Lockdown Experiments

I made another baffle and fixed the driver and bowl to it, no horn though. Putting the mic just inside a slot gave this (average of 4 measurements)




Just a hint of a dip around 2kHz, so possible not what I'm looking for, but certainly some room for improvement. I made a round bung for the centre of the baffle, with plasticine to fit around 3mm from the driver dust cap. This is the result




Some gains higher up, and still that little dip. Next I added more plasticine to fill up more of the front chamber




This was the result




A loss lower down, small gain higher up. Next I filled up the only space left by adding a ring around the outer edge




This was the result




The response is getting flatter. I think this has taken plasticine technology far enough, so next job is to make something more accurate and hopefully repeatable.

I think it is your slot arrangement. Is this the 6" transducer? At 2khz half of the wavelenght is roughly 8,5 cm.  The pairs of slots being parallel obviously doesnt help. Maybe try some radial slots? I mean lines from the center outwards. 

bob4 wrote: I think it is your slot arrangement. Is this the 6" transducer? At 2khz half of the wavelenght is roughly 8,5 cm.  The pairs of slots being parallel obviously doesnt help. Maybe try some radial slots? I mean lines from the center outwards.

Yes this is the 6" driver. I see your point and would expect that cancellation if I measure at some distance from the baffle, maybe I should have done a measurement to check that. Distance between the slots is 58mm on the inner edge, 89mm on the outer edge.

I'm not sure if the photos show the exact arrangement, each slot feeds an individual mini horn, these horns bend around so the mouths end up in a vertical line. The reason I chose the slot positions is to make the bends as smooth and simple as possible, with the bend being in the shorter side of the horn and with minimal twisting. It was also to keep the mini horns as short as possible, as adding length lowers the flare rate which may reduce the loading at higher frequencies. I'm not sure how I could use radial slots with this arrangement.

J7's a bit different....

Look like BMS oem’s to me. Either that or some shameless copying is going on 

I tested the N151M-8, its very close to BMS 4540nd in sound and response, im not 100% but i think Eminence may get the diaphragms from BMS, they sound very very similar.