Another proposal
"mick" wrote in message
.uk...
On Mon, 14 Jan 2008 10:02:58 +1100, Trevor Wilson wrote:
snip
**Perhaps you missed what I wrote. Read it again. I was VERY specific
with my words. Unlike our friend Iain, I do not make blanket
pronouncements which can easily be proven incorrect.
Skin effect is the tendency of the signal current to
flow at, or close to, the surface of the conductor. It isn't measurable
using any normal systems and almost certainly won't be audible.
**Read what I wrote.
I did. Again. I completely agree that skin effect is real in any
conductor carrying AC or DC with an AC component. IMHO, though, it's
effect is not just minor but not relevant at all. :-)
**No argument from me. Iain claims that skin effect is a myth. It isn't.
snip
**For the record: I cut my teeth on HF transmission (and satellite)
transmission equipment. I am familiar with the problems and solutions.
My words stand. Iain is wrong. Skin effect is not a myth.
True, it's no myth at all.
**Pre-zactly. Iain consistently claims that it is a myth.
More importantly, perhaps, is the fact that many exotic speaker
cables exhibit low INDUCTANCE figures. It is this characteristic which
may be very important for many users of ESLs, as even quite short
cable runs (10 Metres or even less in some cases) can benefit from low
inductance cables. IMO, skin effect is not an important parameter in
the vast majority of real world systems. Inductance, OTOH, may well be
very important.
Sorry, but I'm an unbeliever in speaker cable inductance - over any
sane length anyway. For me, any speaker cable over about 3m (i.e. loop
length 6m) is too long and I just can't see that anything contributed
by the cable other than resistance (which is usually swamped by the
speaker impedance & amp output impedance anyway) is going to make the
slightest difference to the sound.
**I suggest you brush up on your electrical theory. My first experience
with the effects of speaker cables was in 1978. My client had quite long
cable runs (ca. 12-15 Metres) and speakers which exhibited rather
difficult HF impedance. Substituting low inductance cable made a
substantial improvement to the system. After some considerable effort, I
placed the amplifiers under the floor, directly beneath each speaker.
The improvement was even more pronounced.
I bet the low inductance cable had a larger CSA, so the loop resistance
was lower.
**Nope. Roughly the same. In fact, the low inductance cable was slightly
higher resistance. Not much though.
Shortening the cables helped again.
**Indeed. That was a dramatic change.
Seriously, compared to the
inductance of the voice coil the cable inductance is tiny. The difference
*at audio frequencies* is going to be less than a midges d**k! ;-) IMHO
12-15m is insane for speaker cables anyway... :-)
**The voice coil had a measured impedance peak of 120kHz (measured with
MLSSA). I never actually measured the inductance, but I can assure you that
it was VERY low. Much lower than a 10 Metre length of speaker cable. And
there were three HF drivers in parallel. As for placement, unfortunately,
clients often want what is not convenient for me. I recall one installation,
where I informed the client that, for optimum sound quality, the Steinway
had to go. The look of horror on he and his wife's face was priceless.
Naturally, the Steinway remained exactly where it was.
In another installation, the client demanded that the cables be invisible.
This required that the cables be very compact and routed behind skirting
boards in a concrete home unit. It was a tough and exacting job. The unit
would be presently valued at in excess of AUS$5 million (nice views of the
Harbour Bridge AND the Opera House). Cosmetics are everything. The cables
were, therefore, at least double the length that they would otherwise be. I
custom manufactured cables, using PTFE insulated wires. I did so, for two
reasons:
1) I wanted to reduce inductance.
2) PTFE insulation allowed me to construct a cable which was much more
compact than a commercial product, yet still retain reasonable resistivity
figures for his 4 Ohm speaker system. The runs ended up at around 15-17
Metres.
Trevor Wilson
|