Bass Tuning in Room - Which way to go? - AVS Forum
Dedicated Theater Design & Construction > Bass Tuning in Room - Which way to go?
Lic265's Avatar Lic265 12:05 PM 05-07-2012
Hi
Recently I finished my room and am having issues with the bass being "booming"

( http://www.avsforum.com/avs-vb/showt...t=farm+theater)

I have adjusted the NAD 15 preamp settings and the Velodyne sub settings with some improvement, but it seems to be a function of the room

Do i go ahead and spend the money on the Odyessey program in the NAD; or invest in acoustic treatments?

Thanks
G

Brad Horstkotte's Avatar Brad Horstkotte 12:32 PM 05-07-2012
First (and most effective) step is to ensure that you've got the best sub and seating location, via doing a "sub crawl" (preferably with measurements) - have you tried that yet?
J_P_A's Avatar J_P_A 12:57 PM 05-07-2012
+1 to what Brad said. That would be the lowest hanging fruit.

I'll add that if you don't have any acoustic treatments, from what I've read they will improve the entire audio experience. Not just your bass. With that said, the treatments necessary to address bass will generally require much more space than the treatments for higher frequency content.
Lic265's Avatar Lic265 01:03 PM 05-07-2012
Thank you for your suggestions- how does one do a "sub crawl" ?
J_P_A's Avatar J_P_A 01:05 PM 05-07-2012
The idea is to put the sub in the prime listening position, and then play some bass heavy content. Then you crawl around on the floor listening for the position in the room that sounds the best. That's where you put your sub for the best sound. Obviously there are some limitations. If the best sound is in the middle of the floor somewhere, you probably can't put your sub there, but it's still a great way to optimize with the positions you do have available.
SierraMikeBravo's Avatar SierraMikeBravo 06:52 PM 05-07-2012
Quote:
Originally Posted by J_P_A View Post

Obviously there are some limitations. If the best sound is in the middle of the floor somewhere, you probably can't put your sub there.

Using a single sub, the best location for a sub IS in the middle of the floor. However, there are ways to mimic that location without the sub actually being in that location. Best way to do this is use two subs. Single subs in a room are not generally the best idea for a number of reasons.
GRBoomer's Avatar GRBoomer 07:26 PM 05-07-2012
As SMB said, you can create a virtual sub by having it at the intersection of two other subs ( say along two opposing walls). You may need to tweak phase and equalize with a parametric equalizer- only subtract. Do not add.

Search here and the web for multi-subs.

Here is some wisdom and wisdom2

Typically 3 to 4 subs helps get you there. They do not all have to be big monsters playing deep and shaking the walls. They just need to cover from the lower modal frequency that your room can support up to the Schroeder frequency (200-300Hz). Best placement may lead you to non floor locations and along different walls. Corners will stimulate room modes and lead to boomyness.
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Then you also need acoustical treatments.
Most typical around here is to fill the corners with super chunk bass traps. OC703 stacked floor to ceiling with a 24" to 34" faced diagonally into the room.

More recently people are building bass traps with regular insulation - "pink fluffy stuff". Insulation deeper than 12" has the best absorption coefficient, at the expense of size/depth. Costs are low too. Just need to have a design that prevents compression of the insulation.

You can also find the peaks along the boundary of the room and surgically place low frequency absorption to broaden/lower the Q of the peak and help fill in the valleys of the response.
Lic265's Avatar Lic265 06:54 AM 05-08-2012
Thanks for the advice; i have not thought about multiple subs.

Currently i have a 15 inch Velodyne in the right front corner of the room; i have another 10 inch Rel sub that i am not using. Should i use the REL; or look for a more similar Velodyne? Can they both be in the front corners?
airscapes's Avatar airscapes 07:48 AM 05-08-2012
Quote:
Originally Posted by Lic265 View Post

Thanks for the advice; i have not thought about multiple subs.

Currently i have a 15 inch Velodyne in the right front corner of the room; i have another 10 inch Rel sub that i am not using. Should i use the REL; or look for a more similar Velodyne? Can they both be in the front corners?

Conner of room is bad probably why it is booming now, do the crawl, it is not hard.. worked it out in about 15 minutes first time I tried it. I was going for opposite end of room from mains (behind seats) and found a location that worked great after a bit of phase and volume adjustment.
Just dump the sub in you seat and start crawling around in the area where you think you would like to put it. Loop some good bass on the CD player, Genesis Firth of Fifth work great for me. You will know when you find the spot.
Brad Horstkotte's Avatar Brad Horstkotte 11:10 AM 05-08-2012
Quote:
Originally Posted by airscapes View Post

You will know when you find the spot.

That's what she .... nvm
BroncoSport's Avatar BroncoSport 03:14 PM 05-08-2012
I always scratch my head when the "sub crawl" is brought up. Yeah it's a good way to find the "sweet spot" but in reality no one wants to place their sub where the "sub crawl" says it should be. Well unless your super lucky and the crawl tells you that up front or behind your AT screen is EXACTLTY where it needs to be! After all that's where most of us want and or place the subs...isn't it?
SierraMikeBravo's Avatar SierraMikeBravo 03:18 PM 05-08-2012
^^^^

In order to do that, you need use at least two subs which was described above.
Lic265's Avatar Lic265 06:20 AM 05-09-2012
So i did some experimenting:
1) Did the crawl as described.

2) Moved the front Velodyne sub from the corner from 2 feet off the back and side wall to 3 feet side to side. Much less booming. Also hooked up a older, smaller REL sub along the opposite side wall about 1/3 from the front. Seemed to "reinforce" the bass without any ill effects.

3)Unfortunately; the REl sub has developed a crackling noise - increases in intensity with volume; not a typical hum. Guess the electronics are blown.

Is there any concern with using 2 dissimilar subs in this setup?
mcluma's Avatar mcluma 09:07 AM 05-09-2012
Quote:
Originally Posted by Lic265 View Post

Thanks for the advice; i have not thought about multiple subs.

Currently i have a 15 inch Velodyne in the right front corner of the room; i have another 10 inch Rel sub that i am not using. Should i use the REL; or look for a more similar Velodyne? Can they both be in the front corners?

I have multiple subs in my home cinema set-up and you do not have to drive them that hard to get a very good experience.

I also used the audyssey speaker set-up to get the timing right
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