Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

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

N Cook wrote:
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?


There shouldn`t be any crud in the magnetic gap!
However, I did once have an Old Altec Lansing that developed an
intermittent raucous scraping noise that was indeed something twixt
voice coil and pole. The only way I could cure it was to remove the
aluminium dust dome, and after vainly trying to clean it out with
various bits of card, sticky tape etc. I ran the speaker face down with
a low frequency sine wave for some time. Eventually a small chip of
aluminium dropped out.

I would expect a speaker is safest transported on it`s face, as I image
that way there are the least stresses on the basket from the weight of
the magnetic assy.

Other peoples mileage may vary (as they say)

Ron(UK)

N Cook wrote:

Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

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



Usually, speakers fail like this from being dropped and the magnetic
magnetic assembly shifts. When this happens the pole piece rubs against
the voice coil. Speaker is usually toast when this happens.

Also, if the speaker has been over excursioned from abuse, the rear of
the voice coil warps and rubs on the pole piece during times of higher
excursions causing a scratching rubbing sound.

I had a yamaha 4115 drop vertical once and it shifted the magnetic so
much that it froze the voice coil.

I had a grundorf trap that fell over that snapped the magnet/pole piece
off the cast frame.

Bob

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I have seen where something mettalic as small as a staple has been
attracted to the dome in front of the magnet making a disturbing noise,
but easiliy removed.

Bob Urz wrote:



N Cook wrote:

Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face
down.?

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



Usually, speakers fail like this from being dropped and the magnetic
magnetic assembly shifts. When this happens the pole piece rubs against
the voice coil. Speaker is usually toast when this happens.

Also, if the speaker has been over excursioned from abuse, the rear of
the voice coil warps and rubs on the pole piece during times of higher
excursions causing a scratching rubbing sound.

I had a yamaha 4115 drop vertical once and it shifted the magnetic so
much that it froze the voice coil.

I had a grundorf trap that fell over that snapped the magnet/pole
piece off the cast frame.

Bob

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News==----
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120,000+ Newsgroups
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=----


--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

Small particles could collect and be forced into the gap by dropping
where they will stack up an cause a rub issue. The magnetic assembly
shifting is usually when they are transported vertically. It's really
hard to shift the magnet face down. What I have seen, with high
compliance loose suspension, big voice coil drivers is the coil fall
out of the gap, then foul the voice coil former.

Remove the dust cap and have a look. It's all you can do at this
point. Sometimes Xylene or Acetone or Toulene can soften the glue to
permit removal, or you can use a razor blade.

Pull the cone toward you and see what is actually rubbing.

Debris can be fished out with masking tape, compressed air, shims,
etc.

If the gap is not symeterical and concentric, the speaker is toast. It
has to be reglued and remagnetized. Unless it is a holy grail speaker,
buy a new one.

If the former is deformed, maybe you can finesse it back with shims
but a new voice coil is usually required.

Good luck




On Jul 21, 7:51 am, "N Cook" wrote:
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

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

N Cook wrote in message
...
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

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



The problem is now more likely the owner having stored it in a damp garage
for a few years , unused.
There were numerous spiders webs and insect cocoons inside the amplifier and
spot rusting of the metalwork of this combo.
So probably insect cocoon or rust flake has got in the coil gap or even cone
distortion due to damp differentially affecting/distorting the cone.
Presumably "palpating" the cone in different clock positions to feel for
rubbing would be the best disgnostic.

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

In article , "N Cook" wrote:
N Cook wrote in message
...
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

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



The problem is now more likely the owner having stored it in a damp garage
for a few years , unused.
There were numerous spiders webs and insect cocoons inside the amplifier and
spot rusting of the metalwork of this combo.
So probably insect cocoon or rust flake has got in the coil gap or even cone
distortion due to damp differentially affecting/distorting the cone.
Presumably "palpating" the cone in different clock positions to feel for
rubbing would be the best disgnostic.

If there is any paint inside there, it can peal and fall off into flakes. I
saw one gap all rusted once.

greg

GregS wrote in message
...
In article , "N Cook"
wrote:
N Cook wrote in message
...
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything
falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face
down.?

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



The problem is now more likely the owner having stored it in a damp
garage
for a few years , unused.
There were numerous spiders webs and insect cocoons inside the amplifier
and
spot rusting of the metalwork of this combo.
So probably insect cocoon or rust flake has got in the coil gap or even
cone
distortion due to damp differentially affecting/distorting the cone.
Presumably "palpating" the cone in different clock positions to feel for
rubbing would be the best disgnostic.

If there is any paint inside there, it can peal and fall off into flakes.
I
saw one gap all rusted once.

greg

I've not literally been able to get my hands on this one yet - still with
the owner , he decided to aquirt the universal solve-all in there - WD40.

If it is salvagable from WD40 etc and if the oproblem is due to damp
affecting the cone , is this being a 15 inch cone more likely to have cone
distortions than a 12 inch for the same sort of damp?
Intuitively I could expect a large cone to be more likely to have a twisting
type distortion than a smaller cone, having a greater proportion of
unsupported edged length to surface area.


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

N Cook wrote in message
...
GregS wrote in message
...
In article , "N Cook"
wrote:
N Cook wrote in message
...
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted
and
causing distortion.
Owner in the habit of transporting face down - to avoid anything
falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face
down.?

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



The problem is now more likely the owner having stored it in a damp
garage
for a few years , unused.
There were numerous spiders webs and insect cocoons inside the
amplifier
and
spot rusting of the metalwork of this combo.
So probably insect cocoon or rust flake has got in the coil gap or even
cone
distortion due to damp differentially affecting/distorting the cone.
Presumably "palpating" the cone in different clock positions to feel
for
rubbing would be the best disgnostic.

If there is any paint inside there, it can peal and fall off into
flakes.
I
saw one gap all rusted once.

greg

I've not literally been able to get my hands on this one yet - still with
the owner , he decided to aquirt the universal solve-all in there - WD40.

If it is salvagable from WD40 etc and if the oproblem is due to damp
affecting the cone , is this being a 15 inch cone more likely to have cone
distortions than a 12 inch for the same sort of damp?
Intuitively I could expect a large cone to be more likely to have a
twisting
type distortion than a smaller cone, having a greater proportion of
unsupported edged length to surface area.


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




correction - vice versa - less proportion of edge length to area

N Cook wrote:

I've not literally been able to get my hands on this one yet - still with
the owner , he decided to aquirt the universal solve-all in there - WD40.


Well if it wasn't knackered before, it is now! Save the WD40 for rusty
gate hinges, it has no place at all in an electronics workshop.

(cue huge debate about the pro`s and cons of WD40)

If it is salvagable from WD40 etc and if the oproblem is due to damp
affecting the cone , is this being a 15 inch cone more likely to have cone
distortions than a 12 inch for the same sort of damp?

If it`s a speaker from a reputable pro manufacturer, get it reconed at
Wembley Loudspeaker, if not, just replace it with whatever the customer
will pay for.


Intuitively I could expect a large cone to be more likely to have a twisting
type distortion than a smaller cone, having a greater proportion of
unsupported edged length to surface area.


What part of a speaker do you consider to be 'unsupported edge length'?

Ron(UK)

Ron(UK) wrote in message
...
N Cook wrote:

I've not literally been able to get my hands on this one yet - still
with
the owner , he decided to aquirt the universal solve-all in there -
WD40.


Well if it wasn't knackered before, it is now! Save the WD40 for rusty
gate hinges, it has no place at all in an electronics workshop.

(cue huge debate about the pro`s and cons of WD40)

If it is salvagable from WD40 etc and if the oproblem is due to damp
affecting the cone , is this being a 15 inch cone more likely to have
cone
distortions than a 12 inch for the same sort of damp?

If it`s a speaker from a reputable pro manufacturer, get it reconed at
Wembley Loudspeaker, if not, just replace it with whatever the customer
will pay for.


Intuitively I could expect a large cone to be more likely to have a
twisting
type distortion than a smaller cone, having a greater proportion of
unsupported edged length to surface area.


What part of a speaker do you consider to be 'unsupported edge length'?

Ron(UK)

If you took a cone from a 12 inch and a 15 inch and laid them face down on a
surface. Then a flat plate on the cylinder extension of the 12 inch and then
some weights on that, but not enough to cause it to collapse.
Then add the same plate and weights to the 15 inch and before the cone would
collapse by compression or radial buckling, would not the larger one be more
likely to start to fail by the central section twisting and then collapse.
Less torsional stiffness is probably the term I'm looking for.

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

N Cook wrote:


If you took a cone from a 12 inch and a 15 inch and laid them face down on a
surface. Then a flat plate on the cylinder extension of the 12 inch and then
some weights on that, but not enough to cause it to collapse.
Then add the same plate and weights to the 15 inch and before the cone would
collapse by compression or radial buckling, would not the larger one be more
likely to start to fail by the central section twisting and then collapse.
Less torsional stiffness is probably the term I'm looking for.

I don't really understand where you're coming from, the only 'weight' on
a speaker cone is the voice coil assembly and dust cover and they weigh
very little, even in a high power speaker. compared to PA speakers,
guitar amp speakers are often deliberately made with reduced cone
stiffness so that they 'trash out' at lower volumes.

In the back of my mind, I do recall seeing a photo of a speaker cone,
face down, with a chap standing on the voice coil former to demonstrate
the strength of the cone assy. I don't remember which company it was.

Most pro speakers have very rigid cone structures, it`s pretty uncommon
to find a professional speaker failure that is attributable to
mechanical damage during use, even over excursion is fairly rare - tho
dj`s do try their hardest.

Almost all pro speaker burnouts are due to being driven with amplifiers
of insufficient headroom,[1] or some external failure i.e. Bad switch
on sequence etc.

There was once a company called Baker who made probably the worse
speakers in the world, the skinny cast alloy baskets would crack,
dumping the puny magnet in the bottom of the cabinet - happily long in
the past.

[1] That statement may lead to flameage

Ron(UK)

Ron(UK) wrote in message
...
N Cook wrote:

If you took a cone from a 12 inch and a 15 inch and laid them face down on
a
surface. Then a flat plate on the cylinder extension of the 12 inch and
then
some weights on that, but not enough to cause it to collapse.
Then add the same plate and weights to the 15 inch and before the cone
would
collapse by compression or radial buckling, would not the larger one be
more
likely to start to fail by the central section twisting and then
collapse.
Less torsional stiffness is probably the term I'm looking for.

I don't really understand where you're coming from, the only 'weight' on
a speaker cone is the voice coil assembly and dust cover and they weigh
very little, even in a high power speaker. compared to PA speakers,
guitar amp speakers are often deliberately made with reduced cone
stiffness so that they 'trash out' at lower volumes.

In the back of my mind, I do recall seeing a photo of a speaker cone,
face down, with a chap standing on the voice coil former to demonstrate
the strength of the cone assy. I don't remember which company it was.

Most pro speakers have very rigid cone structures, it`s pretty uncommon
to find a professional speaker failure that is attributable to
mechanical damage during use, even over excursion is fairly rare - tho
dj`s do try their hardest.

Almost all pro speaker burnouts are due to being driven with amplifiers
of insufficient headroom,[1] or some external failure i.e. Bad switch
on sequence etc.

There was once a company called Baker who made probably the worse
speakers in the world, the skinny cast alloy baskets would crack,
dumping the puny magnet in the bottom of the cabinet - happily long in
the past.

[1] That statement may lead to flameage

Ron(UK)

This was not in-use damage but from storing in a damp garage for some years.
It went in perfectly ok and came out with amp working but speaker sounding
like the amp was clipping. The amp will drive an external speaker fine and
another amp gives horrible noise through this speaker.
So damage due to transporting from (ot to) the garage face-down or more
likely something to do with damp distorting the cone or maybe distorting it
now its been indoors for a few weeks, drying out.

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