Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition? In case it matters,
I'm thinking 10, 12 and 15 inch musical instrument speakers, but any
general info would help. Thanks.

apa wrote:
Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition?

Open voice coil - Hook a 1.5V battery across the terminals and listen
for a click. If you don't hear a click but hear a sort of "tizz" that
means that the voice coil winding has come loose from the form. That's
not good either.

Rubbing voice coil - You might hear a scrape when you "click" the
speaker with a battery. Use your fingers (close to the voice coil) to
move the cone forward and back and listen for any rubbing sound.

Torn cone - obvious. Don't worry about a dent in the dust cover (the
dome-shaped piece at the center of the cone) unless it's torn or
missing.

Bent or warped frame - put it face down on a flat surface and make sure
that it sits flat all around the circle. Look for obvious dents or
nicks in the frame.

Hook it up to an amplifier and play something through it. You can't
tell how good or bad it sounds, but that will let you know if there's a
problem that your inspection hasn't uncovered.

apa wrote:
Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition? In case it matters,
I'm thinking 10, 12 and 15 inch musical instrument speakers, but any
general info would help. Thanks.

For musical instrument speakers, run a swept sine. You shouldn't hear
it rattle or buzz at any frequency. Listen to a couple good drivers and
you'll immediately know it when you find a bad one.

Drivers fail in a lot of ways, but most common are things that cause
them to fail totally. Other than cone damage, the most common non-obvious
failure mode is a deformed voice coil that is scraping, and the swept sine
test will find that very fast.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

apa wrote:

Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition? In case it matters,
I'm thinking 10, 12 and 15 inch musical instrument speakers, but any
general info would help. Thanks.

A speaker can be tested by running some music through it,
or by a simple DC continuity test with a meter. Voltage from
a battery can also give an indication of operation. Also you
can VERY GENTLY move the cone with your fingers and listen
or odd noise and observe uneven motion.

Damaged speakers are repaired in various ways up to and
including a full recone which replaces all the 'active' components.

NonRepairable:

Shifted pole piece (pinched gap) -
The pole piece gets shifted and causes a 'pinched gap'.
Caused by physical shock to the basket such as a dropped
cabinet. Terminal, cannot be repaired in almost all cases.
Symptom - the VC cannot be moved in the gap due to being
pinched.
= = = = =
Repairable with full recone:

Open voice coil - coil winding burned out due to overpowering.
symptom - infinite DC resistance.

Worn out cone - The cone gets worn out around the area
near the VC due to fatigue. Common to heavy paper cones
on larger woofers with proportionately small VCs such as
EVM-18. It's possible the damage will be concealed under
the dome in some designs. plastic cones don't seem suseptable.
Symptom - the VC will rock or tilt back and forth when the cone
in moved.

Damaged cone -
physical damage due to any number of causes.
In many cases the speaker can continue to operate.
symptom - visible damage.

Voice coil rub -
Coil windings warped or shifted due to
heat damage from overpowering or cone damage that
allows the VC to rub on the gap. The rub can be detected
by gently moving the cone through it's normal motion.
= = = = =
Repairable with various methods:

Broken tinsel wire -
The tinsel and VC lead-in wires can become separated from
each other or the terminal due to cold solder or fatigue.
symptom - open DC when tested for continuity.

Spider loose from basket -
A loose spider will cause a VC rub and should be visible.

Outer suspension damage -
The 'accordion' edge can fail in a number of ways depending
on what it's made of. The foam rubber suspensions simply
break down and turn to dust, the fabric type get torn or wear
out and the paper edged style will tear from fatigue.
Foam can be replaced, the paper and fabric usually get a
recone.

Poked or missing dust caps can be replaced.

Warped frame baskets can cause a rubbing VC and might
be reconed after being straightened out.

There may be other failure modes but these are the most
common I've seen during my years as a 'reconer'

rd

Thanks for all the responses.
Is there anything that would cause a speaker to fail such that it
sounds alright at lower volumes but no longer cleanly handles the
levels it could when new? Could be my imagination, but I'd swear I've
heard speakers do this over time, but I don't know how I'd test for it
other than having a known good just like it to test against.


RD Jones wrote:
apa wrote:

Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition? In case it matters,
I'm thinking 10, 12 and 15 inch musical instrument speakers, but any
general info would help. Thanks.

A speaker can be tested by running some music through it,
or by a simple DC continuity test with a meter. Voltage from
a battery can also give an indication of operation. Also you
can VERY GENTLY move the cone with your fingers and listen
or odd noise and observe uneven motion.

Damaged speakers are repaired in various ways up to and
including a full recone which replaces all the 'active' components.

NonRepairable:


Shifted pole piece (pinched gap) -
The pole piece gets shifted and causes a 'pinched gap'.
Caused by physical shock to the basket such as a dropped
cabinet. Terminal, cannot be repaired in almost all cases.
Symptom - the VC cannot be moved in the gap due to being
pinched.
= = = = =
Repairable with full recone:

Open voice coil - coil winding burned out due to overpowering.
symptom - infinite DC resistance.

Worn out cone - The cone gets worn out around the area
near the VC due to fatigue. Common to heavy paper cones
on larger woofers with proportionately small VCs such as
EVM-18. It's possible the damage will be concealed under
the dome in some designs. plastic cones don't seem suseptable.
Symptom - the VC will rock or tilt back and forth when the cone
in moved.

Damaged cone -
physical damage due to any number of causes.
In many cases the speaker can continue to operate.
symptom - visible damage.

Voice coil rub -
Coil windings warped or shifted due to
heat damage from overpowering or cone damage that
allows the VC to rub on the gap. The rub can be detected
by gently moving the cone through it's normal motion.
= = = = =
Repairable with various methods:

Broken tinsel wire -
The tinsel and VC lead-in wires can become separated from
each other or the terminal due to cold solder or fatigue.
symptom - open DC when tested for continuity.

Spider loose from basket -
A loose spider will cause a VC rub and should be visible.

Outer suspension damage -
The 'accordion' edge can fail in a number of ways depending
on what it's made of. The foam rubber suspensions simply
break down and turn to dust, the fabric type get torn or wear
out and the paper edged style will tear from fatigue.
Foam can be replaced, the paper and fabric usually get a
recone.

Poked or missing dust caps can be replaced.

Warped frame baskets can cause a rubbing VC and might
be reconed after being straightened out.

There may be other failure modes but these are the most
common I've seen during my years as a 'reconer'

rd

apa wrote:
Thanks for all the responses.
Is there anything that would cause a speaker to fail such that it
sounds alright at lower volumes but no longer cleanly handles the
levels it could when new?

Yes. A few things could cause that. The voice coil could be rubbing
near the end of its excursion but be clear in the middle. It could also
be caused by contamination in the magnet assembly - metal filings for
instance, accumulating near the poles. If someone has cleaned the
speaker frame or chassis with steel wool, watch out! The tone sweep
that Scott suggested is a pretty good way of looking for problems like
this. Incrase the power to the speaker until the cone is moving over
its full range at low frequencies. Just be careful that you don't ruin
a good speaker this way.

In article , (Scott Dorsey) wrote:
apa wrote:
Can anyone give a list of driver failure modes or a procedure to verify
that a raw speaker is in good working condition? In case it matters,
I'm thinking 10, 12 and 15 inch musical instrument speakers, but any
general info would help. Thanks.

For musical instrument speakers, run a swept sine. You shouldn't hear
it rattle or buzz at any frequency. Listen to a couple good drivers and
you'll immediately know it when you find a bad one.

Thats good to do. I would also run in some low frequency music, and,
or pink noise, sharply cutoff around 400 Hz and listen for any upper frequency
sounds. Inspect tinsel leads for signs of near future failure. I always
handle the driver. Move it in and out , and get the "feel". also look for
even surround fexing.

greg

Drivers fail in a lot of ways, but most common are things that cause
them to fail totally. Other than cone damage, the most common non-obvious
failure mode is a deformed voice coil that is scraping, and the swept sine
test will find that very fast.
--scott

In article . com, "apa" wrote:
Thanks for all the responses.
Is there anything that would cause a speaker to fail such that it
sounds alright at lower volumes but no longer cleanly handles the
levels it could when new? Could be my imagination, but I'd swear I've
heard speakers do this over time, but I don't know how I'd test for it
other than having a known good just like it to test against.

The voice coil can hit up against the back of the magnet making nasty sounds.
Over time the centering of the cone and the strength of the spyder can
loosen up, decreasing power handling. High frequency drivers can sometimes
produce nasty lower frequency sounds, mainly at the resonance frequency,
if things aren't right.

greg

apa wrote:
Thanks for all the responses.
Is there anything that would cause a speaker to fail such that it
sounds alright at lower volumes but no longer cleanly handles the
levels it could when new? Could be my imagination, but I'd swear I've
heard speakers do this over time, but I don't know how I'd test for it
other than having a known good just like it to test against.

Yes, this can be caused by anything that changes the gap shape. It is
more common, though, for you to get speakers that sound okay at full
level but not at low levels.

A swept sine test will usually show these problems up very quickly.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."