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I have a large but unconventional listening room, but enjoy high quality (2-channel digital-only) equipment. I've never used subs as such, although my Avantgarde Duo XD speakers feature hybrid self-powered bass sections, each with twin 12" drivers supporting mid and top end horns.

After a careful and extensive home demo selection sessions 2 years ago, I've moved from SETs to Class D power amps - currently the excellent GaN FET-based Atma-Sphere Class D monos.

I'm seriously considering the purchase of the NAD M66 that offers multiple sub outlets and the wherewithal to get them sounding harmoniously with the help of Dirac Live and Dirac Live Bass Control.

If I go that route and purchase 2 or 3 or even 4 subs, I'm totally ignorant as to where they would do best to mitigate bass nodes and whatever else needs to be sorted for best sound. I don't need more or deeper bass as the current 4 x 12" drivers offer plenty, but carefully-placed subs with Dirac control should improve the quality of the bass and hopefully relatively small subs with single 10" drivers may achieve this - but guidance is welcome.

This is where I hope some of you technical wizz-kids may be able to help! Please take a look at my room layout. There are limited places I could install subs and I've marked these with a NUMBER where a small sub could be placed (sized to be placed under a dining chair) or a LETTER where a larger one could go. Hopefully just 2 will do the job, but this is where I need expert advice as to placement, size of sub and maybe even which model would be ideal.

Also, does anyone have experience of wireless subs, so that no interconnect cable is needed, but using Bluetooth (or whatever) wireless links between the M66 and each sub? Because of the room's features, I don't want cables trailing across the floor, although positions 3, 4 and B could be hard wired with XLR cables.

Sorry for so many questions, but I'm hoping someone can offer scientifically sound and more importantly practical advice. Or maybe you think I don't need subs at all? Many thanks.
 

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I have a large but unconventional listening room, but enjoy high quality (2-channel digital-only) equipment. I've never used subs as such, although my Avantgarde Duo XD speakers feature hybrid self-powered bass sections, each with twin 12" drivers supporting mid and top end horns.

After a careful and extensive home demo selection sessions 2 years ago, I've moved from SETs to Class D power amps - currently the excellent GaN FET-based Atma-Sphere Class D monos.

I'm seriously considering the purchase of the NAD M66 that offers multiple sub outlets and the wherewithal to get them sounding harmoniously with the help of Dirac Live and Dirac Live Bass Control.

If I go that route and purchase 2 or 3 or even 4 subs, I'm totally ignorant as to where they would do best to mitigate bass nodes and whatever else needs to be sorted for best sound. I don't need more or deeper bass as the current 4 x 12" drivers offer plenty, but carefully-placed subs with Dirac control should improve the quality of the bass and hopefully relatively small subs with single 10" drivers may achieve this - but guidance is welcome.

This is where I hope some of you technical wizz-kids may be able to help! Please take a look at my room layout. There are limited places I could install subs and I've marked these with a NUMBER where a small sub could be placed (sized to be placed under a dining chair) or a LETTER where a larger one could go. Hopefully just 2 will do the job, but this is where I need expert advice as to placement, size of sub and maybe even which model would be ideal.

Also, does anyone have experience of wireless subs, so that no interconnect cable is needed, but using Bluetooth (or whatever) wireless links between the M66 and each sub? Because of the room's features, I don't want cables trailing across the floor, although positions 3, 4 and B could be hard wired with XLR cables.

Sorry for so many questions, but I'm hoping someone can offer scientifically sound and more importantly practical advice. Or maybe you think I don't need subs at all? Many thanks.
Have you measured with REW and a UMIK yet to see if, and at which frequency, any room modes are occurring? I suspect the general consensus here will be to 'measure first' then decide on a strategy...
 
Thanks. Yes, but I've changed PC since then so may need a serious search. I plan to do another measurement session soon, though I doubt it'll indicate where subs may be best placed or how much difference they would make. Hoping for an informed guess from those who have knowledge of DSP and room anomalies.
 
Made some liberal assumptions regarding your room shape. Here are my simulated room modes (2D only, height not considered) for the first 28 modes.
room_modes.png
 
Thank you for doing that. I'm not sure I can make head or tail of it, but food for thought!

I dug out my UMIC-1 microphone today and will try to take measurements later in the week. I can do frequency response curve adjustments using alternative DSP software.

I have Dirac Live that can auto-adjust the bass frequencies and I have the XD software that's built into my Avantgarde speakers. This is more a manual system whereby I can adjust a flat-line response according to what the REW measurements suggest should be done. I suspect the XD software would offer the better end result as the upper frequencies do not have to pass through the DSP at all. The XD software is in the AG's built-in bass amp so after the crossover.

I'm not experienced in either DSP method so will probably take the easy path by using DL, but my past experience is that a little of the top end sparkle is lost with DL, despite my version not ADJUSTING these higher frequencies. I've concluded that, as the entire signal has to pass the DL filter if engaged, the higher frequencies suffer when subjected to this processor.
 
I have a large but unconventional listening room, but enjoy high quality (2-channel digital-only) equipment. I've never used subs as such, although my Avantgarde Duo XD speakers feature hybrid self-powered bass sections, each with twin 12" drivers supporting mid and top end horns.

After a careful and extensive home demo selection sessions 2 years ago, I've moved from SETs to Class D power amps - currently the excellent GaN FET-based Atma-Sphere Class D monos.

Sweeet!

Please take a look at my room layout...

Thank you for providing your room layout!!

A general principle for a distributed multisub system is, distribute the subs asymmetrically, and as far apart as you reasonably can, in as many planes as you reasonably can. (Credit to Earl Geddes for these guidelines). If one or more can be elevated so that it's closer to the ceiling than to the floor, that gives you some distribution in the vertical plane as well. Here are some suggestions, and I'm making the assumption that your Avantardes are contributing in the subwoofer region:

Four subs: C, A, 2, D

Three subs: C, 1, D

Two subs: C, 2

You might even find that reversing the polarity of one of the subs results in smoother in-room bass.
 
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