- 9 giờ trước
Quá trình chế tạo loa không dây kèm thêm đèn laser siêu sáng
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00:00In the 1980s, before wireless headphones existed and before Wi-Fi speakers were a thing,
00:06there was an audio port known as Toslink or SPDIF that's still present on modern devices.
00:12And it's got a secret. A simple modification that can be made to it that allows it to transmit
00:18audio completely wirelessly with zero latency and no compression. Something even state-of-the-art
00:26wireless protocols can only dream of. The key to this modification lies in the fact that it's an
00:32optical port. It doesn't use copper cables, but instead relies on a clear plastic fibre that
00:37transports light from one end to the other. The light it transports is from a red LED,
00:42which flashes on and off extremely rapidly with an encoded digital audio signal. So long as this
00:48flashing light can be seen by a Toslink receiver, it will deliver fully uncompressed, dual-channel audio
00:54without any perceptible latency. It's a fairly robust signal as well. Splitting a cable in half still
01:01allows the light through, even if the two halves don't actually touch, meaning that there's an air
01:06gap. That's technically wireless audio right there. Now, seeing as all this cable does is constrain the
01:14light from the LED so that it's visible at the other end, would it be possible to get rid of
01:19it
01:19entirely if we replace the LED with a light source that doesn't diverge? Like that, save from a laser
01:26diode. The light output from a laser diode barely diverges when compared to that of an LED, so an
01:32optical fibre isn't necessary to transport it long distances. It can just shine there all on its own.
01:38To see whether this will work with a digital audio stream, I've got a cheap audio encoder that can take
01:43an analogue audio signal and encode it into the SPDIF format through a Toslink connector. And taking
01:49the back off, we can see the three pins that make the Toslink transmitter bit work. Checking this out
01:55with a multimeter, it appears that there is a signal voltage going through it at almost three volts, which
02:00is pretty convenient because low-power three-volt laser diodes are readily available on places like
02:05Amazon. Being class one lasers, they are low power enough to be considered safe. No fires and no burned
02:12eyeballs. Hooking one up to the three-volt signal, we can see that it immediately illuminates and is
02:18presumably flashing at the same rate as the LED, hopefully containing all of the audio data as a
02:24result. So that we can hear whether it is working, I've got a similar SPDIF adapter, only this one receives
02:30a digital audio signal and converts it to analogue rather than the other way around. Now, a Toslink
02:35port always includes a little plastic hinged cover, so this needs to be removed first so that the laser
02:40can reach the receiver's sensor unobstructed. Having the laser illuminate this tiny sensor though does
02:46require quite a bit of precision, so to mitigate this somewhat we can cut a strip of HDPE from a
02:51bottle and fold it into the opening. This strip fully illuminates when the laser hits it, making the
02:57receiving surface significantly larger. For testing purposes, I'm just mounting it to an old bookshelf
03:03speaker which has a little battery-powered amplifier hot glued to its back. So here we have our
03:09transmitter with its new laser that hopefully contains all of the audio data encoded within it,
03:15and the receiver is obviously over here on its speaker. So when I remove this piece of paper we
03:20should, in theory, hear completely lossless, lag-free digital audio.
03:28That's pretty cool. Now, the distance that this works is really surprising. It can go through four
03:33sheets of glass into a different building if you want it to. It's pretty wild. And again, I'd just
03:38like to emphasize that this is completely uncompressed audio and lag-free, something that's simply not
03:43possible with other wireless methods like Bluetooth. Now, of course, it is line of sight required, which
03:49does limit its usefulness somewhat. However, it still brings to the table a lot of really interesting
03:54DIY audio product opportunities, the most exciting of which I think is a homemade wireless surround
04:01sound system. This would eliminate the requirement of draping speaker wires all over the place. The audio
04:07can instead be beamed straight to them wirelessly, and as it's optical it won't interfere with wi-fi
04:13signals or have any latency issues. For making them, while we could just strap receivers onto old
04:18bookshelf speakers just like this, I've been wanting to make a proper DIY surround sound system for
04:24literally years, and I've come up with a design that strikes a really good balance between both
04:29performance and price, using some very interesting construction methods. These construction methods rely on
04:36the use of 3D printing, which is a fantastic way of building speakers at home because you simply
04:41don't need a workshop or any particular tools other than a 3D printer, which are more common than ever
04:46these days. In an effort to keep the overall cost in check, the design is to be based around a
04:51quite
04:52remarkable speaker driver, the Dayton Audio TCP-115. This retails at just $13 at the time of publication,
05:01which is crazy good value considering that it can not only function as a decent mid-tone driver,
05:05but can also play well as a subwoofer too, which is why we'll need a pair of them, one for
05:10each of
05:11these roles. With these two functions in mind, I've designed a speaker enclosure that is volumetrically
05:16optimised for this particular driver, and the printable files have been made available in the
05:20video's description. As you can see, its design features hollow walls to reduce both filament use
05:26and print times, and the idea is to fill them with a special mixture later to give them the mass
05:32that
05:32they need to become true hi-fi class enclosures. It's also been divided up into a few different
05:37parts to ensure compatibility with even fairly modest print bed sizes, so this does mean that
05:43they need some assembly by screwing them together. The first job is to screw the two main enclosure
05:48units together to make them a solid unit with two distinct compartments, the bottom one being
05:54exclusively for a special subwoofer system, which requires a few extra printed parts to make it work,
05:59the first being a custom coupler for the bottom, using plenty of glue to make an airtight seal,
06:05as well as an internal insert to divide the subwoofer area in half and function as a flared exit port,
06:10which will reduce chuffing noises when the final system is operational, and you'll see how it all
06:15works in just a moment. So with that done, we can now divert our attention to the top compartment,
06:20which forms the chamber for the mid-tone speaker driver, where the hollow walls are ready for a special
06:25Plaster of Paris mixture. What makes this mixture special is simply the addition of some standard
06:30PVA glue to it, which stops the Plaster of Paris from having a ringing quality, a bit like a teacup,
06:36and it's a quick hack to make it suitable for using in speaker enclosures to give them the mass that
06:41they need to sound great. Adding it can be quite a messy process if you're not careful, but it's a
06:46lot
06:47of fun and it reminds me of school craft days. Making the walls this way saves so much print time
06:53without
06:53having to make any acoustical compromises, and it's my favourite method of constructing speakers by far.
06:59Adding acoustic foam to the inside walls is a good idea as well, as it reduces internal sound
07:04reflections and results in a noticeably cleaner sound quality, especially when complemented with
07:09sheep's wool, which you'll see me add later. It's a good idea to add this acoustic foam to the Plaster
07:15of
07:15Paris filled back panel as well, which can be used to seal up the unit nicely. So with that we
07:22essentially
07:22have our finished speaker enclosure, and we can start now thinking about the aesthetics to hide the fact that
07:28it's been 3D printed. This is fairly easy to do. Any joints can be filled with normal decorators filler,
07:35after which it can be thoroughly painted with plastic primer, followed by a top coat of your choosing,
07:41mine being a heavily textured aged iron effect specialty paint. This makes them look really cool,
07:47and you wouldn't at all think they're 3D printed, especially as they feel so solid thanks to the
07:53Plaster of Paris. So with the aesthetics sorted, at this point the speaker drivers themselves can
07:59finally be added, starting with the tweeter, which is for handling the high frequency notes that the
08:03midtone driver can't reproduce very well. This can simply be soldered up, popped into its hole,
08:09and then screwed in place. This same process is required for the midtone driver and base driver as
08:15well, they just need to be soldered up, dropped into their holes and screwed down. Now this is
08:20starting to look quite promising, but to finish it off properly it really needs a front facade,
08:26another job for the 3D printer. Some filling, sanding and painting later, it too can be mounted to the
08:32unit, hiding the speaker rims and screws and making it look very neat indeed, especially considering how
08:38simple they are to actually construct. For this base driver to do its work properly though, and reach
08:45notes as low as 35 hertz, its chamber needs to be hooked up to some tubes to create what's known
08:50as a transmission line configuration. Now as these tubes are going to be quite visible, it's worth going
08:56with some that are made from acrylic, as it'll make them appear much less obtrusive in a room. Again,
09:02plenty of glue needs to be used when attaching these to maintain that airtight seal, as even the smallest
09:08gap can adversely affect sound quality. So that the sound waves travel down one tube and up the
09:15other, essentially making a two meter long transmission line, they can be joined together
09:19at the bottom with a little end cap coupler, which again has been 3D printed. This is what the flared
09:25exit port is for, by the way. It smooths out the transition for the air as it goes in and
09:29out of
09:30these tubes. Once the glue has finally cured, you can see that while it can stand, it is a bit
09:36wobbly,
09:36but that's easily fixed by mounting it onto a wooden foot. I thought that this bamboo chopping
09:42board would look quite nice, but it really doesn't match the aesthetic, so I may just paint over it
09:46with the textured paint at a later date. Either way though, the unit itself looks visually very smart.
09:52The acrylic tubes do a great job of providing support without being obtrusive, holding the speaker
09:58at a good listening height. What's particularly cool is that they provide a function as well,
10:03as the physical delay that they add to the base driver's rear sound waves converts them into being
10:09complementary to its forward sound waves, providing low frequency performance that doesn't feel like
10:14it should at all be possible given the size of the unit. Flat down to 35 hertz does approach dedicated
10:20subwoofer territory after all. Now the idea is to make four of these units for a surround sound setup,
10:27two for the front and two for the rear. But how are we going to focus our laser beams onto
10:33them so that
10:33they each receive their respective digital audio signal? Well, this is where a fifth speaker can come
10:40into play. You see, a surround sound system usually relies on a centre channel for dialogue and important
10:46sound cues, so it's a perfect place from which we can propagate our laser signals from. Its design is very
10:53similar to our surround sound speakers, consisting of multiple parts that can be mounted together with
10:58glue and screws. One interesting difference, however, is that its entire perimeter walls are to be filled
11:04with our special plaster of Paris mixture, as the whole unit will be dedicated to mid-tone use without
11:09its own built-in subwoofer. This is because we're going to be sending these subwoofer frequencies to the
11:14two front surround sound speakers adjacent to it, which is a really efficient way of mixing it into the track.
11:21Again, after the usual finishing process, this makes for quite a nice enclosure, with the mid-tone
11:26driver taking centre stage. One thing, though, that you might be wondering is, where's the tweeter?
11:32Well, the idea is to have the tweeter mounted to its own little chamber on top. This isn't just an
11:38aesthetic choice, although it does look pretty cool, but is primarily a decision to keep the tweeter
11:43time-aligned with the mid-tone driver. You see, on many centre channels, the tweeter sits between two mid-tone
11:48woofers. Not a problem if you're sitting directly in front of it, but if anyone else is off-axis,
11:54they can be left in an interference trough, where important vocal frequencies dip in volume
12:00significantly. This happens because of the slight horizontal distance between the tweeter and woofers,
12:06which means that the sound waves from them won't always land at the listener at the same moment
12:10from an off-axis listening position, causing them to cancel out. This is why I've decided to have the tweeter
12:16mounted above the mid-tone driver, because it doesn't matter how far off-axis you are, the sound
12:21from either speaker will arrive at you at the same moment, avoiding the interference trough.
12:26So, either way, we have now got our centre channel, and it's time to add the laser distribution system
12:32to it so that we can beam audio to our surround sound speakers. As you might expect, this is going
12:38to
12:38be based entirely around some small, cheap, analog-to-digital spdiff Toslink converters.
12:45By soldering four of them up to a little terminal block, we essentially have a four-channel laser
12:51distribution system, with the lasers sitting snugly in the 3D print. Before we can mount it in place,
12:57though, we do need to do a bit of prep work on the centre channel. You see, these Toslink converters
13:03don't do any amplification. That needs to be handled by a separate amplifier. The one I have here can
13:08sit within the chamber on the back, and be screwed in place and wired up to the speakers. To ensure
13:14that each speaker receives only the frequencies that they're best at reproducing, we'll be passing
13:18the signals through a little digital signal processor. This will allow us to program different
13:23response curves and frequency shelves to optimise for each driver, squeezing even more performance out
13:29of them. This too can be mounted onto its own block next to the amplifier and wired up to it,
13:35leaving one last area for the laser distribution block, which likewise can be mounted in place and
13:40wired up. All of these wires and circuit boards do of course look quite messy, but that's okay,
13:46as the intention is to cover them up with some back panels. As you can see, all of the connectors
13:51for
13:51the signal inputs have been angled downwards, and this saves a lot of space, as the intention is to
13:57actually have this centre channel speaker mounted on some wall brackets above a TV, as this keeps it
14:03nicely out of the way far away from the floor in a good position to be heard clearly. Plugging in
14:09its
14:09power, we can see that the lasers are successfully firing at the ceiling. Now these upward firing lasers
14:18might seem like a bit of an odd design choice, seeing as we need the speakers around the room and
14:22not on the
14:23ceiling, but the idea is to actually use some little articulating mirrors to bounce the lasers to where
14:30we need them. These have been made from a few 3D printed parts, and as they can be adjusted in
14:35rotation
14:35and mirror angle, we can use them to direct the lasers wherever we want in a room, using more mirrors
14:41at the other end to bounce the lasers back down towards the speakers. The beauty of this is that the
14:47lasers
14:47are kept out of the way along the ceiling, so that their line of sight can never be broken by
14:52people
14:53walking in front of them, nor any of the alignments disturbed. It's a set it and forget it configuration,
14:58and it really is the only way that this wireless system makes any sense. So now that we have our
15:04lasers
15:05dotted around the room to approximately where we want our speakers to be, we need to enable the speakers
15:10to be able to decode the audio signal contained within. This of course is where the SPDIF TOSLINK
15:16receivers come into play, just like the standalone bookshelf demonstration earlier. Instead of going
15:22directly to an amplifier though, we'll be following the signal path with another digital signal processor,
15:28so that we can make sure that each of the three drivers within the surround sound units can get an
15:32optimised audio signal, which is particularly important for their built-in subwoofers. A perfect spot to
15:38mount these is the rear chamber on the back, where there's space for the same style of amplifier we
15:42used for the centre channel. Just like there, this powers each driver independently, receiving its input
15:48from the digital signal processor, which as you can see, has been mounted onto a back panel. This allows
15:54the whole thing to be neatly closed up, with the TOSLINK receiver facing upwards on the back, ready to
15:59receive its laser signal. Having already set these up, our new wireless surround sound units can simply be
16:06slid in position, so that the lasers hit the TOSLINK receivers, providing each one with lossless,
16:12lag-free audio that literally operates at light speed. Being powered speakers, they do of course
16:19need to be plugged into a wall socket, so they're not 100% wireless, but that's fine by me, as
16:24there are
16:25usually plenty of these to choose from around a room. Now to get a surround sound signal to the centre
16:31channel for it to then redistribute to the other speakers, we're going to be using one of these
16:35little surround sound extraction boxes. These are very low cost compared to a normal AV receiver,
16:41so are a perfect choice that plays a part in keeping the overall system cost down. You can use
16:46them to extract uncompressed surround sound from an HDMI connection, allowing the speakers to have
16:52uncompressed audio end-to-end, which is pretty neat for a wireless system. From my testing, it performs
16:59brilliantly. The audio is crisp and sharp, and in sync with the TV's image, and the bass is sublime.
17:06The fact that each of the surround channels go down flat to 35 hertz without requiring a separate
17:13subwoofer makes the soundstage really enveloping, and it's so cinematic. And the surround sound effect
17:19you get from the rear channels at the back of the room really contributes as well. Now the best bit
17:25is
17:25that using brand new parts, this entire setup costs about the same as a mid-range soundbar, which is
17:31incredibly good value for any surround sound speaker set, yet alone one that works wirelessly with zero
17:38latency and no compression. Pretty cool. Now I can hear some of you saying that, Matt, humans can hear down
17:46to 20 hertz. 35 hertz just isn't going to cut it for a cinematic experience. Well, I've got you covered.
17:53Now this is somewhat experimental, but according to my calculations, we can use a three meter long
17:59PVC pipe to hit these low notes using another transmission line configuration. Now of course,
18:06as this is so long, we do need to trim it down into sections. This makes its size much more
18:13manageable,
18:13and to join it back up again, we can simply use some more 3D printed parts. As the plan is
18:18to use two
18:19TCP-115 drivers coupled together with it, there'll be a lot of air movement to contend with, so it too
18:27needs a flared exit port to reduce chuffing noises, just like on the main surround sound speakers.
18:33Now this is admittedly incredibly ugly, which is why it's to be considered a bonus rather than a
18:38completed project item, but as it's slim enough to slide behind a TV, it can't be seen anyway,
18:43so it doesn't matter too much. Now the amplifier used in the center channel speaker has two spare
18:48channels, so these can be used to power each individual driver with the appropriate subwoofer
18:53frequencies. Right now it's playing a 25 hertz test tone, you probably need headphones to hear it at
18:59all, but it's really deep. It feels like there's a standing wave from a car outside or something,
19:04it's kind of crazy. You can feel it in your chest, that's wild.
19:15It was literally a childhood dream of mine to make a proper surround sound system, so to have made one
19:20that sounds so good and works wirelessly using lasers is a pretty good feeling.
19:26Don't forget that if you'd like to build a set of these speakers for yourself, you can find the
19:31printable files for them in the video's description, along with a link to the LTT
19:35ratcheting screwdriver if you'd like to buy one to help you construct them. But other than that,
19:41I'm Matt, you've been watching DIY Perks, and I hope to see you next time. Goodbye for now.
19:46Bye for now.