The SD-3 series is Sundown Audio’s premier sealed box offering. They 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 whilst still maintaining a large window of mechanical cushion (about 2” p-p maximum mechanical travel for all models). The SD-3 is not considered to be an “ultra-shallow”, 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 – this reduces the space required in front of the woofer to about 1” total (we suggest 1.25-1.5” when possible for the best sound). So, despite not being an “ultra-shallow” woofer, they have an effective total depth requirement of about 2” 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 – this means that the voice coil is shorter than the top plate so the amount of winding in the gap doesn’t change at all over the centre portion of stroke – in this case featuring a 1” thick top plate and ½” 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 and 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.
Sundown Audio borrowed some technology from their 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 – 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 their extensive experience in building high-stroke subwoofers they were able to incorporate the ideal solution.
The parameter set has been optimised for very small sealed enclosures for this line. Whilst 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.
Features & Technology:
- Xmax = 14.5mm one-way by 70% BL
- RMS Power = 500-watts (300-watts for the 8” model)
- Under-Hung low distortion motor topology
- Solid pole piece with chamfered edges
- Black Aluminum 2.5” 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
- Optimised for small sealed enclosures
- Inverted Rubber Surround to reduce front-mount depth
- High strength cast aluminum frames (8” model features US Patent D691595)