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post #31 of 57 Old 07-30-2012, 09:24 PM
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Originally Posted by jim19611961 View Post

My ISD termination comes from a 140 degree angle (almost midway between directly back and directly to the side), but I have significant later reflections (arriving at 18-25ms) from 90 degrees (directly left and right).
I dont know why one would think I or anyone would go to all this trouble merely to please a meter.
Well, can we agree that you would be pleasing a meter if its values are incorrect and do not correlate with what we hear? That is precisely what is going on here. Dragon noted it to you himself in his second post in this thread. Sadly as I noted in the other thread, once he put disclaimer there he felt safe ignoring it. Please read that link and see how you cannot use the tool in a room with dissimilar surfaces.

If you care about improving the sound you hear, then you want to pay attention to research that says what reflections are beneficial, and which are not. As I explained, the answer simply depends on the direction of reflection and is invariant to the gain measured. It is also non-intuitive in that you can get rid of a reflection and yet, make the sound worse. Since you can visually determine the direction as you already did, what are you using the tool for? The only reason to continue to use it and sweat over the values it displays is to please the meter not your ears. Yes a lot of people do it because they have read on these forums that they should. But the research and math is quite strong as explained in the other thread. And it relieves us from spending the time and energy running and interpreting this tool.

But again, I don't want to interfere with your mission here. If you want to charge ahead and keep analyzing the output, I will bow out and let you do that smile.gif. I just ask that you read that one link. It takes but a minute or two to read it.....

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post #32 of 57 Old 07-30-2012, 09:36 PM
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Originally Posted by Bigus View Post

His absorption panels are fairly broadband being 8-12" thick, and thus the differences in broadband ETC measurements as a result if differing spectral content is minimized.
Minimized how? Where do you have the frequency dependent absorption of his diffuser? Here it is for an RPG product:

i-TTDmMvK-X2.png

How does that compare to his naked wall, carpet, a thick absorber, etc? He has a 4 inch absrober distanced from the wall on the corners. Here is a rough simulation of that:

i-GXX8zzp-X2.png

You think this product and the diffuser filter the direct sound spectrum the same because they are both "broadband?" They are not the same of course and as such you have no idea how far off the values are. You are shooting blind and with both feet tied smile.gif.

Again my apology to OP if he wants to continue down this path. I have explained all of this in the other thread and hate to repeat them again here. smile.gif

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post #33 of 57 Old 07-31-2012, 06:33 AM - Thread Starter
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Please, lets keep the discussion topic to ETC and ISD termination.

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post #34 of 57 Old 07-31-2012, 07:06 AM
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Quote:
Originally Posted by jim19611961 View Post

Please, lets keep the discussion topic to ETC and ISD termination.
Ha? That is all I was discussing. ETC is a processed impulse response (whether measured using that stimulus or swept sine technique). The impulse spectrum gets modified as the signal travels through different acoustic material. As soon as that happens, the amplitude representation for each cannot be compared to any other. In the thread I showed experiments by Dr. Toole showing how you can get errors as high as 20 dB in the wrong direction! (See http://www.avsforum.com/t/1413173/does-sound-sounds-better-in-a-room-full-of-furniture-and-stuff-or-without/510#post_22220887.) Once you have dissimilar surfaces, you simply cannot use this tool and compare the the height of one spike against the other as you are attempting to do. It is a misapplication of the measurement to do that. I showed quantitatively how this can be the case in my last response using the absorption coefficients of differing material you may have in your room. And how what you hear does not correlate with what the graph shows anyway.

I am not sure if you read the interchange in the other thread. Here it is again:
Quote:
Originally Posted by dragonfyr View Post

[From Dr. Toole's book] The message is that we need to know the spectrum level of reflections to be able to gauge their relative audible effects. This can be done using time-domain representations, like ETC or impulse responses, but it must be done using a method that equates the spectra in all of the spikes in the display, such as bandpass filtering. Examining the “slices” of a waterfall would also be to the point, as would performing FFTs on individual reflections isolated by time windowing of an impulse response. Such processes need to be done with care because of the trade-off between time and frequency resolution, as explained in Section 13.5. It is quite possible to generate meaningless data. All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects". p. 93

DUH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!rolleyes.gifrolleyes.gifrolleyes.gif If you need a text to explain this to you, the book won't help! It's too late! ...Combine that with the fact that existing treatments may indeed effectively EQ the incident energy and act as equalization, effecting some frequencies more than others.

Thus if one uses live material as a stimulus that may feature varying spectral content at differing times of the program, and you have boundaries or boundary treatments that do not behave in a broadband manner and may indeed effectively EQ the incident and reflected energy, you may indeed end up with whacked data. And anyone who conducts a test in such a manner is an idiot.
You see that it is all about discussion of ETC and how world class audio experts like Dr. Toole are saying you cannot run the tool in your already treated room for the reasons I explained. Dragon agrees and says one has to be an "idiot" to do so otherwise. Yes, like Bigus he thinks that just because a product is "broadband" it means it is OK but as I showed in my post it is not. And at any rate you are comparing naked surfaces and thin coverings to those that have much thicker treatment. It is just wrong all around.

So by all means if you prefer that I don't comment just say so. My feelings won't be hurt and you certainly have the option to tell me to go away smile.gif. But please don't say I am not discussing ETC. I am trying to do just that and answer the question you asked about which spike in that display is preferable to another. There is no answer to that question because the data is simply "untrustworthy." The math says that. The research says that. And the person you are trusting, Dragon, (almost) says that.

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post #35 of 57 Old 07-31-2012, 07:16 AM - Thread Starter
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It seems to me that you are arguing the relevancy of ETC. I am not.

Yes. I saw the other thread.

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post #36 of 57 Old 07-31-2012, 07:34 AM
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Quote:
Originally Posted by jim19611961 View Post

It seems to me that you are arguing the relevancy of ETC. I am not.
I realize you took it for granted that it is relevant and then asked this:
Quote:
Originally Posted by jim19611961 View Post

So given the choice, would you rather:
1) Have a -16db to -14db termination at 90 degrees (12ms) with a following peak(s) at the same magnitude (-14-16db) at 22ms
2) Have a -10db to -12db termination at 140 degrees (12ms)
You don't think it is appropriate to say a) those numbers could be way off from reality and b) they may have nothing to do with which one sounds better? You want them to be accepted regardless or else the person is off topic?

Once you asked what sounds better to a human and relied on specific values being right then you opened the path to the answers I am giving. If you note I did not respond prior to these questions being asked.

Anyway, I take this as another polite "go away" and will do exactly that. smile.gif Appreciate you letting me put in my two cents. Take care.

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post #37 of 57 Old 07-31-2012, 08:07 AM
 
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"Answers he is giving"???? LOL! Thus far he has only documented how his mentors followed a flawed process and ended up with measurements that were not wrong, but which simply could not be directly correlated with one another, and which due to the improper use of non-broadband treatments in direct contradiction to Toole's own stated process!

So now, since his mentors employed a flawed process, he now assumes tht ONLY way to proceed is to do so via his documented mistaken methodology. One wonders what he could do if he only took the time to get OUT of the ditch and learned to perform the process correctly in a manner where you CAN correctly compare the spectrally equivalent reflections???? But apparently we will have to wait for him to read another more comprehensive book.

Funny, our book report boy notes that an ETC run in an already treated room employing various non-broadband treatments is measuring reflections that are effectively EQ'd for spectral content.results in a response where the varying spectral content must be re-weighted in order to be directly compared. Something no one has ever debated, seeing as how we are aware of the proper process that should be employed, but about which he is still stuck in a ditch as his mentor tried this improper process and ran into problems was shocked at the outcome - an outcome which when originally published back in ~1987 was met with a universal yawn by the community already well aware of such a procedural MISTAKE and aware of how a bandwidth limited analysis could indeed be used as a diagnostic tool to evaluate said behavior...

But he fails to address he alternative which properly involves establishing a baseline behavior in an untreated room, and then proceeding to treat using broadband treatments and then verifying the behavior with proof of performance followup measurements.

You see, he is myopically hung up on how to do things incorrectly and assumes that everyone does things incorrectly, as he has set a precedent, not by ever having actually measured anything with his "ETC Meter", but by virtue that he read of his mentor using the erroneous technique and then encountering problems as a result of employing a flawed process.... So he is definitely in touch and a voyeuristic expert with how to do things WRONG.


On the other hand you could ask him for an objective process by which to analyze the specific actual space and for the second time in history listen to silence, just as has happened when he was queried about this in the past! (Heaven forbid that he would ever present a CORRECT way that the tools could be used ) - but then he would have to contradict himself and acknowledge that there is a way to avoid making the same mistakes that his mentor employed to get, not incorrect, but simply misleading results that must be normalized in order to be correctly compared.

You see, this is all a bit complex for someone who has never even seen an "ETC meter", let alone made acoustical measurements in a space, nor actually treated a room based upon the actual awareness of what was happening in the room acoustically. But he does have a book!

Or you could inform him that you are not interested in an amorphous imprecise image, opting for the scenario where Toole himself acknowledges that a more accurate precise image results from the control of early reflections by the employment of broadband treatment..

You COULD try any of the above, but it won't matter, as book report boy is not interested in helping you achieve the response that YOU prefer!

He is simply interested in pushing the one trick pony reflection rich Bose response that he has determined that EVERYONE MUST prefer.

You see, in exercising your free will, you really have NO choice. He is only attempting you to coerce you into freely choosing what is best for you as decided for you by himself, based upon an abstract reference to a survey. And you should feel very ashamed for having the audacity to exercise your own preference and disagreeing like those miscreant professionals dared to do in Blackbird! How dare you disagree!. rolleyes.gifrolleyes.gifrolleyes.gif

After all, he has read A book and attended A 'class'. How dare you question his authority?


"Anyway, I take this as another polite "go away" and will do exactly that."

Yeah, like it worked the first time.... "A consummation devoutly to be wished"!



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post #38 of 57 Old 07-31-2012, 08:23 AM - Thread Starter
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Everyone's 2 cents is welcome smile.gif

I just dont want to wander from the topic too much.

I do think the spectral content is important, so here are 200us smoothed 1 octave ETC's

Blue = 4.2k
Green = 2.6k
Yellow = 1.6k
Orange = 1k
Red = 668hz





At the 11.6ms ISD terminatiion, all the frequencies are present and at the same magnitude. This I think is good smile.gif

This unfortunately isnt the case across the entire time domain. Not sure how much I can fix that, but this is my next area to look at.

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post #39 of 57 Old 07-31-2012, 10:08 AM
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Quote:
Originally Posted by amirm 
Well, can we agree that you would be pleasing a meter if its values are incorrect and do not correlate with what we hear?
Please stop spreading misinformation.

Quote:
Please read that link and see how you cannot use the tool in a room with dissimilar surfaces.
You can. Please stop spreading misinformation.

Quote:
As I explained, the answer simply depends on the direction of reflection and is invariant to the gain measured.
This is not what the research shows.

Quote:
Since you can visually determine the direction as you already did
You cannot.

Quote:
But again, I don't want to interfere with your mission here.
Yes, you do.

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post #40 of 57 Old 07-31-2012, 10:10 PM
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Please don't take this in the wrong way, but it is kind of funny, I've been busy in the real world and not posting here so much, now I took a look in and you guys are still at it! Great stamina LOL smile.gif

Now a teaser especially for dragon...nice use of bandwidth limited ETCs and smoothing biggrin.gif

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post #41 of 57 Old 08-01-2012, 06:01 AM
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welcome back, Nyal.

since you brought it up, ill add that i am still awaiting your response that i've asked multiple times in the past that i was curious on: how you are using band-limited ETC's to design custom treatments (based on the data within the band-limited ETC)?
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post #42 of 57 Old 08-01-2012, 06:35 AM - Thread Starter
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Quote:
Originally Posted by Nyal Mellor View Post

Please don't take this in the wrong way, but it is kind of funny, I've been busy in the real world and not posting here so much, now I took a look in and you guys are still at it! Great stamina LOL smile.gif
Now a teaser especially for dragon...nice use of bandwidth limited ETCs and smoothing biggrin.gif

You and spoke at length some months back. At the time I wasnt posting anywhere. Well, here I am smile.gif

So, do you find my my ETC tracking to have acceptable variance? Do I need to knock down the 1k & 668hz some? (or boost the others)

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post #43 of 57 Old 08-01-2012, 06:48 AM
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Quote:
Originally Posted by dragonfyr View Post

Funny, our book report boy notes that an ETC run in an already treated room employing various non-broadband treatments is measuring reflections that are effectively EQ'd for spectral content.results in a response where the varying spectral content must be re-weighted in order to be directly compared. Something no one has ever debated, seeing as how we are aware of the proper process that should be employed, but about which he is still stuck in a ditch as his mentor tried this improper process and ran into problems was shocked at the outcome - an outcome which when originally published back in ~1987 was met with a universal yawn by the community already well aware of such a procedural MISTAKE and aware of how a bandwidth limited analysis could indeed be used as a diagnostic tool to evaluate said behavior...

On the topic of BW limited ETC....dragonfyr, when I was interested in this topic here http://www.avsforum.com/t/1351247/using-energy-time-curve-for-acoustic-analysis-developing-a-home-theatre-primer/150#post_21399794 if memory serves (you deleted a bunch of your posts in this thread) you replied that I need not worry about spectral content of the ETC and that treatment (whatever method is chosen) needs to be broadband. Now (unless I am not interpreting your reply properly) you are indicating that a BW limited analysis can indeed be used as a diagnostic tool. Can you elaborate?

Where I see value in such an analysis (and pending Nyal's response to Local's question) is where the vast majority of us don't know their actual power response of their speaker, and being able to see just what the reflected spectral content is compared to direct. Perhaps one will base their FR treatment based on how skewed the FR is, or elect to not treat at all if reflected spectrum is deemed as "good off-axis response"? For purpose of discussion, I am talking to sidewall FR's.
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post #44 of 57 Old 08-01-2012, 07:43 AM
 
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How can a BW limited ETC be used as a diagnostic tool?

You can simply employ it to examine a particular treatment to see exactly how the various incident frequencies are addressed and the degree of absorption, reflection or scattering/diffusion that results.

This can be useful in the process of R&D or in the case of an existent but unverified treatment (provided sufficient conditions are met to sufficiently isolate the treatment behavior from the surrounding context such as are addressed in the new absorption and diffusion standard being proposed by Ron Sauro and Petr D'Antonio, primarily as result of Ron's recent testing that has basically invalidated (rendered "inaccurate at best") "the existent ISO-354 and ASTM C423 testing standards, as well as ISO 17497 modified as proposed to ISO 17497-1. Which is rather ironic that these guys should be the prime movers behind the 'renovation' of the testing standards since we have read recently by a another party(ies) that their activities have been largely inconsequential compared to yet another who is here nowhere to be found...)

And while useful in the R&D or testing of individual samples where more standard techniques such as a Bundt tube or other means to determine acoustical impedance or scattering/diffusion coefficient data are not readily available. Again, the need for this is rather limited in general testing in a space where the goal is to work from a baseline and to devise a comprehensive complementary schema that works to a desired result.

And as far as addressing various variations in the spectral composition of the source. the use of broadband treatment addresses that issue without the need to customize the treatment to varying spectral content - which would be a pain at Best and render much of the treatment custom in each case! And if such a course of action were followed, you would not want the bill!

I have not changed my position at all. They can be useful for diagnostic and R&D purposes. But if best practices are followed in both room analysis, and known treatments are utilized, they are generally not needed. Once a baseline behavior is established and known sufficiently broadband treatments are utilized, the need for BW limited analysis is minimal, if not entirely unnecessary, in situ.
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post #45 of 57 Old 08-01-2012, 08:50 AM - Thread Starter
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Looking at the area I have circled in orange, this is the floor area between the listener and the speaker. I have carpeted floors and this is just the kind of response you would expect from carpet. Muted highs and less lower midrange attenuation. The blue circled area is the side wall reflection where I have 12" deep R19. See how much closer together everything is?

You can look all over this plot and see where it seems that carpet is the primary reflection surface. In other areas, where the different 1 octave plots converge, it seems obvious this is a broadband absorption or diffusion panel reflection.

So the question(s) to me becomes:

1) Do you strive to have every area of the graph with convergence (having each 1 octave plot run together at the same energy magnitude)?
2) Do you only concern your self with the more "high energy" reflections?
3) Do you come to realize that the lower frequency plots will always be a bit higher due to room modes and the nature of the frequencies themselves?

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post #46 of 57 Old 08-01-2012, 10:15 AM
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Originally Posted by localhost127 View Post

welcome back, Nyal.
since you brought it up, ill add that i am still awaiting your response that i've asked multiple times in the past that i was curious on: how you are using band-limited ETC's to design custom treatments (based on the data within the band-limited ETC)?

First let me say they are not 'custom' in the sense that I've designed and manufactured them, though this would be theoretically possible to a degree by combining perforated / slatted resonating absorbers and fiber glass.

Where I have used the concept has been specifically in relation to speakers where the off axis response droops significantly above a certain frequency. You can then 'match' a product that is selectively absorptive over the frequency range (like a BAD panel or panel with some form of paper or membrane on the surface) to 'prop' up the higher frequencies at the listening position (since the FR at the LP above the modal region is a combination of the direct and reflected sound from the boundaries). I say 'match' because obviously it is not an exact science. Of course you could choose the other route which is to absorb the offending reflection completely and there is certainly nothing wrong with that approach.

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post #47 of 57 Old 08-01-2012, 10:21 AM
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Originally Posted by jim19611961 View Post


Looking at the area I have circled in orange, this is the floor area between the listener and the speaker. I have carpeted floors and this is just the kind of response you would expect from carpet. Muted highs and less lower midrange attenuation. The blue circled area is the side wall reflection where I have 12" deep R19.
You can look all over this plot and see where it seems that carpet is the primary reflection surface. In other areas, where the different 1 octave plots converge, it seems obvious this is a broadband reflective or diffused reflection.
So the question(s) to me becomes:
1) Do you strive to have every area of the graph with convergence (having each 1 octave plot run together at the same energy magnitude)?
2) Do you only concern your self with the more "high energy" reflections?
3) Do you come to realize that the lower frequency plots will always be a bit higher due to room modes and the nature of the frequencies themselves?

Jim your analysis of band filtered smoothed ETCs is EXACTLY on point with how to use this type of measurement in the context of room acoustic analysis.

1) ideally, though difficult in practice
2) those would be the focus, since they contribute most to the overall frequency response (what we hear)
3) for me it's mostly due to speaker directivity and the fact that small speaker baffles (the most common type today) can't control the dispersion of bass frequencies. Last time I looked at it you needed something like an 18" baffle to control directivity down to 300Hz (don't quote me on this I don't have the figures in front of me but it's in the right ballpark)

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post #48 of 57 Old 08-04-2012, 05:59 AM - Thread Starter
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In an effort to better handle some of those uneven responses after 12ms, I am building 4 - 22" x 40" N13+4 QRD's.



Replacing some older N7's that didnt cover enough area or really go deep enough.


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post #49 of 57 Old 08-04-2012, 06:34 AM
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you can fit N19+5 w/ 1" well width into the same period width..
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post #50 of 57 Old 08-04-2012, 07:52 AM - Thread Starter
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Quote:
Originally Posted by localhost127 View Post

you can fit N19+5 w/ 1" well width into the same period width..




I could, but the low end response isnt nearly as good (for the same 5 1/2 inch depth) which i am limited to in this case.

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post #51 of 57 Old 08-04-2012, 08:21 AM
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Quote:
Originally Posted by jim19611961 View Post

(for the same 5 1/2 inch depth) which i am limited to in this case.

acknowledged -
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post #52 of 57 Old 08-04-2012, 08:56 AM - Thread Starter
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Quote:
Originally Posted by localhost127 View Post

acknowledged -

For onlookers, the N19+5 would have to be 7 9/16" deep to achieve the same low freq cutoff (377hz).

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post #53 of 57 Old 08-28-2012, 04:47 PM - Thread Starter
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Been busy the last few weeks. Working on my room, of course. Worked my ISD gap to a bit over 14ms.

Changed the room a bit as well.


My Room
http://www.gearslutz.com/board/studio-building-acoustics/817205-my-listening-room.html

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My Equipment

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(2) Classe CA-100 bridged power amps (350w)
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post #54 of 57 Old 09-02-2012, 04:31 PM - Thread Starter
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Decided to start all over once again with a longer gap, now a 24ms termination. This is sounding the best so far of all my attempts.

My Room
http://www.gearslutz.com/board/studio-building-acoustics/817205-my-listening-room.html

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My Equipment

Rega - Apollo
Rega - DAC
Goldpoint Passive
(2) Classe CA-100 bridged power amps (350w)
Jenzen Next ( http://www.troelsgravesen.dk/Jenzen-NEXT.htm )
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post #55 of 57 Old 10-24-2012, 04:24 PM - Thread Starter
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Update smile.gif

My Room
http://www.gearslutz.com/board/studio-building-acoustics/817205-my-listening-room.html

My Music
http://rateyourmusic.com/~jim1961

My Equipment

Rega - Apollo
Rega - DAC
Goldpoint Passive
(2) Classe CA-100 bridged power amps (350w)
Jenzen Next ( http://www.troelsgravesen.dk/Jenzen-NEXT.htm )
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post #56 of 57 Old 10-24-2012, 05:39 PM
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In what way does it "sound" different?

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

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post #57 of 57 Old 10-25-2012, 01:18 PM - Thread Starter
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Quote:
Originally Posted by craig john View Post

In what way does it "sound" different?
Craig

Less dead. More ambient and spacious.

My Room
http://www.gearslutz.com/board/studio-building-acoustics/817205-my-listening-room.html

My Music
http://rateyourmusic.com/~jim1961

My Equipment

Rega - Apollo
Rega - DAC
Goldpoint Passive
(2) Classe CA-100 bridged power amps (350w)
Jenzen Next ( http://www.troelsgravesen.dk/Jenzen-NEXT.htm )
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