Inductance and Speed

[Charles Warwick]

I just finished reading that adire article on the 'speed' of a woofer and the relationship to the weight and inductance of a speaker.
so I am wondering about the bfm woofers of choice...
I just grabbed a couple and looked up the inductance:

Kappalite 3015LF .92mH
Magnum 15lf 1.21mH
Definimax 4012 1.17mH

Is this type of inductance typical of what people describe as a 'fast' woofer? Somewhere around the range of 1 mH? I have not yet built/heard any of the Tubas or Titans, so I couldn't say how to describe them, but I do know how a 'slow' woofer sounds... From what I understand about horn loading the mass of the air in front of the woofer is 'added' to the mass of the cone, but as stated in the article it is not about the mass, but rather the inductance of the voice coil in the magnetic field, so I presume that the horn loading shouldn't have an effect on the 'speed' of the overall speaker?

Any ideas on what kinds of inductance and/or BL factors are considered 'fast'?

[Ron K]

This has been discussed in detail before but the thread has been pruned of the responses.

Not everyone is in agreement with Dan Wiggans from Adire Audio.

[Sydney]

Not everyone is in agreement with Dan Wiggans from Adire Audio.

Indeed, and this a private business forum not a peer group for evaluation of proposals or thesis.
Not all claims ( especially those internet based ) are subject to accepted scientific methods.

[Bill Fitzmaurice]

Is this type of inductance typical of what people describe as a 'fast' woofer?

Yes, because these are all wide bandwidth extended range musical instrument/pro-sound woofers. FWIW there's no such thing as a 'fast' woofer, what's generally referred to as such are woofers that have good response into the midrange. That's generally not the case with Le values of 1.5 or more.

[Charles Warwick]

Oh wow, that generated more than I was hoping for.
But regardless, so it seems to me based on what Bill said is that the inductance of a driver is more characteristic of the extended response of the woofer into the midrange; but that makes sense as higher inductance values are like a using a higher mH value for a low pass x-over, and lower values give a response that is less self-inhibited... since the woofer itself is an inductor, it should have a point where the impedance rises and response drops, right?

Hmm...so really the sound of a a'fast' woofer is just what people characterize as an extended range driver.

Okay...Thanks for the replies! I think I have a better grasp of things.

Although, it seems things are quite debate-able around here. heh...

[Ron K]

Hmm...so really the sound of a a'fast' woofer is just what people characterize as an extended range driver.

For some yes. For others transient response is a bit more than just speed. It's a relationship to signal in vs signal out and how accurate the output of a specific driver is compared to the driven signal in the time domain. I think a lot of the confusion come into lay when describing the transient response of a loudspeaker. Since it's an electromechanical device both definitions apply not just the electrical or just the mechanical.

So fast for others is a measure of accuracy where speed ,acceleration, deceleration stop and reverse back the other way are all concerned.Those things are influenced by electrical and mechanical forces. Dampening ,spider ,surround ,cone flex,air mass load etc. and electromotive force and back electromotive forces.

Things like excessive overshoot can make a bass driver sound like horrid crap on a fast attack envelope like that of a kick drum. It may come out of the hole with blazing speed all is good on the initial attack but if it lingers and doesn't stop in the required amount of time because of overshoot or ringing it will make that signal sound like crap.By the same token you wouldn't want to gate an organ sound either.

So accuracy is something a lot of good FOH guys can hear and something a lot of musicians can hear as well.Along with tone ,pitch etc.I personally believe fast to be far too subjective of a term to apply to audio.I prefer accuracy in the time domain.

[Bill Fitzmaurice]

Things like excessive overshoot can make a bass driver sound like horrid crap on a fast attack envelope like that of a kick drum. It may come out of the hole with blazing speed all is good on the initial attack but if it lingers and doesn't stop in the required amount of time because of overshoot or ringing it will make that signal sound like crap.

That's mainly the case with cheap drivers with high Qts/low Bl values, and you won't find those used in quality gear. We're talking $29.95 woofers/Gemsound (lack of) quality cabs here.