Quote:

Originally Posted by

**aarons915**
showed a quote by Dr. Toole addressing the claims of "massless" ribbons and the claimed superiority of them.

Actually, this raised a question for me.

I have a tremendous amount of respect for Toole (I've recently started reading his book) and the general idea of linking objective measurements to subjective preference—great stuff—so I take his points seriously. His argument, conceptually, is that the lower mass of the ribbon vs. a dome is compensated by the more powerful motor that you can mate to a dome tweeter (this is his "my Tesla accelerates really quickly even though it's really heavy" analogy). Seems entirely reasonable.

Then I stopped to think about the math for a second and that's where the question comes up. You, know, Newton's second law, F = MA. What we care about here is acceleration, so A = F/M. To wit, if you have double the mass, you need twice the force.

Consider a good-quality dome tweeter. I searched for "dome tweeter moving mass" and got a very nice

SEAS tweeter, the E0055-06 T35C002. Not the tweeter used in the Sierra-1 but my guess is not all that far off. Moving mass listed at .47 grams.

The Ascend web site says the moving mass of the RAAL used in the Sierra-2 is less than 1/100 of a gram, so let's go with .01 grams.

.47 / .01 = 47, that is, the dome tweeter has almost 50 times the moving mass of the RAAL. So, the motor in the dome has to be able to exert ~50x more force than the motor in the RAAL to have the same acceleration.

So here's my question: is that reasonable?

I readily admit I don't know much about the motors used in typical dome tweeters or the motors used in the RAAL tweeter, but I've handled both a SEAS dome and a RAAL tweeter, and while the dome tweeter is definitely overall more substantial, it's not anything like 50x larger or heavier.

Anyone who knows more want to comment? I'm curious.