Subject: Re: [linux-audio-user] [OT] good studio monitors
From: R Parker (rtp405_AT_yahoo.com)
Date: Fri Jul 23 2004 - 20:30:30 /etc/localtime
--- Jamie Guinan <guinan_AT_bluebutton.com> wrote:
> On 22 Jul 2004, Fernando Pablo Lopez-Lezcano wrote:
> > I have four 824's at home and they are fine, very
> good the the price (a
> > little too much bass) <snip>
> Funny, I just got a pair of 824's a few weeks ago,
> and I found that the
> bass was really weak in my intended "sweet spot"
> position (speakers are
> a few feet apart on a shelf, against the wall, at
> ear level).
> Turns out I have some serious acoustic issues. The
> bass all but
> disappears around the point between the front and
> back walls (standing
> wave?), but I discovered that there's a lot of bass
> "hiding" in the
> corner, very loud and boomy there.
Your room probably needs some accoustical design work.
To build a standing bass wave a minimum amount of
square footage needs to exist, (I forget the amount).
Otherwise, you won't hear the bass and you will
artificially boost it in your mixes. Then when you
play it back in a car or wherever and the mixes will
be very bass heavy.
I think one other issue is wave cancelation but I'm
not so sure about this. Assume a 12 foot long room
with source against one wall. Cancelation will occur
where the waves meet which is at six feet. So, you
don't want to locate the mixing chair in the
DISCLAIMER: I haven't thought about accoustical design
for awhile so what follows is just a primer and
probably a bit inaccurate. It should be enough to give
you a sense of the challange. Everytime I design a
room, I have to relearn this stuff. :)
Ideally you meet the requirement for square footage.
Then you decide what the appropriate room
reverberation is. At this point, you're concerned with
total square footage and sabin values for existing
materials. Then begins the math for which we use
formulas in a spreedsheet that someone helped us put
The first thing you find is the current room
condition; equalization and reverberation responses.
Then you introduce X amount of square footage of
absorption to adjust the responses within about six
frequency bands beginning at 20Hz and going to about
So, for example, you target sabin values per band and
by introducing 80 square feet of four inch thick Ownes
Corning Accoustical Insulation (forget the product
number) you become acceptably close to the target
value. Of course that adjustment could negatively
affect one of the other frequency bands. Basically you
experiment with balancing the amounts of materials
and absorption to get the close as possible to the
target values. Perhaps the higher bands need to be
tamed so you introduce 80 square feet of four inch
ownens corning but you cover it with peg board so that
only the high band frequencies penetrate into the
absorption material. This module is likely to be on
The question is, how does buying anyone's prebuilt
bass traps figure into this. The traps obviously treat
frequencies but you've got to know what your room
requires. It's definitely not arbitrary. So, unless
someone selling traps knows the values of your room
and what you're going to use the room for they aren't
providing you with anything that you can't design
You can design a room through experimentation but that
takes time and you're always a bit unsure of what's
happening in the mixes. That's not a killer until you
do work for hire and someone comes back and says, "the
mix sounds like ass." Speaking from experience, that
If you don't want to do the math, I'd suggest calling
around until you find the Owens Corning product and
then build your own modules. Design them in four x
foor foot profiles and so they can be installed in
different rooms. That way you can take them with when
you move. Removable modules also enable you to change
the accoustics of a room; imagine, a dead room vocal
both becoming a live percussion room. A great feature
for limited spaces.
Somewhere in my empire of junk, I've got photographs
from the last studio that my partner and I designed
and built. They show construction strategies for sound
containment. There's room drawings and the accoustical
design spreedsheets. The variables are only for basic
cube shapes because we weren't dealing with angels and
diffusion. If anyone actually needs this stuff, I'll
put forth the effort to find it.
> I found this interesting/informative (disclaimer:
> the author sells bass
> Looks like I have some work to do...
> > -- Fernando
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