Speaker Asylum

Posted by jonbee (A) on April 13, 2007 at 13:00:32

In Reply to: I read the whole thing... posted by Guth on April 13, 2007 at 11:23:22:

and the xovers are designed around optimal driver parameters. If those params are different because the driver is new, the xovers won't work as designed, which will certainly affect the sound.
I'll try to explain what I think happens, and how it affects the sound. I'll limit my remarks to the measured driver params listed, not the electronic components that Danny mentions, as those changes are harder to measure.
The fs of a driver is related to its lower frequency limit. If a driver is driven below its fs, distortion rises very rapidly with declining frequency. A higher fs in a new also means that there will be a reduction in the LF output of the driver, and at a given frequency below the fs, there will be higher distortion.
The xovers are designed to deliver energy in a defined and fixed band, with usually a fairly shallow rollof at the ends of the band. With a new driver, with a higher fs the lower part of the xover band will be feeding more energy below the fs of the new driver that xover section is feeding. That means higher distortion at the bottom of the driver's range. As the driver fs drops with use, more and more of the xover band will cover the (expanding) driver's sweet spot.

If it is a woofer, this will change the balance of the whole system, making it subjectively brighter overall, with constricted bass. The bass will also exhibit higher distortion, as more power is going to it below its (temporary) higher fs.
For mids and tweeters with high pass filters, the effects are the same, but of course they manifest themselves at the low end of the mid or tweeter range, as aberrations in the lower midrange and low to mid treble.

Xover design theory hasn't changed substantially in decades. Xovers are designed around driver params so that each driver is operating in its sweet spot. If the driver params shift, that driver sweet spot will shift as well.
There is no magic or fuzzy thinking at work here, just the application of loudspeaker engineering basics.