WEBVTT - Rerun: How Speakers and Amplifiers Work 0:00:04.400 --> 0:00:07.800 Welcome to tech Stuff, a production from I Heart Radio. 0:00:12.000 --> 0:00:14.560 Hey there, and welcome to tech Stuff. I'm your host 0:00:14.760 --> 0:00:17.160 job in Strickland. I'm an executive producer with I Heart 0:00:17.239 --> 0:00:21.840 Radio and How the Tech are You? I am working 0:00:22.120 --> 0:00:24.880 right now on a couple of things. When I'm working 0:00:24.920 --> 0:00:28.920 on getting over COVID, I'm almost there, not quite there, 0:00:29.240 --> 0:00:31.760 but I'm getting there. And the other thing I'm working 0:00:31.800 --> 0:00:35.040 on is an episode about a company called San Sui 0:00:35.520 --> 0:00:39.080 that is a or was rather a company that made 0:00:39.600 --> 0:00:43.480 audio equipment like amplifiers and receivers and stuff like that. 0:00:44.400 --> 0:00:46.040 But as I was doing it, I felt like I 0:00:46.080 --> 0:00:50.240 was retreading some ground on a on a previous episode 0:00:50.240 --> 0:00:54.880 called how Speakers and Amplifiers Work? And I thought, why 0:00:54.960 --> 0:01:00.680 not have that episode play out? And then next week's 0:01:00.720 --> 0:01:05.240 Monday's episode will be about San Sui, and I won't 0:01:05.280 --> 0:01:07.600 have to to cover quite as much of the same 0:01:07.720 --> 0:01:09.920 territory again. I can focus more on the company in 0:01:09.959 --> 0:01:13.440 its history because y'all know me. Y'all know that if 0:01:13.480 --> 0:01:16.800 I start talking about a company that makes a certain 0:01:16.880 --> 0:01:19.080 kind of tech or sort of a product that features 0:01:19.080 --> 0:01:22.600 certain tech, I'll end up talking about how the tech 0:01:23.040 --> 0:01:25.240 came about what it does all that kind of stuff, 0:01:25.720 --> 0:01:28.560 but I've already done that. So we're gonna listen to 0:01:28.600 --> 0:01:32.759 this episode how speakers and amplifiers work, and I'll be 0:01:32.800 --> 0:01:37.040 back at the end to kind of tease next week's 0:01:37.200 --> 0:01:41.760 episode on this topic. But sit back and enjoy this 0:01:41.800 --> 0:01:46.720 classic episode. Today we are going to continue our episodes 0:01:46.760 --> 0:01:50.040 about how speakers work and how they are able to 0:01:50.120 --> 0:01:54.000 take electricity and make those sweet, sweet sounds for your 0:01:54.080 --> 0:01:57.520 ear holes. So let us jump back with a quick 0:01:57.560 --> 0:02:01.919 explanation of the electro magna at is um. So, electricity 0:02:01.920 --> 0:02:05.320 and magnetism are very closely related, and you've likely done 0:02:05.320 --> 0:02:09.200 the simple physics exercise of creating a basic electro magnet. 0:02:09.639 --> 0:02:12.440 So you'll take something like an iron nail and you'll 0:02:12.480 --> 0:02:16.280 wrap insulated copper wire in a coil around the nails 0:02:16.320 --> 0:02:20.480 several times. The nail acts as a ferromagnetic core. The 0:02:20.520 --> 0:02:24.440 copper wire coil is a conductor, so connecting the ends 0:02:24.440 --> 0:02:27.799 of the copper wire to a battery will then allow 0:02:27.880 --> 0:02:31.720 current to flow through the wire. Middle flow from one 0:02:31.800 --> 0:02:34.640 end of the battery through the wire down into the 0:02:34.680 --> 0:02:37.560 other end of the battery. As it goes around this coil, 0:02:37.840 --> 0:02:41.480 the flow of electricity creates a magnetic field, the nail 0:02:41.639 --> 0:02:45.240 and coil will behave like a permanent magnet. Would it's 0:02:45.240 --> 0:02:47.480 an electro magnet, but it will behave like a permanent 0:02:47.520 --> 0:02:50.440 magnet with a north pole and a south pole. And 0:02:50.440 --> 0:02:52.959 if you brought it close to a permanent magnet, then 0:02:53.040 --> 0:02:56.720 the opposite poles would attract each other and the similar 0:02:56.720 --> 0:02:58.920 poles would repel each other. So if you brought the 0:02:58.919 --> 0:03:02.079 electromagnets more poll next to a permanent magnets north pole, 0:03:02.120 --> 0:03:05.400 it would push that other magnet away and the polls 0:03:05.440 --> 0:03:10.240 will not change. Because the source of electricity is a battery, 0:03:10.520 --> 0:03:14.240 and batteries provide direct current, which means the current is 0:03:14.280 --> 0:03:17.480 always going to flow in the same direction. It's never 0:03:17.560 --> 0:03:21.480 going to reverse. But if you hooked the same nail 0:03:21.600 --> 0:03:25.480 and coil up to a source of alternating current, things 0:03:25.480 --> 0:03:29.640 would be very different. With alternating current, the direction of 0:03:29.680 --> 0:03:34.400 the flow of electricity changes rapidly every second, and as 0:03:34.440 --> 0:03:38.280 the direction of electricity changes, it affects the magnetic field. 0:03:38.600 --> 0:03:41.080 With electricity flowing in one direction, the head of the 0:03:41.160 --> 0:03:44.320 nail might represent the north pole of the magnet, and 0:03:44.360 --> 0:03:47.280 when the electricity switches to the other direction, the head 0:03:47.280 --> 0:03:49.960 of the nail will become the south pole of the magnet, 0:03:50.160 --> 0:03:54.160 and vice versa. You have created a fluctuating magnetic field 0:03:54.320 --> 0:03:58.160 by running an alternating current through an electro magnet, and 0:03:58.200 --> 0:04:01.080 you can do some pretty cool stuff with a fluctuating 0:04:01.120 --> 0:04:04.800 magnetic field. For example, if you bring this apparatus close 0:04:04.840 --> 0:04:09.440 to a conductive material, you'll induce a change of voltage 0:04:09.840 --> 0:04:14.080 in that material, even without making physical contact between the two. 0:04:14.480 --> 0:04:17.240 So if you do this with a stable magnetic field, 0:04:17.720 --> 0:04:20.479 all you'll do is see a very short spike, but 0:04:20.520 --> 0:04:23.680 then it stops because the magnetic field is not fluctuating. 0:04:24.080 --> 0:04:27.640 To induce electricity to flow by changing voltage in this 0:04:27.720 --> 0:04:32.279 other conductor, the magnetic field has to be fluctuating, or 0:04:32.360 --> 0:04:34.000 the conductor has to be moving in and out of 0:04:34.040 --> 0:04:37.599 the magnetic field constantly. If you get two coils of 0:04:37.680 --> 0:04:41.000 copper wire and you make sure the second copper wire 0:04:41.160 --> 0:04:44.600 has twice as many coils as the first one, you 0:04:44.640 --> 0:04:48.679 can create a transformer. So imagine you've got your first 0:04:48.720 --> 0:04:51.880 coil of wire. Let's say it's got ten coils ten 0:04:52.040 --> 0:04:55.960 ten loops around its core, and you've got a second 0:04:56.200 --> 0:05:00.400 core with copper wire, but there are twenty loops around 0:05:00.560 --> 0:05:03.800 the second core if you run a current through the 0:05:03.839 --> 0:05:08.000 first coil, it will induce current to flow through the 0:05:08.040 --> 0:05:12.479 second coil. Moreover, the voltage in the second coil will 0:05:12.480 --> 0:05:16.000 be higher than the voltage in the first coil because 0:05:16.160 --> 0:05:19.599 the second coil has twice as many coils as the 0:05:19.640 --> 0:05:23.320 first one. So the more times you loop a wire 0:05:23.440 --> 0:05:27.760 around a core, the greater the change of voltage is 0:05:27.800 --> 0:05:32.160 going to be between coil number one and coil number two. 0:05:32.560 --> 0:05:35.479 This particular version of a transformer would be called a 0:05:35.560 --> 0:05:39.960 step up transformer because the secondary coil has more turns 0:05:40.040 --> 0:05:43.400 than the primary coil and steps up the voltage. If 0:05:43.440 --> 0:05:46.640 the opposite were true, if coil number one had ten 0:05:46.720 --> 0:05:50.239 coils or ten loops and coil number two had five loops, 0:05:50.680 --> 0:05:53.920 then that would be a step down transformer. You would 0:05:54.000 --> 0:05:58.279 lower the voltage from primary to secondary. Transformers are what 0:05:58.440 --> 0:06:03.000 made alternating current the more viable solution to supplying electricity 0:06:03.040 --> 0:06:06.200 to homes and businesses back in the early days. Because 0:06:06.839 --> 0:06:10.600 transmitting electricity was all about efficiency. How could you efficiently 0:06:10.640 --> 0:06:14.039 get electricity from a power plant to where it needed 0:06:14.080 --> 0:06:17.240 to be well? If you used alternating current, you could 0:06:17.240 --> 0:06:20.360 create transformers and you could step up the voltage to 0:06:20.760 --> 0:06:24.800 very high levels, and that meant that you could transmit 0:06:24.920 --> 0:06:29.560 power across power lines much more efficiently. If you didn't 0:06:29.600 --> 0:06:32.640 do that, you had so much power loss that you 0:06:32.680 --> 0:06:37.080 would have to have lots of different power generators throughout 0:06:37.080 --> 0:06:40.000 the region in order to supply all the power needs 0:06:40.080 --> 0:06:42.200 of your area, at least back in the old days 0:06:42.240 --> 0:06:44.520 of direct current, because it wasn't easy to step up 0:06:44.560 --> 0:06:48.279 the voltage. And again, high voltage makes it more efficient 0:06:48.320 --> 0:06:52.200 to transmit power across long distances, so in the early days, 0:06:52.440 --> 0:06:55.159 that's why a C went out over d C. These days, 0:06:55.360 --> 0:06:57.160 you could actually do things a little differently if you 0:06:57.200 --> 0:07:00.640 wanted to, and you could go with direct DC power 0:07:01.360 --> 0:07:03.360 if you really wanted to, but it would require a 0:07:03.400 --> 0:07:06.800 big overhaul of the infrastructure. But transformers made a C 0:07:07.080 --> 0:07:11.560 much more practical anyway. Electromagnets are pretty awesome now. With speakers, 0:07:11.800 --> 0:07:15.040 it's not so much about voltage and current as it 0:07:15.080 --> 0:07:17.720 is about making the diaphragm of the speaker move in 0:07:17.800 --> 0:07:21.880 precise ways. With speakers, the electrical current acts as both 0:07:21.920 --> 0:07:24.520 the carrier of information and the means to make the 0:07:24.560 --> 0:07:28.640 diaphragm move. So you start with a steady magnetic field 0:07:28.760 --> 0:07:33.040 inside the basket You can create that steady magnetic field 0:07:33.480 --> 0:07:37.120 either with permanent magnets like I mentioned before, or with 0:07:37.200 --> 0:07:40.240 electro magnets, but it remains the same no matter what. 0:07:40.640 --> 0:07:42.400 The north pole is always going to be the north pole. 0:07:42.440 --> 0:07:44.080 The south pole is always going to be the south pole. 0:07:44.200 --> 0:07:48.000 Inside the frame, that field does not change. The voice 0:07:48.000 --> 0:07:52.120 coil on the cone ends up receiving the variable current 0:07:52.320 --> 0:07:56.520 that came from the transmitter that represents the recorded sound. Now, 0:07:56.520 --> 0:07:59.840 remember the way we record sound, as we typically will 0:08:00.120 --> 0:08:02.800 something like a microphone, and a microphone is essentially a 0:08:02.840 --> 0:08:06.040 speaker in reverse. A microphone has a diaphragm in it 0:08:06.360 --> 0:08:10.080 that vibrates in the presence of sound waves. Those vibrations 0:08:10.320 --> 0:08:14.680 cause fluctuations inside an electric current. You might vary the 0:08:14.760 --> 0:08:19.000 resistance of the circuit, as we talked about with the 0:08:19.000 --> 0:08:24.200 the old Johan Philip Rice approach, and by varying those 0:08:24.640 --> 0:08:27.880 that electric resistance within the circuit, you can fluctuate the 0:08:27.920 --> 0:08:30.440 electric current and then you can send that to a speaker, 0:08:30.880 --> 0:08:33.120 though you would typically send it to an amplifier first, 0:08:33.120 --> 0:08:35.720 but we'll talk about that in a minute. The speaker 0:08:35.800 --> 0:08:39.520 then essentially reverses this process. It takes those fluctuations sends 0:08:39.559 --> 0:08:41.959 them through an electro magnet, which will generate a variable 0:08:41.960 --> 0:08:45.679 magnetic field in response, which then makes the cone vibrate 0:08:45.800 --> 0:08:48.520 within the speaker and essentially do the opposite of what 0:08:48.559 --> 0:08:52.240 the microphones diaphragm was doing and recreate the recorded sound. 0:08:52.720 --> 0:08:56.199 It's pretty cool and pretty elegant, really. So the electrical 0:08:56.280 --> 0:09:00.280 signal representing the recorded sound comes into the speaker, feeds 0:09:00.320 --> 0:09:03.360 into the voice coil creates this fluctuating magnetic field. The 0:09:03.400 --> 0:09:06.560 field interacts with the permanent magnetic field inside the basket, 0:09:06.840 --> 0:09:10.079 either pulling the diaphragm forward in the basket and us 0:09:10.400 --> 0:09:14.800 pushing air outward, or pulling the cone back towards the 0:09:14.840 --> 0:09:17.920 back of the basket and allowing air to come further 0:09:18.040 --> 0:09:22.199 in by creating that lower pressure. And these fluctuations happen 0:09:22.240 --> 0:09:25.880 at high frequencies, so the diaphragm is moving very rapidly 0:09:25.920 --> 0:09:29.200 inside the basket. It's not just pushing out then pulling in. 0:09:29.280 --> 0:09:32.400 It's doing this hundreds or thousands of times per second, 0:09:32.760 --> 0:09:35.640 and it increases or decreases the air pressure as the 0:09:35.640 --> 0:09:39.000 cone pushes those air molecules or suddenly moves away, creating 0:09:39.000 --> 0:09:42.559 more space for them. And because sound is vibration. Those 0:09:42.559 --> 0:09:45.640 air molecules carry the sound up to our ears, and 0:09:45.679 --> 0:09:48.520 then we rock out to a C d C or 0:09:48.520 --> 0:09:50.960 whatever band you happen to like. That isn't nearly as 0:09:51.000 --> 0:09:54.439 cool as a C d C. Now, keep in mind 0:09:54.840 --> 0:09:57.640 what I have described is how a driver works. A 0:09:57.679 --> 0:10:00.760 speaker can and often does have more than one driver, 0:10:01.160 --> 0:10:04.880 and drivers come in different shapes, sizes, and purposes. So 0:10:05.240 --> 0:10:07.560 let's talk a little bit about what those are and 0:10:07.600 --> 0:10:09.320 what they do, and why you need to have different 0:10:09.320 --> 0:10:12.160 ones in the first place. Actually, that last question is 0:10:12.200 --> 0:10:16.360 the easiest answer right away. Remember again, sound is vibration, 0:10:16.679 --> 0:10:20.760 and low frequency sounds have longer wave forms. The points 0:10:20.800 --> 0:10:24.040 of high and low pressure are further apart from each 0:10:24.080 --> 0:10:27.000 other than with high frequency sounds. If you could actually 0:10:27.080 --> 0:10:29.400 see the changes in air pressure due to sound, you 0:10:29.400 --> 0:10:32.040 would see that the low frequency sounds have these larger 0:10:32.120 --> 0:10:34.720 gaps between the high and low pressure points in the 0:10:34.760 --> 0:10:37.120 waves as they move out from the source of sound. 0:10:37.440 --> 0:10:40.480 So you need a cone diaphragm that can vibrate at 0:10:40.480 --> 0:10:44.800 a slower frequency and push air effectively at that speed. 0:10:45.160 --> 0:10:48.080 For that reason, you would typically go with a heavier, 0:10:48.640 --> 0:10:53.079 larger diaphragm, both because the wavelengths of sound are longer 0:10:53.400 --> 0:10:56.320 if you're looking at the lower frequencies, and because making 0:10:56.320 --> 0:10:59.319 the material heavy gives it greater inertia, it takes more 0:10:59.360 --> 0:11:01.560 force to move of the diaphragm, and it will move 0:11:01.559 --> 0:11:04.200 at a pace that will reproduce as low frequency sounds 0:11:04.240 --> 0:11:07.280 you want. This type of speaker falls into the whooffer 0:11:07.720 --> 0:11:11.439 or sub whiffer categories. These are the speakers that create 0:11:11.760 --> 0:11:15.520 the base sounds. A sub whiffer tends to handle frequencies 0:11:15.559 --> 0:11:18.880 from around twenty hurts to two hurts. Think of a 0:11:19.000 --> 0:11:22.199 hurts as how long it takes a wave to pass 0:11:22.240 --> 0:11:25.360 through a given point in one second, or how many 0:11:25.400 --> 0:11:28.160 waves can pass through a given point in one second. 0:11:28.320 --> 0:11:30.559 Al Right, guys, we got some more to chat about 0:11:30.559 --> 0:11:33.040 with speakers. Before I jump into that, Let's take a 0:11:33.080 --> 0:11:43.400 quick break to thank our sponsor. Human hearing ranges from 0:11:43.480 --> 0:11:47.120 twenty hurts, which is twenty waves passing a given point 0:11:47.240 --> 0:11:51.240 in one second, to twenty killer hurts or twenty thousand 0:11:51.400 --> 0:11:55.080 waves passing through a point in one second. This really 0:11:55.080 --> 0:11:57.880 tells you more about the wavelength of the wave itself 0:11:57.960 --> 0:12:01.560 and thus the frequency and then the pitch. Remember, the 0:12:01.720 --> 0:12:05.360 lower frequencies are the lower pitches. The higher frequencies are 0:12:05.360 --> 0:12:08.720 the higher pitches, and that's the frequency range for typical 0:12:08.800 --> 0:12:11.760 human hearing twenty hurts to twenty thousand hurts. Now, I 0:12:11.800 --> 0:12:15.320 can tell you from my experience using a frequency sweeper, 0:12:15.520 --> 0:12:19.920 which will slowly go through a selection of frequencies that 0:12:20.160 --> 0:12:22.880 is all set at the same volume, so you get 0:12:22.920 --> 0:12:25.560 a standard volume across all of them, that while I 0:12:25.600 --> 0:12:28.520 can technically hear stuff at twenty hurts, it's not until 0:12:28.520 --> 0:12:31.240 you hit a frequency of about fifty hurts that it 0:12:31.320 --> 0:12:35.040 quote unquote sounds loud to me, even though actual volume 0:12:35.120 --> 0:12:38.320 of the two tones remains the same, so the amplitude 0:12:38.480 --> 0:12:41.599 is exactly the same, But until you get to a 0:12:41.679 --> 0:12:44.679 frequency of about fifty hurts, it just doesn't sound loud 0:12:44.720 --> 0:12:46.880 to me because my ears are not great at picking 0:12:46.960 --> 0:12:51.080 up those lower, super low frequencies. Also, I should mention 0:12:51.160 --> 0:12:54.599 that while sound waves come in different frequencies, sound itself 0:12:54.800 --> 0:12:58.000 travels at a speed that is dependent upon the medium 0:12:58.160 --> 0:13:01.240 through which it travels. So, in other words, low frequency 0:13:01.280 --> 0:13:04.520 sounds and high frequency sounds travel at the same speed 0:13:04.760 --> 0:13:07.559 through the same medium. Otherwise you would have all the 0:13:07.640 --> 0:13:10.560 high pitched sounds hitting your ears before the low pitched 0:13:10.559 --> 0:13:14.400 ones and conducting an orchestra would drive you crazy. The 0:13:14.440 --> 0:13:17.760 speed of sound is defined as the distance traveled by 0:13:17.760 --> 0:13:21.280 a sound wave in a certain unit of time. But hey, Jonathan, 0:13:21.360 --> 0:13:23.000 some of you might be saying you were just talking 0:13:23.000 --> 0:13:26.040 about frequencies. If a high frequency sound has twenty sound 0:13:26.080 --> 0:13:28.440 waves pass a certain point in the second, and a 0:13:28.480 --> 0:13:31.160 low frequency sound has twenty waves passing that same point 0:13:31.160 --> 0:13:34.720 in the second, are they traveling at different speeds? No, 0:13:34.880 --> 0:13:37.400 they're not. This is easier to imagine if we take 0:13:37.440 --> 0:13:40.080 an analogy. So let's say you're standing on the side 0:13:40.240 --> 0:13:44.200 of the road. Every single vehicle going past you on 0:13:44.240 --> 0:13:47.600 this one way road is traveling at a smooth twenty 0:13:47.600 --> 0:13:50.400 miles per hour or about thirty two kilometers per hour 0:13:50.440 --> 0:13:53.079 if you prefer. But they're all going that speed. Doesn't 0:13:53.120 --> 0:13:55.640 matter what kind of card is, they're all going exactly 0:13:55.679 --> 0:13:59.760 twenty miles or thirty two kilometers per hour. Some of 0:13:59.760 --> 0:14:03.080 these vehicles are very tiny, little smart cars. Some of 0:14:03.120 --> 0:14:06.520 them are super long extended buses, but they're all traveling 0:14:06.520 --> 0:14:09.319 at that same speed. So even though they're going at 0:14:09.320 --> 0:14:12.560 the same speed, the buses take more time to pass 0:14:12.640 --> 0:14:15.920 you than the smart cars do because the buses are longer. 0:14:16.440 --> 0:14:18.880 In the time it takes one super long bus to 0:14:18.920 --> 0:14:21.560 go buy you, like the front passes you and you 0:14:21.640 --> 0:14:25.440 time it out. Maybe for smart cars could go buy 0:14:25.480 --> 0:14:27.440 you and that same amount of time, even though they're 0:14:27.440 --> 0:14:30.160 all going at twenty miles. The same is true with 0:14:30.280 --> 0:14:33.520 sound waves, so we're not just talking about speed but wavelength. 0:14:33.800 --> 0:14:37.920 So low frequency sounds and high frequency sounds are traveling 0:14:37.960 --> 0:14:41.320 at the same speed. It's just you can fit more 0:14:41.360 --> 0:14:45.200 of the waves in at that time than others because 0:14:45.200 --> 0:14:49.440 of the length. All right back to the speed of sound. Now, 0:14:49.480 --> 0:14:52.520 I cannot give you a standard speed of sound for 0:14:52.560 --> 0:14:55.600 all occasions because the speed of sound depends on a 0:14:55.600 --> 0:14:58.640 lot of little things, For example, how much moisture is 0:14:58.680 --> 0:15:02.800 in the air or how cold is the air. Sound 0:15:02.840 --> 0:15:05.400 passes through the air, and air is made up of gases, 0:15:05.440 --> 0:15:08.000 and gases are made up of molecules. So as you 0:15:08.040 --> 0:15:10.840 heat up a gas, the molecules move apart from each 0:15:10.880 --> 0:15:14.680 other and they bounce around more. They're more able to move. 0:15:15.120 --> 0:15:19.840 As gas is cool, the molecules pack around together and 0:15:20.000 --> 0:15:22.560 they move around less, so they get more tightly packed. 0:15:23.000 --> 0:15:26.280 So a cold gas will transmit sound at a slightly 0:15:26.360 --> 0:15:29.960 slower speed than a warm gas will. If the temperature 0:15:29.960 --> 0:15:33.280 outside is sixty eight degrees fahrenheit or about twenties celsius 0:15:33.320 --> 0:15:35.800 and the air is dry, sound will travel at one 0:15:35.840 --> 0:15:41.080 thousand per second or three forty three per second. And 0:15:41.160 --> 0:15:44.560 it doesn't matter what frequency sound waves you're working with, 0:15:44.720 --> 0:15:47.480 that's the speed they're going to travel at. And again, 0:15:47.520 --> 0:15:50.080 at different temperatures and there are different media, sound will 0:15:50.080 --> 0:15:52.160 travel at a different speed. All right. Now, let's go 0:15:52.200 --> 0:15:55.480 back to the different types of drivers. After you handled 0:15:55.520 --> 0:15:59.360 the sub whoffers and the whoofers, well, the whoffers will 0:15:59.360 --> 0:16:03.480 still handle lower frequencies, but subwhiffers are are specialized whoffers, 0:16:03.840 --> 0:16:07.440 largely because they will frequently be paired with special circuits 0:16:07.480 --> 0:16:11.600 and cabinets dedicated to creating those very very low frequencies 0:16:11.760 --> 0:16:14.080 in an effort to produce a specific quality of sound, 0:16:14.320 --> 0:16:16.520 such as let's say you're watching an action film and 0:16:16.600 --> 0:16:19.160 something done blowed up real good. You want to have 0:16:19.240 --> 0:16:21.840 that rumbly low base for those moments, you know, the 0:16:21.920 --> 0:16:25.400 kind where you can actually feel it because it's vibrating 0:16:25.600 --> 0:16:28.280 the chair and the air around you, and so it's 0:16:28.320 --> 0:16:30.720 it's that kind of rumble you can feel in your chest. Well, 0:16:30.760 --> 0:16:33.560 that frequently means you need a dedicated subwhoffer unit that 0:16:33.600 --> 0:16:37.240 has its own power supply to generate the vibrations with 0:16:37.440 --> 0:16:40.520 enough force necessary to create that effect. So it's not 0:16:40.560 --> 0:16:44.560 just the speed but how hard it's pushing. After subwhiffers 0:16:44.600 --> 0:16:48.840 and whoffers, you've got mid range drivers or mid range speakers, 0:16:48.840 --> 0:16:51.760 and as the name suggests, these drivers are responsible for 0:16:51.800 --> 0:16:54.880 producing sounds in the middle range frequencies of human hearing. 0:16:55.120 --> 0:16:57.920 A typical range might include two fifty hurts to two 0:16:57.960 --> 0:17:01.840 thousand hurts. You may have also the term squawker when 0:17:01.920 --> 0:17:05.600 referencing mid range speakers. They're made of lighter materials and 0:17:05.640 --> 0:17:09.160 they can vibrate at higher frequencies than whiffers and subwhiffers, 0:17:09.280 --> 0:17:12.359 which is necessary to create those mid range tones. And 0:17:12.400 --> 0:17:15.639 then you have tweeter speakers. These are made of the 0:17:15.720 --> 0:17:18.480 lightest weight material and they vibrate the fastest in an 0:17:18.480 --> 0:17:21.960 effort to reproduce frequencies on the upper levels of human hearing, 0:17:22.320 --> 0:17:24.959 which tends to be between two thousand and twenty thousand 0:17:25.000 --> 0:17:28.159 hurts at least for consumer speakers. There are tweeters that 0:17:28.160 --> 0:17:30.960 can be made for special purposes that can generate sound 0:17:31.000 --> 0:17:33.919 frequencies well above the range of human hearing, some of 0:17:33.920 --> 0:17:36.040 them as high up as a hundred kill hurts or 0:17:36.160 --> 0:17:39.600 one hundred thousand hurts. That's five times higher than the 0:17:39.680 --> 0:17:43.119 highest frequency the average human is capable of perceiving. So 0:17:43.160 --> 0:17:46.160 why would you want a tweeter that could go beyond 0:17:46.480 --> 0:17:48.919 the range of human hearing. Well, you might use it 0:17:48.960 --> 0:17:53.040 for scientific research purposes, like finding out what high high 0:17:53.080 --> 0:17:58.040 high pitches the ultrasonic pitches might due to affect animal behavior. 0:17:58.280 --> 0:18:00.320 So you might be able to do that to learn 0:18:00.520 --> 0:18:03.560 how high a pitch a dog might be able to hear, 0:18:03.600 --> 0:18:06.200 for example, because dogs can hear at a different range 0:18:06.200 --> 0:18:09.040 than humans can. Or you might want to do experiments 0:18:09.359 --> 0:18:13.679 to see if those imperceptible frequencies have an effect on 0:18:13.760 --> 0:18:17.600 the sounds we can here. So there are audio files 0:18:17.800 --> 0:18:21.760 who insist that frequencies beyond the human range of hearing 0:18:22.080 --> 0:18:25.320 can change the quality of the sounds that we do here, 0:18:25.720 --> 0:18:28.600 and thus it's imperative to get a sound system and 0:18:28.680 --> 0:18:31.960 a type of media capable of reproducing sound frequencies at 0:18:31.960 --> 0:18:34.639 every level if you want a true reproduction of an 0:18:34.680 --> 0:18:39.440 original sounds quality. This falls into the realm of psychoacoustics 0:18:39.480 --> 0:18:43.800 the study of sound perception. Because hearing involves processes in 0:18:43.800 --> 0:18:47.320 the brain, there is a subjective component to it that 0:18:47.400 --> 0:18:50.640 cannot be easily described through physics. We can talk all 0:18:50.680 --> 0:18:54.400 about the physics of sound waves and sound propagation, but ultimately, 0:18:54.400 --> 0:18:57.320 when it comes to the way we experience sound, we 0:18:57.400 --> 0:19:00.480 have to take gray matter into account, and that gets 0:19:00.520 --> 0:19:03.760 tricky since our experience of perceiving sound can depend upon 0:19:03.880 --> 0:19:07.320 other things unrelated to the actual physics of the sound itself. 0:19:07.600 --> 0:19:10.359 For example, if I were to tell you that I 0:19:10.440 --> 0:19:12.600 have a sound system, and I've set it up and 0:19:12.640 --> 0:19:17.680 it consists of the most expensive and most technologically advanced components, 0:19:18.040 --> 0:19:20.600 and the media that was going to play represented the 0:19:20.600 --> 0:19:23.960 most true reproduction of an actual sound, that might be 0:19:24.080 --> 0:19:27.120 enough to influence your perception of the sound. Even if 0:19:27.200 --> 0:19:30.719 what I was really using was just good equipment, not 0:19:30.800 --> 0:19:33.960 the best, but just good stuff. Even if all all 0:19:33.960 --> 0:19:35.840 that stuff I told you wasn't true, your perception of 0:19:35.840 --> 0:19:38.240 sound might make it seem like you're listening to the 0:19:38.280 --> 0:19:41.840 most perfect reproduction of the original performance as could be attained. 0:19:42.400 --> 0:19:44.720 Or if I did play a sound back on what 0:19:44.840 --> 0:19:48.760 really was an amazing sound system, but Before I did it, 0:19:48.800 --> 0:19:51.199 I made a whole bunch of apologies for how the 0:19:51.240 --> 0:19:54.600 system I was using could not faithfully represent high tones, 0:19:54.840 --> 0:19:57.400 or had a very weak base output, or something like that. 0:19:57.760 --> 0:20:01.560 You might perceive the playback as fall lewing these trends 0:20:01.600 --> 0:20:04.960 that I had mentioned, even if scientific recording instruments were 0:20:05.000 --> 0:20:07.399 to show that the playback didn't suffer from those problems 0:20:07.440 --> 0:20:10.720 at all. All that being said, the psychological aspect of 0:20:10.720 --> 0:20:13.679 how we perceive sound does have limitations. No amount of 0:20:13.680 --> 0:20:16.800 snake oil salesmanship is going to convince you that a 0:20:16.880 --> 0:20:20.520 truly subpar stereo system is capable of reproducing the glory 0:20:20.600 --> 0:20:24.280 of the Philharmonic Orchestra, for example. But because there is 0:20:24.359 --> 0:20:27.560 the subjective element and how we perceive sound, there's the 0:20:27.560 --> 0:20:30.439 opportunity to exploit that element and make a lot of 0:20:30.440 --> 0:20:32.879 money in the process. I've talked before about how certain 0:20:32.920 --> 0:20:36.080 manufacturers have used this to market high end audio equipment, 0:20:36.480 --> 0:20:39.240 and some of that has little to no scientific evidence 0:20:39.240 --> 0:20:41.960 to back up the claims that they make about those gadgets, 0:20:43.119 --> 0:20:45.879 and yet they're able to set exorbitant prices for components 0:20:45.880 --> 0:20:48.399 that audio files will cover it because they're always in 0:20:48.400 --> 0:20:52.600 a quest to get that perfect representation of a sound. Uh, 0:20:52.720 --> 0:20:56.160 so this stuff does happen. I also covered this when 0:20:56.160 --> 0:20:59.200 I talked about MP three compression, because if you remember 0:20:59.400 --> 0:21:02.919 an MP threes, part of the compression strategy is to 0:21:02.960 --> 0:21:05.639 take all the different parts of a sound that we 0:21:05.800 --> 0:21:09.399 humans typically don't notice, and you just cut them. You 0:21:09.440 --> 0:21:11.400 get rid of them, because that way you cut down 0:21:11.440 --> 0:21:15.080 on the size of the sound file. The strategy is, 0:21:15.400 --> 0:21:18.639 if you can't perceive it, then we don't need it 0:21:18.800 --> 0:21:21.520 in the information. We can just cut it that. Audio 0:21:21.560 --> 0:21:23.919 files say no, if you do that, it affects the 0:21:23.960 --> 0:21:27.280 stuff that we can here, and thus you are changing 0:21:27.320 --> 0:21:31.440 the nature of the audio recording. Just because you couldn't 0:21:31.480 --> 0:21:35.000 hear the thing doesn't mean the thing wasn't doing something else. 0:21:37.160 --> 0:21:39.080 I think the jury is still out on that in 0:21:39.119 --> 0:21:42.639 a large part. I mean, there are some legitimate arguments 0:21:42.680 --> 0:21:45.520 to make about harmonics and things that do come into play, 0:21:46.240 --> 0:21:48.040 but I'm not sure it gets to the level of 0:21:48.080 --> 0:21:51.080 subtlety that a lot of audio files argue. At least 0:21:51.119 --> 0:21:53.879 I don't see the scientific evidence supporting it. That doesn't 0:21:53.880 --> 0:21:55.840 mean it's wrong, It just means I haven't seen the 0:21:55.880 --> 0:21:59.880 evidence supporting it. Anyway, As soon as we come back. 0:22:00.000 --> 0:22:03.920 I'm gonna go into talking about amplification and why that's important, 0:22:03.920 --> 0:22:07.000 but first let's take another quick break to thank our sponsor. 0:22:14.160 --> 0:22:15.800 All right. Now, Back when I was talking about the 0:22:15.800 --> 0:22:18.240 development of the loud speaker, I mentioned that Rice and 0:22:18.320 --> 0:22:22.280 Kellogg observed there needed to be advancements in amplification, and 0:22:22.359 --> 0:22:24.200 by that they meant there needed to be a way 0:22:24.240 --> 0:22:28.560 to boost the electrical signal from the risk the transmitter 0:22:28.720 --> 0:22:32.320 the microphone in order to give a speaker enough umph 0:22:32.480 --> 0:22:35.160 to vibrate at a force strong enough to play back 0:22:35.200 --> 0:22:39.399 the sounds at a suitable volume. Without amplifiers, the signal 0:22:39.520 --> 0:22:41.879 strength might only allow a speaker to play back a 0:22:41.960 --> 0:22:45.080 sound at a low volume, or if the signal is 0:22:45.200 --> 0:22:48.480 very weak, it might not even move the speaker significantly 0:22:48.640 --> 0:22:52.080 enough at all to create any real sound. The reason 0:22:52.119 --> 0:22:54.560 the signal tends to be weak goes back to the 0:22:54.640 --> 0:22:57.600 limitations we face when we record sound in the first place. 0:22:57.960 --> 0:23:02.200