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post #1 of 32 Old 01-28-2015, 10:54 AM - Thread Starter
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Hush Box - Fan cfm and temp

I am building a Hush box for my benq w1070+ (attached file). I wonder:

1. How much cfm is needed? 30, 40, 50, 100 cfm?
2. Dose it mather if i buy a fan with 8dB or 17 dB considering that the projector has 28-31dB?
3. how much rpm is needed? dose it mather?
4. What temperatur in the box is ideal?

Everyone says that bigger fans are more silent so I think i will get two 140mm, maybe something like this http://www.inet.se/produkt/6308827/i...kt-140mm-svart

Here are some other fans http://www.quietpc.com/140mmfans

Last edited by spatzen; 01-28-2015 at 11:54 AM.
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post #2 of 32 Old 01-28-2015, 11:53 AM
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These are all just guesses on my part.

1. Enough to move all of the hot air coming out of the pj, and then some. It may be hard to figure how much that is though.
2.Hopefully, the hush box fans is all you'll be hearing after going through this trouble. So the quieter the better.
3.RPM and CFM usually go hand-in-hand. CFM being the more critical spec for this application.
4.Hopefully, you can make the pj feel like it is not even in a box, so achieving room temp in the box would be great. I'd worry if it's over 5-10degrees hotter inside that box, as that means that the pj will be using slighter hotter air for cooling. Or do you plan to install fresh air intake fans as well?

I think your other thread about the fan power supply had a link to a nice hush box project. Maybe that page talks about the finer technicalities for a good box.

bg
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post #3 of 32 Old 01-28-2015, 12:05 PM - Thread Starter
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Originally Posted by garciab View Post
These are all just guesses on my part.

1. Enough to move all of the hot air coming out of the pj, and then some. It may be hard to figure how much that is though.
2.Hopefully, the hush box fans is all you'll be hearing after going through this trouble. So the quieter the better.
3.RPM and CFM usually go hand-in-hand. CFM being the more critical spec for this application.
4.Hopefully, you can make the pj feel like it is not even in a box, so achieving room temp in the box would be great. I'd worry if it's over 5-10degrees hotter inside that box, as that means that the pj will be using slighter hotter air for cooling. Or do you plan to install fresh air intake fans as well?

I think your other thread about the fan power supply had a link to a nice hush box project. Maybe that page talks about the finer technicalities for a good box.
1. Does someone know approximately how much cfm is needed? Is 30 cfm to low or should I go with 60 cfm? Are two fans enough?
4. No i will not install fresh air intake.
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post #4 of 32 Old 01-28-2015, 12:06 PM
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I'd imagine you'd want to be somewhere in the 100-250 CFM range depending on what PJ you've got, and how efficient your box is at pushing that air in. Keep in mind that's ACTUAL airflow, which will be quite a bit below rated airflow at zero (or near zero) static pressure differential.

Yes you want quiet fans, the hush box is going to muffle the sound of the PJ.
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Originally Posted by RPS13 View Post
I'd imagine you'd want to be somewhere in the 100-250 CFM range depending on what PJ you've got, and how efficient your box is at pushing that air in. Keep in mind that's ACTUAL airflow, which will be quite a bit below rated airflow at zero (or near zero) static pressure differential.

Yes you want quiet fans, the hush box is going to muffle the sound of the PJ.
I have the Benq W1070+. Do you think i need closer to 100 or 250 cfm? Is it more important to get air into the box than out of the box? should i maybe have two fans inlet and one outlet? If i have two fans with 60 cfm, one as inlet and one as outlet dose that equal to 120 cfm?
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I can recommend 2x120mm since that worked for the box I built. My first exhaust only used 1x80mm and that was not enough (projector would shut down due to heat warning). It's probably better to have more capacity than needed since you can always slow the fans down and reduce noise.

-tm
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I can recommend 2x120mm since that worked for the box I built. My first exhaust only used 1x80mm and that was not enough (projector would shut down due to heat warning). It's probably better to have more capacity than needed since you can always slow the fans down and reduce noise.

-tm
Sounds logical but do you remember approximately how much cfm you have? What projector do you have?

Dose someone know if a 140mm fan leakes noticeable more sound from the projector than a 120mm fan. What i am trying to figure out is if the lower fan noise of a 140 mm maybe in total get louder because of sound leaked.
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Quote:
Originally Posted by spatzen View Post
Sounds logical but do you remember approximately how much cfm you have? What projector do you have?

Dose someone know if a 140mm fan leakes noticeable more sound from the projector than a 120mm fan. What i am trying to figure out is if the lower fan noise of a 140 mm maybe in total get louder because of sound leaked.
Sorry, I don't recall the CFM rating for those fans. I'm fairly skeptical about any numbers on fan packaging. Probably exaggerated marketing numbers. They're all going to be similar. CFM is going to be a product of rotation speed and blade size. No getting around the physics.

The projector in the box was an Optoma HD71.

Bigger hole probably means more sound leakage. My box exhausted into a different room, which is where the fans were located. That's the best way to do it, if you can. Doesn't matter how loud the fans are then.

-tm
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When I get my projector back from the repair guy, I'd like to follow in your footsteps.

Can you post the pics of your finished box? The box should be light enough to not overly weigh down the ceiling mount though. Mine isn't installed on studs so I'm worried it could come crashing down.

Another option instead of a hushbox, or on top of it, could be to record the projector's sound at ear level, then make a 180 degree out of phase short recording and put that on a loop in an audio program that outputs audio along your hdmi wire in stereo to the projector, which you could mute or change the volume of. I'm going to try this option first. I use an external Asus Xonar USB sound card for my sound so the HDMI sound device is free to accept a different signal. You could also do it by sacrificing one or two channels of your 7.1 HDMI connection to a receiver to send this signal to the projector's front left and right channels, since it's in stereo, and use the rear surrounds as your mains. Then you just need to remap those channels in media player classic and you're done.

Play back the recording on a loop using winamp. It probably won't work too well with SmartEco though, since that changes the fan speed (and therefore the noise profile) I believe. Who knows how well it would work even with white noise, which is notoriously hard (if not impossible) to cancel out. Still, it's worth a try.

I wonder if using an Atmos sound system could be of use for this : You record the sound of your projector right next to the projector, constantly, and feed that microphone data back into your mix, so that your entire sound system is now playing back the virtual inverse of that sound in your room, as if it were coming from your projector. (your Atmos mix would need to know where your projector is, and precise positioning of all your speakers)

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post #10 of 32 Old 01-29-2015, 09:52 AM - Thread Starter
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Sorry, I don't recall the CFM rating for those fans. I'm fairly skeptical about any numbers on fan packaging. Probably exaggerated marketing numbers. They're all going to be similar. CFM is going to be a product of rotation speed and blade size. No getting around the physics.

The projector in the box was an Optoma HD71.

Bigger hole probably means more sound leakage. My box exhausted into a different room, which is where the fans were located. That's the best way to do it, if you can. Doesn't matter how loud the fans are then.

-tm
You're maybe right about the marketing thing. I will go with some well know brand like "Be quiet" and change fan speed to lowest possible noise with acceptable temperature.

Unforthunly I cant have the exhaustion in another room.

I look up your projector and it has 200W compared to mine 350W (200W in Eco mode). I use eco mode or economical so It seems that 120 mm fans will be enough for me.
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post #11 of 32 Old 01-29-2015, 10:00 AM
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Originally Posted by RLBURNSIDE View Post
When I get my projector back from the repair guy, I'd like to follow in your footsteps.

Can you post the pics of your finished box? The box should be light enough to not overly weigh down the ceiling mount though. Mine isn't installed on studs so I'm worried it could come crashing down.

Another option instead of a hushbox, or on top of it, could be to record the projector's sound at ear level, then make a 180 degree out of phase short recording and put that on a loop in an audio program that outputs audio along your hdmi wire in stereo to the projector, which you could mute or change the volume of. I'm going to try this option first. I use an external Asus Xonar USB sound card for my sound so the HDMI sound device is free to accept a different signal. You could also do it by sacrificing one or two channels of your 7.1 HDMI connection to a receiver to send this signal to the projector's front left and right channels, since it's in stereo, and use the rear surrounds as your mains. Then you just need to remap those channels in media player classic and you're done.

Play back the recording on a loop using winamp. It probably won't work too well with SmartEco though, since that changes the fan speed (and therefore the noise profile) I believe. Who knows how well it would work even with white noise, which is notoriously hard (if not impossible) to cancel out. Still, it's worth a try.

I wonder if using an Atmos sound system could be of use for this : You record the sound of your projector right next to the projector, constantly, and feed that microphone data back into your mix, so that your entire sound system is now playing back the virtual inverse of that sound in your room, as if it were coming from your projector. (your Atmos mix would need to know where your projector is, and precise positioning of all your speakers)
People have been fiddling with this for years. There's a reason it only works well with headphones.

Good luck is all I can say.
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post #12 of 32 Old 01-29-2015, 10:23 AM - Thread Starter
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Originally Posted by RLBURNSIDE View Post
When I get my projector back from the repair guy, I'd like to follow in your footsteps.

Can you post the pics of your finished box? The box should be light enough to not overly weigh down the ceiling mount though. Mine isn't installed on studs so I'm worried it could come crashing down.

Another option instead of a hushbox, or on top of it, could be to record the projector's sound at ear level, then make a 180 degree out of phase short recording and put that on a loop in an audio program that outputs audio along your hdmi wire in stereo to the projector, which you could mute or change the volume of. I'm going to try this option first. I use an external Asus Xonar USB sound card for my sound so the HDMI sound device is free to accept a different signal. You could also do it by sacrificing one or two channels of your 7.1 HDMI connection to a receiver to send this signal to the projector's front left and right channels, since it's in stereo, and use the rear surrounds as your mains. Then you just need to remap those channels in media player classic and you're done.

Play back the recording on a loop using winamp. It probably won't work too well with SmartEco though, since that changes the fan speed (and therefore the noise profile) I believe. Who knows how well it would work even with white noise, which is notoriously hard (if not impossible) to cancel out. Still, it's worth a try.

I wonder if using an Atmos sound system could be of use for this : You record the sound of your projector right next to the projector, constantly, and feed that microphone data back into your mix, so that your entire sound system is now playing back the virtual inverse of that sound in your room, as if it were coming from your projector. (your Atmos mix would need to know where your projector is, and precise positioning of all your speakers)
Yes I can post some pictures if I remember. I am not sure when I will start building it, have much work to do right now. Also I have to order some stuff from ebay which takes some time.

My inspiration for the box came from a German forum which you can check out right now http://www.hifi-forum.de/viewthread-105-2491-2.html#96. Scroll down and you will se great pictures of the box from all angles. I will build the box witouth the last corner (Wall nr 1 on the first picture)

I use a headset 2.1 sound when I watch movies but I am going for a hush box.

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Originally Posted by spatzen View Post
Yes I can post some pictures if I remember. I am not sure when I will start building it, have much work to do right now. Also I have to order some stuff from ebay which takes some time.

My inspiration for the box came from a German forum which you can check out right now http://www.hifi-forum.de/viewthread-105-2491-2.html#96. Scroll down and you will se great pictures of the box from all angles. I will build the box witouth the last corner (Wall nr 1 on the first picture)

I use a headset 2.1 sound when I watch movies but I am going for a hush box.
Here is another hushbox, which was build by a german.http://www.hifi-forum.de/index.php?a...05&thread=2742
He also included the measurements in pdf and zip.
I like the V1 better than V 2.2 he built, since it isn't so big.
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Those are pretty cool, but way too big for me. I think I'm going to try and work out a bigger, quiet blower fan for the 240 lamp, using a different shell than the default one so that I can do other mods like replace the lens for a glass one, improve the zoom range and sharpness. I might base it on an old black Sony HPPC case I have lying around.
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Originally Posted by RPS13 View Post
I'd imagine you'd want to be somewhere in the 100-250 CFM range depending on what PJ you've got, and how efficient your box is at pushing that air in. Keep in mind that's ACTUAL airflow, which will be quite a bit below rated airflow at zero (or near zero) static pressure differential.

Yes you want quiet fans, the hush box is going to muffle the sound of the PJ.
100-250CFM is ridiculously high. Have you ever heard those computer fans in a server that sound like a leaf blower or a jet engine? Those are not even 200 CFM fans (most likely around 150 CFM).

I think you are probably fine with a high speed 120mm fan for intake and another for outtake. Something in the 50-80 CFM range. You can even try using a resistor to run the fans at less than 12V to slow them down if needed. I would recommend the Scythe Gentle Typhoon AP-15 fan, I believe it is around 60 CFM. The problem is this fan is discontinued, it can still be found on Amazon though. Full model number is D1225C12B5AP-15. This fan is desireable because it has a very good noise curve, no unusual motor noises or clipping that can be found on a lot of other fans, pretty much just the whoosh of the air moving.
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post #16 of 32 Old 01-29-2015, 01:54 PM - Thread Starter
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[QUOTE=Erasmus354;31293513]100-250CFM is ridiculously high. Have you ever heard those computer fans in a server that sound like a leaf blower or a jet engine? Those are not even 200 CFM fans (most likely around 150 CFM).

I think you are probably fine with a high speed 120mm fan for intake and another for outtake. Something in the 50-80 CFM range. You can even try using a resistor to run the fans at less than 12V to slow them down if needed. I would recommend the Scythe Gentle Typhoon AP-15 fan, I believe it is around 60 CFM. The problem is this fan is discontinued, it can still be found on Amazon though. Full model number is D1225C12B5AP-15. This fan is desireable because it has a very good noise curve, no unusual motor noises or clipping that can be found on a lot of other fans, pretty much just the whoosh of the air moving.[/Q

I think you are right! I found this one http://http://www.ebay.com/itm/Enerm...item416f11f474. It has a manual speed control and 37,57-71,25 CFM, 14,5 USD. The cheapest Scythe Gentle Typhoon AP-15 fan I found on ebay was 24 USD.
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Wouldn't it be easier to just replace the two existing internal fans with better quieter ones?
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Wouldn't it be easier to just replace the two existing internal fans with better quieter ones?
Do you know the thread for this?
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Do you know the thread for this?
http://www.hifi-forum.de/viewthread-94-12408-40.html
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post #20 of 32 Old 01-29-2015, 02:56 PM
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Just incorporate a fan speed control. problem solved

DIY dust box / hush box / ceiling light... http://imagizer.imageshack.us/v2/640...633/7qBblE.jpg
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Wouldn't it be easier to just replace the two existing internal fans with better quieter ones?
No, the loud fan is the fourth fan, which is a blower fan not a rotary one, it's in the middle underneath the circuit board and you can't see it in that picture.

Google the service manual and you will see it. I've taken the projector 100% apart and put it back together to clean it because it was overheating and had dust blobs, it's definitely the blower fan causing all that noise.

The only way to fit a quieter blower fan to cool the lamp down, is get a quieter and therefore bigger one. But then it won't fit. So, basically, choices are rather limited. I checked on alibaba for quiet blower fans but didn't find a suitable drop in replacement. There may be one, but IMO it's better to just build a small custom enclosure and replace the blower fan with a bigger unit that is rated for quiet operation.

Or, if you don't mind hacking the plastic, simply drill a big enough hole in the base of the projector to stick an air hose in and then you can have your cake and eat it too. Or just open up the lamp lid, tape an eraser head to hold the release button down, (so the projector thinks the lid is still closed. if the button isn't pressed, the power doesn't turn on). Then you can just stick a blower fan right there and do it. But then it gets tricky, because there is a heat sensor that monitors for overheating to turn the lamp off. This part you definitely want to keep. And the blower fan input port needs to be connected to the outboard blower fan, to modulate the fan speed otherwise the projector might also not turn on. Although this part I'm not sure of. In theory you could get an external blower to keep the lamp cool but then dust would have an easier time getting in. On the other hand, the side vents aren't dust proof which is IMO pretty dumb. First step should be to get some dust filters in there.

Yeah, screw the hush box. Fix the problem at its source : unplug the blower fan and plug in a bigger, quieter one and have it rigged up from the lid to blow cool air in. Probably the best plan, actually, is to take off the left plastic port, and run a hose in the the underbelly where the current blower fan lives, so that the air can flow into the lamp's input port. That way there is no permanent damage to the projector but it would be better to just make a small hole in either the left side or the back panel and run the hose in there. Maybe the back would be the best, like right above the power plug port.

Or, drill a hole in the base and stick the blower right there, and add a couple sleeves to route the air flow from the external blower right into the lamp enclosure.
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Just incorporate a fan speed control. problem solved
No, that won't help. At all. Those three fans on the side panels are very quiet already, they are basically case fans and do not contribute much noise. You could find better + quieter ones, but next to the jet engine that we call the blower fan, their noise is negligible in comparison. You can actually run the projector with the side fans unplugged. It's still super loud. Because Blower fan = Loud.
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post #23 of 32 Old 01-29-2015, 04:05 PM
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No, that won't help. At all. Those three fans on the side panels are very quiet already, they are basically case fans and do not contribute much noise. You could find better + quieter ones, but next to the jet engine that we call the blower fan, their noise is negligible in comparison. You can actually run the projector with the side fans unplugged. It's still super loud. Because Blower fan = Loud.
Is the blower loud internally or because it causes harmonic vibration of the projector housing ? Have you tried adding a couple layers of dynamat to the outside of the projector bottom ?

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post #24 of 32 Old 01-29-2015, 04:10 PM - Thread Starter
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No, the loud fan is the fourth fan, which is a blower fan not a rotary one, it's in the middle underneath the circuit board and you can't see it in that picture.

Google the service manual and you will see it. I've taken the projector 100% apart and put it back together to clean it because it was overheating and had dust blobs, it's definitely the blower fan causing all that noise.

The only way to fit a quieter blower fan to cool the lamp down, is get a quieter and therefore bigger one. But then it won't fit. So, basically, choices are rather limited. I checked on alibaba for quiet blower fans but didn't find a suitable drop in replacement. There may be one, but IMO it's better to just build a small custom enclosure and replace the blower fan with a bigger unit that is rated for quiet operation.

Or, if you don't mind hacking the plastic, simply drill a big enough hole in the base of the projector to stick an air hose in and then you can have your cake and eat it too. Or just open up the lamp lid, tape an eraser head to hold the release button down, (so the projector thinks the lid is still closed. if the button isn't pressed, the power doesn't turn on). Then you can just stick a blower fan right there and do it. But then it gets tricky, because there is a heat sensor that monitors for overheating to turn the lamp off. This part you definitely want to keep. And the blower fan input port needs to be connected to the outboard blower fan, to modulate the fan speed otherwise the projector might also not turn on. Although this part I'm not sure of. In theory you could get an external blower to keep the lamp cool but then dust would have an easier time getting in. On the other hand, the side vents aren't dust proof which is IMO pretty dumb. First step should be to get some dust filters in there.

Yeah, screw the hush box. Fix the problem at its source : unplug the blower fan and plug in a bigger, quieter one and have it rigged up from the lid to blow cool air in. Probably the best plan, actually, is to take off the left plastic port, and run a hose in the the underbelly where the current blower fan lives, so that the air can flow into the lamp's input port. That way there is no permanent damage to the projector but it would be better to just make a small hole in either the left side or the back panel and run the hose in there. Maybe the back would be the best, like right above the power plug port.

Or, drill a hole in the base and stick the blower right there, and add a couple sleeves to route the air flow from the external blower right into the lamp enclosure.
Sounds complicated and risky business.
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post #25 of 32 Old 01-29-2015, 04:26 PM
 
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Originally Posted by dreamer View Post
Is the blower loud internally or because it causes harmonic vibration of the projector housing ? Have you tried adding a couple layers of dynamat to the outside of the projector bottom ?
I doubt that would help much. Getting a bigger CFM blower fan would work though, if you could adjust the air flow with a dial you could probably get it to be pretty quiet. After living without my projector for a month due to it needing a new color wheel, I do not miss the noise and am in fact considering ordering a blower fan rated for quiet operation, as long as I can attach a hose to it and feed that in the side. That's the less risky proposal I think. I'd still have to take the whole damn thing apart again after it getting back from the service center, so remove the old noisy blower and jury rig in a new one. Then make sure it's keeping the lamp cool enough. Then attach the new blower to my ceiling mount somehow. Along with my a-lens. haha the "fun" never stops.
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post #26 of 32 Old 01-29-2015, 05:09 PM
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Originally Posted by RLBURNSIDE View Post
No, that won't help. At all. Those three fans on the side panels are very quiet already, they are basically case fans and do not contribute much noise. You could find better + quieter ones, but next to the jet engine that we call the blower fan, their noise is negligible in comparison. You can actually run the projector with the side fans unplugged. It's still super loud. Because Blower fan = Loud.
I believe he is talking about having his projector in the box /case if he adds
fans (this depends on how the box is built) if they move to much air or create noise that's when
a fan control will come in handy instead of swapping fans out.
I have these fans in my computer case http://www.newegg.ca/Product/Product...-055-_-Product turn the rpm down they move a lot of air and quiet once again it depends on how he designs his box

DIY dust box / hush box / ceiling light... http://imagizer.imageshack.us/v2/640...633/7qBblE.jpg
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post #27 of 32 Old 01-30-2015, 08:15 AM
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Originally Posted by DTI View Post
I believe he is talking about having his projector in the box /case if he adds
fans (this depends on how the box is built) if they move to much air or create noise that's when
a fan control will come in handy instead of swapping fans out.
I have these fans in my computer case http://www.newegg.ca/Product/Product...-055-_-Product turn the rpm down they move a lot of air and quiet once again it depends on how he designs his box
I think, he meant a fan control for the 3 inside fans of the projector.
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post #28 of 32 Old 01-30-2015, 10:38 AM
 
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Here's the service manual:

http://www.scribd.com/doc/208363905/...-Manual#scribd

I've been trying to find the CFM and voltage specs of the blower fan for a suitable replacement. I think one of those silent 120mm fans would do the trick, so long as there was a dial to change the speed instead of just a switch because as time wears on, the bulb gets dimmer, and so you could get away with less CFM and therefore quieter operation. But you'd still probably want the fan to be electrically compatible since the projector modulates the voltage itself at the source to control it based on the settings in the menu and the signal it's getting and the heat the lamp is producing.
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post #29 of 32 Old 02-26-2015, 11:46 AM
 
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Tomorrow I should get my Dynamat panels for insertion into my HTPC-based w1070 hushbox. The tricky part is mounting my anamorphic lens on it, I want it to slide out but prefer if it's motorized. For now a manual slide would be OK, but with the short throw ratio of the w1070, it's very limiting to get the light beam out without any vignetting.
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post #30 of 32 Old 04-21-2015, 08:02 AM
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What do you guys recommend as liner material to absorb noise around the hush box. Mine is essentially a built in shelf in the back of the room. All the sides of the box are closed except the front face where the projector sticks out. The top of the box has a return air vent that goes up the the air conditioning in the attic. The air filter in our house in the actual AC unit in the attic so I don't need to ever remove filters within the room since there aren't any.

ideas for materials:
felt
dynamat
auralex foam
owens corning fiberglass panels

What if you built a conduit for airflow into the box that had a winding pattern similar to how people build ports for subwoofers. This cavity, if lined with absorption material should also deaden sound from the projector right? I would guess this would increase the resistance to airflow a bit at the same time.

Blazar!
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