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Default Active EQ and mic placement

Regarding room equalization with a graphic equalizer, what consensus, if any
is there for placement of the microphone or SPL meter?

I had always thought that the best place was at ear level at the listeners
position, but is that best or should some averaging be done from multiple
locations.

I note the THX guidelines for using a home theatre equalizer says that EQ
for one position can result in poor performance at other points in the
listening area, but that calibration done with an SPL meter may be done from
a single reference position using the internal test signals from a home THX
controller. These are bandwidth limited signals they say minimize room mode
effects. Are we talking about pink noise signals or something else?

I'm not concerned with THX but rather using a 1/3 octave EQ to flatten out
the room response. I've done as much as I can with the room want the EQ to
smooth out the rest of the response from the speakers.

I've heard EQ'd room before using equalizers, pink noise test tones and an
SPL meter that sounded very good from both analog and digital devices,
although I believe the general preference is for digital.

I recall Dick Pierce commenting some time ago about what I recall was his
disdain for active EQ because there are never as many bands on the gear as
there are in the audible frequency spectrum, is that still your view Mr.
Pierce or am I misremembering?

Any constructive information gratefully requested.
Any other suggestions other than RANE's products?
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Steven Sullivan
 
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Default Active EQ and mic placement

wrote:
Regarding room equalization with a graphic equalizer, what consensus, if any
is there for placement of the microphone or SPL meter?


I had always thought that the best place was at ear level at the listeners
position, but is that best or should some averaging be done from multiple
locations.



Depends on whether it will be just one person listening
or several people. The new line of Pioneer receivers
allows both calibration modes (calibration for the sweet spot,
and calibration for several listening positions at once) and
lets you store and recall each, which seems the most sensible
given that sometimes you're listening alone, sometimes not.

I note the THX guidelines for using a home theatre equalizer says that EQ
for one position can result in poor performance at other points in the
listening area, but that calibration done with an SPL meter may be done from
a single reference position using the internal test signals from a home THX
controller. These are bandwidth limited signals they say minimize room mode
effects. Are we talking about pink noise signals or something else?


If they're minimizing room mode effects, they have minimal bass content,
because room modes are essentially a bass phenomenon. Moving up
through mid and treble frequencies, specular reflections become the main issue,
rather than modal resonance.



--
-S
"The most appealing intuitive argument for atheism is the mindblowing stupidity of religious
fundamentalists." -- Ginger Yellow
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---MIKE---
 
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Default Active EQ and mic placement

I am using a Rane 1/3 octave equalizer and a Rane spectrum analyzer. I
place the microphone at my ear level listening position and pointing
straight up. I find that after equalizing, the sound is much too
bright. It was suggested that I should set up a downward slope of .9 to
1.0 dB/octave starting at 2 khz (after eq adjustments). This would
result in a drop of about 3 dB at 16K. Also, Rane recommends using
mostly minus adjustments on the equalizer. I found these suggestions to
be very helpful. I also found that measuring bass response was not
useful at all. I have no idea why that is, but I use a considerable
boost at 40 and 50 and cuts at 80 and 100 to get smooth response. This
is using several sub woofers.


---MIKE---
In the White Mountains of New Hampshire
(44=B0 15' N - Elevation 1580')

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Default Active EQ and mic placement

Mike said:
I am using a Rane 1/3 octave equalizer and a Rane spectrum analyzer. I

place the microphone at my ear level listening position and pointing
straight up. I find that after equalizing, the sound is much too
bright. It was suggested that I should set up a downward slope of .9
to
1.0 dB/octave starting at 2 khz (after eq adjustments). This would
result in a drop of about 3 dB at 16K. Also, Rane recommends using
mostly minus adjustments on the equalizer. I found these suggestions
to
be very helpful. I also found that measuring bass response was not
useful at all. I have no idea why that is, but I use a considerable
boost at 40 and 50 and cuts at 80 and 100 to get smooth response. This

is using several sub woofers.
----------------------------------------------------------------------------------------------------------------------------------------------

Certainly cutting is better than boosting especially if the boost is
more than the driver can handle.
I once heard 8 dB suggested as the limit for boost on woofers,
fortunately in my room, the woofer seems to only need some cut at 50
Hz.

How many subwoofers are you using?
Are you speaking of multiple drivers or of actual subs in cabinets?
  #5   Report Post  
---MIKE---
 
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Default Active EQ and mic placement

NYOB asked:

How many subwoofers are you using?
Are you speaking of multiple drivers or
of actual subs in cabinets?


On the left side of the room I have a Definitive Technology 15" sub and
a Velodyne 12" sub (fed from the left channel. On the right side I have
two old AR3s (mid and high disconnected) plus a damaged Velodyne (woofer
is OK but the amp is toast) fed from the right channel through an Apt 1
amplifier. The room is 22' X 30' with an 18 foot cathedral ceiling.
All the subs are fed through networks that limit the bass to frequencies
below 100 hZ. My main speakers are DBX Soundfield Ones that have the
bass slider on the control unit set at minimum. The room tends to be
boomy in the low mid bass and corner placement of the subs makes this
worse so the subs are placed about mid way along the side walls.


---MIKE---
In the White Mountains of New Hampshire
(44=B0 15' N - Elevation 1580')



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Default Active EQ and mic placement

NYOB asked:



How many subwoofers are you using?
Are you speaking of multiple drivers or
of actual subs in cabinets?



On the left side of the room I have a Definitive Technology 15" sub and
a Velodyne 12" sub (fed from the left channel. On the right side I have
two old AR3s (mid and high disconnected) plus a damaged Velodyne (woofer
is OK but the amp is toast) fed from the right channel through an Apt 1
amplifier. The room is 22' X 30' with an 18 foot cathedral ceiling.
All the subs are fed through networks that limit the bass to frequencies
below 100 hZ. My main speakers are DBX Soundfield Ones that have the
bass slider on the control unit set at minimum. The room tends to be
boomy in the low mid bass and corner placement of the subs makes this
worse so the subs are placed about mid way along the side walls.


---MIKE---


According to Tom Nousaine's research having subs on opposite sides of
the room is a bad idea, and in all cases they should be in a corner.
Not doing so reduces the gain from having 2 drivers from the normal 6
dB to 4.5 dB.

Then there's the problem of notching caused by subs in different
locations, even if they are both in corners.

If at all possible you should move all subs into the same corner. I
don't recall anything about the AR3 other than I don't think it was
ever intended to be a subwoofer and I doubt it can provide anything
below the 30's in terms of low end response. Also, the 100 HZ xover is
I'm sure you've been advised to high to prevent any of them from being
localized. Tom's research confirms the THX standard of 80 HZ as the
highest point possible to keep the subs from being detected as separate
sources.

Of course at low frequency xover oints mono is better than trying to
get 'stereo' bass, particularly since there is no stereo at 80 Hz or
lower.

You should see if you can get your hands on the article from Stereo
Review January 1995 and read Tom's article "Subwoofer Secrets." His
investigation into best placement of subwoofers is very thurough and
definitive.

If you can't get a hold of it e-mail me and I can send a copy.
It may be available in the archives of Sound&Vision's web site.
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---MIKE---
 
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Default Active EQ and mic placement

NYOB wrote:

According to Tom Nousaine's research
having subs on opposite sides of the
room is a bad idea, and in all cases
they should be in a corner. Not doing
so reduces the gain from having 2
drivers from the normal 6 dB to 4.5 dB.


With all due respect to Tom Nousaine's research, every room is unique.
I placed one of my subs at my listening position and checked a number of
positions with a meter while playing a low bass frequency. The best
position was the sides. Putting the subs in the corners created a mid
bass boom that could not be equalized out. I realize that the AR3 won't
go as low as a powered sub but I am mainly interested in the low end of
a symphony orchestra which for all practical purposes is about 32 hz -
assuming the use of a five string bass. I have been "playing" with this
room for 15 years and the sub positions I am using offer the best bass
that I have been able to get.


---MIKE---
In the White Mountains of New Hampshire
(44=B0 15' N - Elevation 1580')

  #8   Report Post  
Kalman Rubinson
 
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Default Active EQ and mic placement

On 13 Nov 2005 18:07:11 GMT, "
wrote:

According to Tom Nousaine's research having subs on opposite sides of
the room is a bad idea, and in all cases they should be in a corner.
Not doing so reduces the gain from having 2 drivers from the normal 6
dB to 4.5 dB.


And, of course, this is exactly counter to the research published at
the Harmon website. Pick 'em.

Kal
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Posted to rec.audio.high-end
 
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Default Active EQ and mic placement

wrote in message
...
wrote in message
...
wrote:
Of course at low frequency xover oints mono is better than trying to
get 'stereo' bass, particularly since there is no stereo at 80 Hz or
lower.


This was very often true in the days when the LP was the primary
music carrier, as the mastering engineer would sum low frequencies
to avoid excessive vertical modulation. But since the introduction
of CD, it is possible to have stereo information recorded at low
frequencies, depending on the original miking. With classical
music, this can add "bloom" and an improved sense of the original
hall acoustic. With rock music, given the ubiquitous placement of
bass guitar and kick drum in the center of the mix, you are
probably correct.

John Atkinson
Editor, Stereophile


If you can't locate the source of the low frequency sound when it's
crossed
over low enough, it can't be stereo.

80 Hz or lower, with a steep enough xover and sound can not be localized.


The biggest problem with stereo bass is that there sometimes is, indeed, a
difference between the 2 channels. A pipe organ, for example, recorded with
a pair of spaced omni microphones, can show differences of 3db between the
right and left channels due to the side to side alternation of the lowest
pitched pipes. Although you can't tell which side the sound is coming from
when you listen, your system will have to supply more power on one side than
the other. You have to buy 2 equally powered subwoofers, since you don't
know which side is going to be called upon to supply the majority of the
output.

So there IS a stricly practical reason to sum the 2 subwoofer signals to
mono.

Norm Strong

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stealthaxe
 
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Default Active EQ and mic placement

wrote in :


If you can't locate the source of the low frequency sound when it's
crossed over low enough, it can't be stereo.


80 Hz or lower, with a steep enough xover and sound can not be
localized.


I will say this .. I have a stereo pair of subs and I crossover at 70 and
700 Hz (triamping, yes). Using 24 dB / oct L-R. It is still possible to
localize sounds coming from the subs, though through what mechanism I'm not
exactly sure. It could be that distortion harmonics actually play a role
here. Or it could be the leading edges of the waveforms. Low frequency
transients, heh.

--
stealthaxe
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Kalman Rubinson
 
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Default Active EQ and mic placement

On 17 Nov 2005 03:46:04 GMT, stealthaxe
wrote:

I will say this .. I have a stereo pair of subs and I crossover at 70 and
700 Hz (triamping, yes). Using 24 dB / oct L-R. It is still possible to
localize sounds coming from the subs, though through what mechanism I'm not
exactly sure. It could be that distortion harmonics actually play a role
here. Or it could be the leading edges of the waveforms. Low frequency
transients, heh.


Or, it could be unfortunate room acoustics......

Kal

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stealthaxe
 
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Default Active EQ and mic placement

Kalman Rubinson wrote in
:

On 17 Nov 2005 03:46:04 GMT, stealthaxe
wrote:



I will say this .. I have a stereo pair of subs and I crossover at 70
and 700 Hz (triamping, yes). Using 24 dB / oct L-R. It is still
possible to localize sounds coming from the subs, though through what
mechanism I'm not exactly sure.



...it could be unfortunate room acoustics......


I don't think so because when I select "MONO" output from the preamp,
things are much more centered.

--
stealthaxe


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stealthaxe
 
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Default Active EQ and mic placement

wrote in :

The biggest problem with stereo bass is that there sometimes is,
indeed, a difference between the 2 channels. A pipe organ, for
example, recorded with a pair of spaced omni microphones, can show
differences of 3db between the right and left channels due to the
side to side alternation of the lowest pitched pipes. Although you
can't tell which side the sound is coming from when you listen, your
system will have to supply more power on one side than the other. You
have to buy 2 equally powered subwoofers, since you don't know which
side is going to be called upon to supply the majority of the output.


1. who says you can't tell?

2. you need the power that you need. if you run out of power, upgrade
both amps. or one stereo amp. i'm one of these guys that thinks one
should never run out of power. to become preoccupied over the loss of, at
worst 3 dB is crazy.

--
stealthaxe
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