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Discussion Starter · #1 ·
I have seen basically a couple of different ways to build a proscenium using either an approach using MDF with cutouts for speakers or 2x4 framing that is simply left as is. In both cases, acoustic fabric covering both. Is one better acoustically than the other?


I assume with the MDF approach, that Insulshield should be used to cover the proscenium on both sides.
 

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I would think the frame would be much better. The MDF would block too much sound unless the speaker is mounted even with the MDF. And the Insulshield should just be on the walls in both cases.
 

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Discussion Starter · #3 ·
I thought I read earlier that the proscenium should be covered with Insulshield at least on the back side. I have tried searching, but cannot find that thread. The simple frame does seems much easier.
 

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I agree that the open frame seems more logical in that it does not create cavities with unknown resonances to deal with. However, the logical answer has been proven wrong more than once on this forum.


Looking at pictures, I've noticed that the prosceniums and columns that tend to have the MDF with the cut-outs tend to be those that had professional help. A good hint that they know something we don't.


How about it experts?
 

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Millwork is typically framed with 3/4" plywood and not with 2x lumber. You just determine how you're going to frame the substructure of the proscenium or whatever, and then create the studs and plates, and walls with 3/4" plywood cut to the right size. The resulting structure is stronger, lighter, and dimensionally stable. Creating a proscenium with an open frame approach as tlllava described is just a matter of cutting plywood walls, and then cutting holes and voids in it to create the open spaces, with more plywood to frame your boxes. I'm not sure what insulshield is or what it does, but your proscenium is nothing more than a bunch of boxes bolted together and covered with fabric.
 

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Quote:
Originally posted by BousquetP
I thought I read earlier that the proscenium should be covered with Insulshield at least on the back side. I have tried searching, but cannot find that thread. The simple frame does seems much easier.
My DE plans call for Insulshield to be installed on the back side of the proscenium, and on walls and ceiling behind the proscenium. The front of the proscenium is spec'd to be covered with Insulshield + GOM fabric


--curtis
 

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Discussion Starter · #7 ·
I can understand the Insulshield on the back of the proscenium, but not on the front. But if DE specs that out, then I guess this is the way to go unless it was something specific to your application.
 

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I'd definitely follow what Dennis recommends. I did the open frame with fabric cover. TS on all surfaces behind the speakers. I used steel studs because they stay so true. I used liberal amounts of caulk to nest each piece of steel. I ripped thin (1/4") strips off a 2x4 and screwed the strips to the steel. IMPORTANT to apply a bead of caulk or adhesive under the strips to avoid buzzing and vibrations. The strips are tack strips to hols staples when stretching fabric over the whole assembly.
 

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For a room used to watch movies with surround sound audio effects, I believe you want the entire front of the room covered with Insulshield (1" thick insulation, dyed black, manufactured by Johns Manville). This includes the screen wall, stage walls, stage ceiling, front and back of proscenium, and side walls to a point 2-3' in front of the proscenium. I believe the reason for this is to capture any reflected sound (From the side or back surrounds, or any reflections from the L-C-R that make it back to the front of the room) so that what you hear from the front of the room is only what is coming from the L-C-R speakers on their first pass.


Regarding the original question - I believe the main purpose of the proscenium is for aesthetics. The proscenium directs your attention to the screen, and adds a classier look to the room.


Hopefully someone with more knowledge about room acoustics will jump in and either confirm or correct this information.
 

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I wouldn't cover the front and back of the proscenium. The idea is to have the proscenium be as acoustically invisible as possible. Open and only covered with GOM. As mentioned this is an aesthetic structure.
 

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I think we are getting confused. The question is whether to build an open proscenium like Ted did or one with MDF panels like most DE designs. I think the matter has been settled that if doing the MDF design, cover front and back with Insulshield.


That leaves us with the original question, open or closed? I have noticed in other threads that when DE explains why he makes his recommendations, I trust the answer. That leads me to believe the MDF panel with a cut-out for the speaker is the best idea even though my gut tells me an open frame would be best.
 

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At the recommendation of DE I built my proscenium out of MDF and covered the front and back side with TheaterShield. The entire inside of the proscenium - walls and ceiling - are covered with TheaterShield. Construction and finished photos can be seen on the link below.


Tom
 

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Discussion Starter · #13 ·
Thanks everyone, I believe I will go with the MDF. However, I have a follow up question that may be related. Is there a point to having the proscenium slightly angled as opposed to having it perpendicular to the side wall?


The only thread I could find that mentioned this was here:
http://www.avsforum.com/avs-vb/showt...led+proscenium
 

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Mine is angled about 30 degrees. The purpose is to aim the L-R speakers at the sweet spot of the theater. My spot is in the center row about 13' back from the screen.


Tom
 

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Discussion Starter · #15 ·
Got it! Thanks Tom.


Very Nice theater by the way. I like that you have all the same seating throughout. I'm trying to decide if I should use the same approach. I originally thought of having some nice seats in the front row with something less expensive in the rear.
 
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