Is the Kab Speedstrobe necessary with the VPI SDS?

Is it necessary (in order to accurately pinpoint the exact 33 and 1/3 platter speed) to purchase something like a KAB SPEEDSTROBE after buying the VPI SDS?
I have the VPI SDS hooked up to my Aries table and used the KAB Speedstrobe to accurately set the SDS to 331/3 and 45. The SDS can be set in very small increments to accurately obtain both speeds.
No, but it sures makes the job easier and repeatable. The KAB is the best accessory I've ever bought.
I'll second that Narrod. Although $80.00 for a 10 inch plastic disc and a cheap box with a strobe light seemed pretty hard to swallow at first sight, now that I've got it I don't know how I ever lived without it.

Piece of mind. That's what it is. Piece of mind.