I was hoping to build a high-efficiency woofer system for use with a Lowther field coil driver. The field coil is 98 db efficient, making the TD15M the reasonable choice. What would you recommend as far as box size and a passive radiator to maximize low frequency response. Would like to have an F3 of 40 hz or less.
It’s unlikely you’ll get a perfect match in efficiency no matter what you do. You will always baffle step to worry about which is a 6dB drop. The easiest way to implement a 2way system like this is by going with an active system. Then efficiency would not be an issue as you can match the levels in the crossover. Keep in mind that you also want to compensate for the baffle step which requires EQ and you’ll want ability for time delay/phase adjustment. The most simple way would be to use a Behringer DCX2496 for the processing, although that is not the most high end option. The DEQX is another choice. Another option I’d like to explore myself in the future is the dsp unit form http://www.minidsp.com. The 2 channel stereo crossover plugin would do everything you need. http://www.minidsp.com/images/documents/Product%20Brief-Crossover%20PEQ%20plug-in.pdf
In terms of output, a single TD15M in 6cubic foot tuned to 32-40hz will do well. In most cases for music you’ll want to get down close to 30hz to cover the low B on bass guitar and low A on piano. The 40hz tune gives an F3 about 40hz, while the 32hz tune costs some efficiency but gives more extension. With the dsp unit you can then EQ this response back up if necessary. That would be the way I would go ideally. You’ll still be capable of about 117dB at 40hz with 200W input.
Red if 40hz tune and green is the 32hz tune.
If you go active and efficiency is not an issue, a TD15H will allow you go to much lower in smaller enclosures. A 4 cubic foot enclosure tuned about 30hz looks good. You can then apply up to about 750W or so to get good output levels up in the 120dB range.
The response of the TDM15 in a 6 ft3 enclosure tuned to 40hz looks really good. Does “tuned” mean a port or passive radiator? Could a similarly flat response be achieved in a sealed enclosure (sealed so as to combine better with a vented sub)? Mine are in 2 ft3 enclosures and looking for a new home 🙂
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