2 subs for 2-ch only system in a small room?

tboooe

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May 11, 2013
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I recently added a REL T/5i sub to my system and have been very happy with the results. Integration was a breeze with my Sonus Faber Guarneri Evolution monitors and I am now more engaged in my music than ever. So of course being a typical audiophile, I got to thinking if 1 sub sounds this good will 2 sound even better? The challenge is my room. Its very small at 9' w x 10' l x 9' h. The back wall is about 3' high, above which it opens up to the rest of my house. I have bass traps in this room. Right now, using just 1 sub and spending a lot of time positioning my speakers, my freq response from 20-1000hz is +- 2db with a -4db dip at 200hz and a +4db hump at 40hz. Not perfect but my system still sounds amazing.

I know the general consensus is a second sub will sound better but I am concerned with the size of my room. Will adding a second sub in such a small space over power it or will it actually help to smooth out nodes? Also can someone describe what benefits I would get with 2 subs versus 1?
 

amirm

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You actually don't have a small room. The open space to the rest of the house allows the bass frequencies to go through, acting like an almost perfect bass absorber (assume that space is much larger than your room).

I say if your system sounds amazing, I would not mess with a second sub. The complexity of optimizing that manually into your system will be high.

But yes, its purpose would be to further smooth the response but you would need EQ either in the sub or externally. Without it the job will be much harder and you can easily make things worse.

You can also put the sub right next to the existing sub to get more output if you desire that.
 

tboooe

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May 11, 2013
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Thank you Amir. Curious why you think setting up a second sub would be so difficult and why an EQ is needed? I know I have to experiment with placement but in your experience do you think its too hard to find a good location?
 

DonH50

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Jun 22, 2010
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Normally I would say those dimensions would lead to significant FR issues since you have three nearly identical dimensions. However, a few things lead me to side with Amir in suggesting you put your money elsewhere:

  1. The room opens to the rest of the house, is not sealed, and so room modes are less problematic;
  2. Your frequency response sounds just fine; and,
  3. You are happy with the sound.
I'd save the money and hassle.

Adding a sub, you may not require EQ (though it can help), but definitely require the ability to independently adjust the phase (delay) of the signal to the second sub. Some subs have phase adjustment (a continuous knob or DSP based, not just a -/180 degree switch), and some AVRs provide independent sub outputs.

IMO - Don
 

amirm

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Thank you Amir. Curious why you think setting up a second sub would be so difficult and why an EQ is needed? I know I have to experiment with placement but in your experience do you think its too hard to find a good location?
If you had a simple rectangular room, research has been done as to where the possible good positions are. But with your open floor plan on one end, that research doesn't apply. You now have infinite possibilities as far as location of subs and the parameters for each. Take a look at this article I wrote on computer assisted version of that: http://www.audiosciencereview.com/f...s/computer-optimization-of-room-acoustics.12/. Alas, that solution is expensive.

As to EQ, a lot of optimization strategies for subs rely on the fact that if some frequency gets boosted, that is fine because EQ can easily pull that down. It is the nulls that we try to fill with multiple subs where EQ is not effective. If you don't have EQ then your job becomes even harder because you have to avoid both the dips and peaks. My article shows how computers can find that solution too but manually would be very hard.

EQ in your current system would yield further improvements without any additional sub. You can knock down the peaks and get very good response based on numbers you have given.
 

tboooe

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May 11, 2013
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If you had a simple rectangular room, research has been done as to where the possible good positions are. But with your open floor plan on one end, that research doesn't apply. You now have infinite possibilities as far as location of subs and the parameters for each. Take a look at this article I wrote on computer assisted version of that: http://www.audiosciencereview.com/f...s/computer-optimization-of-room-acoustics.12/. Alas, that solution is expensive.

As to EQ, a lot of optimization strategies for subs rely on the fact that if some frequency gets boosted, that is fine because EQ can easily pull that down. It is the nulls that we try to fill with multiple subs where EQ is not effective. If you don't have EQ then your job becomes even harder because you have to avoid both the dips and peaks. My article shows how computers can find that solution too but manually would be very hard.

EQ in your current system would yield further improvements without any additional sub. You can knock down the peaks and get very good response based on numbers you have given.

I've been thinking about using digital room correction (DIRAC). My first step towards this is to get a usb mic and analyze my room through Room EQ Wizard software. I am hopeful this is more accurate than my cheapo SPL meter and test tones method.
 

amirm

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Apr 2, 2010
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I've been thinking about using digital room correction (DIRAC). My first step towards this is to get a usb mic and analyze my room through Room EQ Wizard software. I am hopeful this is more accurate than my cheapo SPL meter and test tones method.
Yes, and a lot easier to boot. Note that Dirac does NOT show you a proper measurement post EQ so being able to measure it with REW is important.

If you have not used REW before, here are my two tutorials:

http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-1.4/
http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-2.5/

Feel free to ask questions but I sense you are already on the proper path :).
 

dallasjustice

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Apr 12, 2011
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I'm not sure what you mean Amir. You can see that DIRAC's predicted amplitude results are very accurate.
http://www.whatsbestforum.com/showthread.php?15212-Dirac-validation

The same is true with Audiolense and Acourate as well, IME.

Yes, and a lot easier to boot. Note that Dirac does NOT show you a proper measurement post EQ so being able to measure it with REW is important.

If you have not used REW before, here are my two tutorials:

http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-1.4/
http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-2.5/

Feel free to ask questions but I sense you are already on the proper path :).
 

Fitzcaraldo215

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Nov 3, 2014
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Yes, and a lot easier to boot. Note that Dirac does NOT show you a proper measurement post EQ so being able to measure it with REW is important.

If you have not used REW before, here are my two tutorials:

http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-1.4/
http://www.audiosciencereview.com/f...om-measurement-tutorial-for-dummies-part-2.5/

Feel free to ask questions but I sense you are already on the proper path :).

Yes, that is true of most EQ tools. But, there might be potential problems reconciling separate, independent measurements with those predicted by the EQ. Exact mike placement is one key issue, especially if the EQ calibration, like Dirac, requires moving the mike around to multiple positions. There is also the multipoint averaging aspect vs. single point measurements. Dirac's algorithm for this is proprietary, so it would be hard to reproduce the same results via independent measurements, even if we knew the algorithm. As I understand it, incorrectly perhaps, that multi-point averaging ignores certain local response irregularities unless they are confirmed at multiple mike locations.

My point is single point measurements might not agree with the EQ corrections and predictions based on multi-point. So, which is "right"? It is controversial. Some believe strongly in doing EQ calibrations one way vs. the other. Me? I favor the averaged multi-point idea for the average Joe, like me. But, I cannot then easily duplicate predicted results via independent measurements. So, I just put my feet up and listen, subjectively feeling that Dirac has made a big positive difference as I switch it on and off.
 

dallasjustice

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Apr 12, 2011
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Single point can work very well. The key is how late arrivals are windowed. Single point measurements have the advantage of being better suited to correct time domain.
Yes, that is true of most EQ tools. But, there might be potential problems reconciling separate, independent measurements with those predicted by the EQ. Exact mike placement is one key issue, especially if the EQ calibration, like Dirac, requires moving the mike around to multiple positions. There is also the multipoint averaging aspect vs. single point measurements. Dirac's algorithm for this is proprietary, so it would be hard to reproduce the same results via independent measurements, even if we knew the algorithm. As I understand it, incorrectly perhaps, that multi-point averaging ignores certain local response irregularities unless they are confirmed at multiple mike locations.

My point is single point measurements might not agree with the EQ corrections and predictions based on multi-point. So, which is "right"? It is controversial. Some believe strongly in doing EQ calibrations one way vs. the other. Me? I favor the averaged multi-point idea for the average Joe, like me. But, I cannot then easily duplicate predicted results via independent measurements. So, I just put my feet up and listen, subjectively feeling that Dirac has made a big positive difference as I switch it on and off.
 

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