X-max = V.C. Length????

[Zero Cool]

How does one determine the Xmax of a driver?

I have a couple of dead subwoofers that i have removed the cone and V.C from and i am curious what the Xmas is. the MFG of the driver mentioned they had an abundance of xmax but because the drivers are proprietary they cant tell me the specs....so now i am curious.

Wouldn't it just be the length of the V.C. winding???



Zc

[richie00boy]

It's the length of the voicecoil that stays in the gap. But that is only part of the story - how linear that travel is, is another matter.

[Zero Cool]

Ok got it. yes linear another story. I am just curious what "an abundance" of xmax meant to this MFG? these days 2" peak to peak isn't unusual for a 18" driver.


Zc

[oshifis]

Hm, dead drivers, secret specs... I wouldn't spend any effort in them unless they were free.

[AudioFreak]

As an approximation for Peak to Peak Xmax,

For overhung voice coils it will be roughly
Xmax = voice coil length - gap length

For underhung voice coils it will be roughly
Xmax = gap length - voice coil length

[Svante]

Originally posted by AudioFreak
As an approximation for Peak to Peak Xmax,

For overhung voice coils it will be roughly
Xmax = voice coil length - gap length

For underhung voice coils it will be roughly
Xmax = gap length - voice coil length

There are different definitions for xmax. The above would approximately result in the maximum linear peak-to-peak travel of the voice coil. I would say that it is more common to divide this number by 2, to get the one-way peak travel.

Anyway, this means that one has to look careful for how the numbers were obtained when comparing xmax figures between drivers, and in particular between manufacturers.

[AudioFreak]

Originally posted by Svante


There are different definitions for xmax. The above would approximately result in the maximum linear peak-to-peak travel of the voice coil. I would say that it is more common to divide this number by 2, to get the one-way peak travel.

Yes, that's why I specified Peak to Peak.

Originally posted by Svante


Anyway, this means that one has to look careful for how the numbers were obtained when comparing xmax figures between drivers, and in particular between manufacturers.

Indeed not all Xmax (generally accepted as linear travel) figures are equal and then just to confuse matters further there is also Xmech (mechanical travel before damage results) which is also sometimes listed in spec sheets.

[Luke (Uof Iowa)]

Some manufacturers use other measurements such as where BL becomes 70% of at rest or using a DUMAX machine. I think there might be a Klippel tool to measure it as well, but I can't remember one specifically.

[Zero Cool]

Originally posted by AudioFreak
As an approximation for Peak to Peak Xmax,

For overhung voice coils it will be roughly
Xmax = voice coil length - gap length

For underhung voice coils it will be roughly
Xmax = gap length - voice coil length

Ok i measure a 25mm V.C. Winding length. with a top plate of about 8mm. So should i figure 25 / 2 = 12.5mm one way - 8mm plate = 4.5mm xmax? 9mm P-P xmax?? approximately??

I understand that this is not an exact. just a rough guess.


Zc

[FullThrottleRic]

25mm vc - 8mm gap = 17mm peak to peak or 8.5mm one way