Speaker Failure article

[Phil Allison]

Hi all,

this short article, by yours truly, sets out to debunk the many absurd myths
surrounding sudden failures of loudspeakers - particularly woofers used in
live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit at a
time and cogitate.

Take a careful look at the links provided at the end of the article too.

And before anyone asks, the 40mm voice coil and magnet gap are from a 10
inch woofer used in a very old AR2a.

The pics shown in the article were taken by me with a pocket size Cannon
A430.



..... Phil

 

[William Sommerwerck]

The article is rather tightly written, so you may need
to read it a bit at a time and cogitate.

Actually, it's terse and to the point. It needs a bit of editing here and
there, but everything does. I'm currently editing articles for "Electronic
Design". If every one were of this quality, I wouldn't have a job.

I'm reminded of Robert Stroud, the Birdman of Alcatraz.

The pics shown in the article were taken by me with
a pocket size Cannon A430.

Talk about Freudian slips...

 

[Phil Allison]

"William Sommerwerck"

The article is rather tightly written, so you may need
to read it a bit at a time and cogitate.

Actually, it's terse and to the point. It needs a bit of editing here and
there, but everything does. I'm currently editing articles for "Electronic
Design". If every one were of this quality, I wouldn't have a job.

I'm reminded of Robert Stroud, the Birdman of Alcatraz.

** That's the nicest thing Bill has ever said about me.

Tears .........

The pics shown in the article were taken by me with
a pocket size Cannon A430.

Talk about Freudian slips...

** Because I misspelled "Canon" ??



...... Phil

 

[William Sommerwerck]

The pics shown in the article were taken by me
with a pocket size Cannon A430.

Talk about Freudian slips...

** Because I misspelled "Canon" ?

Well, you are rather a loud, loose cannon.

 

[Phil Allison]

"William Sommerwerck"

The pics shown in the article were taken by me
with a pocket size Cannon A430.

Talk about Freudian slips...

** Because I misspelled "Canon" ?

Well, you are rather a loud, loose cannon.

** No way - I am a real straight shooter, every time.

As us Aussies would say, Sommerwanker is the one with:

" A few roos loose in the top paddock "



..... Phil

 

[William Sommerwerck]

** No way -- I am a real straight shooter, every time.

The following is meant seriously and sincerely...

You're not aware of your Jekyll-and-Hyde behavior? If you are, do you think
it's normal or justifiable?

 

[Phil Allison]

"William Sommerwanker"

** No way -- I am a real straight shooter, every time.

The following is meant seriously and sincerely...

You're not aware of your Jekyll-and-Hyde behaviour?

** No such thing for me or anyone else to aware of.

But I have long ( something like 8 years long ) been very aware that YOU
are merely another half witted, autistic, mental defective.

Usenet is flooded with hundreds of similar, defective individuals, attracted
just like moths are attracted to lights at night.

So is the entire academic world, the public service and all forms of
bureaucracy.

Human garbage and the root cause of all trouble and misery on this planet.



.... Phil

 

[Wond]

On Tue, 05 Jun 2012 15:57:26 +1000, Phil Allison wrote:

Hi all,

this short article, by yours truly, sets out to debunk the many absurd
myths surrounding sudden failures of loudspeakers - particularly
woofers used in live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit
at a time and cogitate.

Take a careful look at the links provided at the end of the article too.

And before anyone asks, the 40mm voice coil and magnet gap are from a 10
inch woofer used in a very old AR2a.

The pics shown in the article were taken by me with a pocket size Cannon
A430.



.... Phil

Great summary, Phil, thanks for posting. And, thanks Rod, for the
site!

 

[spamtrap1888]

On Jun 4, 10:57 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

Hi all,

this short article, by yours truly, sets out to debunk the many absurd myths
surrounding sudden failures of loudspeakers  - particularly woofers used in
live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit at a
time and cogitate.

Take a careful look at the links provided at the end of the article too.

And before anyone asks, the 40mm voice coil and magnet gap are from a 10
inch woofer used in a very old AR2a.

The pics shown in the article were taken by me with a pocket size Cannon
A430.

....  Phil

Pretty good! The write up does raise a few issues I would like to
address:

1. Back in the day we found that the pole piece vent is useless for
cooling. Without the vent, when the woofer compresses the air in the
enclosure, the dustcap (assume solid) pushes air between the voice
coil former and the pole piece. This causes air to flow out of the
space between the magnet and the pole piece, over the wires of the
voice coil and out the gap. On the expansion stroke, air flows back
over the voice coil and then between the VC former and the pole piece.

With the vented pole piece, most of the air simply goes in and out the
vent, and not past the voice coil. The forced air movement past the
voice coil caused by the unvented pole piece should cool it better
than simple conduction (plus some convection) to the pole and to the
top plate when the pole piece is vented.

Now, all this air movement past the voice coil may affect the way the
speaker responds to an audio input. Thus the vent may make for less
distortion even though it's counterproductive for cooling. In that
case, a dustcap that lets air flow through it might be simpler and
cheaper than drilling a vent hole through the pole piece.

2. While the point is well taken that attempting to eliminate clipping
by using higher powered amps merely increases power supplied to the
speaker, for a given amplifier, tweeters are significantly more likely
to be destroyed when the amplifier clips, because amplifier clipping
sharply increases the amount of high frequency signal, and tweeters'
small excursions produce less cooling. Tweeter failure due to clipping
may be the origin of the silly idea that higher power amplifiers cause
less damage.

Showing what happens to the pink noise spectrum between input and
output of a clipping amp would be instructive -- the article's
graphics refer only to the time domain.

3. Saying that the minimum impedance is purely resistive grates a bit,
because the voice coil always has some inductive reactance, however
small, and there is some intrawinding capacitance as well. The minimum
impedance is just the spot where the high electrical impedance of the
mechanical resonance rolls off and before the inductive reactance
takes hold.

4. Just for interest: At the speaker company, our tech built a working
cutaway model. I forget how he wound the coil, but he could drive it
at the mechanical resonance to produce visible woofer excursion.

 

[William Sommerwerck]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:a36hf8Fqk4U1@mid.individual.net...

"William Sommerwerck"

** No way -- I am a real straight shooter, every time.

The following is meant seriously and sincerely...
You're not aware of your Jekyll-and-Hyde behaviour?

** No such thing for me or anyone else to aware of.

But I have long (something like 8 years long) been very aware that
YOU are merely another half[-]witted, autistic, mental defective.
Usenet is flooded with hundreds of similar, defective individuals,
attracted just like moths are attracted to lights at night.

You're just the sort of person I enjoy fluttering around.

So is the entire academic world, the public service and all forms of
bureaucracy. Human garbage and the root cause of all trouble and
misery on this planet.

So this is all serious? It's not some out-of-control joke?

Why would anyone want you as a friend, let alone be around you?

 

[Rheilly Phoull]

On 6/6/2012 3:06 AM, William Sommerwerck wrote:

"Phil Allison"<phil_a@tpg.com.au> wrote in message
news:a36hf8Fqk4U1@mid.individual.net...
"William Sommerwerck"

** No way -- I am a real straight shooter, every time.

The following is meant seriously and sincerely...
You're not aware of your Jekyll-and-Hyde behaviour?

** No such thing for me or anyone else to aware of.

But I have long (something like 8 years long) been very aware that
YOU are merely another half[-]witted, autistic, mental defective.
Usenet is flooded with hundreds of similar, defective individuals,
attracted just like moths are attracted to lights at night.

You're just the sort of person I enjoy fluttering around.

So is the entire academic world, the public service and all forms of
bureaucracy. Human garbage and the root cause of all trouble and
misery on this planet.

So this is all serious? It's not some out-of-control joke?

Why would anyone want you as a friend, let alone be around you?

Ahhh !!
That's better lads, I was starting to worry about you. You know getting
all sentimental and stuff

Rheilly

 

[Phil Allison]

"spamtrap1888"
"Phil Allison"

this short article, by yours truly, sets out to debunk the many absurd
myths
surrounding sudden failures of loudspeakers - particularly woofers used in
live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit at
a
time and cogitate.

Take a careful look at the links provided at the end of the article too.

--------------------------------------------------------------------------

Pretty good! The write up does raise a few issues I would like to
address:

1. Back in the day we found that the pole piece vent is useless for
cooling. Without the vent, when the woofer compresses the air in the
enclosure, the dustcap (assume solid) pushes air between the voice
coil former and the pole piece. This causes air to flow out of the
space between the magnet and the pole piece, over the wires of the
voice coil and out the gap. On the expansion stroke, air flows back
over the voice coil and then between the VC former and the pole piece.
--------------------------------------------------------------------------------

** With most speakers, there is a sealed volume behind the magnetic gap so
very little air flow goes on.
Hot air adjacent to the voice coil circulates with cooler air and this
serves to heat the magnet structure, along with conduction and radiation of
heat from the voice coil.

The main reason for having a hollow pole piece is to relieve pressure on the
cone during large excursions, but it also allows moving air to cool the pole
piece too.

---------------------------------------------------------------------------
With the vented pole piece, most of the air simply goes in and out the
vent, and not past the voice coil. The forced air movement past the
voice coil caused by the unvented pole piece should cool it better
than simple conduction (plus some convection) to the pole and to the
top plate when the pole piece is vented.
----------------------------------------------------

** JBL designed a way to force cool air over at least part of the voice coil
in operation - provided the cone is moving significantly at low frequencies
of course. Their idea, called " Vented Gap Cooling " takes advantage of the
AES 50Hz to 500Hz testing method to get around double the previous published
power ratings.

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=297

See the final two paras on the first page.

----------------------------------------------------------------------------

2. While the point is well taken that attempting to eliminate clipping
by using higher powered amps merely increases power supplied to the
speaker, for a given amplifier, tweeters are significantly more likely
to be destroyed when the amplifier clips, because amplifier clipping
sharply increases the amount of high frequency signal, and tweeters'
small excursions produce less cooling.

--------------------------------------------------------------------------------

** Tweeters burn out for the exact same reason woofers do when the ampler
clips - cos the *average power level* has gone up !!

With normal unclipped programme, a tweeter may receive 5% of the applied
power or 5 watts out of 100. With 6 dB of clipping, that same tweeter will
now receive 20 watts, a direct result of turning up the gain by 6dB.

Others have done tests to show that the increase in high frequency energy
due to peak clipping music programme is small in comparison to the above.

------------------------------------------------------------------------------

3. Saying that the minimum impedance is purely resistive grates a bit,
because the voice coil always has some inductive reactance, however
small, and there is some intrawinding capacitance as well.

-----------------------------------------------------------------------------

** Real speakers (woofers) test purely resistive at some frequency in the
200Hz to 500Hz range and this condition corresponds with the impedance
minimum.

If the impedance minimum for a particular driver is at 250Hz, then below
that frequency the impedance is capacitive and above that frequency it is
inductive. ( There is usually about an octave range where the impedance
varies by only 10%. )

If you sweep test a driver using a dual trace scope, one channel for voltage
and one showing current, you can observe the two traces coinciding in phase
at any impedance minimum or maximum.


The minimum
impedance is just the spot where the high electrical impedance of the
mechanical resonance rolls off and before the inductive reactance
takes hold.

** Correct.

If you were to jam the voice coil tight in the cap, then all you have is the
R of the coil plus some ( lossy) inductance.


..... Phil

 

[Arfa Daily]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:a37r0bFck7U1@mid.individual.net...

"spamtrap1888"
"Phil Allison"

this short article, by yours truly, sets out to debunk the many absurd
myths
surrounding sudden failures of loudspeakers - particularly woofers used
in
live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit
at a
time and cogitate.

Take a careful look at the links provided at the end of the article too.

One quick observation, Phil.

In section 2 - Voice Coil Construction, your photo reference for a destroyed
voice coil is wrongly stated as "Figure 5". The photos that show destroyed /
damaged coils are actually figures 6 and 7.

Good article, though

Arfa

 

[William Sommerwerck]

Admittedly my AC theory is a bit rusty, as am I,
but since a voice coil has an inductive component
to it shouldn't the formula incorporate the J factor,
(R+JX)? Or is this just a theoretical example of perhaps
a DC current being passed through the voice coil?

Mr Allison is quick to call me and others autistic idiots. Well, this
autistic idiot will be the first to give the correct answer.

The reactive component of the voice-coil impedance -- or any impedance --
doesn't dissipate energy. It's as simple as that.

 

[Phil Allison]

"klem kedidelhopper"

This is a very well written article Phil however I have a question. In
"voice coil facts" you state:

"When a current is passed through a voice coil, heat is generated. The
amount of heat in watts is given by the very simple formula:

P = I˛ * R - where I is the RMS current and R is the actual
resistance of the wire, at any temperature"

Admittedly my AC theory is a bit rusty, as am I but since a voice coil
has an inductive component to it shouldn't the formula incorporate
the J factor, (R+JX)? Or is this just a theoretical example of perhaps
a DC current being passed through the voice coil? Lenny


** Sometimes the facts are SOOOO simple folk refuse to believe them.

In any complex, reactive circuit ONLY the resistive components dissipate
actual heat.

Inductive or capacitive components in series with resistive ones only act to
REDUCE the current flow.

So, with a speaker voice coil, one only has to know the RMS current flow and
the actual R value to calculate the HEAT in watts.

R varies with temp, so watch out.


.... Phil

 

[klem kedidelhopper]

On Jun 6, 9:28 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"Phil Allison" <phi...@tpg.com.au> wrote in message

news:a37r0bFck7U1@mid.individual.net...











"spamtrap1888"
"Phil Allison"

this short article, by yours truly, sets out to debunk the many absurd
myths
surrounding sudden failures of loudspeakers - particularly woofers used
in
live music and disco sound systems.

http://sound.westhost.com/articles/speaker-failure.html

The article is rather tightly written, so you may need to read it a bit
at a
time and cogitate.

Take a careful look at the links provided at the end of the article too.

One quick observation, Phil.

In section 2 - Voice Coil Construction, your photo reference for a destroyed
voice coil is wrongly stated as "Figure 5". The photos that show destroyed /
damaged coils are actually figures 6 and 7.

Good article, though

Arfa

This is a very well written article Phil however I have a question. In
"voice coil facts" you state:

"When a current is passed through a voice coil, heat is generated. The
amount of heat in watts is given by the very simple formula:

P = I˛ * R - where I is the RMS current and R is the actual
resistance of the wire, at any temperature"

Admittedly my AC theory is a bit rusty, as am I but since a voice coil
has an inductive component to it shouldn't the formula incorporate
the J factor, (R+JX)? Or is this just a theoretical example of perhaps
a DC current being passed through the voice coil? Lenny

With eith

 

[klem kedidelhopper]

On Jun 9, 11:14 am, "Phil Allison" <phi...@tpg.com.au> wrote:

"klem kedidelhopper"

This is a very well written article Phil however I have a question. In
"voice coil facts" you state:

"When a current is passed through a voice coil, heat is generated. The
amount of heat in watts is given by the very simple formula:

 P = I˛ * R - where I is the RMS current and R is the actual
resistance of the wire, at any temperature"

Admittedly my AC theory is a bit rusty, as am I but since a voice coil
has an inductive component to it shouldn't the formula  incorporate
the J factor, (R+JX)? Or is this just a theoretical example of perhaps
a DC current being passed through the voice coil? Lenny

** Sometimes the facts are  SOOOO  simple folk refuse to believe them..

In any complex, reactive circuit  ONLY the resistive components dissipate
actual heat.

Inductive or capacitive components in series with resistive ones only act to
REDUCE the current flow.

So, with a speaker voice coil, one only has to know the RMS current flow and
the actual R value to calculate the HEAT in watts.

R varies with temp, so watch out.

...  Phil

Thanks William and Phil. It HAS been a while since AC theory. Lenny

 

[Phil Allison]

<jurb6006@gmail.com>

Actually thst airflow in the voice coile is negligible in an infinite baffle
system. And the smaller the cabinet, the more negligible it is.

I built a system once the was so totally short on cubic, but so totally tall
on watts that if I would have left it that way the cabinet would have
exploded.

They were some type of thruster type speakers, the foam was all out. I put
woofers in for the 10" passive radiators as well as the 8" actual woofers.
The one set was four ohms which made the system 2.6 ohms.

Boomy as hell, but I have a Soundcraftsman PE 2217. Every DB of boost at 31
and every one of cut at 120 did most of it, and they sounded good.(I used
them for surround at the time) Really, this is what the system needed.
Nobody bitched when Bose did it. (remember the EQs for the 901s)

But those cones barely moved. Without a port fighting them they didn't have
to move as much, and their response was alot more predictable.

Just so you know, I am better than Dr. Bose. I can get you good sound out of
cardboard boxes. If you doubt that, come on down and challenge me. You know
what else that will blow your fucking mind ? I can do it all with Radio
Shack shit !

You think I'm kidding ? Well I am right here. Sound is a matter of taste,
like cooking. Even Radio Shack tweeters can be set up to sound good, if you
know what you are doing.

I can make a crossover that makes a dead frog sound like an ESS Heil. Well
close.


** And besides all that - you are such a modest chap.

Plus you spelling is just wonderful .....



.... Phil

 

Actually thst airflow in the voice coile is negligible in an infinite baffle system. And the smaller the cabinet, the more negligible it is.

I built a system once the was so totally short on cubic, but so totally tall on watts that if I would have left it that way the cabinet would have exploded.

They were some type of thruster type speakers, the foam was all out. I put woofers in for the 10" passive radiators as well as the 8" actual woofers. The one set was four ohms which made the system 2.6 ohms.

Boomy as hell, but I have a Soundcraftsman PE 2217. Every DB of boost at 31 and every one of cut at 120 did most of it, and they sounded good.(I used them for surround at the time) Really, this is what the system needed. Nobody bitched when Bose did it. (remember the EQs for the 901s)

But those cones barely moved. Without a port fighting them they didn't have to move as much, and their response was alot more predictable.

Just so you know, I am better than Dr. Bose. I can get you good sound out of cardboard boxes. If you doubt that, come on down and challenge me. You know what else that will blow your fucking mind ? I can do it all with Radio Shack shit !

You think I'm kidding ? Well I am right here. Sound is a matter of taste, like cooking. Even Radio Shack tweeters can be set up to sound good, if you know what you are doing.

I can make a crossover that makes a dead frog sound like an ESS Heil. Well close.

J

 

[JW]

On Mon, 18 Jun 2012 21:50:41 +1000 "Phil Allison" <phil_a@tpg.com.au>
wrote in Message id: <a48j0oFt7eU1@mid.individual.net>:

jurb6006@gmail.com

Actually thst airflow in the voice coile is negligible in an infinite baffle
system. And the smaller the cabinet, the more negligible it is.

I built a system once the was so totally short on cubic, but so totally tall
on watts that if I would have left it that way the cabinet would have
exploded.

They were some type of thruster type speakers, the foam was all out. I put
woofers in for the 10" passive radiators as well as the 8" actual woofers.
The one set was four ohms which made the system 2.6 ohms.

Boomy as hell, but I have a Soundcraftsman PE 2217. Every DB of boost at 31
and every one of cut at 120 did most of it, and they sounded good.(I used
them for surround at the time) Really, this is what the system needed.
Nobody bitched when Bose did it. (remember the EQs for the 901s)

But those cones barely moved. Without a port fighting them they didn't have
to move as much, and their response was alot more predictable.

Just so you know, I am better than Dr. Bose. I can get you good sound out of
cardboard boxes. If you doubt that, come on down and challenge me. You know
what else that will blow your fucking mind ? I can do it all with Radio
Shack shit !

You think I'm kidding ? Well I am right here. Sound is a matter of taste,
like cooking. Even Radio Shack tweeters can be set up to sound good, if you
know what you are doing.

I can make a crossover that makes a dead frog sound like an ESS Heil. Well
close.


** And besides all that - you are such a modest chap.

Plus you spelling is just wonderful .....

Please tell me that that was intentional...