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Math + Logic + Science = something completely mad...

So, I've done a metric fuckton of research, notwithstanding the clear bias the man who designed and built my Belles has against esoteric cabling.  And here's the conclusion to which I arrived. 

My monoblocks are sitting on top of the speakers.  The distance from the amp to the speaker is barely a foot, which is exactly how long a run of wire I intend to use.  Goal is to minimize the effect the wire has on the sound.  

According to the calculations I've seen and done, the skin effect depth on copper wire at 20Khz is 461 micrometers.  Meaning a 19-gauge copper wire (911 mics diameter) would reduce skin effect to zero.  As in no impact whatsoever on the signal. 
 
Of course, it's actually very difficult to find 19-gauge wire.  18-gauge (1024 mics) is much easier, and the skin effect is near zero, but not quite zero.  Seems to be an acceptable compromise. Could go down to 20-gauge and eliminate skin effect entirely.  If I could find insulated aluminum wire, 18-gauge would eliminate skin effect entirely, because skin effect depth on aluminum at 20khz is 580 mics.  

12 inches of 18-gauge wire produces 0.006 ohms of additional resistance.  20-gauge = 0.01 ohms.  

Frankly, I don't see the value in spending big bucks on esoteric, heavy-gauge wire for this application.  I'd rather make the bigger investment in the 2m runs from the preamp to the blocks, because that's where the wire's going to have a hell of a lot more of an effect on the sound.  

Stepping back to allow you all the opportunity to punch holes in my thought process here. 
jerkface
62 responses Add your response
jerkface OP
73 posts
 
Skin effect is rarely an issue. Inductance can be.

Only reason I bothered with the math on skin effect is because so many of these esoteric high-end cables do random weird stuff like adding dielectrics to "phase-correct" the signal.  

Of course, over 1-2 feet of wire, I doubt seriously that the signal could possibly get "out of phase" enough to be audible anyway.  

Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers.

So you're saying that the speaker vibrating the amp will cause microphonics in the tubes?  Or is there a concern about proximity to the magnets?  Certainly I could build shelves, that's an easy thing.  I'm just trying to make sure I understand the problem I'm trying to solve here in order to solve it correctly.  If you don't mind, I'd love for you to go over the science with me here. 
dletch2
455 posts
 
Microphonics in tubes is a very real thing. The mats will not eliminate that. I would be inclined to build shelves slightly above the speakers.


Your short 18 awg cables will work perfectly of course. The resistance is but a minuscule fraction of the speaker impedance. Following that short 18awg is a ton of wire in the cross-over, followed by a lot more small gauge wire in the voice coil. The variation in the resistance in the voice coil due to thermal effects is far more than the total resistance of that 18awg.


Virtually every negative reply you will get will be hand-waving with no quantification as you have done. Keep in mind the wire is 2 lengths, resistance will be closer to 0.016 ohm. That will be consistent with virtually no thermal modulation. It is likely a very small fraction of the output impedance of your amplifier too. At 20KHz, the impedance will be up to 0.022. You did miss one critical element though, inductance. That will be the dominating factor. That will increase the impedance to 0.08 - 0.1 ohm by 20KHz. You won’t hear it, but it will be there. Skin effect is rarely an issue. Inductance can be.

jerkface OP
73 posts
 
Can you provide a picture of your setup?

Sure. https://pbs.twimg.com/media/E0JH7A2XsAcv-Zj?format=jpg&name=small

Mats and interconnects are still en route, hence why I haven't powered them up yet. 
oldhvymec
5,101 posts
 
NO. Setting amps on speakers.
NO. 18 gage cable.
NO. skin effect

If you don’t have the room for the amps come up with a different plan.
A good 8 - 16 strand OCC/silver clad PTFE weave up to 3 meters long will work perfect. Red copper or copper/silver terminal ends. (B-16) is an option. OCC or OFC 8-24 strand weave PTFE is another.

No idea where you got your information.. We’re not rewiring a toaster or an ARC welder. The RIGHT kind of cable selection goes a long ways as far as "How does it Sounds".

You’ll squeak out some sound with #18 all right.. :-)

The cable I’m talking about sells for 250 - 3500.00 +. Depends on who’s name is on it..

They actually cost about 150.00 usd. Delivered.. and put together pretty well if you want someone else to do the work..

Second option is a ribbon design.. Same price very close in SQ to Norcast Vanilla. They make anything sound as good as it’s gonna get..
Ribbons and weaves are really really good cables for the money.

GREAT cables are very affordable, LOL so are BAD ones..

Time to feed the chickens..

Regards

onhwy61's avatar
onhwy61
5,217 posts
 
Sounds like you have a plan.  Go for it!

Can you provide a picture of your setup?
jerkface OP
73 posts
 
Wouldn’t the wire at least get warm if you played it at a continual hundred watts?
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Two part response here:

1) These are 25-watt monoblocks going into horn-loaded loudspeakers.  So they will never see 100 watts.  Not even at peaks. 

2) Heat generation is directly proportional to resistance and current.  More resistance + more current = more heat.  The amount of current flowing through a speaker wire is laughably small, even with big SS amps.  And further, if a small-gauge speaker wire was at risk of catching fire at 100 watts, you'd have to think that the much tinier wires on the other end of the speaker's crossover would instantly burst into flames, because they're typically 24AWG or smaller.  
raysmtb1's avatar
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raysmtb1
800 posts
 
I was half joking, thinking out loud. I couldn’t imagine putting my MacIntosh mono blocks on top of my speakers with a little tiny 18 gauge wire. Seriously I don’t know,Wouldn’t the wire at least get warm if you played it at a continual hundred watts?
jerkface OP
73 posts
 
running a short piece like that is going to act more like a light bulb than a speaker wire.
I don't get how you arrive at this conclusion.  Again, 12 inches of 18 gauge wire adds a net of 0.006 ohms of additional resistance to the signal.  

Also, light bulb filament is a mere 46 micrometers - it doesn't even rate on the AWG scale, the smallest gauge being 38AWG (100 micrometers).  

Care to explain the science behind your declaration? 
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raysmtb1's avatar
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raysmtb1
800 posts
 
18awg wire is very small, 20awg even smaller.. running a short piece like that is going to act more like a light bulb than a speaker wire.
jerkface OP
73 posts
 
An amp on top of speakers is not a good place, especially a tube amp, they are better off on the floor (vibration control). The skin affect at audio frequency's is not worth worrying about especially with just a two foot run but a quality solid conductor cable will certainly do the job.

The floor is not an option (space issues), and they are sitting on heavy dampening mats.  
russ69's avatar
russ69
3,501 posts
 
An amp on top of speakers is not a good place, especially a tube amp, they are better off on the floor (vibration control). The skin affect at audio frequency's is not worth worrying about especially with just a two foot run but a quality solid conductor cable will certainly do the job. 
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