Lou Judson wrote:
> Pardon this if it is OT - I am curious about this. I have only heard a 
> few Dynagroove records, and rather than do laborius research, can 
> someone describe what is going on with them? All I remember about them 
> is that they had a raised ridge around the circumference to keep them 
> from rubbing together on the grooves... What are the issues about the 
> mastering and pressing? Offlist if I am the only one who wonders...
> <L>

Others may offer specifics, but briefly:

There were two factors in Dynagroove: mechanical and audible. 
Mechanically, they were pressed on thin vinyl; the ridge was needed 
because the resulting disc was so flexible that the upper one could sag 
onto a conventional disc below. The audible difference was recording 
designed for the typical cheap record player on the market. Equalization 
was not the only difference, though real bass was chopped to avoid 
saturating the amp and lower mid boosted to give the illusion of 
low-frequency response. More painfully, highs were prepared (more than 
EQ, but I do not know how) so that distortion would again give the 
effect of high-frequency response that was in fact cut off.

I own several Dynagroove recordings because that is the only way the 
content could be purchased. Where I have bought CD reissues, they have 
shared some of the audible problems. I do not have 4-track and LP copies 
of the same title where the LP is in Dynagroove.

[log in to unmask]