This is a 2-way design using a 12 inch pro woofer coupled with a compression driver in waveguide. The speakers are designed to be on the floor, and tilted towards the listener, not unlike a stage monitor.
My goal is to design a high sensitivity speaker that can be used for many different purposes, to listen to music using low powered tube amplifiers, or for karaoke or PA purposes. The cabinet can be propped on stand, or can be left on the floor. A typical 5′-9″ individual standing 10 feet away would perfectly face the speaker baffle on axis.
I selected the Eminence Deltalite II 12″ Neo woofer due to its light weight and relatively small box requirement. The fact that its frequency response can extend to 3KHz is also important in a waveguide design. For the tweeter, I chose the Eminence PSD 2013 compression driver due to its ability to cross fairly low and relatively low price. For the waveguide, the SEOS-12 was used due to the fact that it allows low crossover points with minimal distortion, and is generally well reviewed by DIYers.
The enclosure volume is 3.3cu.ft with a F3 of 50Hz. The vent is 2″ high by 13.5″ wide, and 6.25″ deep. Due to the unusual shape of the cabinet, I modeled the box first in Bassbox to determine the volume, then I used Sketchup to model the shape of the box based on this volume. I then “broke” the box apart to determine the shapes, dimensions and angles of the different panels.
Cutting the panels was time consuming due to the fact that the table saw blade had to be adjusted according to the angle of the panel. Once this was done, putting the box together was straight forward. Sketchup was accurate to the point that all pieces fit together with very minor adjustments.
The crossover point was around 1,500Hz, which was the minimum frequency recommended by the tweeter’s manufacturer. Both the woofer and the compression driver behaved extremely well, with the woofer requiring just three components, and the CD another three with a RLC notch filter to achieve steep 4th order slopes. Phase tracking was relatively good, given the deep z offset between the woofer and the CD.
Tips & Tricks:
Sketchup or a similar 3D application will make designing unusually shaped speakers more practical, and also helps maximize panel cuts to avoid wastage.
This project is my first foray into the world of pro woofers, one that validates what all of you have been discussing and writing about these drivers. With certain tracks, these speakers give the music a definite “live” quality as if one was standing close to the stage. If you like to sing, these high sensitivity drivers will make it effortless to hit your notes. The simplicity and low cost of the crossover components are also a big plus.
About the Designer:
Hong Nguyen is a healthcare professional specializing in the development and management of ambulatory surgery centers, and a member of the Speaker Building Design Team.