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Question re proper sealing of woofers with enclosure



 
 
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  #11  
Old September 9th 19, 10:35 PM posted to rec.audio.pro
geoff
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Default Question re proper sealing of woofers with enclosure

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
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  #12  
Old September 10th 19, 04:02 AM posted to rec.audio.pro
Phil Allison[_4_]
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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.

>
> 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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  #13  
Old September 10th 19, 10:16 AM posted to rec.audio.pro
Trevor
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Default Question re proper sealing of woofers with enclosure

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.¬* 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.


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.



  #14  
Old September 10th 19, 03:43 PM posted to rec.audio.pro
[email protected]
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Default Question re proper sealing of woofers with enclosure

Op you can try sealing the port to see what effect that has on the sound and if you prefer it. M
  #15  
Old September 28th 19, 03:41 AM posted to rec.audio.pro
Les Cargill[_4_]
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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.


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


--
Les Cargill
 




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