in the 1980s before wireless headphones existed and before Wi-Fi speakers were a thing there was an audio port known as toss link or SPD that's still present on Modern devices and it's got a secret a simple modification that can be made to it that allows it to transmit audio completely wirelessly with zero latency and no compression something even state-of-the-art Wireless protocols can only dream of the key to this modification lies in the fact that it's an optical Port it doesn't use copper cables but instead relies on a clear plastic fiber that transports light from one
end to the other the light it transports is from a red LED which flashes on and off extremely rapidly with an encoded digital audio signal so long as this flashing light can be seen by a toss link receiver it will deliver fully uncompressed dual Channel audio without any perceptible latency it's a fairly robust signal as well splitting a Cable in half still allows the light through even if the two halves don't actually touch meaning that there's an air gap that's technically wireless audio right there now seeing as all this cable does is constrain the light
from the LED so that it's visible at the other end would it be possible to get rid of it entirely if we replace the LED with a light source that doesn't diverge like that say from a laser diode the light output from a laser diode barely diverges when compared to that of an LED so an optical fiber isn't necessary to transport it long distances it can just shine there all on its own to see whether this will work with a digital audio stream I've got a cheap audio encoder that can take an analog audio signal
and encode it into the SPD format through a toss link connector and taking the back off we can see the three pins that make the toss link transmitter bit work checking this out with a multimeter it appears that there is a signal voltage going through it at almost 3 Vols which is pretty convenient because low power 3vt laser diodes are readily available on places like Amazon being class one lasers they are low power enough to be considered safe no fires and no burned eyeballs hooking one up to the 3vt signal we can see that it
immediately illuminates and is presumably flashing at the same rate as the LED hopefully containing all of the audio data as a result so that we can hear whether it is working I've got a similar spde adapter only this one receives a digital audio signal and converts it to analog rather than the other way around now a toss link Port always includes a little plastic hinged cover so this needs to be removed first so that the laser can reach the receiver's sensor unobstructed having the laser illuminate this tiny sensor though does require quite a bit of
precision so to mitigate this somewhat we can cut a strip of hdp from a bottle and fold it into the opening this strip fully illuminates when the laser hits it making the receiving surface significantly larger for testing purposes I'm just mounting it to an old bookshelf speaker which has a little battery powered amplifier hot glued to its back so here we have our transmitter with its new laser that hopefully contains all of the audio data encoded within it and the receiver is obviously over here on its speaker so when I remove this piece of paper
we should in theory hear completely lossless LaGree digital [Music] audio that's pretty cool now the distance that this works is really surprising it can go through four sheets of glass into a different building if you want it to it's pretty wild and again I'd just like to emphasize that this is completely uncompressed audio and lag free something that's simply not possible with other Wireless methods like Bluetooth now of course it is line of sight required which does limit its usefulness somewhat however it still brings to the table a lot of really interesting DIY audio product
opportunities the most exciting of which I think is a homemade wireless surround sound system this would eliminate the requirement of draping speaker wires all over the place the audio can instead be beamed straight to them wirelessly and as it's Optical it won't interfere with Wi-Fi signals or have any latency issues for making them while we could just strap receivers onto Old bookshelf speakers just like this I've been wanting to make a proper DIY surround sown system for literally years and I've come up with a design that strikes a really good balance between both perform performance
and price using some very interesting construction methods these construction methods rely on the use of 3D printing which is a fantastic way of building speakers at home because you simply don't need a workshop or any particular tools other than a 3D printer which are more common than ever these days in an effort to keep the overall cost in check the design is to be based around a quite remarkable speaker driver the Dayton AIO tcp15 this retails at just $13 at time of publication which is crazy good value considering that it can not only function as
a decent mid-tone driver but can also play well as a subwo of two which is why we'll need a pair of them one for each of these roles with these two functions in mind I've designed a speaker enclosure that is volumetrically optimized for this particular driver and the printable files have been made available in the video's description as you can see it's design features Hollow walls to reduce both filament use and print times and the idea is to fill them with a special mixture later to give them the mass that they need to become true
Hi-Fi class enclosures it's also been divided up into a few different parts to ensure compatibility with even fairly modest print bed sizes so this does mean that they need some assembly by screwing them together this is quite fitting because today's video is being sponsored by the LTT ratcheting screwdriver this is a tool that's had a lot of thought put into its design and you can tell it's been made by people who actually use screwdrivers a lot lot it features a finely tuned ratcheting mechanism with an extremely light back Force allowing for the ability to ratchet
Drive even small screws if you've never used a ratcheting screwdriver before they give you greater control as they allow you to tighten or untighten a screw without having to adjust your grid reducing fatigue and increasing speed this is hugely helpful whether you're building a PC repairing a coffee machine or building custom 3D printed speakers being a multi bit driver you can of course swap out the bits as needed and Stow them in the base of the ergonomic handle which provides storage for up to 12 bits great for keeping your most commonly used head types within
Arm's Reach as the shaft has a strong brooch magnet inside it as well the bits tightly snap into place and provide a nice pull on any screws that are magnetic it's an excellent driver and I'm pretty hooked if you'd like to get one for yourself visit LTT store.com or better yet follow my link in the description which will let them know that I sent you honestly this would make a fantastic Christmas gift for someone even if that someone is you so a big thank you to the LTT crew for sponsoring this project and let's get
back to building so as you just saw the first job is to screw the two main enclosure units together to make them a solid unit with two distinct compartments the bottom one being exclusively for a special subwofer system which requires a few extra printed parts to make it work the first being a custom coupler for the bottom using plenty of glue to make an airtight seal as well as an internal insert to divide the sub area in half and function as a flared exit Port which will reduce chuffing noises when the final system is operational
and you'll see how it all works in just a moment so with that done we can now divert our attention to the top compartment which forms the chamber for the midtone speaker driver where the hollow walls are ready for a special plaster of Paris mixture what makes this mixture special is simply the addition of some standard PVA glue to it which stops the plaster of Paris from having a ringing quality a bit like a teacup and it's a quick hack to make it suitable for using in speaker enclosures to give them the MK that they
need to sound great adding it can be quite a messy process if you're not careful but it's a lot of fun and it reminds me of school craft days making the walls This Way saves so much printer time without having to make any acoustical compromises and it's my favorite method of constructing Speakers by far adding acoustic foam to the inside walls is a good idea as well as it reduces internal sound Reflections and results in a noticeably cleaner sound quality especially when complemented with sheep's wool which you'll see me add later it's a good idea
to add this acoustic foam to the plaster of Paris filled back panel as well which can be used to seal up the unit nicely so with that we essentially have our finished speaker enclosure and we can start now thinking about the Aesthetics to hide the fact that it's been 3D printed Ed this is fairly easy to do any joints can be filled with normal decorators filler after which it can be thoroughly painted with plastic primer followed by a top coat of your choosing mine being a heavily textured aged iron effect specialty paint this makes them
look really cool and you wouldn't at all think they're 3D printed especially as they feel so solid thanks to the plaster of Paris so with the Aesthetics sorted at this point the speaker drivers themselves can find be added starting with the Tweeter which is for handling the high frequency notes that the mid-tone driver can't reproduce very well this can simply be solded up popped into its hole and then screwed in place this same process is required for the midtone driver and bass driver as well they just need to be solded up dropped into their holes
and screwed down now this is starting to look quite promising but to finish it off properly it really needs a front facade another job for the 3D printer some filling sand and painting later it too can be mounted to the unit hiding the speaker rims and screws and making it look very neat indeed especially considering how simple they are to actually construct for this bass driver to do its work properly though and reach notes as low as 35 htz its chamber needs to be hooked up to some tubes to create what's known as a transmission
line configuration now as these tubes are going to be quite visible it's worth going with some that are made from acrylic as it'll make them appear much less obtrusive in a room again plenty of glue needs to be used when attaching these to maintain that airtight seal as even the smallest Gap can adversely affect sound quality so that the sound waves travel down one tube and up the other essentially making a 2 m long transmission line they can be joined together at the bottom with a little end cap coupler which again has been 3D printed
this is what the flared exit Port is for by the way it Smooths out the transition for the air as it goes in and out of these tubes once the glue has finally cured you can see that while it can stand it is a bit wobbly but that's easily fixed by mounting it onto a wooden foot I thought that this bamboo chopping board would look quite nice but it really doesn't match the aesthetic so I may just paint over it with the textured paint at a later date either way though the unit itself looks visually
very smart the acrylic tubes do a great job of providing support without being obtrusive holding the speaker at a good listening height what's particularly cool is that they provide a function as well as the physical delay that they add to the Basse driver's rear sound waves converts them into being complimentary to its forward sound waves providing low frequency performance that doesn't feel like it should at all be possible given the size of the unit flat down to 35 HZ does approach dedicated subwofer territory after all now the idea is to make four of these units
for a surround sound setup two for the front and two for the rear but how are we going to focus our laser beams onto them so that they each receive their respective digital audio signal well this is where a fifth speaker can come into play you see a surround sound system usually relies on a center channel for dialogue and important sound cues so it's a perfect place from which we can propagate our laser signals from its design is very similar to our surround sound speakers consisting of multiple parts that can be mounted together with glue
and screw SCU one interesting difference however is that its entire perimeter walls are to be filled with our special plaster of Paris mixture as the whole unit will be dedicated to midtone use without its own built-in subwoofer this is because we're going to be sending these subwoofer frequencies to the two front surround sound speakers adjacent to it which is a really efficient way of mixing it into the track again after the usual finishing process this makes for quite a nice enclosure with the midtone driver taking center stage one thing though that you might be wondering
is where's the Tweeter well the idea is to have the Tweeter mounted to its own little chamber on top this isn't just an aesthetic choice although it does look pretty cool but it's primarily a decision to keep the Tweeter time aligned with the midtone driver you see on many Center channels the Tweeter sits between two mid-tone woofers not a problem if you're sitting directly in front of it but if anyone else is off axis they can be left in an interference trough where important vocal frequencies dip in volume significantly this happens because of the slight
horizontal distance between the Tweeter and woofers which means that the sound waves from them won't always land at The Listener at the same moment from an off-axis listening position causing them to cancel out this is why I've decided to have the Tweeter mounted above the midtone driver because it doesn't matter how far off axess you are the sound from either speaker will arrive at you at the same moment avoiding the interference trough so either way we have now got our Center Chan and it's time to add the laser distribution system to it so that we
can Beam audio to our surround sound speakers as you might expect this is going to be based entirely around some small cheap analog to digital SP diff toslink converters by soldering four of them up to a little terminal block we essentially have a 4channel laser distribution system with the lasers sitting snugly in the 3D print before we can mount it in place though we do need to do a bit of press work on the center channel you see these toss link converters don't do any amplification that needs to be handled by a separate amplifier the
one I have here can sit within the chamber on the back and be screwed in place and wired up to the speakers to ensure that each speaker receives only the frequencies that they're best at reproducing will be passing the signals through a little Digital Signal processor this will allow us to program different response curves and frequency shelves to optimize for each driver squeezing even more performance out of them this too can be mounted onto its own block next to the amplifier and wired up to it leaving one last area for the laser distribution block which
likewise can be mounted in place and wired up all of these wires and circuit boards do of course look quite messy but that's okay as the intention is to cover them up with some back panels as you can see all of the connectors for the signal inputs have been angled downwards and this saves a lot of space as the intention is to actually have this Center Channel speaker mounted on some wall brackets above a TV as this keeps it nicely out of the way far away from the floor in a good position to be heard
clearly plugging in its power we can see that the lasers are successfully firing at the ceiling now these upward firing lasers might seem like a bit of an odd design Choice seeing as we need the speakers around the room and not on the ceiling but the idea is to actually use some little articulating mirrors to bounce the L to where we need them these have been made from a few 3D printed parts and as they can be adjusted in rotation and mirror angle we can use them to direct the lasers wherever we want in a
room using more mirrors at the other end to bounce the lasers back down towards the speakers the beauty of this is that the lasers are kept out of the way along the ceiling so that their line of sight can never be broken by people walking in front of them nor any of the alignments Disturbed it's a set it and forget it configuration and it really is the only way that this wireless system makes any sense so now that we have our lasers dotted around the room to approximately where we want our speakers to be we
need to enable the speakers to be able to decode the audio signal contained within this of course is where the SPD toss link receivers come into play just like the Standalone bookshelf demonstration earlier instead of going directly to an amplifier though we'll be following the signal path with another Digital Signal processor so that we can make sure that each of the three drivers within the surround sound units can get an optimized audio signal which is particularly important for their built-in subwoofers a perfect spot to mount these is the rear chamber on the back where the
space for the same style of amplifier we used for the center channel just like there this Powers each driver independently receiving its input from the digital signal processor which as you can see has been mounted onto a back panel this allows the whole thing to be neatly closed up with the toss link receiver facing upwards on the back ready to receive its laser signal having already set these up our new wireless surround sound units can simply be slid in position so that the lasers hit the toss link receivers providing each one with lossless LaGree audio
that literally operates at light speed being powered speakers they do of course need to be plugged into a wall socket so they're not 100% Wireless but that's fine by me as there are usually plenty of these to choose from around a room now to get a surround sound signal to the center channel for it to then redistribute to the other speakers we're going to be using one of these little surround sound extraction boxes these are very low cost compared to a normal AV receiver so are a perfect choice that plays a part in keeping the
overall system cost down you can use them to extract uncompressed surround sound from an HDMI connection allowing the speakers to have uncompressed audio end to end which is pretty neat for a wireless system from my testing it performs brilliantly the audio is crisp and sharp and in sync with the TV's image and the base is Sublime the fact that each of the surround channels go down flat to 35 HZ without requiring a separate subwoofer makes the sound stage really enveloping and it's so cinematic and the surround sound effect you get from the rear channels at
the back of the room really contributes as well now the best bit is that using brand new parts this entire setup costs about the same as a mid-range sound bar which is incredibly good value for any surround sound speaker set yet alone one that works wirelessly with zero latency and no compression pretty cool now I can hear some of you saying that Matt humans can hear down to 20 HZ 35 HZ just isn't going to cut it for a cinematic experience well I've got you covered now this is somewhat experimental but according to my calculations
we can use a 3 m long PVC pipe to hit these load notes using another transmission line configuration now of course as this is so long we do need to trim it down into sections this makes its size much more manageable and to join it back up again we can simply use some more 3D printed Parts as the plan is to use two tcp15 drivers coupled together with it there'll be a lot of air movement to contend with so it too needs a flared exit port to reduce chuffing noises just like on the main surround
sound speakers now this is admittedly incredibly ugly which is why it's to be considered a bonus rather than a completed project item but as it's slim enough to slide behind a TV it can't be seen anyway so doesn't matter too much now the amplifier used in the center channel speaker has two spare channels so these can be used to power each individual driver with the appropriate subwoofer frequencies right now it's playing a 25 HZ test tone you probably need headphones to hear it at all but it's really deep it feels like there's a standing wave
from a car outside or something it's kind of crazy you can feel it in your chest that's wild we got slowman it was literally a childhood dream of mine to make a proper surround sound system so to have made one that sounds so good and works wirelessly using lasers is a pretty good feeling don't forget that if you'd like to build this set of these speakers for yourself you can find the printable files for them in the video's description along with a link to the LTT ratcheting screwdriver if you'd like to buy one to help
you construct them but other than that I'm Matt you've been watching DIY perks and I hope to see you next time goodbye for now
