On-Stage SSA21 Subwoofer Adapter

The SSA21 is a mounting adapter designed to convert a M20 threaded subwoofer pole socket into a standard 1-3/8" (35 mm) unthreaded pole socket, allowing you to use standard unthreaded speaker shafts with M20-equipped subwoofers.

Many modern powered subwoofers feature threaded M20 pole mounts to prevent speaker pole wobble. The SSA21 allows you to thread this adapter directly into the subwoofer so you can continue using traditional, non-threaded 1-3/8" speaker poles or stands without buying an all-new threaded pole.

It is constructed from heavy-duty, solid steel with a durable black powder-coated finish designed to withstand heavy stage loads, frequent screwing/unscrewing, and road use.

It features a threaded M20 male stud at the bottom. You simply thread the SSA21 clockwise directly into your subwoofer’s M20 top socket until hand-tight to create a solid, stable base for your speaker shaft.

Yes, it uses the industry-standard M20 x 2.5 mm thread pitch found on most popular subwoofers from brands like QSC, JBL, EV, Yamaha, and Electro-Voice.

No. The bottom M20 thread locks securely into the subwoofer chassis, and the deep 1-3/8" top cup provides full vertical support for standard speaker shafts, ensuring your satellite speakers remain straight and secure.

Yes, its low-profile design allows it to remain threaded into the subwoofer's top socket permanently or during transport, though it can easily be unthreaded if you use a protective subwoofer cover or bag.

Because it is made of solid steel and screws directly into the subwoofer's internal frame, its weight capacity matches or exceeds standard speaker stands, comfortably supporting full-range PA speakers up to 100+ lbs (depending on the subwoofer's rating).