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Old 08-20-2008, 06:26 AM
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Default DIY Speaker for Kama BayAMP

This project started out when our Japan office's sales manager had this problem about turning his stereo on every time he wanted to listen to his collection of mp3s as well as having it necessary for the PC to be in the same room with his stereo. He didn't want to compromise the quality much, but he still couldn't justify his situation for achieving such a simple task.

So, this is what we came up with.

You might have guessed it, but it can be used both internally and externally. The power IC inside is a digital chip designed by Yamaha, which goes by the part number

of YDA-138 (D-3). Although the amplifying method is called PWM digital ( which is not as digital as you might think ), but the input supports analog only.

Still, you might say, So whats it for? Does Scythe expect end users to buy speakers just for the amp? Does that even make sense?. Well, to be honest, nobody in Scythe knew what this thing really was. I mean we knew how to use it, I liked it, the Japan offices manager adored it, your trusty forum admin Shinigami seemed fond of it, but then still it also seemed that producing it was a bit of a long shot in means of PC accessories. But then, probably nobody else would be bold (or should I put it reckless) enough to show up with such a product which says in the middle or sort of all over its face...

So why did we do it? Well, it sure sounded nice for the cost, and at the end our thought was that since we are having so much fun with it, why should we think the others wont? Also it was that since we were quite successful with the other projects/products, we thought we just might treat ourselves with the realization of this product. I mean whats the use in establishing a company if you cant do wild products that we want at least from time to time? =P

Anyway, back when we had some time until CeBit Germany (2007) when the first prototype was done, I planned to build a set of speakers to run demos with the amplifier. The model done for CeBit had two satellite units with a subwoofer unit. The set did work well, and one guy ( yes your trusty forum admin Shinigami) seemed quite interested in what I did, so we talked a bit and came up with an idea to build a set of speakers for Computex Taipei that would also be a good beginner project for speaker DIY for him to do. Then after we were done with Computex he said, why not share the project with everybody in the forum? Well that sounded like a good idea since we could show at least a hint of why we enjoy the product ourselves oh so much.

So lets get cracking!
First you need to get your woods. If you talk about DIY speakers, woods are still the best material. Well let me put arguably there. You should notice that 99% of the (real) audio speakers, even a Behemoth priced/sized speaker set would be usually made of wood, so you need not at least question their credibility.

This speaker set is designed for a 8cm full range driver unit, Fostex FF85K. You can use other units that fits in size, but please note that it needs a very strong magnet. If the magnet is weak, this type of speaker will not work properly. Since the structure of this speaker is a 180cm pipe folded in half, if the magnet is weak, unit will not be able to drive the pipe and will not give you a clear sound. You might want to check the specs here.
Full Range : FF Series - Speaker Components

I recommend you get a hold of this unit if it's available at your region. There should be very few units this size that will be as good or better for this project. One issue there is to this unit is that it is not magnetically shielded. So if you have a good ol CRT in your what ever system, this might be a problem. Also you might have noticed that this unit is good up to 10W of music power. So is the Kamabay Amp. So might ask. Will it be loud enough? Well, the two combinations powered our Computex booth nicely and we never turned the volume any close to the limit. But I do believe there will be people who will experience the need of more power. But then again, you should have a big house with neighbors quite far away.

If you are interested in doing this build yourself, I believe Shinigami can ready a downloadable pdf drawing of the wood pices ready for your disposal.

I suggest you read this Sort of How To thoroughly before starting anything, since my document is written in order of my actual work, which does not always mean it is the best order to have it done in all circumstances.

Ill also encourage you to read other peoples How To for DIY speakers. Since this hobby has been around for quite a while from your grandfathers generation (It goes back to when theaters started to have sound.), there are lots and lots of documents and designs on internet for you to refer. Who knows? There might be one that you would drool for. Also if this is your first time working with woods, How To documents/articles on wood works for beginners should be helpful too.

Now on to the actual work.

If you had your wood cut at a shop and had it delivered like me, the next thing you need to make sure is not damage the wood while unpacking. Watch your knives so it wont cut into the wood while unwrapping.

Then stack up all the wood that is cut to the same shape. This is for checking if you got all the pieces. The wood panels with the round pieces fit inside are the panel that the speaker units will be attached to. The round pieces are just put back there to protect the hole from breaking while transportation.

Then also try putting all the woods together in place without nails or glue to see if all things fit as it should. This is for checking if your woods are cut in the correct sizes. This also lets you double check if everything is there. The small pieces on the left are the leftover bits and pieces from the wood sheet I had all the panels cut out from.

The dimensions of this speaker enclosures (for speakers you usually call them Cabinets) are approximately 120x225x900 (WxDxH) depending on the error margin (woods thickness and build). The aim of this design is, to save space, and achieve a wide range of frequency (relative to small speakers) with low cost. I don't have the exact figure here but the total cost should be maybe around 120 Euro or so. There are many woods to choose from and what kind of coloring, grades of connectors/wires, etc. so the real cost is rather fluid. I used a normal ply wood myself and since I had all the little things like glue wires and connectors at hand, my set cost me around 100 Euro.

The size might not be something you would call small, but since it's very slim it should have not much of a problem to fit into most people's room. You may think a set of speakers that are called bookshelf speakers (the smaller ones that actually fits into bookshelves and desktops) will be more space saving, but usually If you want a decent performance, you would need to set them on a decent set of speaker stands. Then it would suddenly turn a lot more expensive and not so much more space saving than this design.

All in all I believe this project to be fruitful for people that likes DIY and would want to taste something a bit more than multimedia speakers.

Now on to the assembling.

Use the speaker unit as a template to draw the screw holes locations.

Like so.

On the left are the included screws from the speaker unit, center is the type I plan to use, but I didn't have the right size in the toolbox for some reason. I plan to get them later. The thing on the right are screw hole threads inserts. I don't know the English word for it, but it's for hammering into a hole to provide steel threaded screw holes. I wanted to apply this since I plan to screw on/off the units a lot when tuning it after the assembly. It also gets the unit firmly mounted to the wood, hence improving sound quality to some degree. Though it's not a must, I recommend it if you won't mind bothering.

If I'm not wrong, this should be called a Gimlet in English right? Anyway, If you want to have the screw thread inserts, and only have a hand drill, I suggest you use this instrument before you use your hand drill. You can place your holes more precisely. If you plan to use the included screws, you only need to use the Gimlet. Having a small hole, even a shallow one opened in advance will make it easier for you to screw in with your screw driver. It will also help mount the unit straight.

Excuse me with the crappy photos. Since this screw thread insert is about 4.5mm, I plan to open a 4mm diameter hole. A bit tight so it will stay there and won't fall out.

The holes are done. I plan to have the inserts go in after the enclosure is assembled. Next, I want to shave off a bit of the edges off the speaker unit's hole on the inside. This is because since the FF85K has a very huge magnet compared to it's overall size, there are very less space for the speaker unit to breathe. Sound is produced by moving air, so you would want the speaker unit to freely do the breathing. But I dont want to shave off too much since then it would make the structure weaker. I used a grinding drill bit for this, but you can use normal files for woods also. By the way, this drill bit is for carving steel. I had one that said it was for wood, but this one works a lot better.

Here is before shaving off the edge. The lines forming a rectangular shape at the center bottom side of the unit are for the connectors' clearance. The pencil drawing is a reference guide on where till should be shaved off.

The shaving off done. You can clearly see that there is more breathing space for the unit. You can also see that the connectors are visible now. It might take a bit more time, but please consider this part important.

Always use pencils (mechanical ones are fine) to mark your wood. Don't use pens since you won't be able to erase after you don't want them there. It is important to keep it air tight where it should be, so take your time and get the centers and edges to match right.

Make sure you always use glue in combination of whichever method you use to stick the woods together. Nails and screws are Godly with woods, but since you need to have the structure airtight where it should be, you will always need glue. This photo is of what you call a PVA glue which is known commonly as wood working glue, which also is the same thing you used to glue crafts back in Kindergarten. You may think this is not a good glue, but if you speak of putting woods together, it is very powerful. If you try tear down a PVC glued wood work, the chances are that the glued part will be more durable than the other parts of the craft. Also since this glue takes a while to dry, you will have plenty of time to check and correct your errors.

Don't forget to ready an immediate source of water available with a towel. You'd need them to wipe off the excess glue. If you don't wipe it off, you will have a hard time sanding or carving it off. Also paints and coatings don't agree with them, so if you want to color/coat it nice, be sure to wipe them off thoroughly.

This time I won't use any nails but just glues and clamps. The photo shows you the two woods right behind the piece you mount the speaker unit(s) being glued together. You can check the earlier photo where I just placed the woods together.

See how the excess glue is wiped off. This will be the inside, so it doesn't have much to do with the finish which means it isn't really necessary here, but I did it just because I could.

I forgot to show you a reference of how much glue you should use so here it is. This will be the gluing of the front panel and the two woods I just glued in the above photo. Actually the idea about gluing wood is as same as how you should place thermal paste on your CPU for a cooler. The method is _not_ the point, but the result is. You need it to be so that the glue will be between the two woods, with no air in between. Ideally the woods should contact directly to each other as much as possible, and the glue should just fill in the microscopic gaps of the two woods. But that's ideally. Woods bends on their own by the change of moisture, temperature and such, so no air in between, together and close to each other as possible is what we should go for.

You can see the clamping is pushing out some glue from the two woods' gap. If you use nails, you should nail them from the inside in order to hide them for this section.

Don't forget to wipe the glue off here too. You'll have a hard time gluing the side panels if it's not flat, so it'd be wise and less time consuming if you wipe them off at this stage.

Next goes on the bottom panel. It isn't a must to assemble in order as I did. You can do how you feel is comfortable. Just make sure you do it in an order that allows you to assemble till the end.

Here goes the center wood. This is about it for the front side structure, so I'll do some small things to ready assembling the rear side.

Yeeeess..., my crappy photos and me. The gold thingie is the connectors for the speakers. They are called speaker terminals. I guess that means originally they were meant to connect several wires and speaker units instead of one to one. There are various types, but I suggest you use these screw on types. Theyre highly durable, and gets your cable connected firmly. The cable contact affects sound quality, so please consider this choice quite important. Many of these screw on types are expensive, but there are reasonably priced ones if you look for them. Make sure the main shaft is long enough and will allow you to use a 15mm wood. Measure the screw shaft diameter and choose your drill bit size. I used a drill bit 0.5mm smaller than the measurement like the thread inserts so the fit will be tight.

Good thing I wasn't hired to do packages. Seems my ability for photos are very limited. Anyway, the holes for the terminals. It's located on the top rear side of the speakers for me. You can have it where you want it as long as it can be accessed from the outside and does not prevent the cabinet from standing. Don't forget to draw the location with your pencil and to use the gimlet before the drills.

Here goes the top panel and rear panel together.

Then goes the rear vertical piece.

The front and the rear side are assembled together here. The difficult part of the assembling is all over.

Just the side panels left to go. And nope, Gordon Freeman didn't pay me a visit.
Now you can see the structure of the speakers. The design is a pipe folded in half. The lower rear side has an opening, which gives you the extra bass. To be honest, the wood amount and reinforcement structure for this design is a bit of an overkill. But since this was an experiment, I thought why not use all the wood I could with the 1820x910mm standard wood sheet size we have here in Japan.

If you want to have your terminals (connectors) where I put, you need them on and wired before you close the structure with the side panels. The speaker unit hole on with this design should be too small for two hands to go in. I can have one of my hands to go in, but there is not enough room inside to move them much, let alone enough to do any soldering.

Looks nice right? It's a no-brand stuff though. Quite reasonably priced and does a good job fastening the cables. Actually it looks identical as the bay amplifier's terminal. Strangely it was just a coincidence.

Now for the wires. This is a Belden 83029. Belden is a German company by the way. It is an AWG18 (American Wire Gauge) OFC (Oxygen Free Copper) wire with teflon coating. Good stuff. JFYI, the AWG18 part stands for the thickness of the wire. If you check some of the cables inside your PC such as fan cables and PSU cables, you should see the AWGxx printed on them.

The strips I cut is about 45cm in length. Bit long for the short distance, but I want to use these speakers for experiments, so I made it long in order to have the speaker units easy to exchange in case I blow the unit up not just for once but several times. Now, there is only two speaker units, but I got 8 wires. This is because I wanted to do double wirings from the terminals to the speaker units.

You can see the double wirings here. The reason for this is that thicker the wire is, less electrical resistance you have, for the audio signals. But then if you have the wires too thick, it would not mechanically fit in. So in order to satisfy the electrical characteristics as well as the mechanical restrictions, I used a good low resistance wire that's slim enough to fit and had them double wired.

This is not a good picture in terms of finished soldering actually. This is a mid way photo and I don't know why I only had this taken. Anyway, please note that I soldered the bolt and nuts together with the wire. This is to never get the nuts loose, and also for the cables to have a better electrical contact with the terminal. Not necessary, but better than not doing. I'll show a better soldering result for your reference with the speaker units later.

Now to the side panel assembly.

The panels on both sides being clamped at once. Note that you need to have the glue dry enough to move around the speakers without the first glued piece shifting from position. I waited for about 15 to 20 minutes before I went from the first panel to the panel on the other side. Also the clamping should be done after it's half way dried to prevent the panels from sliding while adding pressure.

Here is the whole box in view. You can see the side panels on this enclosure is a bit sticking out on the front side. Since woods bends with temperature and moisture change in the air, there is always a chance that your woods may not fit perfectly. Especially since I left the cut wood for nearly two months, I couldn't completely get rid of the bends. These side panels should be shaved off with a plane to match the front panel.

Speaking of planes, I readied this special plane to shave off the corner of the front panel at a 45 degree angle for this design.

There. Left is before, and right is after.

Generally, modern speakers are becoming more slim than older designs. That's because you will have a better sound stage if the box is slimmer, which is by having less reflection from the front panel. This design is slim already to start with, but giving the edges an angle makes the front panel virtually slimmer in terms of reflection. This part of the work is for experimental reasons, and it is not a must. The bit dark color on the shaved off corner you see now is epoxy putty to smoothen the surface. I need to sand them off later.

Now hammering in the steel screw thread piece. Use a piece of wood between the hammer to hit the steel piece in. This should prevent the hammer from damaging the wood surface of the speakers. Also you can se the epoxy putty has been sanded off here.

You can recognize the steel thread pieces inside here. The unit's hole seems to match fine too.

Now to the painting/coloring. To save labor of scraping the paint off the terminals afterwards, I masked them with pieces of tape. Usually you should use what you call a masking tape, but I used something at hand. Also note that you should do some sanding (apply sandpaper) to smoothen the surface a bit before painting. There should be many DIY web pages on woodwork, so I'll leave those details to the experts to explain.

Here is what I used to color my speakers. It says Bokuteki on the bottle but I believe the more popular name for it in Japanese is Bokujyuu. It's the ink you use to write Kanji letters with a brush. The base ingredient is said to be either carbon made by burning pine tree roots, or what you call Lamp Black.

Here is the result of the coloring. Since it's a water based color, I plan to coat it next. The reason I painted it black is because Mick Jagger said so. Well no. Actually there are several reasons. One major reason is to make it good for projectors. If it's not a dark color, it gives too much attention in the dark by reflections from the screen onto the speakers. Other reasons are to make it look modern, and experiment an easy way to paint dark colors. This is since many people seems to not like the retro look which most DIY speakers has as well as the look of the wood, so I was wondering if there could be an easy way to give a modern appearance.

This is a Watco oil stain Watco is a British company so some people might be familiar with them. I plan a thick layer of this to make the color water proof.

If you plan to use their product, I suggest reading the instructions on the cans thoroughly. Bit complicated, but worth applying. The drying time is pretty long though. I did about 3 or 4 layers with the bokuteki and it took me about 2 - 3 days, but it took me another week with this oil stain for 3 layers. I'm planning to add more layers afterwards. This is dried only mid way.

I'll stop the oil staining for now. It's hard to tell by the photo, but the black has more of a wet shiny texture now. To be honest, the results are fine but I don't know how I'm going to repair it when if the surface is damaged. The oil stain also works as a coating from filth, so the Bokujyuu coloring is not possible to be applied afterwards. I do have another idea regarding this issue, so I'll try that maybe the next time.

I missed to mention about the solder itself but I used an audio grade non-leaded silver and copper mixed solder. Solder affects the sound quality greatly, so I recommend using a good solder. The blue de-soler braid is what you use to remove solder. It works like a towel absorbing moisture, but as you might have guessed, you need to have the solder in a liquid (molten) state for it to work.

Here is the result of de-soldering on the right side terminal. You can see the wire leading to the speaker cone showing from that little square hole there. The brown thing is solder flux. Flux is the name for the glue that's inside the solder.

This is after I removed the solder and had it re-soldered with the audio grade solder. The FF85K speaker unit is not actually a super high grade model (it is pretty much an impressive model for its price though), so I wanted to exchange the solder for extra juice if I could get any. Be careful to not unwire the copper cable thats running from the soldering point to the paper cone. Thats where the signal goes so it needs to keep contact there. Yeah, its obvious, but just incase.

And some more soldering. Check that the wirings shows strands of thin wires while they are covered with solder on the surface. This means the solder has soaked into the wire nicely and has maximum mechanical/electrical contact. It is not bad to have extra amounts of solder on the wire though. Sometimes you put extra solder on to gain mechanical strength. What you dont want to have is the solder to not soak in to the wire. This likely happens if you fail to raise the temperature of the two soldering points (the terminals and wires in this case). If this happens, the solder will melt, but will not connect the two together as it should. There should be soldering tips on many DIY websites also, so I recommend checking them if you are interested.
You can also see a bit of the reflection from the oil stained wood surface here. I didnt want it to become too shiny and reflective since that will also be not good for projectors.

The rear view.

I used my mp3 player for a quick test. The bass reproduction is pretty good for this size. I believe many people will squint their eyes and look for a subwoofer if they see/hear this system playing. But then a subwoofer to match this system would definitely improve the overall quality. By the way, I do have a dedicated room for audio with equipments rather on the high end side, but I wouldnt be that upset if I needed to get rid of them and stick with this sets here With a bit more tuning.

So to the tuning (damping).

Actually building the wood structure and painting it is like 60% of the whole job. Having the damping (stuffing the fluff) done is what you need to do to complete the craft. If this was a normal speaker box, all you need is to do by the books, but since there are many variations and unclear variables for a quarter wave tube design (which this speaker design falls into), the whole procedure will be cut and try.

Arguably these types of speakers are known to produce low frequencies most efficiently, but it does have a few drawbacks. One of them is that since the opening of the pipe is fairly large, all the sound from the rear of the speaker unit will come out including the frequencies that you don't want. Also there will be a lot of standing waves going on inside. When these all comes out without any filtering and mixes with the sound from the front side, the result is a foggy and boomy sound. So comes the necessity of damping. But keep in mind that you wouldn't want to damp it too much. That will even kill the frequencies you want it to come out. Also do not plug the pipe structure with your damping material. A similar design I did before had better results with plugging the pipe structure a bit, but this one is better if you leave it open.

Now about the actual work.

The white fluff you see inside are used as sound absorbing materials. Actually these you see inside are sold as kitchen exhaust fan filters. Though this picture may look like chaos, the filters are rolled into pipes to fit the wooden pipe structures so it does not get in the way of the wooden pipe structure to function. The materials are in both front and rear side of the pipe structures all the way. I would glue to the inside walls while in building if I were to build the same design again ( Which I likely wont. ).

Here's the bottom rear side with the damping material.
As explained above the white material you see at this side goes all the way to where you could see in the first photo. The black fluff that's covering the inside walls are felt. The small strip is to cover up the white fluff as below. The white fluff is sticking out because it simply sounded better that way.

Initially, I did a few weeks of cut and try with this. After that I left it as it was and used it on daily basis for about a month. Then I changed the fluff stuffed as here you see in the photo, so this tuning took the most time than the build. I started out from less material to more since too much will spoil the merit of this design. You can use the human voice and the bass as a reference. If you hear the vocals sound as if someone was speaking/singing into a pipe, you need more. If you hear too less bass that means you are putting in too much. Try distribute the materials evenly so it will not plug up the pipe structure. If you don't want so much bass is the case, you might want to plug the pipe deliberately at the open end in the rear.

Anyway, the final result of all the tuning was pretty much satisfying for me and it won the position as the reference speaker system for my PC.

Here is the whole view of the finished speakers. Well, I mean I have the screws I wanted compared to the earlier photo.

Generally the sound quality will improve over time ( possibly up to 6 to 12months ) by brake-in, which means the speakers will mature in time and in use. This is caused by the woods forced into the form of the enclosure from it's natural bends and other materials maturing in time. Also the speaker unit itself improves sound by break-in. The idea is the same as burn in, but only in a bit more of a long term.

Now as all crafts are, this is not for everybody. As matter of a fact, after this document was done, we even found out that recently there are affordable and nice looking speakers available in the shops more than ever before. Seems that the multi channel requirement for home theaters brought up the necessity of low priced decent speakers. I cannot be sure about all of them, but I am sure that there are many ambitious models with aggressive pricings out there. So I guess it all burns down to if you want to get your hands and knees dirty in search of getting a customized satisfactory result. Just like PC DIY.

But then again, either way, Kamabay Amplifer will be your good friend. =)
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