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Put Fiberglass in Box?

T

Tapper

Dec 8, 2007
53
1
Canyon Lake, Texas
#1
I just traded into a early 80's fender Bassman Compact combo with a single 15". it had been retrofitted with an Altec 416, and sounds pretty good. but when I took the speaker out to better fit it...it had to have slots cut to allow it to sit nicely flush (had to front load it), I noticed the cabinet had no acoustic "padding" inside. Will this cabinet benefit from fiberglass or ?? lining? It is bottom vented solid wood (not particle board) box.:confused:
 
#4
Tapper said:
Will this cabinet benefit from fiberglass or ?? lining? It is bottom vented solid wood (not particle board) box.:confused:
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All cabs should be fully lined with an inch to an inch and a half of either open cell polyurethane foam or polyester batting. Fiberglass is OK too, but far from user friendly (scratch, scratch).
 
#7
Tapper said:
Will do! Thanks! Apparently this cabinet was never lined...does Fender not line their bass cabs?...or was this one of the many "economies" CBS enacted?:hmm:
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You'd be amazed how many cabs from even the best names are either under damped or not damped at all. When corners are cut it's always where it can't be seen. :rollno:
 
#8
It'll help a lot, all I'd say is stop your damping before you get too close to where the tuning port opens up to the inside of the cabinet. You don't want to inadvertently change the size of the port opening as that is tuning the box to the speaker. Otherwise pad all the other surfaces. (you probably don't have to put any on the baffle where the speaker is mounted, there's probably not that much wall left after the speaker and tuning port are cut into it.) It will get rid of that boxy, woody sound.
 
#9
sorry to argue but Im gonna go in complete opposite direction.

screw padding, great for pas and keyboards. not bass or guitar.

y?

that mid range definition, and lack of crossover? would be detrimental to my sound. a lil bit of feedback and "muddy ness" adds so much to a band. makes such a fuller sound. i dont want every note to come though pirceingly clean and push though every thing, the idea is to make music, not to be a solo piece esp. with bass idk maybe im alone here. but I like the nat. distortion that having multiple speakers in a box gives you it shapes my sound.

but thats where we really differ. everyone here thinks all of you sound should be created in the pre. right? and everything else afterwards should only be amplifying that sound? oh well 2 different worlds. I guess it comes down to which do you like more, sounding like a keyboard or a guitar?
 
#10
billfitzmaurice said:
You'd be amazed how many cabs from even the best names are either under damped or not damped at all. When corners are cut it's always where it can't be seen. :rollno:
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Bill, as I'm sure you know, only the back wall of B-15 cabs were ever dampened. I really dig the sounds of them as they are, but would I hear a noticeable improvement if I were to line them with foam all the way around? And would I line the baffle as well? Would more lining affect the performance of the double baffle cab, seeing as how it shunts the low end to right in front of the driver?
 
#11
JimmyM said:
Bill, as I'm sure you know, only the back wall of B-15 cabs were ever dampened. I really dig the sounds of them as they are, but would I hear a noticeable improvement if I were to line them with foam all the way around?
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Probably. Midrange waves reflect back to the cone off any unlined surface within the cab, and depending on how long the pathway is and their wavelengths they'll arrive there at various phase angles, either adding to or detracting from the cabs output, resulting in numerous response peaks and valleys. Lining the baffle won't affect the midrange, but doing so can clean up standing wave development between the baffle and back, getting rid of midbass mud. Lining has no efect on the low bass, the wavelengths are too long.
 
#15
wave rider said:
If standing waves are creating the problem, would a cabinet with non-parallel sides also need the dampening material?

=wr=
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Standing waves are not creating a problem per se, but if you can prevent them there's no reason why not. The 'problem' is sound waves coming off the back of the cone are reflected back to it by any undamped surface in the cab. Non-parallel sides spread the reflections over a wider bandwith, which helps, but in and of itself it's no cure.
 
#16
bottomend! said:
Great thread! Can someone post a pic of the kind of material that was mentioned above?
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[Invalid or Expired Link Removed]

That was the best I could do on short notice. Naturally you don't need 30 yards of it for $68, nor do you need it to be that good, but that's what it looks like. Basically it's foam sheets.
 
#17
billfitzmaurice said:
Standing waves are not creating a problem per se, but if you can prevent them there's no reason why not. The 'problem' is sound waves coming off the back of the cone are reflected back to it by any undamped surface in the cab. Non-parallel sides spread the reflections over a wider bandwith, which helps, but in and of itself it's no cure.
Click to expand...

Thanks Bill, I really appreciated your willingness to share your knowledge.

Would a spray on damping material (similar to the insides of car doors) work as well?

=wr=
 
#19
JimmyM said:
[Invalid or Expired Link Removed]

That was the best I could do on short notice. Naturally you don't need 30 yards of it for $68, nor do you need it to be that good, but that's what it looks like. Basically it's foam sheets.
Click to expand...

You rock! thanks a million! I've got cabs galore and look forward to stuffing each and everyone of them....
 
#20
bottomend! said:
You rock! thanks a million! I've got cabs galore and look forward to stuffing each and everyone of them....
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Line, don't stuff. If you stuff them you'll change the cab's Q characteristic and possibly kill the bass response. OTOH if you've got a sealed cab that's boomy stuffing it will tame the boom.
 

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