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The Plumber's Delight
Here are a few pictures of my latest speaker building project.
I used the 24.5 x 72 x 1.125" workbench table top particle board they sell at Menards for $14.99 a sheet. The finished speakers are 19 lbs each. You might think this thickness is overkill for such a small speaker. But what I was trying to do was to increase the mass of the speaker as much as possible to reduce self-cancellation caused by the entire speaker moving back & forth at low frequencies.
Gross internal volume is 3 liters (5.30x3.55x9.75"). The port is 26" long with a 1.6" inside diameter. This tunes the system to somewhere in the 40-42Hz range. A 10" long by 1.25" inside diameter bass trap eliminates the 1st and 2nd port resonances at 260 and 520Hz. This trap is stuffed with a small amount of Acousta-stuf and dacron material. Tuning was done experimentally by changing the trap length and stuffing density, on the fly, as I measured the near field response with OmniMic.
Drivers are the Tang Band W5-2053 subwoofer, the Techtonic Elements TEBM46C20N-4B midrange, and the Morel MDT-39 tweeter. Crossover frequencies are 320 and 2400Hz. Sensitivity measures somewhat low at 82-83dB/2.83V/1 meter.
Because I am using a 4 ohm subwoofer and a 4 ohm midrange, the overall system impedance dips to about 3 ohms in the 90 to 150Hz range (see graph). I have played the speakers at moderate to somewhat loud levels with a number of amplifiers and have not, as yet, had any problems with amplifier overheating or the tripping of amplifier protection circuitry.
I measured total harmonic distortion at various SPL levels with OmniMic and then transferred this data to a spreadsheet (see attached). Subwoofer distortion at 80Hz appears to be the weakest point, with midrange distortion at 300Hz a close 2nd. When I listen to the speakers at the 86-89dB level, there is absolutely no sense of strain, but when I push them to either the 93-95 or 95-97dB levels, I can hear a very serious dynamic compression effect starting to set in.
Any comments or questions are welcome. Thanks for looking.
Bill
I used the 24.5 x 72 x 1.125" workbench table top particle board they sell at Menards for $14.99 a sheet. The finished speakers are 19 lbs each. You might think this thickness is overkill for such a small speaker. But what I was trying to do was to increase the mass of the speaker as much as possible to reduce self-cancellation caused by the entire speaker moving back & forth at low frequencies.
Gross internal volume is 3 liters (5.30x3.55x9.75"). The port is 26" long with a 1.6" inside diameter. This tunes the system to somewhere in the 40-42Hz range. A 10" long by 1.25" inside diameter bass trap eliminates the 1st and 2nd port resonances at 260 and 520Hz. This trap is stuffed with a small amount of Acousta-stuf and dacron material. Tuning was done experimentally by changing the trap length and stuffing density, on the fly, as I measured the near field response with OmniMic.
Drivers are the Tang Band W5-2053 subwoofer, the Techtonic Elements TEBM46C20N-4B midrange, and the Morel MDT-39 tweeter. Crossover frequencies are 320 and 2400Hz. Sensitivity measures somewhat low at 82-83dB/2.83V/1 meter.
Because I am using a 4 ohm subwoofer and a 4 ohm midrange, the overall system impedance dips to about 3 ohms in the 90 to 150Hz range (see graph). I have played the speakers at moderate to somewhat loud levels with a number of amplifiers and have not, as yet, had any problems with amplifier overheating or the tripping of amplifier protection circuitry.
I measured total harmonic distortion at various SPL levels with OmniMic and then transferred this data to a spreadsheet (see attached). Subwoofer distortion at 80Hz appears to be the weakest point, with midrange distortion at 300Hz a close 2nd. When I listen to the speakers at the 86-89dB level, there is absolutely no sense of strain, but when I push them to either the 93-95 or 95-97dB levels, I can hear a very serious dynamic compression effect starting to set in.
Any comments or questions are welcome. Thanks for looking.
Bill
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