Low impedance = better sound?

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#22
lowmass said:
In building ribbons it often seems the low resistance designs sound somehow better than the high resistance designs
And this is basically at the same mass ( same foil thickness just more smaller runs of it in higher resistance designs)
No real scientific eval of this, it just seems that way often when playing around with making different designs.
Also not saying the lower resistance designs are actually technically better, they just seem to have some sort of desirable sonic quality.

It may be interesting to note that possibly the favorite ( by many) Apogee ribbon were their very low resistance designs. Amp eaters but......

Im not at all sure this has any connection to what Op is talking about
Click to expand...

The resistance of the VC limits the damping factor, it limits it from all this DF of 1600 crap.
 
#24
If the 8 ohm version has twice the number of turns on the voice coil as does the 4 ohm version, the back EMF of the 8 ohm driver will be twice that of the 4 ohm driver.

This will result in the amplifier applying more negative feedback to the 8 ohm driver than it does to the 4 ohm driver, particularly in the bass region.
For both to obtain the same SPL (for the sake of comparison) the 8 ohm version is more likely to be overdriven at the very lowest frequencies as it needs to be driven at a higher signal voltage. The result is frequency doubling when displacement becomes limited.


C.M
 
#26
in this definition from Eminence


BL

Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!


there's no mention of coil length.....?
 
#27
"If the 8 ohm version has twice the number of turns on the voice coil as does the 4 ohm version, the back EMF of the 8 ohm driver will be twice that of the 4 ohm driver."

"the 8 ohm version is more likely to be overdriven at the very lowest frequencies as it needs to be driven at a higher signal voltage"

I don't think the latter necessarily follows, other factors in a design may influence things.

Back e.m.f., from memory, is given by;

V = - L . d fi/dt. It will be greater with the lower Z, and hence back e.m.f. will also.

"Expressed in Tesla meters," - Implicit in this is length, and yes, within the gap.

I've never seen any mention of weightlifters BTW.
 
#34
It is well known in the professional speaker design community that BL, the 'motor factor' is comprised of flux density and coil length.


F = BIL is universally taught at college; units;
Newtons, Wb/m^2, Amperes, metres.


I studied that 45 years ago and it hasn't changed.
 
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