Tweeters often arrive with a lisp and after some smooth out. I think this has to do with the ferro fluid evening out around the coil. Not all tweeters do this but it is pretty easy to hear when you get one like this.
Again, this is not 100%, but if you take a woofer out of the box and measure it, the Fs is often a little high and the Vas off (I think it was low). If you play it for some time, the Fs comes down and the Vas goes up (I think it was up). You can also very gently move the woofer cone in and out almost to peak excursion, you will often hear glue cracking and the spider making bending noises, then the measurements will be a lot closer to spec. be careful if you do this, don't damage the woofer.
I did the measurements once to show this some years back.
P
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