Dark Thunder Bookshelf Speakers

Dark Thunder Bookshelf Speakers


Designer:
Anonymousish

Project Category:
Bookshelf Speakers

Project Level:
Intermediate

Project Time:
20+ Hours

Project Cost:
$100 – $500

Project Description:
A set of bookshelf speakers for my desk.

Design Goals:
The design goals for this project were to design and build a set of speakers; that were both small enough to fit on the desk, and with a deep enough bass response as to not require a separate sub under the desk.

Driver Selection:
To keep costs down I decided on a 2-Way speaker. For the drivers I’ve use the Tang Band W5-1138SMF subwoofer, as the woofer. Choosing a subwoofer over a conventional woofer meant I could get more bass extension from the 7 litre enclosure. And the Dayton Audio DC28F-8 is the tweeter, being budget friendly with a good reputation for performance per dollar and going low enough to meet the W5-1138SMF.

Enclosure Design:
The enclosure is a front slot ported (because of the proximity of walls), bass reflex enclosure. The port is very long, running to the back of the enclosure, up the back and a bit forward again. This helps to give it a very low tuning of about 35 Hz; important for the bass extension. The bottom, back and top are foam lined to damp the enclosure, with the crossover glued to the side.

Crossover Design:
The W5-1138SMF has a significant, but smooth, hump between 1000 and 2000 Hz. So I had to start the roll off relatively early (compared to where they actually cross). I achieved this with a 2nd Order low pass filter using a 0.8 mH inductor and a 50 μF capacitor.

The tweeter is hooked up to a 3rd order high pass filter consisting of a 8.3 μF (3.3 + 1 + 4) cap, 0.6 mH inductor, and 24.8 μF (6.8 + 10 + 8) cap. With an L-Pad made of 5.5 Ohm (5 + 0.5) (series), and 3.7 Ohm (parallel) resistors.

Conclusion:
In the end, I think they sound great! They definitely meet the design criteria and have a solid frequency response down to 35 Hz, truly mini-sub performance without needing a separate sub.

About the Designer:
A guy who likes audio stuff from the UK. This is in fact my first build.

Project Parts List:

Tang Band W5-1138SMF 5-1/4″ Paper Cone Subwoofer Speaker
Dayton Audio DC28FT-8 1-1/8″ Silk Dome Truncated Tweeter

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