System Damping Factor

reeltrouble1

I have read that a total system damping factor of 10 is considered acceptable although the higher the number the better. My question is when calculating the total system for damping the nominal impedance for the speakers and speaker wire is to be considered, do you consider all of the wires connected from the amp to the speakers or just one, if just one then which one in a seven ch system.

It would seem to me you need to figure all of the speaker wire runs then double the total distance for impedence out and back but I am not sure.

HBombToo

If we put this into a Damping Factor perspective:
(an 8Ohm speaker)/(.08 Ohm Output impedance)= 100 (Not bad but there is alot better but does it really matter over 50? )

Now use 10 feet of cat5 @ ~ .3 Ohms resistance and add it to your .08 Ohm output impedance we have ~ .38 Ohms and at a casual glance we would say... ehh, no problem BUT look what happens to damping.

8.0 Ohms/(.08+.3) ~21 which is way down from 100. as an aside The reason I'm lumping the cat5 resistance with the amp impedance is the Q(damping) of the speaker itself is guided by the dc resistance of the voice coil which we are not changing.

NOW:
The DC resistance in a 10 foot(same as above for the cat 5 example)stranded 12 awg is ~.015 Ohms

so doing the same damping calculation:

8/(.015+.08) ~ 83.4 damping factor. ok now... a lot better than 21 eh.

"I posted this on AK and here at one time but did notr get much interest. I am a firm believer that line resistance must be rolled into the calculation."

HBomb

dragon1952

Wow....very impressive, 'Bomb!

reeltrouble1

Henry,

Then taking the spec of the amp damping factor say it is 1000 into an 8 ohm speaker you would divide 8/1000 then multiply by the impedence of one speaker wire. I believe you have impedance going out and back so for a 10 ft. run you have 20 x impedance per foot?

Seems I am missing something here. Back up a moment, Damping Factor of an amp is the ability of the amp to absorb/dissapate/get rid of/ energy once a frequency to a driver stops so that the driver does not continue to vibrate. Have I at least got this right.

But to get the total dampening factor of the system you must figure the wire impedance into the equation. Then would you agree with the statement that anything over 10 is acceptable but the higher the better?

If you have a long run then the total system damping factor is going to be different than a short run, hence the need for larger wire on longer runs? It would seem this would mostly affect the bass driver.

HBombToo

Originally posted by reeltrouble1


Seems I am missing something here. Back up a moment, Damping Factor of an amp is the ability of the amp to absorb/dissapate/get rid of/ energy once a frequency to a driver stops so that the driver does not continue to vibrate. Have I at least got this right.

But to get the total dampening factor of the system you must figure the wire impedance into the equation. Then would you agree with the statement that anything over 10 is acceptable but the higher the better?

If you have a long run then the total system damping factor is going to be different than a short run, hence the need for larger wire on longer runs? It would seem this would mostly affect the bass driver.

Point 1 is near perfect so you understand the concept. for your own good look at the definition of damping.

What is an acceptable damping factor is something that I TRY and continue in my ignorant attemt to figure out. I'm not sure where the limits should be set. My point in the calc is that wire impedance must be figured in because it is the only variable.

YES... you got it but don't want to admit it:p damping changes due to line lengths.

We just brought this up again so I'm not sure where we should take it.

twin

reeltrouble1

Well, I got my answer so I am satisfied on this end, and it supports the wire camp that believes wire is important and makes a difference. Whether a person hears the difference is the point of contention.

Alot of our threads talk about pounding in more and more watts to a speaker, not necessarily a bad thing but there is more to consider.

Thanks Hbomb

John K.

RT, a good discussion by speaker designer Dick Pierce on damping factor is found here . The effects of damping factor on either damping at resonance or fluctuation in response with swings in speaker impedance wouldn't appear to be of any audible significance until down into the single digits. So the statement that 10 is adequate would appear to be realistic, but the "the higher the better" claim wouldn't appear to be valid from the standpoint of audibility.

The impedance(both ways)of the speaker wire has to be included in the damping factor calculation, but commonly suggested gauges for use at various run distances in home use don't create a problem. About the only situation likely to cause some audible problem would be with some tube amps having output impedances of several ohms, leading to damping factors on the order of 1 or 2. Even here however tube enthusiasts describe this problem area(together with the 2nd order harmonic distortion some tube designs offer)using attractive adjectives such as "sweet" or "warm".

HBombToo

Originally posted by John K.
So the statement that 10 is adequate would appear to be realistic, but the "the higher the better" claim wouldn't appear to be valid from the standpoint of audibility.

I run 6dj8's through solid state on two different systems and I realized its all a matter of your needs.

HBomb