Modifying two Descents for HT

[Tj Bassi]

What started out as a basement two-channel audio room project has changed course and is now slated to be a dedicated theater. With two young children in the family and many more in the neighborhood, I can see how my wife favors the theater idea.
Since the theater is going to be one of those 'art-deco' inspired designs, the speakers will have to be inwalls. Looking over my pile of spare hardware for the build, I gave thought to converting two unused Descents (original, not i's) into front-wall mounted subwoofers.
Seems like a strange idea, but I wonder if it can be done? On paper, I could remove the drivers and electronics, and mount each driver in a small enclosure under the projection screen. The plate amps and controls could be mounted adjacent to the woofer arrays.
The only reason for doing this, is I already own the two Descents and this would help keep the build within budget, and it seems like a fun thing to try.
Any opinions?

Tj

 

[C.A.P]

Better sub solutions can be done with that type of build. the TRI force woofer design is what makes it so efficient. They cancel each other out. The box is all part of the equation. I would look into IB or servo subs made by Rythmik. I run one for my HT and its GREAT. JMHO!

 

[zaphod]

page 11 of the Descent manual discusses putting the Descent into a cabinet.

 

[Tj Bassi]

Thats a good find Chris, thanks. As long as the front wall framing (it is pretty deep from the concrete wall) allows the correct volume the Rythmik idea should pan out, and the price is reasonable.
Unfortunately I dont have the space to house the entire Descent, but thanks for the info, I had seen that in the manual.
Brings up a point for which I have not found the answer; in a HT where the sub is either mounted in the same wall the screen is attached to, or sitting on a front stage, does the sub vibrate the screen and hence the image?

TJ

 

[JonFo]

TJ, mounting subwoofer drivers into the wall that your screen is on will cause it to vibrate.

Visibly? not sure, but definitely not ideal, especially from a sonic standpoint. As those vibrations are distortions.

Now, if you build an IB manifold with dual (or quad) opposing drivers, then all that shaking energy is canceled out.
How much space (in Cu. ft.) do you have behind the screen wall?


Also, ideal sub positions are centered on the front wall and if doing 2, another along the middle of the back wall.

Are you doing front projection?

Where are you putting the Center ch. (above, below, behind the screen)?

 

[Tj Bassi]

Jonathan,

I'd have to take firm measurements; the front wall is 15.5 wide, 9 feet high, and is studded approx 10 inches from the concrete wall it runs along.

The plans are front projection, with the center below the screen.

This was originally designed to be a two-channel room, so we are in the initial 're-planning' stages of drawing it up for theater use. The room size is 18.5 x 39, but the stairs from the upper level (this is a basement build) divide the room into a main room of 18.5 x 28, with two hallways running to a media storage room behind. I quoted the front wall as 15.5 useable, because the main beam running lengthwise leaves us with a offset soffit on the one side, but it will make a nice entrance hall.

I like your idea about the front/rear subs....more so since we are planning a second-row raised seating area, but obviously this is where you were going with the center channel position question.

Tj

 

[JonFo]

TJ, that's not enough space behind your front wall for an IB alignment. It usually takes hundreds of CuFt minimum, and I figure you might get 150 or so out of that space.

My advice, just re-use one descent in front under the center channel and the other on the opposite wall, behind the second row (exact positioning to be determined by the guidelines in this paper).
Combine that with the Audyssey Sub EQ (which handles two subs) and you'll have very good low-frequency performance in the room.

And yes, with a raised second row, getting the center placement balanced with the screen position is always tricky.

Your ceiling is too low to support an above the screen position, so below is where it must go.

The challenge is to get it high enough and aimed so that you cover both rows.

Oh, and do plan to keep the 'back' row at least two or three feet off the back wall if you can.
Worst position for a listener in any room is to have their ears be within a couple of feet of a wall. Bad, very bad ...