As I began researching DIYSG kits I saw numerous folks speak of how these pro-grade woofers needed a break-in period, and this would open up their low end. "Open up" is a vague phrase easily inferred at being rather subjective. After about six months with my three models, I could detect no quantifiable change. As my models are now a couple of years old, I have new information that may give it some quantifiable description, although it's not particularly specific.
A couple of weeks ago I helped a friend with a new system, and calibrated and verified it with the Audyssey Editor app and OmniMic. I decided to do an update on my calibration with my system. I first took a look at where it was with OmniMic. To my surprise, the results didn't match the post-calibration results that are about 1.5 years old. This was particularly noticable in the lower frequency range of the 88 Special center. It's is not that it ever reached particularly low (it still needs to be crossed at 90Hz), but after the new calibration it is definitely smoother in that lower octave. The HTM-12s (L/R mains) have always been smooth, but they even got a little smoother and now cross somewhat easier at 60Hz. The Volt-10LX surrounds were perhaps the smoothest in response of them all! Surprising.
The subs (a mix of JBL 1400PS and Klipsch THX U2) have been smooth and powerful, but...for this calibration I ditched my old Audyssey Sub Equalizer and used the AV-7704 built-in Audyssey SubEQ for two subs. This resulted in very smooth bass but rolled off at about 30Hz-35Hz. With the Editor app and verification passes I was able to smoothly extend that to 25Hz which is the SMPTE spec for dubbing stages.
I was very careful to end this calibration with post-EQ trim settings. I then did extensive listening tests with material I always use for this. I listened with subwoofers on and off, and in 3.2 and 2.2 modes to take the surrounds out of the equation for eval of the front stage. This way I was able to evaluate numerous modes of operation and the various speakers in play. I saved the new configuration to a separate drive/location.
BTW, I use DEQ, but only use the subwoofers for movies or serious listening. And for most 2-channel listening I use Dolby Surround, even if subs are off. The results are quite pleasantly dramatic. Even without the subs, the 88 Special is noticeably more solid in that lower octave of its range. This is most noticeable in male dialogue. It's appropriate; not heavy. Add the subs, and the full-spectrum performance is extremely impressive with all material in a way it wasn't quite before. The upper octaves of these speakers are as wonderfully clear as always. But that lower level smoothing makes them an even better speaker.
I attribute this improvement to several things. The DIYSG components do loosen up and change their performance somewhat. I'm fairly convinced that is what happened here, and that the updated
Audyssey calibration was able to make the best of that. I also think that there were benefits from being more disciplined (thanks to a colleague who is a guru on this stuff) about completing the calibration with setting the trims post-EQ. This almost always is somewhat different than what Audyssey chooses. I will always do that in future calibrations. I think that the built-in SubEQ in the 7704 is superior to the separate Sub Equalizer.
So, as we often do, I found myself checking out favorite music and being happy with the "improvements," but also digging out old stuff not listened to in ages...and finding a new experience.
So in summary, an undated calibration every year or so may be a good practice. Of course, always save your older one so you can return to it if necessary.
For what it's worth.