The SD-3 series is our premier sealed box offering. We started off this design knowing that the majority of sealed box applications today face a depth restriction so each SD-3 model was designed to have the lowest depth possible while still maintaining a large window of mechanical cushion (about 2Ó p-p maximum mechanical travel for all models). We do not consider the SD-3 an Òultra-shallowÓ but they are as shallow as possible and feature several techniques to reduce the effective depth required
As mentioned above; the SD-3 series effectively requires less depth than other woofers that are more physically shallow. First of all they have a completely solid pole and, thus, require no room for air venting behind the motor. This allows the motor to be completely flush against the back wall of the enclosure. Secondly the entire SD-3 series features an inverted rubber surround Ð this reduces the space required in front of the woofer to about 1Ó total (we suggest 1.25-1.5Ó when possible for the best sound). So, despite not being an Òultra-shallowÓ woofer they have an effective total depth requirement of about 2Ó less than most traditional woofers of an equal depth.
The SD-3 series truly is a world-class sound quality woofer with low mounting depth, small box requirements, and a reasonable price. This line features an under-hung motor topology Ð this means that the voice coil is shorter than the top plate so the amount of winding in the gap doesnÕt change at all over the center portion of stroke Ð in this case featuring a 1Ó thick top plate and _Ó long 8-layer copper voice coil. This allows for 14.5mm linear excursion one-way while maintaining an extremely flat BL curve. The large inverted rubber surround & high-stroke spider also allow for a very even compliance curve over the full range allowed by the SD-3 series. To further reduce distortion a large Magnet ID faraday ring has also been included
We borrowed some technology from our large high-excursion woofers and incorporated a hyper-extended pole-piece into the SD-3 line. This helps to prevent voice coil rocking & related damages at high levels of stroke Ð since the SD-3 has such a soft suspension and shallow depth it would be more prone to this without the hyper-extended pole. But, thanks to our extensive experience in building high-stroke subwoofers we were able to incorporate the ideal solution.
The parameter set has been optimized for very small sealed enclosures for this line. While they can operate in ported boxes these woofers feature a very soft suspension so will not tolerate high levels of abuse in large, ported enclosures.
Under-Hung low distortion motor topology
Solid pole piece with chamfered edges
Black Aluminum 2.5Ó voice coil former for superior heat dissipation
High Temperature 8-Layer copper voice coil wire
Large aluminum faraday ring (Magnet ID)
Spring Loaded Terminals
Stitched-On Tinsel Lead Wires
Optimized for small sealed enclosures
Inverted Rubber Surround to reduce front-mount depth
High strength cast aluminum frames (8Ó model features US Patent D691595)
Features & Technology:
Size: 20 cm / 8 inch
Power: 300 watt RMS
Impedance: 2×2 ohm