Feedback on proposed IB SBA

[dkelly60]

I would like some feedback on my plan for a Infinite Baffle Single Bass Array, for my new audio and home theater room.

The room is about 8m x 5.6m, 2.7m (26' x 18' x 9'), it it has a store room between the garage and the home theater. I am currently planning a baffle wall on the West which could pass through the wall into the storeroom.
It would provide about 30 cubic meters of space. The idea is to use an array of 8, dual manifold 15" Dayton Audio UM15-22 drivers which should provide an approximate plane wave up to 120hz into a 70-80cm bass trap wall on the East end. The available space is about 8x vas, though I guess you could open the storeroom door and it would be unlimited.
The room will be sound isolated with whisper clips OSB green glue drywall. One question I have is I have about 8m from the storeroom door to the master bedroom, is the bass likely to be a problem? Our house construction will be brick veneer.
I also considered a array of 6 dual manifold IB318 v2 divers which would cost about the same and have a little more output but only be plane wave to 90hz.

[ThomasW]

Hi

Interesting design...

Given all the structure between the IB and the bedroom I doubt that there will be much to be heard/felt, unless the IB is being driven to extremely high output levels. If that's the case all bets are off since the vibrations will travel throughout the structure.

Looks like a fun project don't forget to post pics...

[dkelly60]

I have a question on baffle strength if not using manifolds, IF I used 8 single IB318 without manifolds how much problem is the mechanical vibration? How strong does the wall need to be?

[ThomasW]

Since the drivers are so heavy with big motors flat mounting them dictates a massively reinforced wall. Reason being any vibration of the wall decreases the output from the array.

Some have gone so far as to do concrete and angle iron reinforcing.

The easiest way is stiffen everything up is to put matrix/grid of front to back bracing between the baffle wall and the rearwall of the enclosure.

Manifold are of course the best choice. But I don't think it's a good idea to run manifolds as high as 120hz since frequencies that high are typically better served by the use of good woofers.

[dkelly60]

There is still a way to go before the build but I am leaning toward the front mount with 8 FI318's I just realized that the manifold arrangement would require me to make access panels as I need to preserve space and would have no access behind the manifolds.

[ThomasW]

OK, let us know which design you decide to go with.

At this time I don't have a specific link to direct you, but a bit of time looking through older threads should result in finding threads where the builders have used wall mounted the drivers and massive reinforcements to keep the wall from flexing.

[dkelly60]

I have been thinking about the proposed design from the space point of view. Does the shape pose a problem? What about room modes inside the baffle area. In smaller boxes the size means that the resonant modes are above the subwoofers response, but wont an IB have modes in the frequency range of the sub?

[ThomasW]

Typically the rearwave of an IB is firing into a room, not a closet. This means there is no impact of the rearwave on the front wave.

With your vented closet design there will of course be nulls, my guess is that they could be modeled with a room mode software. But remember this is the rearwave not the sound you hear. So it's not really a problem since you have the ability fill the closed with damping material. That should mitigate most if not all issues created by the smaller enclosure.