The Logic Off Topic list

Hi ot-ers,

I seem to recall that the use of a graphic eq to deal with room 
resonances, esp. standing waves, was found wanting in the late 1970's. 
If you mix to a room with peaks and troughs which are compensated for 
with eq, is the resultant mix what you want it to be - and in another 
room (with an 'ideal' flat response) would it sound the same? My friend 
says it will, using simple logic (not the programme!). I have a 
sneaking feeling it won't though I am weakening in this opinion.

While I have your full attention     ;-)     I have a peak in my room 
around 90Hz - and a trough centered on about 130. The room is 
unfortunately not far off a cube. L and W are 9 feet, and the ceiling 
slopes from 8 foot to 7 foot 6. The walls are 4" deep stud partition 
with 2 x sheets of plasterboard + skim, filled with rockwool. Suspended 
timber floor. I have floor to ceiling screens I use in the studio when 
tracking; when not they fill the wall opposite the speakers - JBLs 
4031s. The speakers are fairly close to the wall / corners - and have 
to stay there.

Questions : would two triangular rockwool filled traps behind the 
speakers help? They could only be about 3 foot high, and approx. 1ft 6" 
x 1 ft 6" on the two smaller sides.

Or - should I try a 4" deep bass trap, filled with rockwool, and 7 foot 
long, 2 foot wide, fronted with 3/8th ply, sealed all round, and fixed 
to the ceiling above and between the speakers? Other than this being 
elsewhere on the ceiling I can't fix traps eslewhere.


Regards,
Mike.


from Mike Levon
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[Non-text portions of this message have been removed]

On 4/10/04 3:07 AM, "logic-ot@yahoogroups.com" <logic-ot@yahoogroups.com>
wrote:

> Original Message:
>  Date: Fri, 9 Apr 2004 19:11:59 +0100
>  From: Mike Levon <mike@...>
> Subject: tuning rooms
> 
> Hi ot-ers,
> 
> I seem to recall that the use of a graphic eq to deal with room
> resonances, esp. standing waves, was found wanting in the late 1970's.
> If you mix to a room with peaks and troughs which are compensated for
> with eq, is the resultant mix what you want it to be - and in another
> room (with an 'ideal' flat response) would it sound the same? My friend
> says it will, using simple logic (not the programme!). I have a
> sneaking feeling it won't though I am weakening in this opinion.

Hi Mike,
EQing the monitor system with an RTA will only bring the system flat in a
specific zone (the "Sweet Spot") and you want that to be where your head is.
BUT, it will do nothing about nulls and standing waves.  Then, when you EQ
the rig to sound like "a typical stereo" system, those problems are going to
be virtually unbearable.
> 
> While I have your full attention     ;-)     I have a peak in my room
> around 90Hz - and a trough centered on about 130. The room is
> unfortunately not far off a cube. L and W are 9 feet, and the ceiling
> slopes from 8 foot to 7 foot 6. The walls are 4" deep stud partition
> with 2 x sheets of plasterboard + skim, filled with rockwool. Suspended
> timber floor. I have floor to ceiling screens I use in the studio when
> tracking; when not they fill the wall opposite the speakers - JBLs
> 4031s. The speakers are fairly close to the wall / corners - and have
> to stay there.

A symmetrical room is the worst thing you can have.  So, rather than placing
traps around, I think you should try to think of ways to break up the shape.
You could hang some pieces of carpet in strips about a foot high and several
feet long, staggered to form an uneven grid pattern on the ceiling, and you
could try to build a "fake" wall at one end to angle it some.  You could
build some baffles of 1"x4" and mount them along the side and back walls to
help disperse the sound waves.  The idea is to bounce the sound around to
infinity before it centers on one place (standing waves) and totally misses
another (nulls).  Traps might help somewhat, but they won't stop the
problems caused by the symmetry of the room...  Think of your speakers as
pool ball ejectors, and imagine where the balls would go given no gravity
and just bouncing around like Super-Balls until they lose all their energy.

Also, you might try moving the speakers so they aren't  meeting on axis at
exactly 90 degrees (since you say they're in the corners) and focus them so
the axes meet just behind your head, when sitting in the sweet spot.  Carpet
the floor if it isn't...  With a room that small and that shape, you
probably won't be able to rid yourself of every problem.  I started my
studio in a room about that size and quickly realized it simply wasn't going
to work and took over my entire basement (about 30'x60'), put a fake wall in
at about 55 degrees to one corner and facing an alcove at about 125 degrees,
so the sound never comes back on itself.  A lot of work, but worth it.  :\

Best regards,
...z


The trouble with idealism is that life gets in the way...

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