damping of series vs parallel

[lopan]

Would (Can) someone please explain why the electrical damping is the same for drivers in parallel as in series. Assuming the drivers are the same in the same cabinet.

In open loop ( no amp and drivers resonating) in series we would have twice the voltage as in parallel and in closed loop (accross a minimal impeadance, Zo) we will have twice the current in parallel as in series.

But if Zo is small as it is then in both case we will crrent limit and voltage generated at the drivers will be I*Zo and power dissapated is I*I*Zo and therefore in parallel power dissapation would be 4 fold.

I know I am making a mistake but I am not seeing it. Your insight is appreciated as is any equations.

Cheers

[sbrads]

I'm unconvinced the electrical damping is the same. JBL don't think so when discussing twin woofers.........Quote.........

"We recommend that you
avoid connecting separate
woofers in series. Because the
amplifier-damping factor (the
amplifier’s ability to control
the motion of the woofer) is
expressed as a ratio of terminal
impedance (the sum of speaker
impedance, wire resistance and
the D.C. resistance of any
crossover coil connected to the
woofer) to amplifier-output
impedance, connecting separate
woofers in series reduces the
damping factor of the amplifier
to a value less than 1. This will
result in poor transient response."

I tend to agree unless someone can show otherwise.

[SY]

If the drivers are identical, I think that symmetry forces the damping to be the same.

[Fixxer]

Originally posted by sbrads
I'm unconvinced the electrical damping is the same. JBL don't think so when discussing twin woofers.........Quote.........

"We recommend that you
avoid connecting separate
woofers in series. Because the
amplifier-damping factor (the
amplifier’s ability to control
the motion of the woofer) is
expressed as a ratio of terminal
impedance (the sum of speaker
impedance, wire resistance and
the D.C. resistance of any
crossover coil connected to the
woofer) to amplifier-output
impedance, connecting separate
woofers in series reduces the
damping factor of the amplifier
to a value less than 1. This will
result in poor transient response."

I tend to agree unless someone can show otherwise.

That doesn´t make any sense. When you connect two woofers in series you double the load impedance -> double the damping factor.

[lopan]

The quote may be an accurate qoute but who ever said it is very wrong. Damping for a single driver is the speaker impedance versus all the other impeadances in the circuit (line + filter + amp) not summed with some of them.

And as stated above series would if anything increase the damping though I don't belive it changes it. But I don't have a succint explanation why.

The simple questions are the hardest and this one is of paramount importance and we don't know.

John K writes "The two driver is series will generate twice the back EMF but that voltage will be applied across the two VC's impedance. Twice the back EMF across twice the resistance yoields the same reverse current and same damping. "

I have a lot more to say but i have to go for a while

Take care

[SY]

And as stated above series would if anything increase the damping though I don't belive it changes it. But I don't have a succint explanation why.

Consider a soure that has an output voltage of V across a load Z. V can vary with time, the source can have a Thevenin or Norton character, whatever, you just have V across Z.

Now, double that voltage and series two Zs. The voltage across each Z is still V. If that is the case, the damping has remained unchanged.

A quick simulation in Calsod showed exactly that- the frequency response did not change a bit, therefore damping stays the same.

A reasonable question, and one that John K raises, is what happens when non-identical drivers are put in series...

[sbrads]

The electrical damping factor on the back EMF may be the same for nice steady tones driving both identical series woofers, but it's unlikely to be the same in the real world because of one experimental observation.....

If you tap your finger on a woofer cone you'll probably hear a resonant thud, but short the terminals out and you get a shorter more damped and quieter sound. Put 2 in series shorted out and tap one cone and it will be resonant again but not as bad the open circuit version. This is because the generated current flowing is reduced by the other coil which in this situation just look like an approx 6R series resistor. Therefore any resonances etc that are different between the 2 woofers won't get the full damping. No problem though if everything is identical between the 2 woofers, but what chance of that is there in a real speaker cabinet with real woofers?

[lopan]

Originally posted by SY


Consider a soure that has an output voltage of V across a load Z. V can vary with time, the source can have a Thevenin or Norton character, whatever, you just have V across Z.

Now, double that voltage and series two Zs. The voltage across each Z is still V. If that is the case, the damping has remained unchanged.

A quick simulation in Calsod showed exactly that- the frequency response did not change a bit, therefore damping stays the same.

A reasonable question, and one that John K raises, is what happens when non-identical drivers are put in series...

This seems to demonstrate the that drive operates the same but not that it damps the same. take for instance a pulse after which there is no drive voltage instead here the drivers act as the source and the amps as the loads. Thanks for your time

Take care

Originally posted by sbrads
The electrical damping factor on the back EMF may be the same for nice steady tones driving both identical series woofers, but it's unlikely to be the same in the real world because of one experimental observation.....

If you tap your finger on a woofer cone you'll probably hear a resonant thud, but short the terminals out and you get a shorter more damped and quieter sound. Put 2 in series shorted out and tap one cone and it will be resonant again but not as bad the open circuit version. This is because the generated current flowing is reduced by the other coil which in this situation just look like an approx 6R series resistor. Therefore any resonances etc that are different between the 2 woofers won't get the full damping. No problem though if everything is identical between the 2 woofers, but what chance of that is there in a real speaker cabinet with real woofers?

Doesn't still answer the question but it is an excellent thought this might be a potential clear advantage to parallel configurations.

Heres my issue my mids are very stable through therie operating rage at 4.9 to 5.1 ohms therfore in parallel 2.5 ohms and series 10 ohms. the amps are meitners w/67 volt mains and max current output of 35 amps (not continuous probably more like 18 amps. refering to Otawa's (probably misspelled) contention that impedance drops to 1/6th of nominal impedance we get this

Parallel max i = (67-2)/2.5 * 6 =~ 170 amps

Series max i = (67-2)/10 * 6 = 39 amps

parallel seems like a better option presently the system is parallel and it does bleed out well below pushing the preamp (also meitner).

But to generate a comparable crossover to just see will cost about 300 buckc it is all 8 gauge northcreek coils and their caps not to mention tearing the speakers apart and rebalancing the tweeters.

Thanks for your thoughts

Take care

[SY]

This seems to demonstrate the that drive operates the same but not that it damps the same. take for instance a pulse after which there is no drive voltage instead here the drivers act as the source and the amps as the loads.

If the voltages are the same independent of the source resistance of the drive, then the damping is the same. Here's another way to look at it: level shift the drive source so that the top and bottom of the series string are driven in equal but opposite directions (instead of going V -> 2V, we're going to V -> +/-V). Note that I have not specified what the source Z looks like, only that it is such that you end up with 2V in total across the pair. The junction of the two drivers is at ground since the two drivers are identical. It's easy to see that the top driver sees the same source Z that it did for the case where it was driven directly by V.

[lopan]

I am onn my way to the gym but I am not sure. I will have to think about it but if the amps are taken out of it there is no damping (electrical) -- the damping characteristic is due to i not v. And we must be able to define the power dissapation in an equation such I squared R, where R is the output resistance of the amp.

I appreciate your input


Take care