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Differing speaker measurements
Old 18th August 2012
  #31
Gear Guru
Nope

The graph presented illustrates the effect of Eq ing for one spot and measuring at another. The Eq in question was not highly regarded by practitioners of these techniques. The harman tests I linked show a couple of products making matters worse. Hard cases make bad law.

Products from years later, i.e. now, do not sample at a single location.
e.g. Dirac Live samples NINE locations within a chosen listening area.
Even Audessey has totally changed to a MultEq incarnation.
The Eq's are very different now, e.g. Mixed Phase Filters.
Some products include Time Domain corrections.
Convolution is sometimes involved.

So the very old graph shown is derived from a non working Eq, restricted to one sample spot. I suggest it is a nonsense to feast on the fruit of a poisoned tree.

bwo has provided spectacular examples of exactly the opposite happening. Audiolense correcting multiple sampled locations. With modal shortening and null filling.


Room Eq Wizard auther JohnPM writes calmly and dispassionately about what Eq will and will not do.

REW Manual/Minimum Phase/Excess Group Delay

John and Jeff have written extensively on this and I have provided links to it before, in earlier incarnations of this same dialogue.


My instinct and what I am hearing, suggests to me that Modal Peaks at Low frequencies cover wide areas, so I expect mode shortening and level drop to tally.
Tests will show one way or the other shortly.

EDIT, While Helmholtz resonance/damping is critical, I don't think the Eq adjustment of modes is critical. JohnPM showed a 50Hz mode being shortened by different amounts using different amounts of Eq.

An unexpected and very welcome result seen in many DRC tests is the filling in of nulls.

In short things have changed and continue to so in an accelerating manner.

To watch IMHO, MiniDSP, DEQX, Trinnov.

DD
Old 18th August 2012
  #32
Quote:
Originally Posted by Ethan Winer View Post
I'm very curious, how large is that particular room? At what room sizes does EQing modal peaks become reasonable in terms of covering a large enough spot? There must be some distinctions you could articulate on this matter considering that you use EQ for modal peaks in your HT.
Old 19th August 2012
  #33
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Ethan Winer's Avatar
 

Lightbulb

^^^ That room is 16 feet long by 11.5 feet wide by 8 feet high. EQ'ing modes can be useful when the mode is dominant in many locations around the room. But I'd never EQ a mode to flat. If the peak is 6 dB I'd apply maybe 3 dB of cut.

--Ethan
Old 19th August 2012
  #34
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Ethan Winer's Avatar
 

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Quote:
Originally Posted by DanDan View Post
Products from years later, i.e. now, do not sample at a single location.
The Audyssey system I tested was extremely expensive, and it made the same claims as more modern systems. It also measured at many locations, but that's not the issue. You can measure at 5,000 locations, but you're still applying a single EQ curve. And that curve can only make things worse elsewhere in the room.

Dan, if you can link me to one or two posts that prove EQ reduces ringing for more than a single spot, I'd love to see it. But please don't link to a 30-page thread and say to read it all. heh

--Ethan
Old 19th August 2012
  #35
Gear Guru
Nope

Any serious current system measures at multiple locations. Then in effect, they generate an Eq for each location. Some apply intelligent algorithms to 'weight' their Eqs. I would expect the most sophisticated ones to take account of interaction between the bands of Eq. Furthermore, many of the systems involve Time Domain correct, so to regard this as simple traditional Eq would be misleading.
One could say all these Eq's form a single curve, but that would be very misleading. It is either many curves or a complex composite. The corrections are calculated to cover an area not a single spot.

It would be very easy to show any of these systems underperforming by chosing a spot outside the correction envelope or by sampling only one spot etc. etc.
Ethan, which version of Audessey did you try and when? How many locations did you measure? If more than two, did you present the worst case comparison, the best, or a representative middle ground?

I, bwo, and others have provided links showing DRC working over multiple locations in the past. I have offered to do specific A/B blind testing on Ethan's converter files in the past. This was not accepted as fully blind testing unless we could be in the same room. In which case, there is no point in presenting anything remote. I recommend Ethan, or anyone else, to test your own situations. Demo Dirac or AudioLense. Or use REW with a plug in Eq. REW will predict whether your modal peak is amenable to Eq or not. It will also predict the result after it's recommended Eq. A few locations will show how wide or not the modal shortening and level change covers.

DD
Old 20th August 2012
  #36
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by DanDan View Post
Any serious current system measures at multiple locations. Then in effect, they generate an Eq for each location. Some apply intelligent algorithms to 'weight' their Eqs. I would expect the most sophisticated ones to take account of interaction between the bands of Eq. Furthermore, many of the systems involve Time Domain correct, so to regard this as simple traditional Eq would be misleading. One could say all these Eq's form a single curve, but that would be very misleading. It is either many curves or a complex composite. The corrections are calculated to cover an area not a single spot.
Dan, you give these devices way too much credit. The reason they ask the user to measure at many locations is to avoid making a stupid mistake. As you know, peak and null levels and frequencies vary around a room by 30 dB. If an auto-EQ system were to measure only once, and the result was like this graph below, it would probably lower the peak at 110 Hz by 15 dB:



But that would be way too much reduction, since it's likely that for ten other nearby places in the room that frequency is lower or is not a peak at all. So asking for many measurements reduces the chance of dumb mistakes.

Quote:
It would be very easy to show any of these systems underperforming by chosing a spot outside the correction envelope or by sampling only one spot etc. etc.
If you read my Audyssey Report you'll see that it was unable to reduce ringing even at the very same place its own calibration microphone was placed. Look at the second photo down on the left. From that page:
Quote:
Originally Posted by Audyssey Report
Audyssey claims to flatten the response and reduce ringing over an area large enough to encompass multiple seats, so I measured at three adjacent locations on Kal's couch. It turns out this was not necessary because the MultEQ was unable to reduce ringing even at the same place it was calibrated for.
Quote:
Ethan, which version of Audessey did you try and when? How many locations did you measure? If more than two, did you present the worst case comparison, the best, or a representative middle ground?
As explained in the article, this was the MultEQ system. Yes, my friend Kal measured at many locations as he calibrated the Audyssey. I don't remember exactly how many places, but it was at least as many as was recommended.

Quote:
I, bwo, and others have provided links showing DRC working over multiple locations in the past.
"Working" has many meanings. Did it reduce ringing at multiple locations, or only reduce the level of the one or two lowest modal peaks? Again, a system like this can apply only a single "correction" no matter how many places you measure at. Physics tells me it's impossible to reduce a peak in one place without making other peaks and nulls worse somewhere else within the area of concern. I refer you again to my "four inches apart" graph in Post #30 above.

--Ethan
Old 20th August 2012
  #37
Gear Guru
Semantics

I and some clients and practicing acoustician friends, are finding them very useful Ethan.
As I said, that Audessey system you tested, is not highly regarded. Afaik, that is, because you haven't told us which one was tested? Or how long ago it was? To be pedantic here, you haven't exactly directly answered the other real questions either.
e.g. Did you chose a worst case pair of measurements?

Quote:
reduce the level of the one or two lowest modal peaks? Again, a system like this can apply only a single "correction"
Spock would have a field day, but sticking to basic English language logic :-
A single correction can only affect one modal peak. Self evident.

You can't have the cake and eat it and still have it.

I don't think you are prepared to take on board the spatial averaging thing.
I will say it again. A single mic measurement is a nonsense unless one is listening through the nose.

Nor the multiple corrections. The software I am testing has a viewable filter curve for each of the nine sampled locations.

As I said before, I find the null filling most interesting.
Also as before, in a well treated room, with speakers and listener in optimum locations, the effect of such systems is subtle. Still useful to me, as I like to correct the speakers too, both for linearity and to my chosen Target Curve. In a bad situation with little treatment, poor postioning, the difference can be night and day.


We have had these banters before Ethan. You will not convince me that what I am hearing and measuring is false. Nor vice versa. I and others have presented you with plenty of evidence.
Do you really really think JBL, Trinnov, DEQX, AntiMode, Dirac, AudioLense, MiniDSP, REW, Nyal, Jeff, me, etc. etc. etc. are fooling ourselves?
Ultimately you have insisted that a test would be worthless unless you were physically present.
That makes further banter on these sticking points useless. I could reliably hear to the point of identifying those converters yet you simply refused to rename the files. What could be more blind?
Perhaps Jack Nicholson in 'A few good men' can fill in the next line.
Let's leave it there. We are way OT.
I may post more test results from my experiments soon. Although I am a bit conflicted about 'Shilling'.
Whatever about positive testimonials I am very down on Attack adverts, as seen in US politics and I am sorry to see the RealTraps site.




DD
Old 21st August 2012
  #38
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Ethan Winer's Avatar
 

Lightbulb

Dan, I spent 20 minutes on that post yesterday and I answered all of your questions! Please read more carefully. No, I didn't "pick" a worst case. I measured at the same place as Audyssey's microphone was when it was calibrated, and even there it didn't reduce ringing. If that system, which cost thousands of dollars, is not "highly regarded" that's not my problem.

Did I really say I won't accept test results without being present? I've said that about other types of tests, like the guys who claim to be able to hear when their AC power cord is changed. But I'd accept your tests. But it has to be thoroughly documented, and it has to show the response and ringing at multiple locations within some stated area. Unless I've missed something, all the test results I've seen show only one location.

As for my article, I know the test was done properly, and it was witnessed by another acoustics expert. So I stand behind that article. If there are better systems today, that's fine. But the system I measured did not do what it claimed. Nor does it seem physically possible. So as far as I'm concerned the burden of proof is on those who claim EQ / DSP can reduce ringing at more than one seat in the room.

--Ethan
Old 22nd August 2012
  #39
Gear Guru
Done

20 Minutes without saying which version of Audessey and what year the tests were done. I am sceptical of tests with a couple of practitioners involved.
Distributed responsibility.
See page 228 of the MHOA. That test was done by a friend of Doug's.

Several of us have presented plenty of evidence of DRC working just fine, it had no effect on Ethan's opinion. Soon enough I will provide the spatially averaged and spot specific testing in a bulletproof manner. But I am quite sure that will not alter Ethan's opinion either.

Quote:
Did I really say I won't accept test results without being present?
Yes, you surely did, kinda knocked me for six. You are an obstinate donkey....loveable though....:-)

DD
Old 22nd August 2012
  #40
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Ethan Winer's Avatar
 

Lightbulb

Dan, you have totally lost me. I said in my article and in the post above that the specific device tested is the Audyssey MultEQ. The article makes it clear that my test was done in February, 2007. As for Page 228 of MHOA, that shows a reduction in ringing after adding a Helmholtz bass trap. What that has to do with room EQ I have no idea!

Quote:
Soon enough I will provide the spatially averaged and spot specific testing in a bulletproof manner.
Excellent, I look forward to that.

--Ethan
Old 23rd August 2012
  #41
Gear Guru
Dates

My apologies, in the article I see a reference to a Face off 2005, emails to Audessey in 2006, and then MultEq. Reading it again, I see you have removed the first face off and replaced it with the newer 2007 MultEq one.
OK, 5 years ago.
And as many consider Audessey relatively ineffective, it hardly fair to infer anything about more recent or indeed, any, other systems.

I linked to a survey which showed similarly several products not functioning at all. The same survey showed good approval ratings for the products that work.

Hard cases make bad law.

The MHOA test is IMO flawed/faked. I tried to recreate that rather spectacular result but completely failed. With subsequent learned experience I am now fully convinced such results from a single small device are impossible.
Doug wrote the article, his friend did the test. He trusted his friend.
The result is nonsense with no-one responsible for IMO fake.
I would be happier if you had calibrated the MultEq and tested it yourself. A short but competent chain of responsibility.

If you are interested and have a scientifically open mind, I recommend you try a demo of AudioLense. The results I have seen are most impressive.
I am testing Dirac (Mac) so we could compare notes.

DD
Old 29th August 2012
  #42
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Ethan:
Audessey isn't considered a goodt room correction program. In Harman Int. blindtest is came out last. Your test doesn't give an answer about room correction in general. Harman Int. who tested several came to another conclusion. Ok, they sell room correction, so we should have that in mind.

I'm not a believer in room correction myself (I've tried Audiolense) and don't believe you can effectively correct the room without introducing negative effects. Don Davis said: You can EQ the speakers but not the room. I think he was right when one has a goal of only improving. Trying to correct the room and speakers like Audiolense does will certaintly have it's sideeffects. Correcting only speakers, like DEQX does, is something else.
Still, sometimes I think the positive effects or changes can make up for the negative ones and it sounds overall better to some people.
Old 29th August 2012
  #43
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Quote:
Originally Posted by bwo View Post
.......Don Davis said: You can EQ the speakers but not the room.......
No, it's not possible to equalize resonant process in the loudspeaker, this behavior is usualiy called linear distortion, and it is needed to be solved by loudspeaker construction (only). It is same situation with edge diffraction.
No free lunch, sorry.

Old 29th August 2012
  #44
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Quote:
Originally Posted by boggy View Post
No, it's not possible to equalize resonant process in the loudspeaker, this behavior is usualiy called linear distortion, and it is needed to be solved by loudspeaker construction (only). It is same situation with edge diffraction.
No free lunch, sorry.

Not sure what you're saying, but every speaker has EQ of the drivers. It can be done passively or with an active crossover.
Old 29th August 2012
  #45
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Quote:
Originally Posted by bwo View Post
Not sure what you're saying, but every speaker has EQ of the drivers. It can be done passively or with an active crossover.
Yes, but loudspeakers may have resonances too, which cannot be equalized (they will still exist, whatever filters we apply), so it's a same problem as room modes. Cabinet edge diffraction cannot be equalized too (same as non resonant interferences in the room). So problems are the same as room acoustics, if we trying to equalize resonant and non resonant interference in both, loudspeakers and rooms, this won't work.

Resonant and non-resonant interferences must be solved by acoustical design, for both, loudspeakers and rooms, not by controlling electrical part of loudspeakers.

EDIT: I trying to say that we must compare the same problems in rooms and loudspeakers, and possible solutions, not apples (resonant and non-resonant interference) and oranges (HP roll-off equalization of the tweeter to get Linkwitz-Riley fourth order acoustical response type, with applied high pass filter).


EDIT2:

This is waterfall plots of tweeter responses:
you can see or not see resonances (or they are out of audible range), which strongly depends of type of tweeter (acoustical design):
Goldwood_GT-525

Accuton_C23-6

ScanSpeak_9500


This is a good example that we cannot EQ this anomalies, and tweeter choice is only way to avoid it.

(graphs are from Zaph|Audio)
Old 29th August 2012
  #46
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I see. I would say resonances are mainly due to poor speaker constructions. OB don't have any for obvious reasons and boxes can be made where the resonances are below what's audible. At least that's what we assume from studies on this. Diffraction varies greatly among speakers. This is one way to deal with it.


I get your point though.

Looks like you are talking about distortion as well.
Attached Thumbnails
Differing speaker measurements-rd-75-06.jpg  
Old 29th August 2012
  #47
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Quote:
Originally Posted by bwo View Post
I see. I would say resonances are mainly due to poor speaker constructions.
Yes, and cannot be improved by controlling electrical part of loudspeakers
Quote:
Originally Posted by bwo View Post
.........
I get your point though.

Looks like you are talking about distortion as well.
Yes, specifically, resonances in drivers are called linear distortion, and this don't mean non-linear distortion (THD), which exist too, but they aren't the same thing.
Old 29th August 2012
  #48
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Yeah. Distortion in speakers are very high compared to electronics. This is where planar speakers like Quad and Soundlab are quite good.

Distortion in a speaker aren't considered as important though as frequency response and dispersion/power response. But I'm sure it's audible and there are room for approvements.
Old 29th August 2012
  #49
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Quote:
Originally Posted by bwo View Post
Yeah. Distortion in speakers are very high compared to electronics. This is where planar speakers like Quad and Soundlab are quite good.

Distortion in a speaker aren't considered as important though as frequency response and dispersion/power response. But I'm sure it's audible and there are room for approvements.
Linear distortion (resonances/difractions in drivers/cabinets) is different "beast"... and it is virtually more audible than THD, especially in well acoustically treated spaces...
Additionaly, if THD is nearly constant for whole frequency range, people usually accept this system more relaxed as "transparent", whatever real value of THD actually is, 0.05%, or 0.001%

EDIT: This is a reason why listed value of THD at (only) 1kHz, doesn't means anything in regards of transparency of audio device.
Old 29th August 2012
  #50
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by bwo View Post
Still, sometimes I think the positive effects or changes can make up for the negative ones and it sounds overall better to some people.
Yes, in a nearly cube room like the one we used for the Audyssey test, EQ'ing down the two worst bass peaks definitely increased clarity in the mids and low mids. I mentioned that in the article.

I was reading the opinion of an audio expert friend the other day in another forum, and he said that room EQ can be helpful as long as you don't try to counter the problems fully. This is the same advice I give in my Audyssey Report: If you have a 6 dB peak, EQ it down by only 3 dB.

Another audio expert friend of mine explains the science very well: The more correction you apply, the smaller the affected area becomes. So if you try to force the response to be perfectly flat at one location, it is certain to be totally screwed somewhere else, possibly even very close by.

I was going to start a new thread, but instead I'll just post this here:

I would like to do this test again. Is there anyone within two hours of me in western Connecticut who has one of the "better" room EQ systems? I'd like to visit with my laptop and REW. Can we get a list in this thread of room EQ systems that are considered "good"? There's no point in testing Audyssey again.

--Ethan
Old 29th August 2012
  #51
I'll get the popcorn...
Old 29th August 2012
  #52
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The Harman International's room correction would be worth checking out.
Trinnov, Dirac and Acourate are the other ones that come to my mind.

AudioVero
HARMAN JBL Synthesis® Now Offers Its ARCOS Adaptive Room Correction and Optimization System To Achieve A New Level of Accuracy For Home Audio | JBL Synthesis
http://www.trinnov.com/technologies/...on/?lang=en_us
Old 30th August 2012
  #53
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Lightbulb

^^^ Excellent. Anyone near me have one of those?

--Ethan
Old 30th August 2012
  #54
Gear Guru
New

A new test by you would be most welcome Ethan.
Such tests have been seminal in the past.
For the sake of neatness and being On Topic, I recommend a new thread.
I would be happy to post the results of my own tests there also.
Also, I recommend keeping the identity of the particular product tested secret.
I would guess that quite a few are available to download and demo?
bwo, you showed great results from AudioLense before, has your opinion on that one changed?

DD
Old 30th August 2012
  #55
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Quote:
Originally Posted by DanDan View Post
A new test by you would be most welcome Ethan.
I too, would be interested in the results of such a test.

Definately worth a thread of its own!
Old 31st August 2012
  #56
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It would also be interesting to compare the results with those obtainable with REWs own corrective measures using e.g. the FBQ.
Old 31st August 2012
  #57
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by DanDan View Post
A new test by you would be most welcome Ethan.
Such tests have been seminal in the past. For the sake of neatness and being On Topic, I recommend a new thread.
Yes, for sure a new thread. But first I need someone local to PM or email me that they have one of those products and would let me visit to do some measurements. Anyone? I'm halfway between Hartford, CT and New York City. Surely someone within two hours of me has one of these!

--Ethan
Old 31st August 2012
  #58
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Bjorn Omholt's Avatar
 

Quote:
Originally Posted by Ethan Winer View Post
Yes, for sure a new thread. But first I need someone local to PM or email me that they have one of those products and would let me visit to do some measurements. Anyone? I'm halfway between Hartford, CT and New York City. Surely someone within two hours of me has one of these!

--Ethan
Ask at several forums.
Or you could try out Acourate which I believe can be demoed for a period of time.
Old 3 weeks ago
  #59
Low-end contribution this, in more senses than one: with a pair of Yamaha HS7 fronts and two home-built subs, an L minus R delayed rear and analogue EQ, I get pretty good domestic results across most musical genres. Bach organ down to 16 Hz, doors visibly shaking, reasonably believable vocals. As a former BBC recordist I am fairly discriminating, but not wealthy!
What persisted, as others note here, was a room dip: in my case at 100 Hz. EQ indeed did not help. Secret remedy - an additional 2 cu ft speaker, focused just on 100, and at low volume, at back of room near where I sit.
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