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It sounds like it's quite a job to get their placement and setup/calibrated so they do not cancel each other out

How hard is it really ? and what equipment do you need ?
 

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From a noob myself I would only consider duals if I had a EQ which calibrated two subwoofers, and did phase and EQ on each one, independently then calculate it as a pair. Something like the top of the range MultEQ XT32 audyssey sub EQ HT or SVS EQ1.
 

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Unfortunately, improper placement of a second subwoofer can actually make matters worse due to interactions between the sound waves of both subwoofers and the room itself.
Bit of a problem for myself, if I wanted another sub it could only fit in one place. Both would be along the front wall, one either side of the TV.
 

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It is not that difficult to add a second sub. The keep is to have a couple of placement options or be willing to make the placement options. If you don't have REW, Omnimic, then add the try the second sub and check if the spl goes up with the addition of the second sub. First level match each sub to around 73 db. With the addition of the second sub the level will usually go up to around 76 db.
 

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From what I understand if both subs are equidistant it should be ok- you can leave both phase controls at 0' however if say one was along the side wall, then another front, or maybe front then I understand that is where phase can cause cancellation.

ie the top one is my room layout (I have a single, but if I were to get double it'll look like this)
 

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First level match each sub to around 73 db. With the addition of the second sub the level will usually go up to around 76 db.
It should be 6db (if they are similar subs.)
If they are totally dissimilar subs you might actually get a decrease in SPL, which would be a bad thing. (very rare, but it happens.)

With a miniDSP and a UMIK add-on you should have everything that you need.
http://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4

If your subwoofer goes below 20hz, then I'd recommend spending the few extra dollars for a laboratory calibrated UMIK:
http://cross-spectrum.com/measurement/calibrated_umik.html

Then all you need is REW, which is free.

As for measuring the subs, it is easy.
You place the subs next to each other in the room, you click measure, and bam you get a chart.
Then you flip the phase on one of them and it should drop (that means the phase was correct the first time, so flip it back.)

Then you move one subs around at a time until you find the two best measuring spots that you can accommodate; then measure them together and chances-are that the results will be pretty darn good.
Apply some EQ and you're done.

If you want to get fancy, you can add some delay to the closest sub to match them better (if applicable); and then also look at the mains-bass integration overlap point to optimize that too (small tweaks to the LPF XO, delay, phase pairs, and LFE output level).
 

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Bit of a problem for myself, if I wanted another sub it could only fit in one place. Both would be along the front wall, one either side of the TV.
You can also stack them. But that will only gain you dB. The advantage of duals is to smooth out the FR with 2 locations.
 

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I would also say you should look for support from the seller of the subs, you may need a meter but when I recently purchased my dual SVS subs and was thinking about a non-standard placement they offered to walk me through the complete setup and calibration etc. Very good customer service!!!
 

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In most cases, you don't want to place the subs symmetrically from where you sit. It may help with the primary waves from the subs, but cancellations are far more likely to occur from reflected waves cancelling each other than primary waves. The main point of having multiple subs is for one to fill in where the other has cancellations. If they're placed symmetrically, you'll have identical cancellations at the same spots from each sub.
 

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In most cases, you don't want to place the subs symmetrically from where you sit. It may help with the primary waves from the subs, but cancellations are far more likely to occur from reflected waves cancelling each other than primary waves. The main point of having multiple subs is for one to fill in where the other has cancellations. If they're placed symmetrically, you'll have identical cancellations at the same spots from each sub.
Hey guys, I'm relatively new to using dual subs but was starting to calibrate my dual Acoustech pl-200 with Audyssey Multeq32. Is there a particular setting on the crossover dial on the sub that is recommended before calibrating with Audyssey? I was instructed to place the volume roughly half way up but was unsure about the crossover seeting dial.
 

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Crossover should be set to max (or defeated if your sub has that option).
 

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BTW, there's this. :)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Set the gain on both subs to the same level - around 12:00-2:00 on the gain knob is a good starting point (just a starting point, gain structure can vary greatly from one manufacturer to another). Set phase to "0" on both subs for now.

1. Connect sub #1 only and place it at the MLP
2. Do the sub crawl to determine the best position for sub #1
3. Place sub #1 in that position
4. Connect both subs and place sub #2 at the MLP (with sub #1 playing as well)
5. Do the sub crawl to determine the best position for sub #2
6. Place sub #2 in that position
7. Playing the AVRs test tone, adjust phase on one of the subs until you get the maximum SPL at the MLP (could be variable or a simple 0/180 switch) (if you have SubEQ HT, skip this step)
8. Run Audyssey, first mic position only, and "calculate"
9. Look to see where Audyssey has set your sub trim, you want it to be around -6db to -8db ideally
10. Adjust the gain on both subs by the same amount up or down as needed
11. Repeat 8-10 until you get the sub trim around -6db to -8db
12. Run the full Audyssey calibration
13. Set all speakers to "small"
14. Set all crossovers to 80hz (or, if set higher than 80hz by Audyssey, leave them alone)
15. Bump up the sub trim by 3db to 6db to your preference
16. Enjoy!

Hope this helps!
 

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BTW, there's this. :)
7. Playing the AVRs test tone, adjust phase on one of the subs until you get the maximum SPL at the MLP (could be variable or a simple 0/180 switch) (if you have SubEQ HT, skip this step)
You shouldn't adjust the phase to align multiple subs with each other. The phase knob is intended to align the subs with the fronts at the crossover frequency. To align multiple subs you need to adjust delay. Not phase.

The problem with adjusting phase is you set a different delay at each frequency since, for example, 180 degrees is 1/40th of a second at 20Hz and 1/80th of a second at 40Hz. You can only adjust the distance correctly at a single frequency using phase.

While playing with the phase may or may not make things sound better, depending on what you're listening to, it will limit how good of a setup you can do.
 

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^^^

Totally agree Kid, but this little guide is intended for those just starting and assuming they don't have the ability to adjust delay to individual subs, which would require outboard equipment (an AVR with XT32 w/Sub EQ HT being the exception here).
 
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