Midrange driver failed twice

Archived from groups: rec.audio.tech (More info?)

tchelvam@hotmail.com wrote:

> Hi,
>
> My left 3 way loudspeaker's Midrange driver failed twice within 1 week.
> The amplifier wasn't the cause. It looks like the crossover but I am
> not sure. Can someone tell me what could be the problem and is it
> possible to get the alternative driver and crossover from any High End
> DIY supplier for Loudspeakers?
>
> Thanks.
>

What is the failure mode?

Archived from groups: rec.audio.tech (More info?)

tchelvam@hotmail.com wrote:

> No sound, no hiss nothing.Looks like internal. Maybe voice coil. But
> when I used a multimeter I saw a closed circuit. Anyway, I am a layman
> so maybe that's not a correct way to test a broken driver.
>

If you disconnect the driver and find that the voice coil is not an open
circuit, there is no reason to believe the driver is bad; specially if
the cone moves during this test. (VOMs put DC voltage through the device
under test when measuring ohms.)

If you know the amp channel is good because the other speaker works on
it and the "bad" speaker was repaired by replacing a driver, then there
certainly is something wrong in the "bad" speaker. If you have the
original driver, check the continuity of the voice coil as it may still
be good.

From what you have described, an intermittent part in the crossover
seems the most likely problem. Post details on the speaker, brand &
model#, so it can be identified and someone in this group may know
exactly what is wrong.

Archived from groups: rec.audio.tech (More info?)

tchel said:

>My guy who checked the Amp told me it could be either the crossover or

>the replacement driver was defective. Having said that, I can confirm
>that the driver was dead when when I switched to my right speakers. So

>something caused the driver to fail. One option that is left for me is

>to transfer my good right driver to left and see if it fails. But for
>now, I have to wait to see if the manufacturer is going to honour the
>warranty first before I start to experiment. (The tweeter and and Sub
>works fine, in fact the sub plays more frequencies when the middriver
>is dead)


My hunch would be the xover, probably a capacitor.

Try the new driver in the other speaker sysyem and if it works, you
know it's the xover.

Archived from groups: rec.audio.tech (More info?)

Robert Gault wrote:
> tchelvam@hotmail.com wrote:
>> My guy who checked the Amp told me it could be either the crossover
>> or the replacement driver was defective. Having said that, I can
>> confirm that the driver was dead when when I switched to my right
>> speakers. So something caused the driver to fail. One option that is
>> left for me is to transfer my good right driver to left and see if
>> it fails. But for now, I have to wait to see if the manufacturer is
>> going to honour the warranty first before I start to experiment.
>> (The tweeter and and Sub works fine, in fact the sub plays more
>> frequencies when the middriver is dead)
>>
>> Model: Mission 783. The drivers are believe to be custom made Audax
>> for Mission.
>>
>> Thanks.
>>
>
> The point is that there are two modes of failure for a driver. 1) Burn
> out the voice coil. 2) Break something because of excessive motion of
> the coil in the gap. Just because you don't hear anything from the
> driver does not mean it has failed.
>
The voice coil can also warp to the point at which the windings jam in the
gap and short out. It will then read a dead short with a VOM. Usually you
can tell if this is the case because gentle pressure on the dustcap will
produce no movement of the cone (try it on a known-good driver to get the
feel for it).

> It is not clear how a crossover could cause a mid-range driver to
> fail. That's why you should be sure that the drivers really have an
> open (infinite ohm) reading before throwing them out.

A shorted blocking cap could pass low frequencies to the driver....

jak
>
> If there is a loose wire or connection in the crossover, you could
> have intermittent sound from the mid-range driver. Messing with the
> speaker could start things up again making you think a new driver
> repaired something.
>
> While testing the various parts of the crossover may be beyond your
> capabilities, you should be able to find bad solder connections.