[G Georgopoulos]

Hi a friend of mine told me the damping factor is reduced by the cable resistance.is this the case what do you think?

the way i see it is

damping factor = Rload + Rcable / zout

the above formula actually increases the damping factor!!

but because the Rcable is not Rload of the voice coil it cancels itself

so

we have now damping factor= Rload / zout

which is not reduced as my friend told me

what do you think??

[*Scotty*]

A simple test could be done by inserting a 0.3 ohm 30watt resistor inline between the power amp and the loudspeaker, you could scale the resistor up to 1ohm and see what you hear if the results of the 0.3ohm resistor test were inconclusive.
Scotty

[Davey]

Your friend is correct.

Damping factor is equal to Zload / (Zout + Rvc)

Zload being the driver nominal impedance.
Zout being the amplifier output impedance.
Rvc being the DC resistance of the voice coil.

Cable (series) resistance adds to the denominator of the calculation so it will reduce the damping factor.

Cheers,

Dave.

[G Georgopoulos]

Your friend is correct.

Damping factor is equal to Zload / (Zout + Rvc)

Zload being the driver nominal impedance.
Zout being the amplifier output impedance.
Rvc being the DC resistance of the voice coil.

Cable (series) resistance adds to the denominator of the calculation so it will reduce the damping factor.

Cheers,

Dave.

Zout is internal impedance of the amplifier,how come you add to it the Rvc of the voice coil??...

your calculation ie with an Rvc of 4ohms and Rload of 8ohms will produce a damping factor of 2 unreal!!!

[Davey]

Rvc and Zout (and also cable resistance) appear as series elements in the analysis.
Yes, a driver with a nominal 8 ohm load and Rvc of 4 ohms would yield a damping factor of 2.

This might not be the definition of damping factor you're used to seeing in specs.  Many times amplifier manufacturers just make a simple calculation of 8 ohms divided by Zout.  The number is higher in that case, but it's still the same configuration.

Regardless of the calculation used, adding cable resistance reduces damping factor.  If you think about it intuitively you'll realize that must be the case.

Cheers,

Dave.

[Speedskater]

For completeness three good Dick Pierce papers on the subject:

'Damping Factor: Effects On System Response'
by Dick Pierce
http://www.audioholics.com/education/amplifier-technology/damping-factor-effects-on-system-response

different edition
'Damping Factor: Effects On System Response'
Dick Pierce
Professional Audio Development
http://www.cartchunk.org/audiotopics/DampingFactor.pdf

'Damping: Loudspeakers In Series'
Dick Pierce
Professional Audio Development
Hanover, MA
“Debunking audio myths for over a fiftieth of a millennium”
http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf

Dick Pierce - Audio Topics
http://www.cartchunk.org/audiotopics/