DIY Bass Speaker

Subwoofers provide ultra-low bass.

The trend in music is more and deeper bass in stereo. Standard LP mono records have been replaced by the new low bass: the subwoofer. These speakers are able to reproduce notes as low as 16.35 Hz. Down there, 100 dB of amplitude is needed to hear anything at all. These speakers use two 10-inch drivers in a vented box. They are designed with a tuning frequency of 17 Hz in a volume of 270 liters. They are crossed over here at 32 Hz; you should cross below 100 Hz. Construction and recommended components follow. (See Reference 1)

Things You'll Need

• High Density Fiberboard (HDF) 19 mm thick, 12 pieces with sizes specified in text. (2 speaker boxes) Fiberglass building insulation (enough to fill about half of the speaker box space) Speaker wire (Flatline cable) Drivers (2 needed per speaker box for a total of four) either ScanSpeak 25W7564 or ScanSpeak 25W8565-01(See reference for specifications on parameters and details) Filters LM837 quadruple op-amp chip (See Reference for choices and or modifications) Amplifier (low-power heavy built with a large power supply similar to a Hiraga LeClasse-A 20 W) 100 W input per channel. Circular saw Wire cutters Soldering gun and solder One- and 1/2-inch wood screws Electric drill and bits Power screwdriver 10-inch hole saw

Instructions

1. Cut the speaker cabinet pieces out of High Density Fiberboard (HDF). Use the three drawings in the reference to assist in the assembly. Drill 1/2-inch starter holes and power screw tightly, with inside pieces first and frame last, using 1- and 1/2-inch screws. Fill the speaker boxes half way with loosely packed fiberglass insulation. Leave space free at the port end of the box.

2. Mount drivers in position. The support pieces for the driver magnets are extremely important in order to realize tight and uncolored bass. Without this piece, resonances are drained from the drivers' chassis, making it impossible for the driver magnets and chassis to move in the opposite direction of the voice coil. It will not function without this support piece. Perfect alignment is required here to tightly contact the driver's magnet.

3. Install and connect filter crossovers using the flatline cable and connecting it in place following directions with the filters. This will connect your subwoofer to your main stereo speakers.

4. Test with an amplifier and subwoofer recordings. Hook up the system, adding the amplifier and placing it on top of the floor-based subwoofers.

   Run a series of test records that present your new world of subsonic hearing. Crank the amplifier toward 100 dB range and feel the ambiance of a woofer flying without audible sound.

Tips & Warnings

• Place the heavy amplifiers on top of the speakers to stabilize units. Subwoofers connect through crossover filters to the main speakers, extending the bass range.

• Be careful not to split the fiberboard when drilling and power screwing. This article is intended for the experienced audiophile and DIY speaker-box builder. Many construction details are assumed in lieu of technical performance on the subwoofer system and its interface with the audience.

References

• SpeakerBuilding.com - REAL subwoofers!