Mr.Greg perform a simple experiment.
Take a 12" woofer in your hand and apply some strokes on its cone with your hand to get a hearing of thump . Now repeat this procedure with speaker's terminals shorted together , then you will hear the difference of the bass thump between shorted terminals and open terminal..........
The cone will vibrate more in case of open terminals whereas cone movement will be tighter and less with shorted terminals........
Open terminals clearly shows Zero damping Factor, whereas Shorted Terminals shows very large damping......
Similarly amplifier with high output impedance has less damping factor and exhibits less control on speaker cone movement , whereas amplifier with very low output impedance exhibits high damping factor and tighter control of speaker cone.
Crown Audio amplifiers have damping factors ranging from 1000 to 15000 ........ www.crownaudio.com....
Damping factor is a very important factor when obtain Very High Sound Pressure level in Low frequency region......
Take a 12" woofer in your hand and apply some strokes on its cone with your hand to get a hearing of thump . Now repeat this procedure with speaker's terminals shorted together , then you will hear the difference of the bass thump between shorted terminals and open terminal..........
The cone will vibrate more in case of open terminals whereas cone movement will be tighter and less with shorted terminals........
Open terminals clearly shows Zero damping Factor, whereas Shorted Terminals shows very large damping......
Similarly amplifier with high output impedance has less damping factor and exhibits less control on speaker cone movement , whereas amplifier with very low output impedance exhibits high damping factor and tighter control of speaker cone.
Crown Audio amplifiers have damping factors ranging from 1000 to 15000 ........ www.crownaudio.com....
Damping factor is a very important factor when obtain Very High Sound Pressure level in Low frequency region......
Workhorse said:
Simply a case of speaker coil-magnet assembly acting as a generator (with inputs shorted).....with the EMF thus generated opposing the cones motion.........
Nothing whatsoever to do with damping or lack thereof...
..........a so-called 'damping factor' of 100 or greater (i.e. output impedance=<.01) is more than sufficient...
It doesn't matter what causes it, it's still damping: Apply an impulse (manually in this case, but the result of an electrical impulse from an amplifier is the same) and the resulting waveform shows little or no ringing, i.e. it is well damped.mikeks said:
When the coil is effectively shorted by a low impedance amplifier the effect is identical. This also explains why amps with high impedance output (current amplifiers) result in Qe of the speaker tending towards infinity.
Hi mikeks,
Post #86. 'Damping a non-issue'. Is that so ?????
I cannot agree.
If the open loop bandwidth of a NFB amplifier is not flat, then the dynamic damping cannot be in phase with the sensed error.
Often in quadrature, it adds an additional hf correction error to the original input signal appearing at the amplifier's output terminal, and it produces the 'glare or bright sound' as reported by MikeB in post#79 above.
When the open loop bandwidth is flat through AF the error correction is closely in phase with signal and thus inaudible.
Something that is added is often more noticeable than something taken away.
Many folks don't understand what I have been trying to communicate about NFB amplifiers having an *internal* inductance that reacts separately in time to, and not in series with load impedance, an internal inductance that can also lead to fractional reverse commutation in class-AB.
This is the oft termed 'solid-state sound'.
It cannot be directly measured via thd analysis but can be revealed by checking an amplifier's response to a suddenly starting first cycle, no matter how incorrect such a test method might be deemed.
Hi MikeB,
The loudspeakers dynamically generate the back EMF that the amplifiers react to (often erroneously), but they (in conjunction with their connecting cable) merely reproduce the potential that the amplifier presents; good as well as bad.
Cheers ......... Graham.
Post #86. 'Damping a non-issue'. Is that so ?????
I cannot agree.
If the open loop bandwidth of a NFB amplifier is not flat, then the dynamic damping cannot be in phase with the sensed error.
Often in quadrature, it adds an additional hf correction error to the original input signal appearing at the amplifier's output terminal, and it produces the 'glare or bright sound' as reported by MikeB in post#79 above.
When the open loop bandwidth is flat through AF the error correction is closely in phase with signal and thus inaudible.
Something that is added is often more noticeable than something taken away.
Many folks don't understand what I have been trying to communicate about NFB amplifiers having an *internal* inductance that reacts separately in time to, and not in series with load impedance, an internal inductance that can also lead to fractional reverse commutation in class-AB.
This is the oft termed 'solid-state sound'.
It cannot be directly measured via thd analysis but can be revealed by checking an amplifier's response to a suddenly starting first cycle, no matter how incorrect such a test method might be deemed.
Hi MikeB,
The loudspeakers dynamically generate the back EMF that the amplifiers react to (often erroneously), but they (in conjunction with their connecting cable) merely reproduce the potential that the amplifier presents; good as well as bad.
Cheers ......... Graham.
Mikeks..... damping could not be a non issue in solid state amplifier, but in your domestic wisdom it could be.....
When the loudspeaker cone vibrates, it acts like a micro-
phone, generating a signal from its voice coil. This signal generated by the speaker is called back EMF
(back Electro Motive Force). It travels through the speaker cable back into the amplifier output, then
returns to the speaker. Since back EMF is in opposite polarity with the speaker's motion, back EMF
impedes or damps the speaker's ringing.
The smaller the amp's output impedance, the greater is the effect of back EMF on the speaker's motion.
An amplifier with low output impedance does not impede the back EMF, so the back EMF drives the loud-
speaker with a relatively strong signal that works against the speaker's motion. When the speaker cone
moves out, the back EMF pulls the speaker in, and vice versa.
The loudspeaker damps itself through the amplifier output circuitry. The lower the impedance of
that output circuitry, the more the back EMF can control the speaker's ringing.
When the loudspeaker cone vibrates, it acts like a micro-
phone, generating a signal from its voice coil. This signal generated by the speaker is called back EMF
(back Electro Motive Force). It travels through the speaker cable back into the amplifier output, then
returns to the speaker. Since back EMF is in opposite polarity with the speaker's motion, back EMF
impedes or damps the speaker's ringing.
The smaller the amp's output impedance, the greater is the effect of back EMF on the speaker's motion.
An amplifier with low output impedance does not impede the back EMF, so the back EMF drives the loud-
speaker with a relatively strong signal that works against the speaker's motion. When the speaker cone
moves out, the back EMF pulls the speaker in, and vice versa.
The loudspeaker damps itself through the amplifier output circuitry. The lower the impedance of
that output circuitry, the more the back EMF can control the speaker's ringing.
There is an interesting experiment about how audio amps reacts to signals that enter via the output terminal (not input terminal via RCA). This disturbance signal is not related to music signal that enters via RCA, the result is that the amp doesn't know which is which, and the NFB process both. Look at figure 2 at page 41 of May 2005 AudioExpress.
Hi Kanwar,
Is this your revelation?
Would a damping factor of 100 be adequate then ( i.e. Zout of 0.08 ohms) or would 1000 or 10,000 be better. Of course you will need to connect your speaker to it with superconducting wire to acquiesce to it's benefits - because it's easily achieved with, as Crown does and as I do, a chip front end.
So if we accept that 100 is all that's needed due to practical connection constraints, then please explain why it would be of benefit to have a constant damping factor vs frequency?
Mike B and Graham Maynard, my amplifiers have NO GLARE at all and they use 2pole nested feedback (huge OL gain variation). "Solid State Sound" as you put it Graham, is ABsupply commutation harmonics (to infinity) breaking through the PSRR and being re-emphasized through it's typical 6 dB/octave decline. That's it. IMHO.
Is this your revelation?
Would a damping factor of 100 be adequate then ( i.e. Zout of 0.08 ohms) or would 1000 or 10,000 be better. Of course you will need to connect your speaker to it with superconducting wire to acquiesce to it's benefits - because it's easily achieved with, as Crown does and as I do, a chip front end.
So if we accept that 100 is all that's needed due to practical connection constraints, then please explain why it would be of benefit to have a constant damping factor vs frequency?
Mike B and Graham Maynard, my amplifiers have NO GLARE at all and they use 2pole nested feedback (huge OL gain variation). "Solid State Sound" as you put it Graham, is ABsupply commutation harmonics (to infinity) breaking through the PSRR and being re-emphasized through it's typical 6 dB/octave decline. That's it. IMHO.
Hi amplifierguru,
I have not said that a damping factor of 100 is all that's needed.
Also you are informing me that reverse commutation is psu related.
Well maybe that is possible, but I am thinking of something different !
When the NFB correction within an amplifier is not in phase with the sensed error (ie. open loop gain is phase shifted within the desired activity band), then a class-AB output stage cannot be prevented from being fractionally modulated by cable/loudspeaker generated back EMF. The error voltage generated within an amplifier due to self inductance prior to output node sensing has nothing to do with a subsequent series output choke or any cable/loudspeaker.
An 8R voice coil is not going to be damped significantly differently by an additional 0.01R in series with it when compared to 0.1R, sure the cable gives that anyway !!!
But, the back EMF induced by crossover circuitry can be much more significant within the audio passband because the acting coils and capacitors seldom have series resistors at each pole filter; they are highly reactive around their crossover frequencies. Separate damping/compensation components might smooth the 'impedance' curve, but these components cannot act within the same timeframe.
The additional *voltage* output error generated by an amplifier as it attempts to damp dynamically induced back EMF *current* is directly related to damping factor multiplied by the sine of the angle of internal output stage (inductance) at the frequency of interest, not just the damping factor alone.
It is possible to obtain a damping factor so high that the angle of correction becomes irrelevent because the error is so small, but then the loudspeaker cable and any crossover/loudspeaker circuitry will ring against what is virtually the amplifier's zero output impedance, which is another aspect of 'solid-state sound'.
These misconceptions arise because the amplifier is observed in isolation.
Look at it from the loudspeaker's point of view. It responds to voltage, but simultaneously dynamically modifies the current drawn, as well as coincidentally generating entirely new currents that are not related to input voltage. It is these new currents that cause the amplifier to reactively generate new internal error voltages, and this happens so fast that it becomes a 'glare'.
The other aspect relates to currents reflecting at the terminals of a high NFB amplifier.
This is due to unavoidable cable *impedance* which again causes fractional voltage generation that especially affects treble, though it is not possible to measure it using steady sine waves. The voltage at the loudspeaker terminals can be dynamically rendered fractionally different to those appearing at the amplifier's output terminals.
Thus a cable driven loudspeaker system can reproduce more accurately when the amplifier's damping factor is not high, as with tube amplifiers.
So, a high damping factor amplifier can be additionally protected from loudspeaker back EMF, and a loudspeaker can be protected from high damping factor cable/loudspeaker ringing, by the simple addition of a series output resistor at the output terminal of the amplifier, say 0.1 or 0.22 ohms, but the nature of the loudspeaker itself would be relevant here, and there is no such design standard.
Cheers ......... Graham.
I have not said that a damping factor of 100 is all that's needed.
Also you are informing me that reverse commutation is psu related.
Well maybe that is possible, but I am thinking of something different !
When the NFB correction within an amplifier is not in phase with the sensed error (ie. open loop gain is phase shifted within the desired activity band), then a class-AB output stage cannot be prevented from being fractionally modulated by cable/loudspeaker generated back EMF. The error voltage generated within an amplifier due to self inductance prior to output node sensing has nothing to do with a subsequent series output choke or any cable/loudspeaker.
An 8R voice coil is not going to be damped significantly differently by an additional 0.01R in series with it when compared to 0.1R, sure the cable gives that anyway !!!
But, the back EMF induced by crossover circuitry can be much more significant within the audio passband because the acting coils and capacitors seldom have series resistors at each pole filter; they are highly reactive around their crossover frequencies. Separate damping/compensation components might smooth the 'impedance' curve, but these components cannot act within the same timeframe.
The additional *voltage* output error generated by an amplifier as it attempts to damp dynamically induced back EMF *current* is directly related to damping factor multiplied by the sine of the angle of internal output stage (inductance) at the frequency of interest, not just the damping factor alone.
It is possible to obtain a damping factor so high that the angle of correction becomes irrelevent because the error is so small, but then the loudspeaker cable and any crossover/loudspeaker circuitry will ring against what is virtually the amplifier's zero output impedance, which is another aspect of 'solid-state sound'.
These misconceptions arise because the amplifier is observed in isolation.
Look at it from the loudspeaker's point of view. It responds to voltage, but simultaneously dynamically modifies the current drawn, as well as coincidentally generating entirely new currents that are not related to input voltage. It is these new currents that cause the amplifier to reactively generate new internal error voltages, and this happens so fast that it becomes a 'glare'.
The other aspect relates to currents reflecting at the terminals of a high NFB amplifier.
This is due to unavoidable cable *impedance* which again causes fractional voltage generation that especially affects treble, though it is not possible to measure it using steady sine waves. The voltage at the loudspeaker terminals can be dynamically rendered fractionally different to those appearing at the amplifier's output terminals.
Thus a cable driven loudspeaker system can reproduce more accurately when the amplifier's damping factor is not high, as with tube amplifiers.
So, a high damping factor amplifier can be additionally protected from loudspeaker back EMF, and a loudspeaker can be protected from high damping factor cable/loudspeaker ringing, by the simple addition of a series output resistor at the output terminal of the amplifier, say 0.1 or 0.22 ohms, but the nature of the loudspeaker itself would be relevant here, and there is no such design standard.
Cheers ......... Graham.
A nice simulation test is to feed the amp's output with +-10V square wave voltage source series with 8R. With input sine signal ( to look for intermodulaion products) or without (some go into crazy oscilation). Some may feel strange when they see sum of Dirac's deltas at output.
I think it is good if amp damps the square in 4us without significant ringing.
I think it is good if amp damps the square in 4us without significant ringing.
An amp speaker combination should be regarded as a SYSTEM anyway. If your amp has a lower DF than desired you simply make the speaker cabinet larger than planned and then you have your desired total system Q.
I don't see any logical reason anyway for not more speakers being active nowadays. With an active system you can tune system Q almost independantly of box size/DF (hint: LTF) and one can do this PER DRIVER.
Regarding DF: Although it should be reasonably high (> 100 is O.K. for me) it is more important that it is constant over the audio frequency range (already mentioned) and that it is independant of output voltage/current.
The reason that some beefy amps with high DF have more precise and powerful bass is often caused by that fact that they are BEEFY and not by their high DF.
Regards
Charles
I don't see any logical reason anyway for not more speakers being active nowadays. With an active system you can tune system Q almost independantly of box size/DF (hint: LTF) and one can do this PER DRIVER.
Regarding DF: Although it should be reasonably high (> 100 is O.K. for me) it is more important that it is constant over the audio frequency range (already mentioned) and that it is independant of output voltage/current.
The reason that some beefy amps with high DF have more precise and powerful bass is often caused by that fact that they are BEEFY and not by their high DF.
Regards
Charles
This is good experiment http://www.diyaudio.com/forums/showthread.php?postid=651443#post651443
Very similiar to what Mr. Graham Maynard suggest. If Jean Hiraga in France and Mr. Maynard is in England, suggesting the same thing, there should be something about it.
For the "big feedback" fans (to get great 0.00....THD or great Damping factor), it is a challange here.
Very similiar to what Mr. Graham Maynard suggest. If Jean Hiraga in France and Mr. Maynard is in England, suggesting the same thing, there should be something about it.
For the "big feedback" fans (to get great 0.00....THD or great Damping factor), it is a challange here.
amplifierguru said:
Yes the speaker cable plays a vital role in Damping Factor analysis, but the back EMF , in my opinion is something which is independent of cable length to some extent and to cope with it, the amp must features high damping factor to counterface the situation. In active subwoofers such as meyersound systems , i have seen the output devices mounted just 3 inch far from the speaker terminals and that is something to get consideration.... Regarding Frequency , the DF must remain in domain , especially when low frequencies are under consideration because the low frequency woofers generate much more back EMF in comparision to high frequency tweeters or midrange speakers and of course their also the reactive nature of passive crossover exists which somehow accelerates this and the ringing would be obtained with the amp having low DF.
Mastertech I think your field of knowledge is confined to some reference level domestic house-hold hi-fi's only, So my advise to you is to do much more ellaborative thinking in professional arena, before making such type of comments.....mastertech said:
you saying that cone motion is controled by less damping factor, which simply makes no sense in professional world of amplifiers in general and even in Technical aspects. if this were true than amps with high damping factor sound worst in bass domain around the world
mastertech said:
Now you again falling short in your comment...... Power without control worth nothing ..... Obtaining Large SPL 's of bass output requires large power output, but with large damping factor that is a control .........you cannot simply obtain large bass output with large power amp having low DF as it will not able to withstand the Tremendous Back EMF generated by the subwoofer and will start ringing the cone.......overkill of output devices definately reduces output impedance hence increases DF.....
We are out of control a bit.
One comment. Kanwar, all due respect, the laws of physics do not change between pro and home audio. I do not see why we need to hear about pro with a superior tone. In pro there are parameters that are important, they may be different for home and vice versa. Two different jobs are performed. The laws of physics are the same. "The Pro Enviroment" can be taken as reliablility first, sound quality second.
To be truthful, pro stuff has to stand up to lots of abuse. There are many great home amps that sound way better (not necessarilly better than yours-I don't know) than pro amps but will not put up with the operating conditions. Therefore you would not use a great sounding home amp for a concert gig (not even a truck full), yes it's been done. By the same token we don't dream of using a concert amp in the home. Yes, that too has been done. Use the correct tool for the job.
Stop whinning that a pro amp is superiour, it's just a different tool. That's all.
-Chris
One comment. Kanwar, all due respect, the laws of physics do not change between pro and home audio. I do not see why we need to hear about pro with a superior tone. In pro there are parameters that are important, they may be different for home and vice versa. Two different jobs are performed. The laws of physics are the same. "The Pro Enviroment" can be taken as reliablility first, sound quality second.
To be truthful, pro stuff has to stand up to lots of abuse. There are many great home amps that sound way better (not necessarilly better than yours-I don't know) than pro amps but will not put up with the operating conditions. Therefore you would not use a great sounding home amp for a concert gig (not even a truck full), yes it's been done. By the same token we don't dream of using a concert amp in the home. Yes, that too has been done. Use the correct tool for the job.
Stop whinning that a pro amp is superiour, it's just a different tool. That's all.
-Chris
Mikeks,
If you dont figure out what is happening here in this thread then please feel relaxed and get some good sound sleep along with VI limiting of nightmares or probably the virtual dreams in double slope SOAR......
Chris,
The Pro Environment cannot be taken as reliability first, sound quality second....Its an old school thought....In present scenario pro environment is a combination of best sound + best reliability, the sound doesnot comes after the reliability but it goes hand in Hand with reliability, whereas domestic environment sound comes first, reliability doesnot matters, thats why Pro Arena is somewhat more superior than domestic....
Pro-amps and domestic amps are really different tools , but pro-amps are now designed to match the sonic perspectives of high -end domestic amps, because the end-user or pro-amp user now feels that its amp must sounds as good as domestic consumer high end types and now all the pro-amp manufactures started to thinking in this way and the outcome is new high end pro amps which are superior in sound quality which they were never than before.....
Secondly Domestic amps are made within kilowatt range powers whereas pro-amps are manufactured kilowatt+++ levels , therefore demand more engineering and talent to get best sound even at high SPL's......... Whereas your domestic amp always run in midpower ranges......
The Pro-Arena is changing very fast........as compared to domestic wares.....
best regards,
Kanwar
If you dont figure out what is happening here in this thread then please feel relaxed and get some good sound sleep along with VI limiting of nightmares or probably the virtual dreams in double slope SOAR......
anatech said:
Chris,
The Pro Environment cannot be taken as reliability first, sound quality second....Its an old school thought....In present scenario pro environment is a combination of best sound + best reliability, the sound doesnot comes after the reliability but it goes hand in Hand with reliability, whereas domestic environment sound comes first, reliability doesnot matters, thats why Pro Arena is somewhat more superior than domestic....
Pro-amps and domestic amps are really different tools , but pro-amps are now designed to match the sonic perspectives of high -end domestic amps, because the end-user or pro-amp user now feels that its amp must sounds as good as domestic consumer high end types and now all the pro-amp manufactures started to thinking in this way and the outcome is new high end pro amps which are superior in sound quality which they were never than before.....
Secondly Domestic amps are made within kilowatt range powers whereas pro-amps are manufactured kilowatt+++ levels , therefore demand more engineering and talent to get best sound even at high SPL's......... Whereas your domestic amp always run in midpower ranges......
The Pro-Arena is changing very fast........as compared to domestic wares.....
best regards,
Kanwar
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