The Spec 4 is a tricky one. The amps use pretty standard speaker relays available at Mouser, and possibly others. But the spec 4 design, using their pre/control amp adds 2 more much bigger speaker relays (that are turned on and off by the speaker switches). The design is that the speaker outputs route back to the pre/control amp, and that is where the speaker wires connect to. Those big one I found get dirtier than the smaller ones. But unless the amps had heavy DC on the speaker outs, the contacts are usually dirty, and not pitted. I use a pencil type eraser to polish the contacts (both sides) and spray with deoxit gold. I let it sit a few minutes, and blow off all excess with my air compressor.
I know other like to replace the relays, but I only do that if they have pitted contacts. If the contacts are only tarnished (most of the time), I clean and polish them.
