Date: Sun Feb 11, 2001 9:18 pm
Subject: Re: [acoustics] can some one help me with a plan ,for a studio
In a message dated 2/11/01 12:27:49 PM Eastern Standard Time,
> Could I make another plastered brick wall with an air gap of 2"-3" for
> isolation from the adjoining shops?
Absolutely ... how noisy is it next door? Maybe build the front and back
walls first and see what you are dealing with, then plan the side walls to be
as massive as needed.
> Check out the diffusion sketchs at Dan's page and figure out what you can
> most easily build (polys are easy
> > but not super effective) ... you need lots of diffusion to artificially
> > increase the acoustic size of the tracking room, try to do this without
> > taking out all of the reverb time.
> When its coming to compromise, should I compromise on the control room or
> the tracking room?
There are two schools of thought ....
You need a big control room to conduct critical listening
You need a bigger studio tracking room to get acoustic instruments to sound
The sad truth is you need both.
Maybe you should have one big room (with a small closet to monitor tracking
levels). Track in the big room, then move the mixer and effects rack and mix
in the big room ... doesn't sound like you have that much gear ... with a a
couple of rack/equipment stands on casters and a clever wiring scheme and
you might get moving down to a 20 to 30 minute chore .... track from the
control closet till you have all of a project's tracks down .... then move to
the big room for mix down.
If nothing else you can always add and interior wall later if you find it
impossible to work that way.
> I can make the diffusers shown in Dan's site (the black one) . But I'll need
> dimensions for that. How deep are the various sections? Should they be from
> floor to ceiling or at an intermediate place?
There is a spreadsheet for calculating that type of diffuser on Dan's site...
you should set the size to fit the target LF - HF limits and commonly
available materials. Generally the taller the better, but well depth and
width set LF and HF limts which need to match the job at hand.
My $0.02 is skip anything this complicated ... go with something simple.
What is the funda of bass
> traps? Do they increase or decrease the Low frequencies? Will they also be
> required here? Do you suggest that both my rooms will require more of
> diffusers and less of absorbers? If I mount a diffuser panel, on the wall,
> does the wall have absorption material on it too. ie. Does the diffuser
> panel sit on top of the absorption treatment, or on top of plastered
A bass trap is generally a sealed vessel tuned to a frequency you want to
"trap" ... go to the library and look up "Helmholtz bottle". If you have a
single known problem freq., and can't tame it with diffusion then the bass
trap is an excellent tool. There is a plan for a Honeycomb port resonator
that looks pretty effective ... you can also make these out of peg board. If
you make a pegboard one for the wall you can also use the pegboared as
pegboard (hang your cables on them). If you curve the pegboard as you hang
it you have a polycylindrical helmholtz array cable hanger, or what I call a
PHACH ... and when people ask you: "What, the PHACH is that?", you can simply
Generally absorbtion (a bass trap or otherwise) is installed to reduce reverb
time ... zero reverb time is dead ... dead is bad. Take drums for example,
they sound good with a bit of reverb ... snappy and big .... but too much
reverb and they sound like mud. Its the Goldilocks syndrome ... not too hot,
and not too cold, but rather, just right. You can calculate a reasonable
target reverb time for a room, there is a spreadsheet on Dan's site.
In a 6,000 cubic foot room, for acoustic music you will want a RT60 (reverb
time till original sound drops 60 dB) of about 3/4 of a second ... for loud
rock-n-roll more like 1/2 of a second. Building movable absorbent panels
while allow you to adjust the reverb time.
Optimum reverb time is a function of source signal loudness, room Sabine
content (hoe reflective thje room's surfaces are, and room volume ... small
rooms have fewer resonant modes and long reverbs sound very colored (just a
few frequencies ringing). This is bad. You want all the frrequencies
ringing and then dying out more or less together ... this is good.
Diffusion artificially adds modes by spreading the direction of the
reflections ... the room seems less reflective by seeming larger
(acoustically). A highly reflective 3,000 cubic foot room with lots of
diffusion will sound like a much larger less reflective room.
Diffusion does not eliminate the need for absorbtive elements it just
diminishes the need ... you will likely need both. The polycylindrical does
both and they are easy to build ... you could line both side walls - near the
floor to near the ceiling - with vaious sizes (widths) and stuff their
interiors with absorbent. This would be an inexpensive but clever way to
make the room bigger acoustically for Mids and Highs while reducing Lows.
Get in there, cut some hits and use the money to get a bigger building.
Scott R. Foster