25mm or even laminations of thinner material are common methods for improving box
rigidity. Corner bracing is popular and works well, as do internal braces between walls.
Don't forget to take account of the volume of any inner bracing when you are optimising
the box size. When we are designing boxes we always allow an additional small amount
(say 0.25 cubic feet or a few litres) of extra space so that we can tune the box accurately
afterwards. You can't add space after but you can fill it with bracing and resin or other
objects to reduce it! On the larger subwoofers it is essential to make the baffle (the side of
the box where the woofer is affixed) from a double layer of 18mm MDF as a minimum. This
reduces box interference greatly and is proven to be a worthwhile exercise. DO NOT use
screws to fasten your subwoofer into the box. It works but they strip easily, can come
undone and do not offer professional repeatability in respect of service work to the
enclosure or speaker. We offer our BFTNUT.1 kit which has ten 60mm long high grade M5
bolts with matching T nuts as an excellent way of retaining your woofer to the enclosure.
Also take note that should you carpet the enclosure you will need to cut the carpet carefully
around the woofer. Do NOT bolt the woofer to carpet as it is porous and could affect the box
parameters.
When running more than one woofer in a mono configuration we recommend that you
share enclosure space and keep the speakers as close together as possible in the baffle.
This tends to do the most effective job of allowing the speakers to act as a single piston,
moving the optimum amount of air. Do note well that should you decide to operate stereo
bass you MUST run the woofers in separare air chambers. Additionally, if you are running a
complex setup of multiple amplifiers driving multiple coils or speakers you MUST meter the
