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Old 31st December 2013, 05:56 PM   #10911
bappe is offline bappe  Sweden
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Quote:
Originally Posted by Jay View Post
What do you mean her?
If it's in the recording, of course I want to hear it, regardless of soom size! I just tired to say that room acoustics should be fairly consistent with the visiuals.

/Anders
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Old 31st December 2013, 06:12 PM   #10912
mitchba is offline mitchba  Canada
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As an ex recording/mixing engineer, most of my time was spent in control rooms where the early reflections were suppressed and the later reflections were diffused. The primary reason was due to the Haas effect. One can hear over headphones what this sound like in this YouTube demonstration.

While the demonstration is to be listened over headphones and is on the mixing side of music production, it does demonstrate if early reflections are high in level (like specular reflections) and in the 0 to 10 millisecond range, how it can fool your ears from a localization perspective. In other words, strong early reflections mask the localization cues that are on the recording.

One of David Greisinger’s most excellent contributions is the objective measure of Interaural Coherence Coefficient (IACC). This is the measure of spaciousness of concert halls. The smaller the IACC value, the more spaciousness. An enterprising mathematician, Dr. Uli Brueggemann, uses IACC in the opposite direction, which is a measure of channel and room reflection equality for the first 80 milliseconds of sound travel. If interested, check out: Advanced Acourate Digital XO Time Alignment Driver Linearization Walkthrough.

See attached EBU 3276. While this is an old paper, I would say it is still valuable guidance for folks wishing to set up their listening environments for critical listening. There are basic guidelines for stereo setup, early reflections, target frequency response, reverb time, etc. Speaking of RT 60, attached is the simulated frequency response and reverberation time of my critical listening environment, as per EBU 3276 guidelines.

Hope that helps and Happy New Year!
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File Type: jpg RT60.JPG (223.8 KB, 565 views)
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File Type: pdf tech3276.pdf (53.3 KB, 24 views)
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Old 31st December 2013, 08:51 PM   #10913
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Yes it does help, thank you and a Happy New Year back at ya!
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Old 1st January 2014, 02:19 AM   #10914
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Quote:
Originally Posted by Tom Danley View Post
Hi Bob


If you make a recording of the loudspeaker, play it back and re-record it, everything that was wrong before will stand out much more strongly as “wrong”.
In that generation loss recording at work, it was very rare to have a loudspeaker go even 3 generations before being unlistenable or close to it, that’s how far they are from signal faithful, even if you do I on a tower and just record the loudspeakers output.
Often enough, just listening live via microphone was enough to hear what was going to stand out on generation one on the more colored speakers. With modern 24/96 recorders, it is possible to do that many generations in/out before it’s degraded.
Loudspeakers ARE still the weak link and that makes them fun to work on i think.
Best,
Tom
A while back I found on the web where someone had done that and posted the results for listening. It did get real bad within a few generations. He was recording the sound of the speakers in a listening room, it wasn't just the speakers. I haven't heard of anyone doing it with the speaker mounted on an infinite baffle wall of an anechoic chamber. Then the results could be argued to be just the speaker without any room effects.
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Old 1st January 2014, 02:43 AM   #10915
soongsc is offline soongsc  Taiwan
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I think Tom pointed out some very interesting issues and references. It may be possible to do some analysis and simulation.

Diffraction strength and spectrum vs direct radiated strength and spectrum. The lower diffraction in respect with direct radiation will yield better performance. This varies with distance. Also the higher directivity will result in lower relative diffraction.

If you prefer to do measurements, you can start doing near field or in horn measurements gradually moving the mic out one cm at a time and see how the response varies until the response is the same within 2db of the 1M measurement. Generally, the less difference throughout the process means better performance.
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Old 1st January 2014, 03:00 AM   #10916
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Tom Danley View Post
Loudspeakers ARE still the weak link and that makes them fun to work on i think.
IMO, if speakers are the weak link, AND it is not understood, there will be a domino effect, a mess. Why speaker distortion test is not a standard?
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Old 1st January 2014, 02:54 PM   #10917
Pano is offline Pano  United States
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Quote:
Originally Posted by Bob Richards View Post
He was recording the sound of the speakers in a listening room, it wasn't just the speakers. I haven't heard of anyone doing it with the speaker mounted on an infinite baffle wall of an anechoic chamber.
Hey Bob, there was a famous test done in Finland - but I can't remember the name - that did basically that. As I remember it was just one pass A/B with speaker and mic, or the direct signal. Don't know if they ever did multiple generations.

Someone here will remember the name of the test.

Happy New Year 2014!
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Old 2nd January 2014, 02:02 PM   #10918
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Hi Pano, It is sometimes called "The Gradient test/experiment". Gradient being the name of a Finnish speaker manufacturer.

In an anechoic chamber we have loudspeakers and a high quality microphone on axis in front of them. Outside of the chamber we have a music source, an amplifier to feed the speaker(s) in the chamber and another to feed external speaker(s).

We have a switch that allows us to listen to the source or the microphone output. Lo and behold, with half decent speakers there is not a lot of difference to be heard.

The conclusion to be drawn is that much of what we hear in a normal room is reflected energy, and if directivity is out of control this experiment reminds us that the consequences can be rather detrimental.

Keith
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Old 2nd January 2014, 03:43 PM   #10919
gedlee is offline gedlee  United States
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Quote:
Originally Posted by Jay View Post
Why speaker distortion test is not a standard?
Because everyone who has looked at this factor has found that it is not important. It does not correlate with the sound quality that is perceived so why measure it, let alone standardize on a pointless measurement.
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Old 2nd January 2014, 03:45 PM   #10920
gedlee is offline gedlee  United States
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Originally Posted by Keith Taylor View Post
The conclusion to be drawn is that much of what we hear in a normal room is reflected energy, and if directivity is out of control this experiment reminds us that the consequences can be rather detrimental.

Keith
Another simple test is to have someone walk across the room between you and the speakers while your eyes are closed. It will be hard to tell where they are. If the direct sound were all-important, the walker location would be obvious at all times.
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