Hello,
In response to Dave's comment...
Quote
We know that with rising frequency, the electrons will reach for the surface.
Hmmm, I have never heard/seen it expressed in this fashion previously, but I suppose this is reasonable. I have always seen and convey the inverse statement - that lower frequencies and higher power require a larger gauge cable due to increased saturation. Hence, the abundance of electrons need a bigger wire.
...Jeff covers the practicality here...
4) Thin foil does not have the skin effect seen in solid conductors larger than 23AWG in the audio band.
The physics revolve around "eddy currents" that essentially create a loss, thus a reduction in efficiency. It's analogous to the turbulent back currents on the edges of a paddle as you force it broad-side through water. The faster the change in current (higher the frequency), the more loss you have. This is largely why attenuation is greater as frequency gets higher (check any coax cable spec). The eddy currents push the electrons that actually "move" to the outside of the conductor (hence, the name, "skin effect"). This increases the impedance of the cable by effectively reducing the amount of electrons that can actually move - which then correlates to the equivalent of having a smaller wire (higher AWG), thus the higher impedance and attenuation.
As Jeff aptly points out, the math shows that it effectively should not affect typical applications for audio enthusiasts, as we commonly use larger sizes than 23 AWG.
But, as a caveat to that, I do want to state the following:
In the "mathematics" of measuring and calculating performance...
Say we take an amplifier with an incredibly complex feedback scheme, producing just 0.005% THD+N rating... It's well established that it sounds worse* (less realistic) than a simple Single-Ended design with 0.3% THD+N.
* by the overwhelming majority of "high end" reviewers and "ears that I trust"God has given us INCREDIBLE instruments (our ears) that are capable of determining that 0.3% distortion sounds notably more "natural/realistic" than something that measures 1/60th of that.
For the record, I am not implying that THD is the be-all, end-all measurement to determine performance of a circuit (in fact, I believe my point above is quite clearly the opposite).
So, what I'm trying to get at... The fact that the "math" says that greater than 23 AWG speaker wire within the audio band should provide minimal to none skin effect, doesn't necessarily convince me that there isn't an audible effect. I'll leave it at that, but this is elaborated (indirectly) below.
As far as noted differences in inductors, I have the following comments.
1) I have done limited comparison of Foil wound vs. the "conventional" solid core cylindrical conductors. The comparisons I made were with Goertz foil and Solen Perfect-lay coils of matching wire AWG. The results were mixed. For lower frequencies, higher power applications, I prefer the Solen. For cone mids, depending on the driver, I usually prefer the conventional. For dome mids, I typically gave a
slight edge of preference to the foil. It seems obvious, but this appears to be a frequency (and perhaps current load, in my opinion) dependency.
**2) At face value, efficiency would seem to be less for foil, as they typically use a tape insulation, which is notably thicker material than the polyimide extrusion over conventional coil wire. Granted, the lay and wraps are drastically different. In any case, DCR values seem to prove otherwise (that foil is in fact more efficient).
3) I do not prefer iron core inductors above "subwoofer" frequencies... I hear muddying of the mid-range already quite evident, not to mention tweeter ranges. This is usually done as a cost saving measure, in my experience. I do believe that a large size AWG air core is notably superior in SQ, particularly for midbass precision.
4) I typically use "perfect lay" Solen coils, in most applications. With the other air cores from Jantzen and Madisound and the like, I've found only minor differences in sound when comparing directly (matching inductance values, and matching AWG of the core wire). The differences I hear are very minor. One isn't necessarily better, just "different."
5) Comparisons of the same value with varying AWG wire, I find, make significant impact to sound. IMO, North Creek Music is where it's at for coils. Their large AWG (physical, not numerical) coils are my personal favorite.
5A) Budget affects us all. If I had my choice, I'd use 10 or 8 AWG coils on all woofer circuits. In reality, I generally don't use less than (again, size, not numerical) 14 AWG on any series network component.
5B) The larger the inductance, the more I prefer a larger size AWG wire. Unfortunately, this gets exponentially more expensive.
6) As for the comments in #1) above, I personally feel that the capacitors used in the mid and tweeter circuits have roughly 50-100 times the impact on performance. Yes, seriously. That may discount my comments altogether with a lot of folks... but I'm pretty sure at least Dave would agree with me here (not verified, a presumption).
** This is intended to be neither pro nor con - merely an observation.Given the fact that I do indeed believe that larger size AWG coils sound better than smaller... I don't in any way claim that this proves that the cause is skin effect. But, I believe it at least brings light to the fact that it's possible that our ears are in fact capable of detecting skin effect anomalies. And that about wraps up my thoughts on the matter.
Also of note, in rereading/proofing of this post, I apparently really like to use "quotations."
Best regards,
