Pertinent point totally missed here is that driver acceleration, slew, or whatever you want to call it, does not come into it, at all.
Rather than a driver running out of slew to be able to reproduce the highest frequencies, the driver is low passed by the mass corner of the moving mass.
This naturally limits the high frequency extension.
Where drivers 'run out of capability' is at large displacements and at LOW frequency, rather than High.
Rather than a driver running out of slew to be able to reproduce the highest frequencies, the driver is low passed by the mass corner of the moving mass.
This naturally limits the high frequency extension.
Where drivers 'run out of capability' is at large displacements and at LOW frequency, rather than High.
If the slew rate isn't the limiting factor, I think this is what I was missing. I don't think I fully understand though. I will if you can answer if this frequency changes with amplitude, or increases if BI increases (other parameters remaining equal)
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I appreciate all the input thus far, but before getting into things I don't understand well enough to discuss without a bunch of reading:
A speaker has a permanent magnet which an electromagnet (coil) uses the field of to generate force. With increasing power, is the amount of force that can be generated up to no limit (disregarding increasing temperature)? Is force linear with power up to a maximum, or does it require more and more power to come closer and closer to maximum, never quite reaching it?
A speaker has a permanent magnet which an electromagnet (coil) uses the field of to generate force. With increasing power, is the amount of force that can be generated up to no limit (disregarding increasing temperature)? Is force linear with power up to a maximum, or does it require more and more power to come closer and closer to maximum, never quite reaching it?
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Yes.
And the reason I wanted to use bursts was to avoid thermal compression. I was thinking these measurements would need be done at power levels well above RMS before becoming statistically significant
I haven't put a tone bursts through a spectrum analyzer, but I'm guessing there's some content above the tones frequency
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Importance of slew rate and transient response
Its upper mass corner [Fhm], [Qts'] where T/S theory peters out defines its transient response:
Fhm = 2*Fs/Qts'
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor plus any added resistance from an XO/whatever.
'Fast' in this context is an over-damped response [< 0.5], ergo 'Slow' is an under-damped one [>0.5] with of course a 0.5 = transient perfect/critically damped, though in some old texts 0.707 is critically damped.
These tell me all I need to know about a driver's transient response, so will leave it to you/others to decide how to convert this to a slew rate, which like group delay I'll ignore since my designs are always critically damped. 😉
Its upper mass corner [Fhm], [Qts'] where T/S theory peters out defines its transient response:
Fhm = 2*Fs/Qts'
[Qts']: [Qts] + any added series resistance [Rs]: Calculate new Qts with Series Resistor
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor plus any added resistance from an XO/whatever.
'Fast' in this context is an over-damped response [< 0.5], ergo 'Slow' is an under-damped one [>0.5] with of course a 0.5 = transient perfect/critically damped, though in some old texts 0.707 is critically damped.
These tell me all I need to know about a driver's transient response, so will leave it to you/others to decide how to convert this to a slew rate, which like group delay I'll ignore since my designs are always critically damped. 😉
I agree. These should be standard.
Distortion at 1w, 10w, and electrical maximum should be listed. All limited to xmax, with the frequency xmax is reached clearly marked. Measured in a sealed enclosure of optimal size. Distortion levels at 2x voltage for RMS power, 50ms tone bursts starting 1 octave above xmax marking.
Would simplify choosing a driver and eliminate garbage drivers lol
No.
GM means a Total Q, Qb, Box Q of 0.5.
I think (and speaking for him) GM may be speaking about both Qb and Qts.
He has vastly more understanding than I, and I'm sure will correct my errors.
GM means a Total Q, Qb, Box Q of 0.5.
I think (and speaking for him) GM may be speaking about both Qb and Qts.
He has vastly more understanding than I, and I'm sure will correct my errors.
Possibly. I said Qts because it's the lower limit for Qtc. In post 5 I mentioned that I'm talking about transient response of frequencies above where box tuning affects it
Go and listen to a good pair of cans if you want 'transient response' at low frequencies. Or set up your set outdoors.
You look at the response of a driver, you see a frequency with a level and phase. This is what it will do if you ask it to, within the normal operating range.
This is called small signal analysis and that does not mean it only applies at small inputs. There are limiting factors that apply such as excursion limits, mechanical and magnetic.. these are unrelated to the initial condition and should be looked at on a separate occasion.
I take it you mean that you double the applied input Voltage, and the output pressure doubles. Double it again, etc...
This is called small signal analysis and that does not mean it only applies at small inputs. There are limiting factors that apply such as excursion limits, mechanical and magnetic.. these are unrelated to the initial condition and should be looked at on a separate occasion.
I just picked it to be a higher level, to be near the loudest transients a driver would be asked to produce
I'll say again, this is (and always has been, clarified in post 5) regarding frequencies above the ones affected by box volume
Can anyone saying what I brought up is a non issue please answer post 23:
"A speaker has a permanent magnet which an electromagnet (coil) uses the field of to generate force. With increasing power, is the amount of force that can be generated up to no limit (disregarding increasing temperature)? Is force linear with power up to a maximum, or does it require more and more power to come closer and closer to maximum, never quite reaching it?"
There Is force and mass, the speed of the mass depends on the force.
Edit: it seems very unlikely, to me at least, that there is no limit
Maybe "magnitude of driver response to transient signals" is better
For a woofer, a 1 second pulse of 300, 500, 1000, 2000hz at 1w and 100w for a 50wrms driver.
If the driver is 1% efficient at 1w, and 0.92% efficient at 100w, the driver has a 92% magnitude response to transient signals.
Rt =92. Voila. Aim for as close to 100.
Is any of this compression related to the strength of the magnet? Would a stronger magnet on the same driver ensure less of it?
"A speaker has a permanent magnet which an electromagnet (coil) uses the field of to generate force. With increasing power, is the amount of force that can be generated up to no limit (disregarding increasing temperature)? Is force linear with power up to a maximum, or does it require more and more power to come closer and closer to maximum, never quite reaching it?"
There Is force and mass, the speed of the mass depends on the force.
Edit: it seems very unlikely, to me at least, that there is no limit
Maybe "magnitude of driver response to transient signals" is better
For a woofer, a 1 second pulse of 300, 500, 1000, 2000hz at 1w and 100w for a 50wrms driver.
If the driver is 1% efficient at 1w, and 0.92% efficient at 100w, the driver has a 92% magnitude response to transient signals.
Rt =92. Voila. Aim for as close to 100.
Is any of this compression related to the strength of the magnet? Would a stronger magnet on the same driver ensure less of it?
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You misunderstood what I was asking then. Yes, pressure doubles with power. It should, if the driver remains linear. If there is a loss of efficiency at a higher level, can some of it be attributed to what I described in 34?
Put another way, the permanent magnet is only so strong. If you drop a weighted coil into a motor (say 100g) and give it a pulse at 10v, it shoots out with a velocity of x. Increase the voltage from 10v to 20 to 30, continuing to 1000, each time it shoots out faster. But, at some point, the speed is not limited by the voltage anymore, but the magnet that the coil is using to push off of. (Ignore air resistance, the coil weighs 100g, not a 12" cone)
This is what I'm referring to in 23.
Does it work as I described above, or does force continue increasing with voltage at the same rate indefinitely?
This is what I'm referring to in 23.
Does it work as I described above, or does force continue increasing with voltage at the same rate indefinitely?
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Indefinitely? Obviously not, but until that point yes.... This is why I mentioned a separation between small signal analysis and non-linear behaviour... and the idea of the stronger magnet, would change things at low levels too, altering the result but not allowing it to go on indefinitely.
Ordinarily, doubling the drive Voltage doubles the pressure and quadrupling the drive Voltage quadruples the pressure.
Ordinarily, doubling the drive Voltage doubles the pressure and quadrupling the drive Voltage quadruples the pressure.