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Have a look at the pic below. There are TS specs for two different drivers, one 12" and one 15", they are both D2 subs and the TS are showing for the same subs with the VCs in series and in parallel. The specs are supplied by the manufacturer and I'd like to know how:

CMS
MMS
MMD

can change just by wiring the VCs differently? Has the manufacturer botched the measurements or have I got something to learn?
 

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hard to say. sometimes manufacturers dont report thing exactly right :p


MMD: not sure how that is supposed to change since this is a simple measurement of weight of the coil and cone. maybe it is some function of MMS?

MMS: "this is the mass of the cone, coil and other moving parts of a driver, including the acoustic load imposed by the air in contact with the driver cone."
means is things like VAS change, so will this. running a coil in series or parallel will change VAS, so likely it will change this.

CMS: "Describes the compliance (ie, the inverse of stiffness) of the suspension. The more compliant a suspension system is, the lower its stiffness, so the higher the Vas will be. Cms is proportional to Vas and thus has the same tolerance ranges."

again, since VAS changes, this will too.
 

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Discussion Starter #3
Yeah, MMD was the real sticker for me! Gotta load them into BBP6 and see what it says, heavy buggers, my SPL days are gone but always interested in playing;)
 

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No, of course the mass and mechanical compliance of the driver doesn't change. the measured parameters change because they're all derived from comparing two impedance curves--one measured without the driver in a box and one with the driver in a box, or one measured without mass added to the cone and one with mass added to the cone. If the apparentl volume if the box isn't calculated perfectly, this can happen. If the mass that's added to the cone isn't securely attached or the mass isn't measured accurately, this can happen. The mass or the box volume provides the baseline for the calculations. The problem is that the measurement technique and the derivation of the parameters leave room for this error. It's really no big deal and the errors are small. I'd just go with these measurements and be done with it.
 
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