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Subwoofer behind screen
This thread has 13 replies. Displaying all posts.
Post 1 made on Monday February 27, 2017 at 10:23
3PedalMINI
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Other then not being ideal, any issues with the subwoofer being behind an acoustically transparent screen? Is there enough air movement to move the screen?

JL 10" dominion is going in.
The Bitterness of Poor Quality is Remembered Long after the Sweetness of Price is Forgotten! - Benjamin Franklin
Post 2 made on Monday February 27, 2017 at 11:09
highfigh
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On February 27, 2017 at 10:23, 3PedalMINI said...
Other then not being ideal, any issues with the subwoofer being behind an acoustically transparent screen? Is there enough air movement to move the screen?

JL 10" dominion is going in.

Is the screen mounted to the wall, or ceiling? I would use more than one sub, but the answer really depends on the cone's excursion and the frequency. If the screen is well-tensioned, I doubt it will be very noticeable unless the note is sustained and it hits the screen's resonant frequency.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 3 made on Monday February 27, 2017 at 11:13
SB Smarthomes
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Yes, if the screen is close enough you can get movement.  Will the screen cover the sub, or will the sub be on the floor beneath the screen?
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OP | Post 4 made on Monday February 27, 2017 at 11:27
3PedalMINI
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Thanks guys. It's a fixed AT screen. I literally don't have anywhere else to put the sub due to the design of the theater. I could maybe get it on the side but that's a big IF and in the side of the room firing out into the middle is worse then having it in the front behind the screen :/
The Bitterness of Poor Quality is Remembered Long after the Sweetness of Price is Forgotten! - Benjamin Franklin
Post 5 made on Monday February 27, 2017 at 12:04
Ernie Gilman
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You need to have a path for the actually moving air to get into the room other than by vibrating the screen.

Three examples:

1.RPTV placed in front of a fireplace because that, too, was the only place for it. There was a brick hearth* about ten inches high and the TV went on that. We had no place for the sub so we got the bright and hilarious idea of putting it behind the TV, actually in the fire area.

Worked great until we got to the side of the TV and saw that the screen was moving forward and backward with a total excursion of about an inch, maybe more. We had to put the sub in the room.

2.Overseas client's brother's place: We turned a theater with about a 12 ft 4:3 screen into a theater with a 20 ft 16:9 screen. The screen was surrounded by drapes with no real open ventilation. It was a rear projection setup. Four 18" JBL subs are in the corners of the space behind the screen (and another two in the room), which is about 400 sq ft and 15 ft high, so maybe 6000 cu ft.

Upon playing the cut from "The Art of Flight" with the gnarly bass, LOUDLY, we observed the screen moving back and forth with a total excursion of almost two inches. We improved this by careful EQ of the major resonances. Bass is still visible moving the screen when you're off to the side of it.

3.Overseas client's system: Much larger screen, about 30 ft wide 2.35 with movable masks. Same 4 JBL subs behind the screen (and another four of them in the room). The space behind the screen is about 12 x 50, with a height of about 25 ft, so a volume of about 15,000 cu ft.

Upon playing the cut from "The Art of Flight" with the gnarly bass, LOUDLY, the screen hardly moved. By "loudly" I mean that the client's engineering staff measured a power draw of about 18 kVA while playing that. The projector is a Digital Projection Lightning, so the power draw was not nearly all just audio.

Anyway, in the last case there's a huge amount of volume and a very large surface area, both of which reduce the amount of energy that will move the screen.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 6 made on Monday February 27, 2017 at 13:18
highfigh
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On February 27, 2017 at 11:27, 3PedalMINI said...
Thanks guys. It's a fixed AT screen. I literally don't have anywhere else to put the sub due to the design of the theater. I could maybe get it on the side but that's a big IF and in the side of the room firing out into the middle is worse then having it in the front behind the screen :/

If you can place the sub(s) close to the edge of the screen, it will reduce the movement but you may see ripples crawl up the screen at some frequencies.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 7 made on Monday February 27, 2017 at 13:21
highfigh
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On February 27, 2017 at 12:04, Ernie Gilman said...
You need to have a path for the actually moving air to get into the room other than by vibrating the screen.

A means 'Acoustically Transparent'. They use a coarse weave for those, although they're becoming finer, now that 4K is here.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 8 made on Monday February 27, 2017 at 14:00
Ernie Gilman
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On February 27, 2017 at 13:21, highfigh said...
A means 'Acoustically Transparent'. They use a coarse weave for those, although they're becoming finer, now that 4K is here.

Of course, you mean AT.

I typed my response, and had the edit screen open, when that information was posted. I didn't go back and look to see if someone had posted while I was editing.

Something named Acoustically Transparent is not acoustically transparent. Hell, air isn't acoustically transparent, though it's damn close. These screens are less opaque to sound than other screens, but in the end it's a marketing term and the actual behavior of the screen has to be investigated.

You can get an idea how much faith the screen maker has in this acoustical transparency if you ask if they'll take back a screen if it turns out not to be acoustically transparent enough. If they're good, that should start a dialog, but if they outright refuse to consider it, we should all be told!
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 9 made on Monday February 27, 2017 at 14:02
Fred Harding
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Or, get a sub with room matching capabilities. Syzygy makes a nice line of subs that will allow you to place the sub where the room allows, and than calibrate to optimize sound.
On the West Coast of Wisconsin
Post 10 made on Monday February 27, 2017 at 14:04
Mogul
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One of my clients put twin JL F110 subs inside a standard base cabinet and then replaced the shaker cabinet door centers with stretched fabric. They pulse like crazy at high SPL's...Pretty trippy.
"Whatever is rightly done, however humble, is noble." [Sir Henry Royce]
Post 11 made on Monday February 27, 2017 at 15:08
jrainey
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Was it mentioned if this was a woven or perfed screen? That matters alot.
Jack Rainey - Full disclosure...reformed integrator, now mid-Atlantic manufacturers rep for: Integra, Paradigm, Anthem, Parasound, Atlona, LG TV's and Metra Home Theater...among others
Post 12 made on Monday February 27, 2017 at 17:53
Audiophiliac
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How much distance between front of sub and screen? Maybe fire it sideways? Maybe space the screen off the wall with a 1/2" gap all the way around?

Only way to know for sure is to try it out. Sounds like you have no choice unless you find out it is a problem. Then you cross that bridge when you get to it.
"When I eat, it is the food that is scared." - Ron Swanson
Post 13 made on Monday February 27, 2017 at 19:25
Fins
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I took over a job where all the speakers in the theater were located behind faux suede acoustic panels. The panels didn't have any foam or insulation in them, just the cover fabric.
Civil War reenactment is LARPing for people with no imagination.

Post 14 made on Monday February 27, 2017 at 20:21
Ernie Gilman
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On February 27, 2017 at 19:25, Fins said...
I took over a job where all the speakers in the theater were located behind faux suede acoustic panels. The panels didn't have any foam or insulation in them, just the cover fabric.

We replaced velvet throughout the hall with a much thinner fabric, made with a pattern to match the existing velvet. This was the client's brother's theater mentioned above.

There was an access panel of the same material in front of the center speaker. We sold them on our expertise and on the need for the redo by putting on a DVD... and opening the access panel in front of the center speaker. They were stunned at how good the center sounded! It was a go!
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw


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