I'm referring to sealed box stuffing material here.
Would some stuffing materials possibly work better at damping/absorbing
lower frequency backwaves (such as could be used in a subwoofer box),
and maybe other materials might be better at damping higher frequencies,
if you had the tweeters in their own sub-enclosure ?
I'm afraid I'm not very knowledgeable on this, but it seems as though
the frequency of the wave being absorbed would make a difference,
and also the amplitude.
If you had a bunch of big logs in the water, they would calm down
a big wake from a passing boat. But, if all you had in the water was
small surface disturbances, like maybe a bit of hail, then smaller
branches would certainly absorb those wavefronts.
Am I worrying for no reason ??
Would some stuffing materials possibly work better at damping/absorbing
lower frequency backwaves (such as could be used in a subwoofer box),
and maybe other materials might be better at damping higher frequencies,
if you had the tweeters in their own sub-enclosure ?
I'm afraid I'm not very knowledgeable on this, but it seems as though
the frequency of the wave being absorbed would make a difference,
and also the amplitude.
If you had a bunch of big logs in the water, they would calm down
a big wake from a passing boat. But, if all you had in the water was
small surface disturbances, like maybe a bit of hail, then smaller
branches would certainly absorb those wavefronts.
Am I worrying for no reason ??
Hi noslepums,
There are differences in which frequencies are absorbed in different types of materials usually used for wadding in loudspeakers.
The white wadding 'poly' stuff u can find in pillows too is good enough to stop reflections from the cabinets rear wall back through the woofer cone which can distort the woofer, yet lambs wool is better. The foam type of wadding is only good for high frequencies in my opinion and the denser carpet underlay type wadding is great for low frequencies when placed on internal cabinet walls except baffle, although denser carpet underlay can absorb a lot of energy.
In sealed cabinets, like yours, wadding is needed more than bass reflex type loudspeakers in my opinion I'd fill it 90% with lambs wool or poly wadding keeping it away from woofer basket, and give it a listen.
There are differences in which frequencies are absorbed in different types of materials usually used for wadding in loudspeakers.
The white wadding 'poly' stuff u can find in pillows too is good enough to stop reflections from the cabinets rear wall back through the woofer cone which can distort the woofer, yet lambs wool is better. The foam type of wadding is only good for high frequencies in my opinion and the denser carpet underlay type wadding is great for low frequencies when placed on internal cabinet walls except baffle, although denser carpet underlay can absorb a lot of energy.
In sealed cabinets, like yours, wadding is needed more than bass reflex type loudspeakers in my opinion I'd fill it 90% with lambs wool or poly wadding keeping it away from woofer basket, and give it a listen.
The best stuffing material for acoustic suspension speakers is fiberglass. When stuffed at the right density, FG optimizes box Q, with lowest Fc and an added benefit of taming the woofer's resonant frequency impedance spike.
Study after study has proven this.
Some DIY'rs are wary of FG because of safety concerns. However, it's contained in a closed box so you needed worry.
As far a reflections go, the FG will take care of that as well. Most tweeters are closed back by design and thus don't require stuffing. Mid ranges in their own little enclosures can be stuffed with FG or good crimped PET fibers.
Study after study has proven this.
Some DIY'rs are wary of FG because of safety concerns. However, it's contained in a closed box so you needed worry.
As far a reflections go, the FG will take care of that as well. Most tweeters are closed back by design and thus don't require stuffing. Mid ranges in their own little enclosures can be stuffed with FG or good crimped PET fibers.
Yes to the above and add reticulated foam 20-30ppi, rockwool and bonded logic ultra touch.
Lately have been experimenting with microfiber towels. They work well too 🙂
Lately have been experimenting with microfiber towels. They work well too 🙂
I agree with this: Fiberglass and Rockwool are the best I have used or seen measurements on.
As to the frequency response of absorbers, for the most part everything absorbs at the highest frequencies and the better materials work lower down in frequency. Most materials absorb frequencies in proportion to their thickness, i.e. a deeper amount is always required for low frequencies.
I've never found fiberfill, BAF wadding or other pillow stuffing type materials to be very good.
David
Of course as speakerdoctor says, fiberglass is better, my friend has a vintage pair of sealed speakers with FG inside.
I tend not to use it because of skin allergy's, but that's me, millions don't have a problem, so use it if u can.
I'd be interested to hear Mundorf's Angel Hair, any suggestions?
Mundorf Twaron Angel Hair Wadding Hifi Collective
Greebster interesting combo, I've just built some bookshelfs with a bitumen, dense underlay and lambs wool combo, works great for what I wanted to achieve.
Of course the bitumen layer is for preventing panels resonant, which is a different subject altogether.
How are you finding the microfiber towels tests?
I tend not to use it because of skin allergy's, but that's me, millions don't have a problem, so use it if u can.
I'd be interested to hear Mundorf's Angel Hair, any suggestions?
Mundorf Twaron Angel Hair Wadding Hifi Collective
Greebster interesting combo, I've just built some bookshelfs with a bitumen, dense underlay and lambs wool combo, works great for what I wanted to achieve.
Of course the bitumen layer is for preventing panels resonant, which is a different subject altogether.
How are you finding the microfiber towels tests?
I've done many box stuffing experiments over the years. A few years back, I thought I was onto something. Some of you may be aware of KEF's Activated Carbon stuffing material. That material has millions of small cavities to trap acoustic waves.
So, I was in the local craft store and came across some foam blocks that are green and highly porous for sticking live plant stems into so they keep moist. Those blocks also had zillions of small pores. So, I cut a couple up and stuffed an AR4x with it. I thought the absorbtion action of the green blocks would be similar to the AC. However, the exp. was a total failure.
If you decide to give that idea a try, be sure to get the porous blocks. They sell non-porous ones as well that look exactly the same. Those are for sticking artificial flower stems into.
Keep us posted greebster on you stuffing journey!
So, I was in the local craft store and came across some foam blocks that are green and highly porous for sticking live plant stems into so they keep moist. Those blocks also had zillions of small pores. So, I cut a couple up and stuffed an AR4x with it. I thought the absorbtion action of the green blocks would be similar to the AC. However, the exp. was a total failure.
If you decide to give that idea a try, be sure to get the porous blocks. They sell non-porous ones as well that look exactly the same. Those are for sticking artificial flower stems into.
Keep us posted greebster on you stuffing journey!
BR is no different than sealed in regard to stuffing amount.
It just needs to be placed around so the port works as intended.
Measurements will show how well stuffing works.
IIRC there have been a limited number od studies (maybe just 1) that ranks UltraTouch cotton wall insulation a bit better. It does cost more but is way nicer to work with.
dave
in (at least older versions of) the Loudspeaker Design Cookbook, Vance Dickason posts measurements of a variety of materials. Trouble is, he doesn't give speaker parameters or box size so you can't do any playing around to model the different materials. He does give Q changes so you can tell which are most effective at resonance. Trouble is, if you get the stuffing too near the driver you can affect Q and Fs by changing mass or restricting flow through the basket, so his measurements aren't all that useful...
Not sure how 'old' is older, but my 6th edition spells out (pg. 36) the test enclusure VD used was 0.95 cu. ft. He called it a 'standard rectangular test enclosure'. Suspect a monkey coffin type.
Yes, I have. Many trials with an assortment of stuffing materials from cotton batting, different types of wools, FG, MBPP, PET, etc..
The trials were done with an AR4x speaker. The reason I chose it was because of it's small size meant I didn't have to buy too much of any one stuffing material and secondly, I wanted to see if such a small speaker's bass output could significantly be enhance via some 'magic' stuffing material - I have yet to find BTW.
Haven't found a magic bullet. I do like microfiber towels draped and held in place by velcro as this allows greater flow. This helped dampen the thin line (~145cm^2) thats 74" long in my mltl. All others caused audible shifting of the material in my not so common design.
Bjorno has done some testing of various materials professionally and posted some results/suggestions of his testing. Even tho, after teasing out the ikea pillow fiberfill (very tedious), measuring weight/volume, still caused audible shifting.
May try a combo of microfiber and vermiculite. Towel wrapped into a cylinder and filled should show some promise of further improvement.
Bjorno has done some testing of various materials professionally and posted some results/suggestions of his testing. Even tho, after teasing out the ikea pillow fiberfill (very tedious), measuring weight/volume, still caused audible shifting.
May try a combo of microfiber and vermiculite. Towel wrapped into a cylinder and filled should show some promise of further improvement.
Recycled bluejeans.
Does look like nice stuff😀
0.95 absorption at 125Hz at 3.5 inch thick.
David
Ultratouch has been getting lots of favorable reviews by DIY'rs. It's basically recycled cotton blue jeans material if I'm not mistaken. Cotton fibers are not very fine. My work has indicated that fiber finess is a key variable in successful A.S. stuffing. Hence, the typical 5 uM diameter of fiberglass fiber's favorable test results. Cottn fibers OTOH, range in diameter from 15-20 uM. Similar to a finer class of PET fibers.
Actually the best stuffing material for any loudspeaker is bubble wrap, as has been used by Sonus Faber and Goldmund for years. It sounds the best to my ears and I have seen real measurements live with my very own eyes. The ranking is as follows:
1.) Bubble wrap
2.) Rock wool
3.) Rigid fiberglass
4.) Fluffy fiberglass
And completely ineffective in just about every way:
Self adhesive grey foam
Fiberfill
Acoustastuf
1.) Bubble wrap
2.) Rock wool
3.) Rigid fiberglass
4.) Fluffy fiberglass
And completely ineffective in just about every way:
Self adhesive grey foam
Fiberfill
Acoustastuf
Last edited:
By what parameters do you determine what is favorable, because the Ultratouch has been measured to have a least as good an absorption as FG, with, if I recall, a flatter absorption vs. frequency overall; or at least as good.
- Status
- Not open for further replies.