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If you want to build a serious sub of such size, this is not even a fraction of the needed bracing.
X-max limited to about 80 watts.
For a back yard party I think we'll be fine with 110 dB from this, and add another 3 to 6dB if I add the others in.
Any more and the police would be here in less than 5 minutes
It's not a serious sub really but please tell me how much extra bracing I'd need for more power.
I'm happy to spend a bit more on small timber to add in a few more cross braces
For a back yard party I think we'll be fine with 110 dB from this, and add another 3 to 6dB if I add the others in.
Any more and the police would be here in less than 5 minutes
It's not a serious sub really but please tell me how much extra bracing I'd need for more power.
I'm happy to spend a bit more on small timber to add in a few more cross braces
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Horizontally at a golden or acoustic ratio.
With vent at the extreme bottom, max cab gain/strongest 'room' modes is with the driver at the top, so may want to compromise at ideally from the (internal) top (L) down to woofer center = L*0.349.
Well guess where I put that first baffle cross brace.
And because I used Titebond3 it isn't being moved; I'll have to put the driver up top.
Going back to the hardware for more bracing materials, at least three more in each direction, then I'll cut some more scraps of MDF for a bit more damping.
And because I used Titebond3 it isn't being moved; I'll have to put the driver up top.
Going back to the hardware for more bracing materials, at least three more in each direction, then I'll cut some more scraps of MDF for a bit more damping.
What about 0.424 (nominally 2/5ths), the one I mostly used till folks started 'expecting' MJK's 0.349.
Re bracing: You want to tie all six sides together to keep it from theoretically 'breathing' and otherwise use boards on edge, not flat, unless you want the added weight. The 'tie' point is a good place to also mass load the driver like I've seen on some detailed Dave p10 drawings.
Break down if 3 meters as qw pipe ? All this is is a very interesting trigonometric function that incorporates the golden ratio and you can see that in the numbers of A squared plus B squared equals C squared as :
864(x sq root 3) plus 864 equals 864(x2)
(I wish I knew wtf I was talking about and had a more appropriate background in mathematics…. Never the less, a 1meter pendulum swings exactly 30° in exactly 1 second catch and release, connecting the dots here to frequency, and the meter and the second and 864
864(x sq root 3) plus 864 equals 864(x2)
(I wish I knew wtf I was talking about and had a more appropriate background in mathematics…. Never the less, a 1meter pendulum swings exactly 30° in exactly 1 second catch and release, connecting the dots here to frequency, and the meter and the second and 864
Attachments
GM because the whole project is an experiment I might just see what happens to the sound if I mount the woofer right at the top.
The baffle will be bolted on, not glued. so I can change things if I need to later on.
I could then always turn the baffle 180 and the woofer would then be right at the bottom.
I will probably never again make a box this big tho. I'm right at my physical strength limits now trying to manipulate this monster.
Any larger and heavier I think I'd be needing a block and tackle and I still have to do the outer MDF damping layer.
The baffle will be bolted on, not glued. so I can change things if I need to later on.
I could then always turn the baffle 180 and the woofer would then be right at the bottom.
I will probably never again make a box this big tho. I'm right at my physical strength limits now trying to manipulate this monster.
Any larger and heavier I think I'd be needing a block and tackle and I still have to do the outer MDF damping layer.
Sometimes you can have small wins that brighten up your day.
I'd put the pine battens and the quick fix glue in my trolley and was walking to the registers when I saw a stack of 12*25 hardwood in really short lengths and I asked if they were sales discounted, the feller from timber said "No, they're offcuts; yours if you want them"
Small win, but I still wound up paying $50- for glue and stuff
I'd put the pine battens and the quick fix glue in my trolley and was walking to the registers when I saw a stack of 12*25 hardwood in really short lengths and I asked if they were sales discounted, the feller from timber said "No, they're offcuts; yours if you want them"
Small win, but I still wound up paying $50- for glue and stuff
In my case, finding them empirically by tapping metal pipe TLs with my then 'blushing' bride telling me which points were sharpest and split the difference as % octave spreads for the nulls.
0.349 is actually MJK's whereas mine cascades? on an octave basis, though in using some of my designs that I still had enough dims of, his original MathCad WSs simmed audibly perfect to my offsets, convincing me his was the 'real deal' and should be protected since the formulas were included, which he initially ignored and later noted that the most DLs were from Just Big & Loud IIRC.
OK
Another $50- and more bracing. The cost of wood and glue at the moment is crazy.
The shelf brace might need some extra because it's only 12mm and being a scrap it doens't go all the way to the front so I can see another $20- being spent tomorrow
Another $50- and more bracing. The cost of wood and glue at the moment is crazy.
The shelf brace might need some extra because it's only 12mm and being a scrap it doens't go all the way to the front so I can see another $20- being spent tomorrow
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Any better Turbowatch??
Each extra brace costs ~$13- and money is tight leading up to XMas
Looks like a start.
Take a piece of wood, a small hammer or your fingers and knock on the outside of your sub. You should be able to hear very different sounds, near and far from braces.
Well braced sounds dead, a short "tock". In the middle of a free panel it will resonate with an extended sound.
Resonating means stored energy, taken from your woofer's impulse and returned with a delay. The larger the box, the worse it gets.
Such rigid versus resonating cabinets have a lot to do with the very different opinions some people have about the same chassis. The same volume does not always sound the same...
The good thing about it, the stiffer box is always better. Voodoo exceptions ignored.
Also, going thick and heavy is never the best, if we ignore concrete for today. Cleverly positioned, upright panels give stenght we know from a T-bar.
Take a piece of wood, a small hammer or your fingers and knock on the outside of your sub. You should be able to hear very different sounds, near and far from braces.
Well braced sounds dead, a short "tock". In the middle of a free panel it will resonate with an extended sound.
Resonating means stored energy, taken from your woofer's impulse and returned with a delay. The larger the box, the worse it gets.
Such rigid versus resonating cabinets have a lot to do with the very different opinions some people have about the same chassis. The same volume does not always sound the same...
The good thing about it, the stiffer box is always better. Voodoo exceptions ignored.
Also, going thick and heavy is never the best, if we ignore concrete for today. Cleverly positioned, upright panels give stenght we know from a T-bar.
Yes it has improved from the previous attempt and going by what GM said earlier I'm going to add some extra vertical elements to the first cross brace too.
It was laid flat to give support to the front baffle but I can see that laid in the other direction it would be stiffer. Easy fix and I'll do that today.
Being a shelf port the bottom of the box is pretty stiff there but converting from inches to metric I made a significant mistake and I think the tuning may be a lot higher than 25Hz
It was laid flat to give support to the front baffle but I can see that laid in the other direction it would be stiffer. Easy fix and I'll do that today.
Being a shelf port the bottom of the box is pretty stiff there but converting from inches to metric I made a significant mistake and I think the tuning may be a lot higher than 25Hz
More bracing done. I added a stiffening matrix around where the woofer will sit and a few short stiffeners to the sides.
Used up some scraps and offcuts at random.
When the glue sets or tomorrow whichever comes first I'll tip the box over and add the MDF panels to the outside. and do the internal quad fillets in the corners.
This is no longer a cheap test box. So I may as well add the panel of 32mm MDF to the top as well
Used up some scraps and offcuts at random.
When the glue sets or tomorrow whichever comes first I'll tip the box over and add the MDF panels to the outside. and do the internal quad fillets in the corners.
This is no longer a cheap test box. So I may as well add the panel of 32mm MDF to the top as well
