From: "Richard Downs" <richardd@u...>
Date: Tue Feb 27, 2001 6:30 pm
Subject: RE: [acoustics] Re: HVAC
Thanks for the info. Sure I'd love to see the pics.The more information the
I don't know if we can get any access to outside air it's totally
underground and 10"1/2 poured concrete walls.
Maybe the entrance/lobby?
I also have concerns about the ceiling? Don't know exactly what we are going
to do there yet.
I know fresh air is important especially in the middle of a 10hr. block with
a bunch of musicians.
If I do a tracking session now I have to leave the AC/Fan running all the
From: sjoerd@n... [mailto:sjoerd@n...]
Sent: Tuesday, February 27, 2001 2:42 AM
Subject: [acoustics] Re: HVAC
--- In acoustics@y..., "Richard Downs" <richardd@u...> wrote:
"He said to take the 'returns' up to the ceiling in
> flex tubes - cut a vent in the ceiling and use the entire ceiling as a
> 'return'. Has anyone ever done this? And if so, what level of air
noise, if any, should I expect on this type of air flow system?
Totally agree with the other answer, iy seems your contractors
solution will jeopardise the acoustic integrity of the ceiling.
I have used a number of different methods, the most successful ones being:
- Build a long, narrow airway in the roof, almost the width of a room.
Put it in the right place and it will often give you additional
assistance with diffusion (which often means placing it about 2/3
towards the rear of the room). You can select a readily available
aluminum profile, or even better a "punched hole" type sheet.
Make it into a "soundproof" structure itself, so you don't have to
worry about it replacing insulation in the ceiling.
To minimise noise on your return(s) you can do a couple of things:
1. Do NOT let anyone sell you one of those "lifetime guaranteed -
never need to buy another one - good for alergies etc" kind of
filters. They are extremely noisy. Next one not to get are paper
filters - also noisy. Use the cheap blue-green nylon fiber ones, the
only good ones.
2. Use only quality insulated flex duct. We have found JPL Flex (from
Denver CO and Fresno CA) to be the most cost / quality effective ones.
Avoid using normal metal duct and insulating it - the end result will
be less effective compared to the flex duct no matter what insulation
3. I presume your intake will run to a collection point / fan chamber,
located in a seperate room / cupboard. Use extra flex duct, coil it
up and fill your extra space with it, you'll be amazed how much noise
4. The more returns you use, the less noise you'll have. If you can
run 2 flex ducts instead of one to the fan chamber, do it.
5. If you can't build return chamber(s) into your ceiling, you can use
a standard twin 10" collection grill - providing you use coiled flex
duct behind it. Cheap solution.
In our current (under construction) place we have a large aircon /
central heating unit, which looks after over 52000 cubic foot, located
in a small room right next to the tracking room. The returns consist
of 2 x 10" returns from the tracking room, 1 x 5" return from the
control room, and 1 x 5' return from outside. There is NO noise, you
cannot hear, only feel, if the unit is running or not.
A final tip - if at all possible, try and get at least a 5 to 10%
intake with fresh air from outside, you'll be amazed how many
headaches that eliminates!!
Hope this is usefull, I can email you some pictures of our
installation if you like
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