Polk (Cobra) Speaker Cables

Peter Daniel · 1st February 2005, 05:01 PM

While browsing this site: http://www.high-endaudio.com/RC-SpkrCab.html I noticed interesting comment on Polk speaker cables. Yesterday, I met another local audiophile who had those cables and he indeed confirmed that they are one of the best.

Any idea about availability of those, as it seems like they are very rare now.

SY · 1st February 2005, 07:44 PM

If these were the ones from late '70s/early '80s, they were total amp-killers. You can get the same result by hanging a 0.1uF cap across some zip cord- or, even better, orange Home Despot wire

DSP_Geek · 1st February 2005, 09:15 PM

If you really want a low inductance solution with less capacitance than the Polk wire, try 4 parallel runs of RG-8. Connect all the shields together, all the cores together, and you have 0.018 uH/ft at 120 pF/foot. For an 8 foot cable that's 0.144 uH and 0.001 uF. Resistance is truly negligeable because each RG-8 is about 12 gauge, so the 4 combined are close to 6 gauge.

The only problem is you'll find the wire inside the cabinet presents an order of magnitude more series impedance than the lead-in...

Cheers,
Francois.

Peter Daniel · 2nd February 2005, 01:20 AM

Quote:

Originally posted by SY
If these were the ones from late '70s/early '80s, they were total amp-killers. You can get the same result by hanging a 0.1uF cap across some zip cord- or, even better, orange Home Despot wire

I was told that the secret to the sound of those was in special braiding. AFAIK, the HD wires don't use that technique.

DSP_Geek · 2nd February 2005, 04:17 AM

Quote:

Originally posted by Peter Daniel

I was told that the secret to the sound of those was in special braiding. AFAIK, the HD wires don't use that technique.

SY was being facetious. The braiding which reduces series inductance also bumps up the parallel capacitance quite a lot, hence the remark about sticking a 0.1 uF cap in there. I like multiple fat coax for speaker cables because you get the benefit of low inductance with reasonable amounts of parallel capacitance. Note the WireWorld speaker cables are also coax, although I think my arrangement is more cost-effective than theirs.

Of course, for *really* good results, I'd eschew binding posts, klugy things that they are, go with UHF connectors on amp and speaker, and run coax on the internal wiring as well.

Francois.

phoneisbusy · 2nd February 2005, 04:56 AM

You could drop by:
http://clubpolk.polkaudio.com/forum/

Some of the members have those cables. They even show up in the flea market on occasion. At the very least, they'd be happy to share their opinions of them.

regards

Dave

zBuff · 2nd February 2005, 05:10 AM

DSP_Geek,

so for your recommended amp -> speaker connections you would use one coaxial cable for both the positive and negative connections or perhaps a dual twisted crossconnected design (like Jon Risch's). By UHF connections do u mean BNC plugs, or maybe F or H type connectors?. I'm in the process of making a chassis for my recently completed 3875 gainclone and will be making my own speakers, thus I am free to implement any connections I see fit.

Peter,

Sorry for diverting your thread topic. Kudos to yourself and Brian for developing such great kit. I was surprised how quickly an amp could be made, turning it on the first time sure was nerve racking, but oh what sweet music it makes. I'm listening to right now as I type, surprising how much the sound is changing as it "burns in". The only problem is I think you might have started another addiction for me

On the topic of the cables, I was wondering if they are still in production today, I travel yearly to Japan and my inlaws live there. If the name of the Japanese manufacturer could be found, I could attempt to hunt it down.

planet10 · 2nd February 2005, 09:13 AM

Cobra cable was one of the very 1st exotic speaker cables. We sold them (for a while) in the late 70s. They were indeed amp killers -- one of the reasons we quit selling them.

I recently flogged off all 4 sets that i had.

They used 2 colors of enameled wire braided over a plastic core at approximatly 90 degrees with a sheath of clear plastic.

Besides the capacitance issue, there was a tendency for the enamel to scratch & short-circuit. They were also a pain to re-terminate.

dave

planet10 · 2nd February 2005, 09:14 AM

and a close-up

rdf · 2nd February 2005, 03:10 PM

Had a pair myself, the Bryston 2B never complained.

If I recall there was also an issue around internal shorting. The wire's ceramic coating could be damaged by stepping on it.

1st February 2005, 05:01 PM	#1
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Polk (Cobra) Speaker Cables While browsing this site: http://www.high-endaudio.com/RC-SpkrCab.html I noticed interesting comment on Polk speaker cables. Yesterday, I met another local audiophile who had those cables and he indeed confirmed that they are one of the best. Any idea about availability of those, as it seems like they are very rare now. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

1st February 2005, 07:44 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	If these were the ones from late '70s/early '80s, they were total amp-killers. You can get the same result by hanging a 0.1uF cap across some zip cord- or, even better, orange Home Despot wire __________________ If there's a sucker born every minute, where do the rest of them come from?

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1st February 2005, 09:15 PM	#3
DSP_Geek diyAudio Member Join Date: Aug 2003 Location: Santa Cruz, California	If you really want a low inductance solution with less capacitance than the Polk wire, try 4 parallel runs of RG-8. Connect all the shields together, all the cores together, and you have 0.018 uH/ft at 120 pF/foot. For an 8 foot cable that's 0.144 uH and 0.001 uF. Resistance is truly negligeable because each RG-8 is about 12 gauge, so the 4 combined are close to 6 gauge. The only problem is you'll find the wire inside the cabinet presents an order of magnitude more series impedance than the lead-in... Cheers, Francois.

2nd February 2005, 04:56 AM	#6
phoneisbusy diyAudio Member Join Date: Mar 2004 Location: Vancouver B.C.	You could drop by: http://clubpolk.polkaudio.com/forum/ Some of the members have those cables. They even show up in the flea market on occasion. At the very least, they'd be happy to share their opinions of them. regards Dave

2nd February 2005, 05:10 AM	#7
zBuff diyAudio Member Join Date: Nov 2004 Location: NZ	DSP_Geek, so for your recommended amp -> speaker connections you would use one coaxial cable for both the positive and negative connections or perhaps a dual twisted crossconnected design (like Jon Risch's). By UHF connections do u mean BNC plugs, or maybe F or H type connectors?. I'm in the process of making a chassis for my recently completed 3875 gainclone and will be making my own speakers, thus I am free to implement any connections I see fit. Peter, Sorry for diverting your thread topic. Kudos to yourself and Brian for developing such great kit. I was surprised how quickly an amp could be made, turning it on the first time sure was nerve racking, but oh what sweet music it makes. I'm listening to right now as I type, surprising how much the sound is changing as it "burns in". The only problem is I think you might have started another addiction for me On the topic of the cables, I was wondering if they are still in production today, I travel yearly to Japan and my inlaws live there. If the name of the Japanese manufacturer could be found, I could attempt to hunt it down.

2nd February 2005, 03:10 PM	#10
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Had a pair myself, the Bryston 2B never complained. If I recall there was also an issue around internal shorting. The wire's ceramic coating could be damaged by stepping on it.