Now, after that long winded explanation to my disagreement, here's the short version. Decoupling or isolating the speaker is strictly so the speaker can perform optimally, not simply to improve bass response (it's a byproduct), although for the more younger crowd, an easier way to get them into the habit of doing things properly (but along the way, let's tell 'em why). I will agree, MDF as a spacer ring to replace the plastic rings in factory locations is a good thing, and while clay will isolate the speaker, why risk the mess when a simple foam gasket will do the trick for a solidly mounted speaker/spacer? Not to mention, no one here knows the rate at which the clay will deteriorate over time, if it does at all.
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