Speaking of audiophools

OK, I am perfectly open minded here, and expect to be corrected by learned experts when I say something wrong due to my ignorance.

Resistance of 12 gauge wire is 1.5883 ohms/1000 ft. For a 20 foot run, you get 1.5883/1000*20 = 0.03 ohm.

For 6 gauge wire, its resistance is 0.3951/1000 ft, so the resistance of 20 ft of it would be 0.3951/1000*20 = 0.007902 ohm.

If the speaker has impedance of 8 ohm, then the difference between total impedance of two circuits is

(8+0.03)/(8+0.007902) - 1 = 0.0027 or 0.27%.

If I am not mistaken, it amounts to 0.01 decibels, which is way below any possible human ability to hear difference.

"Eeyore" wrote in message news: snipped-for-privacy@REMOVETHIS.hotmail.com...

Right. And that means we want to keep the speaker cable resistance below maybe 0.5 ohm, which is not difficult. If I calculate correctly, you're OK with 15 feet (both ways, totaling 30 feet) of #22 wire, or 50 feet of #18. That will be flat to 1 dB.

Note to the mathematically challenged: We're not comparing 5 ohms vs. 100 ohms. We're comparing (5.0/5.5) vs. (100.0/100.5), or 0.91 vs. 0.99, or, in decibels, -0.83 to -0.04. Flatness to within 0.8 dB is generally considered very good.

we are comparing 100+5 with 100+5.5

And indeed your example of 12 gauge wire over 10 ft is absolutely fine.

Try using say 18 gauge and a 20 ft cable ( 40 ft of wire ).

Graham

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I didn't read that thread. Been having trouble with the broadband. I reckon I can let the issue sleep.

Graham

can let the

'Cause you don't understand ?:-)

...Jim Thompson

can let the

Well, I imagine you were anticipating using an I to V converter ? I didn't fancy reading the whole thread to find out though. You can have a bit of trouble with them due to cable C if you're not careful.

Graham

What am I supposed to find there?

On Tue, 27 Jun 2006 04:50:28 +0100, nospam Gave us:

Man's best speaker cable?

But this is not the whole lunch. The speaker has a complex impedance and a real resistance in series will not only affect the volume level, but the resonance frequency(lower) and especially the Q at the resonance, which will increase. This might really be audible. The speaker is a motor and relies on its back-EMC being shunted by the amplifier. If an amp has a "damping factor" of 400, it means its interiour resistance is 8/400= 20mOhms and this is augmented to 520mOhms. If there is little mechanical damping as you find with high quality speakers mounted in bass-reflex enclosures, the misalignment will result in a different, more "boomy" bass response. In expensive speakers a lot of money is spend for very low ohm air coils, which is wasted in this case.

This has been verified, sorry I don't have a citation. Anecdotally, I once designed an audio preamp with 2 paths. One was just "normal" with a distortion level around 0.005%, the other had a CCD in the path, with a distortion level of 0.05%, almost all 2nd harmonic. A couple of reviews commented that when using that path the sound was noticeably "warmer" and "more pleasant".

Regards Ian

I have a speaker design book dating from the 1950s where low damping factor was intentionally examined as a method of 'augmenting' the bass response by not damping resonance so well. The effect is quite dramatic with the output Zs of the day.

Graham

This isn't the whole lunch, either. Consider that the voice coils (usually) are wound with copper wire, whose resistivity increases by ~0.39% per degree C. It has been shown (by me and others), that the temperature of the voice coil easliy reaches 150 degrees C or more during "heavy" playing. This means that the resistance of the voice coil can easily reach up to ~150% of it's nominal (20 degrees C) value... Put these figures into the calculations of (bass reflex or closed) loudspeaker boxes and passive filters (and don't forget that midrange and tweeter enclosures are (in most cases) closed loudspeakers, too) -- and the sub-ohmic differences between various speaker cables will no longer look *that* impressive.

Eh?

With 0.5 ohm cable resistance, at the freq. where the speaker Z is 5 ohms, signal level is (5.0/5.5).

At the freq. where speaker Z is 100 ohms, if there is one, signal level is (100.0/100.5).

Voltage divider equation.

If you want a fantastically high damping factor, then you need big cables. But they do not need to be expensive. Plain wire, of sufficient size, is just fine.

As I understand it, there is considerable dispute whether such a high damping factor actually makes any difference.

Good point!

I was also wondering... How can a super-low damping factor be that important when there is appreciable resistance between one point in the voice coil and another point in the voice coil? The speaker is not a magic machine for converting volts into sound. It is a resistive load, mostly.

Oh gawwwd! We've been invaded by the audiophools :-(

...Jim Thompson

Right. Resistance anywhere in the circuit has the same effect.

John

Yep. Except it's not simply a "resistive load", it has a back EMF.

...Jim Thompson