BUILD THIS! Dual 21-inch subwoofer
It's a monster! Celestion have designed a dual horn-loaded subwoofer cabinet, specifically for use with the NTR21-5010JD neo magnet, cast aluminium LF driver.
November 4, 2014
Material: 18mm birch plywood
Drivers: 2 x NTR21-5010JD
Max continuous SPL (predicted, single box): 138dB 1-watt/1m (-6dB at 45Hz,)
Recommended high pass filter: Butterworth: 24 dB/octave (40Hz cut-off)
Alternatively buy a DIY kit here!