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Questions on replacing speaker stuffing.

Kreshna

Kreshna

...but I have to know.
The speaker stuffing inside my JBL 120Ti has become thin and dried up, and while it doesn't seem to affect tonality and details, sometimes I get the feeling that the sound is "boxy". The questions are:

(1) what is the stuffing materials used inside the 120Tis? I've googled but failed to find the material type.

(2) it's likely the 120Tis use fiberglass stuffing, since fiberglass seems to be the most common type. However, if I replace it with wool stuffing (like this), how much it will change the speaker's sound characteristics? And will it be better or worse?

(3) too bad the 120Tis' cutaway doesn't show its correct stuffing layout, but based on common sense (and after peeking into the speakers after taking off the woofers), it seems the stuffing layout is as follows:
- all sides (front, back, left, right, top, bottom) should be covered by stuffing.
- the stuffing covering the back side should be cut out (rectangular-shaped) to give way for the crossover.
- the stuffing covering the front should be cut out (circles) to give way for the back of the woofer.
- however, it seems the back of the tweeter and midrange are still covered by the front stuffing. There are only small cuts for cables, but the driver's backside is still covered by the stuffing materials.

Am I correct so far? Any further tips?

Many thanks.
 
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I've used polyfill for awhile now and with very good results. Sure beats itchy fiberglass.
 
polyfill comes in sheets-don't be afraid to experiment-it's not like you can't take it back out.
 
The only thing to be careful of is overstuffing. I've used the old stuffing from a poly pillow to great affect as long as I was careful about not getting it too tight. Loose and easy but full seems to work best for me. Poly fill is looser and won't dampen as well as wool stuffing but it is cheap and easy to find so experimenting with it is very easy to do.
 
Not to hijack a good thread but,
“The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.” William Arthur Ward
I wonder what the idealist would do?
 
Njoy-Music said:
The only thing to be careful of is overstuffing. I've used the old stuffing from a poly pillow to great affect as long as I was careful about not getting it too tight. Loose and easy but full seems to work best for me. Poly fill is looser and won't dampen as well as wool stuffing but it is cheap and easy to find so experimenting with it is very easy to do.
Click to expand...
I see, thanks. What amount of polyfill will result in balance between tightness and bass response? Probably 3/4 of the box volume?


CopperWizard said:
Not to hijack a good thread but,
“The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.” William Arthur Ward
I wonder what the idealist would do?
Click to expand...
So does it mean we have to be careful and conservative when replacing the stuffing (ie, staying with the original materials - if it's fiberglass then replace it with fiberglass, etc), or should we take more freedom in doing so? Like replacing fiberglass stuffing with wool?
 
CopperWizard said:
Not to hijack a good thread but,
“The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.” William Arthur Ward
I wonder what the idealist would do?
Click to expand...

Nice quote. I think the idealist would take hundreds of measurements of the wind, conduct a thorough statistical analysis of all the variables associated with the wind and then put together a 50 pg plan to maximize the enjoyment of the wind. :smoke:
 
Around here we would call that a Strategic Plan, perhaps a Five Year or Ten Year Plan. They normally go on the shelf and no one reads them after that.
 
1 lb per square foot of volume. I use 2" thick poly bats from joanne fabrics. easy to work with, more dense than the spun polyfill and really dampens the box.
 
poly stuffing is a very poor material choice to damp a speaker with. Poly stuffing has a very limited bandwidth of damping/absorption and is of little use at frequencies below 300 Hz. This is evident when you over stuff with polyfil as all it does at low frequencies is to take up available cabinet volume and that is why people lose bass not because it works so well. Regular fiberglass or rockwool is much more effective and high density fiberglass is the single best material see Owens Corning 700 series HD fiberglass which is the most used material for sound treatment of low frequencies. Why don't you just leave your speakers alone? If you must experiment then you can away replace the original material if you remove it carefully first. If this is too much for you to do then walk away from experiments you don't want to do.

My Klipsch Heresy 3 are about 95% solid stuffed with high density fiberglass (sealed cabinets) and the bass extension is exceptional. With reflex cabinet you can also use HD fiberglass but you need to cover it so it cannot escape the cabinet and you must leave least a cubic foot of volume around the vents or they will not be effectively driven. You must have a resonant volume for a reflex vent to work properly. If you have reflex vents and this sounds too difficult then it likely is so leave your damping alone. If you are willing to do some work then by all means experiment as I said you can always put things back the way they were. You need to remember that most cabinets are only damped with the minimum of damping material of the cheapest variety and only to absorb mid frequencies to help keep them from reflecting out of the cabinet via the woofer or mid cone(s). With the right material damping can provide you with as much as 25% (theoretical) more apparent cabinet volume. What that means is that your speaker thinks it is in a larger cabinet than it really is and that means that you can (depending upon the driver used) obtain deeper bass extension. Bigger (volume) is generally better. I have learned that how HD fiberglass is installed has a dramatic affect upon its performance. HD needs to be installed so that the pressure wave of the driver enters into the cut edge of the material not into the flat surfaces of the material. The flat surfaces of the HD board is high in density (stiff) and it is reflective and not as absorbent as the edge of the material. Improper installation of HD fiberglass will result in much less than optimal performance. I hope that this is of interest and that it helps you. Best regards Moray James.
 
moray james said:
poly stuffing is a very poor material choice to damp a speaker with. Poly stuffing has a very limited bandwidth of damping/absorption and is of little use at frequencies below 300 Hz. This is evident when you over stuff with polyfil as all it does at low frequencies is to take up available cabinet volume and that is why people lose bass not because it works so well. Regular fiberglass or rockwool is much more effective and high density fiberglass is the single best material see Owens Corning 700 series HD fiberglass which is the most used material for sound treatment of low frequencies. Why don't you just leave your speakers alone? If you must experiment then you can away replace the original material if you remove it carefully first. If this is too much for you to do then walk away from experiments you don't want to do.

My Klipsch Heresy 3 are about 95% solid stuffed with high density fiberglass (sealed cabinets) and the bass extension is exceptional. With reflex cabinet you can also use HD fiberglass but you need to cover it so it cannot escape the cabinet and you must leave least a cubic foot of volume around the vents or they will not be effectively driven. You must have a resonant volume for a reflex vent to work properly. If you have reflex vents and this sounds too difficult then it likely is so leave your damping alone. If you are willing to do some work then by all means experiment as I said you can always put things back the way they were. You need to remember that most cabinets are only damped with the minimum of damping material of the cheapest variety and only to absorb mid frequencies to help keep them from reflecting out of the cabinet via the woofer or mid cone(s). With the right material damping can provide you with as much as 25% (theoretical) more apparent cabinet volume. What that means is that your speaker thinks it is in a larger cabinet than it really is and that means that you can (depending upon the driver used) obtain deeper bass extension. Bigger (volume) is generally better. I have learned that how HD fiberglass is installed has a dramatic affect upon its performance. HD needs to be installed so that the pressure wave of the driver enters into the cut edge of the material not into the flat surfaces of the material. The flat surfaces of the HD board is high in density (stiff) and it is reflective and not as absorbent as the edge of the material. Improper installation of HD fiberglass will result in much less than optimal performance. I hope that this is of interest and that it helps you. Best regards Moray James.
Click to expand...

Very interesting - I have some OC 703, I will experiment. I can cut it into strips and lay it on its side along the bottom of the cabs (and sides if needed) so the cut edges face the backs of the drivers. I think my L300's just have the stock fiberglass in them now, and its old and turning to dust - never thought to try the 703 in this application - thanks for the idea Moray!
 
moray james said:
poly stuffing is a very poor material choice to damp a speaker with. Poly stuffing has a very limited bandwidth of damping/absorption and is of little use at frequencies below 300 Hz. This is evident when you over stuff with polyfil as all it does at low frequencies is to take up available cabinet volume and that is why people lose bass not because it works so well. Regular fiberglass or rockwool is much more effective and high density fiberglass is the single best material see Owens Corning 700 series HD fiberglass which is the most used material for sound treatment of low frequencies. Why don't you just leave your speakers alone? If you must experiment then you can away replace the original material if you remove it carefully first. If this is too much for you to do then walk away from experiments you don't want to do.

My Klipsch Heresy 3 are about 95% solid stuffed with high density fiberglass (sealed cabinets) and the bass extension is exceptional. With reflex cabinet you can also use HD fiberglass but you need to cover it so it cannot escape the cabinet and you must leave least a cubic foot of volume around the vents or they will not be effectively driven. You must have a resonant volume for a reflex vent to work properly. If you have reflex vents and this sounds too difficult then it likely is so leave your damping alone. If you are willing to do some work then by all means experiment as I said you can always put things back the way they were. You need to remember that most cabinets are only damped with the minimum of damping material of the cheapest variety and only to absorb mid frequencies to help keep them from reflecting out of the cabinet via the woofer or mid cone(s). With the right material damping can provide you with as much as 25% (theoretical) more apparent cabinet volume. What that means is that your speaker thinks it is in a larger cabinet than it really is and that means that you can (depending upon the driver used) obtain deeper bass extension. Bigger (volume) is generally better. I have learned that how HD fiberglass is installed has a dramatic affect upon its performance. HD needs to be installed so that the pressure wave of the driver enters into the cut edge of the material not into the flat surfaces of the material. The flat surfaces of the HD board is high in density (stiff) and it is reflective and not as absorbent as the edge of the material. Improper installation of HD fiberglass will result in much less than optimal performance. I hope that this is of interest and that it helps you. Best regards Moray James.
Click to expand...

I disagree with the above. I have read technical papers that have tested the benefits of polyfill in sealed and ported enclosures. The frequency plots show impressive evidence in eliminating multiple instances of resonance peaks- e.g.
http://www.nousaine.com/pdfs/Box Stuffing.pdf
http://sound.westhost.com/articles/boxstuff.htm

I have used the following material in my sealed DIY subwoofer boxes:
http://www.joann.com/15x17x2in-nufoam/5431788.html

It made the box dead quiet, smooth and extended defined bass, not just a one note wonder, and increased net enclosure volume of ~20%.

follow the lbs / cuft guidelines in the Nousaine paper and you are good to go.
 
Thank you for the info it was a good, I'm having problems with one of my pair of
Mission speakers to much bass that's boomy, inside there's just one sheet of grey
foam against the back wall and that's it. I'm thinking of removing that and adding
polyfil to it to see what happens.

Tube
 
1) considering optimist is a synonym for idealist, about the only thing different would be a lengthy harangue on the foibles of those who failed to maintain the proper amount of belief and lack of vision to see their "true" direction. The vagaries and vacillation in the wind is an example to them of being by nature chaotic and flippant as to their willingness to see the truth as he has tried to inspire in them. Therefore those occupying the boat and not holding to the true calling and direction he has been trying to inspire in them has gotten them off course and they must all repent and firmly proclaim their fealty to the correct view as he has declaimed to them or face a continued failure of attaining the fulfillment of their true goal and reward.

2) IME the polyfil has done wonders when I've used it without going crazy. The samples listed and suggestions in those links is very similar to what I'd read in doing my own research. That ended up in some much improved and smoother sound from each sealed enclosure I have used it in. I think I'll next try some of that stuff from JoAnn's to see how it works as well. I've got an old ported sub that needs some help and that looks like just the ticket. Thanks for the links!
 
the 2" thick sheets at joanne fabrics work extremely well and are easy to work with lining a box. If you cut it right you can get it to fit and stay in place without much stapling or adhesive. example a single u-shape that lines the sides and back walls- cut it a little longer and press it in place and it fits like a glove.
 
Thanks for the tip! I've got some errands to run tomorrow and I'll pick some up. Might even get some chair pads that are dying...
 
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