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Question re proper sealing of woofers with enclosure



 
 
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  #1  
Old September 8th 19, 05:31 PM posted to rec.audio.pro
Rick Ruskin
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Posts: 354
Default Question re proper sealing of woofers with enclosure

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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  #2  
Old September 8th 19, 08:32 PM posted to rec.audio.pro
Neil[_9_]
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Posts: 160
Default Question re proper sealing of woofers with enclosure

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
  #3  
Old September 8th 19, 11:33 PM posted to rec.audio.pro
geoff
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Posts: 1,543
Default Question re proper sealing of woofers with enclosure

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?
>
>
>
> ---
> 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.

geoff
  #4  
Old September 9th 19, 02:34 AM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 451
Default Question re proper sealing of woofers with enclosure

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

  #5  
Old September 9th 19, 04:02 AM posted to rec.audio.pro
Rick Ruskin[_2_]
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Posts: 1
Default Question re proper sealing of woofers with enclosure

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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  #6  
Old September 9th 19, 11:07 AM posted to rec.audio.pro
Trevor
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Posts: 2,760
Default Question re proper sealing of woofers with enclosure

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.* 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?
>>
>>
>>
>> ---
>> 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.
  #7  
Old September 9th 19, 11:56 AM posted to rec.audio.pro
geoff
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Posts: 1,543
Default Question re proper sealing of woofers with enclosure

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.* 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?
>>>
>>>
>>>
>>> ---
>>> 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 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
  #8  
Old September 9th 19, 12:10 PM posted to rec.audio.pro
Neil[_9_]
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Posts: 160
Default Question re proper sealing of woofers with enclosure

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.* 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?
>>>
>>>
>>>
>>> ---
>>> 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
  #9  
Old September 9th 19, 02:48 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,651
Default Question re proper sealing of woofers with enclosure

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."
  #10  
Old September 9th 19, 02:50 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,651
Default Question re proper sealing of woofers with enclosure

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."
 




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