Replacing the mid dome has been discussed in this rambling thread ( http://www.diyaudio.com/forums/multi-way/93055-celestion-66-needs-mid-range-75.html ) but nobody yet has actually done so and posted about it.
This is one possibility--
Morel EM 1308 2-1/8" Dome Midrange | Parts-Express.com
...here's another ( better and much more expensive)--
ATC SM75-150 Midrange
ATC SM75-150S Dome Mid Measurement Data - ZeroGain Forum
also, (discontinued) Dynaudio d52 & d54 could probably be made to work well.
If you're trying to replicate the 66, then you'll need to work from the 66 schematic, not the 44. And if you end up using a mid other than a MD or MF, then you'll also need to make measurements & adjust the crossover.
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look in the Celestion 66 needs midrange thread
Almost everything you need to know is in the Celestion 66 midrange thread.
Yes, it is a very long thread, but if one wants to know things, one has to put in the time to look.
The 66 crossover schematic has been posted there.
Look on Page 17 in #162, then continue reading from there.
sba himself has posted Impedance plots for the MD500 drivers in that thread,
first on Page 36 in #354, and some more later in the thread.
Morel EM 1308 will work with the 66 crossover if a resistor is connected in Parallel with it to reduce its middle of bandwidth impedance minimum to the same middle of band impedance as MD500.
Use a 10 watt wire-wound resistor.
You will have to measure the Impedance of EM 1308 across its useable bandwidth.
Looking at the Morel specifications' plot it seems to be slightly higher than MD500, and that is good because it allows a single parallel resistor to be used.
Almost everything you need to know is in the Celestion 66 midrange thread.
Yes, it is a very long thread, but if one wants to know things, one has to put in the time to look.
The 66 crossover schematic has been posted there.
Look on Page 17 in #162, then continue reading from there.
sba himself has posted Impedance plots for the MD500 drivers in that thread,
first on Page 36 in #354, and some more later in the thread.
Morel EM 1308 will work with the 66 crossover if a resistor is connected in Parallel with it to reduce its middle of bandwidth impedance minimum to the same middle of band impedance as MD500.
Use a 10 watt wire-wound resistor.
You will have to measure the Impedance of EM 1308 across its useable bandwidth.
Looking at the Morel specifications' plot it seems to be slightly higher than MD500, and that is good because it allows a single parallel resistor to be used.
You're welcome.
Here's impedance data from my samples. As you can see, there's a lot of variation --
*********************
All of the drivers sound very good, but the pair I received a few weeks ago sound really superb --
*********************
Here's a FR plot of a mid dome, raw --
.....and connected to the crossover --
( SPL not calibrated )
Good luck!
Thanks Alan and sba,
Great information. I just have to wait for bits to turn up down here in SW France and a pal to start the cabinet project.
I already have a pair or 25s and 44s - this is a project to keep me out of trouble (if not out of pocket.....) during my retirement!
I will let you know how it proceeds.
Great information. I just have to wait for bits to turn up down here in SW France and a pal to start the cabinet project.
I already have a pair or 25s and 44s - this is a project to keep me out of trouble (if not out of pocket.....) during my retirement!
I will let you know how it proceeds.
Since you'll be making the cabinets, you have an opportunity to build a smoother baffle, which will result in a better response.
See-- http://www.diyaudio.com/forums/multi-way/93055-celestion-66-needs-mid-range-74.html#post2427632
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