ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
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Oh WOW! This is a dream setup G7?
You deserve a much better exposure and I would post your pictures to this thread.
https://archivedforum2.beoworld.org/forums/t/227.aspx
I'm in love!
Good morning, everyone!
As promised to Rich, I am back with the results of my research with these famous ITT midrange found in the Beobox M70, M75 and M100. But first, I would like to highlight the great generosity of our nice Rich who gave me two of these rare midranges. You see, he could have posted them on Ebay or something, but no, he gave them to me for free and also included a nice letter to my attention.
Thanks again Rich, it's greatly appreciated and you should receive something in the next few days typically French Canadian!
My sincere thanks again Rich!
So back to the original question of whether noisy ITTs can be repaired or replaced? Unfortunately there is no simple answer to this question, as the answers can be multiple. However, we can exclude a possibility immediately in case the voice-coil is permanently damaged and the entire midrange replaced or sent for voice-coil repair.
In order to best describe this midrange driver, the ITT is a sealed 2" soft dome driver that fits perfect for bass reflex or sealed enclosure boxes to reproduce midrange frequencies up to 4000Hz with a 225Hz resonance frequency.
Construction: The voice-coil is glued to the back of the soft dome and the assembly is glued precisely to the moulded plastic faceplate. The facade is then assembled to the magnetic metal structure. This assembly requires a lot of precision in the manufacture of the components and also in the assembly.
So here's the ITT midrange cut view (the best I could draw it… ;-)
Blue: moulded plastic front
Red: Soft dome and voice-coil
Pale green: exterior metal structure
Dark green: core
Continued...
Sorry, I forgot to mention the most critical part which is the yellow plastic ring that seals the soft dome and internal chamber from the outside.
Case #1: If a driver is badly sealed, which was my case for one unit, the air moved by the woofer, in a sealed enclosure box, can reach the underside of the dome and make it to vibrate and worst, unsealed the dome from plastic front thus creating a hiss noise.
Here you can see a dab of glue creating a gap allowing air to reach the internal chamber and soft dome
Case #2 to follow...
Case #2: Depending on the manufacturing period, there could be deterioration inside the voice-coil. On my two units, a plastic membrane covered the inside of the voice-coil, possibly to protect the cardboard against friction and this membrane blistered in places of the inside diameter. This detached membrane rubs against the core and creates a fuzz-like sound. On the other hand, the units generously offered by Rich, did not have this membrane therefore this problem does not affect all the ITT midrange of this series.
The solution is to gently remove this membrane by cutting it, using a surgical knife, at the base of the diameter very close to the dome and above the glue joint, then gently remove it.
Case #3 to follow...
Removal of the plastic membrane...
The membrane is extremely thin so you don't need to push hard on the knife to cut it; just a light pressure is enough. We don't want to damage the voice carton, comprende amigo?
Hello,
I am hoping to resurrect this thread. I am in search of one (or two) M70 Phase Link Mids. One of mine is seized and i am not sure if its' better to rebuild or replace.
Any help is appreciated.
I am in Chicago, Illinois, US.
Thanks
The phase link is the 4” cone (third from top) and the midrange is the 2.5” dome (second from top). I suspect a seized phase link would be a straight forward fix. Can’t speak to a dome driver repair.
My repair guy in Chicago tells me the driver is most likely beyond repair if the coil is burnt or the magnet poles have shifted too much. He is very good so i will take the driver to him for a consult. In the meantime i am in search of an OEM Phase Link driver that could be more of a "plug and play" situation.
Anyone out there with spare / extra drivers available?