reel to reel 7.5 speed to 3.75 speed

An odd question but need some real help.  We have an old reel that was recorded at 3 3/4 ips the slowest speed we have to play back is 7 ips.  Is there a way to record it and then fix it in AA 1.5.  Thanks for all the help.  

James

so everyone knows, we worked it out, it is time/stretch.  need to click the resample button, (so it retains neither pitch nor tempo) and then the ratio is about 200.  Hope this helps anyone else that needs it.  

Thanks

If you have a soundcard that can work with higher sample rates just record at 88.2K (96K) and then playback at normal sample rate.

Your workaround and the above don't however correct for the mismatch of replay EQ between 7.5 and 3.75 ips. although it may sound UK.

I think the equalisation may be OK if he's in the US and the eq ia NAB.
Steve will know, I'm sure. I just think  

I think the equalisation may be OK if he's in the US and the eq ia NAB.
Steve will know, I'm sure. I just think  

Groan... as far as I recall, the NAB turnover figure for 7.5/15ips is the same, but I'm not so sure that this still holds for 3.75/7.5 ips.

But any tape recorded at 3.75ips is unlikely to have accurate EQ anyway - so I'd be rather more inclined to ignore this factor completely, and correct what actually comes back from the tape. By the time you factor dodgy early mics, worn heads, misaligned electronics, tape age (self-demagnetisation effects), etc into the equation, it soon becomes obvious that worrying about the precise turnover point of the tape machine EQ is nowhere in it!

Warning - this is boring.

Okay, I found the numbers. One way or another, there appear to be about 4 standards prevalent in the US for 3.75ips replay, and depending upon the age of the machine concerned you could easily find any of them applied. The HF turnover figures vary, and are either 200, 140, 120 or 90uS HF boost, but the most common NAB recommended one is 90uS for 3.75ips. Also, there is supposed to be a bass boost applied at 3180uS.

The difference in HF response if everything is perfect would be represented by a 2.4dB shelving error (levels too low) if you used the 7.5ips EQ instead of the 3.75ips one. But since this response anomaly generally takes place at frequencies above those which can easily be reproduced at 3.75ips, I still really don't think it's a problem

The other thing worth noting if you are not asleep by now is that at 3.75ips, the NAB and IEC turnover frequencies are the same... 90uS.

James - play back at 7.5IPS (it's unlikely to be 7IPS) and sample at 88.2k, then select "Adjust sample rate" from the Edit menu to read 44100. If you sample at 44.1k and then use the time stretch to change the speed you'll have lost any information above 10kHz that was on the tape - potentially more important than slight EQ errors.

Don't forget too that the tape heads will almost certainly need realigning for the tape - outside of studio-recorded tapes I've almost never come across any that were correctly aligned. Couple misaligned heads with only recording up to 10k and you've got a lot of lost treble information there...

Isn't the quality of 3 3/4 IPS reel recording bad? There is a difference between 15 and 7 1/2 that is very real.

It depends what you mean by bad. On a properly set up professional machine the quality can be pretty good, albeit with a slightly limited HF response. Perfectly adequate for mainly speech recordings. Certainly much better than a lot of today's MP3 quality.  

Isn't the quality of 3 3/4 IPS reel recording bad? There is a difference between 15 and 7 1/2 that is very real.

As ryclark says, it's all relative. You have to bear in mind also that cassettes run at 1 7/8 ips, and have a narrower track width than any open reel format. And if you've ever listened to a Nakamitchi, you'd realise just how damned good that can be - if set up carefully.

As ryclark says, it's all relative. You have to bear in mind also that cassettes run at 1 7/8 ips, and have a narrower track width than any open reel format. And if you've ever listened to a Nakamitchi, you'd realise just how damned good that can be - if set up carefully.

Technically, Fostex's 1/4" 8 track and 1/2" 16 track multitrack machines had track widths on the order of cassettes, but they're a special case.

I never had a Nak - though I drooled over over the thought of one throughout my formative years.  Cassettes DID end up sounding better than they ever had a right to, on the right gear.

Technically, Fostex's 1/4" 8 track and 1/2" 16 track multitrack machines had track widths on the order of cassettes, but they're a special case.

Oh yes - I'd forgotten that they were indeed that narrow. But they went faster, the head design was less compromised, and the rest of the mechanism was a lot more stable than the vast majority of cassette ones, so one tended to forget about this...