Hey Patrick,

Thanks for the response.

Your point is a good one — quality is certainly the main limiting factor and something I’ve thought a lot about.

I’ve found for most audiobooks, the quality becomes “prohibitively bad” somewhere between 7x-9x (for podcasts, it happens closer to 5.5x-6.5x).

If you want to test this yourself, here is what I did: 
1) I imported five audiobooks into my audio editing software (I actually prefer to use Adobe Premiere instead of Audition)

2) One track at a time, I sped the track up to a high playback speed (for example, 7x). Then, I exported it.

3) Then, I imported this new sped up track and slowed it down by 7x (to try to restore the original).

4) Depending on the track, it was quite hard to recover anything I could understand (or found pleasant to listen to) between 7x-9x (I kept playing with each track until I reached the “quality breaking point”).

This is the best test that I could come up with, given that I can’t actually understand audiobooks at 7–9x (yet). Rightspeed treats the audio a little bit better than Premiere’s speed up process, but it’s probably close.

I encourage you to be patient, play around with the Automatic Speed Ramping feature, and see how far you can take it. (I bet you could conquer 5x for sure).

BTW, I cannot listen at 5x cold either. I usually start my ramp up from 3.5–4x depending on the audiobook.

Hope this helps.