WEBVTT - The History of Loudspeakers 0:00:04.160 --> 0:00:07.160 Get in text with technology with tech Stuff from how 0:00:07.240 --> 0:00:13.640 stuff Works dot com. Hey there, and welcome to tech Stuff. 0:00:13.640 --> 0:00:16.880 I'm your host, Jonathan Strickland. I'm an executive producer at 0:00:16.880 --> 0:00:19.520 how Stuff Works and all of all Things Tech, and 0:00:19.600 --> 0:00:22.799 today we're going to talk about a subject that was 0:00:23.239 --> 0:00:26.040 another listener request, and I actually talked about this briefly 0:00:26.160 --> 0:00:29.920 in the Listener grab Bag episode. Listener MICHAELA had asked 0:00:29.920 --> 0:00:32.920 me to talk about speakers and headphones, how they work 0:00:32.960 --> 0:00:35.800 and where they came from. And today we're gonna cover speakers. 0:00:36.040 --> 0:00:38.920 I was gonna cover both in one episode. That turns 0:00:38.920 --> 0:00:41.479 out there's just too much to talk about if I 0:00:41.520 --> 0:00:44.760 really want to explain where these things came from and 0:00:44.800 --> 0:00:47.800 how they evolved over time. They are very closely related, 0:00:48.159 --> 0:00:50.480 but I feel like I'm gonna have to save headphones 0:00:50.600 --> 0:00:54.800 for a future episode. Uh So, this ties in really 0:00:54.840 --> 0:00:57.120 closely with some of the other recent episodes I've done 0:00:57.160 --> 0:01:01.240 about tech and music, like Middy and turntables. In fact, 0:01:01.640 --> 0:01:05.600 the turntables and record player stuff. The speaker development goes 0:01:05.920 --> 0:01:08.479 hand in hand with that because it was all part 0:01:08.680 --> 0:01:11.600 of the development of the recording industry as a whole. Well, 0:01:11.640 --> 0:01:15.319 a quick reminder we're talking about sound, and I promise 0:01:15.360 --> 0:01:19.040 i'll make this brief. Sound travels through a medium. It 0:01:19.120 --> 0:01:21.640 can be any sort of medium. Really can be solid, 0:01:21.720 --> 0:01:24.920 it can be liquid, it could be gas. Sound is vibration, 0:01:25.080 --> 0:01:29.000 So molecules or atoms within this medium are going to 0:01:29.160 --> 0:01:32.760 bounce against each other and propagate sound throughout that medium, 0:01:32.800 --> 0:01:35.280 So you have to have molecules there. This, by the way, 0:01:35.560 --> 0:01:38.600 is why sound does not travel in outer space, because 0:01:38.600 --> 0:01:42.479 while outer space is not totally empty, there are particles 0:01:42.480 --> 0:01:44.960 in outer space, they're so far apart from each other 0:01:45.480 --> 0:01:49.000 that you can't have them bump against each other and 0:01:49.040 --> 0:01:54.280 propagate sound. So that's why there's no sound in space anyway. Uh, 0:01:54.600 --> 0:01:59.120 we experience sound when vibrating air molecules change the air 0:01:59.160 --> 0:02:01.600 pressure in our air canals. At least this is the 0:02:01.640 --> 0:02:06.040 primary way we experienced sound. And when that happens, the 0:02:06.120 --> 0:02:09.480 air pressure means that it either presses against our ear 0:02:09.560 --> 0:02:14.000 drums also known as the tympanic membrane, or the pressure 0:02:14.120 --> 0:02:18.400 is reduced so that our tympanic membrane presses out because 0:02:18.440 --> 0:02:21.320 there's there's not as much pressure as there normally would be. 0:02:21.600 --> 0:02:25.240 As these vibrations that then gets sent through a series 0:02:25.280 --> 0:02:31.440 of tiny bones that then send vibrations to a structure 0:02:31.480 --> 0:02:35.040 called the cochlea in our inner ears that wiggles around 0:02:35.040 --> 0:02:38.960 some fluid which then wiggles around some special nerve cells 0:02:39.000 --> 0:02:41.919 which send electrical impulses to our brain that we then 0:02:41.960 --> 0:02:44.040 interpret as sound. And I know I've said that a 0:02:44.080 --> 0:02:47.639 couple of times in recent episodes, but it always bears repeating, 0:02:47.680 --> 0:02:52.120 because we have to remember, ultimately, sound is this physical phenomenon. 0:02:52.720 --> 0:02:56.160 It's not just some magic stuff that floats through the air. 0:02:56.240 --> 0:03:00.560 It's actual physical vibrations, and it's in warn't to know 0:03:00.639 --> 0:03:03.560 that because as we got a greater understanding of the 0:03:03.639 --> 0:03:07.079 nature of sound, we were also building on our understanding 0:03:07.200 --> 0:03:11.960 of physics, of electrical engineering, of lots of stuff that 0:03:12.080 --> 0:03:16.600 all together made it possible for us to make speakers. Now, 0:03:16.639 --> 0:03:22.760 before electric loud speakers, we mainly relied on just acoustics, 0:03:23.240 --> 0:03:26.960 the physics of sound, and for a while we didn't 0:03:27.000 --> 0:03:32.800 necessarily have very detailed mathematics to describe the acoustics of sound, 0:03:32.800 --> 0:03:36.640 which by the way, are incredibly complicated. I could do 0:03:36.760 --> 0:03:39.520 a series of episodes about the acoustics of sound, and 0:03:39.520 --> 0:03:42.280 it would take a really long time to do so. 0:03:42.320 --> 0:03:44.880 I'm only going to touch upon acoustics in this, but 0:03:44.920 --> 0:03:48.480 acoustics involve everything from the design of say a room, 0:03:48.480 --> 0:03:50.320 like have you ever been in a room that was 0:03:50.640 --> 0:03:55.240 designed acoustically for the performance of music? You've probably experienced 0:03:55.280 --> 0:04:00.000 some really nice performances that way. But there's also acoustic 0:04:00.200 --> 0:04:05.760 design in things like instruments, including horns, and horns would 0:04:05.840 --> 0:04:08.600 largely represent the way we would try to amplify sound 0:04:08.680 --> 0:04:12.960 before the electric loudspeaker like the megaphone is a classic example. 0:04:13.280 --> 0:04:18.360 So how can a simple shape make a sound louder? Well? Again, 0:04:18.400 --> 0:04:20.520 to dive into all the details would be an episode 0:04:20.520 --> 0:04:24.320 by itself. Plus I would kind of need visual aids 0:04:24.360 --> 0:04:27.680 to really explain it properly because doing this all just 0:04:27.760 --> 0:04:30.839 an audio format is very challenging. But in general, when 0:04:30.839 --> 0:04:33.800 you have a horn or a tapered tube where it 0:04:33.880 --> 0:04:36.120 tapers down to a narrow end and then you've got 0:04:36.200 --> 0:04:38.359 a wide end on the other side, you can send 0:04:38.400 --> 0:04:42.480 sound waves down the length of this tube as plane 0:04:42.720 --> 0:04:45.919 waves p L A n E. Those are waves that 0:04:45.960 --> 0:04:49.200 travel in parallel with one another. So you have one 0:04:49.279 --> 0:04:52.560 wave behind that, you have another wave in parallel behind that, 0:04:52.640 --> 0:04:54.960 you have another wave in parallel and so on. It's 0:04:55.000 --> 0:04:57.479 kind of like a stack of waves. Now, the tube 0:04:57.480 --> 0:05:00.200 needs to be narrow at one end to fit the 0:05:00.240 --> 0:05:03.800 source of the sound, such as your mouth or with 0:05:03.960 --> 0:05:07.640 acoustic speakers. Back in the old days when you had 0:05:07.680 --> 0:05:10.960 the gramophones, you know those big trumpet looking things that 0:05:11.040 --> 0:05:13.279 stuck out of what looked like a record player. Well 0:05:13.520 --> 0:05:17.279 that had to be right around whatever the membrane was 0:05:17.520 --> 0:05:20.920 or the speaker driver in order to help amplify sound. 0:05:21.160 --> 0:05:23.359 The tube then has to flare out because if it 0:05:23.400 --> 0:05:26.440 remains narrow, sound waves would start to reflect off the 0:05:26.520 --> 0:05:30.279 sides and that would that would start to affect the 0:05:30.480 --> 0:05:33.760 loudness as it went down the path. And that's largely 0:05:33.760 --> 0:05:37.360 because of wave size. Lower frequency sound waves have longer 0:05:37.400 --> 0:05:39.839 wave forms, so you need to flare out the horn 0:05:39.880 --> 0:05:42.680 to allow for those longer frequencies. And this is why 0:05:42.720 --> 0:05:45.360 instruments like the tube but have such a large flared 0:05:45.440 --> 0:05:49.080 horn at the end because they're playing those lower frequency sounds, 0:05:49.080 --> 0:05:51.800 whereas something like a trumpet can have a smaller flare 0:05:51.839 --> 0:05:54.360 because they are not playing notes that are at that 0:05:54.480 --> 0:05:58.520 low of a frequency. The design of a horn transforms 0:05:58.640 --> 0:06:02.520 sound waves by taking the high pressure, low velocity waves 0:06:02.560 --> 0:06:05.880 emitted into the narrow end also known as the throat 0:06:06.040 --> 0:06:09.640 of a horn, and then converts those into low pressure, 0:06:09.839 --> 0:06:14.279 high velocity vibrations at the wide end, so high pressure 0:06:14.320 --> 0:06:17.640 low velocity to low pressure high velocity, and the high 0:06:17.720 --> 0:06:21.600 velocity vibrations can move through the air more efficiently. In addition, 0:06:21.800 --> 0:06:25.440 a horn restricts the spreading out of sound waves. It's directional. 0:06:25.800 --> 0:06:29.520 Sound will emanate out in all directions from a source normally, 0:06:29.839 --> 0:06:31.960 but with a horn you can restrict that a bit. 0:06:32.120 --> 0:06:34.640 You direct the sound a little bit toward an intended 0:06:34.680 --> 0:06:38.560 target and thus deliver a more concentrated collection of sound 0:06:38.560 --> 0:06:42.080 waves at that target. But while horn acoustics are pretty 0:06:42.080 --> 0:06:44.919 amazing and fascinating, they are not the ideal solution for 0:06:44.960 --> 0:06:48.120 amplifying sound in all situations, which brings us to the 0:06:48.160 --> 0:06:51.560 invention of the electric loudspeaker. Also, I should mention that 0:06:51.600 --> 0:06:55.080 electric loudspeakers frequently make use of the principles of horn 0:06:55.120 --> 0:06:57.800 acoustics in their design. So just to get that out 0:06:57.839 --> 0:07:00.000 of the way, it's not like horn acoustics no longer 0:07:00.040 --> 0:07:03.840 or apply. It's just we're not relying solely on horn 0:07:03.880 --> 0:07:07.919 acoustics for amplification. At this point. The first electric loudspeaker 0:07:08.680 --> 0:07:13.360 was part of an invention called the telephone. Now we 0:07:13.440 --> 0:07:16.200 all know Alexander Graham Bell gets the credit for inventing 0:07:16.240 --> 0:07:20.160 the telephone, but it was actually another person, a German teacher, 0:07:20.280 --> 0:07:24.880 Johan Philip Rice, who was actually the original inventor of 0:07:24.920 --> 0:07:28.560 a device called the telephone. He called his device a telephone. 0:07:28.880 --> 0:07:31.720 It was different from the telephone that Alexander Graham Bell 0:07:31.800 --> 0:07:35.000 would invent, but it was a device. It was called 0:07:35.040 --> 0:07:37.679 the telephone, and it came out about two decades before 0:07:37.760 --> 0:07:41.440 Alexander Graham Bell got into it. Uh so it's not 0:07:41.640 --> 0:07:46.600 nearly as transformative as Alexander Graham Bell's invention in eighteen 0:07:46.640 --> 0:07:51.280 sixty So okay, more like fifteen years before Graham Bell's breakthrough, 0:07:51.920 --> 0:07:56.320 Rice was hard at work creating an electrically powered device 0:07:56.440 --> 0:07:59.920 meant to mimic the human ear. In fact, his early 0:08:00.120 --> 0:08:03.400 early versions of this look like a human ear carved 0:08:03.400 --> 0:08:06.440 out of oak, and even had these little metal parts 0:08:06.440 --> 0:08:10.200 that were supposed to replicate the way the bones in 0:08:10.240 --> 0:08:14.000 our ear drums work or behind our ear drums work. Well, 0:08:14.040 --> 0:08:17.320 he thought he could transmit sound through electric wires, harnessing 0:08:17.440 --> 0:08:21.640 something called magnet restriction Now, this is a phenomenon in 0:08:21.680 --> 0:08:25.520 which a feral magnetic material like iron will change in 0:08:25.640 --> 0:08:29.760 dimensions due to a change in the magnitude and direction 0:08:29.960 --> 0:08:33.920 of its magnetization. So essentially what this means is if 0:08:33.960 --> 0:08:36.920 you get something that's feral magnetic, like an iron bar, 0:08:37.360 --> 0:08:41.440 and you put it inside a magnetic field, and it's 0:08:41.440 --> 0:08:45.880 a weak magnetic field the h and you put it 0:08:45.880 --> 0:08:48.120 in such a way so that the direction of the rod, 0:08:48.200 --> 0:08:50.319 as in the length of the rod, match the magnetic 0:08:50.360 --> 0:08:53.320 fields direction. The rod would actually get a little bit 0:08:53.400 --> 0:08:56.959 longer through this weak magnetic field. Now, if it were 0:08:56.960 --> 0:09:00.480 a strong magnetic field, the rod would actually contry tracked 0:09:00.520 --> 0:09:02.640 a little bit, would be a little shorter than normal. 0:09:03.040 --> 0:09:05.120 And if you had a very precise way of measuring 0:09:05.160 --> 0:09:07.920 the rod, you could actually see that the length of 0:09:07.920 --> 0:09:10.960 the rod changed as the magnetic field changed. So if 0:09:11.000 --> 0:09:14.640 you change the field strength, you could actually dynamically change 0:09:14.679 --> 0:09:17.559 the length of the rod by a very small amount. 0:09:17.840 --> 0:09:20.880 And moreover, doing this would cause the iron rod to 0:09:21.000 --> 0:09:25.000 create a tick sound. Passing a variable current through a 0:09:25.000 --> 0:09:28.480 coil of wire could cause the rod to tick repeatedly, 0:09:28.920 --> 0:09:33.280 generating a sort of tone, and that became the receiver 0:09:33.880 --> 0:09:38.880 of Rice's invention, it became his speaker. This ticking iron 0:09:38.960 --> 0:09:43.400 bar was essentially a speaker. Rice created a device that 0:09:43.480 --> 0:09:47.120 acted as a transmitter. The ear had a parchment membrane 0:09:47.160 --> 0:09:50.400 inside of it that mimic the tympanic membrane in our ears. 0:09:51.000 --> 0:09:54.280 Against that membrane was a little metal strip, So he 0:09:54.360 --> 0:09:58.119 had essentially glued like a platinum strip to this membrane, 0:09:58.720 --> 0:10:03.040 and resting a against that platinum strip was a second 0:10:03.200 --> 0:10:08.559 strip of platinum which was just barely touching the membrane 0:10:08.640 --> 0:10:13.240 due to gravity. So they were just making gentle contact 0:10:13.320 --> 0:10:14.960 with each other. In fact, we would have called this 0:10:15.360 --> 0:10:18.760 a loose contact if it had been done on purpose 0:10:18.800 --> 0:10:22.040 for an electrical circuit, and when the circuit was powered, 0:10:22.040 --> 0:10:25.880 when electricity was flying going through it, uh, it would 0:10:25.960 --> 0:10:29.640 actually everything's working fine. The two contacts are in in 0:10:29.840 --> 0:10:33.080 connection with one another. Uh, you would be able to 0:10:33.120 --> 0:10:36.960 have pass electricity through without any issues. But Rice believed 0:10:37.000 --> 0:10:40.839 that if you made sounds into this simulacrum of an ear, 0:10:41.440 --> 0:10:44.880 you could make the membrane vibrate, and he believed this 0:10:44.920 --> 0:10:48.760 would cause the metal contacts to bounce against each other 0:10:49.200 --> 0:10:53.200 and cause the current passing through the circuit to become intermittent, 0:10:53.679 --> 0:10:56.079 and this would be what he would call and what 0:10:56.120 --> 0:11:00.240 others would call a make or break transmission. So if 0:11:00.240 --> 0:11:03.680 you think about something like a telegraph, where when you 0:11:03.840 --> 0:11:07.040 press down on the key, it completes a circuit, and 0:11:07.040 --> 0:11:09.800 when you let off of the key, it breaks the circuit. 0:11:10.760 --> 0:11:12.840 He was thinking along those same lines, except he was 0:11:12.840 --> 0:11:14.840 thinking this would be a way for you to transmit 0:11:14.880 --> 0:11:19.960 actual sounds, not just uh, the the signal that there 0:11:20.120 --> 0:11:24.120 is an electric circuit made and broken. That's what he 0:11:24.120 --> 0:11:27.680 thought was behind this whole idea, and so he started 0:11:27.720 --> 0:11:30.920 to experiment with this, and he thought eventually he could 0:11:30.960 --> 0:11:33.360 do he could create a system this way where you 0:11:33.360 --> 0:11:37.480 could transmit sound through electricity. You would put the sound 0:11:37.559 --> 0:11:41.000 into the transmitter, it would do this make or break 0:11:41.200 --> 0:11:44.280 series of connections, and then on the other side you 0:11:44.320 --> 0:11:47.400 would have this iron bar that would start ticking, and 0:11:47.440 --> 0:11:49.800 the ticking would be done in such a way that 0:11:49.840 --> 0:11:51.960 you would be able to make out what was the 0:11:52.000 --> 0:11:57.520 original sound put into the transmitter. Side now in a courtroom, 0:11:57.600 --> 0:12:03.320 because eventually his design would be brought into court proceedings. 0:12:03.360 --> 0:12:06.960 When Alexander Graham Bell came forward with his invention of 0:12:07.000 --> 0:12:10.480 a telephone, well, we'll find out what happened in the courtroom, 0:12:10.640 --> 0:12:14.280 but first let's take a quick break to thank our sponsor. 0:12:21.720 --> 0:12:25.600 Scientists testified that the only way this even worked at 0:12:25.640 --> 0:12:30.600 all was if the sound was not too loud, and 0:12:30.679 --> 0:12:34.679 so the two strips of metal would never lose contact 0:12:34.679 --> 0:12:38.880 with each other. They would press more gently against each other, 0:12:38.880 --> 0:12:41.640 but they would still remain in contact, and that this 0:12:41.720 --> 0:12:45.920 would end up varying the electrical resistance of the circuit, 0:12:46.480 --> 0:12:50.199 which would change make it a variable current flowing through 0:12:50.240 --> 0:12:54.360 the circuit, and that is what made the signal that 0:12:54.960 --> 0:12:56.800 made it possible for you to hear something on the 0:12:56.840 --> 0:12:59.280 other side. So not that there was a make or 0:12:59.440 --> 0:13:03.559 break connection, but rather that the connection that was made 0:13:04.000 --> 0:13:07.160 had a variable resistance and thus a variable current, and 0:13:07.240 --> 0:13:10.480 that is what drove the receiver on the other side. 0:13:10.760 --> 0:13:14.320 The reason this is important as they were saying, yeah, 0:13:14.600 --> 0:13:19.680 technically Rice's inventions sort of works, although it wasn't producing 0:13:19.880 --> 0:13:23.400 clear representations of the original sound. You could tell that 0:13:23.480 --> 0:13:26.200 it was making a sound based upon the original one, 0:13:26.480 --> 0:13:29.360 but it wasn't clear. You couldn't get intelligible speech out 0:13:29.400 --> 0:13:32.360 of it. They said, yes, it is working, but it's 0:13:32.400 --> 0:13:35.080 not working the way he thought it was the way 0:13:35.120 --> 0:13:39.400 he described it. It can't work that way, because that's 0:13:39.440 --> 0:13:41.640 not the way that that's not what we're seeing. What 0:13:41.679 --> 0:13:43.640 we're seeing is the only way it works is that 0:13:43.760 --> 0:13:47.120 the sounds are quiet enough to not break the connection, 0:13:47.360 --> 0:13:51.679 but only change the electrical resistance of the circuit. So 0:13:52.200 --> 0:13:55.520 while his his invention works, it doesn't work the way 0:13:55.520 --> 0:13:58.520 he wanted it to. So his patent is invalid, and 0:13:58.559 --> 0:14:01.839 the courts upheld this. And some people find this really 0:14:01.880 --> 0:14:05.240 interesting that you could have something that technically works, but 0:14:05.320 --> 0:14:07.520 if you describe how it works and you get the 0:14:07.559 --> 0:14:11.320 description wrong, that is what ends up being important, not 0:14:11.360 --> 0:14:14.880 whether or not your invention actually does anything. Uh. And 0:14:14.960 --> 0:14:16.959 that in fact was the case. And Rice got really 0:14:17.040 --> 0:14:18.880 kind of disgusted by all this and kind of got 0:14:18.880 --> 0:14:24.080 out of that area of study. After the Brewjaja over 0:14:24.120 --> 0:14:28.280 Alexander Graham Bell's invention. Speaking of Alexander Graham Bell, we 0:14:28.320 --> 0:14:32.120 should chat about his version of the telephone. He patented 0:14:32.160 --> 0:14:35.640 his first electric loudspeaker as part of his telephone invention 0:14:35.960 --> 0:14:39.359 in eighteen seventy six. Now, later on he did acknowledge 0:14:39.440 --> 0:14:43.480 Rice's work as part of the inspiration for his own invention, 0:14:44.040 --> 0:14:48.160 but Graham Bell avoided the problems Rice encountered. Alexander Graham 0:14:48.160 --> 0:14:51.280 Bell was in a race to patent his invention before 0:14:51.360 --> 0:14:54.880 a rival of his named Elisha Gray could get his 0:14:55.040 --> 0:14:58.880 own implementation patented. So he had Elisha and you had 0:14:58.920 --> 0:15:02.880 Alexander Graham Bell, and they were both working on this furiously, 0:15:03.120 --> 0:15:05.320 and in fact they both filed for patents on the 0:15:05.360 --> 0:15:09.600 exact same day. There are people to this day who 0:15:09.760 --> 0:15:13.200 argue that Elisha Gray should get the credit for inventing 0:15:13.200 --> 0:15:17.200 the telephone rather than Alexander Graham Bell. Now, their inventions 0:15:17.360 --> 0:15:20.800 were similar but distinct. They were not exactly the same thing, 0:15:20.880 --> 0:15:24.120 so it wasn't necessarily that one was copying the other, 0:15:24.200 --> 0:15:27.120 although there have been allegations that perhaps Alexander Graham Bell 0:15:27.440 --> 0:15:31.520 had a look at Elisha Gray's um design and then 0:15:31.680 --> 0:15:35.360 based some changes in his own design on that. Whether 0:15:35.400 --> 0:15:38.040 those allegations holding the merit, I'll leave to other people. 0:15:38.320 --> 0:15:40.360 It gets real ugly if you want to read into this. 0:15:40.880 --> 0:15:44.680 But the two had been in competition for years. They 0:15:44.720 --> 0:15:47.640 had been working against each other in the field of 0:15:47.680 --> 0:15:51.520 telegraphy well before they started getting into the idea of 0:15:51.520 --> 0:15:55.000 a telephone. And I'm not gonna go any further into that, 0:15:55.080 --> 0:15:56.920 just to say, if you want to look up some 0:15:57.160 --> 0:16:01.560 pretty interesting muck raking, look at Alexander Graham Bell and 0:16:01.600 --> 0:16:05.800 Elisha gray Well. Alexander Graham Bell mounted a piece of 0:16:05.920 --> 0:16:10.120 magnetized iron to a membrane, or rather he told his 0:16:10.160 --> 0:16:14.440 assistant Watson to do this, and an electro magnet would 0:16:14.440 --> 0:16:18.800 attract or repel this magnetized iron as it received the 0:16:18.840 --> 0:16:22.880 incoming variable electric current from the transmitter. The membrane was 0:16:22.920 --> 0:16:25.040 able to reproduce sound, but at a low volume, So 0:16:25.080 --> 0:16:30.040 in other words, he would speak into a transmitter. The 0:16:30.120 --> 0:16:33.640 transmitter had a membrane in it that would, through its 0:16:33.680 --> 0:16:38.000 vibrations very an electric current. That electric current would travel 0:16:38.040 --> 0:16:41.440 through a wire to the receiver. And on the receiver 0:16:41.560 --> 0:16:45.480 side you had another membrane on which was a piece 0:16:45.680 --> 0:16:49.960 of uh magnetized iron, and you had an electro magnet 0:16:50.120 --> 0:16:55.200 just below it that would receive this variable electric current 0:16:55.600 --> 0:16:58.680 and thus attract and repel the iron that was on 0:16:58.720 --> 0:17:02.400 this membrane, making the brain vibrate. That's what ended up 0:17:02.480 --> 0:17:07.119 replicating the sound. In eighteen seventy four, another inventor named 0:17:07.240 --> 0:17:11.800 Ernst Siemens, the co founder of the Siemens Company, made 0:17:11.840 --> 0:17:15.240 an important contribution to the development of the modern speaker. 0:17:15.760 --> 0:17:18.920 He received a patent for his description of an electro 0:17:19.040 --> 0:17:24.080 mechanical dynamic transducer which used a coil of wire suspended 0:17:24.119 --> 0:17:27.719 in a frame so that it could move axially and 0:17:27.840 --> 0:17:32.200 only axially. So his patent described a magneto electric apparatus 0:17:32.520 --> 0:17:36.200 for obtaining the mechanical movement of an electrical coil from 0:17:36.200 --> 0:17:39.680 electrical currents transmitted through it, which would become the basis 0:17:39.720 --> 0:17:44.119 for electric loudspeakers decades later. Now, basically the idea is this, 0:17:45.520 --> 0:17:48.840 imagine you have a frame. So you've got a frame. 0:17:48.880 --> 0:17:51.320 Let's say it's a square frame. It's got sort of 0:17:51.440 --> 0:17:54.240 a circular opening in the middle of the square frame. 0:17:54.640 --> 0:17:58.600 Inside this frame, you suspend a coil of conductive wire, 0:17:59.320 --> 0:18:01.639 so it's spend it in such a way where it 0:18:01.680 --> 0:18:04.680 can swing towards the back of the frame or towards 0:18:04.720 --> 0:18:07.200 the front of the frame, but it cannot move up 0:18:07.280 --> 0:18:10.280 or down or side to side with respect to the frame. 0:18:10.400 --> 0:18:12.480 So it's if you're thinking of like the x y 0:18:12.560 --> 0:18:17.399 and Z axis axes. Rather, uh, the Z axis is 0:18:17.440 --> 0:18:19.720 what we're concerned with here, not the X Y. So 0:18:19.760 --> 0:18:22.720 it can move if you're looking dead on in the frame. 0:18:22.720 --> 0:18:24.520 It can move towards you or away from you, but 0:18:24.560 --> 0:18:27.119 not side to side or up or down. When you 0:18:27.160 --> 0:18:31.040 apply a magnetic field, you can induce electricity to flow 0:18:31.119 --> 0:18:34.679 through this conductor. The flow of electricity creates some magnetic field, 0:18:34.960 --> 0:18:37.720 and you can use the attraction and repulsion properties of 0:18:37.760 --> 0:18:41.680 magnets to move the coil back and forth within this frame. Now, 0:18:41.880 --> 0:18:45.560 Siemens did not originally intend for this invention to be 0:18:45.680 --> 0:18:49.119 used for acoustics. He had come up with this idea, 0:18:49.240 --> 0:18:51.639 but he wasn't thinking about loud speakers. He was just 0:18:51.680 --> 0:18:55.960 talking about this basic apparatus. But after Alexander Graham Bell 0:18:56.080 --> 0:18:59.600 patented the telephone in eighteen seventy six, Siemens was motivated 0:18:59.600 --> 0:19:02.440 to apply for a new patent for a non magnetic 0:19:02.520 --> 0:19:06.560 parchment diaphragm as a means of sound radiation on a 0:19:06.640 --> 0:19:10.840 moving coil transducer. He received his patent in eighteen seventy eight. 0:19:11.040 --> 0:19:14.080 And we call the coils on speakers that drive the 0:19:14.119 --> 0:19:18.159 speaker's motions a voice coil. So if you ever hear 0:19:18.160 --> 0:19:21.160 anyone talk about the voice coil of a speaker, that's 0:19:21.200 --> 0:19:25.040 the coil that is part of the speaker system. It's 0:19:25.080 --> 0:19:29.359 it's attached to the diaphragm of the speaker that makes 0:19:29.400 --> 0:19:32.679 the diaphragm actually vibrate. At this point, I need to 0:19:32.680 --> 0:19:38.560 mention there were numerous scientists, tankerers, and engineers amateur inventors 0:19:38.800 --> 0:19:42.120 who made numerous contributions to allowed speaker designs. Now I'm 0:19:42.119 --> 0:19:44.439 going to talk about just a few of them, because 0:19:44.480 --> 0:19:47.440 to cover them all would take a couple of episodes, 0:19:47.480 --> 0:19:50.720 and some of those contributions, while important, were of such 0:19:50.760 --> 0:19:54.679 a specific nature that would become kind of tedious pretty quickly. 0:19:55.200 --> 0:19:57.000 Just know, a lot of folks worked on this stuff. 0:19:57.000 --> 0:20:00.520 In the late eighteen hundreds and early nineteen hundreds, twenty 0:20:00.640 --> 0:20:04.479 years after Siemens received his patent for a voice coil 0:20:04.600 --> 0:20:08.359 speaker mechanism, this would be about eight In other words, 0:20:08.600 --> 0:20:11.439 there was a man named Oliver Lodge who filed for 0:20:11.520 --> 0:20:14.240 a patent in the United Kingdom for a loud speaker 0:20:14.560 --> 0:20:18.360 that included non magnetic spacers that were intended to keep 0:20:18.400 --> 0:20:21.399 the proper air gap between the inner and outer polls 0:20:21.520 --> 0:20:24.880 of a moving coil transducer, which would help prevent issues 0:20:24.920 --> 0:20:28.520 with the transducer getting stuck within the frame. In nineteen 0:20:28.520 --> 0:20:33.199 o one, John Strow suggested a conical paper diaphragm to 0:20:33.280 --> 0:20:36.640 act as the sound radiator, and went further to suggest 0:20:36.680 --> 0:20:39.520 such a design could be used so that the end 0:20:39.640 --> 0:20:42.240 of the cone stopped at the rim of the speaker 0:20:42.320 --> 0:20:45.520 in a flat section covered by a corrugated surface. So 0:20:45.560 --> 0:20:47.679 in other words, it's kind of like what a speaker 0:20:47.720 --> 0:20:50.359 cabinet looks like today. If you take a speaker cabinet 0:20:50.359 --> 0:20:53.560 that being what we commonly referred to as just a speaker, 0:20:53.920 --> 0:20:56.119 and you look at you can see you have a 0:20:56.200 --> 0:20:58.880 mesh covering of some sorts, probably made out of fabric, 0:20:58.920 --> 0:21:01.080 but it could be made of something else, and then 0:21:01.119 --> 0:21:05.160 through it you'll see the circles that represent the cones 0:21:05.600 --> 0:21:08.679 of the speaker drivers. Well, it was John Strow who 0:21:08.760 --> 0:21:11.400 actually said you could design a speaker in this kind 0:21:11.440 --> 0:21:14.280 of fashion, So that was back in nineteen o one. 0:21:15.280 --> 0:21:19.480 In nineteen eleven, Peter L. Jensen and Edwin S. Pridham 0:21:19.840 --> 0:21:24.679 founded the commercial wireless and development company Jensen and Britain 0:21:24.720 --> 0:21:29.280 would actually build a practical moving coil loudspeaker in nineteen fifteen. 0:21:29.400 --> 0:21:32.199 So people have been talking about this for decades, but 0:21:32.280 --> 0:21:35.240 this was the pair that built the first practical one, 0:21:35.320 --> 0:21:38.119 not just a prototype in a lab, but one that 0:21:38.160 --> 0:21:41.080 could actually be used out in the real world. Together, 0:21:41.240 --> 0:21:44.560 they created a public address system that would allow huge 0:21:44.560 --> 0:21:48.320 crowds of people to hear a presentation or music distinctly 0:21:48.480 --> 0:21:53.320 over loud speakers, and they called their system Magnavox. Later 0:21:53.359 --> 0:21:56.080 they would use that as the name of their company. 0:21:56.080 --> 0:21:58.879 They renamed their company Magnavox. And I'll have to do 0:21:58.920 --> 0:22:01.400 an episode on Magnavo Box at some point because it's 0:22:01.400 --> 0:22:03.560 a big company. It's been around for a long time. 0:22:03.600 --> 0:22:06.520 They've done a lot of important things. Jensen and Pridum 0:22:06.720 --> 0:22:10.520 attempted to patent their design with the intent of working 0:22:10.520 --> 0:22:14.120 with record companies and radio manufacturers, but they were denied 0:22:14.160 --> 0:22:17.320 their patents for those applications, which is why they instead 0:22:17.400 --> 0:22:23.920 focused on public address systems. In two engineers for General 0:22:23.960 --> 0:22:29.600 Electric named Chester W. Rice and Edward W. Kellogg applied 0:22:29.600 --> 0:22:33.560 for a patent for a dynamic loudspeaker in n They 0:22:33.560 --> 0:22:36.359 published their work in an article titled Notes on the 0:22:36.359 --> 0:22:39.919 Development of a New type of hornless Loudspeakers, and it 0:22:40.000 --> 0:22:43.960 was all on the Journal of ai E Transactions. Their 0:22:44.040 --> 0:22:47.320 design described what would pretty much be the foundation of 0:22:47.440 --> 0:22:50.760 all electric loudspeakers from that point forward. So in a 0:22:50.760 --> 0:22:54.159 bit i'll describe what it consists of and how it works. 0:22:54.200 --> 0:22:58.240 But first let's take a quick break to thank our sponsor. 0:23:05.640 --> 0:23:09.000 All Right, now, I'm gonna focus on the speakers themselves, 0:23:09.040 --> 0:23:11.680 and after we talk about speakers and how they work, 0:23:11.880 --> 0:23:14.600 we'll talk a bit about amplifiers, as that was a 0:23:14.640 --> 0:23:18.520 piece that was missing from the Rice and Kellogg loudspeaker. 0:23:18.600 --> 0:23:20.240 And yeah, I know that sounds like I'm talking about 0:23:20.320 --> 0:23:23.520 Rice Crispy treats, but no, uh. The the guys who 0:23:23.560 --> 0:23:27.880 got the patent for the Dynamic Electric loudspeaker were Rice 0:23:27.920 --> 0:23:30.879 and Kellogg, and the two mentioned in their article that 0:23:30.920 --> 0:23:33.480 there was a need for more work and amplification in 0:23:33.560 --> 0:23:35.760 order to get the volume levels you want out of 0:23:35.760 --> 0:23:38.159 a speaker. But we're gonna get to that in a 0:23:38.160 --> 0:23:40.919 little bit, so we'll put that aside for now. So 0:23:40.960 --> 0:23:43.480 if you were to take a speaker apart, and you 0:23:43.560 --> 0:23:47.160 have essentially was called a speaker cabinet, you would find 0:23:47.200 --> 0:23:50.600 that inside that speaker cabinet are one or more drivers, 0:23:50.680 --> 0:23:52.800 typically more than one if you're talking about a big 0:23:52.840 --> 0:23:58.000 stereo speaker. Now, a driver consists of a cone shaped frame, 0:23:58.440 --> 0:24:02.040 which is called a basket. The basket contains the other 0:24:02.080 --> 0:24:05.879 components of the loudspeakers, so they're all housed inside this frame. 0:24:06.320 --> 0:24:10.040