[Rick Ruskin]

The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed. I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures. Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



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[Neil[_9_]]

On 9/8/2019 12:31 PM, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed. I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures. Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?

I suggest giving them a few days to break in before doing anything else.
Play a lot of music that pushes the low range! ;-)

--
best regards,

Neil

[geoff]

On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed. I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures. Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



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The 4315 is a ported cabinet, so a slight lack of seal (unlikely anyway
as the seal is, unless broken, a continuous ring) shouldn't have a
profound effect. More likely the new foams just a little stiff and
should loosen up with a bit of use to run them in.

geoff

[Phil Allison[_4_]]

Rick Ruskin wrote:
----------------

The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.


** So there is now more low bass.


I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.


** Having more bass contradicts this idea.

Woofers with disintegrating foam surrounds output weak and/or distorted bass.

Seems you got used to it.



..... Phil

[Rick Ruskin[_2_]]

On Sun, 8 Sep 2019 18:34:57 -0700 (PDT), Phil Allison
wrote:

Rick Ruskin wrote:
----------------

The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.


** So there is now more low bass.

No. Slightly less bass and less defined bass, especially with regard
to bass parts in mixes I'm familiar with. .Impact sources like kick
drums sound about right.

I just want to know if a poor seal would make that difference and
whether there is a way to test the integrity of the seal with the
speakers still mounted.




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[Trevor]

On 9/09/2019 8:33 am, geoff wrote:
On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.Â* I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.Â* Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



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The 4315 is a ported cabinet, so a slight lack of seal (unlikely anyway
as the seal is, unless broken, a continuous ring) shouldn't have a
profound effect. More likely the new foams just a little stiff and
should loosen up with a bit of use to run them in.

Or more likely the new foams are a little stiffer than the old ones and
won't change at all. "running in" is more about you simply getting used
to the sound than any real and permanent measureable change in actual
performance.

[geoff]

On 9/09/2019 10:07 pm, Trevor wrote:
On 9/09/2019 8:33 am, geoff wrote:
On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.Â* I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.Â* Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



---
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The 4315 is a ported cabinet, so a slight lack of seal (unlikely
anyway as the seal is, unless broken, a continuous ring) shouldn't
have a profound effect. More likely the new foams just a little stiff
and should loosen up with a bit of use to run them in.

Or more likely the new foams are a little stiffer than the old ones and
won't change at all. "running in" is more about you simply getting used
to the sound than any real and permanent measurable change in actual
performance.

In the past I have 'run in' a bass driver with noticeable change
(measured), and without hearing them at all during the process to
confuse matters.

Both a LF resonance and a level changed over 2 days at moderate power4
level - F down by a few Hz and and level up by a fraction of a dB. Same
position signal distance and everything else I could think of. Just
tilted back up from the sound-deadening wadding that it had been
inclined onto in order to cut down the noise in the basement.

This was elasticised paper surround.May not be the case for all drivers
or surround materials.

geoff

[Neil[_9_]]

On 9/9/2019 6:07 AM, Trevor wrote:
On 9/09/2019 8:33 am, geoff wrote:
On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.Â* I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.Â* Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



---
This email has been checked for viruses by AVG.
https://www.avg.com


The 4315 is a ported cabinet, so a slight lack of seal (unlikely
anyway as the seal is, unless broken, a continuous ring) shouldn't
have a profound effect. More likely the new foams just a little stiff
and should loosen up with a bit of use to run them in.

Or more likely the new foams are a little stiffer than the old ones and
won't change at all. "running in" is more about you simply getting used
to the sound than any real and permanent measureable change in actual
performance.

I've had my mid-range 8" JBL speakers re-foamed by JBL 3 times over the
last 40 years. Each time there were audible and measurable changes in
their frequency spectrum when first re-installed. They stabilized after
a few days of use, and after a slight adjustment to the cross-over
levels returned to a good state.

These *are* physical objects, which means that in the real world, no two
will be identical.

--
best regards,

Neil

[Scott Dorsey]

geoff wrote:
On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed. I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures. Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?

The 4315 is a ported cabinet, so a slight lack of seal (unlikely anyway
as the seal is, unless broken, a continuous ring) shouldn't have a
profound effect. More likely the new foams just a little stiff and
should loosen up with a bit of use to run them in.

Agreed. But I suggest that likely the new foam is probably closer to what
JBL initially intended than the old, failing foam.

I agree that breaking them in is the first step... play some Bootsy Collins
records at high volume when you're not in the room and see if it loosens up.

BUT... if they just replaced the foam and didn't do a complete recone then
changing the foam shouldn't make a big difference in driver Fs.... most of
the resistance is coming from the spider and not from the surround.

So my guess is that you're experiencing the speakers working properly and
you're not liking that flabby JBL bass. Try moving them closer to the wall.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

geoff wrote:
In the past I have 'run in' a bass driver with noticeable change
(measured), and without hearing them at all during the process to
confuse matters.

Both a LF resonance and a level changed over 2 days at moderate power4
level - F down by a few Hz and and level up by a fraction of a dB. Same
position signal distance and everything else I could think of. Just
tilted back up from the sound-deadening wadding that it had been
inclined onto in order to cut down the noise in the basement.

This was elasticised paper surround.May not be the case for all drivers
or surround materials.

I think this makes more of a difference in the spider than in the surround.
If the spider is already broken-in, it should make much less difference.

I also think it makes more of a difference with paper surrounds than with
foam surrounds.

But yes, the difference is sometimes not subtle.
--scott

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

[geoff]

On 10/09/2019 1:48 am, Scott Dorsey wrote:
..

Agreed. But I suggest that likely the new foam is probably closer to what
JBL initially intended than the old, failing foam.



That certainly was the case with my domestic hi-fi speakers. Bought them
'used' in an online auction, and when the cabinets opened (drivers are
internal) I could see through the foam of two driver through to the
bottom of the cabinet !

The foam had been eaten by the bacteria, decomposed, or whatever it is
that happens.

KEF Reference R107. Pretty much flat down to 20Hz.

geoff

[Phil Allison[_4_]]

Rick Ruskin wrote:

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


The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.


** So there is now more low bass.

No. Slightly less bass and less defined bass,

** Makes no sense.

Tight and defined = less low bass and more upper bass.

The *definition" is in the harmonics and transients.


Impact sources like kick drums sound about right.


** So what is you gripe exactly ?

I just want to know if a poor seal would make that difference


** Not a chance.

Small air leaks can create noises noticeable with sine wave testing.



..... Phil



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[Trevor]

On 9/09/2019 8:56 pm, geoff wrote:
On 9/09/2019 10:07 pm, Trevor wrote:
On 9/09/2019 8:33 am, geoff wrote:
On 9/09/2019 4:31 am, Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.Â* I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.Â* Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



---
This email has been checked for viruses by AVG.
https://www.avg.com


The 4315 is a ported cabinet, so a slight lack of seal (unlikely
anyway as the seal is, unless broken, a continuous ring) shouldn't
have a profound effect. More likely the new foams just a little stiff
and should loosen up with a bit of use to run them in.

Or more likely the new foams are a little stiffer than the old ones
and won't change at all. "running in" is more about you simply getting
used to the sound than any real and permanent measurable change in
actual performance.

In the past I have 'run in' a bass driver with noticeable change
(measured), and without hearing them at all during the process to
confuse matters.

Both a LF resonance and a level changed over 2 days at moderate power4
level - F downÂ* by a few Hz and and level up by a fraction of a dB. Same
position signal distance and everything else I could think of. Just
tilted back up from the sound-deadening wadding that it had been
inclined onto in order to cut down the noise in the basement.

This was elasticised paper surround.May not be the case for all drivers
or surround materials.

Yes there CAN be a change during "running in", but not as often as those
who rely on subjective listening alone like to imagine. Now my
experience in measuring speakers isn't extensive enough to make wild
claims, but I'll simply agree with Dick Pierce on the matter.

[[email protected]]

Op you can try sealing the port to see what effect that has on the sound and if you prefer it. M

[Les Cargill[_4_]]

Rick Ruskin wrote:
The low end of my JBL 4315's sounds sounds less tight and defined
after having the 12" drivers refoamed.

Foam gets more brittle and the center frequency of the Q it represents
moves upward over time.

I'm wondering if this could be
do to them not being sealed tightly enough with the enclosures.

I'm thinking "not tightly coupled enough" as more of a chuff thing.

Is
there any way to test for a proper seal without having to dismount
them and instal yet a another set of new seals?



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--
Les Cargill