It was as I stated, assumed.
The imprecise language of JR is somewhat ok, but falls apart on close inspection...too simplistic for accuracy.
And as I stated earlier, the electrical inductance is the definer at hf. At lower frequency where the cone does a better job of physically following the amplifier's intent, the storage mechanism is mechanical.
I also recall during the previous discussion here, that the system behavior is significantly different at the lower end, apparently more extension due to current drive, as shown by actual results.
My thinking is this: when I drive an inductor with a sine voltage, at the peak voltage of the signal the current is ramping at it's peak rate. When the sine returns to zero, the current is at it's peak.
If I drive the inductor with a sine current, the peak current is at the peak of the drive. At signal zero, the current is zero.
So for inductance only, there is a 90 degree current shift between the two drive methods.
So yes the dominance of specific entities through the bandwidth will indeed alter the effect, hence my question.
I do not recall anybody mentioning signal processing in front of current drive, so would expect this difference to show up in the acoustic output.
Jn
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Really?
Current drive of speakers and speaker distortion
I did the job with REW, re-phase and foobar (convolve plug-in)
Please also check ETM's web page, he has done a lot of work on this.
You have just started your argument with "" the hypothesis is correct, therefore it is correct. ""
So, it is identical, however I do require signal processing to make it identical.
PMA..yes, really..no recollection. During the last discussion, my concentration was on the flux field measurement, not overall system response.
Thank you for the link and info, I will peruse it more. ESA IMHO, is brilliant..I have had private offline contact with him, and have high regard of his understandings.
So, the native questions...
1. Is current drive always precluded by signal processing.
2. Is the signal processing a perfect inversion of real drivers.
If it is always used, and sufficiently precise enough to render the difference in audibility low enough, then my question has been answered.
Ps.. That also answers my other question.. If it is better, why is it so rare? It requires the system be tailored to the speaker..no easy, turnkey mix and match for sonic preference.
I wonder if my co-wound solution is in any way a closer to turnkey proposition. That is, can the amp drive different speakers identically with co-wind feedback without having to tailor to the speaker? Of course, my solution would require one amp per co-wound coil (I suspect).
Jn
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In the system I designed in the early 1990s individual driver Zobels flattened driver impedance, and both driver eqs were done pre-amplifier. This resulted in a more well damped transient response than just eq'ing the driver as well as making the eq much simpler.
Cheers!
Howie
1. No statistics on that, as it is still extraordinary DIYjneutron said:
2. No need for perfection in that, as the v-drive responses themselves are usually far from it.
IIRC, your co-wound proposal is in effect i-drive for the EMF portion of the load and v-drive for the wire resistance, so it would require similar EQ than current drive.jneutron said:
If you DSP out the frequency response, all that's left is harmonics as a difference between voltage and current drive. Nelson Pass does say large enough 2nd harmonics affect imaging.
I suppose it's possible the difference in EMF braking at Fs could affect the acoustic impedance in the vicinity of the speaker.
I suppose it's possible the difference in EMF braking at Fs could affect the acoustic impedance in the vicinity of the speaker.
The best speakers I have had were the 8" woofer wired full range with critically tuned RC snubber giving flat impedance past 40kHz with tweeter 'bled in' with IIRC 1.15uF (polystyrene) series cap.
It is notable that the likes of Bose 301 8" 2 ways were wired the same way but without the zobel, they sounded dynamic but a bit dirty, my RC network cured this dirt in the Yamaha example I had.
This setup had the best depth imaging, dynamics, clarity and presence of any speaker I have heard with added benefits of amp and voice coils running much cooler.
This also gave the best polarity portrayal of any speaker I have heard which provides depth imaging for miles and 3D surround sound....which can be a 'downside' because of needing to invert signal polarity of some albums or one track of particular albums usually the Top40 track.
The objections to Joe's work on loudspeaker input RC and RLC networks are viewing the concept in a wrong way and the proof is that the amplifier goes louder and runs cooler, ditto the voice coils.
This all comes down to load power factor being near unity which means no amplifier>cable>loudspeaker circulating currents and consequent amplifier output stage slewing and correcting for and absorbing this return energy.
Wiring networks across the loudspeaker input with conjugate impedance to the admittance to the drivers/crossover provides a dump/store for 'excess' energy in first/third quadrants and driver matched impedance local energy source during the second/fourth quadrants, like i said a bit like a water hammer stopper in a hydraulic system.
This 'smooths' the current demands on the amplifier which reduces a swag of amplifier distortion mechanisms and I think this is essentially what is behind the lowered 'subjective' distortion of flat impedance loudspeakers. There are other distortion mechanisms that are 'stirred up' by circulating currents and flat impedance load reduces these also.
Elsinore schematic for reference.
Dan.
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Ummmm
Did we explain yet why driver's acoustic output distortion is reduced with current sensing feedback and not with VFB? Like I showed awhile ago.
??
Why doesnt voltage feedback at the OPS with drver connected reduce the distortion as much as current FB?
And, thus why should not all amp's use CFB for lower speaker distortion? Surely, the cost of a resistor is not too much.
THx-RNMarsh
Did we explain yet why driver's acoustic output distortion is reduced with current sensing feedback and not with VFB? Like I showed awhile ago.
??
Why doesnt voltage feedback at the OPS with drver connected reduce the distortion as much as current FB?
And, thus why should not all amp's use CFB for lower speaker distortion? Surely, the cost of a resistor is not too much.
THx-RNMarsh
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Thanks, this is the best hypothesis I've seen so far. And, yeah, I was assuming one tuned one's crossover to yield an equivalent output as well.
And with that I'm back out of the current vs voltage drive discussion, albeit happy it's a topic more productive than the past few weeks.
As my post above.
Not suitable for typical V designed passive speakers as it exaggerates resonance amplitudes, current mode amp needs to be built into active speaker with resonance nulling custom eq which needs to dynamically compensate/track Re thermal drift according to power levels.
Can you clarify, is current sensing feedback the same as current feedback and are you referring to a low impedance (voltage) amplifier?
Wasn't it stated that a pre filter was required and that it was an invert of the speaker? That means no speaker swapping, it's no longer a turnkey system.
Dan, you are so incorrect I don't know where to start!!!
Actually, I do. First and third quadrant are resistive. You meant second and fourth.
Jn
Yes, the only difference is in harmonic distortion, this depends on speaker used. Current drive is a cure of some non-linearities, not for all of them. Shown by me
Proudove buzeni repro a zkresleni repro
and by others as well, I assume Esa has some IM measurements.
The more complex solution of speaker non-linearities is by Wolfgang Klippel.
It's v drive across the entire range, as the diff signal ignores all non dissipative energy transfer. At LF it ignores velocity based voltage generation, and it ignores vc inductance at all times. My suspicion is that it will produce constant amplitude response without eq. Whether that is a good thing or not, nobody has tried it yet that I am aware. I've been thinking about how I could co wind on an 8 inch full range.. I thing running two tap wires small enough to be interstitial, and bring both out. Both added will give the exact two layer vc voltage, and the neatest thing is I think we can figure out how measure the tap wire resistance. If we run equal and opposite DC currents in the tap wires, they will provide no force but we can measure the DC V drop. That will give us direct feedback on the voice coil temperature. We can comp out compression and monitor to stop over temp.
I also figured out how to center the vc during reassembly without removing the dustcap. Four thin nomex strips in the gap, long enough to extend past the spider, put coil in, glue spider everywhere except where the strips are. After cure, remove strips and finish gluing. Teflon strips will work as well, and the glue won't stick.
I call it as I see it..
Cheers, John
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Well, what I was to say is that drive impedance doesn't change any "magic" additional amount of phase (or lack thereof), spl mag and phase response strictly follow the rules of a weakly nonlinear mininum phase system. If we measure a certain driver voltage response (or current, for that matter) we always will get a SPL frequency and phase response strictly corresponding to it and nothing else.
The drive impedance does play a role, though, for the inner relationships of distortion currents and voltages and this will be reflected in different SPL distortion profiles.
Same question not clear the difference is understood, this thread has become an embarrassment.
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