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wrote:

I failed to describe the last case; where the company was asked to submit
samples that were taken directly off the shelf and also broken in for the
required 150 hours.

In that case there were nomeasurable differences between any of the 4 samples I
received that weren't within unit-to-unit tolerances expected with a give
model. These drivers also sounded and measured the same.

I've conducted three experiments that exactly bear on this issue. In each of
these cases I had 12-inch woofers which were conditioned by the manufacturer
to
require 24,48 and 150 hours of "break-in" to perform optimally. In the last
case I asked to manufacturer to provide 4 samples at least one of which had
been subjected to the 150 hour break-in period prior to delivery.

Here's what I found. In the first 2 cases the woofers pre/post break-in
performance was identical.

By this I mean that when the voice coil was still hot after break-in there
were
differences in measured paramters (lower Fs, increased Vas, and increased Re)
but enclosure simulations delivered tbe same optimal enclosure but installing
the woofer in a box and measuring and listening to the sound showed they
sounded exactly the same.

Interestingly I found that the woofer that required 48 hours of break-in;
where
I followed break-in of impedance measurements at 1-hour intervals, had a
slowly
falling Fsb that settled after several hours, BUT slowly drifted back to its
original value after an overnight rest.

In my opinion speakers will "warm-up" but it doesn't change their sound and
if
you let the speaker rest overnight you're right back where you started.