Just in case anyone else runs into the same issue:
I recently repaired a vintage Klein + Hummel OY multiway active studio monitor that made a weird squeaking sound at power on. It took me quite a while before I had figured it out, but it was only due to the midrange loudspeaker being broken down. One of the flexible wires that are supposed to make contact with the voice coil was not making any contact.
The OY has two amplifiers, one for the low frequencies and one for midrange and high. The crossover between midrange and high is a passive LC circuit. With the midrange loudspeaker disconnected, the LC low-pass for the midrange turns into a high-Q LC series network. Such a weird load made the amplifier instable, albeit only at start up.
Anyway, I managed to solder the flexible wire to the voice coil wire and to fixate the connection with nail polish (there are probably better solutions than nail polish). It works fine now without any squeaks.
I haven't a clue whether this is the correct forum, my apologies if it isn't. The OY is a professional loudspeaker, but neither meant for instruments nor for public address.
I recently repaired a vintage Klein + Hummel OY multiway active studio monitor that made a weird squeaking sound at power on. It took me quite a while before I had figured it out, but it was only due to the midrange loudspeaker being broken down. One of the flexible wires that are supposed to make contact with the voice coil was not making any contact.
The OY has two amplifiers, one for the low frequencies and one for midrange and high. The crossover between midrange and high is a passive LC circuit. With the midrange loudspeaker disconnected, the LC low-pass for the midrange turns into a high-Q LC series network. Such a weird load made the amplifier instable, albeit only at start up.
Anyway, I managed to solder the flexible wire to the voice coil wire and to fixate the connection with nail polish (there are probably better solutions than nail polish). It works fine now without any squeaks.
I haven't a clue whether this is the correct forum, my apologies if it isn't. The OY is a professional loudspeaker, but neither meant for instruments nor for public address.
In these situations I usually put a drop of contact cement on the wires as I don't know where to get that black goop they use for gluing. Contact cement works good because it's flexible.
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