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The quest for a silent CRT

Discussion in 'Projectors, Screens & Video Processors' started by Nick Beecham, Mar 16, 2005.

  1. Nick Beecham

    Nick Beecham
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    The noise from a CRT projector can ruin the quite parts of a movie and so far I have not come across any practical way of dealing with this.

    Active noise cancellation only works with headphones.

    A hush box vented through the ceiling is a real hassle to construct and, from what I've read on these forums, it is very difficult to achieve substantial noise reduction while, at the same time, not causing the CRT to overheat.

    Forcing down the speed of the CRT fans causes overheating problems.

    So how about this idea then:

    The noise is only an issue during the quite parts of a movie. These are nearly always only a small proportion of the movie - in fact I've watched some movies where there was not a single scene quite enough for the noise to be an issue.

    So then, how about designing a circuit that would control the speed of the CRT fans based not on the CRT temperature but rather on the level of sound detected from the Home Theater loudspeakers. For most of the time, the fans would run at full speed. They would only be slowed down/stopped if the sound level from the loudspeakers fell below a certain level for a certain amount of time (both thresholds being user-adjustable).

    There would need to be an override switch so that the fans could run at full speed when the CRT is being calibrated.

    I have a friend who is an electrical engineer and I'm sure that he could construct something along these lines.

    Any thoughts on this?

    Cheers
    Nick
     
  2. Chris Frost

    Chris Frost
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    What happens if the projector is running when the volume is turned down?
     
  3. Thunder

    Thunder
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    I think the solution that CRT projectors came up with is the most practical solution. They worked out that all the fans in a Barco run in synchrony. This means that they produce a almost rhythmic hum. In order to reduce noise they just worked out a way to replace one of the fans with one which runs at a different speed and is therefore out of phase with the others. This then reduces the noise output substantially :) I dont think the noise from my 808s is that big a deal anyway. Its definitely less noisy than my old LCD :thumbsup:
     
  4. Erling

    Erling
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    Good point, or the equivalent would perhaps be a movie with a very quiet soundtrack.

    Based on this, I think you'd need to build in an automatic temperature regulator too - if the temp isn't low enough, the sound level based regulation would only be allowed to lower the fan speed to a more limited degree.

    Like someone in AVS forum pointed out, the constantly changing temperature inside might cause convergence drift and other stability issues.

    Another thing to consider is that a constantly varying fan speed might even be more noticeable than a constant drone you can tend to ignore.
    The PC I'm writing this on is equipped with an Abit IC7-G motherboard. It comes with some fan control software for the CPU and Northbridge fans. However, when the software is activated, it tends to vary the fan speeds up and down all the time, and this I really find much more annoying than a constant, non-changing noise spectrum.

    Just my 2C, but an interesting idea nonetheless.. ;)

    Cheers,
    Erling
     
  5. crteaman

    crteaman
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    Hi Mark, you are correct,however that modification is now old hat,as of a couple of weeks ago,new improved system is awesome possibly reducing 808 fan noise by 50%
    I have just been at "GODFATHERS" all weekend (including monday),his opinion was, "I think it is almost quiter than my 7lt!"
    Nick what unit do you use,Hockley eh? put an 808 in there recently.

    james
     
  6. Nick Beecham

    Nick Beecham
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    Many thanks for everyone's comments. I might just try this one and will post again to say how it all works out.

    James: It is a 1209 Data S installed by Gordon and Roland.

    Nick
     
  7. crteaman

    crteaman
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    Hi Nick, 1209 eh? good man,the 808 I installed at Hockley was on...wait for it..a 57" screen! I think the contrast was on 40, with the screen almost curling at the edges from the available light output :D

    james
     
  8. Thunder

    Thunder
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    Hi James, how does the new system work then mate? Or is it a case of "I could tell you but then I would have have to kill you" :D If you dont want to divulge on here then I will E-mail you :thumbsup:
     
  9. VFRMan

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    That goes for me too James. Can I get the mod, how much when? :lease: don't say it can only be done prior to installation :suicide:
     
  10. Baggy

    Baggy
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    Hi James,
    Can this be done to my 1209?
    Kevin
     
  11. Nick Beecham

    Nick Beecham
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    ...or mine? :lease:

    Nick
     
  12. Godfather

    Godfather
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    I think James is away on an install at the moment. AFAIK the new fan mod is only for the 808.
     
  13. jlcrawford

    jlcrawford
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    I am interested in the mod is it a user fit or pro fit and how many quids?
     
  14. Tim Cooper

    Tim Cooper
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    Yep & me....
     
  15. VFRMan

    VFRMan
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    ..come on James don't be shy :D
     
  16. crteaman

    crteaman
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    Sorry guy's but,as stated elsewhere I worked 107hrs and done 1250 miles last week,from saturdat to saturday,just got back in this evening and am readting for heading back to Godfather's to finish off his install/upgrade (he had to go off on hols).

    james
     
  17. Paul D

    Paul D
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    But there's 168 hours in the week, so what's the problem? :devil:
    :D :rotfl: :D


    :hiya:
     
  18. crteaman

    crteaman
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    Hi Paul,

    168 hrs,darn it my maths has failed me again,i better rush back to Godfathers cos I feel guilty now :eek:


    james
     
  19. surrey lad

    surrey lad
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    Can this mod be adapted to work on a cine7 in fact are there any mods for my pj. :smashin:
     
  20. Jonesthegas

    Jonesthegas
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    Will it work for a 1209s?

    Martin
     
  21. crteaman

    crteaman
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    Sorry guy's been flat out,well re-building the 9501 on and off this week,hope to pop it on the ceiling sometime on Sunday,thus the mini event at my place draws a little nearer.
    I will mail those Interested in the coming week to see if we can come up with a date that suits the majority,Sat or Sun? possible date is April 16th.

    Back to the questions, barco 7 series are very difficult to modify,although nothing's impossible,most others are not too bad.

    james
     
  22. crteaman

    crteaman
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    The Cine 9 (apart from very recent units) have a fan speed which is very quiet on power up, but when it reaches normal operating temperature the fans speeds up (a lot) for a bshort burst then drops again.
    It does this repeatedly and is in my opinion the 'only' negativething about a cine 9,(actually a second negative..the price)and to me its more distracting with a fan speeding up and slowing down.
    Barco's already have a temperature sensor mounted on an internal board which regulates the fans,as mark has said 808 are very quit really although they can be made to drop to cine 7lt levels perhaps a 40% reduction,1209's are even quieter than an 808,however the same holds for them they too can be made around 40% quieter.
    I am always a little concerned that anyone who finds a 1209 noisy, may not know how lucky they are,for eg, they measure around one third the DB level on a meter compared to a G70,still if we can have something a lot quieter its only normal we aim for it.
    I too have been very fussy about noise levels,much more so than for eg Henry, I think its part of the magic of the movies to transport us off into another dimension for true escapism.
    The last thing we want is for anything to break that magic for us, such as a neighbours dog barking or hundreds of led's lit up on our racks,fan noises and even bright white rooms.

    james
     
  23. Roland @ B4

    Roland @ B4
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    I played for ages trying to quiten down some of the big Barco's.
    Some mods worked really well, particularly on projectors on the bench or hung from my own ceiling. but when installed on site they either got too hot internally. Or the mod made not a lot of differnece.

    I found without doubt the biggest variable was the room and in particular the air temperature around the projector (hot air rising etc).

    On a 1209 it is worth removing the hard wired remote and its case that sits across the fans at the back this will cut the noise and allow more air out.

    A lot of the noise from an 808 is caused by how close the fans are to the rear grill. I have only ever seen one projector with this grill taken off and it was quiet but not pretty.

    The most effective solution I have ever seen for an 808 was to remove the fans altogther and attach a duct box to the back. This lead to a masive fan in the garage that sucked the air through the projector casing.
     
  24. Nick Beecham

    Nick Beecham
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    Roland

    Great to hear from you again.

    Would you be able to help me with the ducted solution to my 1209? :lease:

    Cheers
    Nick
     
  25. Tim Cooper

    Tim Cooper
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    Wahay hello Roland nice to hear from you m8ty.
    Nick:
    If the 1209's too noisy for you i could do you a favour & take it off your hands ;)
    Cheers.
    Tim.
     
  26. Godfather

    Godfather
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    Having lived with an 808s fitted with CRT Projector's mk2 fan mod for a week, I can tell you that it's really whisper quiet on powerup, but as it reaches normal running temperature (after about 15-20 minutes) the fans do speed up so that it becomes a bit noisier than the Cine 7LT. The noise is clearly audible during the quiet parts of a movie but is fairly easy to forget because it's a constant low pitched sound.
     
  27. Jonesthegas

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    Hi Roland,

    I would also be interested in knowing the feasability of a ducted solution to reduce noise on my 1209s.

    Mostly the noise is not too bad but, again, it is noticeable in the quieter scenes.

    Martin
     
  28. crteaman

    crteaman
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    The fan mod as godfather correctly states makes Barco's a lot quieter,I would estimate the noise reduction to be a 30%-40% reduction and with increased cooling! ;)

    james
     

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