Yesterday I fixed up the 2441s. I put a new Radian diaphragm into one, and put the JBL one from that into the other. For some reason, the Radian diaphragms are a tighter fit than the JBL ones.
That’s the JBL diaphragm in situ. It has a circle in the middle, which the Radian doesn’t have, and the diamond pattern around the edge that is a 2441 thing.
The problem was caused by some distortion, perhaps from the diaphragm rubbing. In the end I fixed one simply by using the Radian replacement, and the other by only using three rather than eight bolts. Any more and it would vibrate.
I tested them by running fixed frequencies and sweeps from my phone and through a little class D amp. The Bink test CD is great for these sweeps and stuff.
I think that using the 2441 should really help reduce the distortion - running the Rectums so high is fine, but not through that horn with a sharp turn. I think…
Jesus, the rectums are 14kg each, I’d forgotten how heavy that is!
I have been fiddling with my rectum today. I’ve made the back box bigger, and they now use bolts rather than clamps I’ve borrowed off Pete for two years!
They are fucking massive and heavy. I reckon they’ll be fine down to 100Hz. Some people use 6" drivers lower than that without horns, so I reckon they’re good for it.
Pics tomorrow. I won’t be able to install them until I have help though, they’re just too heavy.
I fiddled and faffed with them, fixing up the issues that had been present since @coco and I made them - crocodile clip issues mostly. Then I had a more serious problem.
Like the 2441s, it vibrated, as tested when running a sweep through it (and a 120Hz warble, which I have just discovered and rather like for this kind of test.
I have determined that the rattle is caused by the rubber that connects the main curved part of the diaphragm to the round metal holder vibrates against the wood that holds it in place. Essentially, we cut the hole too small, not allowing for the movement of this part.
I can fix this by routing a bit of the wood away, maybe 2mm deep, but this might (will) fuck up the air tight seal. That said, that might not be too much of a problem.
Alternatively I could remake them from scratch, but that doesn’t appeal much.
Would a round-over or chamferred router bit not help with the clearance without affecting the seal? Don’t really know, fucked if I can visualise what you’ talkin’ 'bout Lewis! .
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