Am I mathing this out right?

[Seth]

I can't seem to find a Vd spec for the MCM 55-2421. The datasheet I found (http://www.farnell.com/datasheets/23295 ... 1561925106) does list a piston diameter of 163mm and an xmax of 16mm... which, if my math is correct, equates to a Vd of 333.7cc which is more than a Kappalite 10. That can't be right, can it? 2 of them would have more volume potential than a LAB12? Naaaawwww, can't be

[Bill Fitzmaurice]

With Pe of 120w the MCM isn't going to compete against the other drivers. I'm sure it's not built to pro-sound standards either.

[Seth]

With Pe of 120w the MCM isn't going to compete against the other drivers. I'm sure it's not built to pro-sound standards either.

That's what I assumed. I have four of them, new in box, collecting dust in the garage. I'm toying with the idea of making some T18's or TAT's for a garage PA. I was just a little surprised at the figure. Guess I did math it correctly.

All the plans make it very clear that "output isn’t about watts, it’s about driver displacement". I think there's a learnable moment here for myself. But, I'm not sure I have the wherewithal at the moment to wrap my mind around why, in this case, it doesn't hold true.

[Seth]

Side note: I wish there was a half space response chart for the T18. Would I just subtract 12dB from the "in room" response to get close?

[Bill Fitzmaurice]

That would be reasonably close. Vd is more of a limiting factor than Pe mainly with pro-sound drivers. It tends to be the other way around with consumer grade drivers.

[Seth]

Is it that xmax is not achievable at the Pe?

[Bill Fitzmaurice]

It's that pro-sound and consumer sound drivers are built with different goals.

[Seth]

Don't go getting all scientific on me. You're liable to confuse me.

No worries... not that important.

I think these four MCM drivers may just make it into a monster 4xTTLS in one T60 sized cab. Just because. We'll see.