speaker level sub hookup on class D?

Outputs on Icepower amp behave the same way as outputs of the bridged amplifier - both terminals of each output are active. If your Velodyne has both speaker level inputs referenced to same level (internal GND) it will short Icepower amp. This connection is only possible if Velodyne speaker level inputs are balanced or floating/isolated.

I second what Kal said - why bother? You have line level mono input and line level stereo inputs on your Velodyne. As long as you have mono signal out or two stereo outs you can make safer and better connection.

Magfan, ICE is 'full bridge' meaning that load (common mode choke, zobel network, speaker) is placed across the bridge of four Mosfets while two other arms of the bridge are GND and +VCC. At one state two Mosfets on opposite (diagonal) arms of the bridge are conducting while at the other state two other arms are conducting. Speaker is always connected between +Vcc and GND but polarity changes (at about 0.5 MHz). Zero output is when Mosfets switch at 50% duty cycle (perfect square wave). Each of the speaker wires is switched between +Vcc and GND making voltage (since it is filtered by common mode choke and zobel) equal +Vcc/2 hence difference between them is zero. Placing DC voltmeter between any terminal of the speaker connected to ICE amp (with no signal) and earth ground will show half of the module supply voltage. In case of largest 1000ASP module it should be +40V since module has +80V supply. 40V vs. GND is still safe voltage but I would not touch such terminals with wet fingers or tongue.

Half bridge, used in Hypex (Channel Island), has only two Mosfet switches but two opposite voltages +Vcc and -Vcc. One speaker terminal is always connected to GND while the other is switched between +Vcc and -Vcc according to duty cycle.

Each configuration has advantages but one obvious disadvantage of 'full bridge' is inability to further bridge amplifier (for more power) or use for some subs.

Magfan, both 500ASP and 1000ASP have two voltages 50V/80V and 80V/120V respectively, where first (lower) voltage they call "preload". I'm not sure what it means but from my calculations they use higher of two voltages for output stage.

Magfan, you're right - I forgot about it.