[Audio Empire]

On Wed, 9 May 2012 06:07:59 -0700, Gary Eickmeier wrote
(in article ):

"Andrew Haley" wrote in message
...

Well, hold on. Placing the speakers at exactly 1/4 of the room width
is going to maximally excite the second mode. Notching that out isn't
going to be so easy, especially if you want to be able to listen in
more than one position. Placing subwoofers in the corners is
efficient, but it also maximally excites *all* of the room modes.

I repeat to the OP: don't believe any simple solutions. I recommend
CARA http://www.cara.de which alows people to do some simulations.

Andrew.

I can only suggest to you that if the room is large enough for realistic
reproduction, and if the radiation pattern is not pure omni, or mostly
direct, but rather has a D/R ratio with negative directivity, then most of
these classical engineering "rules" go out the window. There will be no
serious comb filtering, no room mode problem, no notches or bad peaks. The
reason is that if the direct field is not as strong as most are used to,
then it will not add and subtract in equal proportions to the early
reflected sound. This is the sea change that permits us to position speakers
for imaging, not for frequency response.

The CARA series looks interesting, but I'm not so sure it isn't just another
look at frequency response only, like most of them out there. It is loaded
with pink noise signals and - horrors - sine waves! What the devil use are
sine waves in room acoustics studies?

In my old age curmudgeon phase, I am thinking more and more that the best
test records are well-recorded music and effects that have things happening
all around. Test signals are just a starting point, and you should adjust
levels and EQ by ear more than meters.

Gary Eickmeier



My current rig, which consists of a pair of Martin-Logan Vantages and a pair
of Aethena self-powered subwoofers in the corners was improved a hundredfold
by using my amp's built-in DSP-based computer EQ system. This works by
following the amp's VF display instructions on where to place an included
microphone for each test.

Not only did it EQ my speakers to be flat in frequency response at my
listening position, but it also, finally, got the crossover right between the
main speakers and the subs. I had been trying to do this by ear for the
better part of a year without much joy. After the EQ program had done its
stuff, I never again felt the need to touch the sub-woofer's controls! I'm
very happy with the sound of my system, frequency-response wise at this time.
I even find that the system images better than it did before it was EQ'd and
I put that down to the smoothing of the frequency response in the room.