When putting fiberfill in a sealed enclosure, do you just pile it in there? Do you glue it to the sides? Staple it to the sides? Also, how critical is the thickness of the fiberfill? The spec sheet for my speakers (Infinity Reference 1230w's, 1.25 cf enclosure) calls for "all sides lined with 1-inch fiberglass or fiberfill". I've got plenty of 3/8" -1/2" bonded fiberfill (the stuff's hard to measure). Can I just layer it to get the 1", or should I just go buy some 1"?
Replies (13)
compvr15s on 05/4/2005 11:29:35
size is not critical, most people just staple it to the inside walls, works the same, can just loosly fill the enclosure.. just double the shheets up and use some short staples, will have no problems doing so, good luck
MrBrownstone on 05/4/2005 15:07:36
You're not going to see much difference if you fiberfill the box. If you are short 0.1 cf, you can use about a pound of that stuff in a 1.1cu ft box...but won't probably notice an audible difference. Most woofers have about a 10% tolerance for box size.
lessismorespl on 05/4/2005 21:26:06
I agree Mr B, never really liked that stuff, kind of like a cap, it takes out your pocket but your ears don't notice the difference. Just a waste of money and time IMHO.
swez on 05/5/2005 09:28:27
Funny how we debate this issue every so often.
Have serviced, built and installed many Pro Audio sub enclosures over the years and every one that I have ever worked on, used acoustical dampening materials.
Even the smaller Sat speakers used in restaurants, stores and retail chains have paging systems and background music, use acoustic damping materials in their MB enclosures. Have install "many" of those of late too.
Wonder why they bother to use it, if it has no purpose or value? What do those designers and fabricators know, that we are missing?
Swez
MrBrownstone on 05/5/2005 11:20:32
Swez
Some of the GREATEST car audio installations use Capacitors. Does that give them value?
Even the guy that proports the use of fiberfill, Tom Nuisaine, printed his article on how much you need vs. the impact on the woofer. Honestly, platinum-tipped RCA cables will have more of an impact.
They put it in there because of what you say, "...they are DESIGNERS.." Nothing more meritous than that. What I was getting at was that 1 POUND would equal 0.1 cuft...so if you are short 0.1 cu ft, use it.
Either way, with a woofer tolerance of 10%, I would challenge anyone to prove it made an audible difference.
Remember, Pro Audio are the people that believed that LPs are better than CDs. You need galvanized Platinum and metal foil shielding and braided materials to isolate your line level signal from the microwave oven in your house!!!! Pro audio is responsible for most of the audio 'jewelry' we have in this industry.
If you woofer box tolerances is 1.0 to 1.25 and you have 0.9--use it. If you are in between 1.0 and 1.25--you'll notice modest differences in Q...just not enough to worry about.
HERE's a long lost post from RC on the issue:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=022663#000003
and here:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=018097#000019
Richard Clark
Moderator
Member # 8
posted May 27, 2004 02:54 PM
--------------------------------------------------------------------------------
close guys but no cigar---------here's the theory and the facts--------in an acoustic suspension system the cone motion is primarily controlled by the air spring behind the cone------this spring is the trapped air in the box and since air is a compressible gas it actually makes a fairly linear spring compared to most mechanical springs-------hence the inherent low distortion of most sealed box designs----------we all should know that when a gas is compressed it heats up------we should also know that when it is rarified (expanded) it cools---------as a speaker compresses the air in a box there is a temperature rise in the gas-------when the speaker moves outward the heat is removed from the gas to the same degree (boyles law tells us that there is a direct relationship between pressure, temperature and volume of a gas)--------this constant rise and falling of temperature occurs whenever thhe speaker moves--------since this system constantly rises and falls in temperature strictly due to gas volume no real energy is lost------when energy is contained in a system and only converted it is considered to be adiabatic---------this is a mechanical pure reactance----ie a perfect spring (no such thing exists but for simplicity we will assume it does)-------remember that if we had a perfect spring and exerted 10 lbs of force to compress it the spring would exert 10 lbs of force back till it was relaxed----------since temp, volume and pressure of a gas are directly related, the spring action controlling the speaker movement is clearly defined----------now if we introduce a way for energy to be removed from the system things change--------if we introduce stuffing we are actually adding resistive losses--------as air moves through the stuffing it suffers resistive losses that produce heat-------unlike the heat that results from compressing air this heat is not recovered when the speaker reverses direction-------this heat is dissipated in the stuffing--------since some of the energy is lost this means that there is less spring power to move against the speaker when it moves---------this means that the speaker "thinks" the box is bigger since the air seems to be a weaker spring----------a system that loses energy permanently to resistive elements is know as an isothermal one-----------now the real issue is not if the theory is correct since it is clearly scientific and beyond question----------i see it as more like the amp sq issue--------we know we can measure differences but can we really hear them???---------it is easy to demonstrate that stuffing a box will lower the resonant frequency a few hertz----------but like the amp issue it is really thin ice to claim to be able to hear it in most cases--------is that a reason not to do it????-------not at all------any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense--------but don't expect miracles..........RC
--------------------
A2000Rich
lessismorespl on 05/5/2005 15:21:50
I have to agree. To me fiberfill has no known purpose, be it audible, or in performance. Going to a ported enclosure would produce more results than fiberfill. As w/ capacitors, they serve no purpose and if you read reviews and articles written on them, the only positive ones are written by people that manufacture or have some affiliation w/ a manufacturer. If you are using a prefab enclosure and one day say, "hey, I think I need to know the volume of the box and see if it is right for my subs" and you discover the enclosures volume is a bit small, why not, but will it make a big difference, no!
Richard Clark is some-one I really look up to in the car audio world. I seen the subwoofer he built using, I believe it was, an ice truck as the enclosure at a couple shows, MTX had backed him somewhat on this, it was amazing. Sorry, got off topic for sec.
Me, personally, I think I would just build a bigger enclosure rather than waste the money on fiberfill, but of course that is me. And don't even get me started on caps, after the testing and research I have done on caps, as well as reading JL's Sound School of Excellence, I'm done w/ caps.
gearhead on 05/5/2005 16:07:58
Well, the manufacturers specs are given for an enclosure with "all sides lined with 1-inch fiberglass or fiberfill". It doesn't give any specs sans fiberfill. I'm not after volume (SPL), this is for a surround sound system, so a ported box isn't what I need/want. I'll just take Mr. Clark's advice "is that a reason not to do it????-------not at all------any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense--------".
swez on 05/5/2005 20:20:05
Well, that sure makes a good case for not using fill if the box is of adequate size.
I have reviewed many sub enclosure specs over the years and many do recommend polyfill for their subs. Why? Reduces standing bass waves inside the box and does add a minute degree of apparent size of the enclosure, as the woofer sees it.
In this case, there are good reasons to use or not use fill materials. Personally, I have used it for years with fine results and will continue to do so if not only for sake of habit and the knowledge that a majority of Pro enclosures do the same. Will it hurt? No... Does it help? In a very minor way according to Leap plots I have looked at over the years.
In short, we all have our preferences and quirks. Mine is to use fill at all times. The cost and time are minimal and the results have not been negative to date. It may not be a notable difference I can detect... but I use it anyway. The choice is pretty much up to the builder of the enclosure. Am satisfied with that. (Whatever)
Swez
MrBrownstone on 05/6/2005 15:07:15
the whole argument for 'reducing' standing waves does not apply to the car audio environment. The box would need to be larger than most trunks to have an impact..and carpet on the floor of the trunk would take care of that.
There just isn't an argument for fiberfill in a car audio system unless you want to please your eyes.
Gearhead, you are misinterpreting Mr. Clark's Post. The unwritten sarcasm is that IF there is scientific proof, use the stuff. There just isn't scientific proof that you'll hear a difference or see any benefit.
Remember, like a red and a green speaker, if you can't hear the difference, is there?
Victor on 05/6/2005 15:31:28
Hmmmm...
With more than a 100 enclosures fabricated, i guess i got something to share here.
Even about capacitors.hehe..
1 - They dont exactly benifit as much as they are hyped.
2 - Not an alternative for a stable electrical system.
About the Fibrefill
1 - Rarely make an audible difference.
2 - It is also much like psycho acoustics, where its just fooling the sub ( lol and your ears if they are like as sensitive as a dog).
3 - I dont see why the issue of standing waves dont apply to Car environment.
4 - Standing waves which are generated by the rear side of the cone and due to the shape of the enclosure affect any enclosed driver.
5 - Unless you got a perfect spherical enclosure there is no way you can eliminate standing waves generated from the back of the speaker.
Using fibre fill is OPTIONAL and not a NECESSITY.
Victor...
gearhead on 05/6/2005 16:19:39
The way I read it is:
#1- "now the real issue is not if the theory is correct since it is clearly scientific and beyond question" & "it is easy to demonstrate that stuffing a box will lower the resonant frequency a few hertz".
#2- "we know we can measure differences but can we really hear them??" & "but like the amp issue it is really thin ice to claim to be able to hear it in most cases".
He's saying it DOES make a difference, you just can't HEAR the difference.
#3- "any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense". He's saying whether you can hear it or not, since it's supported by scientific evidence (#1), but not necessarily physical evidence(#2), and it's inexpensive to do, it does make sense to do it.
Victor on 05/6/2005 16:50:15
Please also read the reply Jhon gave to RC on that post..
i am gonna copy paste it here for faster response..
I'm gonna try to break this down a little...
If there were no losses or outside forces at all, and you tapped the cone of a woofer in a sealed box, it would spring back and forth until you stopped it. Once you started the woofer in motion, it has kinetic energy (from motion) that is being transferred from kinetic to potential energy over time. The potential energy is in the form of compressed (or decompressed) air in the box, and the suspension of the woofer stretching. Acting like a spring. Eventually, all the kinetic energy is transformed into potential energy, and the cone momentarily stops moving (at our excursion max). Energy in a system is always conserved, it just changes forms. The potential energy at that moment is equal to the kinetic energy in the beginning. Then, the force of the spring causes the cone to travel back the other direction, converting the potential energy back into kinetic energy. By the time the cone reaches the normal "at rest" position (still moving), all of the energy has been converted to kinetic, and there is no potential energy. Momentum carries the cone outward from the box, and the process repeats.
This situation is ridiculous in the real world, because there are other factors, losses, and forces. The mechanical parts in the woofer cause energy to be converted into heat when they move. In operation, the coil moving through the magnetic field ends up resisting motion. Those are the biggest. So, if you tap a real woofer, you'll notice it comes to rest really quickly.
Adding stuffing in a box just adds one more function where energy can be converted into heat instead of kinetic or potential energy. So, your woofer can come to rest ever so slightly quicker than it did before. Typically, the difference is measurable, but not audible in music.
This is different from increasing box size, which effectively changes your spring instead of giving you a cause for energy loss.
John G
---------------------------------------------------------------------------------------------------------------
Hope that wud help a little..
Victor...
MrBrownstone on 05/9/2005 16:01:46
standing waves? They are frequency specific, and with wavelengths in the FEET, not a factor unless the inside of the box is in the FEET .
It's amazing. It's like Bob Dole taking Viagra. enough about small things. You'll see more benefit arguing the finer points of erectile dysfunction as a function of sub box size than you will the difference caused by taking the innards of your pillow and placing them in each compartment of your subwoofer box.
Personally, I'd sleep on the pillow stuffing.
Replies (13)
compvr15s on 05/4/2005 11:29:35
size is not critical, most people just staple it to the inside walls, works the same, can just loosly fill the enclosure.. just double the shheets up and use some short staples, will have no problems doing so, good luck
MrBrownstone on 05/4/2005 15:07:36
You're not going to see much difference if you fiberfill the box. If you are short 0.1 cf, you can use about a pound of that stuff in a 1.1cu ft box...but won't probably notice an audible difference. Most woofers have about a 10% tolerance for box size.
lessismorespl on 05/4/2005 21:26:06
I agree Mr B, never really liked that stuff, kind of like a cap, it takes out your pocket but your ears don't notice the difference. Just a waste of money and time IMHO.
swez on 05/5/2005 09:28:27
Funny how we debate this issue every so often.
Have serviced, built and installed many Pro Audio sub enclosures over the years and every one that I have ever worked on, used acoustical dampening materials.
Even the smaller Sat speakers used in restaurants, stores and retail chains have paging systems and background music, use acoustic damping materials in their MB enclosures. Have install "many" of those of late too.
Wonder why they bother to use it, if it has no purpose or value? What do those designers and fabricators know, that we are missing?
Swez
MrBrownstone on 05/5/2005 11:20:32
Swez
Some of the GREATEST car audio installations use Capacitors. Does that give them value?
Even the guy that proports the use of fiberfill, Tom Nuisaine, printed his article on how much you need vs. the impact on the woofer. Honestly, platinum-tipped RCA cables will have more of an impact.
They put it in there because of what you say, "...they are DESIGNERS.." Nothing more meritous than that. What I was getting at was that 1 POUND would equal 0.1 cuft...so if you are short 0.1 cu ft, use it.
Either way, with a woofer tolerance of 10%, I would challenge anyone to prove it made an audible difference.
Remember, Pro Audio are the people that believed that LPs are better than CDs. You need galvanized Platinum and metal foil shielding and braided materials to isolate your line level signal from the microwave oven in your house!!!! Pro audio is responsible for most of the audio 'jewelry' we have in this industry.
If you woofer box tolerances is 1.0 to 1.25 and you have 0.9--use it. If you are in between 1.0 and 1.25--you'll notice modest differences in Q...just not enough to worry about.
HERE's a long lost post from RC on the issue:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=022663#000003
and here:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=018097#000019
Richard Clark
Moderator
Member # 8
posted May 27, 2004 02:54 PM
--------------------------------------------------------------------------------
close guys but no cigar---------here's the theory and the facts--------in an acoustic suspension system the cone motion is primarily controlled by the air spring behind the cone------this spring is the trapped air in the box and since air is a compressible gas it actually makes a fairly linear spring compared to most mechanical springs-------hence the inherent low distortion of most sealed box designs----------we all should know that when a gas is compressed it heats up------we should also know that when it is rarified (expanded) it cools---------as a speaker compresses the air in a box there is a temperature rise in the gas-------when the speaker moves outward the heat is removed from the gas to the same degree (boyles law tells us that there is a direct relationship between pressure, temperature and volume of a gas)--------this constant rise and falling of temperature occurs whenever thhe speaker moves--------since this system constantly rises and falls in temperature strictly due to gas volume no real energy is lost------when energy is contained in a system and only converted it is considered to be adiabatic---------this is a mechanical pure reactance----ie a perfect spring (no such thing exists but for simplicity we will assume it does)-------remember that if we had a perfect spring and exerted 10 lbs of force to compress it the spring would exert 10 lbs of force back till it was relaxed----------since temp, volume and pressure of a gas are directly related, the spring action controlling the speaker movement is clearly defined----------now if we introduce a way for energy to be removed from the system things change--------if we introduce stuffing we are actually adding resistive losses--------as air moves through the stuffing it suffers resistive losses that produce heat-------unlike the heat that results from compressing air this heat is not recovered when the speaker reverses direction-------this heat is dissipated in the stuffing--------since some of the energy is lost this means that there is less spring power to move against the speaker when it moves---------this means that the speaker "thinks" the box is bigger since the air seems to be a weaker spring----------a system that loses energy permanently to resistive elements is know as an isothermal one-----------now the real issue is not if the theory is correct since it is clearly scientific and beyond question----------i see it as more like the amp sq issue--------we know we can measure differences but can we really hear them???---------it is easy to demonstrate that stuffing a box will lower the resonant frequency a few hertz----------but like the amp issue it is really thin ice to claim to be able to hear it in most cases--------is that a reason not to do it????-------not at all------any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense--------but don't expect miracles..........RC
--------------------
A2000Rich
lessismorespl on 05/5/2005 15:21:50
I have to agree. To me fiberfill has no known purpose, be it audible, or in performance. Going to a ported enclosure would produce more results than fiberfill. As w/ capacitors, they serve no purpose and if you read reviews and articles written on them, the only positive ones are written by people that manufacture or have some affiliation w/ a manufacturer. If you are using a prefab enclosure and one day say, "hey, I think I need to know the volume of the box and see if it is right for my subs" and you discover the enclosures volume is a bit small, why not, but will it make a big difference, no!
Richard Clark is some-one I really look up to in the car audio world. I seen the subwoofer he built using, I believe it was, an ice truck as the enclosure at a couple shows, MTX had backed him somewhat on this, it was amazing. Sorry, got off topic for sec.
Me, personally, I think I would just build a bigger enclosure rather than waste the money on fiberfill, but of course that is me. And don't even get me started on caps, after the testing and research I have done on caps, as well as reading JL's Sound School of Excellence, I'm done w/ caps.
gearhead on 05/5/2005 16:07:58
Well, the manufacturers specs are given for an enclosure with "all sides lined with 1-inch fiberglass or fiberfill". It doesn't give any specs sans fiberfill. I'm not after volume (SPL), this is for a surround sound system, so a ported box isn't what I need/want. I'll just take Mr. Clark's advice "is that a reason not to do it????-------not at all------any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense--------".
swez on 05/5/2005 20:20:05
Well, that sure makes a good case for not using fill if the box is of adequate size.
I have reviewed many sub enclosure specs over the years and many do recommend polyfill for their subs. Why? Reduces standing bass waves inside the box and does add a minute degree of apparent size of the enclosure, as the woofer sees it.
In this case, there are good reasons to use or not use fill materials. Personally, I have used it for years with fine results and will continue to do so if not only for sake of habit and the knowledge that a majority of Pro enclosures do the same. Will it hurt? No... Does it help? In a very minor way according to Leap plots I have looked at over the years.
In short, we all have our preferences and quirks. Mine is to use fill at all times. The cost and time are minimal and the results have not been negative to date. It may not be a notable difference I can detect... but I use it anyway. The choice is pretty much up to the builder of the enclosure. Am satisfied with that. (Whatever)
Swez
MrBrownstone on 05/6/2005 15:07:15
the whole argument for 'reducing' standing waves does not apply to the car audio environment. The box would need to be larger than most trunks to have an impact..and carpet on the floor of the trunk would take care of that.
There just isn't an argument for fiberfill in a car audio system unless you want to please your eyes.
Gearhead, you are misinterpreting Mr. Clark's Post. The unwritten sarcasm is that IF there is scientific proof, use the stuff. There just isn't scientific proof that you'll hear a difference or see any benefit.
Remember, like a red and a green speaker, if you can't hear the difference, is there?
Victor on 05/6/2005 15:31:28
Hmmmm...
With more than a 100 enclosures fabricated, i guess i got something to share here.
Even about capacitors.hehe..
1 - They dont exactly benifit as much as they are hyped.
2 - Not an alternative for a stable electrical system.
About the Fibrefill
1 - Rarely make an audible difference.
2 - It is also much like psycho acoustics, where its just fooling the sub ( lol and your ears if they are like as sensitive as a dog).
3 - I dont see why the issue of standing waves dont apply to Car environment.
4 - Standing waves which are generated by the rear side of the cone and due to the shape of the enclosure affect any enclosed driver.
5 - Unless you got a perfect spherical enclosure there is no way you can eliminate standing waves generated from the back of the speaker.
Using fibre fill is OPTIONAL and not a NECESSITY.
Victor...
gearhead on 05/6/2005 16:19:39
The way I read it is:
#1- "now the real issue is not if the theory is correct since it is clearly scientific and beyond question" & "it is easy to demonstrate that stuffing a box will lower the resonant frequency a few hertz".
#2- "we know we can measure differences but can we really hear them??" & "but like the amp issue it is really thin ice to claim to be able to hear it in most cases".
He's saying it DOES make a difference, you just can't HEAR the difference.
#3- "any real improvement that can be supported by scientific evidence that is as cheap as a few oz of fabric just make a lot of sense". He's saying whether you can hear it or not, since it's supported by scientific evidence (#1), but not necessarily physical evidence(#2), and it's inexpensive to do, it does make sense to do it.
Victor on 05/6/2005 16:50:15
Please also read the reply Jhon gave to RC on that post..
i am gonna copy paste it here for faster response..
I'm gonna try to break this down a little...
If there were no losses or outside forces at all, and you tapped the cone of a woofer in a sealed box, it would spring back and forth until you stopped it. Once you started the woofer in motion, it has kinetic energy (from motion) that is being transferred from kinetic to potential energy over time. The potential energy is in the form of compressed (or decompressed) air in the box, and the suspension of the woofer stretching. Acting like a spring. Eventually, all the kinetic energy is transformed into potential energy, and the cone momentarily stops moving (at our excursion max). Energy in a system is always conserved, it just changes forms. The potential energy at that moment is equal to the kinetic energy in the beginning. Then, the force of the spring causes the cone to travel back the other direction, converting the potential energy back into kinetic energy. By the time the cone reaches the normal "at rest" position (still moving), all of the energy has been converted to kinetic, and there is no potential energy. Momentum carries the cone outward from the box, and the process repeats.
This situation is ridiculous in the real world, because there are other factors, losses, and forces. The mechanical parts in the woofer cause energy to be converted into heat when they move. In operation, the coil moving through the magnetic field ends up resisting motion. Those are the biggest. So, if you tap a real woofer, you'll notice it comes to rest really quickly.
Adding stuffing in a box just adds one more function where energy can be converted into heat instead of kinetic or potential energy. So, your woofer can come to rest ever so slightly quicker than it did before. Typically, the difference is measurable, but not audible in music.
This is different from increasing box size, which effectively changes your spring instead of giving you a cause for energy loss.
John G
---------------------------------------------------------------------------------------------------------------
Hope that wud help a little..
Victor...
MrBrownstone on 05/9/2005 16:01:46
standing waves? They are frequency specific, and with wavelengths in the FEET, not a factor unless the inside of the box is in the FEET .
It's amazing. It's like Bob Dole taking Viagra. enough about small things. You'll see more benefit arguing the finer points of erectile dysfunction as a function of sub box size than you will the difference caused by taking the innards of your pillow and placing them in each compartment of your subwoofer box.
Personally, I'd sleep on the pillow stuffing.
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