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Old 24th June 2013, 09:03 AM   #61
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Quote:
Originally Posted by Face View Post
Or he knows how to pick up a book.

" pertaining to a system of sound recording or reproduction using two or more separate channels to produce a more realistic effect by capturing the spatial dimensions of a performance (the location of performers as well as their acoustic surroundings), used especially with high-fidelity recordings and reproduction systems"
? That quote is probably not by Nietzsche

Two channels can hold all the information for a complete reproduction of a 360 sound field BUT two speakers present a major distortion in the transmission of that information. Furthermore most stereo recordings aren't made using binaural techniques. They are made with two speakers sitting at 30 in front of a mixing/mastering engineer.

Last edited by markus76; 24th June 2013 at 09:06 AM.
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Old 25th June 2013, 06:59 AM   #62
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by jlo View Post
You need
- two L and R outputs for playing the sweep file
- one mic input for recording

There is only one sweep file with L and then R, to be sure of the real timings between L and R, so to keep true PITD. You may use IR recorded with other softwares but you will never be sure of the timings : generally software automatically align to a certain peak of the IR.
I intend to try this software out since I have had very interesting experience in how frequency response tuning of an amplifier effects the overall sound stage and focus. However, I wonder if were possible to generate position adjusted ITD and IID signals through each channel so that you can test location from straight ahead of the listener to 60 degrees to the side, and see if this image shift is correctly reproduced.
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Old 25th June 2013, 09:30 AM   #63
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When using interchannel level/time differences only, speaker crosstalk prevents phantom sources outside the speaker triangle. Both speakers act as separate sources and the precedence effect kicks in.
The sound stage can extend beyond the speaker locations only if crosstalk is reduced and/or additional binaural cues are provided.
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Old 25th June 2013, 10:16 AM   #64
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I was thinking in terms of speaker performance only, so this is sort of reverse of moving the mic as the software was originally designed to do. The intent would be to see if there is anything in the frequency/phase response that is associated with imaging because the audible change was too obvious to ignore.
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Old 8th July 2013, 03:41 PM   #65
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by jlo View Post
You need
- two L and R outputs for playing the sweep file
- one mic input for recording

There is only one sweep file with L and then R, to be sure of the real timings between L and R, so to keep true PITD. You may use IR recorded with other softwares but you will never be sure of the timings : generally software automatically align to a certain peak of the IR.
I tried a run using notebook output and it's mic as input, but I was not sure how to connect an external mic with it"s own mic preamp because it would be a line level input. Would POPS be using both channels, left, or right? What would happen if a plugged two microphones (one in each stereo channel) and made the recording?

I tend to feel if the sweep file was made for each channel so as to create a phantom image for specific angles, then record to verify whether the playback also recreates a related phantom image location, it sort of helps link system performance with recording to ensure a design reproduces phantoms images correctly.
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Old 8th July 2013, 04:41 PM   #66
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Not all laptops allow external sources, but many do. It is usually just shown as an external microphone in.

Holmimpulse does do IRs that are time correct as long as you keep the source alive and turn off the auto zero function.
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Old 8th July 2013, 08:05 PM   #67
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Quote:
I tend to feel if the sweep file was made for each channel
There is one wav file with the two sweeps, first on left channel then on right channel, and the time between both sweeps is well defined. So you need a stereo output but you only record once. The recording contains the left response followed by the right response. This permits to analyse exact interchannel delay, channel level difference depending on frequency, interaural phase difference and interaural group delay. All those measured parameters give possibility to calculate frequency dependant ITD and ILD that give phantom image position.
As the calculation mainly relates to channel differences, the measurement is not so dependant of the output frequency response of the laptop or even of the mic performance.
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Old 8th July 2013, 11:51 PM   #68
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Jlo,

I was wondering, the internal mic of a notebook can record a different frequency and phase from each speaker, will that not effect the results? As I understand the way your software works is that the room effects on image source is also included, is this correct?
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Old 9th July 2013, 08:18 AM   #69
jlo is offline jlo  France
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Quote:
I was wondering, the internal mic of a notebook can record a different frequency and phase from each speaker
when I said any mic, I thought about an uncalibrated measurement microphone (usb umik1 or Behringer ecm8000, or equivalent...). You don't need a calibrated class 1 DPA or Earthworks, but you need a mic far at main listening position, with no reflecting surfaces nearby.
The performance of most laptops line outputs is good enough (check it with RMAA), but not the mic itself.

Quote:
As I understand the way your software works is that the room effects on image source is also included, is this correct?
Yes, room effects are also included : the measurement window is frequency dependant and more room effect is taken in lower frequencies (here you cannot separate loudspeaker from room anyway) and at higher frequencies, only early reflections are considered.
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Last edited by jlo; 9th July 2013 at 08:25 AM.
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Old 31st August 2013, 12:29 PM   #70
jlo is offline jlo  France
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Default Griesinger's LOC

POPS news : I've just added LOC calculation.
You all know David Griesinger: among other things he introduced a new measuring method called LOC, a ratio between direct sound energy and buildup energy of reflections and reverberation to give another estimation of clarity. But how does LOC relate to phantom position ? Well, POPS should estimate the frequency dependant position and LOC could estimate its precision : the higher the value of LOC, the more precise the position is defined. I have to do more tests but I thought that adding this function could give an easy way to check one of David's ideas. Visit David Griesinger's website to have more info on LOC.
Click the image to open in full size.
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Last edited by jlo; 31st August 2013 at 12:33 PM.
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