speakers reborn as LS3/5a clone

[mlsstl]

One of my old speaker systems consisted of a set of KEF drivers I brought back from London in 1979 - a set of veritable T27, B110 and B139 units that got put into a set of cabinets. The tweeter and midrange went into a small custom built cabinet the size of a LS3/5a and the woofer went into a transmission line box. The whole thing had an active crossover and was tri-amped. Evenutally I moved on to other speakers. The B139 drivers were sold on eBay but I hung onto the small boxes.

A couple of months ago I decided to dig these out of the basement and make them my computer speakers. Since they had no internal crossover, I just got a cheap 3KHz crossover from Parts Express. Not too bad but I knew they could really sound much better.

So a couple of weeks ago I ran down the schematic for the original LS3/5a's and ordered the parts. I had to etch the circuit board from scratch and hand-wind one of the inductors since I couldn't find a pre-wound 0.24 mH coil. (That's the green-wired one at the upper left corner.)

Anyway, I finished building and testing them this afternoon and got them installed. While the speakers take a hit on efficiency, the sound improvement is stunning. It is like a deep stage has opened in between the speakers. It really sets you back a step to hear this type of sound coming from your desktop computer. (I'm using a Trends Audio amp, not too much power but great quality and more than enough for the desk since this is a seriously "near field" monitoring experience.)

A fun project and a great re-use of some old, but great speakers.