How a single vinyl needle makes stereo

[@gotham61]

Oh man, Paul's explanation is just plain wrong here. It's not vertical movement in one channel, and lateral movement in the other channel. The two groove walls are both at 45 degrees from vertical, and one channel moves the stylus diagonally from one groove wall, and the other channel moves the stylus in the opposite diagonal from the opposing groove wall. Because one channel has its polarity reversed compared to the other, a mono signal will result in only left to right movement of the stylus. This is the 45/45 record cutting system developed by Westrex over 65 years ago, and used for all stereo records since then.

[@gotham61]

There's a pretty decent animation showing how it works starting at the 3 minute point in the 1958 RCA promotional film. kzbin.info/www/bejne/oanInaunqdCemsUsi=z5TudIg_0ThG-tWM

[@oliverbeard7912]

Thumbs up to your comment.I'm pretty sure that's also what I read in a "How does it work?" Book.

[@edwinsinclair9853]

@@oliverbeard7912 Exactly, Westrex (really Western Electric) of Bell Labs called it the 45-45 System.

[@michaelbuxton8947]

Paul describes a method that was dropped in the 1960s and hasn't been used since.

[@markmeridian3360]

Sometimes Paul gets it wrong and appropriately gets corrected in the comments. I've yet to see Paul withdraw a video and issue a new video that corrects a misunderstanding or misstatement on his part.

[@ScottAllison-jf4ke]

How bout quad records.

[@adotopp1865]

How bout em dude?

[@michaelturner4457]

Which quad record format, CD-4, QS, or SQ? Of course that was the problem with quad, multiple incompatible formats, i.e. a format war.

[@RichTeer]

Calvin and Hobbes and The Far Side are my favourite cartoons too! There’s another vinyl-related Calvin and Hobbes comic, where Calvin is listening to the 1812 Overture at 78-RPM.

[@NicholasAladdin]

I really like Paul but this a shocking and erroneous explanation from a man who should know better. I won't bother with the real answer 'cos commenters below have made it clear.

[@SpyderTracks]

Vinyl sound reproduction was so incredibly advanced for its time, the complexity of it and the precision engineering required is mind boggling at a time when tolerances were so much larger than they are now. Never ceases to amaze me. The victorian era were so advanced in so many ways. You look at normal street adornments on lampposts and building facades from that time, iron bridges, it’s all things that we couldn’t afford to recreate in this day, even if we still had the skill sets to be able to do so.

[@a.dejager7062]

It is V-shaped. Think of it as one channel in each side of the V.

[@NicholasAladdin]

Quad vinyl records work in several ways. Phase manipulation, frequency modulation and rotational cutting of the groove combined with the regular left/right cut. Designations were EV, CD-4, SQ and QS and other variables. I tried all of them. The best with really good equipment was CD-4.

[@InsideOfMyOwnMind]

The inner and outer groove walls are 90 degrees apart so that the axis of each channel doesn't affect the other. The channels are recorded out of relative phase so that mono LF content doesn't lift the stylus out of the groove by pinching it out. Several methods were tested including mid side with sum on one channel and difference on the other. Relevant information far more detailed is abundant.

[@kevindillinger3699]

I just don't understand the Vinyl thing. There is a reason why we have moved forward.

[@Projacked1]

Wrong.....

[@Think_Up]

3:50 Paul giving the Birds and Bees talk to audiophiles.

[@adotopp1865]

Modern stereophonic technology was invented in the 1930s by BRITISH engineer Alan Blumlein at EMI, who patented stereo records, stereo films, and also surround sound.

[@oliverbeard7912]

Yep.I think it was originally made for film in order to create effects that more closely aligned with the action on screen

[@Shanachie707]

Sorry Paul, but you a wrong. Original, when vinyl was only mono, the signal was engraved vertical, from the left to the right. When stereo arrived, of course they need a second dimension. So the nearest solution would have been a to engrave the second channel signal lateral up and down. But that wouldn’t be compatible to mono cartridges. Because they could only convert a vertical signal, so the user would lose half of the signal. So they rotate it by 45*. So now one channel is cut from the top left to the right bottom and the other from the right top to the left bottom. Only bass ( below 150Hz) is cut from left to right as a mono signal

[@paulmilligan3007]

Is there an alternative universe where left to right is vertical and up and down is lateral? Each attempt to correct Paul’s slip seems to increase rather than decrease confusion.

[@adotopp1865]

Thanks Paul for a simple explanation. Here's my attempt: The stylus moves in a 45° direction on one side of the groove wall for one side of the stereo signal, and 45° on the other wall of the groove for the other Chanel. So each chanel is up down and side to side at once- amazing really.

[@pebbleschan6085]

It’s quite a pointy subject. 😂

[@stevefisher8323]

Thank you for pointing that out, you are groovy sir!

[@Error2username]

IT scratches it out of the record with popps and clikks, old media, we have much better medium now🎉😂

[@adotopp1865]

If you use vinyl records correctly - keep them and the stylus clean you don't get clicks or pops

[@tomday7309]

Well, THAT didn't settle anything, but I moved from vinyl to CD's decades ago and no, I don't want or need an explanation of that technology, thank you. The vinyl revival is being enjoyed by my son who has my vintage Technics turntable with a new cartridge and my old vinyl as well as some new vinyl, so that old technology is still moving along.

[@paulgaerisch]

I want to see Paul explain quadrophonic vinyl recordings! Fun stuff!

[@Think_Up]

When Paul puts the papers down and glasses come off, you know it's about to get real.

[@michaelturner4457]

I thought a "needle" was what was used on the old time phonographs.

[@adotopp1865]

It's also a slang word for stylus

[@leekumiega9268]

Here is a stylus in a record groove under an electron microscope . Note that the left and right side of the groove are different as would be expected for stereo. kzbin.info/www/bejne/faamlaaveLygqpo

[@richardhanmer]

that is INCREDIBLE! And what a brilliant question - it had never occurred to me.

[@3dimensionsofmusic3D]

The Far Side and Calvin & Hobbes were my go-to strips too. I bet you read Mad magazine and National Lampoon too 😊. Satire is the secret sauce in comedy.

[@soulshinobi]

Paul likes Tales from the Far Side? I knew he was a trustworthy man.

[@avsystem3142]

Since when are phonograph needles made out of vinyl?

[@gianlusc]

I always knew that it is a 45 degrees angle situation, with left and right channel on either side of the groove.

[@bobbybradford6064]

I'm always thankful for your videos. Love it

[@PetraKann]

It's the groove on the vinyl pressing that records the stereo signal

[@thinkIndependent2024]

Yep the is well documented in Alan Blumlein original patent . Some American inventors even produced 2 tone arms 2 needle system with double grooves basically the RIAA settled it with a final standard. Thanks Paul.

[@spacemissing]

That was Emory Cook. The two-headed tonearm appeared to use ceramic cartridges. I have two of those records but no way to play them as intended. All of Cook's materials were donated to the Smithsonian and many if not all are available for purchase.

[@gotham61]

@@spacemissing I remember an AES historic exhibit at the New York AES show in about 1990, where Jack Mullin himself demonstrated a Cook Binaural record for me.

[@timessquarerecordscom1469]

Fascinating subject

[@Jigaboo1929]

Hello Paul my girl farted what advice do u have for that 😮

[@domosautomotive1929]

Was it in mono, stereo or 5.1?

[@funny0000000]

Tell her you want to do what Paul is don't at 3:50 and let us know what she says.

[@edd2771]

I went down the rabbit hole rec this on a forum once. I still don’t understand what happens if the recording requires the stylus to be in two different places at the same time.

[@bestuurdvsgroningen3603]

That wouldn't occur. Look at it this way: vinyl playback makes use of all three spatial dimensions. One is the length of the groove, the other the width and the third the height. The length is the time point at which the stylus is in the recoding, the width is the place where it needs to be for the right channel signal and the height is the place for the left channel signal. (For complete accuracy, turn this image 45 degrees as the channels on an LP are vertically oriented.) These three will always add up to a single three dimensional coördinate on the record and the stylus would never have to be at two places simultaneously.

[@edd2771]

@@bestuurdvsgroningen3603I agree but what if the sound coming from either the left or right channel alone was two simultaneous notes of different pitches (a chord or descant).

[@bestuurdvsgroningen3603]

​@@edd2771 Good question, in that case you add the notes up. The movement of the stylus is the sum of all the notes that are played. Your ears do the same thing where they read all the notes with a one dimensional movement for each ear. Where a stylus takes its signal from the record, your eardrums take it from the air.

[@s_r_v]

A disappointing video, why not delete and redo it with a more correct answer??????

[@BobGeogeo]

I'm glad that vinyl playback is thriving for people who love it. Can't say it's for me.

[@bbb-ri4vs]

azimuth

[@SteveWille]

Aren’t the two channels on stereo vinyl NOT Left and Right, but one Left+Right and the other Left-Right from which, with some “math” on these, Left and Right is be recovered? Leaving some room to be wrong here, I think the Left+Right signal is mapped to lateral stylus movement and the Left-Right signal is mapped to vertical movement. The Left and Right signals are recovered but the coils in the cartridge and their geometry.

[@AndyBHome]

I think you're right, but the idea is pretty much still the same. It's still two distinct data streams, two signals being read by a single stylus. If it were not for the fact that they wanted backward compatibility, they might have simply encoded it as L & R on the opposite walls of the groove.

[@SteveWille]

@@AndyBHome Yeah… a stereo record played-back with a mono cartridge produces a mono signal that is the sum of Left and Right.

[@gotham61]

That's not true. A stereo LP has discrete left and right channel signals, and no matrix is needed. Perhaps you are mixing it up with SQ Quadraphonic LPs, which did use a matrix to encode the rear channels.

[@SteveWille]

@@gotham61 I think there are two equivalent ways to look at this. If the frame of reference is horizontal and vertical (left/right and up/down, parallel and perpendicular to the plane of the record), the signals are horizontally Left+Right and vertically Left-Right. If the frame of reference is rotated 45º from that, then the signals are Left for one and Right for the other. A stereo cartridge has this 45º rotated geometry and implicitly interprets Left and Right channels. A mono cartridge has only horizontal geometry and only respondes to left/right movement. As such a mono cartridge behaves reasonably when playing a stereo record and, to a somewhat lesser extent, a stereo cartridge behaves reasonably when playing a mono record.

[@gotham61]

@@SteveWille While it is true that the sum signal L+R results in lateral motion, and the difference signal L-R results in vertical motion, that is not how the records are cut or played. The cutter head is fed a left channel signal and a right channel signal, and these move the cutting stylus directly on the 45 degree diagonal. It's the same with playback, the stylus reads the two diagonal signals directly, and produces left and right channel output signals. One of the beauties of the Westrex system is that it is fully backwards and forwards compatible between stereo and mono. In other words you can play a stereo record on a mono record player, and can play a mono record on a stereo record player, without any losses.

[@siddharthakataki]

As usual Paul is a magician. The two axis movement of the needle is a brilliant explanation demystifying stereo reproduction on a vinyl. Thank you Paul

[@funny0000000]

If the one channel is the up and down movement does gravity make that one sound better or worse than the left and right one or doesn't it mater? Audiophiles can hear stuff that nobody else in the would can hear so wouldn't some of them hear one channel better than the other one?

[@bestuurdvsgroningen3603]

Good question. Paul missed a detail: the left and right channel are V shaped and both at a 45 degree angle in the record, at 90 degrees form each other. Just turn the image a bit until gravity works equally on both channels and you got it.

[@NoEgg4u]

@1:09 "...and the needle goes in and... @2:57 "...the needle is going back and forth..." @3:32 "...this needle..." It is not a needle. It is a stylus. Stereos do not have needles. Needles are for sewing and flu shot. Our host has spread this misinformation on several of his videos. For an educational channel, he should not be doing that. If our host was having a meeting with a dozen high-end audio manufacturer executives and lead engineers from Clearaudio, VPI, AMG, Basis, Air Tight, The Absolute Sound, etc, I bet that our host would not call the stylus a needle. If he did, the others would be laughing under their breath, if not taking an opportunity to rib him over it. Paul, some of them probably watch your videos. It is akin to doctor #1 telling doctor #2 that the patient has a temperature (instead of a fever), and doctor #1 having a youtube channel and doing the same. People come here to learn. Let's not send them away calling a stylus a needle. Let's send them away thinking "I always heard people saying that it was a needle, but I learned that it is a stylus. Good info!" Let's not send them away repeating what children do. When you have a channel with over 200,000 subscribers, take care in not misleading the public. Again, our host has done this over and over in several of his videos. As helpful and lovable as he is, he should not get a pass on knowingly and repeatedly spreading bad information, especially on an educational channel with so many subscribers.

[@nodoughofmine]

learn who wittgenstein is

[@adotopp1865]

The term 'needle' can be used for stylus. It's an acceptable slang term for stylus.

[@michaelturner4457]

Gramophones and phonographs can also have needles, either steel or bamboo.

[@NoEgg4u]

@@adotopp1865 "The term 'needle' can be used for stylus. It's an acceptable slang term for stylus." The term pineapple can be used for stylus, too. The difference is, no one will think that a pineapple is a stylus. Whereas, countless people believe that turntables really use needles -- and that is propagated by videos such as this, and comments such as yours. When those people learn the truth, they will raise their eyebrow and probably think or say something like "Oh, I always thought that it was a needle." For people that care little to nothing about audio gear, it matters little that they think it is a needle. But for people tuning in to learn, it is a problem to lie to them. Instead of our host using his reach and his stature as an expert authority figure as an opportunity to enlighten people who do not know better, our host does worse than squander that opportunity. He actually uses his reach and his influence to misinform his viewers. Not good. It would be like a top chef telling his viewers that a tomato is a vegetable, when it is a fruit. A stylus is not a needle. it is wrong to tell students that it is a needle.

[@nodoughofmine]

​@@NoEgg4uyou ignored my reply