Journal continued... Comments about the driver:
I’ve studied reviews of many 12” drivers and I decided to go with the CSS Trio 12” driver. This modeled very well and the reviews were positive. A concern was raised by other reviewers regarding the stamped steel frame and the potential for vibration or structural failure. After inspecting and operating this driver, I believe the engineering and fabrication is solid. In my opinion, this driver is a great value. It delivers great performance at a good price. I am very happy with this driver. Comments about the amplifier:
Sound quality and performance is great. I’ve observed nothing concerning regarding the performance. The auto-on feature does not work and PE is replacing this under warranty. I haven’t received the replacement yet so I can only speak to what I know with the original. I do hope the replacement works as advertised. I think this is a good value amplifier. If you are considering this amp for your project please read the forums regarding the factory set high pass filter. I believe the amp’s default HPF is set to 30Hz (or thereabouts) and if you’re building a sub it’s likely you’ll want the amp’s HPF much lower. There’s a 1-page manual (http://www.parts-express.com/pdf/300-752.pdf
) that’s shy on details. The “Bass Boost” tables provide the details you’ll need to modify the HPF to align with your WinISD model. In short, you can select and modify your amp’s HPF by changing 2 resistors on the pre-amp board. I chose the +1 dB bass boost at 27 Hz center frequency and 18.7 Hz cutoff. A screen shot from WinISD shows how I modeled this HPF. I remember reading forums where more than +2 dB bass boost was not advisable. I am comfortable soldering many things however this preamp modification project was outside my comfort zone. I am fortunate to have a coworker experienced in circuit board building and repair. He expertly de-soldered the 2 factory resistors and soldered-in the new R17 and R18 resistors (Thanks Kerry!). 6Sep11 Update: I called Parts Express on Monday, 29Aug and described the problem with the first amp. 2 days later I had a replacement amp sitting at my doorstep. This replacement amp works exactly as advertised (auto-on/off works great). Project Cost Summary:
$169 - CSS Trio 12 Driver (includes $20 shipping)
$189 - BASH 500w amp from Parts Express
$20 - Hardware, magnets, grill cloth etc from PE
$200 – Oak boards, MDF, ¼” oak plywood, pine boards etc from Lowes
$20 – Cable management and other misc stuff.
Total cost for this project ~$600. Note, I didn’t tally costs for the birch plywood (braces), ¾” oak plywood (lid), 1” plywood (driver and amp plates), glue, screws and polyurethane finish. These were leftovers from other projects. I estimate these materials would add another $60 to the cost of this project. Final thoughts:
If you are reading this because you’re considering building a DIY sub, I say “go for it!” I was in your shoes too. This was my first sub build and it was a good experience. It took some time to understand WinISD’s inputs and outputs but the HTS forum and members were very helpful. After I converged on the box dimensions and modeled performance, the biggest challenge was construction of a wedge-shaped enclosure. Building a cube or rectangular shape with 90 degree joints would have been much easier. In the end, I feel I got a great performing sub at a great price.
And “Yes”, I would do it all over again!