The Sidewinder

For my second subwoofer, I wanted a smaller box with no port noise, a higher output, a lower cutoff frequency and a better standard of finish. Switching to the Jaycar driver with a lower Vas and fs, cut the box size from 90 litres to 65 litres.
The enclosure was veneered in blackwood with redwood top and bottom. Originally fitted with 50mm internal ports, this enclosure looked quite good. Port noise forced the move to larger external ports, and the controversial looking Sidewinder was born!

Sidewinder Photo


The 150W amplifier is the only one in the Jaycar range without boost, which gives a flatter response. This gives a slightly higher Peak SPL of 106db, but more significantly, gives a better output in the 25-30hz range

Graph - Peak SPL


Originally this speaker had three 50mm internal ports and the noise was atrocious. By this time, a later version of WinISD was available, which graphs vent air velocity and recommends that the peak not exceed 17 m/sec.

Blanking of the original ports and moving up to three 90mm ports gets this figure to below 10 m/sec.

Graph - Vent Velocity


The ends of the ports were hand sanded for a flare of approximately 5mm. Unfortunately some "chuffing" is still heard on louder content. This Flare-it screenshot shows why

Flare-it screenshot 5mm flares


A minimum of 16mm flares would have solved the problem. This would have been a good candidate for 20mm heat molded flares

Flare-it screenshot 16mm flares


Cone excursion was going to be excessive below the vent's resonant frequency and so a separate Linkwitz-Riley Active filter was used.
See the description of the Linkwitz filter at the bottom of the Active filter page
The Blue line is with the filter and the Brown line is without. Xmax is the Red line

Graph - Excursion


Sidewinder Gallery


/sidewinder.htm last modified: 31 December 2018
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