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Discussion Starter · #1 · (Edited)
There is an interesting thread going on at another forum on double bass arrays.

For those that don't know, the idea is if you have a multi driver two dimentional array of subs along the front wall such that the distance between each driver in the vertical and horizontal merideans is twice the distance between the outermost driver and the wall, you effectively get an infinitely wide and tall plane of low frequency waves coming at you. Imagine the right and left walls, the floor and the ceiling are mirrors... looking out, you would see the bass array having the same spacing going out as far as you can see. If you put the exact same array of drivers on the back wall, wire them exactly out of phase and delay them appropriately, then they will essentially catch the low frequency waves as they hit the back of the room (the coupling of the output would cause perfect cancellation). The Harman White Papers attemp to address room modes but only account for the four walls. This addresses the four walls as well as the floor and ceiling. The one requirement for both configurations is a rectangular room and no bass absorption. If set up as described, the frequency response should be the same as one of the drivers in an anechoic chamber no matter where you are sitting. Theoretically, low frequency modes are completely removed (at the expense of room gain). The closer the subs are spaced, the higher in frequency this phenomenon continues. So, the idea is to have enough drivers to cause this unaltered frequency response to go up to about 80 Hz. And, if you have enough large drivers, you can go as low as you want and dial in whatever curve you want. Depending on the amount of space you have, you can go small sealed with a Linkwitz transform curcuit (LTC), large sealed (IB) or LLT. Obviously the more drivers you have, the less each one must move to have the desired output at the desired frequency, and the less each one moves, the less distortion you get.

As an example, in a room that is 20' wide and 8' tall, you could have 8 drivers on the front and rear walls (so 16 total); basically, there would be two rows of 4 drivers on the front walls and two rows of 4 drivers on back wall. Horizontally, they would be spaced 5' apart (so the outer drivers would be 2.5' from the side wall) and vertically, they would be 4' apart (so the drivers would be 2' from the floor and ceiling). Sure, that's a lot of drivers, but the only need for a PEQ would be dial in your preferred house curve... and with less EQ comes less distortion. Obviously an LLT would need the least EQ, but having ports could mess with the mirrored effect; to what extent is unknown. Doing the same with sealed boxes (whether small or extremely large) would require a bit more EQ, but it's still less and easier to implement than with traditional subs. Obviously each design (LTC, IB or LLT) has it's own pros and cons.

For those with money to spend or those who just want the best or most even bass response, this looks to be a solid answer to taming our in room bass response. It would also look pretty impressive (to say the least) :D!!!!!!
 

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Interesting concept, apparently very popular in Germany. From what I read it only works in a perfect rectangular room (cuboid shape). Response is affected by any large piece of furniture. Nonetheless it's definitely an option for those who can afford 8 subs and meet the room requirements.
 

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Discussion Starter · #3 ·
I know we aren't supposed to link to other forums... but please excuse this one:

http://www.avsforum.com/avs-vb/showthread.php?p=15483815#post15483815

It would be very hard to reproduce this one persons personal testing of his own double bass array (plus I don't think it would be fair to him).

The post detials his in room measurements of his double bass array. The results are very interesting to say the least.
 

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The DBA represents something of a Holy Grail with respect to achieving deep, even bass in domestic rooms. I'm disappointed to see the topic underrepresented hear and other audio sites. I encourage other posters to share the DBA concept with the community!


ARS
 

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I have a friend who is thinking about putting together a small dedicated home theater room. I'm trying to help him out with the most affordable way in getting somewhat even frequency responce and decay time. I've gotten interested in a single bass array IB with damped back wall for a basis for room treatment.

The idea I have currently for the front wall is to put L, C, R and 4 15" subs flush in a sealed brick wall. The subs would be situated 1/4 and 3/4 positions horizontally and vertically. Behringer dcx2496 would be available for EQ with some kind of a AVR.

Room is 2,5m (height), 4,1m (wide) and 5,2m (lenght). Listening distance is about 3,1m for the main listening position. No need to worry about other positions responses.

In my small understanding of SBA he should put massive dampening to the back of the room if he wants to get even response for the region under 100Hz. If he mimics FoLLgoTT:s idea of using rockwool, then how much is enough? Will 0,8m or 0,9m work?


Edit.
I seem to have forgotten to express the most basic questions.
What does this plan sound like?
Problems, things to remember?
 
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