Hello, my name is Jeff. I am a senior graduating from the University of Southern California. As a ME, I took a EE loudspeaker design course taught by George Augspurger to fulfill my senior design requirement. The course covers loudspeaker theory and design. The final project is designing and fabricating a loudspeaker. My partner and I had come across the old AV123 design of the X-Statik, and wanted to use that as our model. It was the starting point for our design, and we wanted to build a high end speaker but for the budget minded audiophile. The total cost for a pair came out to $500 using our components. The crossover network on the OB-5 kit Danny sells utilizes higher quality components over the Dayton Audio capacitors and Jantzen inductors. The Beston ribbon tweeter is around $40, less than the B&G Neo3 PDRW tweeter.
We got in touch with Danny regarding advice on the woofers for our project and decided to use the 16ohm versions of the M-130 woofers because we could not find a good 16 ohm woofer that could perform well in an open baffle configuration. The Neo3 PDR tweeter was unavailable at the time, so we decided to try out the Beston RT002A dipole tweeter. We were able to get samples of these tweeters to test directly from Beston as these won't be available in the market for a few months. Our professor, George Augspurger recommended us that if we were running the mids and highs in open baffle, we should get an open back tweeter, and the Beston was only other tweeter within our budget for the project.
The cabinet was constructed using 5/8" Baltic Birch supplied from our school. We didn't use much bracing besides strips of 5/8"x5/8" glued along the inside edges. The internal volume was 33.8L (1.2 cu. ft) with a single 2" flared port tuned to 50hz on the backside. The crossover points are at 400hz and 3500hz, which were based off testing with a microphone using a variable crossover box. We stained it with a red mahogany on the front baffle and black on all remaining panels. We really liked the x-statik color scheme and thought doing all one color would look really old fashioned. The towers were finished with a semi-gloss afterwards. We used a bi-amp terminal plate with 2 sets of connectors in the event we wanted to run the bass woofers off a separate channel from the mids and highs.
Below are pictures of our fabrication and graphs of our mid and high crossover and our measured frequency response for the closed back and open back Beston tweeters. We did not have time during the course of the semester to get a good measure for the overall system response with the low-pass network in place, but I have ordered Dayton V2 Measuring equipment to objectively quantify the performance of our project speaker. This was our first speaker we fabricated, and certainly won't be our last
We would like to thank Danny at GR-Research for his help and advice, as well as our Professor George Augspurger for supporting us in our ambitious undertakings.
Solidworks Model
http://inlinethumb60.webshots.com/47803/2971100690099908742S600x600Q85.jpgConstructed Cabinets (3/4)
Foaming
The interior of the cabinet was fully lined with 1" acoustic foam
Before finishing with semi-gloss
Finished and outfitted with drivers
Crossover
Blue line is the open back tweeter. Black is closed back.
System Response for Mids and Highs
Overall system response, note the mids and highs are not as flat as in the previous graph. The measuring environment was not ideal as there were 10+ groups playing music in the same room doing electrical testing for their systems as we were testing. We hope to do another measurement when our testing microphone arrives. The professor analyzed this plot and based off of our previous plot, assessed we have pretty good response down to 40-45hz. Just redid the frequency sweep. Response looks pretty good.
System Response
Incomplete frequency response
Overall we are really pleased with our results. Previously I had been using Sony's current line of bookshelf and tower speakers and thought they sounded pretty good, prior to doing research into high end audio. These were all driven by a Sony DHR-810 AV Receiver, connected to my computer through external Soundblaster X-Fi HD sound card.
Our project speakers are leagues ahead of the Sony's in terms of audio clarity and tightness of bass. The Sony SSF6000 towers get loud bass response, but at a lack of refinement. The vocals sound cleaner, mids more enveloping with a wider sound stage from the dipole design, and the bass cleaner. Next upgrade I am looking at is the Peachtree Audio Nova DAC and Amplifier to complement these speakers.
Overall couldn't be happier with the finished speaker.
Thanks for reading
