First off, I'd like to say that these speakers are dedicated to my Grandfather who used to always hide his speakers in drawers or behind his furniture.
For one of my Computer Science classes during Spring 2002, we had to make a website as a project. After the projects were done, I decided to go through the upload directories and look at what everyone else had done. One of the other students in the class did his website on building speakers. Up until then, I wasn't aware that someone could build speakers. Since I had just got my tax return, and would love a really nice pair of audiophile speakers, I decided to look more into the hobby of Speaker Building. Afterall, it involved building stuff...
So, with $600 burning a hole in my pocket, I started reading and reading all sorts of articles and such about designing your own speakers. There was a lot more to it than I had expected at first. Lots of pretty advanced physics, mathematics, electrical design and luck. Even after spending a good month or so learning everything I could about speaker design, I still wasn't confident designing my own speakers. Afterall, I didn't have another $600 to try again, and I really wanted a good set of speakers. So, after looking at many people's designs, I decided on Dave Brown's dB61TL as the first pair of speakers I would attempt to build.
I'll do my best to keep this simple, yet informative. The dB61TL is a 2-way Transmission Line speaker design. There are many types of enclosures a speaker can be put in (sealed, vented.. etc). I chose a Transmission Line because it seemed more obscure, and is known for it's flat response and extended bass range. A Transmission line is basically an enclosure that starts at the driver and is 1/4 of the tuned wavelength long. In this case, the Line is 106" long. This particular Transmission line also tapers, so it decreases in sectional area by 25% (taper ratio of 75%). In this design, the Transmission line is also folded at the bottom (to make a U shape) so the speakers aren't 106" tall, they can be less than half of that.
For someone not too familiar with speakers, this particular speaker is a "2-way design". Meaning that there are 2 separate drivers in each enclosure. The big one is a woofer, and handles the lower frequencies. The smaller one is a tweeter, and it handles the high frequencies. A group of filters called the "crossover" separates the frequencies and sends them either the woofer or the tweeter or a bit of each.
Lets get into the building of these puppies..
At the time, the only large hardware store in the city was Home Depot in the other side of town. There was also a Building Box opening soon near my house. Hayley and I went to Home Depot to pick up the wood I needed for the speakers (two big-ass 4x8' sheets of MDF). When we got there, I was amazed to be helped immediately by one of the Home Depoians. They brought the big ass sheets to their huge saw, and even cut all the wood to the basic sizes I needed for free! Hayley brought the car around the back, and we loaded the wood in.
All the electronics and drivers (about $350 worth) I ordered from parts express in Ohio. To save money on duty, I had them shipped to my friend Eric in Detroit. He "brought" them over once he received them, and the building began!
The first thing was the crossovers. This design has a fairly complex crossover that includes several correction circuits. Including an L-Pad, Notch Filter, Zoebel Impedance Compensation, and Baffle Step Compensation. The Baffle Step Compensation (BSC) I found to be really interesting, and something I would have never thought of otherwise. The waves from the woofer is supposed to reflect off of the face of speaker enclosure to get a proper response. The problem is, most speakers aren't wide enough for all the frequencies to reflect. So the lower frequencies with a larger wavelength will completely miss the front of the speaker and be perceived as 6dB quiter. So, the BSC compensates by lowering all the frequencies above that cut-off-point by 6dB making it all even. Really cool science involved in this Speaker stuff :)
Now to make the enclosures. I cut all the smaller pieces to size, and used my new Router to make proper speaker holes. The holes for the drivers has to be sort of like a "step" so the drivers sits flush with the front of the speaker baffle. There's a bit of science behind this, but put simply, sound reflects off of the front of the speaker, and if the driver isn't lined up, it won't reflect off properly and at the right time. (I'm pretty sure that's the explanation.).
So, I used some big-ass clamps and glued all the pieces together. Filled the inside of the enclosure with poly-fill (from the new "Super walmart") and started finishing the cabinets. If you've ever seen MDF, you know it's just plain ugly looking brown. That's not cool...
By this time, the Building Box was having their "Grand Opening". So Hayley and I attended, hoping to see their hammer-headed mascot. He wasn't there, but cheap veneer was! Veneer is amazingly thin wood that you can glue onto things to make it look like the whole thing is made out of wood. It's different and a lot nicer than that fake wood laminate shit that your computer desk is probably covered in. So, I picked up 2 big rolls of Birch Veneer (enough to do both Speakers) and some contact cement for a cool $60CDN
The veneer gets cemented on, and the edges get trimmed off. Seemed like an easy enough process, although veneer isn't the easiest thing to work with. Thankfully, everything went cool... or so I thought.
The next morning my mom woke me up, and said that the veneer had "bubbled up". Sure enough, it was all bubbly and completely crapped up. But, I noticed if I pushed really hard on the bubbles, they'd go back in and stay there. So, I took a bearing from a router bit (similar to a skateboard/rollerblade bearing) and jammed it on a screwdriver. This way I could put lots of pressure on a small area, and roll the bubbles back down without leaving any scratches or anything. Amazingly, it worked! So, I sanded the surfaces and then applied 3 coats of polyurithane (sanding inbetween) to bring out the grain and protect the surface.
After that was done, I put the woofers and tweeters in their holes (using a type of a caulking to make it all air tight) and they were basically done!! I also made some bases for the speakers because they were a little tipsy, and the bases double as a place for the crossover to go. I painted these bases with a bunch of coats of flat-black spray paint.
The Verdict?
I have to compare these to my previous speakers; Technics 3-Way speakers I purchased at radioshack for $300 about a year before...
Compared to the old speakers, these sound HUGE (they also weigh about 5 times more as well). The bass response is quite different. The Technics had way too much bass, and it was muddy and hard to understand. Like I could tell there was a bass guitar playing, I just couldn't really tell exactly what it was doing or what sort of environment it was in. With these new speakers I can still hear the bass, only now I can really make sense of it. This is my first pair of audiophile-quality speakers that I've listened to for more than 20 minutes at a time, and it is a little strange to get used to. Since the response is basically flat, it's a lot different listening to music that you are familiar with. All of a sudden, the sound is more full and some of the instruments have a better timbre, and some sounds seem even brand new! Also, listening to jazz tracks that use a Double Bass, the lowest notes don't get lost anymore. This shows that these new speakers have a bass response that can go as low some sub-woofers. The treble is a lot clearer too, and drums seem to be more predominant and don't blend into the other instruments. The problem with the detailed treble, is that MP3's annoy me even more now since a lot more of the atrifacts from the compression really show. I made the base of these speakers exactly the right height so they are exactly on level with my ears as I sit here in my computer chair. I've listened to speakers well over $1000 at futureshop, and I'd have to say I'll take these ones any day! One thing that is really noticeable about these speakers is the imaging. Unless you knew the big boxes in the corners were making the noise, you'd be absolutely freaked out walking into my bedroom. All the instruments sound placed all around you, as though each has their own little spot they are coming from.
The finish turned out great, and they look awesome in my room. They sound great, and I'm really happy with the final product (like you can't tell!). I'd have to say Speaker Building is one of the most rewarding DIY projects I've done, since you are left with years and years of awesome sounding music. I recon these won't be the last pair of speakers I will be building!
dB61TL Speaker Project Budget [in CDN funds]
Parts Express
- Drivers
(2) Dayton 6-1/2" Poly Woofers - $52
(2) Dayton 1-1/8" Silk Dome Tweeters - $48
- Crossover Components
(2) .33mH 14Ga. Perfect Layer Inductors - $22
(2) 2.00mH 18Ga. Perfect Layer Inductors - $20
(2) .40mH 18Ga. Perfect Layer Inductors - $11
(2) .3mH Air Core Inductors - $8
(2) Dayton 8.2uF Polypropylene Capacitors - $8
(2) Dayton 6.8uF Polypropylene Capacitors - $7
(2) Dayton .1uF Polypropylene Capacitors - $3
(2) Dayton 5.1uF Polypropylene Capacitors - $6
(2) 47uF non-Polarized Capacitor - $4
(2) 6 OHM 10W Non-Inductive Resistor - $4
(2) 20 OHM 10W Non-Inductive Resistor - $4
(2) 30 OHM 10W Non-Inductive Resistor - $4
(2) 8 OHM 10W Non-Inductive Resistor - $4
(2) 8 OHM 20W Resistor - $2
(2) Mills 2.5 OHM 12W Non-Inductive Resistor - $11
- Other
(2) Gold High Power Terminal Rectangles - $12
36" Speaker Sealing Caulk - $2
Shipping - $20
Home Depot
- Wood
2 4x8' sheets 3/4" MDF - $55
Canadian Tire
- Tools
Black & Decker Plunge Router - $99
Flush Trim Router Bit - $14
Rabbet Router Bit - $21
Cutting Bit - $17
(2) 24" Clamps - $16
The Building Box
- Finishing Material
Birch Veneer - $64
Contact Cement & Wood Glue - $8
Polyurithane - $10
Radio Shack
- Wire
30FT. 12ga Speaker Wire - $30
Walmart
- Stuffing
2LBs Polyfill Pillow Stuffing - $10
TOTAL: $690 (with 15% tax)
Ahh.. Beautiful Pictures!
