I defer the the experts on this site: damping in a subwoofer cabinet is pointless. L/F frequency wavelengths are far too long for the damping material to have any affect, right?
Can somebody explain why almost every manufacturer of small subwoofers stuff their cabinets?
I'm sure I've disassembled more subwoofer cabinets than most and have amassed enough damping material to supply Mike Lindell.
Can somebody explain why almost every manufacturer of small subwoofers stuff their cabinets?
I'm sure I've disassembled more subwoofer cabinets than most and have amassed enough damping material to supply Mike Lindell.
Stuffing the enclosure lowers the system Q (Qtc) to reduce the boominess of the bass reproduction.
As a hypothetical example, Qtc could be reduced from 1.0 to a better controlled 0.7.
As a hypothetical example, Qtc could be reduced from 1.0 to a better controlled 0.7.
Further, speaker cones can be almost acoustically transparent at some frequencies, and the damping helps absorb anything which gets through.
Damping materials represent a miniscule cost in getting that one step closer to perfection!
Damping materials represent a miniscule cost in getting that one step closer to perfection!
Actually, it is science. Thermodynamics. To way oversimplify, the pressure waves in the trapped gas (air) causes the stuffing fibres to move, therefore generating heat. Thus, a net energy loss in the ("enclosed") system. This has the desired effect to make the enclosure "look" larger to the transducer. In theory one could stuff the enclosure so much as to tip the process from isothermal to adiabatic, but I don't think you can really get that much stuffing in the enclosure or have a totally "enclosed" system (there will always be heat transferred out of the system by the enclosure, transducer, etc.).
So, the manufacture can make a smaller enclosure. More market, budget, and shipping friendly. A win, win, as it were.
Dan
So, the manufacture can make a smaller enclosure. More market, budget, and shipping friendly. A win, win, as it were.
Dan
Even though low-frequency wavelengths are long, there are still internal reflections within the cabinet. These reflections can cause standing waves or resonance. The damping material helps absorb some of these internal reflections.
Standing waves that may potentially build up in a small sub would be higher in frequency than the range of frequencies being reproduced by the sub.
The higher frequencies (say above 100 Hz) will be attenuated by 10s of decibels by the sub's electronics so such resonances are of no concern.
If we were talking about a full-range speaker, the addition of the stuffing would make a noticeable difference in what we hear coming through the cone at the mid and high frequencies.
The higher frequencies (say above 100 Hz) will be attenuated by 10s of decibels by the sub's electronics so such resonances are of no concern.
If we were talking about a full-range speaker, the addition of the stuffing would make a noticeable difference in what we hear coming through the cone at the mid and high frequencies.
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Relevant to this discussion: measurements of different levels of ported box stuffing.
https://sound-au.com/articles/boxstuff.htm
https://sound-au.com/articles/boxstuff.htm
That article references results from the boxnotes software. I used it several years ago and as I recall it had an error in the acoustic mode frequency calculation. I was able to get correct acoustic mode frequencies using the also free Hornresp software. The boxnotes software may have been corrected by now, but I didn't want to download it from that sort of dodgy looking website offering pdf viewers and such.
In that case, remember to use rockwool or fibreglass! j/k
That's often false. A typical 24dB per octave filter set to 80Hz can be considered OK but could let through noticeable amounts of muffled speech and other sounds 2 or 3 octaves out.
All the diy'ers knows that adding stuffing to a sealed box lowers it's Q . They also know that adding some stuffing to a ported enclosure absorbs any higher frequencies to stop them from coming out of the port / exciting port resonances. So if all the manufacturers add stuffing to their boxes maybe they know the same thing.
Edit. Manufacturers would not waste money putting stuffing in for no reason. They would measure and reduce the stuffing to the bare minimum required
This makes no sense to me. In the case of PORTED SUBWOOFERS there are no higher frequencies to absorb.
There is also inconsistency between manufacturers. My Celestion is generously stuffed, the B&W not so much, the Yamaha - none.
There is a misconception that a ported box is different to closed. Apart from the port, they both suffer from modes. If it's desirable to stuff a typical closed box then it's unfortunate if you don't do the same for ported.. The reason it's sometimes not done is based on not wanting to lose that bass efficiency gained by adding the port.
Excuse me to interfere, but there are two major differences. The first is, the port reduces the excursion extremely on the port tuning. At the same time, a ventilated enclosure does not restirct the excursion below the fb, which means, the drivers cone practically runs without any resistance! That means, a vented enclosure needs a low-cut/subsonic mandatory! If you don't do that, the VC will meet the back pole plate and will be damaged!
A sealed enclosure doesn't need it (mandatory) but still profits from a low-cut since it extends the nax spl. Of course you don't get 'free lunch' in speaker physics, that limits the low end extension.
That means, on both sealed or vented you have to apply filters and low end extension in exchange for maxspl.
That's a wrong view of the problem. If you have problems with room modes, the best way to deal with it is installing a DBA. If you don't want the best solution to room modes, try a room mode simulator (sry, don't have a link at hand and I'm way too drunk to search for one)
Really just as simple as that.
And in real world, you just add fill , then hear the differences.
Other than that going off the concept.
most the small home commercial type subs I have been inside
Had no fill or absorption material.
The old saying was fill made the box " appear" bigger.
Id expect the whole wanting the smallest box possible
crowd. Would be all about stuffing them full.
And swear it magically sounded "bigger".
Agree sealed or ported, they are still boxes.
plenty of my computer speakers over the years
cross over high 150 Hz with simple filters.
So could line the box and improve the sound.
Something boosted crossed at 60 Hz.
Sure why fill, reality probably fixes
poor alignments a slight bit
And in real world, you just add fill , then hear the differences.
Other than that going off the concept.
most the small home commercial type subs I have been inside
Had no fill or absorption material.
The old saying was fill made the box " appear" bigger.
Id expect the whole wanting the smallest box possible
crowd. Would be all about stuffing them full.
And swear it magically sounded "bigger".
Agree sealed or ported, they are still boxes.
plenty of my computer speakers over the years
cross over high 150 Hz with simple filters.
So could line the box and improve the sound.
Something boosted crossed at 60 Hz.
Sure why fill, reality probably fixes
poor alignments a slight bit
The rear of a chassis doesn't operate totally noiseless, you can often hear sound higher in frequency than the generator feeds, if you listen to the back. Even the cabinet may produce noise under high load. A picky consumer may complain and return a product even for hardly audible anomalities.
I think there are various possible positive effects from using some damping inside a sub, so it makes sense for the manufacturer to invest a few extra Cent. It may not be possible to reduce it to the one, single important cause. I know of quite some experts that fold a piece of Rockwool inside a sub, just "for peace of mind, it can't hurt" if you ask why.
I think there are various possible positive effects from using some damping inside a sub, so it makes sense for the manufacturer to invest a few extra Cent. It may not be possible to reduce it to the one, single important cause. I know of quite some experts that fold a piece of Rockwool inside a sub, just "for peace of mind, it can't hurt" if you ask why.