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You bring up an interesting point.

Posted by Lew (A) on May 6, 2001 at 09:11:45

In Reply to: Re: FYI--Bobby Palkovic provides same idea w/his speaks... posted by DK on May 5, 2001 at 19:29:07:

Thanks for your input. At least you went to engineering school at SOME point in your life. Zoebel filters were definitely not taught in medical school. You are making an assumption regarding the HDLs; we have no clue what values Lloyd Walker selected for use in the HDL, since the devices are sealed in a wood case. The values you worked with (0.1uF and 7.5 ohms) are Mark's choices for use at the amplifier end of the chain. As for your extrapolations to spkrs with a variety of impedance loads, that's what I have been thinking about also. Unless the device works only way way above the audio spectrum, one would probably want custom designs for different spkr types (and/or as Mark thinks, for different amplifiers). Yesterday I brought up the question of dynamic spkrs (mostly inductive, per Paul Speltz) vs ESLs (which are like giant capacitors and use a coupling transformer). This reminds me of those black boxes at the ends of MIT spkr wires that are built differently for transistor vs tube amplifiers. So, I will wager that the Walker HDL uses a cap that is << 0.1uF, making it more compatible with a wide variety of spkrs (but of course making it operate only at very high frequencies, at least in the 100s of kHz range). Anyway, it was a good marketing idea to keep the innards of the HDL a deep, dark secret.

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