One theory - unclestu52 11:52:34 05/11/07 (0)
 Reducing RF noise improves the whole audible spectrum. - Al Sekela 14:35:02 05/08/07 (1)
 Re: Reducing RF noise improves the whole audible spectrum. - pkell44 12:24:42 05/12/07 (0)

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 One theory - unclestu52 11:52:34 05/11/07 (0)
 Reducing RF noise improves the whole audible spectrum. - Al Sekela 14:35:02 05/08/07 (1)
 Re: Reducing RF noise improves the whole audible spectrum. - pkell44 12:24:42 05/12/07 (0)

The midrange becomes dry and disconnected in the presence of RF noise, leading to a sense of coldness and lack of emotional involvement in the music.

The bass becomes muddy and vague. The best way to tell this is to listen for the sound-stage precision of acoustic bass instruments in good recordings. When RF noise is reduced, they become more palpable and their placement is more clearly defined.

Keep in mind the effect you are hearing may be due to RF noise being coupled back into the main system from the power supplies to the subs, rather than a direct effect on the sub output. All the equipment shares the same AC supply if you trace the wires back far enough. Any piece of equipment, or any non-audio appliance, can generate RF noise that will stimulate resonances on the AC wiring as well as on audio cables.

You can identify the strong RF noise sources outside your audio system by turning off and unplugging the suspects one at a time. If you hear improved sound with the candidate source unplugged, then an in-line filter to that source may give you better sound if it is inconvenient to disconnect it each time you wish to listen. An R-C filter at that point of the AC power wiring may also help.

One solid state designer blames the fact that RF prone devices tend to be solid state (transistors)and blames that on the fact that tube gear has a generally 'warmer' sound. He informed me that his power supplies seem to draw more current than predicted, and inevitably, as his test instrumentation increases in sensitivity and in range, he finds more and more parasitic oscillation in the RF range. Eliminating them produces a significantly warmer sound, he reports (and I do hear it in his designs).

Remember any piece of wire is essentially an antenna. One meter was the standard length for the older car radio antennas, so that gives you an idea of what frequencies a 1 meter IC can pick up. Even circuit board traces can act as an antenna. The consider the amount of wireless devices in current use: cell phones, bluetooths, laptops, remotes. The amount of such devices is constantly growing, pervading our air waves with large amounts of microwave emissions. Your power grid itself is essentially a huge RF network and heaven forbid should your local utility be experimenting with sending computer data on the lines!

Stu

Happy Shielding !