- Oct 18, 2009
the drivers: ortho SFI 120 ohm
the foster home: AKG K240 Sextett LP
Let's start with the disassembly...
1. Here's the shiny not-so-new Sextett that I purchased without drivers
2. Use a thin hobby knife to peel off the badge. The badge is a thin metal piece, so be careful not to bend it. There may be some glue residue beneath which obscures the screw. That's ok, just use your knife or a screwdriver and gently scrape away until you can see the screw. Actually, don't even remove it all; just take out enough that you can reach the screw and turn it, the remaining residue will hold the screw partially in place so you won't lose it. You know what they say about little screws...
3. Lift out the cap and screw to reveal... another screw! I think there's a joke here about a screw that screws into another screw in the Sextett, but let's be adult about this. Take this one out too and the cup will come loose. The headband elastics also attach at this point; note the slight ridge on the headband end. When you reattach the headband, make sure the elastics are resting on the ridge and not the screw. Nothing worse than having something snapping your ridge.
4. Disassembled picture; if you look closely you can see that those are not original elastics. They are hair ties that were overachievers, so they were cut short and knotted to put them in their place. You can hide the knot inside the cap during reassembly to hide your dirty dirty deed.
5. Lift out the rear cup and you'll see the mounting bracket (the thing with four holes), which is attached to a ring gimbal, which is attached to the front baffle. This neat assembly is what gives the cups their seemingly circular range of motion. The two side holes fit into the mounting tabs on the rear cup for stability, the bottom hole is where the wires go through. The centre hole is from the screw, where the screwing happens obviously
6. Using a knife or fingernail, pry off the outer ring. I found that there was a small notch on one side which made it easier to get my finger in. Wiggle gently.
7. Gently pop off the bracket. It will be easier to bend the ring gimbal than the bracket as the gimbal is softer. Be careful not to squeeze too hard though; this is a delicate thing after all. There's a lot of deteriorated crud inside. This is what happens when you don't clean your sextett regularly
8. You can also pull off the front grill. Either pry up the edges from the front, or gently push down the middle from the back. I said gently! If things bend rather than push through, you may need to rethink your exit strategy.
9. Here are the naked diffusers that give the Sextett its name. Sometimes they come in different colours. Please resist the urge to poke them. I know it's exciting when there are three pairs in front of you, but do control yourself. You'll get a chance to open things up for them later.
10&11. More shots of the crud. You really should remove this as it's just going to disintigrate
12. Here's the gimbal assembly with all the crud removed. Note the inner 35mm diameter wall, this is where the driver normally goes. Since the driver I want to use is 40mm, it cannot be mounted here. I decided here to mill out the 35mm wall, then opted to mount the driver into the ring gimbal which I figured would be easier than trying to glue it down to the baffle.
13. A bit later with a dremel and voila, all reamed out and noticeably wider and a little rough around the edges
14. Here's the SFI driver sitting on top of the gimbal. There is maybe 1mm is clearance here. I considered cutting out small slots in the ring gimbal so the leads could settle deeper and let the driver sit deeper in the ring, but I was not comfortable weakening the ring.
15. Here's the front baffle all by its lonesome because that hussy gimbal ran off and filled its hole with a big SFI.
16. But it turns out that the gimbal is a little too loose of a fit for the SFI, so a thin layer of hot glue is applied. Drop down a very small bead then use the hot nozzle to wipe a thin flat layer around the inner edge
17. But make sure to rough up that inner surface with some sandpaper or a dremel first, otherwise the glue layer slips right out. Oops. We wouldn't want any accidents now.
18&19. Then slide that baby in. You might have to push a little harder since the fit is much tighter now. As always, be gentle. If you break it, you don't get a second chance.
20. Depending how comfortable you are with bending the gimbal mount tabs on the front baffle, it may be easier to mount the gimbal first, then the driver later. If the driver is mounted first, the gimbal becomes inflexible and is very difficult to snap into the front baffle. After that, reattach the bracket. This is also going to be an extremely tight fit, and I had to dremel the mounting pegs a little shorter and also use a pair of pliers to squeeze everything down so I could reattach it. You will lose the one axis of freedom here because the driver presses up against the bracket so it cannot rotate freely. If one were to mount the driver deeper in the gimbal, I'm sure we could regain that freedom, but as I mentioned before this will require some very careful drilling of the gimbal. If I were to attempt this project a second time I would probably do so, but right now it's all attached and I would really rather not attempt to disassemble it at this point.
21. There is a tiny bit of clearance between the bracket and rear of the driver. This isn't ideal, but at least there's some breathing room. I plan on putting some micropore tape or perhaps sticker felt on the underside of the bracket just to absorb some of the rear projection from the driver.
[more to come]