What is Xmax vs. Xmech

 

Silver Member
Username: Brynm

Prince Albert, SK Canada

Post Number: 182
Registered: Jul-05
I'm looking at a sub that says it has over 3" Excursion peak to peak, the specs say Xmech is 45mm(1.7") and Xmax is 15mm(.6mm).
 

Silver Member
Username: Brynm

Prince Albert, SK Canada

Post Number: 183
Registered: Jul-05
also if you push it past Xmax does that just mean there will be some distortion?
 

Gold Member
Username: Chaunb3400

Huntsville, Alabama U.S.

Post Number: 4586
Registered: Jul-05
Xmax/Xmech - Maximum peak linear excursion of driver, in meters. "Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone."
 

Gold Member
Username: Mikechec9

Http://www.cardomain.c...

Post Number: 2040
Registered: May-05
as chauncy said, xmax is NOT maximum excursion. maximum excursion is the distance the cone travels before its motion is limited by either the back plate or the physical suspension (spider & surround).
but maximum "linear" excursion is also a misnomer, imo. true, xmax denotes the distance the cone can travel with the coil still in the magnetic gap. and any distance the coil travels outside of that gap is done without control from the motor-hence distortion. but most subs' xmax specs don't portray a true linear excursion at such distances. this (and cost efficiency) is why designs such as adire's xbl2 motor are so unique. you can actually only grab a couple of handfulls of high-excursion subs that remain truly linear up to their proclaimed "incredible" xmax (as a note, some subs add 15% to the xmax figure to allow for 3% 3rd harmonic distortion). some of those handfuls are noted here->http://www.cardomain.com/ride/768492/5
an important point to note is that traditionally, t/s paramaters are only concerned with designing for flat frequency response, and they are conducted with very low power input. as such, xmax is not truly a t/s parameter. that is, it can't be derived from low power input, and it really has fairly little to do with flat frequency response.
what's arguably more important is the total amount of data shown regarding the Drive Unit Measurements At excursion (dumax). instead of merely taking the vc length and subtracting the height of the gap/2, dumax offers a less rudimentary approach by moving the cone through its PRACTICAL range of excursion and measuring the various position dependent characteristics of the sub.
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