? 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.
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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.
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.
The sound stage can extend beyond the speaker locations only if crosstalk is reduced and/or additional binaural cues are provided.
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.
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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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.
Holmimpulse does do IRs that are time correct as long as you keep the source alive and turn off the auto zero function.
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.
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?
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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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.
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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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.
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.
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