Testing audiophile claims and myths - Page 107

Quote:

Originally Posted by Steve Eddy 

 

You obviously have no appreciation at all for the sheer amount of work it takes to make a mountain out of a molehill.

I have great respect for the fine art of technical prevarication!

Quote:

Originally Posted by mikeaj 

 

Are we allowed to use more than one molehill, or is that cheating?

A mountain out of a molehill. Singular.

se

Quote:

Originally Posted by mikeaj 

 

Are we allowed to use more than one molehill, or is that cheating?

Only if the sum of the molehills doesn't add up to a hill of beans!

Quote:

Originally Posted by bigshot 

 

I have great respect for the fine art of technical prevarication!

No words over three syllables allowed.

se

There are also plenty of relatively cheap 16 gauge zip cords out there that should work just fine, much cheaper than whatever the boutiques are selling.  Just because 24 gauge cheapo wire is a problem for longer runs to speakers doesn't mean that something cheap isn't okay

But the authors explanation on damping ... is that correct or it mainly fluff? If so, why? I'm just trying to better understand this.

It's exaggerated Yahzi. If you were running wires to a house four doors down the block, it would be an issue. But when you're running them across the living room, it isn't.

Mike AJ posted a great link that explains every issue involved, not just damping, and puts it all in context so you know what you really need. This guy knows his stuff.

http://www.roger-russell.com/wire/wire.htm

Yeah, there's something legitimate going on—unlike some power cord metallurgy BS or whatever else people espouse these days—but it's just not usually a big deal.

If humans can't hear it, people shouldn't sweat it.

He said in the article "The resistance of the cable must be added to the output impedance of the amplifier".

But is it true? And if so why? Some "experts" say that the total resistance in the cable should not exceed 5% of the nominal resistance of the speaker. Why is that, or is it a load of bull?

Quote:

Originally Posted by Yahzi 

He said in the article "The resistance of the cable must be added to the output impedance of the amplifier".

But is it true? And if so why? Some "experts" say that the total resistance in the cable should not exceed 5% of the nominal resistance of the speaker. Why is that, or is it a load of bull?

How long of a run are you talking? Because for an average-ish run (say 10 or so feet) of decent gauge (16 or bigger) you shouldn't be anywhere near 5%, maybe more like .01% of an 8ohm speaker.

Quote:

Originally Posted by Yahzi 

He said in the article "The resistance of the cable must be added to the output impedance of the amplifier".

But is it true? And if so why? Some "experts" say that the total resistance in the cable should not exceed 5% of the nominal resistance of the speaker. Why is that, or is it a load of bull?

The impedance of interest is that of everything in the amplifier -> speaker pathway that's not the speaker.  You add everything else up, including the cable impedance and amplifier output impedance, because these elements are in series, and impedances in series have an overall effect like the sum of those impedances (with lumped-effect model, should be accurate enough at audio frequencies, these distances).

Because the speaker impedance varies with frequency, you want the other impedances to be low so you don't have unintended frequency response shifts and a little bit of excess distortion.  Also, because any extraneous impedance is in series with the speakers, you'll get a little less volume if the impedance is high.  The higher the cable (or amp output) impedance, the greater the effect on the system response.**  5% is a safe limit such that the response of pretty much any speaker will only be marginally affected, definitely not worth worrying about.  Some others may say 10% or something else.  For some speakers, you could get away with more, or they may sound different but not necessarily worse.

**in practice, a "greater effect" relative to something really small may still be trivial.  Let's not get overexcited here.  It depends on how much we're talking about, the speakers.

Quote:

Originally Posted by mikeaj 

Quote:

Originally Posted by Yahzi 

He said in the article "The resistance of the cable must be added to the output impedance of the amplifier".

But is it true? And if so why? Some "experts" say that the total resistance in the cable should not exceed 5% of the nominal resistance of the speaker. Why is that, or is it a load of bull?

 

The impedance of interest is that of everything in the amplifier -> speaker pathway that's not the speaker.  You add everything else up, including the cable impedance and amplifier output impedance, because these elements are in series, and impedances in series have an overall effect like the sum of those impedances (with lumped-effect model, should be accurate enough at audio frequencies, these distances).

 

Because the speaker impedance varies with frequency, you want the other impedances to be low so you don't have unintended frequency response shifts and a little bit of excess distortion.  Also, because any extraneous impedance is in series with the speakers, you'll get a little less volume if the impedance is high.  The higher the cable (or amp output) impedance, the greater the effect on the system response.**  5% is a safe limit such that the response of pretty much any speaker will only be marginally affected, definitely not worth worrying about.  Some others may say 10% or something else.  For some speakers, you could get away with more, or they may sound different but not necessarily worse.

 

**in practice, a "greater effect" relative to something really small may still be trivial.  Let's not get overexcited here.  It depends on how much we're talking about, the speakers.

Excellent explanation. My point was simply that unless you're using some really subpar or high gauge wire, or a long run, the wire resistance is probably more or less trivial. There was a great article I read about impedance, and how you are basically exponentially diminishing wattage with impedance. It made me think about it differently, more or less in the context that with a high impedance, your amp is basically driving a massive load, yet only 8z of that is the speaker itself, acting as a voltage divider, which is rather wasteful. A few pages back, someone talked about the relative merits (or rather, lack there of) of dampening factors. His points were excellent, so don't take my posting this article as being in confrontation to that. Rather, this wiki happens to have an excellent explanation of how to think of output impedance: http://en.wikipedia.org/wiki/Damping_factor

There is also a good wiki on output impedance, but I found it less informative than this one.

I have a friend who does PA systems for live shows, anything from a small club to an amphitheater. He was doing an outdoor show 50 miles out of town and his assistant forgot to put one of the speaker cables on the truck. He had cabling for one side of the stage but not the other. It was too late to drive back and get it, so he sent his assistant to home depot to buy a spindle of lamp cord. He ran lamp cord with duct tape over it for the full run, expecting there to be problems. When he went to do the sound check and EQ, he couldn't notice any difference at all between the two channels. The show went off perfectly.

This part  :

"By contrast, a 10 foot run of one quality high end 10AWG gauge cable can have a total resistance of just .02 Ohm. Adding this to the amplifier's output impedance of .01 Ohm gives a total of only .03 Ohms, which, divided into the 8 Ohm standard speaker impedance gives a true damping factor of 267 -- better than 17 times the speaker control available from the lesser cable. That's one of the key reasons why high end speaker cables sound better"

Everything I've read about damping factor tells me that going from a DF of 20 to 200 is very, very small. So the author is confusing the matter?

Quote:

Originally Posted by bigshot 

I have a friend who does PA systems for live shows, anything from a small club to an amphitheater. He was doing an outdoor show 50 miles out of town and his assistant forgot to put one of the speaker cables on the truck. He had cabling for one side of the stage but not the other. It was too late to drive back and get it, so he sent his assistant to home depot to buy a spindle of lamp cord. He ran lamp cord with duct tape over it for the full run, expecting there to be problems. When he went to do the sound check and EQ, he couldn't notice any difference at all between the two channels. The show went off perfectly.

I think that the 55c per foot "sprinkler" wire at Lowes is excellent. The strands are fine...ish so it's pretty flexible. You can get 12 gauge easy, and it's rated for outdoor use (low voltage) so the insulator is pretty robust and durable. I'm sure I could get the same performance out of cheaper cable, but I'm also sure I could get the same performance out of better cable, so that's about how far I'm willing to go. Oh, it's also OFC.