Aftershock-18 Powered Subwoofer Features

Aftershock-18 Powered Subwoofer Cabinet Features

We sell a ton of these active 18 inch subwoofers and as you can imagine, we field a lot of questions about the features of this subwoofer. Continuing our endeavor of excellent customer service, we put together a list of the top 8 things you should know both before and after you purchase a Seismic Audio Aftershock-18 Powered 18 Inch Subwoofer Cabinet. Enjoy this handy resource and as always, if you have a question, please give us a call!


    1. The inputs on the Aftershock-18 are XLR-1/4" TRS combination inputs. They will accept the "Male" end of an XLR cable or a 1/4" plug. Notice that there are 2 of these inputs, a left and a right. You will command more performance from the sub if you input into both of these. THESE ARE NOT SPEAKON JACKS.

    1. If you input into both the left and right XLR-1/4" TRS inputs, then you will activate both XLR outputs, as well as the powered Speakon outputs, located towards the middle of the amplifier.

    1. You can use the powered Speakon outputs to power a set of passive full range 8 or 4Ω main speakers. The Speakon outputs operate at 150W RMS @ 8Ω, 200W RMS @ 4Ω, each channel.

    1. If you input a full range signal to the Aftershock-18, it will output the same signal via the XLR outputs (to allow you to daisy chain the line level signal to another powered speaker/sub/power amplifier) and the powered Speakon outputs.

    1. There is a Volume knob and LPF (Low Pass Filter) knob that controls the 18" woofer. The LPF controls what frequencies the 18" will or will not play, depending on where you set it to (40 Hz to 200 Hz)

    1. There are 5 knobs that control the "satellite" speakers (a.k.a. the passive speakers) connected to the powered Speakon outputs. These are a volume, 3 band EQ (low, mid, high), and a balance/pan knob.

    1. There is a red "power selector" switch located just below the On/Off switch. The number "115" needs to be visible on the switch itself. This switch is designed to allow customers on a different power grid, such as the one in Europe, to switch the device without having to use a converter. In the US, the switch needs to say "115"

  1. There is a fuse, situated in a caddy, that is part of the power cord receptacle. There is an outline/picture of a fuse. With the unit unplugged, you can use a pen or key to pry out this caddy, should the fuse need to be change. It is a 10 Amp, 250 Volt, "Fast-Blow". We carry them on the site, product code AmpBulb.