The simulators do a pretty good job of predicting what's going to happen when you adding lining / stuffing. All four of my preferred simulators can handle stuffing at any density at any point(s) inside the enclosure.
I wouldn't say stuffing / lining a box makes it acoustically larger or smaller, but it will round off the low knee and change box q making it seem that way.
Placing stuffing / lining anywhere near the port will attack the low bass down near tuning so by the time you damp the higher harmonics the low bass takes a big hit. Stuffing on the opposite end of the box and keeping the stuffing well away from the ports will take care of the higher harmonics without harming the low bass too much.
This is all easy to see if you play around a bit with a good simulator. Or you can do trial and error but it takes a lot longer.
I wouldn't say stuffing / lining a box makes it acoustically larger or smaller, but it will round off the low knee and change box q making it seem that way.
Placing stuffing / lining anywhere near the port will attack the low bass down near tuning so by the time you damp the higher harmonics the low bass takes a big hit. Stuffing on the opposite end of the box and keeping the stuffing well away from the ports will take care of the higher harmonics without harming the low bass too much.
This is all easy to see if you play around a bit with a good simulator. Or you can do trial and error but it takes a lot longer.
Thank you for information. Now it is much mpre clear for me.
Can you tell me which simulators you like? Maybe even some of them are free?
It would be cool to have simulator, which can predict lining and stuffing.
Can you tell me which simulators you like? Maybe even some of them are free?
It would be cool to have simulator, which can predict lining and stuffing.
I actually visited the Bozak factory in Norwalk, CT in the late 70s and the way they made the woofers was very cool, essentially fabricating a very light but stiff paper mache type of cone material for good transients. They advocated for larger enclosures. I still have a pair of their 12" woofers and still work 40+ years later.
Yes.
The best bass is from a large stuffed box with no back. That makes it akin to a portable infinite baffle or lossy dipole, two approaches considered the highest fidelity.
The box per se doesn't help the sound. The sound comes from the driver (aided by a bit of DSP). The box is one way to address the rear wave. Excepting resonance traffickers (BR) and impedance matchers (true horns), that's all it does.
B.
The best bass is from a large stuffed box with no back. That makes it akin to a portable infinite baffle or lossy dipole, two approaches considered the highest fidelity.
The box per se doesn't help the sound. The sound comes from the driver (aided by a bit of DSP). The box is one way to address the rear wave. Excepting resonance traffickers (BR) and impedance matchers (true horns), that's all it does.
B.
Have you tried this with an A-B on the same sub? Are there certain sub drivers better for this approach than others (i.e. subs with too high an xmax or too compliant a suspension may not be as good)?
Leave it in the pillow... I've literally used 4$ Wal-mart pillows as fill for a speaker 🙂 Even better if you use your old ones from the bed when you replace 'em.
Wish I had tested in past times. For sure with a stuffed box with lightly covered back, the driver resonance stays low and that pretty much defines the bass... certainly compared to the tiny sealed boxes that now seem in style that raise the basic cut-off way too high for low bass music even if it brings sim users joyful plots of flat FRs.
It works on all drivers same as traditional TLs, so think super short TLs; what changes is its acoustic compliance (stuffing density), so historically was done to 'taste' in the desired app by DIYers or if they bothered with measurements, then to damp its impedance to just one peak or flatten both as much as practical if coupled to a matching impedance amp.
Have looked at a lot of threads about subwoofers and dampening / stuffing here and other chat forums - open baffle, ported and sealed, It seems there hasn't been a lot of comprehensive research or a major study on this whole area to gain more agreement on what is best for certain objectives and situations?
Many suggestions of fixing damping material to the enclosure wall(s). A little thought will show that this placement remains the least effective use of damping/absorptive material, since particle velocity is zero at the boundary wall.
Correct, way too many variables for the relative few that would benefit from it, so the ones that do the research is typically just for their products, though if you dig around in the room acoustics/damping research there's enough info to satisfy most folks since what is a speaker box but a tiny room with maybe a door or attached hallway? 😉
Here're some data on stuffing.
The second plot shows the output change between no stuffing* and lotsa stuffing in the 17-foot path. The third plot show what is coming out the end (earlier I posted you want mostly the lowest notes to make it through the pipe and out into the room). The fourth plot shows the driver impedance change from no- to lotsa-stuffing - sure controls the driver motion, eh.
Solid bass with no tuned artefacts from a 65 year old 15-inch woofer down to 12 Hz seems pretty good.
B.
* other than the quarter-inch plywood outer walls, the inner paths are made of celotex which is a fibrous mash with some sound control - esp if you have some many square feet of it. So even without the stuffing, there is a some amount of absorption.
https://www.diyaudio.com/forums/subwoofers/322418-17-foot-pipe-sub-12-230-hz-5db.html
The second plot shows the output change between no stuffing* and lotsa stuffing in the 17-foot path. The third plot show what is coming out the end (earlier I posted you want mostly the lowest notes to make it through the pipe and out into the room). The fourth plot shows the driver impedance change from no- to lotsa-stuffing - sure controls the driver motion, eh.
Solid bass with no tuned artefacts from a 65 year old 15-inch woofer down to 12 Hz seems pretty good.
B.
* other than the quarter-inch plywood outer walls, the inner paths are made of celotex which is a fibrous mash with some sound control - esp if you have some many square feet of it. So even without the stuffing, there is a some amount of absorption.
https://www.diyaudio.com/forums/subwoofers/322418-17-foot-pipe-sub-12-230-hz-5db.html
Last edited:
Due to the known deterioration over time of foam, I'd never use it.
Rock wool, or polyester is better, and doesn't rot or crumble.
The last thing I want to do is have to clean out old crumbling foam from a speaker.
I used some rubber crumb underlay in my last sub build. I figured the pressure waves to dampen were quite physical, and as such, a bit of fluff wasn't going to work. Though I stuffed in a pillow anyway..
The rubber crumb has a bit of weight to it. It has a chance of dampening cabinet vibrations that foam can't even address.
Kef have an interesting bit of wood glued inside at the moment. It appears to reduce the number of identical speaker wall cross-sections. Where once you might of had a 300mm wide panel of 18mm, they have glued a diamond shape board to the inside. The number of 300mm lengths of 18mm is drastically reduced. There is very little repetition, with almost every cross-section different.
The rubber crumb has a bit of weight to it. It has a chance of dampening cabinet vibrations that foam can't even address.
Kef have an interesting bit of wood glued inside at the moment. It appears to reduce the number of identical speaker wall cross-sections. Where once you might of had a 300mm wide panel of 18mm, they have glued a diamond shape board to the inside. The number of 300mm lengths of 18mm is drastically reduced. There is very little repetition, with almost every cross-section different.