Audiosphere with Coral flat 5, but what cable?

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Fullrange Drew

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Audiosphere with Coral flat 5, but what cable?
« on: 13 Jun 2015, 08:41 am »
Some Australian Circle folks may know of the now defunct "Audiospheres".  Concrete spherical enclosures, which in the case of my new babies (secondhand) contain a single Coral Flat 5 driver.  Food source is a PP EL84 (triode mode, zero NFB, fixed bias output stage, no cathode bypass caps).

What to do for speaker cable.  Chasing fast but sweet if that's do-able...  Seems mad to have such a purist and unsmeared pair of speakers and then put a "Wooly" cable on them.  Precision, clarity and razor sharp timing would be great, but I really don't want to use something that results in "harsh" in the upper registers.  Provoked into nastiness, the Corals can be unforgiving. 

Current speaker cable is about 4m of ultrafine stranded stuff from Bunnings with a silicone insulation layer.  At present I'm leaning in the direction of DNM Precision or Kimber 4TC.  Afraid the budget is pretty limited.  Fortunately most of this brethren of loudspeakers seem to favour simpler cables rather than garden hoses...

FullRangeMan

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #1 on: 13 Jun 2015, 12:23 pm »
Due personal taste and interactions with the amp, it is difficult to hit an indication of speaker cable.
A suggestion would be you test in your living room cables that are more accessible in your area/city.

Scottmoose

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #2 on: 13 Jun 2015, 03:41 pm »
My presence here is likely as welcome as a dose of ebola, but for what it's worth, as noted, amplifier / speaker / room interactions play a role here. If you do not wish the wire to provide audible contributions to the system (since its electrical characteristics can affect the behaviour of the components it connects together), then you need to ensure

a/ voltage drop is insignificant ( < 0.1 for preference)
b/ Capacitance is not significantly raised
c/ Inductance is not significantly raised

Chasing low inductance generally means capacitance goes through the roof, unless you slap a Zobel network on the wire. Which seems excessive, for wire. Likewise, chasing low capacitance generally means inductance rockets. Neither of these are a good idea if you don't want the wire to cause shifts in system behaviour. Low inductance is a nice idea in theory, but the high capacitance can result in instability for some amplifiers. A very low capacitance wire isn't likely to cause instability problems, but the raised inductance can result in an HF roll-off -how significant depending on the degree of inductance for a given situation.

Fast but sweet being the subjective matters they are, from my POV I'd class them as a technical oxymoron, since 'fast' typically means wide bandwidth, while sweet implies a more-or-less rolled off HF. But that's just my interpretation and everybody else will probably have a different one. Still, running with my imperfect interpretation, you could DIY it for peanuts. Try some solid core mains wire (romex or whatever); space the conductors about an inch apart & see what gives. You can also do this with higher resistance wire -a couple of 24ga strands extracted from a run of Cat5 network cable, untwisted & spaced apart per above. Gives a little extra inductance; solid core has less surface area to corrode (useful in high humidity environments). Magnet wire can be used in the same way & is very inexpensive. If you like the results & believe more exotic materials will bring benefits, be they in terms of the conductor or the dielectric, there's plenty out there you can use, be it plated wire, solid silver, solid gold even, Teflon, PTE, cotton, over-sized xyz for a semi-'air' dielectric... name your poison. 

FullRangeMan

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #3 on: 13 Jun 2015, 03:55 pm »
Scott a member with your big knowledge is always welcome.
Thanks for mention the DIY, at the Jeff shop there is some nice inexpensive copper/teflon:
http://www.soniccraft.com/product_info.php/neotech-solid-upocc-copper-in-teflon-14-awg-red-p-1599
And even silver/Teflon:
http://www.soniccraft.com/product_info.php/neotech-solid-upocc-silver-in-teflon-18-awg-blue-p-1598

JohnR

Re: Audiosphere with Coral flat 5, but what cable?
« Reply #4 on: 14 Jun 2015, 01:25 am »
Some Australian Circle folks may know of the now defunct "Audiospheres".  Concrete spherical enclosures,

From the 70s? Could you post a pic? I think a friend may have had a pair (or rather, his father did).

Fullrange Drew

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #5 on: 14 Jun 2015, 05:14 am »
Once I get home to sunny Canberra I'll try to get some pics up.  I'm presently away in Brisbane for work.

In my original request for something "fast but sweet" I guess I didn't want a cable characterised as "bright" as the speakers themselves are already very dry and revealing (there's certainly no cabinet thrum to add any warmth).  While I'm using a class A tube amp with no feedback, it's a very simple circuit running the EL84's and 6CG7's in their most linear part of the curve.  No 2nd harmonic "warmth" to be added there either.

I guess I want to keep all that is revealing of timing and details, all the PRaT, tightness and precision as it were, but not add anything to make the sound brighter.

Maybe Scott is right and my goals are mutually exclusive...

Scottmoose

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #6 on: 14 Jun 2015, 03:42 pm »
Not necessarily, since as noted, subjective terms being what they are, what you define by them is not necessarily what I (or anybody else) does. This is also a matter of degree; you have to go to extremes for major shifts in behaviour. From what you describe, & without knowing what the output impedance of the amplifier is) I'd try for a higher inductance wire & see if that gives you what you want. It's not an unknown combination for widebanders, especially those with an upward-tilted on-axis response balance. If you want to DIY it, see my last for some options. Or there are a few on the market that partly qualify, even though they aren't necessarily marketed as such. Look for a shotgun / figure 8 / side-by-side configured wire with the conductors spaced apart from each other. If you want to try it in the extreme, use physically separate legs for the hot and return legs, spaced well apart. The downside to doing that is potential inconsistency, so it's a good idea to ensure both channels are done identically. Thinking off the top of my head, in the commercial market the cheaper speaker wire by Gale, Cambridge Audio and Acoustic Research used to have this sort of configuration (I can't recall if they still do). Slightly further up the price range models from Van den Hul & Tellurium Q come to mind. If you value a brand name commercial wire, then Van den Hul should be a fairly safe bet since this is the physical configuration employed in most of their twin-lead products.

Fullrange Drew

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #7 on: 16 Jun 2015, 03:10 am »
While I don't want things to be harsh, I also don't really want the high frequencies rolled off.  The Corals get to about 18k from memory, but are missing that last little bit at the extreme top end.
Amp output impedance is about 2 ohms I believe (from theoretical calculations, not from measurement).  Voice coil inductance is probably going to be far more significant that cable inductance.
The run is about 13 feet per channel.
I'll see if I can source some solid core around 20ga and have a play.

Fullrange Drew

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #8 on: 1 Sep 2015, 08:43 am »
After some deliberation I ended up getting some Audio Principe silver plated solid core from Peter Graves here in Australia.  Pleased to report success, with all desirable characteristics seemingly achieved (speed, detail, smoothness) and none of the harsh aspects (harshness, fatigue, loss of bass).

Stupidly good price too.  Very happy.  Highly recommended.

FullRangeMan

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Fullrange Drew

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #10 on: 2 Sep 2015, 05:59 am »
That's the stuff.

Big WAF too, not some massive hosepipe of a cable.  Tidy, slim and lets the music through.

G Georgopoulos

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #11 on: 2 Sep 2015, 06:20 am »
From wikipedia

Quote
Wire material
Use of copper is more or less universal for speaker wire; it has low resistance and less cost compared to other suitable materials. Copper and aluminum both oxidize, but oxides of copper are conductive, while those of aluminum are insulating. Also offered is Oxygen-free Copper (OFC), sold in several grades. The various grades are marketed as having better conductivity and durability, but they have no significant benefit in audio applications.[4] Commonly available C11000 Electrolytic-Tough-Pitch (ETP) copper wire is identical to higher-cost C10200 Oxygen-Free (OF) copper wire in speaker cable applications. Much more expensive C10100, a highly refined copper with silver impurities removed and oxygen reduced to 0.0005%, has only a one percent increase in conductivity rating, insignificant in audio applications.[4]

Silver has a slightly lower resistivity than copper, which allows a thinner wire to have the same resistance. Silver is expensive, so a copper wire with the same resistance costs considerably less. Silver tarnishes to form a thin surface layer of silver sulfide.

Gold has a higher resistivity than either copper or silver, but pure gold does not oxidize, so it can be used for plating wire-end terminations.


and i thought OFC copper was better than generic copper...  :duh:

Fullrange Drew

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Re: Audiosphere with Coral flat 5, but what cable?
« Reply #12 on: 3 Sep 2015, 03:06 am »
For even more laughs, look up "tube sound" on wikipedia...