I know this is a really stupid question but is there a rule of thumb for the depth of the speakers in relation to the screen. Every theater we have ever done has placed the speakers around the screen and not behind. I've seen a lot of applications where monitors or bookshelf speakers are set back a little but I was looking to put in-wall speakers directly behind the screen and have the screen mount directly to the sheetrock. Is it possible? I'm mostly concerned with the woofer air movement affecting the screen.

I've installed in-walls behind an AT screen and it works perfectly.

Thanks for the response! I just didn't want to do it and whenever they crank the volume the screen starts to move. I understand the screens allow air movement but I didn't know if it was enough to overcome any potential effects from the speakers.

We've done dozens of acoustically transparent screens and never had a single problem. We have used some pretty massive speakers behind them as well (4' tall custom PSB speakers, large JBL Synthesis recessed in niches etc). One consideration you would want to address though...does the screen you are getting come with an additional layer of black material that goes behind the screen?

We tried a Draper screen to meet budget considerations at one point and it did not have black backing material so we could see the wall / speaker grills / speaker drivers. We decided to leave the grills off in the particular install. We had to paint the wall black and got some speaker cloth to cover the speakers.

I was going to try Snap's screen at my house first. Luckily it comes with a black scrim screen and I also have black felt (indoor/outdoor carpeting) on the wall as well. I'm planning on moving in a year so I don't want to invest into something much more expensive. I built a stage that had speaker inset into it but I'm redoing the top to accomodate storage for pillows and blankets. So I want to move the speakers.

It is not a good idea to mount them flush. Here is the problem. The screen will reflect some of the sound waves back because at higher frequencies, it is a reflector. The front of the speaker is usually very reflective so the sound bounces back and forth creating comb filtering (notches taken out of the response of the speaker). It definitely changes the timbre of the speaker and is not correctable using EQ (since both the sound and its reflections always remain the same).

Screen manufacturers talk about high frequency loss but not this problem.

You can hear this effect rather easily. Take a piece of your screen material, have it stretched on a frame, and then have someone swing it in front of a speaker as you listen at your normal position. You will hear a distinct change and not for the better.

A good solution which you should follow even if you have a gap, is to tilt the speaker. You should do that anyway by pointing the speaker to the sweet spot (doing so means that the best sound of the speaker, the direct sound, is heard by the guy paying for it). By tilting it you are reduce the bouncing back and forth. You can hear the effectiveness of this in the above test.

Would it be better to lose the enclosed cavity of wall therefore possibly reducing the response of the speaker or following your advice to reduce the comb filtering effect? I could build an MDF box for the speaker and place it at an angle in the wall. Either way, thanks a lot of the useful info!

I had a problem where if you mounted a dalight perf screen to close to the grill frames of triad speakers the outgasing from the triad speakers starts to disolve the screen material, turns it into goo.

I am too dense to follow your proposal :). Do you mean there is an existing cavity that doesn't allow the speaker to tilt at all?

(re-read the OP, he's using inwalls)

Drew,
The phenomenon is called 'coupling'.

Woven screens perform slightly better than perfed in this regard, but even an inch of space between the baffles and the screen will keep the perfed screens from coupling to LCRs. You will want a lot of breathing room for subs behind a screen, regardless of the screen material.

The best advice to prevent this is to space the screen off the baffles of the speakers (or the wall, in this case). Use some strips of MDF or something, paint them black, or get some black velvet or veltex material and they will not even be visible.

Or it's lacking proper explanation!

The wall is existing and it's only 2x4 construction. I was hoping to place the in-wall speakers flush in the wall and place the screen over the speakers. The gap between the speakers and the perf screen would be minimal. I was thinking about furring the screen out 1" to accomodate some sort of linear strip lighting. Ultimately there isn't a lot of room to angle the speakers. Angling the speakers would require some sort of backbox otherwise the in-wall speakers wouldn't be in a "cabinet."

So yes, there isn't an existing cavity that allows the speaker to be tilted without a lot of work.

For what it's worth, we have the same issue after electricians put some stuff somewhere they weren't supposed to. The center speaker has to be too high so we have to go acoustically transparent.

2x4 wall with no real ability to tilt the speaker since we spec'd Triad Inwalls with the full back box.

Does comb filtering occur at higher frequencies, mid's, low's, or all frequencies? If it only affects the high range wouldn't simply mounting the speakers higher and pivoting the tweeter down help reduce this effect?


Thanks Rick! Coupling is what I was affraid of. It should not be a problem to build it out the screen an inch or two to prevent this. Plus I have some black velvet leftover from the countertop I'm replacing so wrapping the framing material won't cost me anything.

And I only plan on using front ported subs behind the screen. That's ok, right ;)


And you've done this without bringing the screen off the wall any more than what the standard screen brackets provide?

All, I understand that this is the common practice in rooms where you have a 3' space behind the screen to place large towers or monitors. I was looking for more or less the effects of in-wall speakers with a screen mounted directly on top of them.

Wave propagation is different for low frequencies (below about 300 hz) than higher frequencies. There, the waves travel in all directions whereas above, they act more like beams of light. So it is not a problem for low frequencies. At very high frequencies, the screen and imperfections will cause enough interference as to make that a non issue also. So the problem is mid to mid-high frequencies. If you have a two-way speaker, then moving the tweeter helps some but won't fully deal with the problem.

Speaking of bass, you may face a more serious problem there. That is, the energy from the main driver may move the screen enough to make the picture in that area to be out of focus! Or resonate and move with sound. Perf screen would likely be a non-starter because of this. AT screen will do better but you may still see it it resonate.

Answering your previous question, you can tilt the speaker by attaching some furring strips to it. The Triads are MDF so you can just nail these to it to tilt it. It won't be a pretty install :). But it is behind the screen so should be OK.