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Multiple IB manifold questions/scenarios

855 Views 27 Replies 8 Participants Last post by doublewing11, Mar 9, 2014

audiovideoholic

Discussion Starter · Mar 6, 2014

Ok. Just like the title suggests, what can be advantageous IB placement options with 2 or more manifolds that each house multiple drivers? My options are pretty much entire ceiling surface area for attic manifolds, behind front screen, and partial sections of rear wall (has limitations for treating wall if used. Will explain below).

I asked about an IB system that used both the front and rear walls quite some time ago but never got any solid feedback on such a system. I would imagine that two IBs that literally send a wave towards each other (or as much of a wave as can possibly produce) would have some anomalies, maybe?

I have had doubts about creating an IB behind my AT screen when the design calls for the drivers to be directly behind the fabric. I have up to 18" of room between the baffle and screen to work with. I currently have all my drivers arrayed horizontally below the screen (18' of speakers side to side) with one stacked on the outer most drivers next to each left/right wall. This sealed setup is pleanty loud across the front two rows but the FR is all jacked up below 38hz. I literally have a plateau from 38hz on up with a little bump around 20hz which I assume is room gain or some other room interaction.

Are there any strategies for multi manifolds in attic placement only? In attic plus front or rear or any combination of the three?

My front wall has aprox 700cuft to work with. Rear wall has three sections that could each house 60cuft but this would leave me unable to heavily treat the rear wall. FOH has given me a lot of advice to help me come up with a plan to use as much depth on my rear wall as possible for trapping. So I think the back wall may need to be spared for treatment unless there is a design which uses the rear wall specifically paired with other manifolds as my two stage riser is a bass trap designed by D.E. it does some good but I'm sure a bunch of well placed mass across the rear wall will show greatly improved results.

All my current drivers are 21s and am trying to get pallet shipping quote on the 24s which would be 8 drivers. I'm not in any hurry because I have to update my LCRs first so the 24s price increase may push me to other IB capable drivers. But total IB displacement of drivers will be equal to aprox 10 21s and 8 24s.

Just curious as to how you all would lay out several manifolds. With my limited 700ish cuft behind the front baffle I could possibly place some drivers behind the screen since there wouldn't be more than 6-8 of them. I just fear an unwatchable screen from screen movement. I'm working on a plan to even further decouple my false screen wall from the concrete floor/stick framing but enough air movement will make it flutter no matter what I guess. I've thought about going rear projection when update my LCRs and completely hold off on the sub upgrade just for vibration reasons alone but fear the cost of the glass/screen! I'd also have to cut a hole into the structure for throw reasons/reduce the cost of such short throw mirror system. Ok off of fantasy land rear projection. The fact that I fear screen vibrations is quite clear lol.

So what would someone like D.E., Seaton, Danley, YOU scientifically read AVSers design?

This next little bit is more fantasy land but doable if would really be worth it.

I still would like to build atleast 2 FLH 21s before my ht endeavors are over but 4 would be even better! 4 of these modeled with the Mal 21s with more SPL than all 10 of my sealed 21s. I don't know if the design will work with the FTW 21 and I only have two Mal 21s left. I know there are some that have mixed horns with both sealed and ported subs with good results but just don't know about it with IB/overall sub redo. The horns would spread across front wall under the screen from 1/4 point to the other 1/4 point with 4 of them.I want to truly be done after this! I don't need flat response from seat to seat throughout all three rows but would like as close as possible without limiting the two center seats of rows 1 & 2. The "only" reason I brought this up is because I would never build the FLHs for any other room other than the HT so essentially its within the IB build or most likely never.

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