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Old 18th April 2012, 04:20 PM   #111
jim1961 is offline jim1961  United States
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Originally Posted by gedlee View Post
To me its what is going on below 10 ms that is the most important. The curves are obviously much more complex and things change rapidly in this time region. So I would want to see your green and yellow line and the impulse response (not some time averaged ETC curve) from 0-10 ms. Out to 100 ms is simply a waste of paper. 0-20 ms. maybe (I am assuming that we are talking about a small room like we find in a home where there are lots of reflection < 10 ms.)
I draw it out to 100ms because I am interested in both IMAGING and SOUNDSTAGE. And in my understanding, 20ms-80ms are important to the later and 0-20ms, the former.

The graph I showed was at 1.2k at .33 oct (1122hz-1414hz only). Therefore, it is not representing or trying to represent the entire frequency range. My software allows you to look at different frequency centers with different octave ranges. What i do is separate plots at 317, 500, 800, 1200, 2000, and 3200hz at .33 octave. Since ETC is spectrally blind, I look at several ranges. In looking at a number of plots, breaking the entire frequency range into small pieces, I get a sense for whats happening at different frequencies in regard to different areas of the frequency range.

Last edited by jim1961; 18th April 2012 at 04:20 PM. Reason: syntax
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Old 18th April 2012, 04:51 PM   #112
jim1961 is offline jim1961  United States
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Originally Posted by boris81 View Post

The most important factor for the focus of the stereophonic image I found to be the equal distance of the speakers to the sidewalls. When centering the speakers one must be careful to align not only the distance to the wall but also the angle at which the speakers face the listening position.
This is key. I would expand this reasoning to not only considering symmetry to the side walls, but to the entire room from the listening position all the way back to the wall behind the speakers. The left and right should be mirrors of each other as closely as possible. Behind the listening position seems a bit less critical. To what degree I am not sure. But certainly what is in front of you and directly to the side of you, viewing from the listening position, is of great importance.
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Old 18th April 2012, 05:32 PM   #113
gedlee is offline gedlee  United States
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I understand the concept of "imaging" but I do not know what constitutes "soundstage". (Sounds like just another word for "Spaciuosness").

In a small room I would say that perception is dominated by the very early stuff. Its almost over by 20-30 ms. And not much of our perception is going to change for sound > 50 ms. except for a little additive "spaciousness".

I would not filter or integrate the impulse response and just show it full range over this time period. I might be tempted to high pass at 500-1 kHz (and mybe LP at 10 kHz) since as far as imaging is concerned that is the most critical range of frequencies.
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Old 18th April 2012, 05:44 PM   #114
jim1961 is offline jim1961  United States
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Originally Posted by gedlee View Post
I understand the concept of "imaging" but I do not know what constitutes "soundstage". (Sounds like just another word for "Spaciuosness").

In a small room I would say that perception is dominated by the very early stuff. Its almost over by 20-30 ms. And not much of our perception is going to change for sound > 50 ms. except for a little additive "spaciousness".

I would not filter or integrate the impulse response and just show it full range over this time period. I might be tempted to high pass at 500-1 kHz (and mybe LP at 10 kHz) since as far as imaging is concerned that is the most critical range of frequencies.
I think soundstage is a bit like spaciousness. And I also think that audio reflections >50ms do amount or account for spaciousness. What I want is my cake and eat it too. I want detailed imaging but also a spaciousness or liveliness to the sound.

My logic works like this. This spaciousness has to come from somewhere. That somewhere is the room in the form of reflections. Now if you allow reflections early (<20ms or so), you may get spaciousness, but it would be at the expense of imaging, for the direct sound + those 1st 20ms or so are critical to image detail. So in order to preserve image detail, you have to have those reflections needed for spaciousness arrive later.

Last edited by jim1961; 18th April 2012 at 06:01 PM. Reason: syntax
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Old 18th April 2012, 06:32 PM   #115
gedlee is offline gedlee  United States
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You are getting off track. We were talking about what is the right thing to measure NOT what creates image and what creates spaciousness. I never said anything about how to tradeoff image for spaciousness, thats a different topic. Only that if you want to talk about "imaging" then you need better resolution at < 10 ms. and you need to plot the criteria on that plot as it is shown in your plot. What you posted completly ellimiantes what is important for imaging. It will capture spacisouness sure, but not imaging.
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Old 18th April 2012, 07:02 PM   #116
jim1961 is offline jim1961  United States
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Originally Posted by gedlee View Post
You are getting off track. We were talking about what is the right thing to measure NOT what creates image and what creates spaciousness. I never said anything about how to tradeoff image for spaciousness, thats a different topic. Only that if you want to talk about "imaging" then you need better resolution at < 10 ms. and you need to plot the criteria on that plot as it is shown in your plot. What you posted completly ellimiantes what is important for imaging. It will capture spacisouness sure, but not imaging.
I thought soundstage was as relevant to the discussion as imaging given that many people either mean the same thing by both words, confuse their meaning or consider them both equally important.

Looking at the graph I presented, it seems to me the <10ms data is fairly clear. That first vertical divider is about 8ms. The only filter is what I said earlier, a .33 octave response centered at 1200hz measured at the listening position. I have the plots of the other frequencies, but I posted that one for illustration purposes, not to try to convey the entirety of my room response.

In addressing directly what you said. I dont have a saved impulse response. Nor do I have an ETC of just the data to 10ms.

Last edited by jim1961; 18th April 2012 at 07:03 PM. Reason: syntax
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Old 18th April 2012, 07:52 PM   #117
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Jim, I think you are on the right track and I like the fact that you are taking a more systematic approach to this when compared to what others are doing. You are to be congratulated.

If you are not already familiar with it, you should look up the concept of the "Haas kicker". Don Davis uses the term in his work (eg, his handbook) although I don't know if the term is original to him. I won't try and define it in 25 words or less on an internet forum, but it touches on some of the issues you are dealing with in terms of "spaciousness" and the positive and negative role of echoes
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Old 18th April 2012, 08:21 PM   #118
gedlee is offline gedlee  United States
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Originally Posted by jim1961 View Post
I thought soundstage was as relevant to the discussion as imaging given that many people either mean the same thing by both words, confuse their meaning or consider them both equally important.
This is why I objected to the term. If it does not have a clear meaning that one can associate with the literature then of course it is going to be confusing. Its confusing to me. "Imaging" (or source localization) and "spaciousness" are terms that one can find in well regraded texts and papers. "Soundstage" is not such a word. It sounds more audiophile than psychoacoustic.

And I too will agree that what you are doing is a lot better than other approaches that I have seen. I am only trying to suggest improvements in time resolution at the lower times might help to make a better description.

Room Impulse responses are very easy to get with a free piece of software like HolmImpulse, so not having one should not be a limitation.
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Old 18th April 2012, 08:26 PM   #119
jim1961 is offline jim1961  United States
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Originally Posted by WithTarragon View Post
Jim, I think you are on the right track and I like the fact that you are taking a more systematic approach to this when compared to what others are doing. You are to be congratulated.

If you are not already familiar with it, you should look up the concept of the "Haas kicker". Don Davis uses the term in his work (eg, his handbook) although I don't know if the term is original to him. I won't try and define it in 25 words or less on an internet forum, but it touches on some of the issues you are dealing with in terms of "spaciousness" and the positive and negative role of echoes
Actually, I have heard of and at least have a working idea of what it is. For others, a oversimplification of a Haas kicker as I understand it, is basically to re-introduce the signal back into the listening environment in a delayed fashion. Thus avoiding competing with the direct signal along with flexibility as to when and how much to introduce.
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Old 18th April 2012, 08:45 PM   #120
jim1961 is offline jim1961  United States
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In the near future, I intend to work with impulse response more in depth. Right now, my system is completely down while my speakers are getting modified. Once done, I want to synchronize the impulse (timing) of the drivers. That is to say, work on getting the sound from each driver (direct response) to arrive at the ears as closely as possible to the same time.

One idea I am going to try is leaning the speaker. Ok, this requires explanation. Typically, in a 3 way (tweet, mid, woofer) the tweeter output arrives first, then the mid, then the woofer. Now if you have the driver alignment as such whereby the tweet is at the top, the mid in the middle and the woofer at the bottom, you can now imagine that by leaning the speaker back, with the midrange as the pivot point, you can effectively make the tweet further away while at the same time making the woofer closer to you. This, while perhaps not making things perfect, closes the gap between the timing of the tweeter and the woofer which are the farthest apart in terms of timing in typical situations. I realize this isnt a new idea and I am not presenting it as such. But it is something anyone can do, and costs nothing. Even if you dont have software/mics to measure the impulse responses, you can do some simple geometry by taking into account the relative voice coil locations in each driver and trying to get their distance relatively equal relative to the listening position. It may even be worth making the tweet further away from the woofer given a woofers relative slowness in response compared to most tweeters. I dont know how much benefit I will gain by this until I do it. But I think it holds some promise.

Last edited by jim1961; 18th April 2012 at 08:48 PM. Reason: added thoughts
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