Truss space between floors

[darrellh44]

Hi,

Has anyone tried using the truss space between floors to isolate the rear wave? Instead of solid joists between floors, my house is constructed with 2x4 open trusses that are 15"-16" high. My guess is most 2-story houses built in the last 20 years or more use this type construction. In my case this means there is over a 1500 cuft of space available for mounting an above floor IB manifold ala the outie method in my 2nd floor HT room.

One obvious downside is the rearwave will travel throughout both floors of the house. This will be especially true for the downstairs since it will only have a single layer of 1/2" sheetrock to block the sound. There may be a way to limit this by opening up the ceiling directly below the manifold (luckily this is the utility room ceiling) and force the rearwave only into the space over the garage. This should still allow around 600 cuft for the rearwave.

Can anyone think of others reasons/experiences why this won't work?

Thanks,
Darrell

[ThomasW]

CJ used this idea for his IB. His trusses are 24" deep. Unfortunately his build was documented on a HT forum that has been taken down.

The thing is there needs to be depth behind the woofers. This is why better designed box subs are deeper than they are wide.

If you're willing to go to the extra work of lining the area behind the woofer with layers of compressed fiberglass board insulation, having a 15"-16" space might work, but no guarantees.....

[darrellh44]

Thomas,

Thanks for the reply. It sounds like the better option then is to build a manifold in my attic above the HT room...I just worry about the neighbors will think.

How much impact does the outie vs innie mounting have? Has anyone hung their outie from the ceiling?

I have one other thing that's been puzzling me. In the installation guides on the Cult forum, it says the opening for the IB should be centered between the front main speakers. Assuming the mains are setup symmetrically in the room, won't this put the IB midway between the side walls? Isn't this bad for room modes?

Thanks,
Darrell

[ThomasW]

darrellh44 said:

I just worry about the neighbors will think.

The sound coming from the attic won't be any louder than the sound coming from the room where the sub is..

How much impact does the outie vs innie mounting have?

They're fundamentally the same

Has anyone hung their outie from the ceiling?

There's one in the gallery pages

I have one other thing that's been puzzling me. In the installation guides on the Cult forum, it says the opening for the IB should be centered between the front main speakers. Assuming the mains are setup symmetrically in the room, won't this put the IB midway between the side walls? Isn't this bad for room modes?

Depends on the geometry of the room and the placement of the IB. This is the reason for the recommendation to check placement before cutting holes in the structure.