Speaker Repair

[dave]

On 05/26/2014 10:05 AM, Unquestionably Confused wrote:

On 5/26/2014 11:56 AM, William Sommerwerck wrote:
"Ian Field" wrote in message news:m7Kgv.181325$8%2.35334@fx06.am4...

Some allegedly high quality speakers have some sort of flexible
foam rubber [sic] as the suspension round the outside of the cone
-- it usually perishes sooner rather than later.

Foam has largely been abandoned because it eventually self-destructs. It
isn't rubber, it's a synthetic polymer.

I have a pair of original Advents (final green-tweeter iteration), with
foam surrounds in perfect condition. Why, I don't know.

Nothing allegedly about it. I have a pair of Infinity speakers (~ 30
yrs old now) and had to replace the surrounds on several of the speakers
a year or so back. Foam becomes brittle (age? atmosphere? dog farts?
sun/ambient light?) and just starts to disintegrate.

Fortunately, found an outfit on line that sells kits for DIY repair.
Figured that I had nothing to lose I popped for the kits and repair was
a piece of cake. All's well and I'm good for another 30 years (well,
not me, but the speakers<g&gt

It is ozone that dissolves foam surrounds. They are real easy to repair.
No biggie.

 

[William Sommerwerck]

"dave" wrote in message news:H42dnTrR1cf44R7OnZ2dnUVZ_juXnZ2d@earthlink.com...

> It is ozone that dissolves foam surrounds.

Foam -- such as the foam in carrying cases -- softens and falls apart even
when not exposed to environmental contaminants. It just isn't stable.

 

[josephkk]

On Wed, 21 May 2014 19:24:27 -0400, "Robert Green"
<robert_green1963@yah00.com> wrote:

I've got a lot of big, small and medium speakers that have blown out over
the years. Typically I take them to the attic where they usually make
pretty good bookshelf supports.

In the spirit of domestic harmony, I am cleaning out said attic (anyone
*really* refer to their old college texts or books they have read in the
past anymore?). So with all the books being "de-accessioned"

I kept all my college texts. I even occasionally lend them out. I keep
much of my pleasure reading as well.

(librarian-speak for "thrown out") I am left with a lot of bowed knotty pine
planks and burned out speakers.

If they can be salvaged, I can use them, but if they're likely to just blow
out again, I will send them to the curb monster that comes by late at night
before trash day.

So my question is this. Is it worth repairing 10 or 20 year old speakers?
Can replacements be readily had?

If you can get or make parts.

Is there a good site for diagnosing speaker problems? I almost always
assume it's a fine wire winding in the voice coil that shorted when a
speaker no longer even responds to a battery "click" test but I that's an
assumption.

Is it possible to match the characteristics of the old speakers closely
enough without manufacturer info like a parts list?

Do crossover networks ever go bad? Can they be tested with a multimeter?

Yes but it is rare.
Yes, they can. They are just capacitors and inductors, separate them and
test the components themselves, capacitors dying is by far the most
frequent failure mode. Replacement parts may be hard to get.

And yes, I googled it,

http://www.google.com/search?q=diagnosing+speaker+problems&btnG=Search

but I didn't like very many of the sites it revealed. I'll keep searching
but Google ain't what she used to be.

Hmm, should have added "blown" to the search term - much better. Still not
great, though.

Thanks in advance for your input.

(Followups to alt.home.repair please!)

 

On Mon, 26 May 2014 21:52:39 -0400, J Burns <burns4@nowhere.com>
wrote:

On 5/23/14, 4:16 PM, Robert Green wrote:
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:llk4g8$qp4$1@dont-email.me...

stuff snipped

If this was a UK loft then you've increased the probability of adding
bits of iron-corrossion product , now trapped by the magnet , in the VC
gap , to give that classic scratchy sound, as well as the original failure

It's a fairly high humidity Washington DC attic.

I didn't know that ferrous debris in the VC gap was an issue. I thought the
scratchy sound came from the voice coil detaching from the paper/plastic
cone.

Thanks for your input!

--
Bobby G.



The surround is supposed to keep the cone (and voice coil) centered. I
think scratching was how I realized something was wrong with my
surrounds. When I glued in a new surround, I'd let the glue set, then
move the cone to be sure it didn't scratch. Of ten speakers, I think I
had to reset one surround. I'm glad I caught it while the glue was soft.

If the "spider" is good, the surround doesn't do any locating. I
rebuilt 8, 4 of them 12 inchers, With the surrounds totally removed
there was no scratching I didn't need to shim the voice coil, and the
surrounds went on quickly and easily, and the speakers sound
EXCELLENT.They were pretty high end speakers - can't remember the
brand and they are up in the mezzanine so I can't check.

 

[J Burns]

On 5/23/14, 4:16 PM, Robert Green wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:llk4g8$qp4$1@dont-email.me...

stuff snipped

If this was a UK loft then you've increased the probability of adding
bits of iron-corrossion product , now trapped by the magnet , in the VC
gap , to give that classic scratchy sound, as well as the original failure

It's a fairly high humidity Washington DC attic.

I didn't know that ferrous debris in the VC gap was an issue. I thought the
scratchy sound came from the voice coil detaching from the paper/plastic
cone.

Thanks for your input!

--
Bobby G.

The surround is supposed to keep the cone (and voice coil) centered. I
think scratching was how I realized something was wrong with my
surrounds. When I glued in a new surround, I'd let the glue set, then
move the cone to be sure it didn't scratch. Of ten speakers, I think I
had to reset one surround. I'm glad I caught it while the glue was soft.

 

[dave]

On 05/26/2014 06:52 PM, J Burns wrote:

On 5/23/14, 4:16 PM, Robert Green wrote:
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:llk4g8$qp4$1@dont-email.me...

stuff snipped

If this was a UK loft then you've increased the probability of adding
bits of iron-corrossion product , now trapped by the magnet , in the VC
gap , to give that classic scratchy sound, as well as the original
failure

It's a fairly high humidity Washington DC attic.

I didn't know that ferrous debris in the VC gap was an issue. I
thought the
scratchy sound came from the voice coil detaching from the paper/plastic
cone.

Thanks for your input!

--
Bobby G.



The surround is supposed to keep the cone (and voice coil) centered. I
think scratching was how I realized something was wrong with my
surrounds. When I glued in a new surround, I'd let the glue set, then
move the cone to be sure it didn't scratch. Of ten speakers, I think I
had to reset one surround. I'm glad I caught it while the glue was soft.

The surround is for acoustic loading. The spider keeps the motor aligned.

 

[josephkk]

On Tue, 27 May 2014 05:33:47 -0700, dave <ricketzz@earthlink.net> wrote:

On 05/26/2014 06:52 PM, J Burns wrote:
On 5/23/14, 4:16 PM, Robert Green wrote:
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:llk4g8$qp4$1@dont-email.me...

stuff snipped

If this was a UK loft then you've increased the probability of adding
bits of iron-corrossion product , now trapped by the magnet , in the VC
gap , to give that classic scratchy sound, as well as the original
failure

It's a fairly high humidity Washington DC attic.

I didn't know that ferrous debris in the VC gap was an issue. I
thought the
scratchy sound came from the voice coil detaching from the paper/plastic
cone.

Thanks for your input!

--
Bobby G.



The surround is supposed to keep the cone (and voice coil) centered. I
think scratching was how I realized something was wrong with my
surrounds. When I glued in a new surround, I'd let the glue set, then
move the cone to be sure it didn't scratch. Of ten speakers, I think I
had to reset one surround. I'm glad I caught it while the glue was soft.

The surround is for acoustic loading. The spider keeps the motor aligned.

Not quite the case. The surround seals the airflow between the cone and
the spider. It also provides axial tilt support for the voice coil. Both
properties are important to overall function.

?-)

 

[dave]

On 05/28/2014 09:27 PM, josephkk wrote:

On Tue, 27 May 2014 05:33:47 -0700, dave <ricketzz@earthlink.net> wrote:

On 05/26/2014 06:52 PM, J Burns wrote:
On 5/23/14, 4:16 PM, Robert Green wrote:
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:llk4g8$qp4$1@dont-email.me...

stuff snipped

If this was a UK loft then you've increased the probability of adding
bits of iron-corrossion product , now trapped by the magnet , in the VC
gap , to give that classic scratchy sound, as well as the original
failure

It's a fairly high humidity Washington DC attic.

I didn't know that ferrous debris in the VC gap was an issue. I
thought the
scratchy sound came from the voice coil detaching from the paper/plastic
cone.

Thanks for your input!

--
Bobby G.



The surround is supposed to keep the cone (and voice coil) centered. I
think scratching was how I realized something was wrong with my
surrounds. When I glued in a new surround, I'd let the glue set, then
move the cone to be sure it didn't scratch. Of ten speakers, I think I
had to reset one surround. I'm glad I caught it while the glue was soft.

The surround is for acoustic loading. The spider keeps the motor aligned.


Not quite the case. The surround seals the airflow between the cone and
the spider. It also provides axial tilt support for the voice coil. Both
properties are important to overall function.

?-)

Speakers work without surrounds; "seals the airflow" is another way to
say "acoustic loading", ain't it? I use shims so the surround is glued
when the piston is at rest, thus favoring neither compression nor
rarefaction.

Try torquing a spider supported voice coil with a piece of soft
cardboard, not gonna happen.

 

[Tony Hwang]

NotMe wrote:

"Robert Green" <robert_green1963@yah00.com> wrote in message
news:llje3k$d8a$1@speranza.aioe.org...
I've got a lot of big, small and medium speakers that have blown out over
the years. Typically I take them to the attic where they usually make
pretty good bookshelf supports.

In the spirit of domestic harmony, I am cleaning out said attic (anyone
*really* refer to their old college texts or books they have read in the
past anymore?). So with all the books being "de-accessioned"
(librarian-speak for "thrown out") I am left with a lot of bowed knotty
pine
planks and burned out speakers.

If they can be salvaged, I can use them, but if they're likely to just
blow
out again, I will send them to the curb monster that comes by late at
night
before trash day.

So my question is this. Is it worth repairing 10 or 20 year old speakers?
Can replacements be readily had?

Is there a good site for diagnosing speaker problems? I almost always
assume it's a fine wire winding in the voice coil that shorted when a
speaker no longer even responds to a battery "click" test but I that's an
assumption.

Is it possible to match the characteristics of the old speakers closely
enough without manufacturer info like a parts list?

Do crossover networks ever go bad? Can they be tested with a multimeter?

And yes, I googled it,

http://www.google.com/search?q=diagnosing+speaker+problems&btnG=Search

but I didn't like very many of the sites it revealed. I'll keep searching
but Google ain't what she used to be.

Hmm, should have added "blown" to the search term - much better. Still
not
great, though.

Thanks in advance for your input.

(Followups to alt.home.repair please!)

If you're blowing out speakers with that regularity I expect a sever miss
math in equipment. The second would be a recommendation to have your
hearing check as you may have damaged/serious loss of hearing.

All my kids were big into music. I made sure they wore ear protection at
concerts and especially when they were performing. Unlike me (too many
years near jet engines) they can still hear a pin drop.

Hmmm,
Not only high power blows speakers. El Cheapo amps can blow speakers
much easier than good amps. Why? Cheap amps have too much garbage in
the output signal. My kids are in music since toddlers. Piano, sax,
flute, drum, guitars. I don't have to tell, they wear ear plugs when
they jam. Me? I am lower brass lifer since high school days. Still
active with local concert band.

 

[dave]

On 05/29/2014 08:59 AM, Tony Hwang wrote:

NotMe wrote:



Hmmm,
Not only high power blows speakers. El Cheapo amps can blow speakers
much easier than good amps. Why? Cheap amps have too much garbage in
the output signal. My kids are in music since toddlers. Piano, sax,
flute, drum, guitars. I don't have to tell, they wear ear plugs when
they jam. Me? I am lower brass lifer since high school days. Still
active with local concert band.

It's the clipping in the Power Amp that puts DC pulses of opposite
polarity into the voice coil. Pulses always destroy better than steady
current.

 

[dave]

On 05/30/2014 07:16 AM, dave wrote:

On 05/29/2014 08:59 AM, Tony Hwang wrote:
NotMe wrote:



Hmmm,
Not only high power blows speakers. El Cheapo amps can blow speakers
much easier than good amps. Why? Cheap amps have too much garbage in
the output signal. My kids are in music since toddlers. Piano, sax,
flute, drum, guitars. I don't have to tell, they wear ear plugs when
they jam. Me? I am lower brass lifer since high school days. Still
active with local concert band.

It's the clipping in the Power Amp that puts DC pulses of opposite
polarity into the voice coil. Pulses always destroy better than steady
current.

RMS = Peak (in a square wave situation afaik)

 

[josephkk]

On Thu, 29 May 2014 08:29:48 -0700, dave <ricketzz@earthlink.net> wrote:

The surround is for acoustic loading. The spider keeps the motor aligned.


Not quite the case. The surround seals the airflow between the cone and
the spider. It also provides axial tilt support for the voice coil. Both
properties are important to overall function.

?-)


Speakers work without surrounds; "seals the airflow" is another way to
say "acoustic loading", ain't it? I use shims so the surround is glued
when the piston is at rest, thus favoring neither compression nor
rarefaction.

Try torquing a spider supported voice coil with a piece of soft
cardboard, not gonna happen.

Your view of acoustic loading seem rather different from mine. Segregating
the forward and rearward acoustic domains is a prerequisite for acoustic
loading to occur. Acoustic loading is mainly determined by the physics of
the speaker enclosure, be it stuffed with absorptive batting, folded horn,
bass reflex, or some other design.

?-)

 

[dave]

On 06/08/2014 04:08 PM, josephkk wrote:

On Thu, 29 May 2014 08:29:48 -0700, dave <ricketzz@earthlink.net> wrote:


The surround is for acoustic loading. The spider keeps the motor aligned.


Not quite the case. The surround seals the airflow between the cone and
the spider. It also provides axial tilt support for the voice coil. Both
properties are important to overall function.

?-)


Speakers work without surrounds; "seals the airflow" is another way to
say "acoustic loading", ain't it? I use shims so the surround is glued
when the piston is at rest, thus favoring neither compression nor
rarefaction.

Try torquing a spider supported voice coil with a piece of soft
cardboard, not gonna happen.

Your view of acoustic loading seem rather different from mine. Segregating
the forward and rearward acoustic domains is a prerequisite for acoustic
loading to occur. Acoustic loading is mainly determined by the physics of
the speaker enclosure, be it stuffed with absorptive batting, folded horn,
bass reflex, or some other design.

?-)

The surround separates the air behind the speaker from the air in the
room, don't it? A sure sign your surrounds are gone is the bass falls
off. If you have subwoofers you can go a long time before you even
notice your mains have bad surrounds. I have some AR4x that appear to
have the original surrounds from ca 1968. All foam not created equal.
Refoaming is not difficult. You can do a a couple speakers in an hour,
once they have been removed from the cabinets. Be "clean room" as
possible when the dust caps are off. Get old glue off the frames before
removing dust caps and shimming. I use little shims made from theatrical
lighting gels, that's about the right thickness for 10" Advent/AR style
low compliance woofers. The choices for replacement foam rings are size
and the angle of the interface with the cone. Actually whether there is
an angle. Either angled or not. That's it. YouTube has a million proud
tutorials I'm sure.

 

[jfeng@my-deja.com]

On Monday, June 9, 2014 7:21:13 AM UTC-7, dave wrote:

I have some AR4x that appear to
have the original surrounds from ca 1968. All foam not created
equal. Refoaming is not difficult.
Are yours really foam? I have some AR-2ax's from the early 1907s, and the surrounds appear to be rubberized cloth (which should make a better seal than foam). They have survived over 30 years of California smog with no obvious degradation. I do not remember seeing foam on any of the old AR speakers (AR 1-4) I have seen at the swap meets.

 

[gregz]

"jfeng@my-deja.com" <jfeng@my-deja.com> wrote:

On Monday, June 9, 2014 7:21:13 AM UTC-7, dave wrote:

I have some AR4x that appear to
have the original surrounds from ca 1968. All foam not created
equal. Refoaming is not difficult.
Are yours really foam? I have some AR-2ax's from the early 1907s, and
the surrounds appear to be rubberized cloth (which should make a better
seal than foam). They have survived over 30 years of California smog
with no obvious degradation. I do not remember seeing foam on any of the
old AR speakers (AR 1-4) I have seen at the swap meets.

Its not foam or rubber. It's treated cloth. Some kind of substance. I've
seen the treatment seep down, but the stuff might be different on different
drivers.

Greg

 

[dave]

On 06/11/2014 11:36 AM, jfeng@my-deja.com wrote:

On Monday, June 9, 2014 7:21:13 AM UTC-7, dave wrote:

I have some AR4x that appear to
have the original surrounds from ca 1968. All foam not created
equal. Refoaming is not difficult.
Are yours really foam? I have some AR-2ax's from the early 1907s, and the surrounds appear to be rubberized cloth (which should make a better seal than foam). They have survived over 30 years of California smog with no obvious degradation. I do not remember seeing foam on any of the old AR speakers (AR 1-4) I have seen at the swap meets.

I've had a bunch with cloth surrounds too. I have a pair of AR2 in the
middle of a refinishing project. These are AR4x which were "mass
produced" by Cambridge standards. They have been on a shelf on my patio
for at least 10 years as the tweets (HF drivers) are smoked; the rubber
surrounds are still alive and well. I am 30 miles North of UCLA. The air
here is not the cleanest. Houston (Petro Metro) will eat your surrounds
faster than anywhere.

 

[jfeng@my-deja.com]

On Wednesday, June 11, 2014 8:49:22 PM UTC-7, GS wrote:

Its not foam or rubber. It's treated cloth. Some kind of substance.
I've seen the treatment seep down, but the stuff might be different
on different drivers.

Greg
On reflection, I would guess that the cloth is impregnated with silicone rubber. I do not remember any of it oozing down; however, my sample size is small. Still, foam does not make sense for acoustic suspension woofers.

 

[William Sommerwerck]

> Foam does not make sense for acoustic suspension woofers.

If it were porous, it wouldn't make sense for any woofer. But it isn't
particularly porous.

 

[dave]

On 06/13/2014 05:19 PM, William Sommerwerck wrote:

Foam does not make sense for acoustic suspension woofers.

If it were porous, it wouldn't make sense for any woofer. But it isn't
particularly porous.

Two major divisions in foam, closed cell, open cell. Open cell is what
we use for microphones pop filters, closed cell for gasketing, etc.

 

[William Sommerwerck]

"dave" wrote in message
news:HIadnQALpsXe0AHOnZ2dnUVZ_vadnZ2d@earthlink.com...
On 06/13/2014 05:19 PM, William Sommerwerck wrote:

Foam does not make sense for acoustic suspension woofers.

If it were porous, it wouldn't make sense for any woofer.
But it isn't particularly porous.

Two major divisions in foam, closed cell, open cell. Open cell is what we
use for microphones pop filters, closed cell for gasketing, etc.

Thanks for the clarification.