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post #1 of 5 Old 09-14-2019, 08:05 PM - Thread Starter
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Hush Box Design

I am considering a JVC RS4500 projector for a new theater build — a large laser based projector (20x8x28”). I am concerned about the fan noise in medium and high laser mode, in which it will need to run.

I have to ceiling mount this projector pretty close to row 2 of 2 (5 feet from your head). Can someone suggest principles to design a hush box ? My builder will have to do it.. Questions:

1. Should the projector still be supported by a pole (Ex chief mount) and hung from ceiling (it will need to be as high as possible ), with a box built around that ? Or is a better approach building a secure wooden box (with a floor the projector sits on), attached to the ceiling joists ?

2. I will not actively cool this box, but the room has dedicated zone AC. I will put the return air vent at the back of the room, with two supply up front. Would two large PC fans be adequate to keep it cool in the box (I was thinking an intake fan towards back of box where the projector intake is, exhaust fan near front where projector blows out) ?

3. Any sources on where I can find some hush box build plans / examples to give builder ?



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post #2 of 5 Old 09-14-2019, 08:08 PM
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[quote=blake;58559064]I am considering a JVC RS4500 projector for a new theater build — a large laser based projector (20x8x28”). I am concerned about the fan noise in medium and high laser mode, in which it will need to run.

I have to ceiling mount this projector pretty close to row 2 of 2 (5 feet from your head). Can someone suggest principles to design a hush box ? My builder will have to do it.. Questions:

1. Should the projector still be supported by a pole (Ex chief mount) and hung from ceiling (it will need to be as high as possible ), with a box built around that ? Or is a better approach building a secure wooden box (with a floor the projector sits on), attached to the ceiling joists ?

2. I will not actively cool this box, but the room has dedicated zone AC. I will put the return air vent at the back of the room, with two supply up front. Would two large PC fans be adequate to keep it cool in the box (I was thinking an intake fan towards back of box where the projector intake is, exhaust fan near front where projector blows out) ?

3. Any sources on where I can find some hush box build plans / examples to give builder ?



Sent from my iPhone using Tapatalk[/quote @Killroy just built one for his NX9. Maybe he is in a sharing mood?!?!

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post #3 of 5 Old 09-15-2019, 10:11 AM
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Quote:
Originally Posted by blake View Post
I am considering a JVC RS4500 projector for a new theater build — a large laser based projector (20x8x28”). I am concerned about the fan noise in medium and high laser mode, in which it will need to run.

I have to ceiling mount this projector pretty close to row 2 of 2 (5 feet from your head). Can someone suggest principles to design a hush box ? My builder will have to do it.. Questions:

1. Should the projector still be supported by a pole (Ex chief mount) and hung from ceiling (it will need to be as high as possible ), with a box built around that ? Or is a better approach building a secure wooden box (with a floor the projector sits on), attached to the ceiling joists ?

2. I will not actively cool this box, but the room has dedicated zone AC. I will put the return air vent at the back of the room, with two supply up front. Would two large PC fans be adequate to keep it cool in the box (I was thinking an intake fan towards back of box where the projector intake is, exhaust fan near front where projector blows out) ?

3. Any sources on where I can find some hush box build plans / examples to give builder ?



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I can offer some insights from the lessons learned from designing my RS3000 hushbox. They (projectors) both weigh about the same and are about the same size.

1) Yes, you should mount it to the ceiling via a mount pole to the joists or whatever way it can be mounted to ceiling (I had to put a 2x12 between two joists since the projector was directly between my two joists, I deep bolted the 2x12x30 to the two joists). Logic for that is that the hushbox then only has to be strong enough to support its own weight and not the projector AND the hushbox.

2) You do not need to actively cool the hushbox but you will need to create a method to actively remove as much hot air from the box as possible. You can use the theory that you want put more cold/cool air into the box than it gets sucked out. This being said, exhausting the hot back INTO the theater room will NOT be an option as it will not only warm up your room but the exhaust nosie will kinda defeat the purpose of having the box in the first place. If you can I would suggest exhausting the hot into an attic via an in-line fan and to an exterior exit point in the attic (do not exhaust directly into the attic). If you are not in a position to exhaust into an attic (basement, first floor, etc) then you need to find a way to exhaust into either your return air (not recommended since the return air system shuts off when the AC fans shut off) or to an exterior wall, or another room that you don't mind if it gets warm (maybe a laundry room). But that also brings up the fact that you need to actively bring cooler air into the box as the hot is being exhausted. Some will argue that the pressure being generated by the exhaust fan (in-line fan) would be enough to negatively pressure the cold air into the box but I would not take that change with a $24k+ projector. You can find some very silent PC based fans that will not only keep the cool air intake quiet but will also suffice the fact that the JVCs need air to enter the rear of the projector for proper ventilation. Yes, this is not that easy.

3) Not many people are building them commercially but Draper is still actively designing, building, and selling them (https://www.draperinc.com/liftsmount...spx?detail=997). If you can shell out the big bucks I would highly recommend them since the guy that actually designed them actually was nice enough to give me lots of pointers to build mine when I told him that their box was way out of my budget range. That alone was worth a recommendation if you can afford them. There are lots of OLD threads here where people show photos of their builds but you will have to deep search the forum. Not many design threads but the pictures should give you some ideas.

And about mine... it was my design that would work in my room so I don't think I can say it will work in yours. It is HUGE!!! It is heavy. But since it sits in the back of my 24-foot room I did not care and more improtantly, the Mrs. approved it.

I posted some pics of the unfinished (not painted, no port window, no wiring of all the goodies, etc) on post # 18 of this thread: https://www.avsforum.com/forum/24-di...ditioning.html

Last edited by Killroy; 09-15-2019 at 10:21 AM.
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post #4 of 5 Old 09-15-2019, 10:17 AM
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[quote=Killroy;58560944]I can offer some insights from the lessons learned from designing my RS3000 hushbox. They Projectors) both weigh about the same and are about the same size.



1) Yes, you should mount it to the ceiling via a mount pole to the joists or whatever way it can be mounted to ceiling (I had to put a 2x12 between two joists since the projector was directly between my two joists, I deep bolted the 2x12x30 to the two joists). Logic for that is that the hushbox then only has to be strong enough to support its own weight and not the projector AND the hushbox.



2) You do not need to actively cool the hushbox but you will need to create a method to actively remove as much hot air from the box as possible. You can use the theory that you want put more cold/cool air into the box than it gets sucked out. This being said, exhausting the hot back INTO the theater room will NOT be an option as it will not only warm up your room but the exhaust nosie will kinda defeat the purpose of having the box in the first place. If you can I would suggest exhausting the hot into an attic via an in-line fan and to an exterior exit point in the attic (do not exhaust directly into the attic). If you are not in a position to exhaust into an attic (basement, first floor, etc) then you need to find a way to exhaust into either your return air (not recommended since the return air system shuts off when the AC fans shut off) or to an exterior wall, or another room that you don't mind if it gets warm (may a laundry room). But that also brings up the fact that you need to actively bring cooler air into the box as the hot is being exhausted. Some will argue that the pressure being generated by the exhaust fan (in-line fan) would be enough to negatively pressure the cold air into the box but I would not takethat change with a $24k+ projector. You can find some very silent PC based fans that will not only keep the cool air intake quiet but will also suffice the fact that the JVCs need air to enter the rear of the projector for proper ventilation. Yes, this is not that easy.



3) Not many people are building them commercially but Draper is still actively designing, building, and selling them (https://www.draperinc.com/liftsmount...spx?detail=997). If you can shell out the big bucks I would highly recommend them since the guy that actually designed them actually was nice enough to give me lots of pointers to build mine when I told him that their box was way out of my budget range. That alone was worth a recommendation if you can afford them. There are lots of OLD threads here where people show photos of their builds but you will have to deep search the forum. Not many design threads but the pictures should give you some ideas.



And about mine... it was my design that would work in my room so I don't think I can say it will work in yours. It is HUGE!!! It is heavy. But since it sits in the back of my 24-foot room I did not care and more improtantly, the Mrs. approved it.



I posted some pics of the unfinished (not painted, no port window, no wiring of all the goodies, etc) on post # 18 of this thread: https://www.avsforum.com/forum/24-di...ditioning.html[/quote @Killroy as always thanks for being a true gentleman and scholar. I really appreciate you taking the time to offer your insights and knowledge to fellow a fellow forum member.

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post #5 of 5 Old 09-24-2019, 03:33 PM
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I only use a fan to pull the hot air out, making sure that I am pulling more than the projector can use. The idea is if I pump more air into the box than I am pumping out, it could cause the air flow to change, and hot air to circulate in the box waiting to get exhausted out, and as long as I can get more total air flow than the projector needs, I don't need to push any air in.

I use soundproof mufflers for both intake and exhaust, and if you run the vents for each much bigger than the ducts, sound can easily be reduced below your noise floor so where you exhaust it doesn't have to be about sound, just the heat. In my case I still exhaust it into my equipment room, not into the theater, and my cold air intake comes from the theater room. My room is not air tight because I have a fully soundproofed and muffled air circulation system for the whole room, so I am not restricting the intake air by having it in a different room from the exhaust. My equipment room runs ~20 degrees warmer than the rest of the house when everything is on, but some day I will exhaust some air outside to fix this.

Despite a vent for cool air intake and a sealed design, I decided to leave the back of the hush box open. It faces the back of the theater, most of the noise is directed out the front of the projector anyway, and with 3/4" MDF walls and an extra inch of OC703 lining the hush box, I don't hear any sounds coming from the projector, even on high lamp. Now I have the RS2000, not a 4500, so it is 10" shorter and a bit quieter to start, but all that really means for you is a longer hush box and maybe a little more room for thicker sound absorption inside the box. The RS2000 sits just under 95 cfm max fan, so I have 130 cfm of exhaust fan in the form of a 4" inline fan. Figure a lot of fans don't have a high static pressure, and if your duct work is long or restrictive you could cut your flow down significantly. I may end up moving to a 6" fan to pull over 200 cfm just because I go through the muffler system that is a little restrictive and I would rather be safer than so close on tolerances. It is really bad if you exhause 92 cfm and the projector is blowing 95 cfm.. that is a lot of hot air sitting in the box cooking the projector...

I recommend building a shelf off your ceiling instead of hanging the projector from a pole and suspending the entire hush box on that pole, or even building a hush box around it. I originally set mine up to hang from a pole and then was going to have the entire hush box hinge off the ceiling to swing down and give access to setting up the projector. I switched it out to a shelf using 4 lengths of allthread and a 3/4" baltic birch shelf, then enclosed it in after the projector was dialed in. The sides and front are removable so I can get to it easily, and I was able to tuck it up fairly tight to the ceiling, where with a pole mount I was 2" down from the ceiling which would have put the projector and hush box almost 15" down from the ceiling. Every inch counts when your back row is on a 14" riser and directly below the projector. The other reason I opted to leave the back open is if I sealed it, I could potentially be sucking air around the lens opening, which I chose not to use glass to seal up because I already have an anamorphic lens, and I was worried that over time, air flowing over the lens would build up dust, and cleaning lenses is a pain. Open back means no static pressure around the lens opening, so no problems there.

If you are wanting to seal yours up completely, use Edmunds Optics glass, they have a variety of AR glass in various sizes, but be sure to angle it so the light from the projector isn't reflecting back onto the projector lens which could cause your projected image to ghost.

One more thing, I built a timer relay system that will turn the fans on when the projector comes on, then leaves the fans on for 10 minutes after the projector turns off. This way it is all automated and I don't have to worry about forgetting to leave the fans on or to turn them off later.

I have details in my theater build thread in my sig, although I have not updated it in a while.
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