Hi :] is anyone who knows how to measure Xmax ?

I want to build on my own hands subwoofer and I have driver but I didn't know its parameters than I used this measuring metod: http://www.diysubwoofers.org/measure.htm but there isn't anything about measuring Xmaxwho don't know what is it :]Xmax:Excursion (Xmas): (Required.) The maximum or peak linear excursion of the loudspeaker. It is usually defined as the distance the voice coil can travel in one direction and still maintain a constant number of turns in the gap of the magnet. This definition yields the maximum excursion before distortion occurs. Sometimes Xmax is defined as the distance the voice coil/loudspeaker cone can travel in one direction before the loudspeaker is physically damaged. and my question would be:How to measure Xmax ????

The only way I know of is destructive...  not really  }:>  If the voice coil and magnetic gap heights are provided, subtract the gap height from the coil height, then divide by 2.  If the VC is shorter than the MG, then you are one of the lucky owners of an underhung woofer, and you do it the other way i.e gap height minus coil height divided by two.  Example, if the gap height is specified at 10mm, and the coil height is specified as 20mm, then the formula plugs in like this:  20-10=10  10/2=5.  Your Xmax would be ±5mm on this particular driver or 10mm, but most calculations are based on the one-way distance, or 5mm.  This formula will give you the TRUE Xmax of the driver; the linear Xmax, not the mechanical Xmax.  If you want to figure the physical Xmax (a parameter you would NEVER use in figuring an enclosure) it IS a destructive test, and usually involves fumes from a very hot coil of wire  <grin>  Luckily the diysubwoofers site looks like it requires the linear displacement of the driver.  I believe there are ways to figure it by using other parameters provided, but I do not know them, I am just pretty sure that a speaker engineer friend of mine who works at Harman/JBL does know how to do it...  but then he spent years in school to learn how to do it...It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

hmmmm :\ how I understand I must destruct driver.... :\sorry for my English because I am from Lithuania.. :]I thought that there is an easier way to measure Xmax :(because it looks so simple :]

Exactly what manufacturer is the driver from, and what is the EXACT model.  I can maybe do a bit of research for you, I have quite a library at my disposal.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

hmmm..... this driver is very old but stil in good condition :\ there are not any letters on it :(but this driver is taken from "Radiotechnika S-50" model speakers if you know it.... the main page of this manufacturer is http://www.rrr.lv/in my country is very populiar S-90 model speakers :]thay are very old too but until now a lot of people say just a good words about them and they use ithmmm if you have any information about S-50 model than write it here... :] but for me the most important is low frequency driver from "Radiotechnika S-50" speakers