How important is bracing? Over what panel length is it required?
I bought a BIC America F12. The plate amp was shot so I converted it to passive. The longest panel length is 450mm but the cabinet has no bracing.
To my ears it sounds a little woolly . . . but I paid five bucks so maybe it's just crap?
I bought a BIC America F12. The plate amp was shot so I converted it to passive. The longest panel length is 450mm but the cabinet has no bracing.
To my ears it sounds a little woolly . . . but I paid five bucks so maybe it's just crap?
i wouldn't bother bracing it. you would make a bigger difference lining the internal walls with some foam, but i wouldn't do that too. you could also stuff an old pillow in it and plug the port but i wouldn't do it either.
just gift it to somebody who likes it and build something better. that's what i do with my old gear.
don't think there are any rules for bracing. also don't think anybody braces 12" subwoofers.
panel resonances are an issue with higher frequencies.
and if your concern is losing output to non-resonant panel flex at low frequencies you are losing more output to having a box that is too small than by having a box that is too flexible unless it's literally made out of cardboard or is already like 20 cubic feet.
just gift it to somebody who likes it and build something better. that's what i do with my old gear.
don't think there are any rules for bracing. also don't think anybody braces 12" subwoofers.
panel resonances are an issue with higher frequencies.
and if your concern is losing output to non-resonant panel flex at low frequencies you are losing more output to having a box that is too small than by having a box that is too flexible unless it's literally made out of cardboard or is already like 20 cubic feet.
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Bracing is good! Cheap easy effective.
Find sticks that is 1mm longer than the inside distance you are bracing. Put it in and turn it until it gets stuck (maybe slightly misaligned) add some glue s that the stick falls down.
Find sticks that is 1mm longer than the inside distance you are bracing. Put it in and turn it until it gets stuck (maybe slightly misaligned) add some glue s that the stick falls down.
Bracing is absolutely worthwhile. Even something as simple as cross braces as shown in the photo will make an audible difference at higher volumes.
Yeah, don't listen to Dissident Sound. Bracing is highly effective and helpful. It might not be worth salvaging those speakers but bracing is helpful in pretty much every build since it reduces panel vibrations.
do you realize that a typical speaker such as a 15" PA 2-way has its drivers operate outside of pistonic range for most of the frequency range ? do you realize that by going to 3-way this can be dramatically reduced by introducing a third frequency band of pistonic motion ? do you realize that this is rarely done because it is considered not worth it ? your bracing won't achieve even 5% of the improvement by comparison but do it anyway because it will give you a sense of accomplishment even if in blind A/B testing 9 out of 10 people won't hear ANY difference. not in an average 12" subwoofer anyway.
if this was a high-end studio monitor i would say of course. but it's not.
my own subwoofer i built using double wall, extensive bracing and damping and the box came out weighing about 100 pounds, but that was for a $1,300 driver that weighed 80 lbs by itself.
the only reason i am even replying to your post is because you have knowledge in other areas but you're out of your element here.
things can always be improved but it is not always worth it.
in PA stuff bracing is used because they use lightweight materials for the size of the box which makes it resonate like a guitar so bracing is in order. the alternative to use thicker / heavier material is not an option for gear meant to be portable.
studio gear is mainly just built using thick and heavy MDF because it is not meant to be easily transportable. yes they may brace it too but they mainly rely on just mass.
knock on a subwoofer box and note the frequencies you hear. do you hear any subwoofer frequencies ? no ? then it doesn't need more bracing.
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I agree that the panel vibrations in a subwoofer is way above the frequencies of the woofer. But since people can hear differences when speaker cable is resting on chewing gums on the floor... and not only that! They can hear if the chewing gum has a taste of strawberry or lemon.
Lemon giving that chrisp fresh detail in the treble when the strawberry has that colourful sound... you know the drill.
Lemon giving that chrisp fresh detail in the treble when the strawberry has that colourful sound... you know the drill.
😀 yeah on small sub I would put a cross brace just in case, box and panel resonances are likely above pass band.
For a box that goes into midrange you'd likely want to put a lot more. For reference, a mid box I just built has box resonating some around few hundred Hz, middle of it's passband. It looks like it's the whole box mode, the whole thing resonating as one. First panel modes are roughly an octave higher, still in pass band. These are visible in impedance plot, and it's very hard to determine whether they are audible or not. My bracing is with about 15cm spacing, and if I wanted to push the panel resonances octave higher I'd need to drop that to 10cm or so, basically redo the boxes.
It's no joke to push resonances high up. Plywood box. That's why one wants to add damping with the panels or the braces or both, look for KEF LS50 white paper. And make a multiway speaker to separate concerns. If your mid box is 10cm x 10cm x 10cm it doesn't need any bracing 😉 Oh, and do a fun test, knock your box with other hand while use the other to tighten the driver screws and hear the whole thing tune higher just like a quitar. Tried using tight and floppy connection with few different damping between box /screws/driver, but the lowest resonance was still there just at lower frequency the lossier the connection, which is why I think lowest mode of mine was just the whole box resonating all together. Tigthness like this was audible with knock test, but not sure if I heard any difference with music with a quick test.
ps. tip for knock test, short your driver terminals to kill the driver resonance with electrical damping. Now you hear the box with the knock, not the driver. Unhooked the driver/box main resonance is quite loud while knocking.
For a box that goes into midrange you'd likely want to put a lot more. For reference, a mid box I just built has box resonating some around few hundred Hz, middle of it's passband. It looks like it's the whole box mode, the whole thing resonating as one. First panel modes are roughly an octave higher, still in pass band. These are visible in impedance plot, and it's very hard to determine whether they are audible or not. My bracing is with about 15cm spacing, and if I wanted to push the panel resonances octave higher I'd need to drop that to 10cm or so, basically redo the boxes.
It's no joke to push resonances high up. Plywood box. That's why one wants to add damping with the panels or the braces or both, look for KEF LS50 white paper. And make a multiway speaker to separate concerns. If your mid box is 10cm x 10cm x 10cm it doesn't need any bracing 😉 Oh, and do a fun test, knock your box with other hand while use the other to tighten the driver screws and hear the whole thing tune higher just like a quitar. Tried using tight and floppy connection with few different damping between box /screws/driver, but the lowest resonance was still there just at lower frequency the lossier the connection, which is why I think lowest mode of mine was just the whole box resonating all together. Tigthness like this was audible with knock test, but not sure if I heard any difference with music with a quick test.
ps. tip for knock test, short your driver terminals to kill the driver resonance with electrical damping. Now you hear the box with the knock, not the driver. Unhooked the driver/box main resonance is quite loud while knocking.
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if i wanted a dead sounding box for a $10,000+ studio monitor i would laminate a 3/4" sheet of MDF between two sheets of 1/2" Plywood
outer layers would provide the stiffness while the inner layer would provide the mass, the damping and the spacing for proper geometry as in a Truss or I-beam
but be careful - wood products will warp if you add moisture on one side - your sandwich has to be perfectly symmetrical with equal amounts of glue on both sides or it will warp
you will also want to put a lot of weight on it while drying so it stays flat until dry, and only use as much glue as needed to minimize moisture unless you can swing some kind of epoxy or something that won't make the wood expand too much
perhaps if you can laminate several sheets at the same time you could stack them on top of each other and use just one set of weights or clamps for all of them ... but that begs the question of where the moisture will go ... can the wood simply absorb it ... may require some experimentation
want even more damping ? use two layers of 1/2" MDF for a total of 4-layer 2" thick sandwich.
there may be bonding / adhesive products that are specifically designed for damping as well. i know there is one designed as constrained layer between two sheets of drywall used to construct home theaters, but i don't know if it can be used on wood products.
but it shouldn't be necessary as MDF by itself has some damping - just not a lot of stiffness. by laminating plywood on both sides you keep the damping but push the resonances up, and the mass will prevent the cabinet from accepting the energy from the driver and the air in the chamber in the first place. in other words the mass will create an acoustical impedance mismatch that works in your favor.
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