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#1
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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? |
#2
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Active EQ and mic placement
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#3
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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') |
#4
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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
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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') |
#6
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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. |
#7
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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
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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 |
#9
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Active EQ and mic placement
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#10
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Active EQ and mic placement
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. |
#12
Posted to rec.audio.high-end
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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 |
#13
Posted to rec.audio.high-end
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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 |
#14
Posted to rec.audio.high-end
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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 |
#15
Posted to rec.audio.high-end
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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 |
#16
Posted to rec.audio.high-end
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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 |