How do vinyl records hold stereo sound?
čas přidán 23. 03. 2023
We answer that question!
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A CLARIFICATION: My script is missing two important words in describing the stereo groove: "behaves like." When discussing stereo-difference signals, I declared that that's what's on the record - which is arguably true but only when you consider lateral and vertical stylus movements in isolation. The raw L&R channels are still encoded as purely diagonal groove movement, but the phase difference in the the cutting head's actuators ensures that those movements, when combined and equal to one another, only result in lateral motion. The cartridge also has its pickups wired with the same phase arrangement to ensure the L&R channels are in phase with one another when playing a mono record (or the virtual center of a stereo record). Is that a mono signal in the lateral motion with stereo-difference information in vertical motion? Well... you decide!
Nice info, Alec! I'm Indonesian. We might have different taste regarding things. For instance, your video about electric kettle is certainly off-limit, not because of such thing doesn't exist because we have it too. But because 1300w kettle, let alone 3500w Europeans use, is way overpowered. We, like Italians, only have strict limit on electricity. Most of us only have 1.3kw. Yes, 1.3! Others have 2.2-4.5kw. Not bad, but not great either. There are also lots of people using 450 and 900w! If you try to use even the lowest end kettle with both types of electricity, you'll trip the breaker (singular, because most of us only have one) quickly. If you have middle class electricity (which is most likely the viewer of your video), you'll hit the limit quickly, and yes, 1.3kw kettle (assuming you have adapter for it) will instantly trip. Even on 2.2-3.5kw, 3.5kw kettle will trip that range of electricity. You have to be at least 4.5kw to be safe, which coincidentally the government persuade to make the transition to EV successful. For your video about can opener, nope, we don't use that. Instead, we have a thing called coconut grater. And heck, you can buy a f ing coconut grater machine if you want. And yes, it comes with electric variant. For the video about passive house, unfortunately, it doesn't gain traction here, even in SEA generally. We simply have surplus of electricity and we don't do time rate. So, noon power is the same as night power. The heat pump and related parts (water heater etc), and house insulation tho, we have it. For the EV, we do have the exact same Ioniq 5 model as yours, just with 250v. So, we're able to pull 3500w in a single cable. Overkill for most households tho. Same goes to electric stove. Tho again, 3.5kw per stove is simply insane to us. Most of us, if any at all, only have single 1 kW stove, mostly nonembedded (tho embedded/range variant do exist, but we have at max 3 stoves). Rest of us that don't have electric stove obviously use gas, which is the majority of stove even today.
Thanks. I was wondering about the phases since they didn't look right to me in your paper mode.
FYI - Your Closed Captions are one of my favorite parts of your videos!
Note, the same idea was kinda used for video too. Instead of using RGB for transmitting color video, we used YPbPr to transmit the black and white backwards compatible Luma and the difference Chroma channels for blue and red.
Thank you. I thought, either I have a huge hole in my decades-long audiophile knowledge, or . . . Great presentation regardless, as usual.
When you started discussing stereo difference channels using Audacity, it was very satisfying. I have a fun story about a radio station that did this by accident, causing me to make a curious detour on a job. Back in 06, I was at university, and also working for the university's media department. They wanted to play the campus radio station over the ceiling speakers in the lobby of the student union, so we put a receiver in a closet and connected the signal. Only -- the ceiling speakers weren't in any kind of stereo configuration; the whole array was driven off the same mono signal, so we had to pass the radio station through a little downmixer. At first I didn't have the part with me, so I just shoved one channel through the speakers to test them, and then I went and got the downmixer to install. When I did that, I found the audio almost totally went away. I checked the wiring and I hadn't messed up; everything was connected the right way. The level indicator wasn't zero, though, so I went from the closet into the lobby with the volume turned up and it sounded like I was underwater. The signal was there, but coming out mud. I tried a different source signal, and it came out fine (after I almost blew out the speakers from nearly forgetting to reset the volume levels). That's when I had the thought, "oh crap, the radio station, they're broadcasting their stereo channels 180 degrees out of phase." One of my roommates had a radio show and worked as a technician at the station so I told him about it. To prove what I was saying, I captured a segment of the station's live Internet stream, which I knew from my roommate was driven off the same mixer as the FM broadcast, and the software I used to capture it was Audacity. All I had to do was combine the left and right channels -- without having to invert one -- and play it back. "I think you've got something wired backwards," I said. We went into the station the next morning and fixed it. They were using analog audio equipment, not digital mixers, and at some point the polarity of one channel had been reversed in the feed. That is the first time in my life I got to fix something by reversing the polarity, and it did satisfy a good chunk of the childhood engineering dreams I had since watching ST:TNG at age 3.
when one of the channel is inverted (which could also happen when speakers are connected in reverse) the center is removed, so i thought i found a karaoke mode (doesn't work for all songs)
Doctor Who would be proud
And you didn't even have to route it through the main deflector dish. 😜
Something like that happened to me once. i replaced the cartridge on my turntable and and mistakenly reversed the wires to one of the channels. Took out the center channel until I figured it out.
I plugged in the headphones into the headphone jack, enough that sound will be loud and clear, but not all the way. I could be wrong, but when I did that, I think I may have been listening to the stereo difference channel.
I'd be super interested in hearing you cover quadraphonic records.
I did see a video about quad. Not sure who, You can do a search.
Yes
Upvoted!
seconding
came here to say this^^^
i've worked at a record store for 8 years now and the technology behind vinyl still blows my mind thank you for doing this
digital wins!
@Dehv Blak Analog is more fun.
Vinyl record trivia: Monty Python (back in the day) cut an album that had two sides on one side: Each 'side' was cut in one spiral grove right next to another spiral grove. Depending on how you set the needle down, you'd get one track or the other. They had no mention of this on the album notes, just left it for you to figure out. Of course, each track was half the length of a regular album side. Crazy!
I think it was the same album, certainly it was Monty Python, where they recorded into the end loop of the record, at the end of a sketch where a protection racketeer scratches the record. The last few words of the side are "sorry squire, I scratched the record, scratched the record, scratched the record, ... " which repeated ad infinitum until you got bored. The end loop was larger than usual so that the record deck did not realise the record had ended.
…which would have been another approach to stereo. Emory Cooke tried an outer and inner track for stereo with a forked tonearm with 2 mono pickups. It didn’t work that well and neither that nor concentric spirals like the Monty Python record (nor true vertical / lateral stereo) would have been backward and forward compatible.
Techmoan did a video about a "horse race" record; it had four different grooves on the one side, each groove containing a different commentary of a horse race with a different winner.
Gro🇴ve.
I remember Tower Records selling a not-as-expensive-as-you'd-think box of CDs of the complete Wagner's Ring of the Nibelung. It came shrinkwrapped with a simple control box with a knob to fade the output from the CD player completely left or right (placed between the CD player and the amp I presume). Instead of the 10 CDs the 15-hour epic opera cycle would normally take up, it only used a paltry 5 discs 😀
Loving the inverted credit music haha! Phase cancellation is essentially what we’re listening to. The difference between the sounds that isn’t cancelled. Love the video!
this difference in channels is what hafler used to produce a pseudo quadrophonic sound simply wiring a speaker or two across the positive terminals of the amp output. i have been using this for decades to add depth to the stereo image.
This technique is still a thing in digital recordings. In a "joint stereo" MP3 encoding, the sound is encoded as a mono channel and a stereo difference channel. The reason is that it compresses more efficiently and results in smaller files for the same quality.
The most common terms for that are "mid" and "side" channels (and the transform called a "mid-side transform")
not the same quality, that's the point: you sacrifice stereo separation to more detailed "mono" components -- only problem is, the stereo difference is not nearly as musical as the mono part, but the encoding does not use significantly different method to encode it, so you will lose a LOT of stereo details (also, some encoders insist using heavy low-passing, at least below certain bitrate mangling the sound even more)
Can you still record two completely different mono track on each R an L channel. Say one song on the left and another in the right and hear them completely separated, like if you isolate and only listen to the L chanel?
This is how FM radio broadcasts in stereo as well. The baseband signal in order is L+R, pilot tone, L-R, RDS encoding, then supplemental services.
huh i didn't know that's what joint stereo is. i thought joint stereo turns mono signal into a fully mono sound while still retaining the remaining stereo channels.
I never expected Alec to add papercraft to his list of tools to explain with but I am ALL for it!
Fun fact about the mono and “stereo difference” signals (better known as mid and side): There is a drum micing technique built around this principle! If you take a cardioid mic, and put a bi-directional mic right next to it, but pointed perpendicular from the sound source, you can get stereo drums that collapse perfectly to mono. Simply add the two signals together in one channel, then subtract the bi-directional signal from the cardioid in the other, and you have stereo drums!
You can generalise the technique. Split the cardioid into an omnidirectional and a bidirectional pointed forward and add another bidirectional microphone pointing up. Your resulting set of four signals can represent a full sphere of sound. It's known as first-order Ambisonics. CS-tv uses it for the audio component of 360-degree video.
There’s nothing inherent to drums about this. I use mid-side to record piano, and even orchestra. I like it because you can adjust the stereo sound in post.
Very common for video and broadcast from the beginning of stereo t.v. to maintain compatibility with mono tellys. Still used in many budget video mics, but the mix matrix is on the mic so you get L&R out rather than M&S. Some are switchable while others are not.
@Alister Carmichael Still something of a standard for TV and radio broadcasts of orchestral performances. Often with a very very nice Schoeps M/S rig.
Don't get us started on the ORTF stereo technique…
What a great video, Alec! As a mastering engineer and former lacquer cutter, I think you did a fantastic job explaining the process. The construction paper model was a perfect visual aid! Bravo!
Your closed captions are just A++! Such a small detail that screams attention-to-detail! Love your content!
I was actually listening to a record when I realized this is how it worked! The snares on Todd Rundgren’s A Wizard A True Star are intentionally put out of phase, but panned hard left and right. Listening back to the cd, it sounds like normal out of phase, and in mono it disappears. But on the vinyl, it gets a really weird, unique spatial quality to it as the needle fights with that huge Side channel! I love weird Mid-Side tricks like that, and in other music where listening to it in mono will ‘erase’ certain vocal lines
Stereo difference (along with some frequency filtering) is sometimes used to generate Karaoke tracks as the singer is typically placed in the center of the stereo stage while instruments are distributed. There are some Karaoke machine chips with this functionality built-in.
I was surprised that this was not mentioned.
This is indeed true. Anything that is mixed mono will effectively cancel itself out and since most vocals are panned center/ mono they will be "extracted" from the mix when isolating the difference. This is exactly how all "surround" processing works from a stereo source. David Hafler while working for Dynaco came up with a passive analog circuit which could extract the "difference" channel from a stereo signal and then send that signal to dedicated "surround" speakers. Dolby pro-logic is the exact same process just done with digital circuits but functionally identical with the exception that with digital you can alter the timings between channels to compensate for speaker placement and distances.
I remember the sound editor that came with the packaged software included with our sound blaster 16 on our 486 could do that. Though most profession karaoke setups are actually worse than that, often being simple covers done by the production company, often with cut runtime, and sometimes even being performed on cheap synths, like someone's toy Casio keyboard. Lol. I'd imagine this reduces the licensing costs, as opposed to the original studio recording with the vocals filtered out as you suggest. I wish it were the case. Though I have on occasion heard some that seemed to be just that, where you can hear the faint remnants of the vocals if you listened hard enough. And even on a rare occasion, one that sounded like they actually got a hold of the masters and just mixed it without the vocals from the beginning. But sadly, by far, most professional karaoke discs seem to be the crappy covers by their in-house musicians.
@Nael Blogger Probably wasn’t mentioned in the Wikipedia article.
A crude version of this can be acheived by connecting the speakers incorrectly. I'm sure there is an audio term for this. I don't remember if it involves connecting both positives to one speaker, or both negatives. Discovered this after accidentally wiring up some speakers the wrong way and suddenly revealed a song I liked had a distinct bit of lyric effect audible this way while nearly inaudible on the normal stereo version. It was quite fun.
Thelma Houston and Pressure Cooker was the first direct-to-disc record that was done without breaks. In other words, LIVE. The only break the band and singers got was the 30 seconds or so before the next song was supposed to start. Also, the break they took between sides of the LP. Well worth a listen!
I had direct to disc records. They were considered the best the format had to offer. CD essentially made them obsolete. Doug Sax of Sheffield Labs had a horrible case of sour grapes about this fact.
@Robert Romero Technically, all discs before 1948 were direct to disc, until recording on tape came into the picture.
@Dan Petitpas True, but the associated equipment wasn't as good back then.
Also, check out James Newton Howard and friends ( some of the Toto guys )
As someone who is deaf in their left ear, this has actually made me interested in getting a mono stylus. I listen to almost everything in mono so that I don't miss anything, and it'd sure be convenient to only need one speaker, rather than two - especially if I have a smaller space to work with in the future. I have no idea whether it'd actually work the way you'd describe with modern records, but it'd be interesting to find out.
A mono stylus wouldn’t do what you’re thinking of, I think. A mono switch would, however.
You can pick literally any kind of subject, and talk about it in so much detail… that is the best explanation about stereo records I’ve ever seen in my life!
I've always known mastering for vinyl was a more specific process, but after seeing how stereo sound works in a record player, it now makes sense! Awesome video! (Also big fan of the channel in general, this one was especially interesting to me as a hobbyist music producer)
Fun fact: I often accidently heard only the stereo difference: When the headphone jack is not plugged in all the way, and both channels have contact but not the ground, you hear only the differences between the audio channels. Happened a lot in the good old days with mp3 players
A tip for anyone doing restoration of stereo audio off records. Because dust and crud sits in the bottom of the groove, it proportionally affects the stereo difference signal more than the mono signal. Convert from LR to MS then do your de-clicking etc. on each separately. Be careful not to use anything that might affect the phase relationship between the two signals. Then convert back to LR after processing.
The stylus tip never rides in the bottom of the groove. Styli have the tip rounded off, so only the sides of the stylus are in contact with the groove walls. The very bottom of the groove is typically not in contact with the stylus. One trick you can use with worn records is to use a stylus with different radius than the one that caused the wear, making the stylus ride higher or lower in the groove to find a portion of the groove wall that is unworn. This trick is regularly used by audio engineers transferring rare recordings from old 78s.
"Convert from LR to MS" - could you unpack this a bit? I assume LR = left-right, but I'm having trouble with MS
@sevenbark MS = Middle (mono) and Side (Stereo difference).
I've seen this advice for years, but every time I have tried this in Adobe Audition, it does not produce better results than just declicking normally. Perhaps its declick algorithm is already doing something like that anyway.
@Mike Brown Quite possibly. I've found it useful in Audacity.
My favorite part was the stereo - difference outro. 😁 I love hearing things that you can't normally hear hidden in the stereo - difference channel.
I grew up with LPs during the 80s. By then, fine audio equipment was available at a reasonable price. Speakers with fifteen inch kickers were very popular. Listening to the left and right audio was an experience. Even to this day, stereo is one of the greatest inventions of all time. Very interesting video, I enjoyed it. Thanks!
Mono and Difference channels, or "Mid / Side", are the key to so many things we use every day -- most of the time, because of backward compatibility with older standards, or where we just want mono compatibility. FM Stereo and analog TV audio both work this way (similar to TV's Y / Cr / Cb color encoding.) Some digital audio encoding formats still use this as an alternative to L/R encoding, for various reasons. MPEG, for example, and probably many of the other perceptual encoding schemes, due to compression algorithms having a particular affinity for correlation. I sometimes track stereo audio (like two guitar or vocal tracks) as a mid and side track, then convert them to L/R using polarity inversion. Again, that helps to ensure the result will work if folded down to mono, but it can also sound interesting (sometimes better, sometimes worse) when there are differences in the takes. This two-channel phase relationship is also one of the core principles to how Dolby Pro-Logic Surround works -- the center channel is from the Mid, the rear channel is from Side, and L/R vs. M/S are steered using some fancy analysis of the signal to determine which direction (front/back vs left/right) is more prominent.
I remember experimenting with the album 'Dark side of the Moon' back in 73. With the song 'Money' if you disabled the right or left speaker, you would still faintly hear the right channel on the left side and the left channel on the right side. That song has very distinct stereo sound so it was easy to experiment with. Back then I had no idea how the sound was recorded, just that I could easily manipulate it. This was a very good video with a solid explanation. I enjoyed it very much. 👍
This all still blows my mind how simple yet complex records are. Also thanks for having the outtakes.
BTW, fantastic job on describing the audio in the captions! Many people never seem to get that captions are more than just what words are being said...
Yeah! The words of the script read aloud are usually pretty good image descriptions too
I was literally laughing out loud at them they were so on point and clever.
Thanks for reminding me, I keep forgetting which channels have the good captions or not.
The confusion goes the other way too. I'm always annoyed when caption information finds its way into subtitles.
Oh noes! This is Primitive Technologies all over again. Me watching all the videos one more time not to miss out. 😂
Love this video, thanks! So about 1,000 years ago my brother & I spent the summer with our grandparents & they just had a mono record player. Magical Mystery tour was a new LP & we played that record a LOT. When we got home we were blown away because we now heard the full stereo on my Dad's piece of furniture stereo. So I'm still not sure why that would be as the two tracks were pretty much isolated when played on the Mono record player. I seem to recall something about how some of the FABs recordings were mono then later somehow enhanced for stereo by boffins.
I loved all the attention to audio production detail, and the captions, and the audio technology. This has been one of my favorite videos so far!
It's such a cool concept to fit two different channels in one grove like this. I heard about it a while back but your explanation really helps. I'm always impressed with vinyl and how it's physically storing sound but the concept of stereo sound like this is just crazy to think about! Genius! Great video as always!!
I’ll throw you a curve. Look into quadraphonic vinyl LPs. Played with the infamous “Shibata” stylus! Quite interesting and actually produced exceptional sound. However, not 100% analog of course, but still very advanced for the era in which they were introduced. Great video!
The quad recordings used a 30,000 cycle carrier frequency to modulate the rear channels. The problem was the best quad stylus in the world couldn't keep up with the groove and would wipe out the record in about five plays, leaving only the front two tracks.
@Greg Roberson Yeah, I would play my quad LP when I first got it to make sure there were no defects and the second time I played it I would record it to reel to reel. After that I’d file the LP into my collection. Most of my quad LPs only had two plays on them. I run it through a Kenwood KR9940 receiver. I wish I still had that setup.
I did the same and recorded on a 4 channel Akia. I lost most of my equipment during the '94 Northridge earthquake. I was living about 2 miles from the epicenter and the only room that sustained damage was the theater room.
I feel like you'd be a teriffic Intro to Linear Algebra teacher! You've basically described what a change of basis is in a way that is super accessible and tangible.
Fun stuff. I'm old enough to remember the coolness of the original stereo records. But honestly, what really WOW'ed me was "quadrophonic" records. That could also be an interesting follow-on to this...
The moment he said and showed "stereophonic" I immediately thought of that as well. That would indeed be a very interesting topic.
I would love to know more
Uh, yes please
Not to mention "Ortoperspecta", invented by Tapio Köykkä, a three-channel (Front-Center and L + R Rears) reproduction from a regular stereo signal. Center channel was the sum of L and R, while the rear channels reproduced the differential signal.
There were two different quadraphonic systems. There was SQ, a “matrix” system which didn’t really have four separate channels, and there was JVC’s CD-4, which used subcarriers to encode either the rear channels or front/rear difference signals, not sure which. This gave better channel separation. I remember reading a bunch of Sansui brochures at the time. They took SQ and turned it into “QS”, which some kind of dynamic level-based adjustments of the decoding matrix, to give the effect of better apparent channel separation.
Wondered how this works for years. Never could work out how a single groove could create stereo so glad to finally have an answer !
Just found your channel. Absolutely loving this, please keep up the great work! Great explanations, great overall mood, great music - amazing.
Something that came in my mind recently given the resurgence of vinyl records and the scarcity of printing plants: do a laser engraver have enough resolution and movement to create a record directly on a disc surface?
i LOVE when you come out with a new video. That's because all of your videos are perfection and in reality should be used in universities.
Great video, I always wondered how you get sound or music out of a piece of vinyl. Excellent history and technology behind it all. Thanks! 😃
That concept would also be used in FM radio broadcast. The combined channel is the main band while the difference channel is a side band. When the signal strength is weak the radio will swap to mono to retain quality.
Yup, and for basically the same reason - the technology existed in mono first, so transmitting the stereo as a difference channel in a sideband kept the transmissions compatible with older receivers. Come to think of it, it's the same thing they did with color television, just with a "color difference" channel instead of a stereo channel.
@rjhelms Technically on US analog TV it is "color difference channels". The 3 primary colors are encoded as two signals in the sideband channel. The two signals in the sideband are encoded on the carrier in two different phases. Those colors you see are made with more adding and subtracting than if at first obvious.
@rjhelms Actually, in NTSC TV two 90 degree separated difference signals carried the colour. G-Y and R-Y. Add G-Y to Y to get red, R-Y to Y to get green, then subtract red and green from Y to get blue.
@Doug Browning PAL rotated them so they're equally important and it's that version (YUV) that is used in early digital codecs.
I was taught for FM Stereo, they switch _very fast_ between the left and right channels and TX the stereo pilot signal at a high audio frequency that 90% can;t hear! And also if the pilot signal isn't present, the RX will automatically turn it into mono!
Holy wow, Down To The Moon, what a throwaback! It, and other Vollenweider albums like White Winds, were a huge part of the soundtrack to my childhood. I'm pretty sure my dad wore out those tapes (yes, we had them on cassettes so we could listen to them on road trips - cars didn't have CD players in the 80s, kids). Thanks for the blast from the past!
An awesome video as usual! I loved the paper diagram of how the needle and pickups work together. It really helped me understand the process occurring to generate sound from the lp. Thanks for all the wonderful content you put out! I always look forward to your new videos and haven’t stopped talking to people about dishwasher detergent and brown haha.
An interesting trick on a turntable is to swap the polarity of one of the cartridge channels and mono the amp. Interesting effect where only difference between left and right is heard. On records with lots of separation the main vocals, bass and drums usually disappear as they are normally in centre of image. Often you can hear backing vocals and instruments not heard before. Works well on Beatles.
Great video, as always! Did you know that Ben over at Applied Science has an amazing scanning electron microscope animated gif of a stylus moving in a groove! It really shows the 45 degree stuff you were talking about!
Once you broke out the model everything clicked. Getting to see what the actual effect of the technique was really helped cement how they work at the same time, and how that translates to reading the groove. I remember watching your first video and, while I came away with both tracks being stored at a diagonal to each other, sharing a groove, I couldn't tell you why. I feel coming away from this that I could actually explain why they are at a diagonal and that feels fantastic. The followup about the stereo difference was also really cool and, from a completely different perspective really helped me understand what the record is effectively encoding. "Two different tracks at 45 degree angle to eachother" is hard for me to understand how that translates to a record, but taking that extra step to explain how effectively it leads to a mono track being preserved in the lateral movement with stereo difference in the horizontal it really got it from a technical understanding to an intuitive one. Thanks for another great video!
I love that the demonstration was arts &crafts instead of computer animation!
@MonkeyJedi99 YES!
I would love to see a microscopic view of the groove to show the difference between mono and stereo records.
As a person that I starting a record collection I asked myself this very same question just about a month ago. Thanks for being here to answer it!
One other advantage of this set-up you didn't mention is that the stereo-seperation signal is generally much less intense than the "main" signal, meaning most of the motion of the stylus is still side to side. If there were intense signals in the up and down direction, this would pose a much bigger risk of launching the stylus out of its groove with loud sounds.
I remember some years back there was a fellow who could "read" vinyl records by looking at them and tell what piece of music it was. Granted (and by his own admission), he could only do it with classical music because he didn't know other styles, but impressive nonetheless.
Thanks for revisiting this topic. I appreciate the additional details and hi-tech visual effects. Grew up with phonographs, and still have my working 1908 Columbia Disc Graphophone.
Here I am, retired and in my 70s with a lifetime (well almost) in electronics and it never occurred to me to question how stereo sound works on a vinyl record. Thanks for the ‘training session’.
its known as the 45/45 out of phase system
I had no idea. Before the internet, these were deep dark secrets
I'm absolutely shocked I never knew vinyl stored information on the walls instead of the grooves.
When I was a kid, I watched an episode of Mr Wizard showing how this works and had people at home make a stylus out of a piece of paper and a sowing needle taped to it. One of the many things I learned on that show growing up. He even did a thing using a flashlight on a movie projector to produce sound.
I've always wondered how they got stereo sound out of one groove and one needle. Thank you!
I love you brother I love your content and what you do give me so much information on technology throughout the past and present it's amazing all the stuff that I grew up with and I used to take apart all of this stuff I didn't know really anything about it but I knew how it works and watch your channels helped me clarify a lot of stuff thank you keep up the good work I'm proud of you bro. Technology connections
Congratulations in creating such a clear and concise explanation of stereo LPs. One reason for its continuing popularity is its simplicity. Providing basic care is taken through all stages of recording and playback (e.g. keeping the LP clean and scratch free) excellent reproduction can be achieved with relatively basic equipment. Whereas the digital recording process is very complex involving a lot processing and despite its high spec can sound a little mechanical and sterile in comparison. Thank you for crediting Alan Blumlein, one of the most important engineers of the last century in many fields including RADAR, the invention of Ultra Linear amplifiers, improving undersea telephone cables and many others. Largely unknown probably due to his secret military work and untimely death in 1942 at 38 years old in an air crash whilst testing HS2 RADAR. He had achieved 128 patents.
Wow this is auspiciously timed. I’m literally building my own record lathe right now and studying this technology 🎉 Neat!
I guessed most of it (horizontal axis for average, vertical axis for difference) but I thought they would be picked up as horizontal and vertical and composed later electronically. I would figure since horizontal and vertical axes may have a different dynamic range, the ability to electronically choose the amplification for + and - signals can help balance that. You could effectively do that with diagonal pickups as well (just by changing the angle, instead of being exact 45 degree) but would make manifacturing a bit more complex (and wouldn't allow for adjustment in the future when disk material changes would change the ratio).
As a visual creative professional, I'm used to using the difference blending mode on images but the fact that you can do the same with audio is blowing my mind
I kind of dig the sound of just the stereo difference track; it's an entirely new sound. Also, I bet you could play the stereo difference of a Beatles song and still hear the entire song.
I’ve done that on A Hard Day’s Night. The vocals cancel out so you get just the instruments. The acoustic part (panned left) is actually pretty complicated.
Interestingly, perhaps, Blumlein invented that technique for use in recording a stereo sound-field using two (figure-eight pattern) microphones placed at 90 degree angles to one another, just like the placement of the cutter head drivers and playback coils on the photograph cartridge. Another stereo micing technique, M-S, for "mid-side" uses different microphone types, but the same math, a mono (mid) signal and stereo-difference (side) signal to capture the stereo sound-field. It's really interesting stuff they came up with back then!
Another excellent video! And you're still at nearly 100% on stuff I already knew, but you're so good at telling the story that I watched the whole video anyway.
Nice touch with the stereo difference version of the closing music! 🤓 Back in the dark ages (‘70s) there was a device called the Thompson Vocal Eliminator which employed this very technique. Since the lead vocal was/is usually panned center, shifting the phase of one channel by 90° would cancel out the vocal, leaving only any reverb triggered by said vocal. I never actually operated one of those, so I don’t know if anything was done to allow the low-frequency sounds of kick drum and bass (also usually panned center) to come through unscathed.
In the 70s when you got bored with a record you lifted the tone arm up to find the little colored wires plugged in the cartridge and switched a pair of connections. Then you got a completely different mix, usually minus the vocals and bass
Yes. They had a variable bandpass filter that you could dial in to only modify only the vocal range...in theory. My aunt had one, and in practice it was pretty much crap. But I suppose it got the job done enough.
Thank you for pointing that out, I didn't even notice the closing music sounded different! 😅 Playing it again it's very obvious it's weirdly off 😁
I used this process many times in my teen years when transcribing music in my DAW software and reorchestrating it with midi synths. The center cancellation helped to reveal some sounds that were hard to hear in the normal mix. But, yes, it would usually cancel bass too, so EQ’ing was involved before the cancellation process. I must add that it’s not a phase shift of 90°, it’s a polarity inversion of one channel of the musical content, similar in concept to a 180° phase shift of a sine wave added to the original sine wave - cancellation. Common-mode rejection, used in balanced signals like pro microphone signals to cancel common-mode interference that might leak into a long run. Balanced or differential signaling using this noise-cancelling property is also used in HDMI, Ethernet, and other well-known signals.
@Chris Merklin Yes, I misspoke. Polarity inversion. Thanks. 😎
The fact you added the bloopers was comical, ha. Thank you for the explanation. I had seen HOW records were pressed before, which is fascinating in itself, but I had never considered HOW the stereo signal is achieved.
You can get some really interesting audio effects by engineering in sum-difference stereo instead of left right, or by applying tools designed for one encoding to the other.
This "L+R and L-R" thing also becomes useful in stereo FM broadcasts (transmit L+R as regular mono FM, then L-R as a suppressed subcarrier,) and later in color TV transmissions.
The 'mono' plus 'stereo difference' channel arrangement as you called it is, I believe, called Mid-Side in the audio mastering industry, or at least is somewhat similar to that.
The visual aid you made for the angled needle was super helpful for me. I couldn't quite picture it. You make very good videos.
I once had an informal cassette copy of some instrumental music that somehow got recorded as a stereo-difference signal without realizing it. No idea how. But I always thought the music was supposed to sound like that. It was quite a surprise to finally hear the original stereo recording years later and hear instruments I didn't even know were there. It certainly sounded much better and crisper and explained why my old copy always seemed somewhat flat and lifeless in sound quality.
Very interesting. I must admit though, I really like the imperfect "living" sound of vinyl records. My digital FLAC/ALAC music is cleaner and more accurate, but I like the scratching sounds in my vinyl and the organic feel of it all
Continues to be one of my favourite channels to watch with subtitles! Love it.
Also worth an honorable mention is the Pathe disk system - up/down grooves on shellac, sometimes called "hill and dale" records - patented as a competitor to Berliner sideways grooves. Obvious now why the Berliner system became the standard.
BTW, did you ever do a video for 4-channel vinyl records or perhaps how the Hafler circuit audio output is achieved?
I wanna hear how Quadrophonic records were made now
Yes!!!!! I know what I’m doing for the next however long this video is. Being into tube gear and vinyl and a speaker builder for 20+ years I ~ THINK ~ I understand the way a stylus works, but I’m sure I’m about to learn something new. Love your vids! You are one of the most cogent, easy to follow educators on youtube. Thanks for remembering the audio geeks :)
Great explanation of information storage on vinyl and the extraction of that information by the stylus. Your lava lamp brought back a flood of memories from my high school days in the late 60s. Thanks for the flashback…
There are records that contained 4 channels from 1 groove called quadraphonic. The 2 extra channels are mastered above hearing frequencies that can be de-modulated back to hearing frequencies.
Nice explanation. I particularly liked the paper cut-out simulation. A couple of things. The stereo signal that vibrates through the stylus and cantilever is, as you say, two channels being fed through one solid, and therefore the stereo signal cannot be completely separated. This is measured as Crosstalk, and phono cartridges have a specification that describes the cartridges ability to minimise it. Better designs do better. Of course, crosstalk isn't unique to vinyl records. The other thing - seeing as you used Audacity to describe one aspect, I would have liked you to illustrate RIAA Correction or Equalisation, which is something that is peculiar to the phono stage in an amplifier because the record groove is shrunk to cram in more record/play time. It means the actual output from a record groove is very bass light/treble bright and has to be corrected. [an Audacity simulation could have shown this very well]. No other input/output requires any correction. Perhaps, when the vinyl record virtually takes over the recording industry for a second time, you can add the last bit in another re-visit to the groove. 😊
I once had a vinyl album with two groves on one side, with a different track listing for the two grooves. It was "matching tie and handkerchief" by Monty python.
I love this channel because it makes me want to learn about things that I never thought I could have possibly cared about before the video was posted. Thanks for all the great content!
A relative of mine experimented in the 1950's with early LP stereo that required two separate records and turntables that had to be started simultaneously. He said there was a small dot you placed each needle on then turn it all on.
First off, LOVE the extra descriptions of the stereo jazz in the Closed Captions. Second, it's interesting to contrast this to how stereo sound (and mono playback compatibility) was encoded in old analog television broadcasts. I believe it was a combined full mono track on the left channel, and stereo seperated right on the right channel?
lol funny timing coming across this after picking up a cheap $35 record player off amazon. Love the videos, and your timing is somehow always great. this is like the 3rd or 4th time you've made a video around the time I am thinking about that same thing.
15:15 that sounds like the “poor mans surround sound” setup. I had a 2nd pair of speakers hooked up from the two positive leads from left and right on my stereo when I was a kid and it gave this interesting surround sound effect from the rear speakers. That reminded me of my setup back in the day.
I remember 2 modern types of records, heavier and thicker one in the 50s, then they all turned to slick light vinyl, AND album covers too became slick and lighter 🕳️ , like the Sargent pepper album on your desk. in Montreal, Quebecers simply call modern records, 'des vinyles', still very popular 🥏
The important things about the encoding used to press stereo LPs is that the sideways movement has the highest bandwidth so it makes perfect sense to use that for the average signal between the channels. The same idea is used in digital audio compression, for example MP3 files support "joint stereo" encoding where one of the channels is encoded as delta to the main channel. Because real world stereo music typically has very similar audio on both channels, encoding one channel as difference to the another saves a lot of bandwidth.
I am pretty sure that Polarity thing is what happened to the original pressing of the album Skylarking by XTC. "Decades later, it was discovered that the album's master tapes were engineered with an improper sound polarity.[93] Mastering engineer John Dent, who discovered the flaw in 2010"
I know captioning ( and so much more) was covered in another video, but I must say, I love the captions in these videos! Especially for the added bonus commentary such as "it's the same song. But, like.... haunted." I laughed a little too hard at that
I find it wonderful you explained the stereo imbalance channel as this is a trick used in some higher end car audio to provide a balance to the audio with a “center” speaker that is connected across the left and right speakers to only play the imbalance as a mono that is bilaterally perceived as an amplification of the opposite channel to even the listening experience with such short distances to the drivers. Generally done with a wide band tweeter. Ie the infinity audio in my 2004 dodge ram 1500. With a “9” speaker infinity audio system lol quite ingenious with driver stacking along with the use of 2ohm drivers.
Great video. You might want to mention in a followup that the concept of separating the mono content from stereo separation content is not unique to vinyl. It's actually very common. This technique is known as "joint stereo" or "M/S stereo coding". Instead of recording the two channels (L and R) separately, you record the "mid channel", M, which is the sum of the two channels (L+R) and the "side channel", S, which is the difference of the two channels (L-R). The result can easily be turned back to the individual channels by adding them and subtracting them: (M + S = (L+R)+(L-R) = 2L. M-S = (L+R)-(L-R) = 2R). One common use of this encoding is FM stereo broadcasts. An FM broadcast modulates the M channel on the primary carrier and the S channel on a sub-carrier. If you are too far from the transmitter to get a clean signal, your receiver will pick up the primary carrier but not the sub-carrier, so the result will be a mono signal instead of the stereo signal. Which is why when you're driving and listening to a weak station, you will hear the sound switching between stereo and mono as the signal strength varies. It's also how your receiver can know when to turn the "stereo" light on/off - it depends on whether or not the tuner can lock on to the subcarrier that contains the S channel. Joint stereo is also used in many compressed audio formats, including MP3 and FLAC. This is because moving the common components of the audio to one channel and keeping the differences on a second channel usually gives you better compression ratios when compression is lossless and will produce better quality sound when compression is lossy. Another cool thing you can do with joint stereo signals is that you can boost or cut the relative volume of the difference (separation) channel. If you boost it before converting it back to the discrete L/R channels, you effectively increase the amount of stereo separation (the "wide" effect) and if you cut it, you decrease the amount of separation.
Literally since I was like 15 and getting into audio recording, music production etc this question has been sitting in my brain. Even now 10 years later this question would still nerd snipe everytime I thought about it while playing vinyl. I think I even googled it a few times but just didn't really understand the concepts just from written answers. But THIS video has finally given me a satisfying answer. Thanks mate!
This was great. It's a subject that many don't ever get to fully understand, and you covered it very well. I retired in late 2020, but one of the last products that I worked on as a product developer was a modern direct drive turntable.
The same diagonal system is used in CoreXY 3D printer heads. One motor goes diagonal one way, the other goes diagonal the other way. Running both motors the same way is X movement, running them opposite is Y movement. Interesting to see how far back the idea goes.
woah i was actually thinking how do they get the up down (left chanel) and side to side (right chanel) to blend so nicely ,,, so glad to find out how it actually works! thats great thankyou so much
Here's an interesting question, because the two channels can somewhat influence each other, does this system allow for two distinct sounds to be played on the left and right channels simultaneously? Or does Fourier/sum-of-signals make that possible?
It was done on early stereo demo discs. It’s possible to a great extent. Like all analog, not “perfect”.
Thank you so much for this. I had always envisioned the movement as up and down vs left-right, but at the same time thought that it wouldn’t work… glad to see I’m not stupid.😅
This is a thing I was curious about, but not curious enough to bother to do any research myself. I would have thought maybe one day it'd be mentioned in a Techmoan or VWestlife video, but now Technology Connections has made a video about it so I'm probably going to learn every detail about the subject. Every time I make a piece of toast, I wonder - "this would be so much better if I had a Sunbeam".
Loved this one. The Aquarius and the 5th Dimension record you had on the table is actually the first record I owned, given to me by my mom. Let the Sun Shine In is my jam 🤩
Alec, would you consider doing an exposition on the various quadrophonic formats?
This is really interesting. I make music and when I'm producing some plugins that I use allow me to hear the 'difference' and 'sum' channels and I always knew kinda what they were, but I couldn't really explain what they were. Now I know where those terms come from and it makes so much sense now
Ignore the scam reply.
@Kevin D i will pay full attention to it
You ought to do a video on how the FM stereo works regarding stereo vs mono.
Philips used to have a display in the Evoluon (in Eindhoven) that showed how stereo sound was obtained from a single groove. The display used a giant disk (about 4 feet in diameter) with a suitably sized pickup arm. On the front of the arm a couple of indicators, one for the left channel the other the right channel, waggled according to the groove (which was only a sine wave) in the record. If I remember correctly (it was the mid-1980s!) there were three grooves, one had only the left channel cut, one the right channel and the third had both cut, the indicators showed how each side of the groove affected the stylus and the combined result when both channels were playing. The side wall nearest the centre of a record carries the right channel, the outer side wall carries the left channel, this is why when there is damage to the grove which straddles several rotations a 'pop' is heard first in the right channel, the 'pop' then migrates across the sound stage before exiting 'stage left'.
As a vinyl enthusiast this cleared some misconceptions I had held for years, and indeed questioned said misconceptions as well