How do vinyl records hold stereo sound? 

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!

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.

I'd be super interested in hearing you cover quadraphonic records.

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

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 never expected Alec to add papercraft to his list of tools to explain with but I am ALL for it!

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.

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!

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!

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!

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!

Your closed captions are just A++! Such a small detail that screams attention-to-detail! Love your content!

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...

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

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!

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’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!

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.

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...

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.

Just found your channel. Absolutely loving this, please keep up the great work! Great explanations, great overall mood, great music - amazing.

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 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. 👍

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! 😃

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.

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)

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.

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.

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.

This all still blows my mind how simple yet complex records are. Also thanks for having the outtakes.

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.

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!

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!

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

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!!

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 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!

I would love to see a microscopic view of the groove to show the difference between mono and stereo records.

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.

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.

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!

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’.

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.

Wondered how this works for years. Never could work out how a single groove could create stereo so glad to finally have an answer !

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.

You can use the MSED plugin for easy stereo separation of audio. Really useful.

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.

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!

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.

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.

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.

I love things like this. It's like some awesome analog technology in a steampunk fantasy world, except it's real.

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.

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!

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 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

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.

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.

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).

I've always wondered how they got stereo sound out of one groove and one needle. Thank you!

The stereo difference track is trippy! The bass guitar is all ghostly cursed, but the brass is really quite similar to the original…

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.

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.

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.

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

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.

As a vinyl enthusiast this cleared some misconceptions I had held for years, and indeed questioned said misconceptions as well

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. 😊

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.

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!

I boggles my mind that someone can invent a form to translate sound into a physical recording and then convert it back into sound just with ingenuity, some paper, a pen and of course a lot of money. I pale in comparison when i find myself unable to use autocad to design something that barely works. Kudos to the people that make things that work.

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…

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.

I love how you describe technology! Thank you 😊

For some reason I am always more in awe of materiel methods of creating magic than electronic ones. The groove in a record has always struck me as remarkable, not only in that it works at all but how exactly it achieves it. Too few people are aware that it is a 90 degree difference in the two channels, and that the groove isn't shaped left and right for the two channels. I admit I thought it was that for the first 64 of my 65 years on the planet.

This is very apparent on vinyl in some Led Zeppelin songs like Whole Lotta Love and very much synonymous with Pink Floyd's sound engineering. Pro tip: if you need to clean your vinyl, use wood glue 😉

Stereo recordings are a fascinating aspect of older tech. Where it also gets interesting is in how else multiple sound channels have been tried over the years. From the quad-channel records with actual encoding methods to the "binaural" records from the earlier years by making a record with either two spirals running beside each other or two completely separate mono tracks played together to get the stereo effect. But the 90-degree single track setup was certainly the most cost-effective for the average consumer who just wanted to listen to nice music.

BTW, did you ever do a video for 4-channel vinyl records or perhaps how the Hafler circuit audio output is achieved?

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 :)

Next it would be nice to describe how the four channels were combined on a phonograph record during the quadraphonic days of the 1970's.

There's a lot of interesting physical considerations for vinyl mixing/mastering. The bass frequencies have to be center-panned as the low frequencies create such big grooves that they can cause the needle to jump out if they're side-panned. Records undergo RIAA equalization where they're mastered with attenuated low-end freqs so the grooves can be physically smaller and denser on the record, and the attenuation is reversed on playback.

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 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.

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.

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.

Applied Science (the channel) has a superb electron microscope clip/animation of stereo records and the needle moving along them, very relevent and shows exactly what is described.

I was surprised that the stereo effect bit worked. Not because you could pull it off; I just didn't think the speaker on a laptop would be that advanced.

Your videos are so rad! My boyfriend and I have been binge watching them all week. Your humor is delightful 😂❤

Early experiments tried also to use the right channel vertically and the left horizontally, but the idea with 45° is genius. The stereo plays also mono records, the bass is mono, but this is ok, we can't locate the low frequencies, the wave lengths are too long, we locate a bass instrument by the harmonics.

Continues to be one of my favourite channels to watch with subtitles! Love it.

The lateral movement can be described as the sum of the 2 channels and the vertical movement, their difference. If you had a cutter that cut vertical difference information (L-R) and lateral sum information (L+R) you would come out with a perfectly compatible stereo disc. Fairchild in fact made such a stereo cutting system in the mid 1960s. It also can be compared with “M/S” microphone techniques for stereo.

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.

That was pretty interesting, but now it calls for a follow-up. How was quadrophonic sound created and reproduced from albums? That sounds like an even more complicated venture.

I inherited from my grandma some Pathé records that used vertical engraving. They rotated at 90 rotations per minute and the track started close to the label and worked its way out to the edge. For the fun of it, I copied them to tape using the following setup: I set the speed to 45 Rpm and the tape recorder to half speed. Then I changed the polarity of one of the stereo channels on the pickup and set the recording to mono. This had the effect of recording the vertical movement instead of the normal horizontal mono movement. I also changed the stylus to a 78 model with wider tip. The sound was not good, but still quite acceptable. Unfortunately, I don't have these records anymore.

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.

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?

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.

I wanna hear how Quadrophonic records were made now