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designing hush box for 801s

Discussion in 'Projectors, Screens & Video Processors' started by chrisgeary, Aug 8, 2003.

  1. chrisgeary

    chrisgeary
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    more accurately, designing a coffee table to look asthetically pleasing whilst keeping noise at bay :D

    ok, i have the tasty barco 801s which is floor mounted. its spiked to some wood (thus it has more clearance than usual beneath it) and a coffee table is above it. clearance at the top is 1mm at the moment (not what i intended but the spikes were an afterthought hence i lost all my clearance although since the PJ is angled up, the rear 3/4 of the PJ still has lots of clearance). our viewing position is just behind the PJ, hence the needs for some sort of enclosure.

    enclosure v1.0
    my first attempt was with side panels at 0" clearance at the top and 1.5" at the bottom. the rear panel is removable and covers fully top to bottom. i worked on the presumption that air would be taken in at the back and thus from the bottom of the enclosure from either side and warm air pumped out the front. what actually happened was heat built up quite quickly. i axed that design within 15 minutes. :eek:

    enclosure v1.1
    last night i tried side panels at 1.5" clearance top and bottom. a marked improvement in terms of heat build-up. there was virtually none but there was obviously enough to cause the fans to speed up (although im not sure how much the hot sticky evenings we've had these last few days have had to do with that).

    im thinking that v1.1 is probably ok, and if i raise the table up 1cm more to give the front of the PJ the clearance it needs, then it will work fine. basically i dont want to cook the PJ or have the fans work any more than at their lowest speed.

    does anyone have any practical experience in designing a hushbox for floor mounted barco CRT projectors? i know that air is sucked in at the back and exhausted at the front but is that the whole story? any tips would be greatly received :)



    thanks

    Chris :)

    [edit 10:36]
    Ive had an idea for v1.2:
    use 0" clearance at the top for the side panels as in v1.0. install three 240v fans (much like those already in the barco) running in series so that they run at 1/3 their normal speed at the top of the table to help stray heat run along the top of the (underside of the) table. those fans will be mounted to the table via a rubber strip to minimise noise transmission. think ill give that a go.

    im still interested to hear other's designs and experiences.

    Chris :smashin:
     
  2. chrisgeary

    chrisgeary
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    for anyone interested, v1.2 works reasonably well. here's what happened...

    started with the aforementioned Ikea Lack coffee table, £35

    modified the legs so that they were 50cm rather than the original 40cm. (bit of timber from B&Q, £5). applied a bit of clear satin varnish. £3.

    0" clearance at the top and 1.5" at the bottom of the side panels (MDF) works really well (obviously assumes fans are installed). (£8 for enough MDF to do the whole enclosure from B&Q)

    3 x 240v fans did not spin up at all in series. 2 x 240v fans do (just) and appear to run at about 1/4 to 1/3 normal speed. They shift a lot of air very quietly, but the machanics of them are noiser than i expected. when running in my hand they are whisper quiet, even silent, but motor noise really does transmit, even with rubber gromits in the way, through the table. (fans would have been £15 each from maplin although i had a few kicking about anyway)

    the fans are held to the underside of the table top with superglue and about 6 cable gromits (98p for a pack of 10 from B&Q).

    acoustic foam (£18 per sq. m from a friend) cut into small sections mounted at the rear where most noise and (crucially) free space without impeding air flow is.

    rear panel covered in acoustic foam and sits freely to allow access to the rear controls if required (by prodding it about until it allows me access) :D

    overall sound pressure from the 801s at idle is about 56db (at my viewing position)
    with enclosure that figure dropped off the scale completely (it was unmeasurable, id estimate the noise floor at least halved if not more.
    with enclosure and enclosure fans running, it came back up to 51db.

    for v1.3 what i think ill do is change out the 2 240v fans for 3 or maybe 4 12v ones. then use a variable resistor (or some other device) to control the speed until enough air is shifted without any extra noise being added to the system. the key thing is the mechanics or motors of the metal 240v fans are just too noisy and almost defeat the purpose of the enclosure. :rolleyes: i might also put a smidge of MDF up front to cover the gap between the floor and the start of the exhaust air flow.

    so far, project 'whisper' has cost me £70! respect :D

    has no-one else done anything like this? i'd love to hear about it :smashin:

    actually i would really take some advice from anyone who might be able to recommend the quietest of 12v fans and where to get them?

    cheers

    Chris
     
  3. SeaneyC

    SeaneyC
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    How big are your fans? If you're really flush, i'd try a couple of these bad boys and see what happens. Not sure if this is the best price online, i doubt it, but they usually deliver within 48 hours.

    Kustom PC fans
     
  4. Mark Ward

    Mark Ward
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    Got any piccy's to post Chris? This interests me, I've been trying to work out how to hang my 801S with a 18ft hogh ptiched roof.

    Floor seems way more sensible.

    Mark.
     
  5. Mark Ward

    Mark Ward
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    ME:-
    Spot the guy who's been on the lager all afternoon having got his PJ up 'n' running after a 2 week abscence.:clap: :D

    Which is where I'll be heading if I have any more!

    Mark.
     
  6. chrisgeary

    chrisgeary
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    ill get on the case.. (the piccies and the lager) :D

    you have it fixed now! thats fab news =)

    yeah ill post some images up in the next day or so. ive got some of those papst 80mm 12v fans on order. should be with me tomorrow.

    ah the amber nectar...
     
  7. SeaneyC

    SeaneyC
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    Legend has it that those Papst fans are the dogs bits for silent treatment. Will have to investigate for PSU mod. Let me know how you get on!
     
  8. chrisgeary

    chrisgeary
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  9. Mark Ward

    Mark Ward
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    Looks good Chris!

    I take it you'll be venting the rear panel once you have the fans in place? Also, can you power the external fans directly from the Barco.

    Would leave the top cover off the Barco aid cooling? or would that increase internal fan noise too much?

    Do those table come in Black BTW?

    Think I may have a look at this as a solution for me.

    Thanks for the piccys/inspiration.

    Mark.
     
  10. chrisgeary

    chrisgeary
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    nope. the rear panel will remain as is. you should be able to make out from the third shot DCF1089 that there is a gap at the bottom. this is about 1.5 inches. the theory i worked on was heat being trapped at the top. the 801s intakes from the back and exhausts from the front, but latent heat builds up because its gets a little warm. so the "ceiling" fans shift that forwards too. all that air is being drawn from back to front. thus, the gap at the bottom serves as the air intake leaving me free to fully seal the rear (which is where im most sensitive to noise). if i put my hand in the gap, i can feel a fair flow of air passing. plus, ive periodically opened the rear (ooer) and stuck my hand in (double ooer) to check all is well. and even in these warm summer evenings, its stayed the same as the ambient temperature.

    as for removing the cover, ive read posts from roland that suggest this to be a bad thing, in that the cover is part of the air flow design, which makes sense. roland, if you happen to read this, can the fans inside chloe be changed for nice quiet papst ones?

    id love to know if the PJ could power a relay to trigger the fans.. anyone know? might have to start a thread about that, or do a search :D

    according to my lovely gf, who pays more attention to these things, the table comes in the colour i have and a creamy white looking colour only. its so cheap though, you could afford to paint it :D
     
  11. Rob.Screene

    Rob.Screene
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    If you are using roughly 12V fans then the pyramid fan controller from quietpc.co.uk might be £20+VAT well spent. http://www.quietpc.com/uk/casefans.php#pyramid5

    It's a temperature sensitive and supposedly computer controlled. They work well and quietly in a couple of PC's I have them in, keeping the cases at 38-39 degrees C. The case fan apparently speeds-up if needed, but I never notice it, I just notice the both pc motherboards are not very temperature stable and the fans usually quiet.

    They also start up at full speed briefly and reportedly have an audiable warning if at full speed and the temerature is still too high.

    regards,
    Rob.
     
  12. BBD

    BBD
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    I'm in the process of developing a hushbox for a Sony G70 its ceiling mounted and vents into an open roof space so not directly comparable with your setup but it may be of use to others.

    I constructed the hush box using a 20mm timber frame clad with hardboard. The hushbox doesn't need any strength and in terms of fitting and removing the lighter the better. In hindsight I would use 3mm mdf instead of hardboard because it's easier to work with. The projector draws air in from the front and vents out of the back. The box is air tight to the room except for the inlet opening around the tubes. I have used loft insulation to line the box but I plan to use proper sound deadening material when funds permit. I'm using a Marley extractor fan (£25) to extract air from the rear of the box into the loft space. The extractor fan is the type which sits in the loft space with ducting either side. Its very quiet unlike normal ceiling/wall mounted extractor fans. The performance is very good as long as the flexible hose run is kept short. The fan also has a timer which allows the fan to continue extracting after the system has been switched off preventing heat soak build up. I have blocked off all space around the sides of the projector so that all air flow has to pass through the projector.

    Regarding fans I bought a 120mm fan from here a recommendation from the HTPC forum. I use it to blow cool air across my kit. Its very very quiet (silent) but the air flow is no where near as high as the Marley unit (see above). Also fan noise is very dependant on the loading the fan is working against. The fans in my Sony are relatively quiet out of the projector but are noisy when trying to push air through the confined space inside it. The trick is to dampen noise whilst still leaving large apertures for the air to flow through easily, not easy on a floor mounted unit. Unless you can vent it to under the floorboards!!
     
  13. chrisgeary

    chrisgeary
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    ok the papst 80mm fans arrived and are really noisy at any speed (in terms of motor noise not air noise). i have reverted back to my original plan. i really think 120mm is the minimum size for this kind of job. the larger fan blade surface area means they can run much slower to move the same amount of air. also the 240v ones are seriously quiet.
    what happened was i axed the wood support that the fans were screwed to (which i didnt mention before) and superglued 4 rubber gromits to each fan then superglued those to the table. that in itself reduced motor noise transmission significantly over my previous design. its now so quiet that im actually very happy that i spent money on the fans i now do not want because i inadvertently came across a better design through error :D
    i think ill still use the 80mm papst fans in my computer instead.
     
  14. Kristof Ector

    Kristof Ector
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    Nice design ... I have also a Barco 801s data.

    [​IMG]
    [​IMG]
    [​IMG]

    Does anyone know/have the construction plans of the barco-tables ?

    Kristof

    :smashin:
     
  15. Roland @ B4

    Roland @ B4
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    Sounds like someone needs to get into production on these.

    I still hold that Barco's and most other projectors won't like the case being removed as it forms part of the air flow.
    A Cine 7 will last about an hour before shutting down for instance.
     

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