Official Rythmik Audio Subwoofer thread - Page 545 - AVS Forum
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post #16321 of 16323 Old 07-21-2014, 11:52 PM
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Originally Posted by rcohen View Post

Here are a few suggestions to try:
1) One in each corner, time aligned (most power, canceling some room modes)
2) At 1/4 & 3/4 positions on the front and back wall, time aligned (cancels additional room modes)
3) At 1/4 & 3/4 positions on the front and back wall, but invert polarity for the back pair, and add delay to the back pair of a bit less than 1 ms/ft for the length of the room (Double Bass Array - cancels most room modes)
dazzdax

Midwall placement has been documented as one of the very best positions of subs. Best if you can have all four subs on their own wall, but if you want to stack them, front/back or left/right wall is also good. Always use opposing walls, if just going with two walls.
If you do sidewalls midplacement, do not set XO higher than 80Hz due to localization, but honestly I don't think you will localize a F15 even at XO=100Hz, but this is something you can try out.

My recommendation is not to invert polarity for a backwall sub, you might get it look better at the XO freq, but it might get worse at other freq., it has not worked out for me to do it like that. If you set a distance to the sub in your AVR, set the distance to the sub farthest away, then the phase on that sub could be 0 on the sub phase dial. Then you delay the sub that is closer to you at MLP on the sub phase dial. If subs are at the same distance you can have both subs at 0 and just play with the AVR phase/distance adjustment.

Not sure if you already have, but just in case, with more than one sub you really need a measurement mic and a SW (like REW) to make the best call on placment and phase adjustments, no matter how golden year you are, you are likely to get a much better integration by doing simple freq. sweeps and see what happens when you play around with placement and settings.

Good luck!
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post #16322 of 16323 Old Yesterday, 06:46 AM
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Originally Posted by Danne2 View Post
dazzdax

Midwall placement has been documented as one of the very best positions of subs. Best if you can have all four subs on their own wall, but if you want to stack them, front/back or left/right wall is also good. Always use opposing walls, if just going with two walls.
If you do sidewalls midplacement, do not set XO higher than 80Hz due to localization, but honestly I don't think you will localize a F15 even at XO=100Hz, but this is something you can try out.

My recommendation is not to invert polarity for a backwall sub, you might get it look better at the XO freq, but it might get worse at other freq., it has not worked out for me to do it like that. If you set a distance to the sub in your AVR, set the distance to the sub farthest away, then the phase on that sub could be 0 on the sub phase dial. Then you delay the sub that is closer to you at MLP on the sub phase dial. If subs are at the same distance you can have both subs at 0 and just play with the AVR phase/distance adjustment.

Not sure if you already have, but just in case, with more than one sub you really need a measurement mic and a SW (like REW) to make the best call on placment and phase adjustments, no matter how golden year you are, you are likely to get a much better integration by doing simple freq. sweeps and see what happens when you play around with placement and settings.

Good luck!
This varies from room to room, but I have not had good luck with center wall placement with a sub on 4 walls (not enough power and poor frequency response). On the other hand, center wall placement on the front and back walls gives me pretty good natural frequency response. Corner placement gave me the best results overall, because I have a large room, and benefit from the extra power. As long as there are no nulls, I can EQ the rest flat. In a smaller room with no headroom issues, I think that the center wall or 1/4 3/4 placement may be better. It comes down to experimentation. (My room is longer front to back.)

The interesting thing about the double bass array stuff is that it can cancel out more room modes and create a much larger sweet spot. It's critical to set the delay and gain at the back to coincide with bass from the front wall hitting the back wall to cancel out the reflection. If you don't do that, it will cause problems. I haven't tried this myself, but others have had good results, and the REW room sim predicts good results for me. Someday, I will have to try it, to see if it's worth the power sacrifice:
Double Bass Array (DBA) - The modern bass concept!

I have found that low distortion subs like the Rythmiks can handle higher crossover frequencies without too much localization problems. If you use careful placement, going above 80hz can have definite frequency response benefits. For example, if you're struggling with room modes from the front to back axis in the 80hz range, you can put subs in the front and back to cancel them out (even without that polarity inversion/delay stuff). Even with great full range mains, they won't have that benefit, so a 100-120hz crossover point can help in that case. More details:
http://www.soundandvision.com/conten...nd-tell-part-1
http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf
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post #16323 of 16323 Old Yesterday, 08:26 PM
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Whelp, just placed my order for two LV12Rs for my living room / home theater. I'm looking forward to getting them set up and running some frequency response tests on them! They should be here by next Tuesday - not bad for 140 lbs shipped to Toronto from Texas. Thanks to Brian for the quick shipping (same day).

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