From Usenet FYI: "I have conducted several experiments in break-in covering periods as long as 150 hours. What happens is that you can measure a fall in system or driver resonance by several percent along with an increse in compliance of a like amount immediately following an extended break-in period. However if you allow the driver/system to rest for several hours you'll find that the unit returns to its 'fresh' values. Further if you model either set of parameters you'll wind up at the same enclosure requirements for either condition (a lowered Fs and an increase in compliance will be off-setting.) The "most" you can say about extended break-in is that at most a system/driver may "warm-up" but even then its sound will not change. On the other hand, the only negative thing about 'warm-up' is that it can be dangerous in that you can damage the speaker by putting too much currrent into the voice coil for an extended period and/or rip suspension components with too much power. Noise signals are by far the most dangerous. I was involved in a trial testing the EIA 426B power handing standards and found it was possible to actually melt a plastic cone using their long term noise signal. If one is to try-nature with break-in I'd strongly recommend against using noise (as is often suggested) and especially against using the off-polarity test using a pair of systems placed face-to-face out of polarity to reduce the ambient noise of break-in with a noise signal. It's just too darn dangerous; full or partial band signal with equal amplitude over the entire bandwith, unless you 'like' the smell of softening voice coil glue. At DLC Design where they use DUMAX to test linearity of loudspeakers they sometimes need a short break-in period to allow a speaker that has been stored on its back to restore its natural rest position .... and this takes less than a minute. What's the "safest" (as in using a condom for contraception even if you've had a vasectomy) break-in signal? The most comfortable condition is a woofer driven with a sine wave near its resonant frequency in free-air with enough power to allow excursion to attain perhaps half to 2/3 stroke for a relatively short period while you remain in attendance. But even so if there really were an important "break-in" period wouldn't your speakers simply just break-selfs-in during normal use? The only time this might be an important issue is when the break-in period might exceed the product-return time limit. I once tested a product where the owner manual suggested that the speaker would 'improve' over 150 hours of use. I called a local dealer and asked what the store return policy was. As it turned out that was 7-calendar days (meaning that a speaker purchased on Monday had until Saturday to get returned but if you bought on Tuesday you had a full week) so that meant that in order to 'reach' the speaker's full potential a new owner would have to use/break-in the product for 6.25 days non-stop to find out if they 'sounded' as good as he was lead to believe.. This condition is but one of the real reasons that break-in has become an audio urban legend. I understand both the conditions where this might be important. First it tends to reduce buyers remorse; but it also tends to limit customer choice."
Was this post originally written by Tom Nusaine? Sure looks a lot like something he wrote in a recent Audio Critic, IIRC. BGL
