Ok,

The manual says "Any number of SE175 or SE250 modules may be seriallybridged together, as long as they are in the same family. However, SE175 modules cannot be bridged with SE250 modules."

So, this seems to say that I could bridge all 6 channels of my SE6175 together, not that I want to. I only want to bridge the back two.

Next it says "Use a high-quality ground-loop isolator in series with the RCA input of each SE175/250 module to be bridged. Using a low quality isolator will decrease and distort low-end bass performance (between 20 and 60Hz.)

This is odd, but seems easy enough to do.

I'm not familiar with the term "serial bridging" but thankfully there is a diagram.

So, it shows the positive speaker lead going to the positive terminal on channel "A", and the negative speaker lead going to the negative terminal on channel "B". Traditional bridging.

But, it also shows a lead from the negative terminal of channel "A" directly to the positive terminal of channel "B."

I assume this is what is meant by serial bridging?

Finally, it only shows a ground loop isolator being used on channel "B", could this be an oversight?

Hopefully someone that installed Blade back in the day will remember something.