Audio engineering help needed

I’m in the process of digitizing some old reel-to-reel tapes that were kept in the owner’s closet for about 30 years. But when I play them into the computer, there appears to be audio that is backwards playing over the audio that is playing forward. I’m using Adobe Audition to do the cleanup.

Is there any way to separate this so that both sides will come out clean? The tapes belong to an alumnus with whom we’d like to maintain a good relationship.


Realign the playback heads to match the tape. There’s usually a screw on the head mounts to accomplish this.

You can also try this service: King Tet Productions. I’ve used them with good results.

After thirty years there’s going to be a great deal of “print-through.” Basically, the tape is so thin that the magnetic patterns from one layer of tape will influence the layers on either side of it.

Unfortunately, my audio textbooks don’t say how to cope wth print-through except by prevention.

Barely related story: I once bought a cassette tape (I’m pretty sure it was U2’s Boy) which had been assembled incorrectly such that the reels inside the shell were in backward: the side of the tape that was supposed to face outward was facing inward. This resulted in the audio over the entire tape being very faint and, well, backward. I figured out what the problem was through deductive reasoning, but the guy at the store couldn’t wrap his brain around what it meant that the tape was “in backward.” He insisted that the only effect of this would be that side A would be side B and vice versa. Finally, I made him put it in and listen to it and he agreed it warranted replacement.

I’m with Squink on this. Raising or lowering the heads with respect to the tape path should help a great deal.

Most tape recorders for home use (both reel-to-reel and cassette) had record and playback heads that covered only the upper half of the tape. At the end of the tape, the reels were switched (or cassette flipped over), at which point the previous “lower half” of the tape became the new “upper half”, and could be recorded and played back as a “B side” – note that it’s not actually the other side of the tape, just the other half of the tape width. [The less common auto-reverse decks had full-width heads split into four parts (Left + Right for the “forward” direction and Left + Right for the “Reverse”), and could play both A and B “sides” without removing the reels or cassette.].

If one plays back a tape that has been recorded on both “A” and “B” sides, (i.e. neither the upper or lower halves are blank), but with the playback head at the wrong height, one can hear parts of the “B” side backwards while playing the “A” side forwards. I’d be willing to bet – as I’m sure would Squink – that this is what is happening, MsRobyn.

Print-through is magnetic leakage from adjacent winding turns of the tape around the spool, and usually manifests as a pre-echo or post-echo. It is, however, predominantly the same audio track, in the same direction, just time-shifted. As slitterst says, there’s not much that can be done about it after the fact; however, since the OP specifies backwards audio, IMHO it’s much more likely to be head misalignment than print-through.

I reckon you have the wrong tape machine for the job.

It sounds like you have two track tapes and a four track machine.

Print-through on reel to reel machines is not usually much of a problem compared to cassette tape as reel to reel tape is rather thicker, plus the tape bias is very much lower so you don’t get the very much higher levels of magnetic alignments - it can happen but generally because the signal to noise ratio of r2r machins is so much better, you don’t have to drive the tape as hard to lift the wanted signal out of the background noise and hiss.

Reel to reel machines have several differant formats, just because the tape itself looks the same means very little.

Very old machines used to record just one mono track. Play in one direction, rewind to replay.

Old ones record two tracks of mono, one on one half of the tape, turn the tape over, and one more track of mono on the other side.

Quite old ones can do twin track mono - stereo, this is two tracks running parallel one either side of the tape, you can only play this in one direction.

Not quite so old ones can do 4 tracks, or most commonly this is 2 lots of stereo.
You play one way in stereo, turn the tape over, and play the other way in stereo.

Relatively newer machines do the twin stereo but can also can do all 4 tracks in one direction and often include a 4 channel mixer, some even carry time code but this occupies one of the 4 tracks avalailable.

My best guess is that you have a 4 track - ie 2 track stereo machine and you are attempting to play back a 2 track mono - ie one track stereo tape.

Some machines could switch over from one to another in playback, but could only record in 2 track mono, this was fairly common in the 1970’s.

I strongly advise you not to mess with the tape head position unless you have some idea of the format and principles of operation, all you will do is make yourself a lot of problems.

I second casdave. Do NOT adjust the heads. However, I believe you have a tape that was recorded on a 1/2 track consumer stereo, and you’re trying to play it back on a full track professional stereo machine.

Look at the head of your machine. You should see two recording surfaces, each one taking up approximately 1/2 of the tape width. Right? That’s a fulltrack configuration.

A consumer machine also has two tracks, but the head has two recording surfaces on the top half of the head - each about 1/4 of the tape width. That’s a half-track configuration.

Picture the tape blown up. Now picture four equal size tracks on the tape. The top two record one way, then you turn it over, and the same two record the other way, but on the bottom half of the tape. That sounds like the tape you’re trying to play.

Try this: Pan to one side or the other. In effect, cut out one channel. That might help.

If it does, then just digitize in mono.

If not, you’re going to have to find a consumer machine that is the same head format as the recording machine. Without that, you’re stuck, unfortunately.

I’ll be happy to help if there’s any way I can.

casdave and Rico, I know what you’re saying.

These tapes are broadcast-quality and IIRC four-track. The machine I’m using is professional-quality that was hauled out of storage just for this project. Unfortunately, I don’t have access to this over the weekend, so I’ll play with it on Monday. I’ll try digitizing in mono first before I try anything drastic.

Robin, a nonlinear girl in a linear world.

A lot of confusing and conflicting information here. Here’s my two cents.

Let me start by strongly reiterating Rico and casdave’s advice not to adjust any of the screws on the head block. First, it will absolutely, positively not fix the problem you are reporting, and second, it will absolutely, positively screw up the machine’s recording and playback capabilities beyond your ability to restore them. Head settings are NOT a user-adjustable control, and require test tapes and equipment and a knowledgeable technician to adjust correctly. The tapes and the technicians are as rare as hen’s teeth these days. Don’t touch those screws!

I believe that some of the terminology used by previous posters is incorrect, or at least at odds with my experience. Here’s my understanding of several key terms:
[li]Full-track = 1 audio channel across the full width of the tape. Uni-directional recording (i.e., no flipping the reel and playing the other side).[/li]
[li]Half-track = 2 audio channels, each taking about half the width of the tape. Can be bi-directional mono, in which case you can use the other side, or half-track stereo, in which case you can’t. [/li]
[li]Quarter-track = 4 audio channels, each about one quarter of the width of the tape. This can be bi-directional stereo or uni-directional 4-track. (The latter was used mostly for semi-pro and home recording studios.)[/ul][/li]
Antonius Block and Rico assert that on quarter-track recordings the stereo pairs are on the same half of the tape width. This is incorrect. If it were true, then playing back a four-track recording on a two-track machine would not result in the mixture of forward and backward sound that MsRobyn is reporting. Instead, you’d have a mono playback of the two stereo tracks, which, although perhaps not ideal, would be preferable to what you are getting now.

No, in quarter-track recordings left and right of side one are the first and third tracks from the top edge of the tape, and R&L of side two are the second and fourth tracks, respectively. Like so:

Side 1 left

Side 2 right

Side 1 right

Side 2 left

(Ideally, I would have printed the 2nd and 4th tracks upside down.)

The OP states that the tapes in question are four-track (i.e. quarter-track), which leads me to conclude that your playback machine is half-track. If this is the case, there is simply no way to get clean playback of any bi-directionally recorded tapes from this machine. (Of course, anywhere that side two is blank, you will get relatively clean sound.)

But for any quarter-track tapes with content on both sides, this machine will probably not work. You’ll have to find a quarter-track recorder, or use a service like that linked by flex727.

However, some half-track recorders did have quarter-track playback heads. It may be that by changing some jumpers or using different output connections, you could access those heads and get good playback. If you can tell us the brand and model of the machine, we may be able to find out.

BTW, the up-side of using a service is that if these tapes are very old, or not in very good condition (a fair assumption for almost any R-T-R tape) the service will know lots of tricks to preserve them and get the best possible recordings off them. Tapes that are very old, badly stored, cheap quality, or any combination of these three, will often shed the magnetic oxide material as they are played. This clogs up the heads, requiring frequent stops for head cleaning (a PITA), and also degrades the recording further. Some tapes are so bad that may only have one good pass in them. A good service will know how to deal with this. (Hint: it may involve baking them! Really!)

I hope this helps.

Not true, as I have absolutely, positively recovered decent sound from tapes that were recorded on an improperly aligned deck using this technique. Sure, the method may not be for everyone, but lets not get overly dramatic about it here.

It just occurred to me that (as I see casdave had already suggested), if the circumstances are the opposite – a half-track tape played on a quarter-track recorder – you’d get forward playback out of the left channel and backward out of the right. Obviously, if that is the case, just record the left channel, not the right. But since you probably would have figured this out without our help, I suspect my original assumption is correct.

I think they’re four-track. But not having any real experience with tape, I’m really not sure. I do know the tapes are bi-directional. As I said, I will try digitizing them in mono before I ask the engineer to mess with the machine itself. If I need to, I’ll ask what kind of tapes these are.

Actually, these tapes are in very good condition, all things considered. The guy who recorded them kept them in a box in the back of a closet, so they weren’t subjected to repeated playing or extreme conditions. They’re also not commercially-recorded R-T-R tapes that were intended for repeated use. He recorded them on good-quality tape, played them a few times, then stashed them in a box. Based on what I’ve heard so far, I’ll have to do little, if any, noise reduction, and I’ve had no breakage due to the condition of the tape.

Unfortunately, there’s no budget for an outside service. I’m doing this as a favor to an important alumnus, and we have to make the best use of what we’ve got. I’m fortunate that I’ve got engineering support and good tapes to work from. I just want to be able to do the best job possible.


Recording one channel only would never have occurred to me. Thank you!


Not only that, I live in the UK so you’ve a long way to go to find me!

I forgot to mention that, although it’s not relevant to the present case, audio cassette recorders pair the stereo tracks side-by-side on half of the tape, as Antonius Block and Rico described. But not R-T-R recorders.

I stand by my statement. First, we have no indication that the OP’s problem is caused by a recorder with misaligned heads. I’ve presented a much more plausible explanation.

Second, telling someone to adjust the heads is roughly equivalent to telling someone to change his car’s timing belt himself, without knowing if he has any experience working on cars. Yes, if he’s an experienced mechanic he’ll be able to do it. But if not, he has little chance of success, and will almost certainly make things much, much worse. And if he were an experienced mechanic (or audio engineer), he probably wouldn’t have been asking for our advice in the first place.

I believe that your advice was irresponsible and very unlikely to help most people in the OP’s circumstances.

Whatever, It’s still a viable method, and sometimes the only way to deal with the problem.

Lemme get this straight:

Tape-owner comes in with old reel-to-reel tapes that were recorded on some machine thirty years ago.

You pull out some other machine that was on hand to playback the tapes into the computer. Am I right?

This would be effective if the backwards audio is fairly faint and inconsistent. Assuing you are playing back on the right type of machine to begin with the playback heads are not fully aligned with the audio tracks on the tape, and the head is picking up sound from a track meant to be heard only when the reel is flipped. Aligning the heads could help if this is the case, but if this machine is ever to be used for anything again, this work should be done only by someone extremely qualified and familiar with the machine in question.

However, if you simply have the wrong machine for the tape format (the backwards audio is pretty much as loud as the forward audio) no amount of alignment has a prayer of working. Digitizing the tape and hoping to clean it up in post will never happen either.

But print-through wouldn’t sound backwards, it would sound like a forward echo or pre-echo, depending on if the reels were stored “tail out”.

You absolutely must ask what kind of tapes they are.

From the sound of it, I suspect that you have tapes using this sort of format

|   |   |   |   |
| S | R | S | L |
| i |   | i |   |
| d | B | d | B |
| e |   | e |   |
|   | e |   | e |
| A | d | A | d |
|   | i |   | i |
| L | S | R | S |
|   |   |   |   |

And a machine that uses this sort of format

|   |   |   |   |
| S | S | R | L |
| i | i |   |   |
| d | d | B | B |
| e | e |   |   |
|   |   | e | e |
| A | A | d | d |
|   |   | i | i |
| L | R | S | S |
|   |   |   |   |

If this is the case, and the machine only allows you to listen to a left or right channel, you simply turn the knob to the side where you hear forward audio, and you can digitize off that. However, you will only get the left or right channel.

If your machine allows you to listen to all four tracks on the tape, just turn up the ones that sound forward, and you can record right and left off of both sides of the reel.

The worst case scenario is if you are not working with a four-track machine but a two track:

|       |       |
|   S   |   B   |
|   i   |       |
|   d   |   e   |
|   e   |   d   |
|       |   i   |
|   A   |   S   |

In that case you’d be SOL, because the head that reads back the “double-wide” Side A is always going to hear both the forward and backward audio tracks, and nothing can be done about it.

Alignment tapes aren’t as rare as hen’s teeth. I’ve never seen the latter, but have a 7" Sony frequency/azimuth/level tape to go with my 7" and 10" Akai RTR decks. :smiley: