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Abbey Road Plate Reverbs

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Abbey Road Plate Reverbs

Postby Hugh Robjohns » Mon May 17, 2021 11:00 am

Came across an interesting post and image on the Abbey Road Facebook feed that I thought worth sharing:

Abbey Road plates.jpg


Abbey Road wrote:In 1947, artificial reverb as we know it today was born in a bathroom — Bill Putnam’s bathroom, to be exact. It provided an echo chamber effect for the Harmonicats’ recording of ‘Peg O’ My Heart’. Echo chambers remained the dominant type of artificial reverb until 1957 when EMI introduced the first plate reverb.

Used most prominently in the ‘60s and ‘70s by pioneering bands including The Beatles and Pink Floyd, our original reverb plates were first installed in 1957 to complement the fixed reverberation times of the studios’ echo chambers.

In each of these original plates, the stereo reverb effect is created by suspending a large sheet of metal with tensioned springs attached to each corner. A transducer injects the metal sheet with audio energy, which is picked up by two contact mics fixed to the surface of the plate. The reverb time can then be adjusted by using an internal damper, and all of this is contained within a large wooden unit.
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Re: Abbey Road Plate Reverbs

Postby blinddrew » Mon May 17, 2021 11:03 am

Those are huge! :shocked:
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Re: Abbey Road Plate Reverbs

Postby Luke W » Mon May 17, 2021 11:14 am

blinddrew wrote:Those are huge! :shocked:

I'm starting to remember seeing some pictures of these a while back. They're bigger than you expect aren't they!
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Re: Abbey Road Plate Reverbs

Postby Hugh Robjohns » Mon May 17, 2021 11:22 am

They are. About four foot high and 8 feet deep!

The early ones used asbestos either as acoustic wadding lining the wooden case or as the damping panel (I'm not sure which)!

When I worked at the BBC's training centre we had an early plate in the cellar of the original 'stately home' at the heart of the Wood Norton estate. But when that was sold off to become a hotel the cellar access wasn't big enough to allow the plate to be removed in one piece, and because of the asbestos we weren't allowed to dismantle it. So it was just abandoned! I've no idea whether it is still down there, or if it was smashed up by the builders and skipped, or what...

But it was fun taking students down to it to hear ghostly reverberant sounds coming from a studio on the other side of the campus! :lol:

The silver lumps on the top of the four Abbey Road units are the motors that move the damping panels to allow the reverb time to be adjusted remotely (the early versions had a big wheel like a ship's control valve at the top for that -- as you can see in the pic above). The panels move closer or farther from the plate itself (but don't ever touch it) tp control the reverb duration.

Image

A small control unit with up/down buttons and a meter is usually built into the mixing console, allowing a control signal to be routed to the reverb plate along with the audio to and from, and that control signal allows the damper to be moved to increase or decrease the reverb time, with the display showing the current setting.

EMT 140 remotes.jpg
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Re: Abbey Road Plate Reverbs

Postby Zukan » Mon May 17, 2021 12:35 pm

Amazing.
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Re: Abbey Road Plate Reverbs

Postby Hugh Robjohns » Mon May 17, 2021 12:44 pm

There's a typically fastidious BBC Technical Instructions note (in BBC parlance means service manual!) on the EMT140 plate here:

http://www.bbceng.info/ti/eqpt/EMT140.pdf
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Re: Abbey Road Plate Reverbs

Postby Zukan » Mon May 17, 2021 12:49 pm

Now 'that's a manual'!
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Re: Abbey Road Plate Reverbs

Postby Zukan » Mon May 17, 2021 12:59 pm

Hugh, are there any companies that still make plate verbs? Google's not helping here...

I get that it would be completely uneconomical and practical to do so but wouldn't it be cool? I mean the hi-fi clans buy 8 grand usb cables so why shouldn't we do crazy shit huh?
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Re: Abbey Road Plate Reverbs

Postby Wonks » Mon May 17, 2021 1:14 pm

There are a few videos on YouTube about making your own plate reverb (though they are probably 1/4 the size of the EMTs). Relatively simple to do, but you need a quiet space to put it in. And it will probably sound no different to a good emulation.
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Re: Abbey Road Plate Reverbs

Postby Luke W » Mon May 17, 2021 1:14 pm

It's yet another thing to add to my list of completely unnecessary things I'd like to build.
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Re: Abbey Road Plate Reverbs

Postby ManFromGlass » Mon May 17, 2021 1:17 pm

I found instructions on how to build your own on the internet.

Our cistern is a concrete box roughly 8 feet square. When it’s almost empty it sounds glorious. But the choice is always cool reverb vs 3 months of water.
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Re: Abbey Road Plate Reverbs

Postby Zukan » Mon May 17, 2021 1:22 pm

Luke W wrote:It's yet another thing to add to my list of completely unnecessary things I'd like to build.

I'm still building my lightsaber. It's trying to incorporate usb-1, you know for warmth, that's holding me back.
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Re: Abbey Road Plate Reverbs

Postby Hugh Robjohns » Mon May 17, 2021 1:26 pm

Back in the day, when the Beeb either made everything itself, or modified everything it bought in, the Technical Instructions manuals were wonderful things. Multiple large red ring binders containing fabulously detailed information on everything in service, with new TI sheets being issued regularly for new gear that could be clipped into the folders.

So if you had a unit that had failed or needed alignment, you simply pulled the appropriate ring-binder from the shelf, thumbed through to the relevant device ID number -- AM 8/16 or DK 4/19 or whatever -- and read the notes. It gave you a thorough overview of the device, its operation, and it's full circuit design, with all the schematics, parts lists and, where appropriate, analysis you'd need to get it working, complete with detailed test point measurements to check proper functioning.

Sadly, from the late 80s onwards, as the Beeb stopped making its own stuff and just bought off-the-shelf commercial gear, the TIs stopped and we had to rely on the manufacturer's own service manuals which were rarely a patch on the Beeb TIs.
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Re: Abbey Road Plate Reverbs

Postby Hugh Robjohns » Mon May 17, 2021 1:30 pm

Zukan wrote:Hugh, are there any companies that still make plate verbs?

Not that I know off, although as others have said there are DIY instructions on the web. And original EMT plates still change hands (from defunct studios, mainly) for big money.
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Re: Abbey Road Plate Reverbs

Postby Zukan » Mon May 17, 2021 1:31 pm

Hugh Robjohns wrote:Back in the day, when the Beeb either made everything itself, or modified everything it bought in, the Technical Instructions manuals were wonderful things. Multiple large red ring binders containing fabulously detailed information on everything in service, with new TI sheets being issued regularly for new gear that could be clipped into the folders.

So if you had a unit that had failed or needed alignment, you simply pulled the appropriate ring-binder from the shelf, thumbed through to the relevant device ID number, and read the notes. It gave you a thorough overview of the device, its operation, and it's circuit design, with all the schematics you'd need complete with detailed test point measurements to check proper functioning.

Sadly, from the late 80s onwards, as the Beeb stopped making its own stuff and just bought off-the shelf commercial gear, the TIs stopped and we had to rely on the manufacturer's own service manuals which were rarely a patch on the Beeb TIs.

Early synth manuals were like that. I remember getting the manual for my Arp 2600 and it had hand written sound design and routing tips in there by the author. I am looking at it right now and it's brilliant!
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