Hi, I am about to do some comparisons of various CD releases of music transferred from old shellacs. Before starting out, I could need some input on what to listen for and suggestions about objective measures of sound quality. I don't have the original 78s myself, which makes it a bit of a mess. On some cds the sound is filtered and eq'd a lot, on others not.
I know some transfers are done at different speeds, is there some way to reliably find the correct speed/length of a song?
If the wrong eq curve is applied to the music, it should theoretically be easy to fix it, but the trouble is I don't know how the music was processed.
You are going to “do some comparisons of various CD releases of music transferred from old shellacs.” It seems to me you have to have well defined goal in order to make a plan for getting there.
One problem facing anyone transferring 78s is the quality of the original. A good original won't need much doing to it to make it sound presentable.
This is very tricky and in many cases it will be impossible to tell. Your only hope of being sure is if there is a clearly audible instrument on the recoding which has a fixed key - EG many brass/wind instruments have Eb as their home key, I believe. Then, as long as you have some way of producing the right note you can check if the speed was correct when the transfer was done.
I understand that you want the eq to be right but I really wouldn't worry about it unless the result offends your ears in some way. Most of the collectors I know use "modern" magnetic cartridges and hi-fi systems to replay their 78s. Consequently they've been subjected to the standard RIAA eq used for LPs. But since that reduces the treble - and hence some of the noise - and boosts the bass a bit they actually prefer the result.
I wouldn't worry too much about playback speed. If it doesn't "sound wrong", Id assume it's correct. Even in the early 1900's they know how to make clocks and it wouldn't have been a big problem to get accurate recording/cutting speed. Players (gramophones)
There were actually quite a range of "standard" speeds, as well as a fair number of "standard" EQs. Every company had their own standards and these changed from time to time.
gradually reduce the speed of a record until it starts to sound sluggish, and then increase it slightly (in my experience the ear is much more sensitive to low speeds than high speeds).
People get the correct playback speed by matching the pitch of the music with the pitch they believe the original performers played at. You can't assume "78rpm" or "80rpm" (plenty of those!) means what it says - especially on early discs.(...)...or by knowledge (e.g. this record company at this time has this equipment) or just by listening and guessing.
These latter ills are more damaging that slightly wrong frequency response or speed. You can easily fix the speed (and sometimes the frequency response) yourself to suit your own tastes.
Spotify, Napster etc etc are great places to search for a popular vintage track and compare the highly variable transfer quality.
Anyway, I'm intrigued - what kind of events are you doing? What kind of music are you playing? Any examples I can look up? DJing with 1930s music sounds cool!