One of the reasons that I'm such an advocate of the discontinued Sony
APR-5003V tape recorder is its varispeed is +/- 50%, so I effectively have
coverage from 1.88 to 45 in/s.
Your speed may fall in the hole of some Studers or Otaris that only have
+/- 15-25-35% varispeed.
I respectfully disagree with the comment about the EQ of synthesizing one
between 3.75 and 7.5 as the tape would have been recorded with one of these
The only machines that ran at all these odd speeds were the rim drive
ones--at least in my experience. And they are horrific.
I assume this is a short piece of tape, so the relative pitch shift from
end-to-end would not be as noticeable (you can go 30-60 seconds sometimes
on a rim-drive if you're lucky). I usually piece-wise transfer rim drives
into the computer and then use the continuously adjustable correction
provided by Diamond Cut 5.
As far as "EQ" goes, I think you'll need to see which sounds better 7.5 or
3.75 and go with that and then fix it in the computer. You may be limited
to one or the other if you can't reach the proper speed via the varispeed
from one side or the other. But, after all, you can fix that in your
One trick I've used is playing test tapes off speed and then adjusting in
the computer so the test tape is flat.
Certainly is an interesting problem.