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Dual Stereo Subwoofers in multichannel system

Mishaiger

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Hi, i need your help, guys. Right now i have 5.1 system, but i plan to upgrade it to 7.2. And i want stereo bass.
I was thinking about buying Denon AVR-X3600H AV Receiver. If i understand right it have 2 sub out, which you can equalize independently, but it will still be mono bass, right? Also i was wondering, since its pre amp have 12 channels can i use 2 channels for my needs? I do not need more than 7 speakers.

What i want is this:
FL,SL,RL=>LSUB
FR,SR,RR=>RSUB
C,LFE=>Both LSUB and RSUB

I will be using Windows PC as audio source. I'm using EqAPO to equalize + do crossover, i.e. redirect bass from 5 speakers to 1 sub. And i can easily redirect bass from 5 speakers to 2 subs, but this will take additional channel, which is meant for back speakers.

I'm basically asking about digital crossover hardware that wont take up additional channels. I can also redirect bass from all speakers to, say, front, so i just need a stereo configurable crossover, although, i think that it will be better if crossover could filter all channels.

So i want your advice about stereo bass and how to make it all work, will receiver be enough? Recommend me buy some digital crossover/processor? Maybe diy? Something else?

PS. I have only bookshelf speakers therefore they cant play bass and buying floorstanding is out of question because i do not have enough space. I was also thinking about passive crossovers, but they turned out to be quite expensive and they create some nulls in frequency response.
 

markus

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There is no such thing as stereo bass in acoustically small rooms (see Toole "Sound Reproduction" for a detailed discussion and references). Better use a monophonic multisub approach which results in better and consistent sound quality when dialed in correctly.
 

pozz

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There is no such thing as stereo bass in acoustically small rooms (see Toole "Sound Reproduction" for a detailed discussion and references).
This is incorrect. You can have stereo bass but:
  • A specific setup is required.
  • FR will be uneven.
  • Bass SPL will be lower.
  • A lot of the time you won't notice (plenty of recordings have mono bass; few have deliberate stereo bass).
Toole's book says nothing about it being impossible, but goes into detail about why it is impractical.
 

markus

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This is incorrect. You can have stereo bass but:
  • A specific setup is required.
  • FR will be uneven.
  • Bass SPL will be lower.
  • A lot of the time you won't notice (plenty of recordings have mono bass; few have deliberate stereo bass).
Toole's book says nothing about it being impossible, but goes into detail about why it is impractical.

You can get a sense of directionality but that's not really "stereo bass" as you could perceive it outdoors. Not worth the effort and also not what anybody in the recording world strives for. The exception proves the rule.
 
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Mishaiger

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Well, i redirected bass to front speakers and they cant play it very well, but i really can hear it being left or right depending on the recording. I have a sub which is located left from me, it was really pissing me off that i can clearly hear bass only from left side. I know that i can achieve something like omnidirectivity with 2 subs playing mono, but i tested it with speakers and decided to go for stereo. My main reason, of course, that some recordings have bass out of phase (or how do i correctly say it? -180 and +180) and obviously mono speakers cant play out of phase, thats why i want stereo bass, not mono.

So i'm asking not if stereo bass is good thing or will it work in my room, but how to send correct audio signals to subwoofers. And, if no one mentioned it, i get it that you cant make it with Denon receiver. My worst case will be using channel from rear speakers, and i'm asking is it possible to avoid that?
 
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markus

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Friends, in classical music we often have plenty of stereo bass information. Of course, if you can make that work well or not in a small listening room, that's another question.

No, that was the question :) Why obsess about something that can't be reproduced or isn't even available in most recordings while compromising aspects that can be reproduced and are available in recordings?
 

markus

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Well, i redirected bass to front speakers and they cant play it very well, but i really can hear it being left or right depending on the recording.

You can not. This has been scientifically tested. What you can hear though is pressure gradients caused by small room effects. You can hear it even with monophonic recordings. Also other sensory input can result in a directional perception – our hearing doesn't operate in isolation from other senses.

Or maybe you're talking about the frequency range above about 60-80Hz? That's not "subwoofer frequencies" anymore.
 
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Mishaiger

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Or maybe you're talking about the frequency range above about 60-80Hz? That's not "subwoofer frequencies" anymore.
Yeah, as i said, i have a small bookshelf speakers to test, they can go as low as about 50hz, usually i have crossover at 110hz. Maybe i cant hear lower than 60 as you said. But subwoofers will play 110hz and lower, so i should hear the difference between mono and stereo.
And thats actually the question, what hardware do i need to redirect bass from speakers to 2 subs as i described in initial post?
 

pozz

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nd thats actually the question, what hardware do i need to redirect bass from speakers to 2 subs as i described in initial post?
You can use this or similar units, like professional multichannel interfaces and set the crossover up with software.
 

digitalfrost

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I'm basically asking about digital crossover hardware that wont take up additional channels. I can also redirect bass from all speakers to, say, front, so i just need a stereo configurable crossover, although, i think that it will be better if crossover could filter all channels.

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd

You can feed this a stereo signal and get two low-passed singals out which you can send to the subs.
 
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Mishaiger

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You can use this or similar units, like professional multichannel interfaces and set the crossover up with software.
I was also looking at this, but its not fully digital. I'm not sure, but i think i can use USB as input, thats absolutely fine, but it can only output as analog. And it only have got 8 outputs, but for 2 subs + 7 speakers i need 9 outputs.

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd

You can feed this a stereo signal and get two low-passed singals out which you can send to the subs.
It is almost as above, not fully digital + i can not use its digital in, because its only stereo.
But lets consider, i connect left and right from receiver pre amp out. Cut high frequency for subwoofers, and thats it for subwoofers. But i will need another amplifier for left and right speakers, otherwise no low frequency cut for speakers. And i would like to continue using receiver amplifier for speakers. Without additional amplifier for speakers it will be same as simply having crossover in subwoofer amplifier.
But overall that is quite good option.

So right now i have 2 options, this or using channel from rear speakers, latter offering superior quality because of no analog to digital conversion and then digital to analog.
Personally i was thinking about something like box with 1 usb-in and 2 usb-out: usb-in 8 channels, first usb-out 7 channels with low frequency cut and second usb-out is 8 channels mixed into 2 channels + high frequency cut. Also i'm ok even without mixing 8 channels into 2, since i can redirect bass from all channels to front, so i just need FL to LSUB and FR to RSUB.
 
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Mishaiger

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I just got a thought. What about Denon receiver in 7.1 + bi amp configuration. What about crossovers?
Because if I can apply delay and crossover to them, then this option is also viable. Although again inferior to using rear channel because i can only choose within predefined crossover cut frequencies and cut strength.
PS. Even if i can apply individual crossover, i still doubt that i can apply individual delay, because bi amp was designed only for one bi amp speaker, not speaker and subwoofer.
 

pozz

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What about BSS, RME or Xilica products?
 

mitchco

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If you are using a PC as the source, why not go all digital? Use JRiver as your media player. Audiolense DSP is about $430 and can do all of your digital XO, time alignment of all drivers plus room correction (both in the frequency and time domains). Audiolense also provides full bass management. JRiver also knows about linear phase FIR filter latency, so the lypsync is perfect with movies.

There are quite a number of multichannel DAC's with 16 channels like the Lynx Aurora. There are some folks in the Audiolense folks doing what you are looking to do, some even with triamped LCR's. My triamp system also includes stereo subs. Not because of stereo bass content (as a ex recording/mixing engineer, most bass below 100 Hz is mono and we spend a great deal of time with phase meters to make sure the bass does not disappear when summed to mono, but that is a different subject) but because I have complete control over each individual driver in my system. This is what gives the system the dynamic impact as all direct sound is arriving at your ears at the same time. Loads of fun! Good luck with your project!
 

digitalfrost

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Audiolense DSP is about $430 and can do all of your digital XO, time alignment of all drivers plus room correction (both in the frequency and time domains).
Does Audiolense provide a virtual WDM soundcard so this solution works for the whole system, or is it "just" ASIO?
 

mitchco

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Hi @digitalfrost Audiolense DSP application provides acoustic measurement, analysis, design, and generation of the FIR filters. As mentioned, JRiver can host the filters and using JRiver's WDM driver and one can loopback system audio through JRiver's convolution engine. Or another approach is to use VB-cable ASIO bridge to route system audio (like Netflix or YouTube) and route it through a standalone convolver like Audiolense Convolver, or Acourate Convolver or ... There are several approaches depending on the specific scenario.
 

detlev24

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[...] Not because of stereo bass content (as a ex recording/mixing engineer, most bass below 100 Hz is mono and we spend a great deal of time with phase meters to make sure the bass does not disappear when summed to mono, but that is a different subject) but because I have complete control over each individual driver in my system. This is what gives the system the dynamic impact as all direct sound is arriving at your ears at the same time. [...]
Thank you for the information! I was looking for this recently.

So, since most bass below 100 Hz is mono, as you explained: Does this mean it is available on both the stereo channels, identically? This would make sense to me, as it would allow for lower distortion of the loudspeakers during playback and it would lead to excitement of room modes from two, rather than one position. Due to negligible directivity below 100 Hz, no audible impact in terms of stereo imaging should be given even, when multiple subwoofers are added; receiving their information mixed for one single mono bass channel [in case of full-range main loudspeakers, those might additionally be run without HPF]. Does my line of thought make sense; or did I miss something?

Furthermore, by "as all direct sound is arriving at your ears at the same time"; are we talking exclusively about delays for each individual loudspeaker/subwoofer? Comprehensive bass management, see the following excerpt from the 'miniDSP DDRC-88D' user manual [page 44], suggests, that individual delays can be added even in case of "multi-subwoofer mono mixing". Please correct me, if my interpretation is erroneous. I am trying to learn something. :)

DDRC-88D.png

[...] As mentioned, JRiver can host the filters and using JRiver's WDM driver and one can loopback system audio through JRiver's convolution engine. Or another approach is to use VB-cable ASIO bridge to route system audio (like Netflix or YouTube) and route it through a standalone convolver like Audiolense Convolver, or Acourate Convolver or ... There are several approaches depending on the specific scenario.
I have been trying to get working several options for system-wide integration of VST-plugins on Windows 10 [mainly, 'Sonarworks Reference' and 'Dirac Live']:
  • JRiver WDM Driver
  • VB-CABLE + either of:
    • Pedalboard2
    • Juce Plug-In Host
The upper solutions give pops/cracks and extremely high latencies, e.g., during YouTube playback via a web browser [just one example]. Furthermore, with JRiver's WDM Driver, certain usability issues remain permanently, e.g., when closing the application. VB-CABLE and the two mentioned hosts did not receive any update for the last 5+ years.
  • Audiolense Convolver 0.9, which is 'beta', does not start at all [although, both the required 'Dotnet framework 4 (or later)' and 'Visual C++ Redistributable for Visual Studio 2015' are installed on my system]
  • Equalizer APO, which was my last hope + seems to be the only contender with multi-channel implementation, still needs to get its VST-plugin support fixed [see link].
Is there really no (inexpensive) solution available, which is user-friendly and works reliably?

====
Thank you again, @mitchco!
 
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mitchco

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@detlev24 it is not guaranteed that bass is mono under 100 Hz. In fact, nothing is guaranteed on the music production side :) Virtually all pop, rock, alt, country, R&B, blues, etc., are all mono mic'd in the studio to begin with. The reverb and delay one hears is all an elaborate illusion. Of course, you don't need to watch the whole thing...


Of course, there are labels that capture purist two channel "stereo" recordings and the above may or may not apply...

Bass management routing and mixing is a subject way beyond a thread post. There is a section in the Audiolense PDF help file that explains some of the unlimited possibilities...

I have not had any issues with the JRiver WDM driver or VB-Cable - ASIO Bridge or Audiolense convolver (need to read the manual and it is Beta...) So using Netflix Windows 10 app for example, with VB-Cable capturing the stream, routing the audio through ASIO to the AL convolver and then out to my Lynx Hilo using ASIO works perfect. No lipsync issues with a minimum phase filter and I did to have to change any buffer sizes. I think the system latency was 10ms as measured by AL convolver.

But I agree, these solutions can be finicky to set up, hard to debug and kinda at the mercy of how good the audio drivers are. used in the interactions. I use ASIO exclusively if I can... Also one windows update or another app update can stop things from working and back to hard to debug.
 
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