At times like this, I reach for the wisdom of G.A. Briggs!
"The maximum velocity attained by a voice coil moving 1/2" at 50 Hz is equal to only 4.45 mph. Any resultant change in pitch could not be detected by the human ear."
"The maximum velocity attained by a voice coil moving 1/2" at 50 Hz is equal to only 4.45 mph. Any resultant change in pitch could not be detected by the human ear."
Reinhold Lutz "Active Doppler Compensation" device reduces some intermodulation distortion he refers to as "Bessle lines" while increasing harmonic distortion.
No thanks, I'm not planning to buy the "Active Doppler Compensation" device to trade distortions that I wouldn't hear..
Art
See, the biggest issue in a room is actually compression distortion. What you need to have are speakers exactly opposite your current speakers, but in opposite polarity so your room doesn't suffer from these instantaneous compressions of air which then distorts the sound. These compressions are happening up to tens of thousands of times per second, and they continuously disturb the air molecules around you.
It sounds even better when you do this with Atmos.
It sounds even better when you do this with Atmos.
A perfectly linear driver with a big LF signal and a HF signal does not add "doppler" effects. This is superposition theory.
In reality air itself is non-linear and real drivers are not at all linear, so you get intermodulation.
The real effect incorrectly called "doppler" is the weakness of coaxial drivers, where the LF signal modulates the HF directivity and this can be heard.
In reality air itself is non-linear and real drivers are not at all linear, so you get intermodulation.
The real effect incorrectly called "doppler" is the weakness of coaxial drivers, where the LF signal modulates the HF directivity and this can be heard.
I experienced doppler distortion listening to heavy bass material mixed with midrange at loud levels on B&W DM-7, a small 2-way wih passive radiator for very low tuning and a huge DC blocking cap to protect the woofer below tuning resonance . They also pumped quite noticeably on warped records, but this was not audible. Doppler distortion exists, at least in small 2-way systems, and is audible depending on the low frequencies involved, the midrange instruments involved, and the amplitude of the driver excursion.
Understood. I should listen to my system in a vacuum to avoid distortions caused by those pesky molecules.
More seriously I thought this was a real thing. It seems clear to me that the effect is real, and one of the benefits of multi-way systems is to reduce this. I don't know if the effect is noticable though. The speed of a bass cone might only be a few mph, but say it's about 1% of the speed of sound then that's a 1% change in pitch, or about 17 cents. I think smearing a clean tone by this much might well be noticeable.
More seriously I thought this was a real thing. It seems clear to me that the effect is real, and one of the benefits of multi-way systems is to reduce this. I don't know if the effect is noticable though. The speed of a bass cone might only be a few mph, but say it's about 1% of the speed of sound then that's a 1% change in pitch, or about 17 cents. I think smearing a clean tone by this much might well be noticeable.
Doppler effect equation:
Observed frequency = emited frequency x (speed of sound + Speed of listener)/(speed of sound + speed of emiter)
6mm of excursion at 50hz (1.2m/s) would shift a 1000hz signal to 996.5 on the downside. So a +/- shift of 3.5hz
Observed frequency = emited frequency x (speed of sound + Speed of listener)/(speed of sound + speed of emiter)
6mm of excursion at 50hz (1.2m/s) would shift a 1000hz signal to 996.5 on the downside. So a +/- shift of 3.5hz
That's what it sounds like, a rapid flutter in the mids that follows the bass. When I had my DM-7, a friend of mine had the 801F, a 3-way with a much larger woofer. His didn't suffer doppler efects as mine did with the very same record.
Whatever causes it, it's real and audible under certain circumstances, and doppler is a fair, analogous description of it .
I seriously doubt a human can hear a 3.5hz frequency shift, and what you are hearing is highly unlikely to be doppler shift.
Intermodulation distortion is what I would assume you are hearing.
Intermodulation distortion is what I would assume you are hearing.
I think it's the same thing in this context. Sum and difference frequencies and all that.
Depends on frequency. 15 cents is a tight vibrato.
(vibrato measurement figures from this paper)
https://www.researchgate.net/public...nt_and_analysis_of_musical_vibrato_parameters
Attachments
I think even if there's not definite perception of a vibrato or clear intermodulation products, it might still have a muddying effect. I suppose someone needs to do proper science to establish if it's discernible.
Snake oil. "The only way to get rid of these disturbing additional frequencies is to use an acoustically stationary membrane." Well, that solves everything doesn't it? Of course there won't be much music.
Well with live music the tones produced by real instruments from discrete sources, so for sure they won't intermodulate in the same way. Trying to recreate that from a single membrane could well create artifacts.
That implies something is being sold. I haven't seen anything like that in this thread, only an honest enquiry into an acoustical effect which may or may not exist.
Why would the frequency shift? This I think is the big misunderstanding of so called Doppler distortion. The 1,000hz signal is still being reproduced along with the 50hz frequency, the frequencies add, and the overall waveform is the same. The difference in the article is that the two frequencies are reproduced with phase distortion added to prove the authors beliefs (and sell his magic box). It's total baloney, horse hockey, technobabble nonsense.
The AudioChiemgau ModeCompensator https://audioxpress.com/article/the-audiochiemgau-modecompensator-a-quick-basic-test
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Yep, my bad. I'll admit I didn't click the link for the article. So yes, snake oil!
You would get doppler effects if a woofer had a tweeter attached to the cone. The tweeter cone position is then modulated by the woofer position. Nobody does this.
An ideal single driver driven by two signals is in a position determined by the two signals, with the same reference point, so the sum pressure exactly tracks the drive voltage - no doppler shifts.
Cone breakup effects, which make some drivers sound very messy at times, can easily make a HF sound AM modulate with cone position due to a LF signal. This is intermodulation, not doppler.
An ideal single driver driven by two signals is in a position determined by the two signals, with the same reference point, so the sum pressure exactly tracks the drive voltage - no doppler shifts.
Cone breakup effects, which make some drivers sound very messy at times, can easily make a HF sound AM modulate with cone position due to a LF signal. This is intermodulation, not doppler.