Here is another update on my L100 project...
I mounted the new upgraded Murphy crossover board to the back panel, drilling the top holes with a Milwaukee 1/4 in right angle adapter I got from Home Depot (part number 48-32-2100) with a Craftsman drill bit with a 1/4 hex shank. I used some strips of foam insulation behind the board to stop it vibrating. You can see the new JBL spec crossover L-pads in the top of the picture, this was mounting using the orignal screw holes in the baffle (for the moment, I might fill these when I refinish the cabinets).
Here is a close-up of the terminal and switch plate. I tried to run every common or ground wire back to the negative terminal in a kind of star-earth way, that's why there are so many wires : 2 to the JBL spec crossovers, 3 to the Murphy crossover, 2 to the woofer and tweeter, 1 to the midrange switch.
I also replaced the old fibreglass insulation with some new acoustic wadding or cabinet damping.
Here is a view of the back panel, looks more business like now doesn't it?
And here they are fully assembled. I had to pull out one of the tweeter domes with a pin, so I sealed it using some "Wet Look" speaker paint from Parts Express. I did the woofer caps as well, since I had to remove one.
Before everything was buttoned up, I was able to play each driver on it's own, just to make sure I wired the switches the correct way. This revealed some interesting results...
The woofer reproduces a lot more midrange frequencies using the JBL crossover, these are rolled off with the Murphy. From the factory, it has no crossover components of any kind, relying on it's natural roll-off. Likewise, the tweeter reproduces more midrange frequencies with the JBL crossover than the Murphy. I hate to point the finger at the little guy in the middle, but I've already mentioned the midrange reproduces a lot more treble than it should in JBL crossover mode. What is also interesting is it seems to get more low frequencies as well. This was noticed using nothing more high tech than some dust that just happened to be sitting on the cone. With just this driver connected (hence no vibration from the woofer), switching from Murphy to JBL caused the dust to bounce off the cone. Actually, the speaker doesn't sound all that bad with just the woofer and tweeter connected using the JBL crossover, in a loudness button "boom and tizz" kind of way, less midrange.
Connecting all the drivers and placing them back in the cabinet, it is easy to hear the difference when switching crossovers. Going from high to low, and with the switches set to the Murphy crossover, here's what happens. Switching the tweeter over from the Murphy to the JBL crossover, now there's more midrange. Switching the midrange now there's more midrange and even more treble, switching the woofer over adds even more midrange. It's easy to see why this speaker is impressive when you first hear it, there's so much attack because all three drivers are having a go.
What's weird is the midrange interaction with the woofer. I don't know what you call it, but we all know the sound a pair of out-of-phase speakers make. That weird sound like it's coming from behind you, or inside your head, it's kind of hard to describe. I've been to peoples houses (who should know better) and told them one of their speakers is wired back to front. Of course they deny it, then when they check, it is. I've been to HiFi shops, record shops, heard car systems, and can easily tell when a speaker is wired up wrong. Well, I had each of these L100s lying on their backs on the floor with a piece of wood propping them up so I could switch between crossovers. Switching from the Murphy to the JBL crossover on the midrange, with the woofer set on the JBL crossover, sure enough you can hear the fact that the midrange is wired out-of-phase. This obviously isn't helped by the fact that they have such an overlap. This doesn't happen using the Murphy crossover.
These are just initial observations, I need to get them set up properly and get down to some serious listening...
