Full range Open Baffle with Current Drive

[knutn]

With current drive you don't need any series resistance, so all the power is delivered to the driver. And you can manipulate the Q value actively or passively, as e.g. in Pass' FIRST WATT F1, where a resistor in parallel with the amplifier output does the job.

[Nelson Pass]

Originally Posted by el`Ol

I also think series resistors are bad per se. My main 3-way system runs with a low Qts wideranger and 3.3 Ohm series resistor that brings it to Qts = 0.5. Sounds much less stressed, much more relaxed.

I have run into this observation more than once - Jon ver
Halen has commented that series resistance "sucks the life
out" as an example.

And yet Thevenin equivalency is clear that there is no
difference between a perfect voltage source in series with
a resistor and a perfect current source in parallel with the
same resistor. If there is a difference then we have to
presume that there is either a failure in the perfection of
the cs and/or vs or a flaw in the test / listener.

[hitsware]

> "sucks the life out"

In my experience it not only sucks the life out,
it also mangles the remaining cadaver.
However, a bypass cap seems to raise the dead
to a great extent.

[el`Ol]

Originally Posted by el`Ol

I also think series resistors are bad per se. My main 3-way system runs with a low Qts wideranger and 3.3 Ohm series resistor that brings it to Qts = 0.5. Sounds much less stressed, much more relaxed.

Sorry, I didn't post carefully enough. Wanted to say "I also don't think series are bad per se. But that too high values "suck out life" is true. The character of this driver before was a bit what a naim lover calls "energy", I don't like that kind of sound. I didn't make such experiments with other drivers, but with this driver +/- 0.3 Ohm was clearly audible (in the midrange, I don't speak about bass response). Are there different paper mixes that demand weaker/stronger motors?

[nicoch58]

Knuts the new seas will be in the 125$ range....

Papa, Watt's next?

[Vix]

Originally Posted by Nelson Pass

And yet Thevenin equivalency is clear that there is no
difference between a perfect voltage source in series with
a resistor and a perfect current source in parallel with the
same resistor.

"In theory, there is no difference between theory and practice. But, in practice, there is." -Yogi Berra

By the way, I noticed that even simple L/R circuits that are used in series with the fullrange speaker in order to 'correct' their frequency response degrade the sound. Theoretically, they should be just shelving frequencies above the certain point, but...they suck some life out the music. That's why I prefer current source amps, and I (again) removed the feedback resistors (and CCS modulation) from my Zen V9.

[knutn]

Originally Posted by Vix

"In theory, there is no difference between theory and practice. But, in practice, there is." -Yogi Berra

By the way, I noticed that even simple L/R circuits that are used in series with the fullrange speaker in order to 'correct' their frequency response degrade the sound. Theoretically, they should be just shelving frequencies above the certain point, but...they suck some life out the music. That's why I prefer current source amps, and I (again) removed the feedback resistors (and CCS modulation) from my Zen V9.

Have you tried active equalization instead of simple L/R circuits? What kind of speakers do you use, and how would you describe the difference between current drive and voltage drive?

[Vix]

Yes, I tried equalization instead of simple L/R circuits. They do work, but any such circuits would require to be "sandwiched" between two buffer blocks for the best effect, which works well if you use J-fet (or even tube) buffers (I do not prefer opamps). My Open baffle (120x50cm-flat baffle) consists of The Eminence Beta 15 for the bass and Visaton B200 for the highs. It is biamped, so that the the Beta is driven by a voltage source amp (Sony TA-N511) while Visaton is driven by Zen V9 without feedback, i.e. current amp. The whole thing is now actively crossed over, though during the last two years I have been playing with various crossover combination (slopes, frequencies, active, passive, hybrid). The difference, V/I: Current drive changes the damping (hence bass) and the tonal character of the driver, often for the better. In my case, only the fullrange (above 150 Hz) is driven with the current amp, so no effect on the bass here, but some nice things happen in the upper registers as well. Somehow it sounds more musical, there is more "air', it just sounds more natural and less strident. Also, there is a bit of compensation here as well, in order to correct for fullrange nasties. There is Zobel (C+R) in parallell with speaker terminal (B200) to correct for its rising response.
On the paper, you would see that Zen V9 without feedback has actually more distortion than with feedback. However, at normal volumes I do not find it distracting. To me, connecting the feedback (this making it a conventional voltage amp) makes it sound more 'solid' and loose that 'breath of air that makes some instruments sound so lively....
I know it's all subjective, but...

[knutn]

Thank you for your feedback. Your description is a further encouragement for current drive!

[Nelson Pass]

Current source amplifiers are great for people who want to
play around with stuff. Not so great for those who just
want "plug and play"