Introduction and design

The speaker that started it all. In Januari 2001 I was reading an article in Speaker Builder magazine about the Aria 5r speaker. This is a bass reflex speaker, with two Focal 5inch 5K4211 mid/woofers and a Raven R1.0 ribbon tweeter in D'Appolito configuration.

I had bought some year-sets of back issues of Speaker Builder magazines, because in late 2000 I had gotten interested in building my own set of speakers. I did not want to design my own speakers, because that is very complex, and building a set of speakers to an existing design seemed a much better idea. In contrast to other speakers featured in Speaker Builder, the Aria 5R was reviewed quite favorably, and especially the tweeter was very appreciated by the people that had listened to this speaker.

So, I thought, this will become the speaker that will be my first venture into DIY-speakerbuilding. I reread the article and the remark that the speaker was I little light on bass attracted my attention. Indeed, these two small woofers, seemed just a little TOO small to produce real bass.

That would be a problem, since a lot of the music that I listen to has got a rich bass content, and I was looking for a speaker that could reproduce that part of the music convincingly.

So, I thought, maybe I should change the design to having two Focal 7inch woofers. That shouldn't be too difficult, since the Orcadesign website (the home of the Aria 5R), already has some designs with this arrangement.

Focal is readily available in the Netherlands, the Raven tweeters aren't. I bought the Raven tweeters online, from E-speakers, and they arrived within a week! For the woofers, I went to Speakerland. I explained my plans, and told that I thought that two Focals 7k4411 per speaker would get the job done. Ruud -the shop-owner- gave me his famous: "well, that's ok, but if you really want something that works well", go for the Scan Speak 18w/8546. Of course I knew the Scan Speaks, but I thought using Focal drivers would work better, because that wouldn't deviate too much from the original design. But I let Ruud convince me otherwise, and went for the Scan Speak units.

Well, so even with my best intentions, I ended up not building something after an existing design, but creating my own speakers. The only thing my new speakers would have in common with the Aria 5, was the Raven R1.0. But since I can count on some help from more experienced people, I hope this won't be to big of a problem.

Ruud did some simulating on a vented enclosure and advised me to go for a box-volume of about 40 litres. I went home, with two woofers (the Scan-Speaks cost double the price of the Focals, so I bought half of what I needed) and started drawing. And this is what I came up with:

This drawing shows some extra detail. My CAD-skills aren't the best around, so I figured that some extra info wouldn't hurt. I'm convinced that making a drawing of the speaker -especially when it's a more complicated design, or your first...- is important. It really makes you think about how it is to be put together. This helps to prevent problems further on in the process.Click on the image above for a vector graphic.

The speaker is built from panels of 22mm MDF and 18mm Birch plywood glued together. Several people have told me that making speakers from two materials glued together would help in eliminating resonances. I did not want a black speaker, but one with a nice wood-finish. I made the Birch plywood the outer layer so that would give me a nice finish and eliminate the need to veneer the speaker later on. If only I had known that birch plywood is available in different qualities, I would have looked for a better quality. The sheets that I bought had several oval repair pieces in them and were also rather rough, which ment a lot of sanding later on. That's something to keep in mind for the next project.

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Construction

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I started construction by sawing the boards of MDF and Birch plywood to usuable pieces. For this I used a hand circle saw, for two reasons. Although I have access (my dad has a great collection of powertools) to a table saw, this table saw was abused for cutting firewood. Which is a shame because it's very good one, with a sliding table mounted to it for easier ripping. Second reason: Table circular saws scare the h*ll out of me!! I personally know three people, who after a careeer of tens of years (My uncle who owns a sawing mill, my neighbor who has a kitchenbusiness, and a friend of the family who has owned a table saw for decades) have cut off several fingers with one. I don't get near one, if I don't have to! Since a hand held one needs to be handled with two hands, I think it's safer. The result of a days worth of sawing (one obvious disadavantage, besides accuracy, is that a hand held circular saw is way slower) is a nice stack of panels.

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Next, I made a mould out of a 9mm thick piece of mdf for the front baffle. I used my my new router for this, together with the circle jig. I thought that would be the difficult part, but making the square cutout for the Raven proved to be quite a challenge. I asked some advice from my neighbor, the one who owns the kitchenbusiness, and he gave me the tip to screw 4 small battens on the mould and use them as a guide for the router, after cutting a rough hole with the jigsaw. Further on, you can see a picture of how I used this technique to make a cutout in the side panel.

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On this image, you can see a few steps in the construction process together. I have made the baffle using the mould of the previous image. I glued together the two panels of MDF and Birch plywood. I also made a bevel in the cutouts for the woofers in the MDF panel. This was done because the front baffle in total is 40mm thick, if I had made a circular cutout, the woofer would be mounted in a small tube with only a small opening to vent the backwave of the woofer. The magnet of the woofer would have almost plugged this tunnel, the bevel makes sure that this does not happen. I have also already mounted the threaded nuts in the MDF, which will later be used for the screws that hold the woofer. The clamps you see are for the glueing of the small panels that make the narrowing in the frontbaffle.

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Here you can see the resulting baffle from the back. The three small pieces of birch plywood are in place. The MDF panel already has a cutout for this narrowing, the birch panel hasn't. In this image you can also see that I used T-nuts to mount the Raven tweeter.

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A close up of the narrowing. I first used the jigsaw to make a rough cutout. I then used the the three panels, using the "valley" as a guide for the template bit to finish off the edge. Also visible are the countersinks for the drivers. I made the using the same mould, but mounting different seized guide bushings on the base of the router. The large guiding bushing (or ring) was for routing the hole through the panels, the smaller one (with the router depth set to 5mm) made the countersink. I had some luck with the countersink for the Raven. In my set of routerbits is a 12mm bit, which is just right for the corners of the Raven countersink, so no extra work was needed there!

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Here I glued on the two panels that create the sub-enclosure for the tweeter.

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When I started on this little adventure, I was convinced that making the circular cutout for the woofers would be the most difficult to get right. Well, I was wrong. Making circles is relatively easy. When you need two identical baffles, you simply make a mould from a €1 piece of MDF, using the circle jig for the router. Within 5 minutes you can have a perfect round circle, of exactly (within 0,5mm) the right diameter, and in exactly (again, within 0,5mm) the right place. Making square cutouts in the right place, perfectly squared and of the right size turned out to be the biggest challenge for me. This little trick I learned from my neighbor and was also used to make the cutout for the tweeter. How does it work? Well, pretty simple actually. I wouldn't have thought that it could be done so easy, after spending nearly a day fiddling around with a jigsaw and a ruler! Just mark where you want the cutout to be on the panel. You then mount small battens exactly on these markings. That needs to be done meticilously and is the difficult part of the operation. You then make a rough cutout with the jigsaw, sawing as close to the battens as possible. Then you take your router and with the template bit, using the battens as a guide, you can remove the remaining edge. This will leave a small edge in the corners, but for this five minutes with a chisel is all you need.

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I used plenty of clamps to hold the front and side of the speaker in place when the glue settled. I also made an extra jig to apply extra pressure on the small panels of the narrowing, to make sure they were glued airtight. I used the panel that will become the top of the speaker to make sure that the two panels were mounted square. After the glue had set, it turned out that this worked.

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Here the backside of the subenclosure for the tweeter is glued in place. Now the Raven has it's own little airtight home in the cabinet. Free from the pressure waves produced by the Scan Speaks.

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Halfway through the construction! I made them pose for the camera, so we can see what´s inside the speakers. The ports are in the picture just for show, They were delivered just that morning. As you can see, the side of the speaker has gotten it´s extra layer of MDF. The subenclosure for the tweeter is finished, and the hole for the port in the backpanel has been made.

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The black sheets are leadbitumen. It looks like roofing material, but it has a peel off glue back. I heated it on this small stove, but later that day I discoverd that simply laying this stuff in the sun worked much better, even when it was only 15ºC outside. I heated it, so it would stick better. And it bonded so well on the MDF, that when I had to remove a sheet, I had to use a chisel and a small layer of MDF simply came off with it!

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This is the is inside of the speaker-to-be. On the left you can see it lined with leadbitumen. Visible on the close up are the staples that I used to secure the corners of the sheets of leadbitumen. They aren't necessary, the sheets stick well enough from themselves. They're just there for an extra feel good factor. In the image on the right it has an added layer of pritex. Pritex is the standing wave reducing liner recommended by speakerland for bass reflex boxes. The image on the left is a little small to see what leadbitumen looks like, so when you click on it, you will get a close up.

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I forgot to take pictures of the final assembly of the speakers. But that looked just like the other "clamping pictures", so you're not missing much. On these pictures you can see that I've started on the finish. The one on the left has had a run with the round-over bit, and has been sanded. And oh boy, did that need a lot of energy. Next time, I'm buying the best grade of birch ply I can find!! The one I bought, had a real rough finish, that had to be sanded away, it needed six grades of sandpaper. I started with 80 grit, followed by 100, 120, 150, 180 and finally 240. But when the sanding was done, they felt like a baby's butt! I asked everyone that came to see the speakers to feel them. They thought I was mad, but when they did, they just couldn't stop rubbing them.

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Here's a close up of the narrowing in the speaker. The one on the left has a small bevel on the cutout in the side and the inside has been sanded. The round-over of the side of the speaker is clearly visible. Click on the image to get a better look on how much needs to be done on the speaker on the right.

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And here they are, in full glory. The one on the left is ready to be painted, the one on the right isn't. Clearly visible is the nice birch plywood wood structure in the left speaker, that is missing in the speaker on the right, which has to be sanded.

Pictures

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Destruction

As you can read on the page about my monitorspeakers, there isn't any space for these large speakers in my new (and much smaller) room. So that's why I designed smaller speakers. But that left me with a pair of finished, large and heavy cabinets.

What to do with these? Store them? Nope, too large, and besides: By the time I have enough space for them, I will want to build a new pair. Sell them, or give them away? No, if I can't have them, no one can. Well, only one option left: throw them away. To be sure, that they're unusuable, I ripped them apart, which wasn't easy!

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A speaker and main tool of destruction

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The side panel would only come loose after putting full force on the jack, and a firm whack with a large hammer.

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After that, the rest was easy