Speaking of audiophools

A simple little test. Tap on the woofer with various load resistors. I have done this in a way, but not thoroughly

greg

For the audiophools with their assinine view of loudspeakers...

This model is courtesy of "analog", 2002.

...Jim Thompson

I'm aware of that and in fact I have some active speakers driven from current sources. They avoid the compression encountered with varying voicecoil temperatures, but pose new problems, which are difficult to overcome. In fact the tweeters sound much better driven this way. Also the treble doesn't roll off because of the voicecoil inductance. But it is risky, too loud and a thermal runaway burns out the coil.

We were talking about the possibility of identifying different cables, and even if 0.8dB usually don't make a difference, the rising Q might be identifyable.

It's a *motor* for heaven's sake. Hardly resistive ! Back emf and all.....

Add in the crossover network and you have a potentially really unpleasant laod. I've measured some and you get some wacky phase angles.

Graham

Cue Don Pearce on the subject.

Graham

Yes it works like a microphone. Your point ???

Graham

You can hear the effect of damping by way of damping factor. This driver is in a proper cabinet of course. I'm sure everybody has tapped on a speaker with no wires attached, but with a short across it, it sounds alltogether different. Of course many coiled devices are shipped shorted.

greg

A loudspeaker is usually designed for zero Ohm generator impedance. Putting an added resistance between the amplifier and the loudspeaker will of course affect the transfer function of the speaker. However, as you point out, one has to consider the proportions between the added resistance and the resistance of the speaker (drivers) itself.

Please note, though, that an (resonable) added cable resistance will only slightly affect the transfer function of an "ordinary" (parallel) filter, whereas variations in the speaker drivers' resistance (as discussed earlier) are much more devastating.

$8000 for a 2 meter pair?!?!?!?!? Your out of your friggin mind. I'd propose to use copper bus bar - Much cheaper and you eliminate the inductance effects by not having the cable twisted..sheesh, talk about picking the fly sh*t out of the pepper.....

John

On Tue, 27 Jun 2006 08:35:54 -0700, Jim Thompson Gave us:

important

and

None of the "voice coils" in modern speakers are directly attached. You need to include not only a crossover circuit, but THE EXACT SAME crossover circuit used for any given driver array.

Sum Ting Wong

On Tue, 27 Jun 2006 17:44:18 +0100, Eeyore Gave us:

You were supposed to take note of the back force to your applied force for any given R value.

You won't catch me tapping on my woofers though.

On Tue, 27 Jun 2006 16:59:47 GMT, snipped-for-privacy@pitt.edu (GregS) Gave us:

Baloney! Many capacitors are shipped with a shorting wire, particularly large sized HV caps.

I have never seen a "coil" or transformer winding, or bare 12" speaker driver get shipped with a shorting wire. There is just no need for it.

On Tue, 27 Jun 2006 13:23:52 -0400, John Hudak Gave us:

There is no "inductance effect". Sheesh indeed.

I have seen multimeters with a switch position for "off/transit" that shorts the coil to minimize the needle being bounced around.

- Don Klipstein ( snipped-for-privacy@misty.com)

I think AVO model 8s did that too.

Graham

You betcha. Take a nice old-time 10 to 100 uA meter movement and wiggle it around both shorted and unshorted and see what happens. The short increases the damping bigtime. Visual proof.

On Tue, 27 Jun 2006 20:22:58 -0700, Wes Stewart Gave us:

Jeez. A simple wire across a child's DC motor shows the same thing.

When permanent magnets are involved, and coils of wire... a closed loop means that motion will cause current flow, and movement will be resisted by way of back EMF.

Hell, I knew that at five years of age, back in the sixties.

And any cable resistance or reactance comes in series with Rvc, the voice coil resistance.

I once got (from an audiophool, who got unhappy) rather expensive cable. Thick conductors (about 5 mm round) but also a 3 cm distance between the conductors (mostly air). Nice dark red color.

I wonder if the inductance could 'do' anything noticeable at say 5 KHz. Not that I even tried to hear a difference.. I later made another audiophool happy with them and went back to two different cheap cabels, one thin and short, the other longer and fatter.

Thomas

How do you compute inductance of a loop?Can we estimate impedance of this wire loop at, say, 40 kHz?