George wrote:
Hey guys, a local pawn shop has a pair of JBL E90's for sale, included with
them is a pair of E20 bookshelf speakers. The only problem is two of the
woofers are dented in,

Do you mean the round dust caps are dented on the front of each speaker
driver? If only the dust caps are dented in, don't worry about it.
They're only dust caps and don't affect the sound.

one on the E90 and one on the bookshelf's. I
contacted JBL and they said they would ship out two brand new woofers for 80
bucks. Do you think I should buy them anyway and just fix them or let them
go. The E90's go for anywhere between 250 and 400 dollars and the smaller
ones are 160 a piece, any thoughts?

I'm not familiar with these speakers. If you like 'em, buy 'em.

Also, I'm crossposting my comments to rec.audio.tech, where you might
get some technical advice.

Thanks
George

it's the round part in the middle of the woofer, the one on the e90 is only
dented a bit but the bookshelf one is crushed completely in, the dust cap I
mean, the rest of the woofer is ok. Do you think its still a good deal? I
heard the were decent speakers, I'm mad because a week ago they were in
perfect condition and should have bought them then but didn't know how good
they were, when I found out I went back and the dustcaps were crushed in.

Thanks
George

wrote in message
oups.com...

George wrote:
Hey guys, a local pawn shop has a pair of JBL E90's for sale, included
with
them is a pair of E20 bookshelf speakers. The only problem is two of the
woofers are dented in,

Do you mean the round dust caps are dented on the front of each speaker
driver? If only the dust caps are dented in, don't worry about it.
They're only dust caps and don't affect the sound.

one on the E90 and one on the bookshelf's. I
contacted JBL and they said they would ship out two brand new woofers
for 80
bucks. Do you think I should buy them anyway and just fix them or let
them
go. The E90's go for anywhere between 250 and 400 dollars and the
smaller
ones are 160 a piece, any thoughts?

I'm not familiar with these speakers. If you like 'em, buy 'em.

Also, I'm crossposting my comments to rec.audio.tech, where you might
get some technical advice.

Thanks
George

George wrote:
it's the round part in the middle of the woofer, the one on the e90 is only
dented a bit but the bookshelf one is crushed completely in, the dust cap I
mean, the rest of the woofer is ok. Do you think its still a good deal? I
heard the were decent speakers, I'm mad because a week ago they were in
perfect condition and should have bought them then but didn't know how good
they were, when I found out I went back and the dustcaps were crushed in.

If they work, they work. If the cap is smashed enough to distort the
voice coil, you could have an issue; but testing will indicate whether
this is so....

jak

Thanks
George

wrote in message
oups.com...
George wrote:
Hey guys, a local pawn shop has a pair of JBL E90's for sale, included
with
them is a pair of E20 bookshelf speakers. The only problem is two of the
woofers are dented in,
Do you mean the round dust caps are dented on the front of each speaker
driver? If only the dust caps are dented in, don't worry about it.
They're only dust caps and don't affect the sound.

one on the E90 and one on the bookshelf's. I
contacted JBL and they said they would ship out two brand new woofers
for 80
bucks. Do you think I should buy them anyway and just fix them or let
them
go. The E90's go for anywhere between 250 and 400 dollars and the
smaller
ones are 160 a piece, any thoughts?
I'm not familiar with these speakers. If you like 'em, buy 'em.

Also, I'm crossposting my comments to rec.audio.tech, where you might
get some technical advice.

Thanks
George

jakdedert wrote:
George wrote:
it's the round part in the middle of the woofer, the one on the e90 is only
dented a bit but the bookshelf one is crushed completely in, the dust cap I
mean, the rest of the woofer is ok. Do you think its still a good deal? I
heard the were decent speakers, I'm mad because a week ago they were in
perfect condition and should have bought them then but didn't know how good
they were, when I found out I went back and the dustcaps were crushed in.

If they work, they work. If the cap is smashed enough to distort the
voice coil, you could have an issue; but testing will indicate whether
this is so....

BTW, it's possible to fix pushed-in dust caps. There's a trick
involving making a small hole in the dust cap, then pulling the dust
cap toward the front of the speaker. I haven't done this.

By searching the web and newsgroups, you could probably find
instructions for pulling the dust caps outward so that they're not
pushed in.

Another BTW: The reason dust caps are so easy to push in is that
there's a vacuum inside the dust cap.

OTOH, this sort of thing like pushed-in dust caps may really bother
you. If you buy the speakers with the pushed-in dust caps, will you
really be happy? Life's too short to be unhappy and there are about a
zillion other speakers you could buy instead. Will repairing the
speakers make you happy?

And keep in mind that almost anything you can find in pawn shop will
probably also be found on eBay. (Actually, a lot of pawn shops sell
through eBay.) Anyway, you might want to search eBay now and see if you
can get the same speakers there, but w/o the pushed-in dust caps.

jak

Thanks
George

wrote in message
oups.com...
George wrote:
Hey guys, a local pawn shop has a pair of JBL E90's for sale, included
with
them is a pair of E20 bookshelf speakers. The only problem is two of the
woofers are dented in,
Do you mean the round dust caps are dented on the front of each speaker
driver? If only the dust caps are dented in, don't worry about it.
They're only dust caps and don't affect the sound.

one on the E90 and one on the bookshelf's. I
contacted JBL and they said they would ship out two brand new woofers
for 80
bucks. Do you think I should buy them anyway and just fix them or let
them
go. The E90's go for anywhere between 250 and 400 dollars and the
smaller
ones are 160 a piece, any thoughts?
I'm not familiar with these speakers. If you like 'em, buy 'em.

Also, I'm crossposting my comments to rec.audio.tech, where you might
get some technical advice.

Thanks
George

wrote in message
oups.com...

jakdedert wrote:
George wrote:
it's the round part in the middle of the woofer, the one on the e90
is only
dented a bit but the bookshelf one is crushed completely in, the
dust cap I
mean, the rest of the woofer is ok. Do you think its still a good
deal? I
heard the were decent speakers, I'm mad because a week ago they
were in
perfect condition and should have bought them then but didn't know
how good
they were, when I found out I went back and the dustcaps were
crushed in.

If they work, they work. If the cap is smashed enough to distort the
voice coil, you could have an issue; but testing will indicate
whether
this is so....

BTW, it's possible to fix pushed-in dust caps. There's a trick
involving making a small hole in the dust cap, then pulling the dust
cap toward the front of the speaker. I haven't done this.

By searching the web and newsgroups, you could probably find
instructions for pulling the dust caps outward so that they're not
pushed in.

Another BTW: The reason dust caps are so easy to push in is that
there's a vacuum inside the dust cap.

OTOH, this sort of thing like pushed-in dust caps may really bother
you. If you buy the speakers with the pushed-in dust caps, will you
really be happy? Life's too short to be unhappy and there are about a
zillion other speakers you could buy instead. Will repairing the
speakers make you happy?

And keep in mind that almost anything you can find in pawn shop will
probably also be found on eBay. (Actually, a lot of pawn shops sell
through eBay.) Anyway, you might want to search eBay now and see if
you
can get the same speakers there, but w/o the pushed-in dust caps.

jak

Thanks
George

wrote in message
oups.com...
George wrote:
Hey guys, a local pawn shop has a pair of JBL E90's for sale,
included
with
them is a pair of E20 bookshelf speakers. The only problem is two
of the
woofers are dented in,
Do you mean the round dust caps are dented on the front of each
speaker
driver? If only the dust caps are dented in, don't worry about it.
They're only dust caps and don't affect the sound.

one on the E90 and one on the bookshelf's. I
contacted JBL and they said they would ship out two brand new
woofers
for 80
bucks. Do you think I should buy them anyway and just fix them or
let
them
go. The E90's go for anywhere between 250 and 400 dollars and the
smaller
ones are 160 a piece, any thoughts?
I'm not familiar with these speakers. If you like 'em, buy 'em.

Also, I'm crossposting my comments to rec.audio.tech, where you
might
get some technical advice.

Thanks
George

neilnewsgroups wrote ...
Another BTW: The reason dust caps are so easy to push
in is that there's a vacuum inside the dust cap.

The reason dust caps are so easy to push in is that they
are made of very thin metal foil. There is only atmospheric
pressure on both sides of the cap. Look at any cross-section
of a conventional cone speaker to see that there are no
"sealed" areas.

Richard Crowley wrote:

neilnewsgroups wrote ...
Another BTW: The reason dust caps are so easy to push
in is that there's a vacuum inside the dust cap.

The reason dust caps are so easy to push in is that they
are made of very thin metal foil. There is only atmospheric
pressure on both sides of the cap. Look at any cross-section
of a conventional cone speaker to see that there are no
"sealed" areas.

Some are paper, felt or plastic, it depends on the speaker.

One trick is using painters tape (like masking tape but not as sticky)
to pull out the dents, another is using a vacuum nozzle

wrote in message
oups.com...

wrote:
Another BTW: The reason dust caps are so easy to push in is that
there's a vacuum inside the dust cap.

No, there's not. Why would there be? If there was a vacuum inside
the dustcap, there would be a resultant force that would bias the
cone inwards due to the atmospheric pressure on the outside of
the dustcap. A dust cap that's 2" in diameter, for example, that had
a vacuum on one side would experience a net inward force due
to atmospheric pressue of over 40 pounds. Does that make sense?

How would such a vacuum be maintained? There's no intrinsic seal
that's going to prevent pretty rapid and complete equalization of the
pressure front and aft of the dustcap.

The reason dustcaps are so easy to push in is that they're easy to
push in. They're made of materials that are not very strong, for the
most part, and they're easy target for kids and the like.

The best way to avoid dents in your dust cap is to leave the grille in
place. It looks nicer, and protects the dust cap from curious fingers and
paws.

Norm

wrote in message
...

wrote in message
oups.com...

wrote:
Another BTW: The reason dust caps are so easy to push in is that
there's a vacuum inside the dust cap.

No, there's not. Why would there be? If there was a vacuum inside
the dustcap, there would be a resultant force that would bias the
cone inwards due to the atmospheric pressure on the outside of
the dustcap. A dust cap that's 2" in diameter, for example, that had
a vacuum on one side would experience a net inward force due
to atmospheric pressue of over 40 pounds. Does that make sense?

How would such a vacuum be maintained? There's no intrinsic seal
that's going to prevent pretty rapid and complete equalization of the
pressure front and aft of the dustcap.

The reason dustcaps are so easy to push in is that they're easy to
push in. They're made of materials that are not very strong, for the
most part, and they're easy target for kids and the like.

The best way to avoid dents in your dust cap is to leave the grille in
place. It looks nicer, and protects the dust cap from curious fingers and
paws.

Doing so tends to cause some substantial differences in the FR of the
speaker, unless the grill was factored into the design, which is not usually
the case IME.

wrote:
wrote:
wrote:
Another BTW: The reason dust caps are so easy to push in is that
there's a vacuum inside the dust cap.
No, there's not.

Thank you for correcting that. When I wrote the above, I wasn't quite
sure myself. Seems like I've seen a dust cap somewhere made of some
sheer material that couldn't hold a vacuum anyway.

As well as the methods already mentioned in this thread for pulling out
dents in dust caps, there's another method that I've heard of, but
haven't tried: making a pinhole in the front of the dustcap, then
inserting a bent pin or or other L-shaped thing and pulling out the
dents from inside the dust cap. I've never tried this.

Actually that was mentioned by another poster, but whether accidentally
or on purpose, he sent it directly to my inbox instead of here. I've
done it. If the dent is not too severe, it can work (depending on the
cap material...I wouldn't try it with a metal cap).

If I see a speaker driver with a dented dust cap, I know I don't want
that and I don't want to fix it either, so I never buy speakers with
dented dustcaps. Been lucky enough so far that I've never dented a dust
cap myself.

It's pretty cosmetic, actually...as others have pointed out.

jak
(snip)

wrote:
The best way to avoid dents in your dust cap is to leave the grille in
place. It looks nicer, and protects the dust cap from curious fingers and
paws.

Doing so tends to cause some substantial differences in the FR of the
speaker, unless the grill was factored into the design, which is not usually
the case IME.

That the grill causes SOME difference, yes. That those differences
are substantial, probably not. Typically reasonable grill perturb the
upper end response on the order of 1 dB or less, and are of the same
magnitude and effect as moving the measurement position a few
inches. The frequency response errors caused by comb filtering effect
from floor and furniture reflections are typically much worse.

wrote:
wrote:
The best way to avoid dents in your dust cap is to leave the grille in
place. It looks nicer, and protects the dust cap from curious fingers and
paws.

Doing so tends to cause some substantial differences in the FR of the
speaker, unless the grill was factored into the design, which is not usually
the case IME.

That the grill causes SOME difference, yes. That those differences
are substantial, probably not. Typically reasonable grill perturb the
upper end response on the order of 1 dB or less, and are of the same
magnitude and effect as moving the measurement position a few
inches. The frequency response errors caused by comb filtering effect
from floor and furniture reflections are typically much worse.

I was working from memory of the measurements I have seen on spekaers
tested and/or designed by Joe D'Appolito in Speaker Builder and
AudioXpress. The comaprisons always looked pretty drastic on the HF
response IIRC.

I never buy anything from pawnbrokerages. I consider them a blight on
society in general.

Bret Ludwig wrote:
I never buy anything from pawnbrokerages. I consider them a blight on
society in general.


They are nearly the first place I turn when looking for new (old) gear.
Just today I bought a pair of mint EV ND767's for around $100.

jak