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Super Simple theory on speaker cables

Let's call this ESST for "Erik's super simple theory" of speaker cables and how they actually work.

As you may know, I've been involved in the DIY speaker building hobby for a while, and ages ago got to sit in on a class at Georgia Tech.

Since then I have noticed a weird effect. A slight change in impedance in the 100 Hz to 1kHz range Say, between 3.5 Ohms and 3 can cause a noticeable and unexpected change. In one case, I worked on a Focal which had a really wonky crossover. After analysis, it seemed it was deliberately trying to lower the impedance in the bottom of this range. Lots of resistors that did not need to be there.

So, here is what I think is going on:

Speakers and amplifiers are much more sensitive to impedance changes than we think they are. Yes, of course this should be covered in damping factor and amplifier output impedance, but what if it isn't? What if either the ear is more sensitive, or if there's something else in amps that makes them perform worse than their damping factor?

If this hypothesis is right, then speaker cables need add just a little inductance or capacitance to make a difference.

No quantum, wave theory or skin effect needs to be involved.
erik_squires
elizabeth
6,726 posts
 
The midrange resistor on my Magnepan 20.7 seems to adjust the tone of the mids rather than the loudness. Adding the 1.0 ohm resistor (furnished) warms the mids and aligns them better fit to the bass panel. So the fact this is happening to the Magnepans just tends to confirm the op here theory a bit. 
Thought the treble resistor does seem to be to reduce the loudness. as well as change the tone. Just to mention.
erik_squires OP
5,268 posts
 
@Kosst_amojan
I did a complete analysis of the speaker in XSim. Gathered acoustical and impedance plots. The only thing that circuit did was lower the impedance.

You can remove one cap and resistor section with nearly zero effect to the voltage transfer function. With a "normal" low pass filter, you can raise the impedance, with the identical transfer function, and eliminate the resistors.

I’m confident in my conclusion: The crossover was deliberately designed to have a low impedance point.

Best,
E
erik_squires OP
5,268 posts
 
Hi @elizabeth,
Yeah, I put that in a different category. Several high end manufacturers have some sort of level setting which DOES show up in simulations as altering the output. I think those circuits are legit, whether dials or resistor changes.

What I'm talking about are how simulations miss how changes to the impedance curve alters the sound, even when the simulation says it does not.

This is kind of like how we assume tube amps are more sensitive than SS amps to hard to drive speakers.

We think, oh, it's a SS drive, what can 1 ohm change in impedance to? Actually, a lot.

Best,
E

kosst_amojan
2,095 posts
 
@erik_squires 

I don't see what the problem is with that. That's very characteristic of Focal. That's how they get their unusually small woofers to create the bass performance that they do. 
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