For the New Lab, I thought it would be a good time to improve the sound system a bit. I have a pair of Kef Concerto speakers from the 70s, I have the power amp boards from the project a couple of years ago, I have a donor home cinema amp or two so some bits come together.
I was sorting out someone's lousy sounding hi-fi on Hayling last year or so, where they said the sound was muffled. It turned out that their speakers were bi-amp capable, and they were only driving the bass part. I'd wired them in properly, and that thought was in the back of my mind. I liked the sound of those bi-amped speakers, and it stuck with me. I did some research online, found that there were people who did recommend tri-amping as well as bi-amping for smaller bookshelf-y sized speakers, so I was ready for it.
Then an offer from Seeed studios dropped in the mail box for 5 10cm square boards for about a tenner including postage, so I went for it.
This is the Linkwitz filter - two required, one for each channel. The idea is that it is fed from a regular 700mV kind of level output from a pre-amp or mixer, has some fairly steep active filters that provide the low end, the mid-band and the high end signals to discrete power amplifiers, which are then wired directly to the speaker drive units (maybe with an inline fuse in a vain attempt to save the life of a speaker cone if the amp decides to fail in dramatic fashion).