Built a vocal booth, need help designing an air exchange system!!!

[cajonezzz]

Hi ya'll.
As you may or may not know, our little place has been an ongoing construction project (as outlinedhere

We've just finished a nice largish vocal booth in the B room (actually big enough for 3, or an upright bass) We built it quickly and quite air tight, with the intention of adding some type of air system after the build out (it's no problem to mod the room, designing in the air xchange from the begining would have been great, but we we're moving fast on some down time)

We basically just need to keep fresh air in the booth, not Air co. The cool air in the B room should be fine to be recirculated in the booth, so...
We need to fabricate some kinda box that would reside out side the booth, with quiet fans to move air. I've got a couple ideas, but was wondering if someone has already done similar. Don't want to have to reinvent the wheel if we don't have too.
anyone have a suggestion on "super quiet fans" ? that would get us started.

thanks!

excuse the blurry shot: this is inside with window looking to big room.

[Jack Ruston]

Hi

In my humble experience

Quiet air circulation only ever occurs when you have a smooth large bore tube, with the fans some distance from the outlet. By large bore I mean BIG....not six inches or whatever. When you have a smaller diameter, particularly circular, you will get a lot of turbulence which manifests itself as the familiar train in a tunnel noise.

The only way fans are ever quiet (whatever they tell you) is when they run very slowly. This is partially due to mechanical noise, but equally due to the reduction in turbulence. Which means that if you want to shift any volume of air, you need a large fan and a big duct.

Clearly making a huge hole in the top of an isolation booth and sticking a fan in it will negate the isolation, So unless you have the ability to install a big duct above the booth leading to a 'remote' location, you are not going to end up with a workable level of noise.

I dont imagine this is going to be easy, and I'm afraid that what's likely to happen in this scenario is that you are forced to turn the air exchange off whenever you are tracking in the booth....which obviously rather negates the point of having that system installed in the first place.

I would first see how long the booth can practically be used for without needing to be opened up and 'cleared'. I would imagine it wont be long before a headache sets in. You could then try putting a couple of small ducts in, one top and one bottom perhaps, to pull air through. obviously you must have air in and out, but you dont neccessarily need an air in fan. I suppose that if you have a fan near the floor, pulling air out, and a simple baffled duct at the top for air to flow in, that would put the fan as far as possible from the mic. However, you'll still need to run it very slowly, and it will make some noise. What might be a clever idea, would be to wire the fan to operate at various speeds so that when you can tolerate more noise, you have the option of more circulation.

The more you baffle a duct, the harder it is for the air to flow 'successfully' into the booth.

J

[djui5]

Originally posted by Sly

What might be a clever idea, would be to wire the fan to operate at various speeds so that when you can tolerate more noise, you have the option of more circulation.
J

Yeah.......good idea...like putting a dimmer switch on the fan.


Cajo,

What about a slit arcoss the top of one side....with air flowing in..and a slit on the top of the other side pulling air out...this way there's no direct air traveling through the middle of the room where the mic's will be.

[thenoodle]

How about just take some close looks at the Whisperroom diagrams for their air duct/fan systems and then just come up with a similar thing for yours.

[Ruphus]

I have a passive system which works surprisingly well.
Originally tending to take an active solution, but had been granted that it would work without too.

The build consists of two channels. Not round tubes, but square ones for taking up less space, sized maybe 3 cm or so deep and 15 or so broad. The tubes sit inside between the inner surfaces of the walls and are prolonged with those flexible plastic foil tube stuff like used as steam exhausts on laundry dryers. These flexible ends again are attached to gratings with a foam filter in the wall. The effectiveness seems to be connected to the fact that one of the tubes has the outer grating sitting beneath knee hight with the inner grating around head hight, while the other tube has it the opposite way round. The passive exchange also works through air under- and over pressure generated by any surface moved inside the cabine. Obviously even with small moves already.

It really works great. You can easily spent over two hours in there without feeling out of oxygen or anything, - though after about an hour one usually wants to take a break anway.

Ruphus

[Dave Martin]

i'd think that you'd want air moving through the room... At a low level, of course. The two things that come to mind are that (A), a return is a necessity, and (B), tapping of the main AC duckts as far away from the room as poosible is a GOOD thing. I've got scads of ductwork in the attic here, including a couple of air mixers, where the air comes in from the outside units and then hit a largish chamber, where the ducts to the individual rooms are broken out.

I didn't design my system, by the way. The guys at Accurate Air (Nashville) did the design and the build.

[Jules]

How about using 'quiet" computer fans...somehow...? Dunno...

Whatever you build you may need to switch it on between takes, and off during them...

[Ruphus]

That might be the point.
If the system makes just the slightest noise you will be ending up with having to turn it off during tracking. At that point the system would become superfluous actually, I think, because instead of turning it on during breaks you could just open the doors. Works even faster than ventilation.

Either an active system is dead quiet or it won´t make practical sense for a recording booth I suppose.

Ruphus

[shortyprs]

I haven't tried it, but what about using the John Manville acoustic dampening duct liners? With enough length, a couple bends and a dual system (one for intake, one for outflow, small fan at the end of the outflow), you might get enough flow with nominal noise.

[Angelo M]

A pair of attractive, scantily clad women holding large hand fans made of peacock feathers always works for me.

Peacock feathers move a lot air but are virtually silent.

[zimv20]

maybe this isn't very slutty, but...

is it mandatory that the air be flowing during takes? i just run the fans/hvac stuff between takes and during breaks.

[Jules]

"is it mandatory that the air be flowing during takes?"

In the modern project studio / self built studio - NO!

In a "high end" facility - yes

IMHO

[triez]

Two things that will help: Make the duct and outlet port big, and DO NOT put any kind of grille, grate or slats over it. What usually works well is to make it a long box structure that is open across the front so nothing whooshes, and line the inside with felt. direct the air into the end of the box, and let the air diffuse out the wide slot cut along the front of it. The felt inside will dampen any noise.

[shortyprs]

Felt has its problems. If its synthetic, and most of it is, you have an issue with fumes and it can hold dust mites and mold. Very bad in A/C. That's why I'd look at the Manville stuff. Its tested and code-rated for HVAC.

Whether you run the fan or not while tracking depends on 2 things. Is the fan quiet enough not to matter? Does the room get stuffy without it. Big pipes with intake and return might allow enough passive flow to avoid being stuffy. But, fan or no fan, the system has to absorb sound along the path and not induce sound because of flow throgh the path. Length, width, building rated sound dampening material, quiet fans and open vents. Them there are the tickets.

[subspace]

Been routing ductwork a good bit of this week. Think I finally found the solution to keeping the drummer cool.

[cajonezzz]

Originally posted by subspace
Been routing ductwork a good bit of this week. Think I finally found the solution to keeping the drummer cool.

I like it when AE's look out for the drummer!

Sweaty bastards that they are.....

[faeflora]

Just stock up on dry ice and put it in the room when someone's in there for a while.

Also put in an O tank and a mask.

When they start to pass out from all the CO2 released, tell em to suck on the mask a little while.