Slow speaker cables?

12-11-12: Csontos
Some of the best sounding amps have limited bandwidth. I don't understand how greater high frequency extension="faster". Is it not rise time that ultimately determines the perceived speed of the amp at the upper end of the scale? Not taking you to task Al.

That is a legitimate question, Peter.

First, bandwidth and risetime are intimately related. Oversimplifying somewhat, the greater the bandwidth the faster the risetime.

But what I was referring to was primarily greater high frequency extension within the 20 kHz audible spectrum. Under some circumstances speaker cable inductance can produce an audibly perceptible rolloff of frequencies that are within that range. Particularly, as I said, if the impedance of the speaker is low at those frequencies. Electrostatics, for instance, commonly descend to the area of 1 ohm at 20 kHz, as I'm sure you realize. The inductive reactance of a speaker cable (inductive reactance being the inductive form of impedance, which is measured in ohms and is proportional to frequency), can be a significant fraction of that value at upper treble frequencies, particularly if the cable length is long and/or the cable does not have low inductance per unit length. The voltage divider effect resulting from the interaction of those two impedances will, to at least a small degree, roll off the upper treble.

Rolloff of the upper treble will, of course, tend to be perceived as sluggish transient response, and probably dullness as well.

Bandwidth limitations beyond 20 kHz, either in the amplifier or resulting from the interaction of cable inductance and speaker impedance, may also have audible effects, due to phase shifts of audible frequencies that will increasingly occur as bandwidth is reduced. That is one reason, btw, that amplifier bandwidth needs to extend considerably beyond 20 kHz.

Another factor necessitating bandwidth margin in the amplifier is, I believe, minimization of feedback-induced TIM (transient intermodulation distortion), if the amplifier uses feedback. Transient response that is sloppy and distorted as a result of TIM might also contribute to a perception of sluggishness, but that gets into amplifier-related matters that are not germane to this discussion.

Best regards,
-- Al

"Wouldn't a slower cable slow all parts of signal down, not just one part?"

In a nutshell, probably not. Signal propagation of all sorts, including that associated with a wire conducting an electrical signals, is highly frequency dependent in theory. It's just a matter of how much and whether significant enough to matter or not in any particular case. I believe it is significant enough to matter for many with discerning ears in the case of speaker cables. Even more so in the case of analog ICs. At least, that is my assessment based on my personal listening experiences.

Al, how do you know so much about all of this!?! I see you posting responses to questions all the time here; you seem like a genius to me. Anyways, thanks to everyone else too that helped me get a better understanding of fast vs. slow cables. I had to read Kreallmans first post a few times, scratching my head asking myself "is he being sarcastic", then I read his second post then realized he was joking...lol.

12-11-12: B_limo
Al, how do you know so much about all of this!?! I see you posting responses to questions all the time here; you seem like a genius to me.

Thanks, B. I have an extensive background in electronic design, both analog and digital, although in defense electronics, not audio. And I've been an audiophile since around 1980. And I enjoy getting into the technical aspects of the hobby.

Best regards,
-- Al

B- He seems like a genius to most of us.