When you add one pound of polyfill per cu. ft to a box, how many cu. in or cu. ft of airspace does it make the sub think it's getting?
A loose stuffing of Polyfill will effectively increase the volume of a closed box by 5 to 10%.
I'll leave you to do the mathematics! 🙂
I'll leave you to do the mathematics! 🙂
You don't want to stuff a ported box. It restricts are movement you need for the port to work. Polyfill comes in sheets, for quilting. Line the walls, not the driver panel, to absorb mid frequencies. I have a pair of Boston Acoustics that have a 10" drone with a 6.5 woofer. Passive radiators work much like a port. The cabinet is about half full of polyfill with nothing in the drones area. If you stuff a ported box try .5 pound per cubic foot and leave lots of room around the port. I think Boston uses a loosely woven block as there is no sign of sagging. I thought they were woofers until I opened them up as there is plenty bass.
Volume increase does not apply to a ported box as it should not be filled with Polyfill.
Reflex enclosures should only be lined with damping material e.g. felt. Check out this link for details:
Cabinet-damping
Reflex enclosures should only be lined with damping material e.g. felt. Check out this link for details:
Cabinet-damping
am building a 2-way box a need 4.670 cu.ft based on the speaker specs (kappa-15LFA ) and WINISD but i could only manage to get 3.5cu.ft .is there any way to increased the internal volume with Polly fill and is yes how much ?
I filled my sealed box for fullrange driver with lightly packed polyfill and it sounded much better but the box is already way bigger than necessary,
Could it better to use mineral wool here for better damping? maybe a mixture?
There is some leftover from treating the listening room.
Could it better to use mineral wool here for better damping? maybe a mixture?
There is some leftover from treating the listening room.
Please for health and environment issues, use real wool. Real wool is better for sound, lungs and kids health, it is a non-petrol and environmental friendly, and wont harm the sound in any ways.
Please reconsider poly , and rock wool. , real wool can be bought untreated for the same purposes.
Please reconsider poly , and rock wool. , real wool can be bought untreated for the same purposes.
The possible dangers of polyfill is concerning, much more concerning is the polyfill inside bedding rather than in a sealed speaker.
It might not be ideal environmentally speaking unless properly recycled (so properly recycle it), but as far as health matters go, I think if polyfill was dangerous somebody might have noticed by now. 😉 And wool needs treating if you don't want the potential for problems with moths. Which is no joke.
That aside, there is no reason at all why you can't add stuffing to a vented box. Standard for many TLs & TL variations. Plenty of regular vented enclosures do it also, it's even an option in many modelling packages. If you over-damp it, then you'll kill output, and very high densities in close proximity to the driver can mass-load the moving components, preventing them moving or resonating as intended, but the key word is 'over'. If you design appropriately, then this is not an issue.
That aside, there is no reason at all why you can't add stuffing to a vented box. Standard for many TLs & TL variations. Plenty of regular vented enclosures do it also, it's even an option in many modelling packages. If you over-damp it, then you'll kill output, and very high densities in close proximity to the driver can mass-load the moving components, preventing them moving or resonating as intended, but the key word is 'over'. If you design appropriately, then this is not an issue.
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Yes, but Trev98 has asked if stuffing his 3.5cu ft box can increase its effective volume to 4.67cu ft.
I said no - what is your opinion Scott?
My opinion is worthless; I have some hard data on my home machine (in the office at present) which is of rather more relevance. Not that it matters, I would say that is pushing it somewhat; the most sensible approach however would be to use modelling software of known reliability to check the alignments, which will render the question a non-issue either way. WinISD is mentioned, and is quite capable of doing that.
Perhaps more usefully, I have to wonder where the 4.67ft^3 stipulation comes from. That sounds like simply following a specific mathematical alignment which usually isn't particularly good practice. There's nothing wrong with that driver in 3.5ft^3 tuned to, say, 36Hz which will give quite a usable, lightly damped alignment with an anechoic F6 = Fb or thereabouts. In practice, vis-à-vis the larger box, gives up about 4Hz worth of LF extension and a touch less gain for a similar[ish] alignment. In the circumstances, I wouldn't get in a lather over that myself.
Perhaps more usefully, I have to wonder where the 4.67ft^3 stipulation comes from. That sounds like simply following a specific mathematical alignment which usually isn't particularly good practice. There's nothing wrong with that driver in 3.5ft^3 tuned to, say, 36Hz which will give quite a usable, lightly damped alignment with an anechoic F6 = Fb or thereabouts. In practice, vis-à-vis the larger box, gives up about 4Hz worth of LF extension and a touch less gain for a similar[ish] alignment. In the circumstances, I wouldn't get in a lather over that myself.
Thanks Scott, your cabinet design expertise is of more relevance to solving Trev98's problem than his suggested use of polyfill!
There are some who might disagree with that. 😉
FWIW: http://web.archive.org/web/20120620065121/http://www.nousaine.com/pdfs/Box Stuffing.pdf Not lengthy but the methodology and equipment were plenty adequate. Be that as it may, I'd set my sights a little lower as I don't care for high packing densities for other reasons -the 3.5ft^3 with a mid 30s tuning and conventional lagging or light stuffing should be pretty decent though.
FWIW: http://web.archive.org/web/20120620065121/http://www.nousaine.com/pdfs/Box Stuffing.pdf Not lengthy but the methodology and equipment were plenty adequate. Be that as it may, I'd set my sights a little lower as I don't care for high packing densities for other reasons -the 3.5ft^3 with a mid 30s tuning and conventional lagging or light stuffing should be pretty decent though.
That's an interesting article on making a small sub box appear larger by using polyester fiberfill, Scott!
It's worth quoting the 'rules of thumb' that were stated in the conclusion to the article:
It's worth quoting the 'rules of thumb' that were stated in the conclusion to the article:
It should be noted that quantitative measurements were made using only one size of ported enclosure (1.4cu ft), and that's why the results can only be translated into 'rules of thumb'.
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