Hush Box material, MDF, Particle board or plywood

[tomwu]

Hi all,
I recently got a Christie projector which is huge and with very very loud (>60 DB) noise. Basically I need to use a noise cancellation phone to watch movies. So I'm planning to build a hush box. 

So basically the shape of the hush box will be 1.2 meters by 0.9 M, height 0.55M. Well, this will be just a rough figure. Since it's so huge, I don't want to hang it above my head as the lens is a short throw lens. It will be put on a cabinet instead.

It will be a generic hush box which air flows as 'S' through the box.

Now it's time to choose the material to build the box, for best soundproof/rigid purpose. Those materials are available from Bunnings:

1. MDF, which it has 25mm think and 12 mm thick. If I choose 2 12mm board, put some damping material (such as a used tower) in between, is it going to be better in reg to soundproofing? I'm just worried using 12mm board, it might not be strong enough.
2. We also have 19mm particle board, stronger than the 12mm MDF I believe.
3. And 17mm ply wood, which looks pretty strong.

Not sure how do you find similar thickness ply wood/particle board/MDF, which of those material is the best for soundproofing?

interior of the box I will try some different material to test the outcome. i.e. acoustic foam, acoustic mat, towels. I heard towels are actually very good on sound absorb.

[Clarity Calibration]

An area that interests me also. Please keep us updated on the build!

[Kezzbot]

Thicker the better obviously when your talking sound transfer through. 12mm would be fine. 

 

Denser the better, so which ever is heavier would probably be the best. But i bet the difference would be so small its not really worth worrying about.

 

IMO the choice in building materials comes down to how you want to construct it. If you want a bit easier then use Plywood and glue and screw. But you will have screws showing.

 

Or use MDF and glue and clamp. no screws showing.

 

You could also countersink and fill the screws or cover with a veneer.

 

You could add another "S" bend in the mix and a quiet fan or two to pull the air through the baffle.

 

 

 

 

[tomwu]

Thanks guys.

Yesterday went bunnings alexendria and got some 25mm MDF boards. Very heavy stuff yet I think for the size, could be the thicker the better.

Bought a Gunnersen 1200 x 2400 x 9mm Acoustic Pinboard, planned to use it to cover the base underneath the projector.

Bought 2 ultra low noise fans 200mm from Amazon.

The lining, I'm planning to use different options to see how's the outcome:

• Acoustic Foam Wedge Tiles
• Bath towels
• Maybe in combination with the acoustic pinboard or some other 10mm acoustic rubber foam

 

 

[tomwu]

@Rec. 709

After 5 months of planning (laziness), I finally completed the hush box. Well, need a bit of more decoration yet the result is fantastic!

 

Material used:

• Most boards are 25mm MDF bought from bunnings, a few pieces are 16mm ones (used up 25mm board and only very few Bunnings has 25mm in stock).
• Acoustic pin board: https://www.bunnings.com.au/forestone-1200-x-800mm-9mm-black-acoustic-pinboard_p0098212
• 2* 200mm fans for exhaust and 3*120mm fans for air intake.
• Real wool mat

 

Without hush box, from seating position, it's 53.5 db. Pretty loud, yet turn amp volume up, you can still enjoy a movie with great experience. I've watched movies, even some concerts like this for almost 5 months.

 

In the begining, The design is a rectangle box sized 120*90*45cm, huge! Then I decided to cut 4 corners to make it look less bulk.

 

 

Edited May 7, 2020 by tomwu

[tomwu]

 

 

I made a hold with 127mm diameter, just a few mil bigger than the lens. (Lens is removable)

 

Also I'm just using screws, so that it will be easy dismantle if required in the future.

 

[Quark]

Looks good. What sort of noise reduction have you achieved?

[tomwu]

@Quark 15db!

 

A lot of issues on the path of making this hush box...

 

After I took off the lens, I noticed there's some plate on the bottom side that can't go through the hole...

 

Then I cut the front board to half.

 

[tomwu]

In the evening, very exited to turn the projector on for a test, and found the boresight is out of alignment (four corners are not in focus at the same time)...

 

I must be when I install the front board, it had put some force to the lens. Since everything's very heavy, the board and the projector (>40kg), if sometime the weight is lean on the lens (if bottom board is too high), then the lens mount will be moved a little bit, then re-alignment is required...

 

 

[tomwu]

Once done, I very carefully adjusted height of the projector and make sure lens does not touch the front panel.

 

Also on top cover and back cover, I use wool panel and nailed acoustic pinboard covers it.

 

 

 

 

[Quark]

17 minutes ago, tomwu said:

@Quark 15db!

 

 

That's a massive improvement - well done!

 

[tomwu]

1 hour ago, Quark said:

That's a massive improvement - well done!

 

Thanks, it is great outcome, super satisfied!

 

 

However, after watched for 2 hours, I noticed an issue. The temperature inside the projector (in menu, it displays temperature in several points) is 10 degrees higher than earlier.

 

Checked again for the fan specs and I'm pretty sure they're over spec'ed. And the exhaust fan CFM combined is below 40% of what's installed in the projector itself.

[tomwu]

Later I noticed the temp in the hush box it's self is pretty high, thus hot air goes into the air intake and caused the projector temp high.

Then I made 2 new pieces of board to isolate intake and output areas. Which ends up very very effectively. Just 2 small pieces of board reduced temp for 15 degrees! Now it's even 5 degrees cooler than in the past without the hushbox!

 

[Clarity Calibration]

Most impressed by your DIY skills and of course the improvement! Waiting to see how it turns out with the rising temps... I imagine that Christie generates a fair bit of heat.

[tomwu]

1 hour ago, Rec. 709 said:

Most impressed by your DIY skills and of course the improvement! Waiting to see how it turns out with the rising temps... I imagine that Christie generates a fair bit of heat.

Christie does generate a lot of heat with 1000W Xenon bulb.

 

Yet now with intake/exhaust area separated,  it's 5 degrees cooler than not having the hush box. I've been using it like this for 2 weeks and it's just perfect

[oztheatre]

wow that is a beast of a projector!! well done on the box looks phenomenal.

 

 

[Marc]

Well done @tomwu - great mod!

[tomwu]

Thank you guys. It is really good. Better than I expected.

 

Thus I'm lazy to 'decorate' the box, I think until my boy can draw something nice/interesting on it.

[Johnny_Boy]

great work!