 is also the largest, it's a 'leftover' of my previous diy project which was quite enormous haha. This project ended up much smaller and i put a lot more effort in getting the directivity right. For my next house, i'll probably build two new smaller enclosures for the XLS10 drivers which are currently housed in Sub3 (than i'll have four identical single XLS10 sealed subs). Otherwise i'll have nothing left to build haha. Or maybe i need new surrounds, hmmmm.

Anyway, here's a schematic (behold of my paint skills!!). Two large couches (pos1 - 4) with 200x100x9(WxHxD in cm) acoustic panels behind them to dampen the early reflections from the wall. Projector screen and dining table to the right (position 5 ).

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post #4 of 527 Old 08-18-2015, 11:18 AM
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I made a thread of my attempt to EQ 16 of my subs.
I put one beefy sub at the LP and walked a UMIK mic around the room at the various placement options I had available to me (including their existing positions); with the DSP disabled of course...

I figured that finding the best locations were more-important than finding the best EQ filters for any given sub, or group of subs. So I started there...

Those locations looked like this:




Basically I discovered that the locations I had the existing 16 subs in, that I selected by ear, turned out to be the best options for a multi-location configuration. (I have pretty anal hearing... so it didn't surprise me too-much.) It is always best to trust your instruments and science (especially if you are flying in an airplane at high speed in the dark around mountains... LOL!)

The loudest placement was directly behind the golden-seat with the cone firing directly into the back of my head at a distance of <1ft, raised 2ft off the ground (believe me, I really did do an exhausting search for the best locations.)

I assumed it might be loudest because of the distance-law of audio. So no huge-surprise there...
It was up-to 15db louder that the total sum of all the other 15 subs combined.

It had surprisingly few room-modes, but the downside is that it had massive rolloff below that point, that no amount of EQ to that sub could recover that <22hz performance.


Most of my subs are sealed and they all go down to single digits, so any change in position response is purely room-caused.
The red "today" line is the other 15 subs, and the black line is the nearfield skull-nuke position.

When I get home I will try your app and see if I reduces the number of headaches I have.
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post #5 of 527 Old 08-18-2015, 11:41 AM
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Quote:
Originally Posted by Jag768 View Post
Just too many degrees of freedom (gain, delay, high/low pass settings, parametric EQs).
I know, me too! I have 11 discrete bass DSP channels for my subs, that all have those options. (For both all-inputs and all-outputs: I use 3 DCX2496's)
and then a zillion location placement options.

To add additional confusion, they are different brands and box volumes and wattage and performance-capabilities, at different distances, and some of them are stacked/grouped in pairs, and some are individual. (Yeah Yeah I know, I like to torture myself... )

That said, even with all of those variables, the red line I get without EQ doesn't look too bad. They say that once you hit 4 subs that the room-impacted response is basically: "as good as it's gonna get".
Based on my experience I would tend to agree with that.
There are always exceptions of course, like what Jag may have encountered above with his 4 subs, some people have limited placement options and/or haven't found the optimal-locations prior to applying EQ; or they have-found the locations but they don't work with that room layout / Feng Shui. It is what it is, you can only do so much... EQ is a last resort saving grace.

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post #6 of 527 Old 08-18-2015, 06:42 PM
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Quote:
Originally Posted by BassThatHz View Post
It is what it is, you can only do so much... EQ is a last resort saving grace.
The software doesn't require that one use EQ at all. For instance, one could decide to only use adjustable delay and gain/attenuation for each sub individually. So in your case, you could define 11 sub "filter" channels in the software, and only put one delay and one gain/attenuation in each channel, for a total of 22 adjustable parameters. The software will then adjust these 22 parameters to optimize response flatness at multiple listening positions. You can weight the errors at, say, the MLP higher than at other positions.

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post #7 of 527 Old 08-27-2015, 09:59 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
I know, me too! I have 11 discrete bass DSP channels for my subs, that all have those options. (For both all-inputs and all-outputs: I use 3 DCX2496's)
and then a zillion location placement options.

To add additional confusion, they are different brands and box volumes and wattage and performance-capabilities, at different distances, and some of them are stacked/grouped in pairs, and some are individual. (Yeah Yeah I know, I like to torture myself... )

That said, even with all of those variables, the red line I get without EQ doesn't look too bad. They say that once you hit 4 subs that the room-impacted response is basically: "as good as it's gonna get".
Based on my experience I would tend to agree with that.
There are always exceptions of course, like what Jag may have encountered above with his 4 subs, some people have limited placement options and/or haven't found the optimal-locations prior to applying EQ; or they have-found the locations but they don't work with that room layout / Feng Shui. It is what it is, you can only do so much... EQ is a last resort saving grace.
Wow, thats really a no compromise setup, i like it . And that must have been crazy work setting up all those channels. How is the seat-to-seat variance?


And how are others managing their multi sub setup?
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post #8 of 527 Old 08-27-2015, 01:32 PM
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Quote:
Originally Posted by Jag768 View Post
Wow, thats really a no compromise setup, i like it . And that must have been crazy work setting up all those channels. How is the seat-to-seat variance?
As a music-only guy, I'm constantly amazed at some of the subwoofer setups used by home theater buffs, especially those in the DIY sub and speaker forum here.

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And how are others managing their multi sub setup?
There's a post by Matt Grant on multiple-subwoofer setup here that's worth reading.

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post #9 of 527 Old 09-08-2015, 02:10 PM
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Quote:
Originally Posted by BassThatHz View Post
I put one beefy sub at the LP and walked a UMIK mic around the room at the various placement options I had available to me (including their existing positions); with the DSP disabled of course...
I thought doing the subwoofer crawl with UMIK instead of squeezing my head into all those tight spots between the furniture was my original idea!

Quote:
Originally Posted by Jag768 View Post
And how are others managing their multi sub setup?
I posted a simple/budget subs position study of my living room:

One vs two subwoofers?

So far I have settled on placement but the level, phase, EQ, and integration are still awaiting finalized acoustic treatments. At this point my absorbers are all temporary while I climb the learning curve and I have not given much thought to diffusion.

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Originally Posted by andyc56 View Post
As a music-only guy, I'm constantly amazed at some of the subwoofer setups used by home theater buffs, especially those in the DIY sub and speaker forum here.
All my favorite music mixes are 5.1 now. What does a 'music-only guy' listen to?

Quote:
There's a post by Matt Grant on multiple-subwoofer setup here that's worth reading.
Thanks, I will look into that.
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post #10 of 527 Old 09-08-2015, 05:54 PM
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I just now found some other pics of jag768's speakers from a more close up perspective in another forum here. Very impressive and well worth checking out.
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post #11 of 527 Old 09-17-2015, 11:02 AM
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I've uploaded a new update of Multi-Sub Optimizer. It can be downloaded here. There's a new graph trace type for showing and tracing target (house) curves. There were some bug fixes too, including:

1) The optimization algorithm was performing unnecessary calculations at frequencies above those used for the actual optimization. This didn't affect optimization results, only efficiency.

2) When the house (target) curve is computed for the optimization, the curve used internally is offset so that its value at the highest frequency used for optimization is 0 dB.

3) In the optimization options dialog, when the automatic limits options are chosen for reference and optimization frequency ranges via the checkboxes, the actual automatic limits computed by the software are now displayed in the corresponding edit controls. If all needed measurements have not yet been imported at the time the dialog is launched, these may not be the final values used in automatic mode.

4) Minor updates to the .chm (help) file. I have noticed that clicking some of the links can cause the MS Windows HTML help viewer software to give error messages :-(.

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post #12 of 527 Old 09-17-2015, 11:21 AM
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Originally Posted by andyc56 View Post
I've uploaded a new update of Multi-Sub Optimizer.
Wow. Thanks for this! This is exactly what I'd envisioned after reviewing Geddes' materials and discussing the software he uses, as well as reviewing the Harman SFM stuff. I'd envisioned it as more of a manual tool than automatic optimization, but it looks like this works both ways. You even included the listening position weighting I'd envisioned as well as some things I hadn't like making sure the smaller subs in the array won't be over-gained. I'd intended to modify some of the FRD Consortium tools into this someday, though that day was likely to be when I retired LOL.

Now I just need to hurry up and build my subs so I can implement it!
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post #13 of 527 Old 09-17-2015, 11:59 AM
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Wow. Thanks for this! This is exactly what I'd envisioned after reviewing Geddes' materials and discussing the software he uses, as well as reviewing the Harman SFM stuff.
You're welcome! I was inspired by the Geddes video about multiple subwoofers. As soon as I saw it, I said, "I'm gonna write some software that does this". In talking to Earl a while back at his now-closed forum, he said that, while his software predicts the combined output of mains and multiple subs, manual adjustment of filter parameters is necessary. I've combined the summation with a global optimizer that maximizes the flatness of the summed response.

Quote:
Originally Posted by aackthpt View Post
I'd envisioned it as more of a manual tool than automatic optimization, but it looks like this works both ways. You even included the listening position weighting I'd envisioned as well as some things I hadn't like making sure the smaller subs in the array won't be over-gained. I'd intended to modify some of the FRD Consortium tools into this someday, though that day was likely to be when I retired LOL.
I'm retired myself. That's the only reason I had time to do it!
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post #14 of 527 Old 09-17-2015, 02:26 PM
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4) Minor updates to the .chm (help) file. I have noticed that clicking some of the links can cause the MS Windows HTML help viewer software to give error messages :-(.
This is the one I'm getting now.

And I could use some help.

Michael
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Did you really need to quote that entire post in your reply?
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post #15 of 527 Old 09-17-2015, 02:45 PM
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This is the one I'm getting now.

And I could use some help.

Michael
Did it happen when you clicked on a link, or just browsing in the tree view on the left? I've been trying to use the same HTML in the help file as on my site, but the buggy nature of the MS HTML help engine is messing me up. If it was from clicking on a link, just press the "back" button.

Or did the help file just not work at all? The solution to that can be found here.
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post #16 of 527 Old 09-17-2015, 03:06 PM
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Unblock worked!

For those who want to save themselves the trouble of following the link, find the help file ("multi-sub_opt" compiled HTML), right click, properties tab bottom right -> Unblock.

THANKS!
Michael

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You're welcome! When I get around to doing an installer program, this problem will go away. The program for creating installer programs is itself a PITA, so I've been putting that off.

Also, I just now noticed that pressing F1 causes an error message in the help system . Just found a a fix for that and will be posting an update when I gather a few more requests.
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post #18 of 527 Old 09-20-2015, 10:09 AM
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Andy,

I use a Denon DN-AV500 (no individual analog channel input for center channel) as a pre/pro, with a minidsp on the back end managing two subwoofer clusters.

I am planning to use a Dirac Live enabled nanoAVR before it, so I won't have an EQ'ed LCR when I measure for MSO (in fact, I'll only be measuring with a loopback through the individual speaker amps most likely).

Can I use MSO for the sub out only for optimal delay/gains and maybe a few PEQ cuts without having to measure a sattelite/main (LCR) channel, so that I can measure/setup with Dirac afterward? Dirac will likely correct the center channel affecting the response, which MSO would not have been privy to before running DL.

Thanks for such a great piece of software, is there a place we can donate to in order to further fund development?



Thanks,


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post #19 of 527 Old 09-20-2015, 10:56 AM
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Quote:
Originally Posted by maxmercy View Post
Andy,

I use a Denon DN-AV500 (no individual analog channel input for center channel) as a pre/pro, with a minidsp on the back end managing two subwoofer clusters.

I am planning to use a Dirac Live enabled nanoAVR before it, so I won't have an EQ'ed LCR when I measure for MSO (in fact, I'll only be measuring with a loopback through the individual speaker amps most likely).

Can I use MSO for the sub out only for optimal delay/gains and maybe a few PEQ cuts without having to measure a sattelite/main (LCR) channel, so that I can measure/setup with Dirac afterward? Dirac will likely correct the center channel affecting the response, which MSO would not have been privy to before running DL.
MSO will give an error message if an optimization is attempted with no mains measurements defined. In optimizing the frequency response flatness, it first calculates the reference level by taking the average in dB over frequency of the combined mains/subs response at each listening position and for each (of potentially millions) of the EQ/gain/delay combinations attempted. This occurs in the frequency range defined as the "reference frequency range" in the optimization options dialog. The reference frequency range should be chosen where the response is nominally flat, starting somewhat above crossover and extending to, say, 200 Hz or so. Without mains measurements, this can't work properly.

This gets to a broader issue of how to use MSO in conjunction with room correction systems. Unfortunately, these systems will tend to "fight" each other. On one hand, if one runs room correction before MSO, then suckouts might be present in the combined subwoofer output (because they haven't been optimized yet). These would be much better fixed by using MSO before room correction to adjust how the subs interact with each other to "fill in" the suckouts rather than boosting them with room correction. On the other hand, if you run room correction after MSO, it will apply filtering to both mains and subs, but without regard to how they interact with one another in the frequency domain in the crossover region. Unless you're very lucky, running the correction will degrade the integration.

The simplest way to fix this up after running room correction might be to just apply pink periodic noise in REW and tweak the sub distance in the AVR to get the best integration using the RTA. I should mention that I am not at all familiar with Dirac. I'm a two-channel guy in the "dont EQ above Schroeder" camp. If Dirac changes the crossover frequency to something different from what was used when running MSO (as Audyssey might do), then all bets are off as far as MSO optimization.

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Originally Posted by maxmercy View Post
Thanks for such a great piece of software, is there a place we can donate to in order to further fund development?
I don't have anything like that set up, but thanks for the thought!

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post #20 of 527 Old 09-20-2015, 11:19 AM
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MSO will give an error message if an optimization is attempted with no mains measurements defined. In optimizing the frequency response flatness, it first calculates the reference level by taking the average in dB over frequency of the combined mains/subs response at each listening position and for each (of potentially millions) of the EQ/gain/delay combinations attempted. This occurs in the frequency range defined as the "reference frequency range" in the optimization options dialog. The reference frequency range should be chosen where the response is nominally flat, starting somewhat above crossover and extending to, say, 200 Hz or so. Without mains measurements, this can't work properly.

This gets to a broader issue of how to use MSO in conjunction with room correction systems. Unfortunately, these systems will tend to "fight" each other. On one hand, if one runs room correction before MSO, then suckouts might be present in the combined subwoofer output (because they haven't been optimized yet). These would be much better fixed by using MSO before room correction to adjust how the subs interact with each other to "fill in" the suckouts rather than boosting them with room correction. On the other hand, if you run room correction after MSO, it will apply filtering to both mains and subs, but without regard to how they interact with one another in the frequency domain in the crossover region. Unless you're very lucky, running the correction will degrade the integration.

The simplest way to fix this up after running room correction might be to just apply pink periodic noise in REW and tweak the sub distance in the AVR to get the best integration using the RTA. I should mention that I am not at all familiar with Dirac. I'm a two-channel guy in the "dont EQ above Schroeder" camp. If Dirac changes the crossover frequency to something different from what was used when running MSO (as Audyssey might do), then all bets are off as far as MSO optimization.



I don't have anything like that set up, but thanks for the thought!
I see. Without EQ on the center channel, I do not have a very flat FR baseline in the region above crossover due to room effects. I was hoping to run MSO to get proper delays/gains configured for flattest FR and then run Dirac. I may have to just experiment manually with delays/gains on the sub clusters to get the best response over the greatest number of locations then run Dirac. I was hoping MSO could do that initial experimentation for me.

JSS
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post #21 of 527 Old 09-20-2015, 11:36 AM
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Originally Posted by maxmercy View Post
I see. Without EQ on the center channel, I do not have a very flat FR baseline in the region above crossover due to room effects. I was hoping to run MSO to get proper delays/gains configured for flattest FR and then run Dirac. I may have to just experiment manually with delays/gains on the sub clusters to get the best response over the greatest number of locations then run Dirac. I was hoping MSO could do that initial experimentation for me.
It can. You just need to measure either Left and Right excited in mono, or center channel to make it work.

Edit: Let me try to clarify this. Just because the center channel isn't as flat as you might like it to be, this doesn't prevent MSO from improving flatness at other frequencies. That's because the error MSO tries to minimize isn't the worst-case error over frequency, but the sum of the squares of the errors over frequency.

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post #22 of 527 Old 09-20-2015, 11:47 AM
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I'll try it and report back. I hope the himalayan center channel response from 100-300Hz won't affect things much, esp if an average is calculated.

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post #23 of 527 Old 09-20-2015, 12:06 PM
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You might also be able to tweak the high end of the optimization frequency range to avoid some of the bad areas. IOW, the high end of the optimization frequency range might be made a little lower (say, 150 Hz) than the high end of the reference frequency range (say, 200 Hz).
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post #24 of 527 Old 09-22-2015, 05:23 PM
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Quote:
Originally Posted by maxmercy View Post
I use a Denon DN-AV500 (no individual analog channel input for center channel) as a pre/pro, with a minidsp on the back end managing two subwoofer clusters.

I am planning to use a Dirac Live enabled nanoAVR before it, so I won't have an EQ'ed LCR when I measure for MSO (in fact, I'll only be measuring with a loopback through the individual speaker amps most likely).
Are you doing bass management in the Denon, or in another nanoAVR ahead of the nanoAVR-DL? EQ needs to be applied after bass management. The configuration of DL before bass management is not a valid one. It will function, but may give unpredictable results.
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post #25 of 527 Old 09-22-2015, 05:58 PM
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Dirac Live does not take into account bass management. That is one of its drawbacks; you must manually compensate for the crossover phase shift.

The multisub program is Matlab? Is it possible to get the source code?

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post #26 of 527 Old 09-22-2015, 06:18 PM
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Quote:
Originally Posted by DonH50 View Post
The multisub program is Matlab? Is it possible to get the source code?
It's a standalone native Windows GUI executable written in C++, compiled with the Visual C++ portion of Visual Studio 2015 Community Edition. I had to modify the source code of this MFC graphics library for some of the features I needed and I'm not authorized to redistribute that modification. I don't think I'd redistribute the source code anyway.

This page has the download link.

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post #27 of 527 Old 09-22-2015, 06:21 PM
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Quote:
Originally Posted by DonH50 View Post
Dirac Live does not take into account bass management. That is one of its drawbacks; you must manually compensate for the crossover phase shift.
That wasn't what I was referring to. Any EQ needs to be done downstream of bass management or it's an invalid configuration. This same problem happened years ago with the Emotiva UMC-1 bass management and resulted in all sorts of flame wars.
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Got it, thanks. Something was in Matlab, I'm sure...

On the EQ, I agree, but with Dirac Live you have to manually deal with the crossover in the processor because DL does not. As I understand DL, it treats the sub and speakers independently and full-range, without regard to the crossover in the AVR. So, whatever phase shift the AVR's crossover introduces is not compensated by DL.

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post #29 of 527 Old 09-27-2015, 11:19 AM
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I've uploaded a new version today. It can be downloaded here. It adds support for miniDSP-compatible biquad text format in the filter reports, so you can copy and paste this information into the miniDSP software directly without having to enter individual filter parameters manually. To enable it, choose Tools, Application Options, Hardware. Check the box labeled "Include biquad information in filter reports" and choose the sample rate. Then, when a filter report is generated, you'll get the biquad text. Here's a simple example of just a single PEQ filter:

DSP Filter Channel Information:
Sample frequency 48000 Hz
Sub Channel 1:
biquad1,
b0=0.998587755842349,
b1=-1.995698264655141,
b2=0.997281499773885,
a1=1.995698264655141,
a2=-0.995869255616234,
biquad2,
b0=1.000000000000000,
b1=0.000000000000000,
b2=0.000000000000000,
a1=-0.000000000000000,
a2=-0.000000000000000,
biquad3,
b0=1.000000000000000,
b1=0.000000000000000,
b2=0.000000000000000,
a1=-0.000000000000000,
a2=-0.000000000000000,
biquad4,
b0=1.000000000000000,
b1=0.000000000000000,
b2=0.000000000000000,
a1=-0.000000000000000,
a2=-0.000000000000000,
biquad5,
b0=1.000000000000000,
b1=0.000000000000000,
b2=0.000000000000000,
a1=-0.000000000000000,
a2=-0.000000000000000,
biquad6,
b0=1.000000000000000,
b1=0.000000000000000,
b2=0.000000000000000,
a1=-0.000000000000000,
a2=-0.000000000000000
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post #30 of 527 Old 09-27-2015, 01:04 PM
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Thanks!

Markus

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