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I needed a little sub for my living room (22' x 13') for general TV watching at moderate levels, but I also wanted it to still play low. I knew I would need a driver that could use a very small box and also have long excursion. After reading the reviews of the TB 740P 8" I was sold, but modeling it in a small sealed box gave a roll-off of around 50Hz. Some sort of low frequency boost will needed to get the response I want, then I remembered the Active Subwoofer controller project from Elliot Sound Products (http://sound.westhost.com/project48a.htm). There will need to be plenty of power available to drive the sub to full excursion in a small enclosure, so an SPA-250 amp was added to the order.
Using 3/4" MDF, I built a box that was 11" x 11" x 11.75". I wanted to stay at 11" cubed, but adding the extra layer to recess the driver added extra stiffness and visual appeal. This yielded an enclosure with 0.5 cuft internal volume before stuffing it with gear. The basket, magnet and cone of the 740P is larger than a typical 8" and the SPA-250 is a whopping 3" deep (behind the mounting plate). Once the amp and speaker are mounted, the net internal volume is around 0.3 cuft. Stuffing is two thick layers of FG insulation which sounds much better me than 'Polyfill'. If you do this, wear long sleeved gloves while working with it!
The processor is simply a single band EQ set at 18Hz (can be set to other frequencies) with a slope of 12dB meant to match the roll-off of sealed subs. The unit is installed between your receiver (or other audio source) and sub amplifier. Its purpose is to add boost to the signal the sub amp sees and extends the usable bottom end of a subwoofer system. There is a price however - you will need a driver that can take the excursion and more power than usual to get it to work properly. It is a simple project that anyone with soldering experience can handle.
The result is more than I could have imagined. For general TV and music in the family room, it is MUCH more sub than necessary. :D The sub plays down into the 20's with great clarity and hitting harder than I thought it would. Trying it out without the processor resulted with what you would expect a 50Hz roll-off to sound like - high and a little thin. The processor is well worth the effort.
Using 3/4" MDF, I built a box that was 11" x 11" x 11.75". I wanted to stay at 11" cubed, but adding the extra layer to recess the driver added extra stiffness and visual appeal. This yielded an enclosure with 0.5 cuft internal volume before stuffing it with gear. The basket, magnet and cone of the 740P is larger than a typical 8" and the SPA-250 is a whopping 3" deep (behind the mounting plate). Once the amp and speaker are mounted, the net internal volume is around 0.3 cuft. Stuffing is two thick layers of FG insulation which sounds much better me than 'Polyfill'. If you do this, wear long sleeved gloves while working with it!
The processor is simply a single band EQ set at 18Hz (can be set to other frequencies) with a slope of 12dB meant to match the roll-off of sealed subs. The unit is installed between your receiver (or other audio source) and sub amplifier. Its purpose is to add boost to the signal the sub amp sees and extends the usable bottom end of a subwoofer system. There is a price however - you will need a driver that can take the excursion and more power than usual to get it to work properly. It is a simple project that anyone with soldering experience can handle.
The result is more than I could have imagined. For general TV and music in the family room, it is MUCH more sub than necessary. :D The sub plays down into the 20's with great clarity and hitting harder than I thought it would. Trying it out without the processor resulted with what you would expect a 50Hz roll-off to sound like - high and a little thin. The processor is well worth the effort.
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