The Subwoofer DIY Page - DIYAudio Projects
The TH18
 27 October 2018

Classification Data:
Name: TH18
Type: "Tapped-Horn" (1/4 wave resonator)
Use: Pro Audio
Recommended Driver(s): 18 Sound 18WL2400
Fb: 36.8 Hz
Dimensions: 101.6 cm x 571 cm x 724 cm (40" x 22.5" x 28.5")
Designer: Martin Cox

Introduction:
The objective of this design was to produce a reasonably compact "tapped-horn" using an 18" driver that would have decent performance and the ability to be fed with power in excess of 1kW without experiencing excursion issues. An extended high frequency response was also an objective.

Simulation:
The imput parameters to the corresponding HornResp simulation are as follows:
 

The predicted frequency response with the 18 Sound 18WL2440 driver is as follows:

The predicted group delay is as follows:

Build Information:
A cutsheet for the TH18 can be downloaded here. Note that the cut sheet does not include bracing.  A suggested bracing scheme is shown below

Some build pictures...

Results:
(TBD)

 

Suggested Improvements:

  1. Double the thickness of the bottom panel to reduce the tendency of the box to "walk" at high volume.

  2. Using a metal grille at the mouth that's fastened to all four sides will also reduce panel flex.

Discussion:
DIYAudio discussion thread