On April 15th 2008, the Audio Society of Minnesota hosted a members-only loudspeaker design challenge.
The design rules were simple:
1. The only drivers used in this challenge are the SB Acoustics SB025F9 1" tweeter and the Peerless 831990 5" woofer. Due to interest and the sellout of the original two drivers, the contest has been extended to the Peerless 830341 woofer (a 4 ohm variant of the original) and a nearly identical substitute SB Acoustics tweeter is available if you reference the original part number.
2. There are two categories of competition, Specified (Spec) class and Unlimited class. The Spec class must use one each of the chosen drivers per speaker and a passive crossover. The Unlimited class may use as many of the drivers as desired, and may use active or passive crossovers. Entrants using active crossovers must provide their own amplification.
3. The club system will be used in the judging, and to facilitate connection all speakers which will use the club amplifier must have available standard-spaced banana jack terminals.
The idea behind this contest is that everyone starts with the same drivers, and the difference between the finished speakers will be solely in the execution of the design of the cabinet and crossover.
Judging criteria are: Sound quality, Build quality and Technical measurements, as judged by non-participants. Judging sheets and measurements are attached in Excel files below.
Results
The process of the judging went like this. The speakers were given a number and set up in a room where they were submitted to the aesthetic senses of our judges. From there we brought the speakers out at random one at a time, set volume with a pink noise and listened to a preset list of tracks. The judging sheets allowed judges (all non-participants) to rate the speakers according to a set list of criteria. Once listening was complete, the speakers were rushed to another room where Wally Malewicz performed acoustic and electrical measurements on them.
We warmed up the judges with a pair of low-fidelity control speakers - a "highly rated" $50/pair set using a 5" woofer and 1" tweeter (System 8 in the Excel sheets, Sony SSM-B100H - see Audioreview for ratings) to relieve the participants of the onus of going first.
The systems were labeled 1-8, with the Sony's as #8. Below is a list identifying System # with builder and their judging class.
1. Spec Class (eyeball tweeter) by Nathen Field
Dayton Black Lacquer cabinets with an architectural post as the tweeter pod mounted on top and slab wood sides. Vented boxes, 2kHz crossover.
2. Spec Class by (mini blond cab) by Nathen Field
Dayton Blond cabinets, vented box, 3kHz crossover.
3. Unlimited Class (Corian-composite sandwich MTM) by Chuck Bottemiller
Home constructed cabinets of ~1.5" thick composite wood material - veneer skins over honeycomb cardboard core. Corian front baffle.
4. Spec Class (Black Shelf Speaker) by Tom Mittlestaedt and Jon Zehnal
Tom and Jon found an easy way to make speakers using prefinished shelving material. These looked quite good for the amount of time invested.
5. Unlimited Class (Birch ply MTM) by Ron Ennenga
Birch plywood boxes - 18x7x10, 3kHz 3rd order crossover with drivers in phase.
6. Spec Class (PVC Tube) by Gene Lyle
23" long 6" Dia Open back PVC pipes stuffed with long fiber natural wool.
7. Spec Class (Hardboard-foam sandwich/motor caps) by Jay Tonkinson
Cabinets made of hardboard skins glued to either side of polystyrene insulation sheets - mitered construction with bracing /diffusion created by gluing whiffle balls inside the enclosure in a matrix.
Results:
Spec Class winner: Nathen Field for System #2
Unlimited Class winner: Chuck Bottemiller for System #3
Aesthetics Winner: Nathen Field for system #2
Creativity Winner: Gene Lyle for system #6
Sound Quality Winner: Ron Ennenga for System #5
Judging sheets and measurements are attached below. All raw data (including judges written comments) relevant to scoring and judging is contained within the Excel document