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Discussion Starter · #1 ·
I know it's supposed to be quiet to begin with, but the fan noise is driving me crazy, even after building a hushbox with a sealed rear air duct/vent (the G90 expelled air is sucked up into 20' 6" duct with a 500 CFM fan at the end). The hushbox did two things: (1) nuked the power supply hum/noise and (2) redirected the fan noise to the front of the unit.


Short of totally sealing the hushbox (which I can't do, since I don't have a cold air supply to feed into it), is there anything to be done? It seems that all the Rockwool or Theater-Shield+ in the world won't change the fact that air is rushing through the lens openings, and that the internal fan noise normally exiting the rear is being forced out of the front through the same lens openings. I'm at a loss--I feel like I wasted 5 days building this thing!
 

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Get an active noise reduction system to send out sound waves that are the exact opposite of the fan noise coming from the projector - voila! Silence.
 

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Quote:
Originally posted by amillians


Short of totally sealing the hushbox (which I can't do, since I don't have a cold air supply to feed into it),

is there anything to be done? It seems that all the Rockwool or Theater-Shield+ in the world won't change the fact that air is rushing through the lens openings, and that the internal fan noise normally exiting the rear is being forced out of the front through the same lens openings. I'm at a loss--I feel like I wasted 5 days building this thing!
I have a 1292 which is substantially louder although as an engineer that doesn't scare me yet.


My working design is a box which is sealed on the theater side, with an anti-reflection coated projection port glass from a movie theater supply shop on the lens end. The projector gets sealed to the box with foam partitioning the enclosure into inlet/exhaust areas. Air gets pumped in near the intake areas from ducting in the ceiling, and sucked from the exhausts the idea being that with positive and negative pressure respectively I won't get less than designed air-flow.


(The 1292 is ugly - it has five intake fans on back, two up front, and a pair of exhausts on top)
 

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...and don't forget the 3 CRT fans inside.... ;)
 

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Something's not right here. A G90 is very quiet even without a hush box -- not dead silent, but pretty darn quiet. Kind of like a soothing background of white noise.


Perhaps your G90 is out of spec.
 

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PF has hit this one right on the head. I also have a G90 and have had it for almost two years. Not once did it ever distract me or anyone else with its fan noise which you can't even hear unless the room is dead quiet, which rarely ever happens when there's content on the screen. Something is not right with the previous poster's setup or his ears are like Clark Kent's being superhumanly sensitive. The G90 is renowned for its whisper quiet fans and there's no way you need a hushbox. Even in the abstract if you did, there's no way you would hear noise emanating out of the hushbox either. I mean that would have to be loud and we all know its not made that way. I would suggest you get a tech to look at your setup.
 

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How noisy is it without the 500 CFM fan on?


500 CFM means a HUGE amount of air is being moved. The total amount of air being evacuated out of the G90 from it's built-in fans is probably nowhere near 500CFM. If the whole passage is indeed sealed from the front of the projector all the way 20' back to the 500 CFM fan, you could have a pretty sustancial 'wooshing' noise just from that much air trying to be moved past the internal fans which are actually slower.


Just for a few seconds, try turning off the 500CFM fan with the hushbox still in place? Does the unit get much quieter? If yes, there's your problem...


Kal
 

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Quote:
Originally posted by MikeM
PF has hit this one right on the head. I also have a G90 and have had it for almost two years. Not once did it ever distract me or anyone else with its fan noise which you can't even hear unless the room is dead quiet, which rarely ever happens when there's content on the screen. Something is not right with the previous poster's setup or his ears are like Clark Kent's being superhumanly sensitive. The G90 is renowned for its whisper quiet fans and there's no way you need a hushbox. Even in the abstract if you did, there's no way you would hear noise emanating out of the hushbox either. I mean that would have to be loud and we all know its not made that way. I would suggest you get a tech to look at your setup.
I tend to agree I have a G70 and also find no use for the hush box

If there is that amount of noise in the G90 I would think there is something internally wrong more than likely the fan has bearing noise need replacing

with the hush box this unit should be ultra quiet I have seen the 1292 with a hush box and it made a hell of a difference these are the loudest Pjs on the market
 

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So how low is quiet? I also have a G70, but I wouldn't say I've been thrilled with how quiet it is. Maybe we should do some db test and post the results. During the quieter movie scenes, I hear mine. No one else comments on it because I'm usually the only one sitting there critiquing every aspect of my theater and thinking "I should be able to do better." Ok, at 12 inches behind mine I register 61db (C weighting / fast response). Granted that isn't screaming, and people are normally farther than that, but it's a reference to compare your PJ to. Let's see what some of the others register. Hope it helps.
 

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Surprisingly the G90 is quieter than the G70 because of some new system Sony built especially for this PJ and after their noise problems with the 1292. Next time I fire mine up I'll give you a Db rating. Last time I did that, and I sit directly below mine, I seem to recall it was less than half that.
 

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Well, to be honest, and to my suprise, a foot from the back was the only place I could get it to register significantly on the meter. It's just "seems" loud to me.
 

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Discussion Starter · #12 ·
Thanks for all the replies, sorry for no follow-up, been out of town.


Yes, I *am* being way too sensitive on this--I'm aiming for perfection and although I knew I was going to fall short, I thought I was going to make it closer than I did. The G90 is a used unit (317 hours), but checked out in tip top shape by Roger Galvin just last week--I queried him on the noise issue (and the mild power supply hum) and he told me that it was no better/worse than any G90 he's ever heard. The exhaust fan doesn't appear to be helping/hurting the situation on the air rush--the exhaust duct is actually 25' with 2 "S" turns in it, so the "pull" isn't as great as one would think. Nothing really appears to be broken, except maybe my dreams of absolute silence! :)


For the record book, a lot of effort went into the "hushbox," but aside from wiping out any trace of a power supply hum, it really turned out to be an expensive (time/materials) strategy for redirecting the noise from the rear of the unit to the front. No harm, no foul--just food for thought for anyone foolish enough to think that they can 100% nuke sound without going the totally sealed box route. In fact, Roger just told me once again that I really should have put in a cold air feed for the projector--he apparently has had a number of G90 customers do it, so I'm not the only crazy person! :).


I'd give some meaningful numbers, but I only have a Rat Shack SPL meter and as noted, oftentimes the hard number doesn't come close to the soft number in my head. It just "seems" loud, but it's probably a combination of going overboard on sound isolation for the room and overly sensitive ears. As already stated, most any movie passage will drown out the fan noise in toto.
 
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