Building, Cutting, and Playing the World's Largest Record

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The high frequency response of a scaled up player like that would be very poor, and stereo would likely
be out of the question.
Ahh OK. If this would be a demo piece project, music with maximum midrange content and mono cartridge can be used to make it simple. A friend gave me Vintage Acos electric phono cartridge. Quite big actually almost 2"x2"x1.5". I wonder if it can be used.
 

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In the 1950's it was common for drugstores and music stores to have a booth with a machine to cut directly to a plastic disc similar to the Decelith alternative to acetate on metal.

'78's were shellac on a harder core. Which is why they cracked, which led to the flexible vinyl 'unbreakable' records. It was mostly durability that pushed to vinyl, not fidelity, though I imagine the damping is better.

Maybe you could go for mono in the old 78-rpm conical-stylus groove dimensions? After all, most 78s were mono too. I think you can drive a stereo cutting head with the channels in-phase to create a vertically modulated mono groove if you can fit a suitable cutting stylus?

But it should be possible to create full-fidelity stereo, perhaps even better performance.

Remember that you don't have to cut in real time at full speed; these days you can slow down the disc and the driving signal to match. Don't bother with cutting the entire disc, just cut the outer 4 inches, and it will still play a lot of music for a long time. That way you just make a new spindle and platter with its edge sruck under a standard cutting lathe and head.

That also solves most playback issues. Mount a standard tonearm on a larger swing-away shelf or arm or a hinged table leaf or something like that. With such a big disc the groove curvature is such a large radius that anti-skate will be negligible. I can envision a completely standard Garrard zero-100 articulated pentograph-like dual arm mounted to a fold-down hinged table working just fine with the anti-skate dialed out. And it would be MORE recognizable as a real record-player!

The more I think about it, you should be able to do this easily and cheaply with mostly standard hardware if you can get a mastering cutting lathe with an open arm shape donated for the tax write off.

You could make it really kick butt with some testing and coming up with your own equalization curve, since you don't need the compact long-playing groove of an LP, and you can certainly go for a groove speed that's more optimum than an LP, or than even a large 78 EP.

Why go so enormous if you can break the record with minor mods to standard equipment with a 14" record?
 
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So the goal of this is to produce the world's largest playable record (verified through Guinness) and earn the charity (musack.org) some press. I don't think hi-fi is required here, but it should do a relatively decent job. It can't be too crappy, because my personal "audiophile" cred is on the line! :)

I listened to the version of the 3D printed record, and it sounded pretty bad. It's a great concept, but the practicality isn't there. Also, I think that might be even harder at the 4' scale we're shooting for.

I do not want to scale up the size of the groove and have deal with reinventing the resonance solutions, etc. My goal is to turn the record at a low RPM and get a similar needle speed to a 78.

I just found a record cutting forum and it looks like they have a lot of DIY solutions to pour over.
 
You guys always manage to reply while I'm mid-writing mine! Great suggestions cyclecamper! The hard part is finding an existing open-arm lathe to use. A functioning one can make money, and people aren't willing to risk tearing it down to use the arm for my purposes. My plan is to make a head and drive it across on a homemade screw mount.

And your link to The Secret Society of Lathe Trolls • Index page is very timely! Found 'em last night and jumped through the registration hoops.
 
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What a cool project! Really want to hear and see it when it's complete.

I've used a few old record cutters made for home. They basically just had a big, heavy tonearm with a cutter at the end. Of course the tonearm was driven across for cutting.
I agree with Ray and Cycle on their ideas. Use an arm with a pivot at the end. It will still look classic, but behave much better than a giant arm with a pivot at the back. Go for the big, mono groove, a la 78 RPM. That's going to be much more robust than the micorgroove style from the 33 1/3 LP.

You may be able to find one of these old cutting heads that was made for home use, or even the whole player/cutter combo. If so, that would be my path to making something quickly with a good shot at success. And with a disk that huge, you probably want low RPM, like 16 RPM or even lower. The groove velocity is going to be rather high on a 4' or 6' diameter disk.

Best of luck with the project and thanks for including us! :up: :up:
 
For playback, build a long robust arm, drive it slowly in an arc across the record at close to required tracking speed. At the speed this is going to play you could even wind it across by hand. At the end of the robust arm, mount a standard tone-arm. The tone-arm tracks the record, the long arm carries the tone-arm. The long arm could even hide the real tone-arm so it looks like one huge tone arm.
 
While searching for long tonearm I found this. May be it will help in some way. If you are aiming for 4' record player and if above tonearm looks thin you can cover it with foam or something so aesthetically it looks proportionate. May be it will damp resonance too. Thanks for sharing interesting project.
Regards.
 
Great pics for long tone-arm ideas! It's good to know that the problem has been tackled before. I doubt the guy would be smiling next to his creation if it didn't work decently.

I talked with a guy I found on the record-cutting forum. He's got a few DIY solutions under his belt and he's local and willing to help me out. We're getting together next week to discuss how this thing is going to be designed.

In the meantime I'm going to finish the CAD model of the turntable and do the boring bookkeeping stuff for the project. I may not post for a little bit, but progress is happening! I'll be back soon with some renderings and probably more questions.

Thanks for all the help guys!
 
So the goal of this is to produce the world's largest playable record (verified through Guinness) and earn the charity (musack.org) some press. I don't think hi-fi is required here, but it should do a relatively decent job. It can't be too crappy, because my personal "audiophile" cred is on the line! :)

I listened to the version of the 3D printed record, and it sounded pretty bad. It's a great concept, but the practicality isn't there.

I just found a record cutting forum and it looks like they have a lot of DIY solutions to pour over.
Does it NEED to be an LP-sized microgroove to win the record? I think the large 78 sized groove will save a lot of trouble - cutters for it may be easier to get, and you can get the larger 78 stylus for many LP cartridges with a replacable stylus. I've used a Grado Blue with a 78 stylus for it, and with the heavier stylus pressure and different compliance, having a possibly too-low arm resonance on a long arm won't be a problem. I've done some 78 Audiodisc-style recordings (recorded at both 78 and 33 - sometimes on the same side of the record!) onto CDR that sound quite good, certainly MUCH better than that 3d-printed record. And with the possible problems with microgroove, a 78-sized groove could come out sounding better anyway. No doubt those on that forum can advise you on this.
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Why go so enormous if you can break the record with minor mods to standard equipment with a 14" record?
Well, firstly, larger records already exist. There are 16" transcription LPs that were used to distribute national programs to radio stations - they play for about a half hour a side at 33. I got one on ebay many years ago and still haven't made a TT to play it on.
Transcription disc - Wikipedia, the free encyclopedia

Also, by Really Thinking Big, one makes it a Big Deal out of it for the charity as well as discouraging others from quickly and incrementally taking the, um, Guinness "record."
 
It might be possible to cut the disc with a CO2 laser from a laser cutting setup. You modulate the laser power to change the depth of the cut with one channel of audio and then modulate the side to side position of the laser with the other channel of audio? You would probably have to make your own pickup for it, but if you're doing a giant record, a giant turntable, a giant tonearm, why not a giant pickup?
 
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