This pair of Serious Speakers is the result of my year-and-a-half rollercoaster project Designing loudspeakers by trial and error.

In this Instructable you will find everything you need to make the Serious Speakers that are now in my living room and that I enjoy everyday.

The budget for these speakers is around €250 / US$300. I noticed the Visaton drivers I use (German made) are more expensive in the US than in Europe. DROK has a comparable driver model that is cheaper in the US than the Visaton FR10. See step 2 for that.

Making the speakers is not very easy. During the design process, I found that "skewed cabinets" (with only non-parallel planes) sound much better than regular right-angled boxes. The price you pay for this is a more complicated geometry and more demanding, precise working. But with the right tools (table saw!), some practice and patience, it really can be done. The cabinets I made are certainly not perfect, but they do sound good.

The drawings I made (step 4) are a little different from my own cabinets. That is to say, the geometry of the inside of the cabinets is exactly the same, but I reduced the number of panels from 10 to 8. This saves some time sawing, but more importantly it makes it a lot easer to assemble, glue and clamp the cabinets. I wish I had thought of that before writing this Instructable :)

Before you run to the store or hit the Amazon buy-button, have a look at the next step in which I describe, as well as I can, what my Serious Speakers sound like. If you're a hip-hop fan with a 90m2 (1000 sq. ft) living room, these speakers are not what you're looking for. If you listen to pop, blues, jazz and country and have a more modest living room, you might be in for a nice surprise.

Step 1: Sound Quality

In the pics you can see a home-made, almost serious graph in which I placed my speakers on the axes of costs vs audio-quality. Considering the costs of US$ 300 for the pair, I believe my speakers are pretty good. In the graph, this is somewhere between "decent" and "fine" and closer to "cheap" than "not cheap".

I compared my speakers with quite a few others, from common off-the-shelf 2-way and 3-way speakers to high-end beauties made by experienced builders with budgets ranging from €1000 to €5000 and up. My speakers easily beat the regular commercial models up to €500 for a pair. They can't beat the €1000,- experienced builder types. Those have more sound pressure, lower bass and easier highs.

Yes, but how do they sound?

The speakers are at best in the midrange. Vocals, piano, guitar, horns, etc come out really, really nice. (Watching and listening to movies is a real treat, because the speakers are so good at the vocals.)
The "soundstage" is pretty good. That means the stereo image is clear and different instruments can be distinguished easily.
The high notes are nice, but not spectacular. All tweeters have a tendency to "chirp", and so has the DT94 I use.
The bass is pretty good considering the small drivers. Bass sounds punchy, not boomy. Low notes are there from about 60 Hz and up (according to acoustic calculators, the cabinets are tuned at 56 Hz with the -3dB frequency at 43 Hz). I spent a lot of time optimising the bass by experimenting with volume, tube lengths and the crossover.
The sound pressure is not very good. The speakers have trouble filling a large room with music. For me, that's not a problem because my living is small and the speakers are about 2.5 meters away from my couch.

(Before you ask: An audio sample of my speakers makes no sense here. You would be listening to my speakers through your own speakers. The only way to listen to my speakers is to pay them a visit in person. Most of you would have to make the detour of a lifetime, because I live in The Netherlands, where people speak Dutch (Frank Zappa mastered one word in Dutch: Vloerbedekking. It means carpet.))

Step 2: Materials Needed

To make one loudspeaker, you need

For one cabinet:

- 18mm MDF of birch plywood, half of a 122 x 244 cm sheet.

- about 0.5 m2 of wool carpet (I got a sample for free from a local carpet store)

- 4x straight PVC tube connectors for 50mm diameter PVC tubes

- 50 cm PVC tube, 50mm diameter

- Filling for the cabinet: From a pillow, audio grade PolyFill or sheep wool.

- A set of loudspeaker spikes

Drivers:

- 4x Visaton FR10 8 Ohm full range drivers

- Instead of the Visatons, you can consider 4 DROK 4" full range drivers. It saves you money when you buy from the US. Disclaimer: I've never listened to the Dayton drivers, but the specs match the Visaton drivers.

- 1x Visaton DT94 tweeter

- About 10 meters (30ft.) of 1.5mm2 speaker cable (12-16 AWG)

Crossover components:

- 1x Visaton HW2 / 70 NG two way crossover @3000Hz / 8 Ohm

- 1x 3.3mH / 1.0 Ohm Visaton air core coil

- 1x 30uF bipolar capacitor or MKT capacitor

- 3x 10 Watt resistors: 30 Ohm, 8.2 Ohm, 4.7 Ohm

Step 3: Tools Needed

Tools for woodwork / cabinet making:

- Table saw (or look for a Maker Space in your area. Maker Spaces have table saws :) )

- Clamps in different sizes (the biggest you need is 1000 mm)

- A router to sink the tweeter into the front panel.

- Hole saws: 51 mm (for the tubes), 68 mm (tweeter), 102 mm (FR10 drivers). If you are comfortable with a router, you might not need hole saws.

- Bison Polymax kit

- Wood glue

For assembling and tweaking the crossover:

- Wire connectors

- Small screwdriver

- Soldering station and solder

- 1.5mm2 / 15 Gauge speaker wire (leftovers)

Tips and tricks to building loudspeaker cabinets:

- Noahw's classic Instructable on loudspeaker building

- MatthewM's Instructable guide for a first class build

On the use of tools:

- tashiandmo's Instructable on Making small holes with a router

Step 4: Building Plans, Making Panels

Although I simplified the cabinet design, you still need to saw no less than 8 panels per speaker. Six of the panels have edges that are mitred in uncommon angles (12°). Take a look at the pics for a composition of the different panels and for drawings of each panel.

There are some tips and remarks within the pictures of the cabinet.

Especially the back panels (E & F) are tricky to saw, because the two long edges are slanted and mitred. The easiest way to make the back panels fit as well as possible is to build the rest of the cabinet first. Then take measurements of the back side of the cabinet and saw the back panels individually.

(I made the back panels up front and regretted that choice. I had a hard time fitting the back panels in the cabinet, and I'm still not very satisfied with the result).

Take your time making the baffle. Laying out the nine holes, sawing the holes, trimming the tweeter hole with a router, it all takes time and patience. Don't rush!

Glue the bass reflex ports (50mm PVC tubes, 11 cm long) in the back of the baffle before assembling the cabinet. I used Bison Polymax to fix the tubes airtight into the holes.

Step 5: Building the Cabinet

Although tricky, it doesn't take a lot of time to assemble and glue the cabinets. What you do need is a set of decent clamps, though.

Put the baffle (front) upside down on a flat worksheet and place the side panels on the backside of the baffle. Thanks to the mitered edges, the panels lean inwards and nicely support each other.

Put glue on the edges of all upstanding panels and the on the baffle's backside. Then place the panels in position.

Place the first clamp over panels C & D. I made a set of slanted (12°) blocks to go between the clamps' pads and the cabinet (see the picture).

The second (widest) clamp goes across the length of the cabinet, pushing top and bottom panel inwards. Again, put a slanted block between the clamp and the panels.

With the two clamps in place, the panels are now fixed. I put some weight over the side panels to push them against the underlying front panel.

I used Pattex fast hardening wood glue to assemble the cabinets.

Step 6: Lining, Mounting Speakers, Wiring

This is one of the most rewarding steps :) Once the entire cabinet is there, except for the back panels, the drivers can be mounted into the holes.

But first, you have some carpeting to do. Line the bottom and top inside the cabinet with wool carpet, as you can see in the first and second picture. Carpet can be fixed with double sided carpeting tape, but I used Polyfix in the end. The double-sided tape I used just wasn't strong enough to keep the heavy wool carpet in place upside down.

I also clad the inside of the back-panels with wool carpet.

Wiring and mounting the speakers

- Start with wiring the speakers. I soldered the speaker wires directly to the drivers' connectors, but I wouldn't do that again. In hindsight, I would use push-on terminals as in one of the pictures. It makes repairs or re-wiring a lot easier. Besides, soldering 15 gauge copper wire to the small terminals is not easy.

- Attach about one meter (3 feet) of speaker wire to each driver. Drill five holes in the back panel just large enough to push the wires through. I didn't exactly do this. Instead, I connected the drivers that are linked in series on the inside of the cabinet. That way, only three wires come out of the cabinets' backside. The big disadvantage of this is that I now have to open my cabinets if I want to reconfigure the drivers.

- Pre-drill the holes for the drivers' screws. Be careful not to drill through the baffle. A 1 cm deep hole is fine.

- Gently fix the wired drivers into the holes with screws. Screws should be tight, but not so tight that the screws strain the drivers' frames.

- Fill the two compartments with pillow filling or sheep wool, but not too much. Keep the filling away from the opening of the ports. You might want to experiment with the amount of filling. When your speakers sound muffled, you've overdone the filling. When the speakers sound shrill, you should add some filling.

- Finally, put the backside panels in place. I used screws to fix them into place.

Step 7: Crossover, Filters and Finishing Up.

I love crossovers :). The parts and circuits are simple, yet their working is subtle. I bought ready-made crossovers from Visaton and added some filtering. The circuit is in the first picture.

The Visaton crossover can easily be build without a PCB. Most DIY loudspeaker enthusiasts just buy the parts and mount those on a woorden board, separate from the cabinet.

Connecting the drivers to the crossover is not hard. Just keep a good eye on which wire to connect to what part. I labeled the wires coming from the cabinet (W+ for the plus-side of the woofer, etc.)

I mounted the filtering parts on the back of my speakers, using electric wire connectors to connect the parts, causing a spaghetti incident of wires, parts and protruding terminals. It is only now that I understand why the experienced builders use separate boards for mounting the crossover parts :).

And now...

You can finally test your speakers! Actually hear them playing music :)

Don't panic when you hear nothing or only half of the drivers. It is easy to make mistakes when connecting the drivers to the crossover. Just check your wiring and connections again. The beauty of loudspeakers is in their simplicity. It's only a few parts, so you're bound to find mistakes.

Finishing off the exterior of the speakers might be the hardest part. I want to paint my cabinets with transparent floor lacquer, but haven't found the time to do that yet.