CX Noise Reduction

Techmoan's got a decent new video up covering CBS's ill-fated CX noise reduction scheme from the early '80s. Worth a view for those who might be interested, or who've stumbled across CX-encoded vinyl over the years and wondered what that was all about:

 

Yeah, I watched this earlier as I really enjoy his vids. I'd never heard of CX on vinyl but the logo did ring a bell from the laserdisc days. It could have been a winner IF it had just improved playback with CX decoders but the fact that it detracted on non-CX hardware meant it wasn't really "compatible" and was a loser. I'll keep my eye out for the CX logo when I'm crate-digging (so as to avoid buying it!) but I doubt there's too much of it kicking around in the UK for sure...

 

Interesting historical documentary, and I had never heard of CX noise reduction. My sister found at a thrift a DBX encoded record, asked what that was about. I explained a decoder is needed and that the record would sound horrible without it. The early 80's was a time of new technology for vinyl (going back to about 1979) 20 bit PCM digital masters, DMM direct metal mastering, half-speed mastering, direct to disc (bypasses rec to tape) Teldec vinyl (earlier actually) Aural exciters in the mastering process, even a laser turntable under development. Most popular was half speed mastering, and then perhaps DMM. How they did try...

The CD arrived on the scene all too quickly.

At about 1981, I purchased a few half speed mastered albums. The upper register sounded splendid, but otherwise I found less than thrilling. One record in particular, "The Stranger", Billy Joel, was pitched up, which I tried to overlook, but just could not. I hate it when a song is rushed, notes mashed together without enough rest between. "Just the Way You Are", was most of my reason for owning this album. It sounded awful. The sax lost its soul, sounded tinny and rushed, the snare attack sounded more like a "click" .. less than a stick on skin.

Half speed mastering requires special eq which adjusts RIAA curve to half the frequency and special play eq for the source playback deck. I have not mastered a record, so it's my guess the possibility for error increases as each eq must be tightly controlled, any errors become cumulative and magnified. Speed errors will also be magnified by a factor of two. (ie: +1% pitch error at half speed translates to +2% pitch error at normal speed) I would even conjecture the tape heads alter the spectral balance at half speed, as the efficiency of the gap improves at half the frequency.. therefore a generous boost of higher frequencies during the mastering process. Anyone experienced in mastering records, would this be correct?

I am not a fan of half speed master records.
Maybe I was unlucky? Do really great sounding half speed records exist?

 

I love Techmoan's videos. They are well researched and presented,, they have a good flow and I always end up learning something new.

 

Shouldn't this be in it's own thread? CX has nothing to do with half-speed mastering.

 

Good point and a good topic, half speed relates to CX as it is one of the many attempts to improve vinyl, some more successful than others.

You're right, I got "carried away" into half speed, perhaps too far off topic. Mention of other competitive technologies certainly shouldn't be off-topic IMO.

 

The Billy Joel album you reference would have been a CBS/Columbia reissue. I'd agree with you that those generally aren't that great.

I am quite fond of the first generation MoFi releases- the ones pressed in Japan with translucent JVC Super Vinyl and mastered by Stan Ricker. Others don't like those though. Like anything else, its personal preference.

 

It refreshing that his videos aren’t based around a view of “this is great/sucks and here’s why.” It’s straight up conclusion based on fair testing of the technology in question.

 

Ironic that CX encoding involved boosting quite passages and leaving the loud ones untouched. Kinda like how records made today sound.

 

I think my favorite Techmoan review is the one testing kitchen gadgets to peel, slice and cook potatoes to make chips. I lose it every time that foam shoots out from the peeler.

 

The video he did of the egg cooker was pretty good, too...

I was gonna say - all of those engineers who got their knickers in a twist over CX? If any of them were still working in the early 2000's, they were doing far, far worse to the albums they were mastering as a matter of course.

 

Has anybody here actually owned any CX-encoded albums and a decoder?

It's also curious that CBS didn't encode cassettes with CX. Wouldn't it have been cheaper than Dolby to implement, and presumably more effective.

I also remember Dolby FM, which never really took off. MTS Stereo, which the US at least adopted for stereo TV broadcasts, incorporated dbx if memory served. There's a thread about Dolby FM here: Dolby FM CX would also probably make more sense for FM than Dolby, since it boosts quiet passages, which non-critical listeners wouldn't notice but which - for those with CX decoders - would result in a much quieter signal.

Was there ever an attempt to encode LPs with Dolby? I'd imagine Dolby B wouldn't do much, since it mostly worked on high frequency hiss, although the encoded LPs, while bright, would still be playable without a decoder. The reduction in noise would be pretty minimal though, and for LPs at least the biggest problem wasn't hiss but clicks, pops and broad-spectrum surface noise. Something like Dolby S might work better, but that was long after the LP's reign was through.