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Old 19th October 2012, 03:59 PM   #541
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Without comment. Impulse response at my listning position.

Craw monopole- front driver only:

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Monopole both sources connected:

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CRAW, dipole mode:

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CRAW, cardioid mode:

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Old 19th October 2012, 04:02 PM   #542
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John

Sorry for the confusion but I thought you would post the actual impulse response files as sound files.
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Old 19th October 2012, 04:41 PM   #543
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Quote:
Originally Posted by Barleywater View Post
Markus:

In post #530

What are microphone distances?
It's all explained at Comparison of different near field subwoofer configurations

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Originally Posted by Barleywater View Post
Windowing for spectrograms is too large and 30dB range is too small; can't get much from this view.
The spectrogram is supposed to show in-room low frequency modal ringing. As always the window time is a tradeoff between frequency and time resolution. I doubt 300ms is too long for what I wanted to show.
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Old 19th October 2012, 04:54 PM   #544
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I can save data fro ATRT as I do not have a registered copy. My W95 PC is not working so I can't use the IMP. So pictures are the best I can do at the moment. The thing the struck me was that with the mono, connecting the rear source, which is 18" behind the front source, seems the make the impulse ring on much longer, not to mention the apparent dead spot right after the initial spike which is then followed by a broad up spike.
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Old 19th October 2012, 05:02 PM   #545
gedlee is offline gedlee  United States
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Originally Posted by markus76 View Post
I'm wondering how the source-to-sink principle could be exploited more by taking lots of measurements within a room and placing/processing sources accordingly.
My software can use up to six room locations and I suggest at least three, but more is better. The sources cannot be moved about once the data has been taken, but the processing can change. In the end it creates a situation where if you turn off one source, you will in general see both an increase and a decrease in different parts of the spectrum. This means that this sub is both sourcing and sinking. In general I find that when a good setup is obtained that all sources act as sources and sinks in different frequency ranges. To me this has a certain appeal to it.

Early next year I am on hook to do a presentation on using multiple subs to the lcal audio group. I will be doing and documenting the whole procedure in my room and I can probably post all this once I have it. I hope to do it over the holidays because between now and then I am swamped.
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Old 19th October 2012, 05:22 PM   #546
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Originally Posted by gedlee View Post
As far as the Greisinger comments go, I have trouble with the fact that a 100 Hz tone has a ten foot wavelength and we are supposed to somehow believe that a reasonable "gradient" can be achived between the ears? At 20 Hz the wavelength is 50 feet. Come on, the signal at the two ears at these frequencies has to be extremely similar if not identical. The correlation has to be nearly 1.0.

Dave: 6 dB addition of SPL is the exact same as a 3 dB addition to PWL. Multiple subs could be an issue if the structure is not very solid because there can be a lot of structure borne sound due to the heavy subs coupling to the structure. AT LFs sound issolation becomes a seriously complex problem of coupled modes and structure borne sound. In this regard a dipole would fair far worse since its mechanical forces generate far less SPL than a monopole, so structurally they would generate a lot more LF coupling. Maybe this is what makes them sound different!?
Depends on source spacing. I was thinking of two woofers well spaced giving double the power (+3dB) but double the pressure for a listener equal distance to both. No different than dual mids in an array giving +6 on axis but +3 for random phase summing (or a 3dB increase in d.i).

I realize woofers tend to be close relative to the wavelengths but if they are well spaced you may get a benefit towards the top of the range.

As to structural borne bass, that is hard to calculate. My comments were for air borne using the standard room acoustics approach. Structural borne is easy to deal with in terms of compliant feet. Do we know that it is ever a bigger factor than acoustical coupling from room to room?

I'd have to think about dipole vs. monopole with regard to vibration. I would guess the other way, that a dipole, that has to accelerate the woofer more for a given far field SPL, would tend to cause more adjacent vibration, but its not good to generalize too far.

Certainly, in a free field you are correct about nil difference between ears at bass frequencies (both for amplitude or phase). I believe Griesinger is strictly talking about in-room cases with differential between ears coming from proximity to standing wave nulls.

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David S.
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Old 19th October 2012, 06:20 PM   #547
gedlee is offline gedlee  United States
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Originally Posted by speaker dave View Post
As to structural borne bass, that is hard to calculate. My comments were for air borne using the standard room acoustics approach. Structural borne is easy to deal with in terms of compliant feet. Do we know that it is ever a bigger factor than acoustical coupling from room to room?
For home situation I don't have much experience, but for cars I have a lot and in cars structural borne is a big deal - on par with airborne in some situations. In buildings I know that it is also a factor. That leads me to believe that it should not be overlooked. But yes, I completely agree that putting the sub on resiliant feet is a big step in the right direction and I do this for all my subs, but I don't think that it is the norm.

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I'd have to think about dipole vs. monopole with regard to vibration. I would guess the other way, that a dipole, that has to accelerate the woofer more for a given far field SPL, would tend to cause more adjacent vibration, but its not good to generalize too far.
Regards,
David S.
But isn't this what I said as well? That the dipole would have the greater mechanical force to its foundation.

Example of structure borne problem: I have an air-to-air heat exchanger on my HVAC system. When I rigidly mounted it to the house structure it made lots of noise (just two fans which are supposed to be balanced so where is the vibration coming from?). Then I suspended the entire unit from nylon cord - my first cut solution to all problems like this! - and the noise simply disappeared. A large sub cannot be much different than this system in terms of its size, weight and vibration force.

I still have a lot of problems with "LF localization". I keep going back to Blauert where all of his data stops at 250-500 Hz and is dropping below that. Obviously he never even consider LFs to have any localization and yet its talked about here as if its some kind of "known fact". I just don't see that at all. Even if there is "more LF localization than has been assumed in the past", it was assumed to be zero, so even "more" is still pretty insignificant. That it cannot be even comparable to frequencies above 500 Hz is clearly the case, but I have not seen any data that shows what it actually is in a small room where all sounds are basically steady state, all sources are basically close and highly correlated. I'm just not buying "LF localization" as a factor. It is proably artifacts > 250 Hz that are being detected.

Last edited by gedlee; 19th October 2012 at 06:28 PM.
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Old 19th October 2012, 06:59 PM   #548
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Originally Posted by gedlee View Post

But isn't this what I said as well? That the dipole would have the greater mechanical force to its foundation.
Indeed, I read it backwards.

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I still have a lot of problems with "LF localization". I keep going back to Blauert where all of his data stops at 250-500 Hz and is dropping below that. Obviously he never even consider LFs to have any localization and yet its talked about here as if its some kind of "known fact". I just don't see that at all. Even if there is "more LF localization than has been assumed in the past", it was assumed to be zero, so even "more" is still pretty insignificant. That it cannot be even comparable to frequencies above 500 Hz is clearly the case, but I have not seen any data that shows what it actually is in a small room where all sounds are basically steady state, all sources are basically close and highly correlated. I'm just not buying "LF localization" as a factor. It is proably artifacts > 250 Hz that are being detected.
I don't think that Griesinger is talking about localization as we would think about it. In fact he is looking for the opposite. He wants rapid variation in the presentation to the ears to give a sense of envelopment.

This is a bit as we got into some pages back. Everyone else is pursuing some version of accuracy while he is actually going for less accuracy but a more pleasant since of involvement. His concert hall papers are following a similar vein arguing that engagement should be the primary design objective:

http://www.davidgriesinger.com/direct_sound.ppt
http://www.davidgriesinger.com/

Unconventional but worth thinking about.

David S.
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Old 19th October 2012, 07:16 PM   #549
ScottG is offline ScottG  United States
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Quote:
Originally Posted by speaker dave View Post

I don't think that Griesinger is talking about localization as we would think about it. In fact he is looking for the opposite. He wants rapid variation in the presentation to the ears to give a sense of envelopment.

This is a bit as we got into some pages back. Everyone else is pursuing some version of accuracy while he is actually going for less accuracy but a more pleasant since of involvement. His concert hall papers are following a similar vein arguing that engagement should be the primary design objective:

http://www.davidgriesinger.com/direct_sound.ppt
http://www.davidgriesinger.com/

Unconventional but worth thinking about.

David S.

Indeed.

You can read that paper several times, and while it "reads" pretty well - it's difficult to truly understand, often presenting a slightly different perspective on each reading.


He needs a better editor (..or you know, one at all).
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Old 19th October 2012, 08:49 PM   #550
gedlee is offline gedlee  United States
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Originally Posted by speaker dave View Post
I don't think that Griesinger is talking about localization as we would think about it. In fact he is looking for the opposite. He wants rapid variation in the presentation to the ears to give a sense of envelopment.
I would propose that in a small room, much as this completely disagrees with my approach above Fs, I am not sure that direct accuracy is warranted either. That is because a small room deviates so much from any room that one would ever listen to music in. So a direct one-to-one accuracy would not necessarily be what I would be looking for at these frequencies. It's at LFs that we need to "hide the room" and "trick our senses" because otherwise it just does not sound right. Again, thats because it is not right, its a small room not a large one. I use heavy EQ < Fs, and none above, I suggest heavy damping < Fs and very low amounts above. Its simply a completely different situation and has to be dealt with completely different. This is why I am not convinced that the shortest impulse response is desirable at LFs. What's the justification? More reverb at LFs would yield a greater IACC than a shorter impulse because reverberation tends towards uncorrelated sound.

I glanced through the Greisinger paper and found it quite compelling. He is saying much of the same things that I have been saying, that localization is the key to envelopment, that this is dominated at frequencies > 700 Hz, etc. etc. I never did read anywhere where these ideas had any implications for LF sound, but I didn't read it all. It is hard to read because it is not a paper, but notes from a presentation. He also seemed to be refering more to concert halls than small room reproduction systems. But what I did read I did not disagree with at all. It was completely parallel to what I have been saying and doing and I found his term "envelopment" to encompass precisely what I am looking for in a sound system. I might start using this term!! I like it! "Waveguides create Envelopment"! Cool!

Last edited by gedlee; 19th October 2012 at 09:01 PM.
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