warbs

I'm on the verge of wiring my car ready for amp etc.

If I could get 50 metres of hi-quality Coax Speaker cable for very cheap would it be worth using to make RCA leads and speaker cable rather than buying a traditional cabling kit for a car?

It's about the same thickness as the leads on a spark splug and very flexible (but it is purple ;( )

Cheers

Chris

chiark

One man's definition of high quality is another man's "oh God, we got this batch wrong".

Personally, unless you have experience of the cable in question, I'd be more tempted to pay for pre-made cables, or use cable that you know is good stuff.

Although you could bag yourself an absolute bargain - it's a bit of a gamble...

hades

IMHO Co-axial speaker cable is not a good thing. A feature of co-axial cable is that it has a significant capacitance. As electronics textbooks will tell you, impedance is proportional to capacitance divided by frequency. If you have a long run of high capacitance speaker cable, you tend to find that there is a significant impedance to ground at high frequencies. Net effect - half the treble "leaks" through the cable and doesn't make it to the speakers - result is "flat" sound with no sparkle.

With some hi-fi amps which have a flat frequency response to 100kHz or more, this is enough to cause them to go high frequency unstable and go "pop". Don't think you'll get this in a car, but I wouldn't use co-ax cable for speakers, full stop

Co-ax for RCA (line level) is fine due to the much high output impedance of the source: typically 10,000-100,000 ohms against generally <<1 Ohm speaker output (to drive a 4 Ohm speaker). Therefore, this high quality co-ax might be fine for use with RCA phonos, but can't comment without knowing more.

Sorry - no intention to blind people with science. Just that there are good scientific reasons to not use co-ax speaker cable.

warbs

From a pretty ignorant point of view I was most curious about the shielding effect of the coax in a car environment.

Lot's of people talk about interference and where to put cables for the least bother. regardless of quality if it's coax will it inherit some resistance to interference due to design - or does interference in wiring in cars come from somewhere else (earth?).

The same brand (Klotz - I think) is sold for seperates and video at £25 for a 1 metre lead - this is less than that per 50m - I'm confident it's not from a dodgy run (it's in our staff shop, end of line).

cheers

Chris

warbs

Found it :

LY225K at : http://www.klotz-ais.de/produkte/pdf/LY2K_eng.pdf

Be interested in anyones thoughts....

I expect I'll have some spare, and can get 100m in total

Cheers

Chris

chiark

Be interested to know what sort of price you're looking at. There's a few sites sellign this, and it is pretty cheap by the look of it...

Nick.

warbs

Chiark,

It's costing me 47p per metre.

You're welcome to what's left out of the first 50m plus whatever it costs to post.

It'll be a few weeks until I wire my car up - but I'm expecting to have about 25m left, depending on how I route it all.

Cheers

Chris

Si.t

I've made my own coaxial cable wit shark plugs from maplin - the good ones - you can save a bit doing this, and of course cut the cable to the desired lenght.

Given that capacitors are used to attenuate tweeters, I agree with the treble loss - well spotted there Mr Hades

hades

Thanks Si, glad that expensive education didn't go to waste I agree about the shark plugs from maplin - they are decent enough quality and very good value, assuming you're happy to make your own leads

Looking at it, the capacticance of that cable is about 600 pF/m. Spec I've found on a few other speaker cables is perhaps 50nf/km which is 50pf/m. Therefore, this has about 10 times as much capacitance. Net effect will probably be a slight softening of treble and loss of "sparkle", but probably nothing too horrendous. The cable has good low resistance - i.e suited to high power. Almost certainly won't sound as good as more exotic material cables (eg OFC, silver plated, PTFE insulated), but then again they'd be much more expensive - at 50p/m guess you can afford to try it.

Re: the interference. Speaker cables carry large amounts of power. Interference adds a very small amount of signal to cables. Therefore, generally in a speaker cable, the high power amp output tend to drown out the small power signal and you don't hear anything significant. With a line level (phono) signal, the signal is much smaller (lower power), so interference has much more effect. Hence, you do often need a co-ax cable for the hook up between your head unit and power amp, for example.

I'm going to have to stop with this applied physics stuff

Si.t

did you get a degree in waffle as well?

My dissertation was shorter than that!!!!