Interesting thread. Doppler distortion?
Saw this on a review of Loth-X Ambience Loudspeakers by a Ross Mantle.
"During playback through a regular multi-way speaker, the high frequencies are separated from the low frequencies by means of a crossover, and these small Doppler frequency shifts will be passed on to the listener as distortion. A full-range driver, on the other hand, should move in an exact mirror image of the movements of the microphone diaphragm, so that the Doppler shifts inherent in the recording are cancelled out by a reverse Doppler effect at the driver."
If you change the polarity of the speakers the effect would be either additive or subtractive. Is this what people hear?
Saw this on a review of Loth-X Ambience Loudspeakers by a Ross Mantle.
"During playback through a regular multi-way speaker, the high frequencies are separated from the low frequencies by means of a crossover, and these small Doppler frequency shifts will be passed on to the listener as distortion. A full-range driver, on the other hand, should move in an exact mirror image of the movements of the microphone diaphragm, so that the Doppler shifts inherent in the recording are cancelled out by a reverse Doppler effect at the driver."
If you change the polarity of the speakers the effect would be either additive or subtractive. Is this what people hear?
It's hard to say whether the difference we hear is the dopple effect or not. Is there any information explaining what frequency difference and how much driver travel will produce doppler effects that may be audible?
Hi, here is the URL of the article I quoted:
http://www.ultraaudio.com/equipment/lothx_ambience.htm
I was intrigued as I had never come across that theory before.
I don't know if it holds water in real life, as there is no scientific data.
I have not heard absolute phase on my systems but believe that others must be hearing something even if it is subtle.
Cheers
http://www.ultraaudio.com/equipment/lothx_ambience.htm
I was intrigued as I had never come across that theory before.
I don't know if it holds water in real life, as there is no scientific data.
I have not heard absolute phase on my systems but believe that others must be hearing something even if it is subtle.
Cheers
I have experienced the same thing as explained in that article. I think it may not be due to doopler effect because. In my recent experience in tweaking drivers, there are a few things that I noticed. The better fidelity the more difference in between the different absolute polarities. Recording that go though too much processing also reduces the possibility of hearing the difference between the different polarites (lot of XRCDs are like this). There are other factors that probably would have a greater effect than the doppler effect.
1. Residual energy in the drivers.
2. Non-transient perfect design.
3. Resonances caused by enclosures.
I would use the reverse polarity test as a basic test of fidelity check.
1. Residual energy in the drivers.
2. Non-transient perfect design.
3. Resonances caused by enclosures.
I would use the reverse polarity test as a basic test of fidelity check.
I agree that the 3 points you made would have a bigger effect on a speaker's sound than the doppler distortion. Klipsch made a big thing of doppler distortion referring to it as "mud" in the sound, but he was trying to sell horns and they have less diaphram movement thus less doppler distortion.
I have mucked about with multiway speakers for years but never been happy, hence my interest in single driver speakers. I have some drivers on order. I may be able to hear this absolute phase effect at home.
What are you doing to drivers?
I have mucked about with multiway speakers for years but never been happy, hence my interest in single driver speakers. I have some drivers on order. I may be able to hear this absolute phase effect at home.
What are you doing to drivers?
There are 3 areas that are easy to play with, all involving reducing resonances. Mainly cone resonance, cavity resonance, and spider resonance. I'm sure it is also possible to get good results with multi-way speakers. Each driver just needs to perform well wider than it's XOed range. One person commented on one of my mods indicating is was a bit slow, which I later attributed to passive componenets in the speaker.
soongsc
Good to hear someone is trying to make better drivers.
Apart from resonances there is also the reflected energy from the magnet structure at highish freqs which Vandersteen has tackled. I like the sound of his speakers in the midrange/treble.
After looking at this quoted by komen earlier
http://www.st-and.demon.co.uk/AudioMisc/asymmetry/asym.html
There must be something very wrong with today's systems if we cannot hear this.
Good to hear someone is trying to make better drivers.
Apart from resonances there is also the reflected energy from the magnet structure at highish freqs which Vandersteen has tackled. I like the sound of his speakers in the midrange/treble.
After looking at this quoted by komen earlier
http://www.st-and.demon.co.uk/AudioMisc/asymmetry/asym.html
There must be something very wrong with today's systems if we cannot hear this.
I have not read any information about reflected energy in the magnet structure, is this flux modulation? I know lots of drivers use shorting rings, but somwhow those seem to have some adverse effect on the mid and high frequencies. Probably that's why they are mostly used in woofers. If you have any information on what the reflected energy is, I would be interested in exploring it.
Asymetry in audio signals are more evident in sudio recordings. I was listening to some old recordings made in studios and with little sound processing technology, the difference in polarity is much more significant than newer recordings. It must have somthing to do with synthetically adding room reverberation into the music. In properly recorded live performances, the polarity is also audible, but not as much as the old studio recordings.
Asymetry in audio signals are more evident in sudio recordings. I was listening to some old recordings made in studios and with little sound processing technology, the difference in polarity is much more significant than newer recordings. It must have somthing to do with synthetically adding room reverberation into the music. In properly recorded live performances, the polarity is also audible, but not as much as the old studio recordings.
fredex said:
You can argue even better the other way around:
"During playback through a regular multi-way speaker, the high
frequencies are separated from the low frequencies by means of a
crossover, and because the tweeter membrane is not moved forth
and back by half an inch of bass excursion, there is no bass Doppler on the treble.
The membrane of a full-range driver, on the other hand, must
move forth and back nearly half an inch to provide the required
SPL at 30 Hz, thusly constantly dislocating the source of treble.
Since one would seriously hope that the diaphragm of the
microphone is never ever moved by the sound source for
half an inch, there is absolutely no hope for Doppler cancelation."
Gerhard
fredex said:
I investigated Vandersteen's point of view at this site
http://www.soundstage.com/interviews/int07part2.htm
and think he has a point worth looking into to see how large the magnet needs to get for it to have effects. Right now I have only focused on parts mechanically in tact with the cone. Results are measureable as well as audible. I think B&W also does some analysis on a similar issue that caused them to shape the higher frequency enclosures the way they do.
Gerhard
I think Ross Mantle is saying is that the doppler distortion is already encoded in the recorded signal and a multiway speaker just reproduces this accurately whereas a single driver because it creates its own doppler distortion has the potential [if the polarity is correct] to 'cancel' out this doppler distortion in the recorded signal.
Although this idea appears OK. I can only see it happening if just one mic is used to record the music, today you would have a separate mics for the bass bass drum etc
Soongsc
Yeah the reflections are acoustic off the magnet and basket structure, same as the back wave from the rear cabinet wall. I believe Vandersteen physically moves the magnet back from the cone so the effect happens a little later. Reducing "smear" or loss of "detail". I read that somewhere, I have not seen inside his midrange driver.
I think Ross Mantle is saying is that the doppler distortion is already encoded in the recorded signal and a multiway speaker just reproduces this accurately whereas a single driver because it creates its own doppler distortion has the potential [if the polarity is correct] to 'cancel' out this doppler distortion in the recorded signal.
Although this idea appears OK. I can only see it happening if just one mic is used to record the music, today you would have a separate mics for the bass bass drum etc
Soongsc
Yeah the reflections are acoustic off the magnet and basket structure, same as the back wave from the rear cabinet wall. I believe Vandersteen physically moves the magnet back from the cone so the effect happens a little later. Reducing "smear" or loss of "detail". I read that somewhere, I have not seen inside his midrange driver.
posted by Gerhard
If it can't then there is no distortion to cancel out.
You have got me thinking now, can a microphone actually create doppler distortion if it only moves a small amount ?
If it can't then there is no distortion to cancel out.
Trying to make better drivers
soongsc
Good to hear someone is trying to make better drivers.
Apart from resonances there is also the reflected energy from the magnet structure at highish freqs which Vandersteen has tackled. I like the sound of his speakers in the midrange/treble.
After looking at this quoted by komen earlier
http://www.st-and.demon.co.uk/Audio...metry/asym.html
There must be something very wrong with today's systems if we cannot hear this.
Also check out Von Schweikert as well www.vonschweikert.com(Technical Design Overview)
soongsc
Good to hear someone is trying to make better drivers.
Apart from resonances there is also the reflected energy from the magnet structure at highish freqs which Vandersteen has tackled. I like the sound of his speakers in the midrange/treble.
After looking at this quoted by komen earlier
http://www.st-and.demon.co.uk/Audio...metry/asym.html
There must be something very wrong with today's systems if we cannot hear this.
Also check out Von Schweikert as well www.vonschweikert.com(Technical Design Overview)
Link should be:
http://www.st-and.demon.co.uk/AudioMisc/asymmetry/asym.html
and
http://www.vonschweikert.com/about.html (=Technical Design Overview)
http://www.st-and.demon.co.uk/AudioMisc/asymmetry/asym.html
and
http://www.vonschweikert.com/about.html (=Technical Design Overview)
Re: Trying to make better drivers
Recently doing some study, I discovered that lots of energy in the cavity under the VC cap between the magnet structure. Depending on the dimensions, these seem to start as low as 1KHz up to watever can be measured. If the caps are not absorptive, then much energy is also rediated back out of the cap.
I love the coherence of wide range drivers, which is most ideal in small rooms. trying out some MTM designs made me convinced that for two drivers to cover the same frequency range, the drivers would need to be precisely matched dynamically. In a design that I tried, two woofers each in their own enclosure, I could hear what normally should be one drum beat come at as two beats.
No matter what the analysis say, with XO design showing good phase response, if the drivers are connected out of phase from each other, then one polarity, I hear high frequency transients correct, but muffles (slow) bass, the other polarity around, the bass is good but not the high frequency transients.
heilman said:
Recently doing some study, I discovered that lots of energy in the cavity under the VC cap between the magnet structure. Depending on the dimensions, these seem to start as low as 1KHz up to watever can be measured. If the caps are not absorptive, then much energy is also rediated back out of the cap.
I love the coherence of wide range drivers, which is most ideal in small rooms. trying out some MTM designs made me convinced that for two drivers to cover the same frequency range, the drivers would need to be precisely matched dynamically. In a design that I tried, two woofers each in their own enclosure, I could hear what normally should be one drum beat come at as two beats.
No matter what the analysis say, with XO design showing good phase response, if the drivers are connected out of phase from each other, then one polarity, I hear high frequency transients correct, but muffles (slow) bass, the other polarity around, the bass is good but not the high frequency transients.
This 135 post thread is about absolute phase.
Your comments seem a bit far from that. Every person that participated in the Absolute Phase thread will now get a link to your comments.
Perhaps you should think about starting a new thread more in line with your comments (just a thought).
Your comments seem a bit far from that. Every person that participated in the Absolute Phase thread will now get a link to your comments.
Perhaps you should think about starting a new thread more in line with your comments (just a thought).
djk said:
The beginning of this thread is absolute phase in the sense of "absolute polarity" which is less confusing terminology. Even absolute polarity in each drivers of speaker system makes a difference. Something to try and experience.
As said in the beginning, this is very mixed up with another thread concerning Absolute Polarity. I am not certain that that is not the real issue here; after all I cannot see an absolute phase (compared to what?) issue as compared to absolute polarity.
But I must unfortunately react to some extremely sweeping statements made here earlier - not about the subject - sincere apologies, but enough is enough.
Firstly, Mr Rollins, I am sad that you seem to judge Douglas Self only by perhaps his worst moment "making a complete fool of himself (otherwise)..."? Is that the sum total of your impression of him? Then, with all respect, you do appear to be in a very small and opinionated minority! (I could continue and be witty and say that if you are later surprised to be compared to him, where does that put you? - either quite smarter than him, or ...?) But I will leave it at that; it is just that blanket statements like that and behind someone's back ....
Then:
To you I will be extremely kind and just respectfully say that audio technology and background do not appear to be your forte - sorry.
Firstly, once again (ad nausiam) the weary old bleat that your ears are right (checked how), and those who do not agree with you are simply deaf, stupid, whatever. And there are as yet undiscovered things about hearing. QED.
Scientists do not know everything, but they do know certain things. They have designed Boeings, race cars, put a man on the moon. Who should one rather trust, those "ignorant" scientists, or a minority of people who have absolute (subjective) faith in their own abilities - only?
Let me simply sum up the state-of-affairs regarding established audio technology:
1. All audible defects in amplifiers can be verified by the right measurements.
2. "Hearing" has been qualified and quantified in many of tests (noticably at Scandenavian universities) and has been published. Self has simply not re-investigated those because it has all been done.
3. Many effects "sworn to" by "golden ears" could suddenly no longer be detected in blind tests the next moment. This is also getting boring. Again: It has been done, dear sir!
So nobody is saying (also not Douglas Self) that the ear is no judge per se, only that it is subjective and can be bluffed - this again is the conclusion from numerous tests of numerous subjects (Again: Has been done!) But if you read objectively, you would have noticed that Self mostly objected to those objecting with some arrogance to the "sin" that science would not accept that 3+5=11, because they claimed it to be so
Please my friend!
I design amplifiers, all of which have been accepted with acclaim by others (not my ears!), and I do it by measurements. So either I must be the luckiest person the past 50 years - or I must be doing something right!
(Despite this, perhaps you could console yourself with the recent finding by mathematicians that 2 + 2 can =5 .... for very large values of 2. 🙂 🙂 🙂 )
Regards, and back to the subject.
(Edited: Spelling)
But I must unfortunately react to some extremely sweeping statements made here earlier - not about the subject - sincere apologies, but enough is enough.
Firstly, Mr Rollins, I am sad that you seem to judge Douglas Self only by perhaps his worst moment "making a complete fool of himself (otherwise)..."? Is that the sum total of your impression of him? Then, with all respect, you do appear to be in a very small and opinionated minority! (I could continue and be witty and say that if you are later surprised to be compared to him, where does that put you? - either quite smarter than him, or ...?) But I will leave it at that; it is just that blanket statements like that and behind someone's back ....
Then:
djk said:
To you I will be extremely kind and just respectfully say that audio technology and background do not appear to be your forte - sorry.
Firstly, once again (ad nausiam) the weary old bleat that your ears are right (checked how), and those who do not agree with you are simply deaf, stupid, whatever. And there are as yet undiscovered things about hearing. QED.
Scientists do not know everything, but they do know certain things. They have designed Boeings, race cars, put a man on the moon. Who should one rather trust, those "ignorant" scientists, or a minority of people who have absolute (subjective) faith in their own abilities - only?
Let me simply sum up the state-of-affairs regarding established audio technology:
1. All audible defects in amplifiers can be verified by the right measurements.
2. "Hearing" has been qualified and quantified in many of tests (noticably at Scandenavian universities) and has been published. Self has simply not re-investigated those because it has all been done.
3. Many effects "sworn to" by "golden ears" could suddenly no longer be detected in blind tests the next moment. This is also getting boring. Again: It has been done, dear sir!
So nobody is saying (also not Douglas Self) that the ear is no judge per se, only that it is subjective and can be bluffed - this again is the conclusion from numerous tests of numerous subjects (Again: Has been done!) But if you read objectively, you would have noticed that Self mostly objected to those objecting with some arrogance to the "sin" that science would not accept that 3+5=11, because they claimed it to be so
Please my friend!
I design amplifiers, all of which have been accepted with acclaim by others (not my ears!), and I do it by measurements. So either I must be the luckiest person the past 50 years - or I must be doing something right!
(Despite this, perhaps you could console yourself with the recent finding by mathematicians that 2 + 2 can =5 .... for very large values of 2. 🙂 🙂 🙂 )
Regards, and back to the subject.
(Edited: Spelling)
fredex said:
Not sure if I picked up all of the posts on Doppler - rather late here! - but Doppler distortion is dependant on the product of thefrequency of the high frequency source and the amplitude of the low frequency source. Therefore no Doppler distortion at all is likely to be generated in a microphone. I am afraid this business of concellation (if I read correctly) is not so.
Doppler distortion is audible with a full-range small driver. I am afraid that it therefore is a factor in many small long-throw woofers, depending on the frequency range it covers.
Regards.
Johan Potgieter said:
Although the subject is not related to doppler distortion, I would be interested in knowing what would it sound like for a small long throw driver (maybe 3", Xmax 3mm p-p) of 200~20KHz bandwidth sound like, and how it would be distinguished for distortion caused by other means? Then how would doopler distortion in a 6" driver with 15mm p-p Xmax and bandwidth of 50~8KHz sound? and how it would be distinguished for distortion caused by other means?
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