need 100 ft subwoofer cable - would normal RCA cable do? - Page 2

That part you made up.

Regards,
Wayne A. Pflughaupt

Well, actually, there seems to be a fair amount of RG-59 that has copper-plated steel conductor from what I see on the Belden site. So, the point is that just selecting RG-59 seems not to guarantee solid copper conductor.

Anyway, does it REALLY matter whether it's copper-plated steel or solid copper? Sure, given the choice, solid copper offers about lower resistance even though both values are fairly small such as ~1 ohm vs. ~2.5 ohm over 100ft, but again, does it REALLY matter?

What would support there being a significant (read clearly noticeable) difference in the resultant sound - especially considering a subwoofer setup?

Wasn't aware of that, thanks for the info.


For a subwoofer, probably not. It might make more of a difference with video signals, though - I'll leave it to the videophiles to discuss.

Regards,
Wayne A. Pflughaupt

I've noticed the same thing when shopping for bulk cable. There's some solid copper RG-6 and there's some copper clad steel RG-59. It's a minority in either case, but they're definitely in the product mix. Except for the fact that this might confuse one of my employees someday, I'm glad that they're available.


This is a stretch, but I'm hoping that this thread comes up with a scientific answer to this one. It's way outside my area of expertise, but I'll throw out an idea in case somebody wants to confirm it or prove it wrong: what if using one material vs. another changes the amplification levels at different parts of the frequency range? Since copper clad steel was selected for it's ability to carry higher frequency signals (broadband internet, digital cable, etc) (and again here, I'm going on hearsay), perhaps it carries lower resistance in this range. Copper, however, is what most unbalanced, line level audio signals were engineered for. Thus, the person mixing down your music would have tuned his EQ for the characteristics of the copper, which (again, I'm reaching here) supposedly hit high attenuation in high frequency ranges.

So, if my hypothesis holds true, then using steel to transmit line level audio would be similar to inserting an equalizer and increasing the gain on high frequencies and decreasing the gain on low frequencies.

They put copper around the steel in "copper clad steel" for a reason, though. Most people expect that cable coming out of the wall to still perform on the lower numbered cable channels, which are in the baseband range. One could suppose that it would also help the signal for line level audio.

In the case that the OP is asking about, none of this matters. It's all low frequency at a low current. Probably won't be affected by any of what I'm suggesting here.

Also, keep in mind that this is hypothesis. I'm only a custom installer who's trying to know "the right answer" instead of just going on hearsay. Hopefully, this thread will conclude with other people chipping in a scientific answer.

Or, as I'm often learning, there is another thread somewhere on AVS Forum that already answers the question. Maybe someone else knows where it is.

Looking forward to your replies, if anyone's game for getting to the bottom of this. Thanks in advance.

Kind regards,
Justis

I guess in this statement you are saying that RG6 is suitable? Maybe you need to read up on coax cable. That way so much stuff won't "float" around here.

Your hypothesis isn't correct.
Different metals and alloys have different reisistances. Restivity is a property of the material.
Copper is used because it is a good conductor, and reletively cheap (compared to silver).
Aluminium is also used, for it's weight and price properties.
The only difference in these conductors , is resistance.
Resistance doesn't affect frequency response.


CCS makes use of the skin effect.
Baseband basically means unmodulated, it doesn't apply here.


Unbalanced, line level audio is baseband, and does not make use of the skin effect .

The loss, due to series resistance of a cable, in a high impedance audio circuit, will be 3dB, when the cables resistance equals the input termination resistor on the audio device (which is typically between 10K and 50K Ohms).

Assuming a cable with a resistance of 2.5 Ohms/100',and a 10K input, you would need 400, 000 feet of cable, before noticing a slight loss in amplitude.

No doubt there is mis-infirmation floating around here but not from me. I was responding to a specific post that insisted Quad shielded RG6 should be preferred to RG59 for a subwoofer cable. When we compare QS to the average RG59 cable we find the extra shields present are mostly foils placed around the cable in addition to the standard copper braid found on almost every type of coax. These additional foil shields have everything to do with rejection of capacitively-coupled higher frequencies well beyond the audio range that would normally penetrate the gaps in the copper braid. That makes them as useless as tits on a nun on a subwoofer cable. RFI ingress on a subwoofer cable is generally not a consideration. The first thing an incoming signal sees on a subwoofer is a lowpass filter (the crossover) that would efficiently reject any RFI on the signal line. Additionally, the components in a subwoofer are not responsive to frequencies over the audio range anyway. While there have been a few instances of people with audible RFI coming through their sub it can always be attributed to a direct ingress into the unshielded sub amplifier itself from a radio station located next door. QS would not have helped. The low-frequency hum experienced by many is the result of a ground loop. Again, increased shielding would be totally ineffective in alleviating that problem.
Even the copper braid shield on RG59 isn't very useful for this application. The interference frequencies we might be interested in shielding against are around 60 Hz and below. The primary source of this interference is obviously household current lines. Unfortunately these inductively-coupled frequencies are nearly impossible to stop with a shield made of copper or aluminum. Only thick steel conduit can significantly shield against those frequencies. Fortunately the field strength present around household current wires isn't very strong and don't travel very far. Hence my statement that even RG59 is overkill. An audio patch cord would work just as well.

Exactly right. There is both copper clad and solid copper versions of both RG59 and RG 6. And would it matter on a subwoofer cable? Not even a little bit. It's 60Hz and below! People must remember that the requirements on a subwoofer are less than on any other cable in your system except the power cord (Let's not get started on those).