A clue
Excellent- a nice concise post,
You don't get thrown off a discussion group for saying the emperor has no clothes, and expressing your opinion, you get thrown off for obnoxious behavior that doesn't respect others. Another opinion: Yes it is important to stand by your beliefs and please yourself, but compromise is sometimes good- it shows you have an open mind and are willing to consider other's opinions and knowledge.
I apologize to all for this additional self indulgent screed, and won't post on this thread again.
Excellent- a nice concise post,
You don't get thrown off a discussion group for saying the emperor has no clothes, and expressing your opinion, you get thrown off for obnoxious behavior that doesn't respect others. Another opinion: Yes it is important to stand by your beliefs and please yourself, but compromise is sometimes good- it shows you have an open mind and are willing to consider other's opinions and knowledge.
I apologize to all for this additional self indulgent screed, and won't post on this thread again.
definitions
I am not sure that the driver impedance per se limits the dampability, as someone stated earlier on. If this were true, a 4R driver would be inherently superior to an 8R driver which does not seem to be the case. At least, I have never heard this to be an empirical truth. Neither would the definition of the damping factor as driver impedance / amp output impedance be meaningful if this were true.
The voicecoil can be regarded as a transformer between the acoustic energy acting on the cone and the electrical signal that is generated by it and should be damped. Twice as many turns may give twice the DC impedance, but also twice the induced voltage. Assuming that external energy is fixed, only half the current needs to be damped, so the doubled resistance would not hurt.
One should also differentiate between LF and HF damping factor, the latter being usually lower. This is partly due to lower loop gain (feedback) at higher frequencies, but usually, most of it is due to the coil that is added at the output of most amps to insure stability with all kinds of loads.
One might argue whether the midrange and tweeter drivers need that much damping, the tweeter having a series resistor in many crossover designs. But the frequency response may become warped if the impedance of the speaker isn't flat. Also, the coils found in many commercial designs are just longish air coils made of woefully thin wire that vibrate with the current applied to them, so their impedance is probably not very linear with the amplitude. First thing one can do is to put some epoxy glue on them....
Eric
I am not sure that the driver impedance per se limits the dampability, as someone stated earlier on. If this were true, a 4R driver would be inherently superior to an 8R driver which does not seem to be the case. At least, I have never heard this to be an empirical truth. Neither would the definition of the damping factor as driver impedance / amp output impedance be meaningful if this were true.
The voicecoil can be regarded as a transformer between the acoustic energy acting on the cone and the electrical signal that is generated by it and should be damped. Twice as many turns may give twice the DC impedance, but also twice the induced voltage. Assuming that external energy is fixed, only half the current needs to be damped, so the doubled resistance would not hurt.
One should also differentiate between LF and HF damping factor, the latter being usually lower. This is partly due to lower loop gain (feedback) at higher frequencies, but usually, most of it is due to the coil that is added at the output of most amps to insure stability with all kinds of loads.
One might argue whether the midrange and tweeter drivers need that much damping, the tweeter having a series resistor in many crossover designs. But the frequency response may become warped if the impedance of the speaker isn't flat. Also, the coils found in many commercial designs are just longish air coils made of woefully thin wire that vibrate with the current applied to them, so their impedance is probably not very linear with the amplitude. First thing one can do is to put some epoxy glue on them....
Eric
Further to Nelson's post....
Back when I had time to actually play around with audio equipment, I was starting to look at how various amplifiers "dealt" with back-emf from the speaker. The sources of back-emf could come from the speaker itself (what starts moving will keep moving....), not to mention from room pressurization, etc. I was as much playing around with the amount of porting, speaker dampening material, etc. I would even go outside to eliminate room effects.
This is a really easy thing to play with though. Get a speaker you don't care about, and then start pushing on the speaker. Take your scope and look at the output of your amplifier.
What I found is that some amplifiers, I am guessing those being on the hairy edge of stable, would exhibit definate ringing on the output independant of just the speaker movement. Those amplifiers being my cheapy, mid-80's Japanese stuff. My lone tube amp (sorry, it has long since died so I can't recreate this), kept a relatively constant output sans a bit of movement. The good transistor amp I had was in the middle.
If I had to list them, the good transistor amp would have the best DF, the tube amp the lowest (probably by a good margin).
... getting to Nelson's comments. In general, the more feedback you have, the less stable your amplifier and the more prone to oscillation. Could this be why the better amps with lower DF have more real control and depth?
Alvaius
... As will always be... sound is the output of a system, not one device...
Back when I had time to actually play around with audio equipment, I was starting to look at how various amplifiers "dealt" with back-emf from the speaker. The sources of back-emf could come from the speaker itself (what starts moving will keep moving....), not to mention from room pressurization, etc. I was as much playing around with the amount of porting, speaker dampening material, etc. I would even go outside to eliminate room effects.
This is a really easy thing to play with though. Get a speaker you don't care about, and then start pushing on the speaker. Take your scope and look at the output of your amplifier.
What I found is that some amplifiers, I am guessing those being on the hairy edge of stable, would exhibit definate ringing on the output independant of just the speaker movement. Those amplifiers being my cheapy, mid-80's Japanese stuff. My lone tube amp (sorry, it has long since died so I can't recreate this), kept a relatively constant output sans a bit of movement. The good transistor amp I had was in the middle.
If I had to list them, the good transistor amp would have the best DF, the tube amp the lowest (probably by a good margin).
... getting to Nelson's comments. In general, the more feedback you have, the less stable your amplifier and the more prone to oscillation. Could this be why the better amps with lower DF have more real control and depth?
Alvaius
... As will always be... sound is the output of a system, not one device...
Mr. Pass
I do like your ideas (I actually experienced them) but if you have others as well don't withhold them.
To capslock:
The reason why the resistance-related restriction on damping is still valid, even when drivers of different impedance have the same Qes, is simply because everything is equalled out (I don't know if this is the correct English term for what I mean) by the DESIGN of the drivers, making one to have a certain Qes wit Rdc of 3 Ohms and the other one having the same Qes with an Rdc of 6 Ohms ! But of course half the increase in amp output resistance for the lower impedance driver would have the same detrimental effect as given increase for the higher impedance driver !
Regards
Charles
I do like your ideas (I actually experienced them) but if you have others as well don't withhold them.
To capslock:
The reason why the resistance-related restriction on damping is still valid, even when drivers of different impedance have the same Qes, is simply because everything is equalled out (I don't know if this is the correct English term for what I mean) by the DESIGN of the drivers, making one to have a certain Qes wit Rdc of 3 Ohms and the other one having the same Qes with an Rdc of 6 Ohms ! But of course half the increase in amp output resistance for the lower impedance driver would have the same detrimental effect as given increase for the higher impedance driver !
Regards
Charles
There is something wrong when speaker’s voice-coil is observed as inductor in series with resistor. Let me be clear, I don’t see problems with this when we investigate what amp sees (though actual equivalent schematic of speaker is more complicated.)
Problem is when we discuss what speaker sees. Speaker does not see its resistance/impedance. In this case speaker is generator with certain output impedance. Its impedance sees amp, not speaker. In this way, speaker is directly connected to amp and damping factor IS important.
But, I cannot see any purpose of DF other than to damp parasitic oscillations of speaker. If speaker is well formed, its parasitic oscillations are out of the range they work (behind the X-over’s cut-off point). Of course, principally it is good, they are damped in the term they don’t work in a region of parasitic oscillations, but this goal can be achieved only partially. Some parasitic oscillations stays, and they should be damped, and here x-over appears as unwelcome impedance. That means it forms the bulk of impedance that speaker sees, amp’s output impedance is negligible in comparison and that means unimportant. In a region the drivers work normally, they have less parasitic oscillations to be damped.
In the bass region, where there are also uncontrolled movements of the speaker’s cone, speaker is (electrically) directly connected. This can explain why amps with better damping factor have better controlled bass, and why everything else is not so clear. Of course, there are exceptions (as always)…
(All these observations assume damping factor only as a possibility of amp to accept energy induced in speakers.)
Pedja
Problem is when we discuss what speaker sees. Speaker does not see its resistance/impedance. In this case speaker is generator with certain output impedance. Its impedance sees amp, not speaker. In this way, speaker is directly connected to amp and damping factor IS important.
But, I cannot see any purpose of DF other than to damp parasitic oscillations of speaker. If speaker is well formed, its parasitic oscillations are out of the range they work (behind the X-over’s cut-off point). Of course, principally it is good, they are damped in the term they don’t work in a region of parasitic oscillations, but this goal can be achieved only partially. Some parasitic oscillations stays, and they should be damped, and here x-over appears as unwelcome impedance. That means it forms the bulk of impedance that speaker sees, amp’s output impedance is negligible in comparison and that means unimportant. In a region the drivers work normally, they have less parasitic oscillations to be damped.
In the bass region, where there are also uncontrolled movements of the speaker’s cone, speaker is (electrically) directly connected. This can explain why amps with better damping factor have better controlled bass, and why everything else is not so clear. Of course, there are exceptions (as always)…
(All these observations assume damping factor only as a possibility of amp to accept energy induced in speakers.)
Pedja
An awful lot of people spend their money. Nelson should be greatful! And probably is.
I found this on "damping factor".
Might clarify some things. might not.
http://classic-audio.com/marantz/mdampingfactor.html
I take the liberty to copy the last paragraph,
and quote it to you.
--------------------------------------------------------
Hey, enjoy your music. Don't sweat it. Play with the knobs, and if you like what you're hearing, the specs are probably pretty good. Or your ears don't care. Maybe someday you'll hear something better, or you'll use specs to put something together you know is better. Maybe not. But if you like what you're hearing, you're on the right path. I can guarantee you one thing: There are an awful lot of people out there spending money on specs they will never be able to hear as differences in the music in a million years. Just don't expect them to ever admit it. I have to really work not to laugh my head off when someone tells me they spent several hundred dollars - or even over a thousand - on speaker cables and they "sound better" than a nice heavy gauge twisted pair of stranded copper wires they could have had for about five bucks...
-----------------------------------------------------------
I found this on "damping factor".
Might clarify some things. might not.
http://classic-audio.com/marantz/mdampingfactor.html
I take the liberty to copy the last paragraph,
and quote it to you.
--------------------------------------------------------
Hey, enjoy your music. Don't sweat it. Play with the knobs, and if you like what you're hearing, the specs are probably pretty good. Or your ears don't care. Maybe someday you'll hear something better, or you'll use specs to put something together you know is better. Maybe not. But if you like what you're hearing, you're on the right path. I can guarantee you one thing: There are an awful lot of people out there spending money on specs they will never be able to hear as differences in the music in a million years. Just don't expect them to ever admit it. I have to really work not to laugh my head off when someone tells me they spent several hundred dollars - or even over a thousand - on speaker cables and they "sound better" than a nice heavy gauge twisted pair of stranded copper wires they could have had for about five bucks...
-----------------------------------------------------------
Hi Pedja
I did not state that DF doesn't matter at all (see my first post in this thread) but that it's impact is sometimes overestimated.
And there is no logical argument that the "generator" loudspeaker doesn't "see" the amplifier (which would theoretically be a voltage source) via the sum of all impedances inbetween ( connector(s) + cable(s) + crossover + voice-coil inductance + VOICE COIL DC RESISTANCE). Because the driver's DC resistance is usually the largest (by far !) of them all, it is also the one that affects damping of the driver's fundamental resonance the most. You can of course eliminate it a little by using an amp with negative output impedance but you'd rather take care !!!
Regards
Charles
I did not state that DF doesn't matter at all (see my first post in this thread) but that it's impact is sometimes overestimated.
And there is no logical argument that the "generator" loudspeaker doesn't "see" the amplifier (which would theoretically be a voltage source) via the sum of all impedances inbetween ( connector(s) + cable(s) + crossover + voice-coil inductance + VOICE COIL DC RESISTANCE). Because the driver's DC resistance is usually the largest (by far !) of them all, it is also the one that affects damping of the driver's fundamental resonance the most. You can of course eliminate it a little by using an amp with negative output impedance but you'd rather take care !!!
Regards
Charles
damping factor etc
May I throw another spanner in the works?
What is damping? It is the removal of energy from a system. If no energy is removed, the unwanted movement of the speaker continues. To remove energy, it must be dissipated. You can only dissipate energy in a resistive component, not in a coil or cap. Of course, you can dissipate energy in the resistive part of a coil, but you get the point.
So, back to our amplifier with the very low Rout. If this actually damps the speaker movement, where does the energy go? The amp can only keep its output at zero volts, when the speaker supplies a current, by a counter current from the output stage. Say, as an example, the speaker has a back-EMF that generates a current of 1 A in a short. Our ideal amp needs to "suck" that 1 A from its output in order to keep the output terminal at zero volts. So, the energy goes back into the amps power supply, and some is dissipated in the output stage resistive Rout. But I would think that most of it is dissipated in the speakers resistive elements, notably its voicecoil, because that is the largest part. That means that the output impedance of the amp has no effect on the damping at all, because it plays almost no role in the removal of energy.
There is another effect of the amp output resistance however that influences the sound quality. If the amp cannot fully null for the speaker generated signal, some of it will stay at the output, and be added to the "normal" signal from the input. That means that the result is a distortion of the signal, probably undistinguisable from other distortion products.
Anybody want to shoot any holes in this?
May I throw another spanner in the works?
What is damping? It is the removal of energy from a system. If no energy is removed, the unwanted movement of the speaker continues. To remove energy, it must be dissipated. You can only dissipate energy in a resistive component, not in a coil or cap. Of course, you can dissipate energy in the resistive part of a coil, but you get the point.
So, back to our amplifier with the very low Rout. If this actually damps the speaker movement, where does the energy go? The amp can only keep its output at zero volts, when the speaker supplies a current, by a counter current from the output stage. Say, as an example, the speaker has a back-EMF that generates a current of 1 A in a short. Our ideal amp needs to "suck" that 1 A from its output in order to keep the output terminal at zero volts. So, the energy goes back into the amps power supply, and some is dissipated in the output stage resistive Rout. But I would think that most of it is dissipated in the speakers resistive elements, notably its voicecoil, because that is the largest part. That means that the output impedance of the amp has no effect on the damping at all, because it plays almost no role in the removal of energy.
There is another effect of the amp output resistance however that influences the sound quality. If the amp cannot fully null for the speaker generated signal, some of it will stay at the output, and be added to the "normal" signal from the input. That means that the result is a distortion of the signal, probably undistinguisable from other distortion products.
Anybody want to shoot any holes in this?
big hardware <-> damping factor
Nelson, I think your observation is not necessarily at odds with the concept of DF if you take into accound that DF can be nonlinear.
I'll argue with a very conventional BJT design in mind. Part of its output resistance is determined by how well the voltage gain stage is buffered from the output. This means it is determined by the current gain and gain linearity of the emitter follower driver and output transistors. In a small amp this gain may be quite high for small signals but the transistors may get into the gain drooping region quite quickly. Conversely, a larger amp might also have larger devices are a greater number of them in parallel so that their gain remains more constant at a given high output level. This particular design might have a lower overall damping factor due to other reasons such as lower feedback, but this damping factor is more constant with output amplitude. I guess the same arguement can be made for the stiffness of the power supply, which is bound to have some nonlinear influence on DF.
I know you use MOSFETS, but I am not that familiar with your topologies, so I am not sure if this argument holds for your amps. I know that MOSFETS suffer from thermal modulation especially at low frequencies. Larger devices would simply see less of a thermal signal.
In my very first design I had 2 or 3 A slow blow fuses in series with the output. Their resistance of roughly 50 mR should have been negligable, and thermal modulation of this resistance at output levels of <1 W should have been absolutely insignificant. Still, I remember that I had the impression of a much tighter and crisper bass when I shunted them.
Regards,
Eric
Nelson, I think your observation is not necessarily at odds with the concept of DF if you take into accound that DF can be nonlinear.
I'll argue with a very conventional BJT design in mind. Part of its output resistance is determined by how well the voltage gain stage is buffered from the output. This means it is determined by the current gain and gain linearity of the emitter follower driver and output transistors. In a small amp this gain may be quite high for small signals but the transistors may get into the gain drooping region quite quickly. Conversely, a larger amp might also have larger devices are a greater number of them in parallel so that their gain remains more constant at a given high output level. This particular design might have a lower overall damping factor due to other reasons such as lower feedback, but this damping factor is more constant with output amplitude. I guess the same arguement can be made for the stiffness of the power supply, which is bound to have some nonlinear influence on DF.
I know you use MOSFETS, but I am not that familiar with your topologies, so I am not sure if this argument holds for your amps. I know that MOSFETS suffer from thermal modulation especially at low frequencies. Larger devices would simply see less of a thermal signal.
In my very first design I had 2 or 3 A slow blow fuses in series with the output. Their resistance of roughly 50 mR should have been negligable, and thermal modulation of this resistance at output levels of <1 W should have been absolutely insignificant. Still, I remember that I had the impression of a much tighter and crisper bass when I shunted them.
Regards,
Eric
Hi Guys,
My experience is that if the damping factor were simply the result of a finite output resistance on a pure voltage source, then its effects would be consistent and there would be no controversy.
Unfortunately, most amplifiers are not yet close to being a pure voltage source for anything other than DC, or a steady state sine wave into a "real" 8 Ohm load.
As soon as transient signals become involved with complex loudspeaker impedance, limitations in the output driver speed & gain, PSU max current delivery, and feedback topology, cause many amplifiers to exhbit gross limitations in overall current delivery that dramatically reduce the amplifiers instantaneous ability to damp the movement of a voice coil.
Ideally, if the amp were a pure voltage source, the ringing effects of transient speaker voice coil movement would be damped by very high short term currents supplied by the amp through the voice coil, which would literally act as a brake on the voice coil as it moved through the magnetic field.
Unfortunately, while for small, steady state signals, the amp's damping ability is directly related to the damping factor, once the changes become large and dramatic, the amp stops operating as a voltage source, and clips momentarily (limited by either speed, gain, or PSU current capacity) either the curent or voltage supplied to the speaker, and then you get the discrepancies between amps.
The higher instantaneous current capacity offered by most of the higher powered amps is the reason for the general rule of thumb that bigger is generally better in terms of control. However, the best designs I have heard have been lower power (even with a lower damping factor), below 50 Watts, but with a massive, fast, instantaneous peak current capacity.
This is one of the reasons why tube amps with their often poor damping factor figures can offer much better control of the bass frequencies - they are both faster at delivering the higher currents, and the "lever action" of the transformer design allows for much higher instantaneous peak output currents without over-stressing the instantaneous current delivery capability of the drivers/psu.
Interesting stuff, though...
Bill.
My experience is that if the damping factor were simply the result of a finite output resistance on a pure voltage source, then its effects would be consistent and there would be no controversy.
Unfortunately, most amplifiers are not yet close to being a pure voltage source for anything other than DC, or a steady state sine wave into a "real" 8 Ohm load.
As soon as transient signals become involved with complex loudspeaker impedance, limitations in the output driver speed & gain, PSU max current delivery, and feedback topology, cause many amplifiers to exhbit gross limitations in overall current delivery that dramatically reduce the amplifiers instantaneous ability to damp the movement of a voice coil.
Ideally, if the amp were a pure voltage source, the ringing effects of transient speaker voice coil movement would be damped by very high short term currents supplied by the amp through the voice coil, which would literally act as a brake on the voice coil as it moved through the magnetic field.
Unfortunately, while for small, steady state signals, the amp's damping ability is directly related to the damping factor, once the changes become large and dramatic, the amp stops operating as a voltage source, and clips momentarily (limited by either speed, gain, or PSU current capacity) either the curent or voltage supplied to the speaker, and then you get the discrepancies between amps.
The higher instantaneous current capacity offered by most of the higher powered amps is the reason for the general rule of thumb that bigger is generally better in terms of control. However, the best designs I have heard have been lower power (even with a lower damping factor), below 50 Watts, but with a massive, fast, instantaneous peak current capacity.
This is one of the reasons why tube amps with their often poor damping factor figures can offer much better control of the bass frequencies - they are both faster at delivering the higher currents, and the "lever action" of the transformer design allows for much higher instantaneous peak output currents without over-stressing the instantaneous current delivery capability of the drivers/psu.
Interesting stuff, though...
Bill.
Hi woneill and capslock
I agree. There's nothing better than a generously designed power amp (the amp itself AND it's PSU) when it comes to LF authority.
One thing that can deteriorate LF authority as well is VI limiting, since the typical load isn't purely resistive. I.e. an output stage should be capable of dissipating a lot of power in order to be able to use pure CURRENT limiting (with a good marging!) only.
Switching amplifiers in general are also quite good (if done properly) in bass control simply due to the fact that they "dont care" into which load they deliver their power, as long as the signal frequency is much lower than the output filter cutoff frequency (but a designer has to cope with the supply pumping effect).
I was able to experience this with the TacT Millennium and the Sharp SM-SX100 amplifiers. A German HiFi magazine recently tested a prototype amp using a class - D output stage (AVM A 6) and made positive remarks about bass control.
Regards
Charles
P.S.:For the lows and mids in active speakers, switching amps would be quite cool (in every sense of this word). Current limiting could even be omitted completely.
I agree. There's nothing better than a generously designed power amp (the amp itself AND it's PSU) when it comes to LF authority.
One thing that can deteriorate LF authority as well is VI limiting, since the typical load isn't purely resistive. I.e. an output stage should be capable of dissipating a lot of power in order to be able to use pure CURRENT limiting (with a good marging!) only.
Switching amplifiers in general are also quite good (if done properly) in bass control simply due to the fact that they "dont care" into which load they deliver their power, as long as the signal frequency is much lower than the output filter cutoff frequency (but a designer has to cope with the supply pumping effect).
I was able to experience this with the TacT Millennium and the Sharp SM-SX100 amplifiers. A German HiFi magazine recently tested a prototype amp using a class - D output stage (AVM A 6) and made positive remarks about bass control.
Regards
Charles
P.S.:For the lows and mids in active speakers, switching amps would be quite cool (in every sense of this word). Current limiting could even be omitted completely.
woneill said:
Bill,
No, not at all! There is no braking effect as such. You can only damp if you remove energy, ie change it for instance to heat. If your amp has zero output impedance, the ONLY damping comes through the resistive part of the voicecoil and/or xover filter.
This may sound like hairsplitting, but is significant. The very high short term current you refer to, generates an opposing amount of force that may *temporarely* stop the cone, but as soon as you remove that current (and you have to, sooner or later) the original circulating current will move the cone again. OK, eventually it will stop, because there are resistive losses for instance in friction with the air and the ohmic losses as alluded to earlier.
The ultimate power output stage in this context is a short-circuit. Try shorting the speaker after exitation, and you will see a damped oscillation, that doesnot stop immediately if you short the driver connections, but gets smaller and smaller as energy is slowly removed from the system through all kinds of resistive losses.
Don't think that a high damping ratio amp can stop a cone dead in it's tracks, it cannot. The terminal voltage may be kept at zero by the output stage, especially if it has very low or zero impedance, but the voice coil current and cone movement lead their own lifes. The cone *has* to slowly decay to a standstill, because it will take time for the stored energy to die out.
I know this sounds counter-intuitive for a lot of people, but I think my reasoning is essentially correct.
Cheers, Jan Didden
What it boils down to is the question of whether an amp can stop a speaker more effectively than a short circuit.
My gut feeling is yes. I have not done the maths so I may be doing my training as a physicist little credit with this handwaiving argument.
The energy stored in the speaker air volume moves the cone, generating a current in the voice coil. A short circuit would sink the currents. An amp could also inject an opposing current, but that would require its output voltage to move from 0. This is something that won't happen with your everyday voltage controlled voltage source amp which behaves like a short circuit when there is no input signal -- so Jan is right!
One would need to measure the movement of the cone or even better the air pressure by using a microphone in front of the cone to generate the correcting signal.
Acitve sound cancellation through destructive interference works. The point that worries me is: where does the stored energy go?
Is it dissipated in the amp's transistors? No, due to the finite speed of sound, the cancellation works only in a certain volume close to the mike. In other areas, we are bound to see constructive interference so the energy goes into the room and gets dissipated there. If the listener does not want to creep to the mike, he will have no benefit...
My gut feeling is yes. I have not done the maths so I may be doing my training as a physicist little credit with this handwaiving argument.
The energy stored in the speaker air volume moves the cone, generating a current in the voice coil. A short circuit would sink the currents. An amp could also inject an opposing current, but that would require its output voltage to move from 0. This is something that won't happen with your everyday voltage controlled voltage source amp which behaves like a short circuit when there is no input signal -- so Jan is right!
One would need to measure the movement of the cone or even better the air pressure by using a microphone in front of the cone to generate the correcting signal.
Acitve sound cancellation through destructive interference works. The point that worries me is: where does the stored energy go?
Is it dissipated in the amp's transistors? No, due to the finite speed of sound, the cancellation works only in a certain volume close to the mike. In other areas, we are bound to see constructive interference so the energy goes into the room and gets dissipated there. If the listener does not want to creep to the mike, he will have no benefit...
cpaslock wrote
=> http://www.meyersound.com/products/studioseries/x-10/index.htm
Regrads
Charles
P.S :I wasn't able to have a listen to these babies so far but beleieve me I would if I could, though I'd never buy a pair of them.
P.P.S : Feedback is never a cure-all.
=> http://www.meyersound.com/products/studioseries/x-10/index.htm
Regrads
Charles
P.S :I wasn't able to have a listen to these babies so far but beleieve me I would if I could, though I'd never buy a pair of them.
P.P.S : Feedback is never a cure-all.
Damping etc
Ahh, Active Sound cancellation, yes, but that works by setting up an opposing air movement, for example by another transducer, to make the net air movement (as capslock rightly stated, in a very limited volume - works great with headsets though) zero. It does nothing to damp the cone movement.
As for where the current goes, there are two terminals on the driver, right? What comes out must go in - some guys law, I think it was Thevenin. Since the driver is connected to the amp, the current comes out the driver + terminal, into the amp output, through the amp bottom part to the neg supply cap, out again at the ground terminal of the neg supply cap to ground and back to the ground terminal of the driver - loop closed!
Jan Didden
Ahh, Active Sound cancellation, yes, but that works by setting up an opposing air movement, for example by another transducer, to make the net air movement (as capslock rightly stated, in a very limited volume - works great with headsets though) zero. It does nothing to damp the cone movement.
As for where the current goes, there are two terminals on the driver, right? What comes out must go in - some guys law, I think it was Thevenin. Since the driver is connected to the amp, the current comes out the driver + terminal, into the amp output, through the amp bottom part to the neg supply cap, out again at the ground terminal of the neg supply cap to ground and back to the ground terminal of the driver - loop closed!
Jan Didden
Hi Janneman and Capslock,
Sorry for my vague terminology. I agree with what you are saying. My vague use of the word braking was referring to the energy transformation from mechanical (kinetic) to electrical when a coil moves through a magnetic field: the electrical energy that is generated as the current flows through the coil, is directly transformed from the kinetic energy of the cone.
It is dissipated primarily as heat in the coil windings, and in the output stages of the amplifier. This process is not braking in its true sense, but is, the topic we are concerned with here: damping.
Many of the transient current demands on the amp are related to its ability to source/sink appropriate current to maximise this damping effect and to reduce the time taken for the kinetic energy due to the cone's/coil's movement to be dissipated such that the cone assumes the appropriate displacement based on the voltage applied by the amp.
Thinking about the physics of damping, it is quite possible to overdamp as well as underdamp - I wonder how many amps are matched to the damping requirements of the speakers they are driving such that the drivers are critically damped?
It IS a fascinating topic!
Bill.
Sorry for my vague terminology. I agree with what you are saying. My vague use of the word braking was referring to the energy transformation from mechanical (kinetic) to electrical when a coil moves through a magnetic field: the electrical energy that is generated as the current flows through the coil, is directly transformed from the kinetic energy of the cone.
It is dissipated primarily as heat in the coil windings, and in the output stages of the amplifier. This process is not braking in its true sense, but is, the topic we are concerned with here: damping.
Many of the transient current demands on the amp are related to its ability to source/sink appropriate current to maximise this damping effect and to reduce the time taken for the kinetic energy due to the cone's/coil's movement to be dissipated such that the cone assumes the appropriate displacement based on the voltage applied by the amp.
Thinking about the physics of damping, it is quite possible to overdamp as well as underdamp - I wonder how many amps are matched to the damping requirements of the speakers they are driving such that the drivers are critically damped?
It IS a fascinating topic!
Bill.
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