I have seen some for sale on ebay. Are they really worth the extra $$ and why are they called half speed? I assume it has to do with the speed of the master tape while converting to the LP?

It just means the LP was cut at half speed so to cut down on errors the cutting bit might move towards.

man, that almost made sense.....

In this case, the "master" is the disk which is used to press the vinyl. The master is cut at half speed, which reportedly improves the sound by making the grooves more precise. These master disks were also used in a limited number of pressings (they wear out) compared to the "standard" versions of the same album. I used to buy these in the early 80's, and they indeed sounded much better than their mass-produced counterparts.

I wondered about this half track master idea myself recently (since I noticed that a local company near me does this (or used to) (Mobile Fidelity). I guess it means they cut the master at half speed (16 2/3) while the master tape also runs at half speed (if recorded at 30 inches per second they play it back at 15 inches per second while cutting the master -- which are the speeds generally available on those studio tape decks).

Having watched the cutting of several masters through the microscope at the Scully lathe recently I can say that those lines are not as precise as you might think. The engineer is constantly adjusting the "lines per inch" control and maybe at the slower speed there is more time to make adjustments. I am curious and will ask about this half track master idea next time I speak with him. Now that I think of it, I don't understand why he didn't bring it up when I was cutting because my master tape was done a 30 ips and I know that the Ampex we were using also had the 15 ips speed. I suspect he doesn't believe that there is anything to it, either that, or his Scully (or at least the one we were using) does not have a 16 2/3 speed (yet).

Another thing that has to be monitored is the vacuum system that evacuates the "chips" as the hot stylus is cutting into the lacquer. You do not want any of those pieces remaining on the disc while new grooves are being cut. In addition to everything else, there is a tank of helium which is used to cool the (Westrex) "head" in which the heated stylus is fixed.

This is/was a fun learning experience....

C&S

Most of these MFSL and other half-speed master discs are also pressed onto 'virgin' vinyl, meaning that no reground 'bits' are present in the vinyl, which would cause ticks and pops. There might be other quality control measures as well, such as less discs being pressed off of each mother (negative disc mold), etc.

They do sound fantastic and are well worth the extra $$ if you're a true vinyl entheusiast!

Michael

Most decks used for the two track master have a preview head to allow for automatic adjustment of the groove width.

Decca half speed mastered all of its LPs in the 60s, mainly because of dynamic range limitations in the cutter head amplifier.

Right before CDs became common, Douglas Sax (Sheffield) did about 90% of the masters for top 40 music in the United States.