801s Hush Box! Woohoo!

Discussion in 'Projectors, Screens & Video Processors' started by Boy Lex, Mar 23, 2006.

  1. Boy Lex

    Boy Lex
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    Ok. Here it is - after a couple of weeks of getting MDF cut to the wrong blinkin size!!!

    I got MDF cut at B&Q. Did the angles with the circular saw. Kitchen door type hinges on the bottom so I can still get inside.

    Brackets are attached to the base of the PJ - the rod goes through accross the top for the box.

    40 mm foam inside all around.

    Ducting to the loft with 2 120mm fans one blowing into back of box, one sucking out the front. Voltage testing after 2 hours shows fan voltage at 11.5V, so well under HOT conditions.

    Next mod is going to be a voltage readout and loft fan speed adjust. I should be able to lower the fan speed and make things even quieter and get to about 14v.

    Results at the moment: It is quiet!!! Not completely silent, but I can now hear myself think and I can watch stuff at low volumes and can completely forget about the slight hum from above... it really only appears when the soundtrack is complete silence
     

    Attached Files:

  2. cosaw

    cosaw
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    Very nice work! :thumbsup:

    Presume you've taken the rear remote out and are sucking through that hole?

    So is it a coat of paint next to get rid of that mdf smell?

    I was thinking myself what an ideal temp would be to run - presumably you could overcool so there would be a bit of a temp war going on inside and the pj electronics would not settle to a good working temperature?!

    Nice screenshot by the way - did you use any photoshop or similar to bring the brightness level up?
     
  3. Boy Lex

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    Yes to the remote, yes to the paint.

    As temperature determines the voltage that the fans run at, I reckon measuring this is the way to go... I know that prior to the installation of this ducting, it would run at about 15 or 16 volts, so now even in the box it is cooler than it was.

    Only thing I did to the screenshot was crop it, but my camera is automatic, so don't know what it does.

    All I can say is that my picture is excellent at the mo!!
     
  4. Alaric

    Alaric
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    Hi There,

    I'm just in the midst of building one myself....I cut the panels earlier today, however i have a CAD/CAM router at my disposal so cutting is the easy part.

    I'm also using a foam sandwich laminate board rather than MDF and have cut the shape to mimic my barcos shape, however i have more constraints on my design as you can already easily hit your head on the projector when getting into the rear seats and naturaly i don't want to encroach into the living space any more than i have to. I also don't have the good fortune to have a loft overhead as its a flat roof above. As such the best i can do is duct to another room or the outside, which may suffer condensation.

    What have you done round the lenses. I was thinking something like a rubber baffle ???

    Thanks,
    Lee
     
  5. Boy Lex

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    Around the lenses, I just stapled a bit too much foam into the box so it compresses around them. With the angle down, the box is only about 70mm lower than where the bottom of the PJ was... 40mm of foam, 20mm of space and 12mm of MDF.
     
  6. Mad Mr H

    Mad Mr H
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    Hi,

    Thats a very nice job, I like it loads......

    I would just like to add my small observations and hope you dont mind......

    I would use Plywood instead of MDF, MDF is great at transfer of sound which you want to avoid. MDF is easier to work with and cheaper, but WBP Ply is in my opinion better. (Marine ply even better but NO real acoustic differance)

    the fan mounting to the tube system......Fans on accoustic mounts to reduce noise transfer to the tube, which could create additonal "noise" - if not PM me you address I will donate 8 for the new fans and if I have enough some for the PJ too......

    The fan tube - if possible 2 45deg bends are better than one 90 - They could of course not be available.

    The fans tube going through the ceiling - Isolate the fan tube from the ceiling, if it touches the ceiling you will use the ceiling as a baffle board and create unwanted noise (maybe draught excluder strip or anyy rubberised material)

    Hush box to ceiling line, same again, acoustic isolation

    PLEASE NOTE - I only mention these things as my first impression of what I can see in the pictures.....

    It is a great job, and looks excellent....
     
  7. Boy Lex

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    observe away Andy! Always room for improvement!

    Internal fans already have mounts, but 2 for the loft fans would be appreciated - will pm. Thanks.

    As it is, the ceiling holds the ducting in place, which isn't ideal. I may cut the holes slightly bigger and hold the ducting up in the loft instead. I'm also thinking through a mount for the fans that doesn't physically attach them to the ducting so as to completely isolate any noise.
     
  8. Mad Mr H

    Mad Mr H
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    Try the rubber mounts I send you, they are so soft........:D
     
  9. cosaw

    cosaw
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    Down from the roof rasters...oh :rolleyes: ... I mean roof RAFTERS :blush: I suppose?

    Should be good!
     
  10. Mad Mr H

    Mad Mr H
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    couple of other thoughts....

    Dust issues?

    Which is the in/out of the fans? the higher one should be the out......cold air lower, hot air higher.......

    ALSO the long duct tube - this possibly will add to the "noise" in comparrison to a shorter tube - also long ducts cause more stress to the fans in the long run (no pun intended)

    Not got your PM yet.......
     
  11. paublo

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    hi Lex,

    Looking good, looks very similar to mine... :thumbsup:

    Just one suggestion - after much reading about my Barco 808 I discovered thta the majority of air, doesnt go through the board and fan at the top, but round the lenses and out the back. If your front duct is tight against the front fan you may not be getting cooler air through the projector - hence all the heat.

    I simply blast cool air vertically down the front of the projector and allow it to be sucked in through the fan and in past the lenses.

    I would also suggest a maplin temperature actuated fan controller - £5.99 kit plus two power supplies... works a treat..

    Good stuff.

    Paul.
     
  12. Boy Lex

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    Yeah I'd read that as well, but it looks like the 801x's work differently. No fans at the front at all, and the fans at the back blow inwards, so I've assumed the flow is back to front. I had thought about adding a front fan, but was worried about creating a no flow dead spot in the middle.
     
  13. Welwynnick

    Welwynnick
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    Is that why they make speakers out of MDF then?

    Nick ;)
     
  14. cosaw

    cosaw
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    Nick you probably meant that tongue in cheek with the wink!

    Just in case it wasn't in jest:

    If you've got the money to afford it and you're building your own you'd use plywood for your speakers also.

    I used 25mm mdf for my subs as the type of damping affoded by ply is not as critical in the real low frequencies it seems. Mdf is also easier to work with and cheaper. If I was building some full range speakers I'd think aobut going with ply once I get a bit more wood working expereience.
     
  15. Mad Mr H

    Mad Mr H
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    Sorry - Its been a long time since I bought cheap speakers ;)

    Marine Ply, real wood, fibre glass flares - but you knew that :D

    For others.....The idea it to hear the driver NOT the cabinet - so the cabinet should not vibrate or move or it alters the sound.....Cross bracing, not 90 deg corners etc all part of complex designs...MDF is weak, and if damp swells and twists - though most of us live indoors!

    OH - YES Nick - my subs are MDF - but then again I dont consider them that good - or musical - though they do give a very nice KICK :thumbsup:

    Many companies today do use MDF - cheap thats all, not strong, 40mm thick of you are lucky.....

    My "new" tannoy speakers weigh 80 KGs each! thats a 1209s weight.....:devil:

    Good job im ground floor..........
     
  16. Welwynnick

    Welwynnick
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    Absolutely.

    Martin Colloms did some well-known and very interesting research into the audible contribution made by cabinets. He removed the diaphram from a number of speakers and bonded weights to the voice coil. The intention was to nullify nearly all the sound from the drive unit itself, but preserve the unwanted cabinet vibration generated by the drive unit. The sound generated by the cabinet itself was compared with baseline measurements taken with complete drive units.

    What he found with most speakers was that the total sound output was not reduced as much as expected, showing that the cabinet generally makes a significant contribution to the overall sound. This contribution was highly frequency dependant, showing that the cabinets were tuned to certain frequencies, where they would sing along by themselves.

    This is quite bad, because whereas the drive unit will start and stop when told to by the amplifier, the cabinets resonances will continue for some time after the source has been removed. And it will do that at it's own preferred frequqncies - colouration indeed.

    Worse than that, the actual magnitude of the cabinet contribution with some examples was found, at certain midrange frequencies, to be greater than from the drive unit itself. Of course, this research couldn't investigate the contribution of cabinet vibration caused by acoustic coupling from the driver to the cabinet, nor from internal reflections of back-radiation and acoustic resonances inside the cabinet re-emerging through the drive unit itself, both of which will make the results even worse. Still, it's rather sobering, and one of the reasons I love my electrostatics.

    Hope I haven't gone too far off-thread!

    Nick
     
  17. Boy Lex

    Boy Lex
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    Indeed - it's been a while since I failed my acoustic engineering degree, but it's definately true to say that no speaker is capable of giving you a true reference sound - every different cabinet adds its own characteristics to the signal. Far better to choose a well made speaker that has characteristics that you are happy with than to go for the 'holy grail' of a speaker that has a perfect frequency response.
     
  18. JaniH

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    Here's the story of my hushbox (for BD801s) which is posted also on some other forums.

    First the air intake system. Cool air is drawn from the floor level through a closet behind the projector.

    Pic 1: The air duct going to the rear of the pj (old picture).
    Pic 2: Three NMB B30 fans at the other end of the duct.
    Pic 3: General view, notice the gap in the bottom of the closet door. This is where the air is sucked in.

    And now on the actual hushbox. Kal's hushbox project gave me a lot of ideas, so big thanks to him! Since I wanted to be able to operate the hushbox (take it down and put it back up) all by myself and there was no room for hinges at the back, I desided it would be easiest to install guide bars to the both sides of the pj into which the hushbox can be slided. Exhaust is directed toward the roof above the lenses. Sound absorbing material inside the box is some kind of compressed foam which is used in cars, boats etc. Works pretty well and isn't such a hassle to mess with as fiberglass boards but is somewhat heavy.

    A few teasers:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Rest of the pictures can be found here.

    Upcoming updates include:
    - modification to the air duct / back of the hushbox connection
    - sealing the lenses better (and make it all black!)
    - some noise dampening to the exhaust side, possibly an air canal going above the projector with additional fans
     
  19. Boy Lex

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    That looks really good. I decided to keep the chassis on because I heard that it channeled air flow - would be interesting to see temps on it on and off.

    What's the noise level like?
     
  20. JaniH

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    As you can see from this picture, I've covered the card cage with foam. This helped A LOT with cooling and lowered fan voltage, even with the original cover! Same thing is done on later Barcos (808's etc.) with metal covers. I recommend to try this.

    Pretty quiet, but I'm looking for silent. :) Difference to original is HUGE and to previous installation without the hushbox, but with the same air intake system, very noticeable. It's quite surprising how big a difference does it make when pulling colder air from floor level. :thumbsup:
     
  21. Boy Lex

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    Well it certainly looks like a good idea - my only concern is that the thermostat is located in just one place, so while voltages may go down, there could be hot spots elsewhere... Can't see how what you've done would do this though.

    Oh yeah - and I seriously think that these things must be easier to keep cool and quiet than any DLP or LCD unit... what do we think?
     

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