Speaker wiring really is a hot topic on all audio related forums. Next time I'll use the term "speaker wire" instead of "lamp cord". :-)
For a small and inefficient Kef satellite speaker (3" with a tiny coaxial tweeter and internal crossover circuit), unable to reproduce frequencies lower that 120Hz, driven by a dirt cheap 10W class-T amp, for listening at a maximum distance of 2.5 meters, I doubt that using short lamp cords will be my worst problem; sleeping well, for example, is a better investment to improve my listening experience than getting better cables or amplified speakers. For lower frequencies I use small subs with integrated amps; I have no idea if Kef used some negative impedance trick in their cheapest sub. Wed, 27 Jul 2011 07:43:37 +0000, Fons Adriaensen <f...@linuxaudio.org> a écrit : > On Wed, Jul 27, 2011 at 01:41:51AM +0300, Sampo Syreeni wrote: > > On 2011-07-26, Fons Adriaensen wrote: > > > >> I certainly don't want you to waste your money on fancy speaker > >> cables. > > > > Never thought otherwise. That's obviously never been what we do > > here. ;) > > > >> But resistance does matter, so a good cross section such as 2.5 > >> mm^2 puts you on the safe side. > > > > What I was trying to ask is, what's the real problem with > > resistance, especially with regard to a passive speaker and a > > modern, A/B class solid state end stage? I mean, I don't really see > > cable resistance shifting their operating point much, even with > > feedback, within the audible range. > > > > What is it that I'm missing? > > When the voice coil of speaker moves in the magnetic field it > is surrounded by it generates a voltage proportional to its > velocity. Ideally that voltage should be equal to the one > produced by the amplifier: in that case the amplifier has > complete control over the movement. > > You can easily test this: disconnect the speaker and gently > push the cone of the woofer. You will see it moves quite > easily. Now connect the speaker and switch on the amplifier, > OR just short-circuit the speaker terminals. In both cases > the speaker sees a very low impedance, and it will resist > movement. > > In practice there is a problem: any resistance in series > with the 'ideal' voice coil means that those two voltages > are not equal and the amplifier is not fully in control. > > The resistance that appears in series is the the sum of the > DC resistance of the voice coil itself, cable resistance and > the output impedance of the amplifier. This sum should be as > small as possible, and cable resistance can be a significant > part of it. > > One advantage of integrated amps/speakers is that the amplifier > can be designed to compensate for this resistance by giving > it a negative impedance. This has to be controlled very > carefully - overdoing it makes the whole thing unstable and > ready to auto-destruct. Which is why it can't be done with > separate amps and speakers. > > Ciao, > _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
