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post #31 of 70 Old 08-18-09, 11:39 AM
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Re: Is Full Range EQ a no go?

I am enjoying and learning from this good debate. Although, now I feel like I should go get a mic boom so I can "hang" the mic at the listening position with minimal interaction with the speaker response and compare the vertical to horizontal readings.
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post #32 of 70 Old 08-18-09, 11:33 PM
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Re: Is Full Range EQ a no go?

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Wayne A. Pflughaupt wrote: View Post

Yup - the key is to use the mic in accordance to the proper calibration file. Comparing weverb’s graph (generated with a mic calibrated for vertical orientation), to the graphs with sagging high end from those folks using vertical orientation with a horizontal calibration file, should be evidence enough.

I am not sure why anyone would be using vertical orientation with a horizontal calibration file. What am I missing?

When someone goes to download our cal file the information is clearly stated in red:

They are all on-axis (facing the sound source - horizontal position) response measurement files.
Cross-Spectrum employs the pressure method to calibrate the low frequency response and the quasi-anechoic free-field on-axis method to calibrate the upper frequency response.

For listening position measurements we recommend that the meter or mic be oriented vertically with a forward angle of about 10 - 20 degrees to capture a good mix of direct and reflected sound for 'room' measurements.


I am like brucek on this one...
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post #33 of 70 Old 08-18-09, 11:41 PM
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Re: Is Full Range EQ a no go?

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Wayne A. Pflughaupt wrote: View Post

You should point the mic towards the speaker you want to take a measurement of.
If you are going to measure one speaker at a time, which is not going to do anyone any good unless they have the brain of Audyssey to calculate the proper settings for all their speakers. In most cases, I would think people would do sweeps of their entire system. That is what I do when I measure full range. I certainly ain't gonna measure the left speaker then right speaker independently and try to equalize them independently. Once you measure them together after equalizing them independently, the response is going to be all over the place because of the interaction of the two speakers. The picture you provide contradicts your suggestion... it is pointed to the center. Of course that may be what you mean... point in the general direction of the ones you want to measure. I am speaking of measuring from the listening position, not nearfield.

EDIT: Those are also poor instructions in that picture too. When you are listening are your ears 3' clear of everything surrounding them. Those instructions are not real world and are not what you will actually hear. The mic needs to be very near where your ears will be. If there is reflection or absorption from a chair, then your measurement needs to take that into account and you need to equalize for it. This is one reason I have always been the proponent of placing the mic at my ear when measuring... but at least placing it where your ears will be... not out in the middle of the room where it will sound completely different than where you sit.
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post #34 of 70 Old 08-19-09, 05:49 PM
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Re: Is Full Range EQ a no go?

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I’m at a loss to understand how it makes sense. It’s a given that these mics are increasingly directional the higher the frequency range goes. Pointing it vertical without the benefit of vertical-orientation calibration (and 1-2 o’clock isn't far enough removed from straight-up to make a significant difference) – how can one expect to get anything but deficient high frequency information? It’s beyond mere “error,” it’s a wholesale deprivation of the high end that results in a graph bearing no resemblance to what you’re actually hearing (or at least what your speakers are delivering ) at the measurement location.
Yeah, you certainly make some good points Wayne. I'm somewhat on the fence, but I think this is the key point. What a single speaker delivers, and what is present at a listening position when two main speakers are playing is quite different. The listening position is the result of direct and reflected sound. That direct sound is affected by both the mixing and axis of two speakers, and the reflected sound is a result of the room. The reflections come from everywhere, including quite a bit from the rear. A horizontal mic positioning will basically ignore those signals. I do think we want to favour the direct sound and so the mic is tilted in that direction (albeit only slightly), such that we favour the direct, but don't ignore the reflected.

The direct sound will also be altered by the off-axis placement of each main. If the speakers are facing directly forward rather than toed-in (as many people like the increased soundstage it offers), there can be many degrees of off-axis to deal with, so even a horizontal mic placed between the two speakers is problematic.

I did some tests a while back on my mains and measured horizontal mic placement at 50" at 0 degrees on-axis compared against a horizontal mic placement using 30 degrees off-axis. Both tests were with the mic pointing directly at the speaker. The result is shown below, where even a small off-axis angle kills the high frequencies.

.

I show this to reinforce the statement that the only way to see "what your speakers are delivering" is to do a near field measure with the mic horizontal and on axis at zero degrees. Anything else is not going to be accurate.

I suppose there's merit in recommending a vertical mic position with a vertical calibration file, but my feeling is that should be left for those that want to get their own mics calibrated with two files, one for vertical and one for horizontal. We all agree that the generic file isn't accurate regardless of the mics orientation, so to supply two different files for mic orientation in a generic form seems a bit silly to me. I think we make it clear that for proper HF readings of a speaker users should measure a speaker near field.

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post #35 of 70 Old 08-19-09, 08:16 PM
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Re: Is Full Range EQ a no go?


Quote:
Sonnie wrote: View Post
I am not sure why anyone would be using vertical orientation with a horizontal calibration file. What am I missing?
When someone goes to download our cal file the information is clearly stated in red:

They are all on-axis (facing the sound source - horizontal position) response measurement files.
Cross-Spectrum employs the pressure method to calibrate the low frequency response and the quasi-anechoic free-field on-axis method to calibrate the upper frequency response.

For listening position measurements we recommend that the meter or mic be oriented vertically with a forward angle of about 10 - 20 degrees to capture a good mix of direct and reflected sound for 'room' measurements.
Basically, for the purposes of measuring frequency response, acoustical spaces fall into two categories: diffuse field or free field.

Free field essentially means an open space, free of reflections. According to the protocol recommended by most manufacturers of measurement mics, free-field measurements should be performed with the mic pointed directly at the sound source, and angled 20-degrees upward.

A diffuse field (aka random incident) environment is one where the sound is arriving from all directions more or less simultaneously, with equal probability and level. In other words, an exceedingly reverberant environment. Diffuse field measurements are typically accomplished with the mic angled at approximately 70-80 degrees, oriented towards the sound source.

Actually, very few venues are so reverberant that they would qualify as textbook diffuse field, even if they have bad acoustics. So the question is, is the typical home theater more akin to a free field or diffuse field environment? They typically have reflections, but aren’t exactly a highly-reverberant environment (unless perhaps someone is living in a cinderblock house). I’d characterize them as being closer to a free field environment than diffuse field – much closer. Therefore the best way to measure a home theater is to use the free field protocol when taking full range measurements. Subwoofers are different, of course. Bass frequencies could be classified as diffuse field, since they meet the requirement of "arriving from all directions, with equal probability and level."


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Sonnie wrote: View Post
If you are going to measure one speaker at a time, which is not going to do anyone any good unless they have the brain of Audyssey to calculate the proper settings for all their speakers. In most cases, I would think people would do sweeps of their entire system. That is what I do when I measure full range.
The only reason to measure any speaker independently would be if you intend to equalize it specifically, or if you just want to see what its response is. Not sure how you do a sweep of the entire system, since REW can only be plugged into the two front speakers? I wouldn’t do that anyway, because all the soundwaves bouncing around from so many speakers (including the room reflections) isn’t going to give a meaningful reading. It would only be a “just for grins” thing – you certainly wouldn’t want to make any system adjustments based on an “all speakers running” reading (except perhaps a sub level adjustment). Generally, RTA should be done one speaker at a time, or perhaps a speaker w/ subs.


Quote:
I certainly ain't gonna measure the left speaker then right speaker independently and try to equalize them independently. Once you measure them together after equalizing them independently, the response is going to be all over the place because of the interaction of the two speakers.
That may happen with multiple subs, but it’s not the case with mains at all. There is a proper procedure for measuring and equalizing speakers independently, but that's a thread for another day.


Quote:
The picture you provide contradicts your suggestion... [the mic] is pointed to the center.
Hmmm… Looks to me like it's off-center, pointed at the left speaker...


Quote:
EDIT: Those are also poor instructions in that picture too. When you are listening are your ears 3' clear of everything surrounding them. Those instructions are not real world and are not what you will actually hear. The mic needs to be very near where your ears will be.
It’s generally accepted that mics don’t “hear” the same way we do. Reflections from near-by objects that our ears can readily ignore can have a negative effect on what the mic sends to the RTA, which can skew the reading to show something that you really aren’t hearing. It isn’t necessary to get the mic precisely where your ears are. No one expects in-room measurements to deliver laboratory-grade results. A few feet in front of where your head would be would deliver a perfectly acceptable (and useful) reading.

Regards,
Wayne



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post #36 of 70 Old 08-19-09, 10:29 PM
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Re: Is Full Range EQ a no go?

Quote:
Wayne A. Pflughaupt wrote: View Post
The only reason to measure any speaker independently would be if you intend to equalize it specifically, or if you just want to see what its response is.
Right... which not many of us are doing when we try to equalize our rooms.

Quote:
Wayne A. Pflughaupt wrote: View Post
Not sure how you do a sweep of the entire system, since REW can only be plugged into the two front speakers?
What do you mean it can only be plugged into the two front speakers??? Yeah... definitely scratching my head on that one. I plug REW into the front inputs of my receiver and run the sweep through all of my speakers for my measurements. I want to know what my ears are hearing and they hear all of the speakers, not one at a time or just the two front ones.


Quote:
Wayne A. Pflughaupt wrote: View Post
I wouldn’t do that anyway, because all the soundwaves bouncing around from so many speakers (including the room reflections) isn’t going to give a meaningful reading. It would only be a “just for grins” thing – you certainly wouldn’t want to make any system adjustments based on an “all speakers running” reading (except perhaps a sub level adjustment). Generally, RTA should be done one speaker at a time, or perhaps a speaker w/ subs.
As noted above, I want to know what my ears are hearing and they do not hear just one speaker at a time... they hear all of them together. I am not sure why equalizing a 30Hz tone would be any different than equalizing a 3KHz tone... the ultimate goal is to get it flat. If we do not take into consideration how those reflections will effect it, then it definitely is not going to be accurate.


Quote:
Wayne A. Pflughaupt wrote: View Post
That may happen with multiple subs, but it’s not the case with mains at all.
I think you would be surprised if you tried it sometime. If I measure just one speaker at a time, it may not show that peak at 2KHz that is there with all speakers measured together. Again... I do not have the brain of Audyssey to know how those speakers are going to interact... and that actually may be why Audyssey doesn't always get it right either. It usually gets the subs right because it is measuring and equalizing them all at one time, but struggles with the mid and upper end because it is measuring them one at a time.

I can go out in my room right now and measure a full band sweep of all speakers and manually fix a peak that Audyssey missed, provided I am willing to give up all else that Audyssey did. I highly doubt anyone else can do that by measuring one speaker at a time.
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post #37 of 70 Old 08-20-09, 08:41 PM
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Re: Is Full Range EQ a no go?

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Orange55 wrote: View Post
But am I doing something which should be avoided?
Don't use any smoothing, and you should be time-gating your impulse so that you don't EQ frequency aberrations caused by reflections. Since we hear in the time-domain, we don't hear the tonal shift that you might measure if you don't gate the impulse....instead, we hear it as a separate reflection. Adding EQ will then screw up the tonal balance of the direct sound that we perceive as separate from the reflection.

The only catch to this is that you lose frequency resolution the shorter you gate....REW will tell you what the resolution is and doesn't draw the line below that frequency since it wouldn't make any sense.

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post #38 of 70 Old 08-20-09, 08:52 PM
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Re: Is Full Range EQ a no go?

Quote:
Quote:
---Quote (Originally by Wayne A. Pflughaupt)---
Not sure how you do a sweep of the entire system, since REW can only be plugged into the two front speakers?
What do you mean it can only be plugged into the two front speakers??? Yeah... definitely scratching my head on that one. I plug REW into the front inputs of my receiver and run the sweep through all of my speakers for my measurements.
Hey, I was merely quoting a highly reliable source! You must have one of those nifty 5-channel stereo modes or something like that. My ancient gear doesn’t have such luxuries.


Quote:
Quote:
---Quote (Originally by Wayne A. Pflughaupt)---
I wouldn't do that anyway, because all the soundwaves bouncing around from so many speakers (including the room reflections) isn't going to give a meaningful reading. It would only be a "just for grins" thing - you certainly wouldn't want to make any system adjustments based on an "all speakers running" reading (except perhaps a sub level adjustment). Generally, RTA should be done one speaker at a time, or perhaps a speaker w/ subs.
As noted above, I want to know what my ears are hearing and they do not hear just one speaker at a time... they hear all of them together. I am not sure why equalizing a 30Hz tone would be any different than equalizing a 3KHz tone... the ultimate goal is to get it flat. If we do not take into consideration how those reflections will effect it, then it definitely is not going to be accurate.
Sure, it’ll get you a nice “FYI” graph that tells you what your ears are hearing with the full system going. But there’s no way you’d ever get anything resembling accuracy trying to manually equalize this way. For instance, if the graph shows a problem at a certain frequency, how will you determine which speaker(s) it is coming from if all are playing at the same time? Especially if you have an asymmetrical room like mine, with some speakers closer to boundaries than others.


Quote:
Quote:
---Quote (Originally by Wayne A. Pflughaupt)---
That may happen with multiple subs, but it's not the case with mains at all.
I think you would be surprised if you tried it sometime.
I have. It works fine - been doing it well over 10 years now. (As long as we’re talking about bass-managed speakers, of course.) Each of my speakers is independently equalized, the front three with parametric, the back two a bit less-precisely with my receiver’s on-board quasi-parametric EQ. My ears and RTA confirm that response is not trashed when they are all operating together.


Quote:
If I measure just one speaker at a time, it may not show that peak at 2KHz that is there with all speakers measured together.
Trust me, something like that would never “just happen.” Independent measuring would identify the speaker(s) with the offending problem.

Regards,
Wayne



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post #39 of 70 Old 08-20-09, 08:58 PM
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Re: Is Full Range EQ a no go?

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brucek wrote: View Post
What a single speaker delivers, and what is present at a listening position when two main speakers are playing is quite different. The listening position is the result of direct and reflected sound. That direct sound is affected by both the mixing and axis of two speakers, and the reflected sound is a result of the room. The reflections come from everywhere, including quite a bit from the rear. A horizontal mic positioning will basically ignore those signals.
The mic will only ignore the upper frequencies – it’s omnidirectional. You’ll still get plenty of side and rear reflection information.

Furthermore, I’d submit that side- and (especially) rear-reflections, are high-frequency deficient to begin with, due to dispersion and absorption from the various surfaces (unless you have glass walls or something like that!). This is why someone can bring you into your room blindfolded, spin you around, and you can easily point to where the sound is originating from. So IMO you’re losing little in the way of meaningful reflections measuring with horizontal mic orientation.

But as Dr. Who noted in this post you should orient the mic so that it captures the information you’re looking for. If you want to ensure you’re getting all the reflections, then by all means position the mic vertically. Just keep in mind that it might affect the accuracy of your high-frequency measurements.


Quote:
The direct sound will also be altered by the off-axis placement of each main. If the speakers are facing directly forward rather than toed-in (as many people like the increased soundstage it offers), there can be many degrees of off-axis to deal with, so even a horizontal mic placed between the two speakers is problematic.

I did some tests a while back on my mains and measured horizontal mic placement at 50" at 0 degrees on-axis compared against a horizontal mic placement using 30 degrees off-axis. Both tests were with the mic pointing directly at the speaker. The result is shown below, where even a small off-axis angle kills the high frequencies.


I show this to reinforce the statement that the only way to see "what your speakers are delivering" is to do a near field measure with the mic horizontal and on axis at zero degrees. Anything else is not going to be accurate.
I can’t quite agree with your assessment. If orienting the speaker off axis delivers an inaccurate picture of the speaker’s response, then how can orienting a measurement mic severely off axis do anything but the same thing? Sure, “the direct sound will be altered by off-axis placement” of the mains. And a measurement mic.

In reality both graphs are accurate. Both show the high freq content that is reaching the listening position (assuming that’s where the measurement was taken?) with two different speaker orientations. Determining optimal speaker placement and positioning – isn’t that one of the reasons we take these measurements to begin with? I would assume that you can probably hear the difference between the two speaker placements, and I'll bet the way it sounds closely resembles what you measured. (Side note: If someone likes the off-axis imaging, but not the high frequency loss, the graph would show how to EQ to make up for it.)

I think your experiment actually helps prove my point, because consider this: If you had taken those two readings with the mic in a vertical position, most likely they would have looked the same. The reason? Even with vertical orientation of the mic using the proper vertical-incident correction file, the file makes up for the loss of high frequency information, but the file can’t reclaim the benefit of the mic’s high-frequency directivity.

IOW, I expect that vertical orientation would not readily register a change in frequency response when you toe the speakers away from or towards the listening position.


Quote:
I show this to reinforce the statement that the only way to see "what your speakers are delivering" is to do a near field measure with the mic horizontal and on axis at zero degrees. Anything else is not going to be accurate.
A near-field measurement does not represent what is heard at the listening position (assuming the listening position is not near-field), and I expect it would be problematic to find a professional who would agree with or practice near-field when tuning a system.

If I may be so bold as to make a recommendation to you and Sonnie - why not do what I do when I’m trying to decide what the correct approach is: consult a pro!

Regards,
Wayne



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post #40 of 70 Old 08-20-09, 09:30 PM
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Re: Is Full Range EQ a no go?

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Sure, it’ll get you a nice “FYI” graph that tells you what your ears are hearing with the full system going. But there’s no way you’d ever get anything resembling accuracy trying to manually equalize this way. For instance, if the graph shows a problem at a certain frequency, how will you determine which speaker(s) it is coming from if all are playing at the same time? Especially if you have an asymmetrical room like mine, with some speakers closer to boundaries than others.


I have. It works fine - been doing it well over 10 years now. (As long as we’re talking about bass-managed speakers, of course.) Each of my speakers is independently equalized, the front three with parametric, the back two a bit less-precisely with my receiver’s on-board quasi-parametric EQ. My ears and RTA confirm that response is not trashed when they are all operating together.


Trust me, something like that would never “just happen.” Independent measuring would identify the speaker(s) with the offending problem.

As previously eluded to... I can have a peak at 2KHz from measuring all speakers at once and easily cure it, just like I do with my subs. There is no way I could identify which speaker it is coming from if I tried to measure only one speaker at a time simply because it would not show up. It only shows because of the combination of speakers. I am not sure why this is so hard to understand. Unless you actually try it, you will never know.

When you have that 2KHz peak with the combined speakers measured, you do not need to know what speaker is causing the problem. Simply reduce 2KHz a little and remeasure... it will be reduced. It is no different than the way we equalize multiple subs. I promise... try it sometime.


Quote:
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If I may be so bold as to make a recommendation to you and Sonnie - why not do what I do when I’m trying to decide what the correct approach is: consult a pro!
For what I am referring to... no pro is needed... it is so very simple and it works fine.
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