In building a 4 cubic foot HT sub using the Ultimax 18, which would be better to reduce cabinet resonances, bracing similar to the kits provided by PE, or mass loading the walls of the cabinet with an additional layer of 3/4" stone like granite or marble?
Ignore the weight differential, as nobody moves their sub often. Yes, both could be done, but would there be any value to bracing & mass loading?
Ignore the weight differential, as nobody moves their sub often. Yes, both could be done, but would there be any value to bracing & mass loading?
Good to see the shape before members pontificate on the answer.
Seems like a pretty small box with short unsupported expanses. So not likely to be any kind of issue (or make the back panel a bit thicker). Better to incorporate the cubic volume inside box instead. The whole matter of cab wall vibrations is much over-blown on this forum with zero evidence of audible detection.
B.
Seems like a pretty small box with short unsupported expanses. So not likely to be any kind of issue (or make the back panel a bit thicker). Better to incorporate the cubic volume inside box instead. The whole matter of cab wall vibrations is much over-blown on this forum with zero evidence of audible detection.
B.
It obviously depends on box panel sizes and amount of power to the speaker.
On small home stuff probably not an issue.
If disco/PA/guitar for gigs then it can become relevant.
On small home stuff probably not an issue.
If disco/PA/guitar for gigs then it can become relevant.
In that case, assuming exterior dimensions, no point on any wall is more than maybe 9 inches from a joint. You think you could make a 9 inch span of MDF (in a reasonable thickness) vibrate audibly like a singing saw?
B.
Not like a singing saw, but I suspect unbraced, walls of 3/4" MDF would flex, and the flexing would intorduce energy into the room.
Yeah gig equipment made of stone may be a gimmick for a "Rock" band, but you wouldn't keep your roadies very long.
Both would be easily doable...3/4 inch MDF layered ( 1.5 inch ) with half-lap joints for the panels. I wouldn't bother with the likes of marble...
Some stretches of 2"X 2" reinforcing, laterally set on the largest panels.
Pay attention to the straightness of the two-by-twos, lots of glue & screws everywhere...the diagonals will have your miter-box saw very busy.
--------------------------------------------------------------Rick................
Some stretches of 2"X 2" reinforcing, laterally set on the largest panels.
Pay attention to the straightness of the two-by-twos, lots of glue & screws everywhere...the diagonals will have your miter-box saw very busy.
--------------------------------------------------------------Rick................
The process of adding a 3/4 inch layer of granite or marble not only adds mass, it adds a lot of stiffness as well. The Young's modulas for these stone materials is at least an order of magnitude higher than wood products. Granite is similar to aluminum, so this 3/4 inch slab of granite is going to be similar in stiffness to 3/4 inch aluminum plate, only much heavier.
So the choice you are contemplating is not "mass vs bracing", it is "stiffness by granite or stiffness by bracing".
I have not done any analysis, but my guess is that a 23 x 21 slab of 3/4 inch granite would need no additional bracing.
So the choice you are contemplating is not "mass vs bracing", it is "stiffness by granite or stiffness by bracing".
I have not done any analysis, but my guess is that a 23 x 21 slab of 3/4 inch granite would need no additional bracing.
A simplified view:
Typically, cabinet wall resonances occur at higher frequencies than the frequency range of a subwoofer. Therefore these resonances themselves do not play an important role.
However, the cabinet walls do still flex below their resonance frequencies, which reduces total sound output of the subwoofer somewhat. Stiffness is important now. Therefore bracing will help, while mass loading will not. Note that this only applies to frequencies below the wall resonance frequencies.
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For subs mass loading does not do much in my experience. WIth this kind of sub, bracing and maybe an extra layer of wood on the outside will do much more. I would not use the same material, as it keeps resonating the same way. If you use an other material, the different resonance frequencies will damp each other more. I would build a plywood box arround it, but granite can also be good, or even solid wood (if it's totally dry so it won't crack).
Mass loading only works higher up in frequency (mid and top), and best on thin wall speaekers.
Mass loading only works higher up in frequency (mid and top), and best on thin wall speaekers.