Does every cone have ONE right motor? - diyAudio
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Old 19th May 2010, 09:59 AM   #1
el`Ol is offline el`Ol  Germany
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Default Does every cone have ONE right motor?

Hello all!

I once experimented with a light cone, strong motor driver and for my taste it sounded "stressed" or "overdynamic", so I experimented with series resistors. I found that differences of 0.3 Ohm were clearly audible and at 3.3 Ohm there was a point where I had exacly the relaxed sound I like, neither stressed nor boring (what happened with too large resistors). I am not talking about bass response in a certain enclosure (I used OB and sealed), just about midrange performance, and the effect remained the same when adding a large series capacitor.
Recently I stumled on reports about the 8" Tangbands where (I don't know whether it was the same person) was said the "stronger" one had good transients with percussive sounds and the "weaker" one was more for easy listening.
Are these singular effects, or do they appear with all fragile paper cones?

Oliver
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Old 19th May 2010, 09:44 PM   #2
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Hi Oliver,

did you adjust volume for same voltage across the voice coil when listening ?

Maybe there is an effect when going from voltage towards current drive.

The higher the resistance is, the lower is the frequency dependent influence
of VC inductivity e.g.

Influence of cone resonances on impedance are flattened relatively.

VC velocity vs. frequency may change significantly dependent on the
drivers motor/VC design.

I can imagine that there might be drivers which sound better using a
resistor in series.

Regards
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Old 19th May 2010, 10:13 PM   #3
tinitus is offline tinitus  Europe
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el`ol
its not uncommon to be like you say, at least its my experience too

But dont forget that high or low Qts changes things
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Old 19th May 2010, 11:40 PM   #4
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The Replikon builders have an interesting idea about optimizing, but it's broader than the motor / series resistance.

They do not use box alignments. Instead, they find the ideal box volume empirically -- the volume that gets the driver / box to sing (with a given amp / room). When the sound "locks in," that's the ideal volume for the driver / amp / room. (They use blocks to vary the volume, just as you're using different amounts of series resistance.)

www.hornlautsprecher.de - solutions in sound

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Old 20th May 2010, 06:38 AM   #5
el`Ol is offline el`Ol  Germany
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Quote:
Originally Posted by LineArray View Post
did you adjust volume for same voltage across the voice coil when listening ?
Regards
I adjusted the volume subjectively

Quote:
Originally Posted by LineArray View Post
Influence of cone resonances on impedance are flattened relatively.
And what does that mean?
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Old 20th May 2010, 12:11 PM   #6
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I do not know either what that means ...

Some wild speculation:

I think it depends on the mode shape of the membrane
resonances under question.

A peak in VC velocity can nevertheless be associated
with a dip in frequency response, in those cases voltage
drive will worsen things.

If the impedance peak is associated with an efficiently
radiating membrane mode however the peak will be less
pronounced using voltage drive.

Constant voltage drive smoothes the sound pressure peaks
for efficiently radiating resonances in VC velocity,
while notches in sound pressure associated with VC velocity
peaks are pronounced.

Constant current drive will act vice versa. Sound pressure
peaks associated with impedance peaks will be pronounced.
Sound pressure notches assotiated with impedance peaks are
smoothed.


Maybe "constant power" is a way of muddeling through at best,
neither voltage drive nor current drive.

The less damped a membrane is - i think you reported mainly
from experience with lightwight paper cones - the more
audible this small changes could be.

With a well damped cone having smooth impedance vs. frequency
a resistor in series might not be audible to that extent.


Regards
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Old 20th May 2010, 05:07 PM   #7
GM is offline GM  United States
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Greets!

Qts = ~0.312 gives the maximum bass extension for the minimum box size, so it seems reasonable to me that this yields the most balanced summed (Fs/Vas/Qts) to diaphragm loading/damping through its mass controlled (~flat) BW regardless of box loading type, so cone mass per se is irrelevant, a point that many can't seem to understand, especially when considering horn driver spec requirements.

GM
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Old 23rd May 2010, 12:59 PM   #8
el`Ol is offline el`Ol  Germany
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What is the sonic difference between a current- and a voltage-driven Lowther?
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Old 23rd May 2010, 02:35 PM   #9
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6moons audio reviews: FirstWatt F2

Some seem to praise it ... have no own experience.

But in that article i read that laying a resistor "across" (which means parallel?)
the terminals is needed for optimization when using current drive ...

That would mean "no pure current drive" for optimum result and
would point towards the same direction as your finding.
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Last edited by LineArray; 23rd May 2010 at 02:44 PM.
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Old 23rd May 2010, 03:04 PM   #10
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An introduction to current source amplifiers and fullrange
high efficiency speakers from Nelson Pass:

6moons audio reviews: First Watt - An Introduction to the Concept by Nelson Pass
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