A speedster is a car that was meant for one thing: to be fun to drive. It wasn't meant for picking up groceries, or hauling the family around. It wasn't meant for commutes on cold mornings, or city driving across potholes. It was meant to whip around corners and let you feel the wind in your hair and the bugs in your teeth--and look cool doing it. It's a rich boy toy. No one needs a roadster, but people buy these things because they're a fun way to forget your problems and focus on the exhilaration of white-knuckled driving, if only for a few hours.
These speakers are like those roadsters, spyders, speedsters, and barchettas. They are meant to be small, cool, and fun to listen to. They're for private listening, and enjoying the music, and leaving your cares someplace else, miles away. They are not the cheapest speakers on the block. but you get what you pay for: a well-engineered woofer with a massive underhung motor, and a true ribbon tweeter. The result is a speaker that provides plenty of detail and dynamics, but in a very small cabinet. Depending on how you finish them, they can disappear into the decor of a room, or be showcased like the little luxury item they are.
Well anyway, when I finally went on my own volition and looked over Fountek's application notes for the tweeter, they actually recommended crossing at 3000 Hz, using only a 2nd order electrical crossover. That's a much more useful application! I played around with this configuration with some random little woofers and found the sound quite nice.
So the hunt was on for a cool midwoofer to pair it with, preferably something around 4". Now, while there are some european midwoofers that could have done this job quite admirably, I was intrigued by Tang Band's new offering, the W4-1720, with its crazy-massive magnet and underhung motor. It was given high praise by Lou C, who had recently used it successfully in a high-quality mini speaker, so I gave it a shot.
This driver is silly. The magnet is ginormous, like the size of a softball; the photos don't do it justice. Because of the huge underhung motor, the driver is very heavy. The cone is smooth-coated paper, and the dustcap is almost flat and bottlecap-shaped. The driver's Frequency Response is well-behaved, akin to that of many higher-priced Scandinavian drivers. The impedance is higher than the 4 Ohms it is advertised as, which allows it to play nicer with a wider range of amplifiers.
The enclosure for the Speedster is 5.5 Liters. It has a 1.375" dia port that is 4.5" long (mounted directly behind the tweeter). This tunes the box to about 55 Hz. The -3 dB point of the W4-1720 in this size box is in the mid 40 Hz range, which is quite satisfying (more on that later). The cabinet is constructed with 1/2" MDF, and there is no bracing. Instead of lining the walls, I used a few handfuls of polyfil to lightly fill the box. You can add or remove stuffing to adjust the bass response to your taste. The tweeter is flush-mounted, however the woofer is surface-mounted. As you can see the woofer slightly overlaps the tweeter's flange.
The crossover here uses 3rd order electrical filters on the woofer and tweeter. I could have used lower-order filters in this design, however in the end I decided to use higher-order filters in order to shape the drivers' Frequency Responses to my liking. All in all, it's still not a terribly complicated crossover, with 8 components.
The speaker would work on a desk, although I might advise raising it a bit off the surface of the desk to keep bass response in-check. It would also kick ass as a stand-mounted satellite or bookshelf speaker in a small or medium-sized room. As I said about the Overnight Sensations, the big advantage of these type of small speakers is that they can allow for full-sounding listening sessions into the wee hours of the night and won't rattle the walls or wake the neighbors.
To my knowledge, the first one to build a Speedster was [bkeane], who used it as a re-introduction to speaker building. Believe it or not, it was built from mostly scraps. He did a truly outstanding job making sure to get the fit and finish just right. I've seen these in person, and they are the real deal!
Brian's build thread can be found here.
[ILuvPieNCake] decided to build himself a pair of Speedsters before he headed off for college--which officially makes his dorm room the best-appointed one on campus. Honestly, it blows my mind to imagine if I'd had something like this with me in college. Thumbs up, indeed! Here is his build thread.
This pair was built by [Studio 22], an aspiring Industrial Engineer. He absolutely nailed the execution of this project from beginning to end. Take a look at the thread to see what I mean.
These are my Speedsters. Originally mine were just bare MDF, but I had the cabinets rebuilt, veneered, and lacquered by cabinetmaker [s7horton]. Beauty, eh?
This beautiful pair was done by [RINNAV]. In the tradition of Italian sports cars, he wrapped the enclosure in Milan leather, and used aluminum to create trim accent behind the Bordeaux-stained cherry baffle. You can read his build thread here.
You gotta love Ed's curved Speedsters. (The curve was achieved using 1/2" MDF, kerf sawn) The veneer on sides in Wenge, and the baffle is striped Anegre. To take the awesomeness up a level, he made matching stands.
Devin did the Speedsters with a slot port. The finish is a deep-gray metallic auto paint.