Calculating Xmax of Loudspeaker

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
diyAudio Moderator Emeritus
Joined 2001
To my knowledge, you can't get it from Vas, diameter,or any Thiele-Small parameters.

You can get it from length of voice coil and length of magnetic gap, (air gap). These measurements are frequently listed.

The formula: Excursion(+ or -) = (voice coil length - magnetic gap length) / 2.

Example: A speaker with a voice coild length of 17 mm has a 6 mm air gap, (magnetic gap). What is the excursion?

Answer: (17mm - 6mm) / 2 = 11mm / 2 = 5.5 mm.

the excursion is 5.5 mm.

The DuMax method is sometimes used to measure the excursion, and it sometimes comes out just a little bit longer than this method. But the difference is not significant.

This method will give you the answer you need.
 
diyAudio Moderator Emeritus
Joined 2001
PPS: Sometimes a manufacturer will publish the voice coil length, but not the air gap, (magnetic gap), length.

In that case, it probably is a fair guess that for most midbasses and woofers, unless these are special speakers, will have a magnetic gap between 6 and 8 mm. You are probably reasonably safe with that.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.