"Backwards- Mastering"

[subkontrabob]

Hi,

I had a few odd thoughts the other day that I would like to discuss.
To put it short, I've been thinking about the concept of playing audio backwards at the mastering/cutting phase.

Let me outline my train of thought:
A basic fact we all know is that any kind of audio consists mostly of transients (= fast impulses) and a decay tail. So in the natural order of a sound, and the corresponding electrical signal you have at first a short burst with a very high slew rate, followed by a decay phase with a much slower one (well, I don't know if slew rate is an appropriate term to describe the decay phase, but you probably get what I mean).

As an electromechanical system, any cutterhead is subject to inertia, which it always has to overcome. It's easier for the needle to stop back to the center point than to accelerate and follow a transient signal. Another limiting factor is the inductance of the voicecoils.

By cutting backwards, the head would first cut the decay tail that is slowly rising, accelerate to the peak, and then slow down really fast during the transient.

I'm not sure if it would be an advantage, but another side- effect of this method is that compression with slower attacks could be applied. Maybe this would result in more subtle compression?

I suspect it would be possible to improve quality by cutting "backwards", because:

- influence of voice coil inductance on transients is decreased
- influence of inertia on the moving parts is turned to benefit
- more accurate signal tracking
- increased thermal performance because heat builds up slower -> system has more time to dissipate it


disadvantages:

- you would have to cut from inside out
- you would have to rotate the cutterhead 180°
- you would have to reverse platter turning direction
- you would have to calculate your starting point in advance, or allow for a gap between the edge of the record and the starting groove (this might look odd, but turn out to be a benefit in regards to stamper robustness)


My question to the old trolls:
1. Has anyone done this kind of "backwards processing"? (I mean only the mastering part, not cutting)
2. Has anyone done "backwards cutting"?
3. Does this make any sense at all?

[Kris D]

Wow!! This is very strange my friend and I have been discussing the same concept. I read in the Morrison book how they used to run tape backwards into compressors to make it easier for the equipment to handle the transients and reduce thump. This gave me the idea the same could be applied to the cutting process. Using a sled type lathe (VMS,Scully,Arcturus etc) one could machine a bracket that would shift the head mount brackets to the left far enough (5 or 6"?) to allow cutting from the opposite side. The motor would then need to be set to run in reverse as well as engaging the lathe in the inside out position for outside in cuts. I have not thought about stereo applications i.e. if you would need to reverse left and right inputs?
This could be the wave of the future but something tells me Emory Cook or Howard Holzer tried this 50 years ago!!

First person to cut a record this way wins an all expenses paid trip to the former site of the Presto factory in scenic Paramus New Jersey*

*Paid for by a generous donation from the Lathe Trolls Pension Fund.

[Nickou]

that is a real concept

I love

[mossboss]

First person to cut a record this way wins an all expenses paid trip to the former site of the Presto factory in scenic Paramus New Jersey*

*Paid for by a generous donation from the Lathe Trolls Pension Fund.

Hey K D
May be this would a better place to visit at the expense of the SSLT fund
http://www.villagevoice.com/related/to/Pilgrim+State+Psychiatric+Center
I wonder if they still perform lobotomy's there?
If we where to modify existing lathes so as to do that, even though is most likely a great concept, may be we do need one of those
Seriously,
I must admit It is the first time I am reading about it
As a concept put forward by Bob it makes a lot of sense
I wonder if it was ever approached by anyone else in the past or anything ever being published about it
Cheers

[subkontrabob]

I read in the Morrison book how they used to run tape backwards into compressors to make it easier for the equipment to handle the transients and reduce thump.

Alas, that's where it comes from! I have the Morrison book too, totally forgot it is mentioned there.

And mossy is right, cannibalizing an existing Neumann would probably be a terminal sin, but maybe a presto?? *duck and cover*

Seriously, because the cutterhead would need to be turned 180°, the whole suspension and slide arrangement has to be rebuilt. Maybe it is time for a new lathe design after all......

by the way, check out this crazy guy from Romania. It's not a lathe, but a veeeery strange DIY high end turntable, maybe it could be converted to a lathe?

http://www.vinylengine.com/phpBB2/viewtopic.php?t=166&postdays=0&postorder=asc&start=423

and this german guy has built a nice DIY stroboscope feedback system to keep his platter steady without wow and flutter (sorry it's in german):

http://www.rstaudio.de/TT1/tt1_de.html

[Kris D]

Hi - The Mods are not as severe as you would think. All one really needs to do is get the arm to travel further to the left. Because the table is turning backwards and the head is on the other side of the center pin it is an exact mirror of standard cutting. The lacquer spins past the stylus in the same way it would usually, you do not need to turn the head around or change the suspension of it. In my previous post I stated one would set the machine to inside out for this type of cut and that is incorrect. I failed to think that the song starts at the end (this is confusing and hurts my brain!!) The best lathe to try this with would be a Scully in my opinion. The overhead/sled has enough mass to handle the extension of the head mount. You would probably not be able to use vacuum hold down due to clearance issues.

Mossboss-
I thought cutting in the Southern hemisphere was already done backwards due to the coriolis forces??

- Kris

[JayDC]

coriolis forces??

- Kris

You mean how the toilet that is flushed down there, spins the opposite way?..

I have been repeatedly told that this is just a myth, and that it doesn't happen.

like all last week, and this week, oddly enough..

[Kris D]

http://mynasadata.larc.nasa.gov/glossary.php?&word=Coriolis%20force

[subkontrabob]

In my previous post I stated one would set the machine to inside out for this type of cut and that is incorrect.

I get the idea, makes perfect sense actually! You're right, the cutterhead wouldn't need to be flipped, only the platter direction has to be reversed With the extension it will technically cut from inside out, although the sled moves in the regular way.

The extension would have to be 7" - 8", that's long! Do you think the bearings can handle the extra weight and leverage?

[emorritt]

If we cut backwards then how will we cut records with secret reverse messages??? I guess they'd be secret forwards messages!?!?!??

[greybeard]

`They're coming to take me away, ha ha, they're coming to take me away,
ho ho, he he, ha ha, to the funny farm, where life is beautiful all the
time, and I'll be happy to see those nice young men in their clean white
coats...' - Napoleon XIII

somewhere (over the rainbow?) I have this 7" record. The B-side has all the sound in reverse.

Now, the basic principle and its advantages that subkontrabob described were given in US Patent No. 2,466,186 assigned to The Brush Development Company. It was filed in 1943 and issued in 1949.

[JayDC]

If we cut backwards then how will we cut records with secret reverse messages??? I guess they'd be secret forwards messages!?!?!??

I agree, you can't cut the devils music backwards.. it defeats the purpose..

[Axon]

I don't think this will work, because:

When you flip the handedness of the lathe and cutting apparatus (ie to cut counterclockwise so as to be played clockwise), you're also flipping the sign of the VMA: as far as playback is concerned, it will appear as if the cutting head is mounted so that the VMA is at a very large, and negative, angle.

At which point, instead of dealing with a vertical tracking error of perhaps 5-10 degrees, you'll have an error of 30-50 degrees. For stereo audio, that's probably going to cause more audible distortion than whatever improvements might occur for cutting transients.

[subkontrabob]

I don't think this will work, because:

When you flip the handedness of the lathe and cutting apparatus (ie to cut counterclockwise so as to be played clockwise), you're also flipping the sign of the VMA: as far as playback is concerned, it will appear as if the cutting head is mounted so that the VMA is at a very large, and negative, angle.

At which point, instead of dealing with a vertical tracking error of perhaps 5-10 degrees, you'll have an error of 30-50 degrees. For stereo audio, that's probably going to cause more audible distortion than whatever improvements might occur for cutting transients.

what is VMA?

[leo gonzalez]

Mossboss-
I thought cutting in the Southern hemisphere was already done backwards due to the coriolis forces??

- Kris

YOU CAN ALSO CUT A LOUDER RECORD THE CLOSER YOU ARE TO THE NORTH POLE

[Axon]

what is VMA?

Vertical modulation angle, aka the cutting equivalent of VTA.

[maniman]

If someone known very well the VR and have the needed expansions (and he are totally insane ) , I guess can do that , turn the carriage (as far as i know the part between the screw and the carriage is the most delicate part of the overhead... own risk ) , inside/out expansion , and rest to know if the extra platter can go reverse (or can invert the motor and maybe the technics too , both are sync I guess , i havent d expansion).

hehe if I were in a madhouse and had a VR inside evidently I would try.

Best Regards
Mani

[subkontrabob]

I don't think this will work, because:

When you flip the handedness of the lathe and cutting apparatus (ie to cut counterclockwise so as to be played clockwise), you're also flipping the sign of the VMA: as far as playback is concerned, it will appear as if the cutting head is mounted so that the VMA is at a very large, and negative, angle.

At which point, instead of dealing with a vertical tracking error of perhaps 5-10 degrees, you'll have an error of 30-50 degrees. For stereo audio, that's probably going to cause more audible distortion than whatever improvements might occur for cutting transients.

Is the VMA a VMS specific component?

If you have a lathe with a overhead system that spans the whole platter (like the Fairchilds and the Lyrec on the photos that have been posted here) AND allows the cutterhead to travel to the left side also, it would be possible to cut "backwards" inside out without switching the cutterhead 180°, like Kris pointed out.

[mossboss]

Please Guys
See Greybeard's post on this
Is quite appropriate
Else
JDC's boat trip
Cheers

[leo gonzalez]

Hi, I suspect it would be possible to improve quality by cutting "backwards", because:

- influence of voice coil inductance on transients is decreased
- influence of inertia on the moving parts is turned to benefit
- more accurate signal tracking
- increased thermal performance because heat builds up slower -> system has more time to dissipate it

cut half speed if this is where you're going.

i would add antoher disadvantage:

recently i had a cut with a 10+ min track of just backwards piano. it was cool but i can't see myself cutting every program backwards unless i'd do it in mute.

would you really see yourself cutting records backwards?

make a poll and vote, ha!