I just finished my latest project. Up until now I focused on HiFi, but this time I wanted something for a bass guitar that could also be used as a sub. As such, my design parameters were a bit different:
- high sensitivity
- hi power
- transportable
- reasonable bass extension, ideally 41Hz for the E string
I chose the 1840 from etone:
etone PROFESSIONAL SOUND
They are hand made (assembled) here in Sydney by an old Chinese man in a shed in Bankstown. He doesn't do HiFi drivers because of intense competition, but he makes a good business in the professional market. He can make drivers to spec. This driver has 101dB sensitivity and continuous ratinng of 800 watts. It has a 100mm voice coil and a huge magnet. The resonant frequency is higher than you would expect because he has used a light cone to improve sensitivity.
I chose a 150l box, which I reckon is about 120l after all the bracing I used. According to WinISD, this will give me a 3dB point of about 55Hz, which is higher than I wanted. In a domestic situation, the amount of headroom this driver gives means that a lot of eq can be used to improve the response to 40-45Hz while still getting generous power handling. It certainly does not sound lacking in ths area.
Previous experience with subs has shown me that extensive bracing is required for subs in large boxes. Because of the power handling of this driver, I decided to use a honeycomb style bracing that starts 20mm behind the woofer and entends to the back of the box. The box is made of 18mm ply, and the bracing is 16mm MDF. The bracing is designed so that the largest un-braced span on the box is about 100mm. Everything is glued, then nailed with 50mm finishing nails, then screwed with 65mm screws.
I was after an industrial finish, so rather than hide all the screws, I made them a feature by screwing every 50mm along the braces to form a grid pattern of screws on all sides. I finished in a satin black stain so it still works as furniture while fitting in as a PA box.
