RC network(zobel) Radio Frequency speaker filter question?(rather long)

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I did a pretty thorough search of both this asylumâ€™s archives and those of the cable asylum on this subject as well as doing some Google searches. I live within a couple of miles of a rather large and powerful NPR transmitter tower. I became curious about RF pollution after switching some Naim speaker wire (I also have an old Nate for a second system) out of my system that was in there as a temporary measure back to my usual speaker cable. The first thing I noticed after installing the better cable was that the noise floor was noticeably lowered. I assume that the Naim wire is just a more efficient antenna than the German Audioplan stuff I normally use. This prompted me to start doing some reading. I ran across a few interesting items like the Walker High Def links, the Enacom Speaker filters, and the RC networks that Bobby uses on the Merlinâ€™s as well as quite a bit of discussion in the archives. I feel like I may get some additional RF rejection with the RC in conjunction with my Audioplan cables. RF seems to be one of those things thatâ€™s hard to put your finger on and seems more easily identified after you remove it.
What I havenâ€™t found is any consensus on the right values to use for a filter of this nature. Everyone seems to be in the same ballpark as far as the resistor values go. What I see suggested is usually a 10 ohm and sometimes an 8 ohm. The cap values suggested seem to vary more. I used an online zobel calculator and plugged in an 8 ohm nominal impedance and a frequency of 1.6 Megahertz and got an answer of a cap value of 0.12uF and a resistor value of 10 ohms. I see that Bobby uses a .01uF cap in his network for his speakers. Part of my question is, how much of a role does the impedance of the speaker play in determining the right cap value for this sort of filter? I am quite sure that the tweeter (Foster E110T samarium cobalt, planar) is an 8 ohm impedance, but I donâ€™t think the nominal impedance of the speaker system is much over 4 ohms. Iâ€™m not sure if tuning this filter to the speaker is critical or not? I do realize that using high quality parts for this device IS critical. I plan to place this RC filter across the speaker terminals. Is this value for the cap something that needs to be precise to get the best performance or am I just splitting hairs? This isn't a real expensive filter to build ONCE, but I would like to only built it once.
My amp does not appear to have any sort of RC in itâ€™s output(ARC VT50).

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Topic - RC network(zobel) Radio Frequency speaker filter question?(rather long) - Keith Lockwood 12:23:41 05/9/05 (8)

Thanks to everyone - Keith Lockwood 19:02:08 05/11/05 (0)

Besides Zobel, will ferrite beads help ? (NT) - E 04:40:38 05/10/05 (2)

Re: Besides Zobel, will ferrite beads help ? (NT) - Jon Risch 21:04:41 05/10/05 (0)

Re: Besides Zobel, will ferrite beads help ? (NT) - pkell44 14:35:31 05/10/05 (0)

Re: RC network(zobel) Radio Frequency speaker filter question?(rather long) - pkell44 19:57:17 05/9/05 (0)

Re: RC network(zobel) Radio Frequency speaker filter question?(rather long) - Jon Risch 17:56:47 05/9/05 (0)

My results. - Al Sekela 15:35:21 05/9/05 (1)

Re: My results. - pkell44 14:48:14 05/10/05 (0)

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