Stored all the time, in an on the street van, and obvious mold spotting of
the cones.
Actual problem is 8//8 + 8//8 wiring with 1 driver failing unnoticed in a
gig and then followed by the other strained one, oddly at low level output,
in practise session.
Well I assume that is the scenario.
At least I can bypass the failure pair with some high W droppers for them to
practise next week, before replacing properly.

Could dampness have played a part in the failure?
Owner obviously handles the cabs with respect , so I have to believe that he
does not overdrive them (from the original matching bass amp ) - blurb says
600W cab

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Meat Plow wrote in message
...
On Sat, 05 Jan 2008 14:12:58 +0000, N Cook wrote:

Stored all the time, in an on the street van, and obvious mold spotting
of
the cones.
Actual problem is 8//8 + 8//8 wiring with 1 driver failing unnoticed in
a
gig and then followed by the other strained one, oddly at low level
output,
in practise session.
Well I assume that is the scenario.
At least I can bypass the failure pair with some high W droppers for
them to
practise next week, before replacing properly.

Could dampness have played a part in the failure?
Owner obviously handles the cabs with respect , so I have to believe
that he
does not overdrive them (from the original matching bass amp ) - blurb
says
600W cab

Dampness as in high humidity isn't a likely culprit. Voice coils don't
corrode or host molds. Did you inspect the magnet structure for corrosion?
There is a remote possibility that the magnetic pole inside and around the
voice coil could corrode but I seriously doubt it would cause a failure
that couldn't be previously detected as a rub. My guess would be either a
defect in the driver or the cab was overdriven and the client isn't being
honest. I used to see that all the time when I worked on a lot of amps and
cabs.


Agree but I won't be inspecting the voice coils until after replacing the 2
failed units. Reassembled with a number of W/W droppers in there for the
moment.
Moving the cones/feeling by hand shows no grittiness or scratchy noises so
no burst coils, no burning smells around them. There is a few Mohm across
one of them. Other than they have copious grey mold spots on the outer face
of the the cardboard, they and skirts etc look fine.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:

Agree but I won't be inspecting the voice coils until after replacing the 2
failed units. Reassembled with a number of W/W droppers in there for the
moment.
Moving the cones/feeling by hand shows no grittiness or scratchy noises so
no burst coils, no burning smells around them. There is a few Mohm across
one of them. Other than they have copious grey mold spots on the outer face
of the the cardboard, they and skirts etc look fine.

Sounds like corrosion could have set in. Rip out the cones/coils of the
the failed units. They have to be reconed or replaced anyway...and will
provide proof-positive of the cause. The rot could have happened at any
part of the electrical/mechanical chain. I'd first suspect the flex
connection where the wire is soldered to the speaker terminals, running
to the cone (that might actually be repairable)--but with that much mold....

jak

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Meat Plow wrote in message
...
On Sat, 05 Jan 2008 19:47:55 +0000, N Cook wrote:

Meat Plow wrote in message
...
On Sat, 05 Jan 2008 14:12:58 +0000, N Cook wrote:

Stored all the time, in an on the street van, and obvious mold
spotting
of
the cones.
Actual problem is 8//8 + 8//8 wiring with 1 driver failing unnoticed
in
a
gig and then followed by the other strained one, oddly at low level
output,
in practise session.
Well I assume that is the scenario.
At least I can bypass the failure pair with some high W droppers for
them to
practise next week, before replacing properly.

Could dampness have played a part in the failure?
Owner obviously handles the cabs with respect , so I have to believe
that he
does not overdrive them (from the original matching bass amp ) -
blurb
says
600W cab

Dampness as in high humidity isn't a likely culprit. Voice coils don't
corrode or host molds. Did you inspect the magnet structure for
corrosion?
There is a remote possibility that the magnetic pole inside and around
the
voice coil could corrode but I seriously doubt it would cause a failure
that couldn't be previously detected as a rub. My guess would be either
a
defect in the driver or the cab was overdriven and the client isn't
being
honest. I used to see that all the time when I worked on a lot of amps
and
cabs.


Agree but I won't be inspecting the voice coils until after replacing
the 2
failed units. Reassembled with a number of W/W droppers in there for the
moment.
Moving the cones/feeling by hand shows no grittiness or scratchy noises
so
no burst coils, no burning smells around them. There is a few Mohm
across
one of them. Other than they have copious grey mold spots on the outer
face
of the the cardboard, they and skirts etc look fine.

Bass speakers often fail without having a rub or burnt smell. I blew one
Eminence 10" in my 4x10 Fender bass cab in the 18 years I've owned it.
I'm sure that it was caused by the demand I imposed upon it with a 1000
watt RMS Crown. No burn or rub just a fracture of the the wire in the
voice coil.

I hope there is a good technical reason (not known to me) why Warwick wires
them as
8//8 + 8//8
I would have wired them
(8+8) // (8+8)
so if one failed then no other failure and it would be possible to continue
to end of gig, but as driving 16 ohm, with less power.

If no one realises that only 2 of the 4 are working ,then - what the hell!
It would unlikely to be straining the amp

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/