Why are my reel to reel tapes running so fast?
June 8, 2010 6:01 PM
I want to transfer a bunch of reel-to-reel tapes to digital audio, but when I play them back, the sound is too fast/high pitched. Is there a standard percentage that I can slow things down by?
First, the problem, then the specs.
I have a bunch of reel-to-reel tapes. When I put one on this reel-to-reel machine (AKAI GX-747dbx) I received, they play really fast. The tapes say 3¾ on them, and there is a "7½ / 3¾" switch on the player, but even when I switch it into 3 3/4 mode, it's much too fast (the 7 1/2 is, of course, even faster than that). Fiddling with other dials/knobs = no dice. There's a "pitch control", but that doesn't help much.
The player itself seems to be fine, though - when I play some reels recorded off of WRKS FM (nyc) in the early 80s, it plays back beautifully.
What I think I have here is an incompatibility issue - the reel-to-reel machine I have is significantly newer than the tapes I have. I am thinking that I could simply play back the sound as-is, and then digitally slow the "chipmunked" sound down using an audio editing program. I've actually done this, and it sounds okay. The issue here is, however, that I don't know exactly how slow I should be going. I can kinda ballpark it, but I'd like to be accurate.
So, the question: Is there a standard percentage that I can slow down by: e.g. "okay, dude, what you need to do is record these things at the normal speed your player is going at, and then slow them down to 60% of the original speed using your computer"?
Also: if I do this, will I be losing a lot of sound quality? (these tapes are mainly just people talking, so I don't need awesome quality - but I'd like it to be as good as possible).
Any other tips or warnings are, of course, much appreciated.
Equipment Specs:
AKAI GX-747dbx (picture/info here)
Macbook (first generation). I can use Ableton Live, Audacity, Logic, etc.
Media Specs:
25 or so 3 3/4 tape reels,
10 or so 1 7/8 (I think) tape reels (I haven't played any of these, so I don't know what they sound like - any hints here?)
these all were taped in the mid 60s (and seem to have been very carefully stored. I have heard of "baking", but it doesn't look like I'll have to do that).
Additional note: some of these tapes seem to be playing such that going playing them in one direction gives you normal sound in the left channel, and another, backwards sound on the right channel.
First, the problem, then the specs.
I have a bunch of reel-to-reel tapes. When I put one on this reel-to-reel machine (AKAI GX-747dbx) I received, they play really fast. The tapes say 3¾ on them, and there is a "7½ / 3¾" switch on the player, but even when I switch it into 3 3/4 mode, it's much too fast (the 7 1/2 is, of course, even faster than that). Fiddling with other dials/knobs = no dice. There's a "pitch control", but that doesn't help much.
The player itself seems to be fine, though - when I play some reels recorded off of WRKS FM (nyc) in the early 80s, it plays back beautifully.
What I think I have here is an incompatibility issue - the reel-to-reel machine I have is significantly newer than the tapes I have. I am thinking that I could simply play back the sound as-is, and then digitally slow the "chipmunked" sound down using an audio editing program. I've actually done this, and it sounds okay. The issue here is, however, that I don't know exactly how slow I should be going. I can kinda ballpark it, but I'd like to be accurate.
So, the question: Is there a standard percentage that I can slow down by: e.g. "okay, dude, what you need to do is record these things at the normal speed your player is going at, and then slow them down to 60% of the original speed using your computer"?
Also: if I do this, will I be losing a lot of sound quality? (these tapes are mainly just people talking, so I don't need awesome quality - but I'd like it to be as good as possible).
Any other tips or warnings are, of course, much appreciated.
Equipment Specs:
AKAI GX-747dbx (picture/info here)
Macbook (first generation). I can use Ableton Live, Audacity, Logic, etc.
Media Specs:
25 or so 3 3/4 tape reels,
10 or so 1 7/8 (I think) tape reels (I haven't played any of these, so I don't know what they sound like - any hints here?)
these all were taped in the mid 60s (and seem to have been very carefully stored. I have heard of "baking", but it doesn't look like I'll have to do that).
Additional note: some of these tapes seem to be playing such that going playing them in one direction gives you normal sound in the left channel, and another, backwards sound on the right channel.
It's pretty impossible to answer this question, since who knows what could be on there, recorded at literally any speed, but it's probably just a mislabeled 1-7/8ips reel. Try cutting the speed in half.
posted by Sys Rq at 6:32 PM on June 8, 2010
posted by Sys Rq at 6:32 PM on June 8, 2010
Re: some of these tapes seem to be playing such that going playing them in one direction gives you normal sound in the left channel, and another, backwards sound on the right channel.
Look here, third paragraph from the bottom. They are probably mono tapes, but they could be non-standard stereo. You might be able to twiddle with the head position.
Regarding the speed, they are probably 1 7/8. So, 50%. That's not going to sound great on a good day, but when doing the digitizing, run up the sample rate to something like 92,000 samples per second, 32 bits per sample. Since it's going twice as fast, all your signals are going to be twice as high. A 10,000 hz sound on the tape is going to come out as 20,000 hz. You want to make sure you capture everything. And instead of doing a complicated pitch shift, try simply changing the digital sample rate without modifying the track itself. The digital equivalent of turning it to half speed.
posted by gjc at 6:53 PM on June 8, 2010
Look here, third paragraph from the bottom. They are probably mono tapes, but they could be non-standard stereo. You might be able to twiddle with the head position.
Regarding the speed, they are probably 1 7/8. So, 50%. That's not going to sound great on a good day, but when doing the digitizing, run up the sample rate to something like 92,000 samples per second, 32 bits per sample. Since it's going twice as fast, all your signals are going to be twice as high. A 10,000 hz sound on the tape is going to come out as 20,000 hz. You want to make sure you capture everything. And instead of doing a complicated pitch shift, try simply changing the digital sample rate without modifying the track itself. The digital equivalent of turning it to half speed.
posted by gjc at 6:53 PM on June 8, 2010
There were a few different standards for tape speeds but 1⅞ in/s (or 4.76 cm/s) is likely to be correct for the ones you have (the original recordist may have been trying to economise, or perhaps didn't have a faster recorder). It is possible but unlikely that they were recorded any slower (15/16ths in/s) -- very rare.
The ones that sound backwards on the right channel were probably recorded one side in mono, then at the end of the tape the full reel turned over (and reloaded on the left hand side of the recorder) and recorded on the other "side" (thus returning the tape from the take-up spool back to the original spool, instead of rewinding). A full width mono recording would cause the effect you're hearing, so I'd suggest disregard the right channel whilst listening to those.
To complete your task it's important to get the best digital copy in an editable lossless format first (you can compress it later) so record to WAV, choose 24bit for maximum headroom - your meters can afford to peak at around -12dB, and since you're going to be slowing it down I'd choose a high sample rate - 88.2 divides nicely in to 44.1KHz for CD quality mastering later.
Your recording tool of choice (I think most of the ones you mention will be fine) should let you reduce playback speed by 50% - remember you need to pitch down too -- some new speed controls on Logic for instance can alter the speed but not pitch, which is not what you want.
When you make the master recording, leave the Reel to Reel machines pitch control centred (+/-0). Don't forget to test a few minutes first, for each different type of recording.
Once you're happy with your WAVs you can consider whether any filters, noise reduction or further digital processing will enhance the quality, but work on copies and keep the new digital 'masters' intact just in case. Then you can compress to OGG or MP3 for daily use -- I highly recommend the freely available LAME encoder which sounds much better than iTunes at any rate. I'd also keep an archive (lossless) copy in FLAC as the best way to preserve your bit of history for the future, which will then allow you to reclaim the disk space used by the WAVs.
Best wishes with your project, and feel free to mefimail me if anything isn't clear.
posted by dirm at 7:17 PM on June 8, 2010
The ones that sound backwards on the right channel were probably recorded one side in mono, then at the end of the tape the full reel turned over (and reloaded on the left hand side of the recorder) and recorded on the other "side" (thus returning the tape from the take-up spool back to the original spool, instead of rewinding). A full width mono recording would cause the effect you're hearing, so I'd suggest disregard the right channel whilst listening to those.
To complete your task it's important to get the best digital copy in an editable lossless format first (you can compress it later) so record to WAV, choose 24bit for maximum headroom - your meters can afford to peak at around -12dB, and since you're going to be slowing it down I'd choose a high sample rate - 88.2 divides nicely in to 44.1KHz for CD quality mastering later.
Your recording tool of choice (I think most of the ones you mention will be fine) should let you reduce playback speed by 50% - remember you need to pitch down too -- some new speed controls on Logic for instance can alter the speed but not pitch, which is not what you want.
When you make the master recording, leave the Reel to Reel machines pitch control centred (+/-0). Don't forget to test a few minutes first, for each different type of recording.
Once you're happy with your WAVs you can consider whether any filters, noise reduction or further digital processing will enhance the quality, but work on copies and keep the new digital 'masters' intact just in case. Then you can compress to OGG or MP3 for daily use -- I highly recommend the freely available LAME encoder which sounds much better than iTunes at any rate. I'd also keep an archive (lossless) copy in FLAC as the best way to preserve your bit of history for the future, which will then allow you to reclaim the disk space used by the WAVs.
Best wishes with your project, and feel free to mefimail me if anything isn't clear.
posted by dirm at 7:17 PM on June 8, 2010
Apologies for the late answer, but everyone who said to cut the rate by 50% was absolutely right on - thanks!
posted by dihutenosa at 11:54 PM on June 20, 2010
posted by dihutenosa at 11:54 PM on June 20, 2010
This thread is closed to new comments.
posted by Marky at 6:30 PM on June 8, 2010