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
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
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.
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
Zc
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
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
AudioFreak said:
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.
Svante said:
Yes, that's why I specified Peak to Peak.
Svante said:
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.
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.
AudioFreak said:
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
Zero Cool said:
25-8 = 17
17/2 = 8.5mm
Xmax is roughly 8.5mm.
Still, I would be willing to bet that actual Xmax (as defined by Klippel measurements) would be closer to 6 or 7 mm.
Klippel-Light
Hi DevilDriver
You probably will win this bet. I have measured some drivers with 10mm to 15mm Xmax acc. manufacturers specification with a procedure similar to IEC 62458 (Klippel). Many of them ended up with a Xmax of 3-4 mm 😀
Heinrich
Hi DevilDriver
You probably will win this bet. I have measured some drivers with 10mm to 15mm Xmax acc. manufacturers specification with a procedure similar to IEC 62458 (Klippel). Many of them ended up with a Xmax of 3-4 mm 😀
Heinrich
That's correct Heinrich.
And not only far-east type of drivers don't fulfill their Xmax spec, even high-priced drivers fail...
Also the linearity of the suspension Cms(x) sometimes seems to be the limiting factor. Not to mention Le(x) for midbass drivers
.
regards,
Karel
And not only far-east type of drivers don't fulfill their Xmax spec, even high-priced drivers fail...
Also the linearity of the suspension Cms(x) sometimes seems to be the limiting factor. Not to mention Le(x) for midbass drivers
.regards,
Karel
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