Is one really better than the other for packing cabinets? And If I go with polyfill how much will I need for two Large Advents?
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Polyfill or fiberglass insulation?
- Thread starter tonedeaf57
- Start date
30hz MAGIC
Creator of earthquakes!
I heard in multiple places and from multiple people that fiberglass is better and adds more volume.
But polyfill(which i use personally)is more practical and can even be used with ported enclosures.
But polyfill(which i use personally)is more practical and can even be used with ported enclosures.
Thanks for the replies. Kinda leaning toward the 'glass since that's what was in the boxes. It is nasty but the stuff that was in there looks as 'fresh' as it probably was almost 45 years ago, and I have it on hand. Just didn't know if the polly was a sonic improvement.
Bob Orme
Active Member
You need to consider what it does. The most simple (and non-technical) way to explain the purpose in most applications is, fiberglass slows down the speed of sound. It kind of tricks a woofer into acting like it is in a larger enclosure. I could be wrong, but I don't think polyfill is as effective.
keilau
AK Member
The better speaker cabinet stuffing material
The question was answered a long time ago. See the blog by Ken Kantor on this subject. The blog is somewhat technical. If you spend the time to digest it, it is easy to follow.
http://auralization.blogspot.com/?zx=a7750b35f5725eac
Fiberglass:
Fiberglass was the first material to achieve widespread commercial usage as a “stuffing” material for loudspeakers, specifically intended to increase the effective volume of a sealed enclosure. Already widely used to line the inside walls of speaker cabinets thanks to its excellent sound absorption and insulation properties, fiberglass was now distributed throughout the inside of sealed woofers to lower system resonance and improve bass response. This innovation is generally attributed to Villchur for use in his “Acoustic Research” products. The reduction of internal reflections and “standing waves” at higher frequencies was also present, and was considered an important collateral benefit.
Villchur tended to explain, (rather casually), that the fiberglass acts on Fc primarily through its thermal mass, continuously exhanging heat and pressure in the system, and thus altering the acoustics of the sealed box from “adiabatic to isothermal.” For example, an inward motion of the woofer, which decreases the size of the sealed cavity, results in a slighly lower than expected pressure. In effect, the box looks bigger that it is. Alternatively, but equivalently, he described the effect as a lowering of the speed of sound in the box.
It is easy to measure the empirical results of adding fiberglass to a sealed box. Fc is noticably reduced, and there is a downward effect on Qtc. It has long been a matter of debate as to what extent there are bona fide thermodynamic, cyclic heat exchange processes occuring in the box, as opposed to purely viscous damping of the air, flow resistance and tortuosity effects. It has been shown repeatedly and convincingly that the introduction of simple resistive damping to a closed box system will result in superficially similar effects on both Fc and Qtc. However, experimental evidence (here and elsewhere), suggests that fiberglass shows behavior that goes at least somewhat beyond pure resistive damping.
Synthetic Polymer Fibers:
Fiberglass is not an easy material to work with in a manufacturing environment. It requires the use of respirators and gloves, at a minimum, and is irritating to operators. The need to “fluff” the fiberglass from its sheet form into a shape appropriate for speaker filling exacerbates the problem. This has led loudspeaker manufacturers to seek alternatives of similar effectiveness, but with friendlier material properties. Dacron®, Hollofil® and similar polyester fibers in wad form have emerged as the leading candidates, and are now widely used.
It is important not to consider all types of synthetic fiber fill to be equivalently effective. There is a wide range of material available, from readily available types intended for making pillows, to hollow core fibers used for thermal insulation, to fibers of triadic cross-section specifically designed for audio use. Generally, the best of these have excellent midrange damping properties, but still fall somewhat short of fiberglass in their ability to lower Fc. This has not proven fatal to their commercial use, but it does present a problem for manufacturers attempting to implement a running change to an established design, and to hobbyists and repair shops engaged in restoration activities. It also demands of the engineer the ability to undertand and specify material properties in a domain that is often unfamiliar and poorly understood. This leads to sub-optimal “stuffing” in both professional and amateur loudspeaker designs.
The question was answered a long time ago. See the blog by Ken Kantor on this subject. The blog is somewhat technical. If you spend the time to digest it, it is easy to follow.
http://auralization.blogspot.com/?zx=a7750b35f5725eac
Fiberglass:
Fiberglass was the first material to achieve widespread commercial usage as a “stuffing” material for loudspeakers, specifically intended to increase the effective volume of a sealed enclosure. Already widely used to line the inside walls of speaker cabinets thanks to its excellent sound absorption and insulation properties, fiberglass was now distributed throughout the inside of sealed woofers to lower system resonance and improve bass response. This innovation is generally attributed to Villchur for use in his “Acoustic Research” products. The reduction of internal reflections and “standing waves” at higher frequencies was also present, and was considered an important collateral benefit.
Villchur tended to explain, (rather casually), that the fiberglass acts on Fc primarily through its thermal mass, continuously exhanging heat and pressure in the system, and thus altering the acoustics of the sealed box from “adiabatic to isothermal.” For example, an inward motion of the woofer, which decreases the size of the sealed cavity, results in a slighly lower than expected pressure. In effect, the box looks bigger that it is. Alternatively, but equivalently, he described the effect as a lowering of the speed of sound in the box.
It is easy to measure the empirical results of adding fiberglass to a sealed box. Fc is noticably reduced, and there is a downward effect on Qtc. It has long been a matter of debate as to what extent there are bona fide thermodynamic, cyclic heat exchange processes occuring in the box, as opposed to purely viscous damping of the air, flow resistance and tortuosity effects. It has been shown repeatedly and convincingly that the introduction of simple resistive damping to a closed box system will result in superficially similar effects on both Fc and Qtc. However, experimental evidence (here and elsewhere), suggests that fiberglass shows behavior that goes at least somewhat beyond pure resistive damping.
Synthetic Polymer Fibers:
Fiberglass is not an easy material to work with in a manufacturing environment. It requires the use of respirators and gloves, at a minimum, and is irritating to operators. The need to “fluff” the fiberglass from its sheet form into a shape appropriate for speaker filling exacerbates the problem. This has led loudspeaker manufacturers to seek alternatives of similar effectiveness, but with friendlier material properties. Dacron®, Hollofil® and similar polyester fibers in wad form have emerged as the leading candidates, and are now widely used.
It is important not to consider all types of synthetic fiber fill to be equivalently effective. There is a wide range of material available, from readily available types intended for making pillows, to hollow core fibers used for thermal insulation, to fibers of triadic cross-section specifically designed for audio use. Generally, the best of these have excellent midrange damping properties, but still fall somewhat short of fiberglass in their ability to lower Fc. This has not proven fatal to their commercial use, but it does present a problem for manufacturers attempting to implement a running change to an established design, and to hobbyists and repair shops engaged in restoration activities. It also demands of the engineer the ability to undertand and specify material properties in a domain that is often unfamiliar and poorly understood. This leads to sub-optimal “stuffing” in both professional and amateur loudspeaker designs.
Rex Aeterna
Gigolo of Gigolos
Fiberglass is a better absorber obviously but I use both usually.
I use thick as possible fiberglass (around 9" thick) to usually line bottom, top, back, and sides and stuff the rest with good quality polyfill. Some people say it'll make speakers lifeless or whatever but in my experience it usually improves the speakers overall sound and performance. It will lower sensitivity a bit depending how much is stuffed of course but im not too worried about stuff like that since I got the amp to push about any speaker to high levels easily.
Just when stuffing, always leave decent amount room behind woofer for it to have room for excursion. Well, that's how I do it and always had good results. I would experiment I guess depending what you want.
I use thick as possible fiberglass (around 9" thick) to usually line bottom, top, back, and sides and stuff the rest with good quality polyfill. Some people say it'll make speakers lifeless or whatever but in my experience it usually improves the speakers overall sound and performance. It will lower sensitivity a bit depending how much is stuffed of course but im not too worried about stuff like that since I got the amp to push about any speaker to high levels easily.
Just when stuffing, always leave decent amount room behind woofer for it to have room for excursion. Well, that's how I do it and always had good results. I would experiment I guess depending what you want.
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Naptown Rob
Ponographer
Fiberglass.
As long as you wear gloves & avoid dancing the Fandango while rubbing it on your face, it's really not horrible to work with at all when you're just talking about two speakers. In fact, I often don't even bother with gloves, RINSE hands with COLD water when done.
Now, back when I worked on the assembly line at Bose, stuffing it in cabinets 8 hours a day, THAT sucked. Bad enough to make me go to college.:yes:
As long as you wear gloves & avoid dancing the Fandango while rubbing it on your face, it's really not horrible to work with at all when you're just talking about two speakers. In fact, I often don't even bother with gloves, RINSE hands with COLD water when done.
Now, back when I worked on the assembly line at Bose, stuffing it in cabinets 8 hours a day, THAT sucked. Bad enough to make me go to college.:yes:
Rex Aeterna
Gigolo of Gigolos
Same. I usually never use gloves or anything. Fiberglass though never makes me itch either like other people.
Fiberglass is always my number one choice for speakers and room acoustics. It's safe to work with unless like you said "dancing around with it"
Fiberglass is not air bourne unless moved around a lot. Stationary its safe and it being in a speaker enclosure it's not going anywhere.
drbiggles
I like to pull weeds.
Hey,
As others have stated, fiberglass. And it's not that big of a deal. Just don't strip down naked and roll around in it with arms and legs flailing. I went over board with my jump suit, mask and latex gloves. But I'm itchy to begin with, didn't need any help.
ADC-18's getting stuffed!
Biggles
As others have stated, fiberglass. And it's not that big of a deal. Just don't strip down naked and roll around in it with arms and legs flailing. I went over board with my jump suit, mask and latex gloves. But I'm itchy to begin with, didn't need any help.
ADC-18's getting stuffed!
Biggles
Naptown Rob
Ponographer
Harder to work with & messier, in my experience. Fiberglass is actually quite tidy...
Adda
Super Member
I donno, in my experience, fiberglass leaves a lot of dust behind, while rockwool leaves woolly balls in stead.
At any rate, rockwool provides better dampening then any other type of wool.
Rex Aeterna
Gigolo of Gigolos
Good stuff but for the price I usually see it, not worth it. I can get 9" thick r-30 fiberglass 25ft roll for 13 bucks that has better coeffiency then rock wool safe n sound that is 50 something. I can see it being used for specific applications but for speakers way too expensive.
