Input to subs

JL Audio LoC-22 - line output converter may work for your setup.

Ayre A7e speaker connectors > JL Audio LoC-22 > Velodyne SMS-1 line level input.

The JL Audio LoC-22 featured differential-balanced input architecture and compatibility with most amplifiers. It is a active speaker level to line converter need a 12V dc power supply.
You can contact JL Audio to confirm if their LoC-22 compatible with your Ayre A7e.

JL Audio Customer Service: (954) 443-1100

Maybe. But why make it harder than it has to be? The elegant solution is what I did, a simple 2 resistor mod to the amp. https://systems.audiogon.com/systems/8367 See picture #26.  

Or if you don't want to change your amp then you can use the same two resistor circuit connected between speaker outs and sub in. https://www.epanorama.net/circuits/speaker_to_line.html 

Or if you don't like that then just buy one of these  https://www.parts-express.com/car-audio/car-audio-installation-accessories/line-output-converters-co...