My personal opinion on OSB for speaker enclosures aside, I'd suggest that a blade capable of very clean cuts would be a high tooth count carbide negative hook angle as might be used for melamines, double cutting, or a tale saw with scoring blade. Edge routing can't be guaranteed to not chip out - it's simply not intended for this type of work, and certainly doesn't machine as well as MDF or BB plywood.
Likely it's not a blade specifically made for cutting OSB, but it cuts well enough. I don't consider myself too much of a woodworking expert, and these were meant to be prototype cabinets - so I wasn't too concerned with the end appearance, more concerned with how they sound. Though they may still spend some time in my living room, so possibly I should have just used the cheap ply instead. Ah hindsight, my constant nemesis...
I'm curious to see how the routing goes. It will be a 3/8" roundover on all the edges. I'm expecting it to be a bit rough. If it's really awful, I may fill in holes from big chunks that fall out with some bondo or whatever, but trying not to go overboard on the appearance. They are getting big waffle mesh grilles too, to keep the kids hands out of the woofer cones, so they'll look pretty industrial anyway. Hopefully the grilles don't impact the sound much on the low end of the spectrum, 150-750 hz on down.
I'm curious to see how the routing goes. It will be a 3/8" roundover on all the edges. I'm expecting it to be a bit rough. If it's really awful, I may fill in holes from big chunks that fall out with some bondo or whatever, but trying not to go overboard on the appearance. They are getting big waffle mesh grilles too, to keep the kids hands out of the woofer cones, so they'll look pretty industrial anyway. Hopefully the grilles don't impact the sound much on the low end of the spectrum, 150-750 hz on down.
If you have a random orbit sander, I'd be inclined to try that with 80G for rounding over the edges, rather than routing. I'd imagine the irregular surface of the OSB will tend to cause your router to snag a little bit, and if all you want to do is soften the edges a bit, rocking the sander back and forth would work fine - take a bit longer than a router on a smooth surface, but this is OSB after all.
I certainly wouldn't worry about the grille's affect at those frequencies - as soon as the word "kids" is mentioned, I'd compromise on durability over ultimate sonics.
I certainly wouldn't worry about the grille's affect at those frequencies - as soon as the word "kids" is mentioned, I'd compromise on durability over ultimate sonics.
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That's not a bad idea Chris. Belt sander might be even better. But a router was on my wish list anyway, so worth a try... 
I'll try a test piece, and if it's horrid, then I guess I'll sand... Maybe even a sanding flapper wheel thing in an angle grinder.. something is bound to work.
Possibly another idea is setting the circular saw at a 45 and cutting a chamfer instead, with a guide board clamped on.
I'll try a test piece, and if it's horrid, then I guess I'll sand... Maybe even a sanding flapper wheel thing in an angle grinder.. something is bound to work.
Possibly another idea is setting the circular saw at a 45 and cutting a chamfer instead, with a guide board clamped on.
Yeah, didn't really think about it beyond the high tooth count of my blade, but it's rated for plastics too. Never tried to route it, just assumed it would be potentially too dangerous.
GM
That's not a bad idea Chris. Belt sander might be even better. But a router was on my wish list anyway, so worth a try...
I'll try a test piece, and if it's horrid, then I guess I'll sand... Maybe even a sanding flapper wheel thing in an angle grinder.. something is bound to work.
Possibly another idea is setting the circular saw at a 45 and cutting a chamfer instead, with a guide board clamped on.
I think a belt sander would be WAY too easy to get out of control - Makita or Dewalt electric RO sander would be my suggestion. Air powered are even easier, but use a crazy volume of air with which only a fairly large compressor can keep up for extended periods .
I also think the structure of OSB would work against you for chamfering - the material is simply not designed for this type of machining. Great material for cheap sheathing or shipping crates though.
Here is my cut list, for anyone interested.
A few notes-
1. Ply or OSB is nominal 3/4" thick, 23/32" was what I found at the store.
2. I had 2 front baffles cut so I could make them double thick, 1.50" - but the 3/4" OSB felt solid enough that I opted for just a single layer, so in this case you only need qty-2 front baffles.
3. Relating to the baffle thickness, the vent depth needs to remain constant, so the width (depth as installed) of this vent plate varies to keep the port tuned correctly. MY port was only 19.50" wide (24" - .75" - .75" - 1.5" - 1.5" to account for OSB strip braces and also 2x3 cleats at the corners), so my total port length is 6.75", so the width of the vent plate is 6" (6" + .75 thk baffle = 6.75).
4. Internal brace plate is cut to fit, add ventilation holes to suit. I haven't made this piece yet, but will probably just jigsaw out a lot of it. The thing to remember is to leave support front to back, and for the woofer. The cut out for the woofer magnet should just clear the magnet, then add a bit of foam or insulation between magnet and brace so that the brace damps the magnet and basket.
5. I used 2x3 cleats at all corners, glued and screwed.
6. I glued in the rear baffle tight and made the front baffle removable, your choice on that - it's big enough you might not need to make anything removable.
7. Woofer cutout is listed as 16.73, I went 16.625" and it's a nice tight fit. (16.75 test hole was pretty loose).
A few notes-
1. Ply or OSB is nominal 3/4" thick, 23/32" was what I found at the store.
2. I had 2 front baffles cut so I could make them double thick, 1.50" - but the 3/4" OSB felt solid enough that I opted for just a single layer, so in this case you only need qty-2 front baffles.
3. Relating to the baffle thickness, the vent depth needs to remain constant, so the width (depth as installed) of this vent plate varies to keep the port tuned correctly. MY port was only 19.50" wide (24" - .75" - .75" - 1.5" - 1.5" to account for OSB strip braces and also 2x3 cleats at the corners), so my total port length is 6.75", so the width of the vent plate is 6" (6" + .75 thk baffle = 6.75).
4. Internal brace plate is cut to fit, add ventilation holes to suit. I haven't made this piece yet, but will probably just jigsaw out a lot of it. The thing to remember is to leave support front to back, and for the woofer. The cut out for the woofer magnet should just clear the magnet, then add a bit of foam or insulation between magnet and brace so that the brace damps the magnet and basket.
5. I used 2x3 cleats at all corners, glued and screwed.
6. I glued in the rear baffle tight and made the front baffle removable, your choice on that - it's big enough you might not need to make anything removable.
7. Woofer cutout is listed as 16.73, I went 16.625" and it's a nice tight fit. (16.75 test hole was pretty loose).
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a friend who made my 4-RJ18 boxes, used a belt sander for their edges - so MDF can take a lot of contouring. He didn't have a table saw so made one from a little circular saw.
http://i.imgur.com/l7OjCYg.jpg
your big reflex should have ease in the lower octaves and sound nice with JS Bach's organ works. It will be interesting to see if you note any significant panel flex.
http://i.imgur.com/l7OjCYg.jpg
your big reflex should have ease in the lower octaves and sound nice with JS Bach's organ works. It will be interesting to see if you note any significant panel flex.
MDF would have been easier to work with, but not as strong, and also would have been heavier. I should have incorporated some casters in the backs of these, they are already monsters to move. Hate to add now, I'd have to cut thru the reinforcing cleats at the bottom back corner... but I'm putting together another PE order anyway, we'll see. Moving them from garage to house won't be fun, but after that they won't move much anyway.
Lower octave ease is what I'm going for!
I just hope I get some pretty significant output with the 100 watts or so I can feed them. According to the model, I can't push them past xmax til down below ~21 hz, even with a 20 hz/12db highpass filter upstream, and even then max excursion is ~7.5mm, which is above xmax but below xlim, so I shouldn't be able to hurt them at least.
Re: significant panel flex, I'm not sure how much is really acceptable... ideally there would be none, but surely there will always be something. If I can feel them moving or they buzz against a hand laid on them, I will certainly be adding more bracing. I'm intending on adding that center plate brace, then probably a few boards going across as well. That at least breaks the unsupported areas up to spans shorter than 12". A 12" piece of 3/4 OSB feels pretty stiff - but we'll see.
Lower octave ease is what I'm going for!
I just hope I get some pretty significant output with the 100 watts or so I can feed them. According to the model, I can't push them past xmax til down below ~21 hz, even with a 20 hz/12db highpass filter upstream, and even then max excursion is ~7.5mm, which is above xmax but below xlim, so I shouldn't be able to hurt them at least.
Re: significant panel flex, I'm not sure how much is really acceptable... ideally there would be none, but surely there will always be something. If I can feel them moving or they buzz against a hand laid on them, I will certainly be adding more bracing. I'm intending on adding that center plate brace, then probably a few boards going across as well. That at least breaks the unsupported areas up to spans shorter than 12". A 12" piece of 3/4 OSB feels pretty stiff - but we'll see.
MDF, yes, just wear good eye/nose/throat protection; OSB can potentially shred sanding belts, so another thing I've been reluctant to try since I got a nasty cut from a cheap one that quickly snapped at its seam when 'grinding' on a car panel.
Yeah, a high Q driver in a large cab generally doesn't require bracing other than a driver mass loading one as any 'breathing' helps damp the driver.
GM
Yeah, a high Q driver in a large cab generally doesn't require bracing other than a driver mass loading one as any 'breathing' helps damp the driver.
GM
I'd always suggest good quality plywood over any other materials for speaker boxes, but if you definitely decide to go with the OSB, I'd highly recommend cleating and cross bracing between all opposing panels to be of solid wood - even ripped from 2x4 studding (not finger jointed), or hardwood dowelling. Do not locate them on centrelines of panels, and it definitely doesn't hurt to couple them together, although it can be less elaborate than on attached photo.
And nesting at least one of the braces to support the woofer's magnet motor assembly and couple it to the rear / side panels does take some time to get just right - often the single most time consuming piece in the box, but is also worth the effort
And nesting at least one of the braces to support the woofer's magnet motor assembly and couple it to the rear / side panels does take some time to get just right - often the single most time consuming piece in the box, but is also worth the effort
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GM,
Qts=0.33, that doesn't seem all that high.. Or you're referring to the Qms = 11.2?
https://www.parts-express.com/pedocs/specs/295-036-dayton-audio-pa460-8-specifications-46885.pdf
At any rate, a "driver mass loading brace" is which part here? The center board of OSB intended to support the front/back panels at the midline as well as help support/damp the woofer magnet? As usual, you seem to be a step or two ahead of me...
Re: Breathing, I wondered how critical it was to get a truly airtight box (other than the port!)... I want to load the driver as close to the simulation as possible of course, and don't want any whistling/wheezing noises. Everything was glued and screwed, and any gaps that were present were maybe 1/32", hopefully enough for the wood glue to make up (titebond I). I was not going to bother caulking all those seams... should I>?
Thanks!
I can't really recommend working with the OSB in particular, even if it is basically zero void... It's just plain nasty and splintery. And, it wasn't even cheap! $23 a sheet is nuts... this stuff used to be like $8/sheet. If I did it again for prototype, I'd just use cheap ply, fwiw.
Nice looking cabinet construction Chris.
Mine are cleated at all corners, and glued and screwed. OSB was chosen for prototype, I'd like to do these in birch ply if they sound like I hope they do.
Don't locate the braces on centerlines? Because the resulting 2 unsupported spans that you just split have the same distance and thus same resonant frequency? So by offsetting slightly, you'd spread out that resonance? That's an interesting point. Thanks!
Hmm, haven't been following of late, thought this was for a high Qt [>~0.7] driver, so never mind.......
Right, with something lightly wedging the driver against the baffle, or in the case of front loaded, pushing against its mounting hardware.
Vented needs to be airtight, otherwise it will wind up tuned higher, sometimes an octave or more.
Don't know about Titebond's ability to seal gaps; I use PL400, which is excellent, but if in doubt, use something that will.
Yeah, I've only used OSB for decking, wall bracing, etc.. I've used thin Marine grade ply and heavily braced them with various types of scrap when building big cabs 'on the cheap', mass loading them with particleboard and/or drywall and/or cement backer board or similar, even used various types of tile.
Construction site scrap piles kept my costs way down.
GM
Thanks GM.
Got one of the cabinets together far enough today to drop in a woofer and connect it up to the sub out on my cheapy htib garage stereo, so presumably its on a 100hz lowpass or similar, and getting a questionable amount of wattage. Results thus far, with front baffle not screwed down and woofer held in only by gravity, were not terribly encouraging... Facing up, in a 24x36 room w/ open rafter ceiling its very boomy. A few notes; no eq (and maybe questionable built in eq), questionable quality of wattage being delivered, no insulation in box yet, woofer not fastened down, baffle not fastened down yet, no internal bracing yet.
So there's more to do, but i couldn't resist trying it. Disappointing so far :-/
Also get an odd sound out of the woofer when i crank it up a bit.. like a brrraaaap noise, same sort of sound as if you held your hand out so that the dustcap hits it while playing. I hope this is just an oddity of not having it bolted down...
Got one of the cabinets together far enough today to drop in a woofer and connect it up to the sub out on my cheapy htib garage stereo, so presumably its on a 100hz lowpass or similar, and getting a questionable amount of wattage. Results thus far, with front baffle not screwed down and woofer held in only by gravity, were not terribly encouraging... Facing up, in a 24x36 room w/ open rafter ceiling its very boomy. A few notes; no eq (and maybe questionable built in eq), questionable quality of wattage being delivered, no insulation in box yet, woofer not fastened down, baffle not fastened down yet, no internal bracing yet.
So there's more to do, but i couldn't resist trying it. Disappointing so far :-/
Also get an odd sound out of the woofer when i crank it up a bit.. like a brrraaaap noise, same sort of sound as if you held your hand out so that the dustcap hits it while playing. I hope this is just an oddity of not having it bolted down...
Ive got receivers, but they are buried in the living room console - this cabinet is out in a detached garage, where the radio is a htib with a few satellites and sub. 2nd amp will drive these woofers once in the house. I'll see about dragging one of the receivers out there for testing.
Qts is .33, vas is about 14 cf, fs is 28.3 hz.
Box is 9.85 cf, tuned to 28.3 hz.
Granted, the amp i tried sucks and i dont have any insulation in there yet. That "brrrraapp" noise is scaring me a bit, this amp shouldn't have enough power to push it past xmax in this box.
Qts is .33, vas is about 14 cf, fs is 28.3 hz.
Box is 9.85 cf, tuned to 28.3 hz.
Granted, the amp i tried sucks and i dont have any insulation in there yet. That "brrrraapp" noise is scaring me a bit, this amp shouldn't have enough power to push it past xmax in this box.
"brrraapp" is a perfect description of that stressful sound. might be the protection circuitry - kinda sounds like low frequency sawtooth wave IIRC and excursion shoots up. DJK has mentioned this but I can't remember the proper term. I called it "ratcheting" when trying to drive a very low Z reactive load consisting of a series 20mH L and 600uF shunt. (a "boost network" - of course it depends upon a constant voltage source to work, as do some crossover tricks - so tube amps with zero loop feedback won't work)
it may all be fine when you get it together.
you could build a Gauss 5181 or scale K15 up 1.2:1 as I believe Karlson did, for a punch machine.
it may all be fine when you get it together.
you could build a Gauss 5181 or scale K15 up 1.2:1 as I believe Karlson did, for a punch machine.
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Hmmmmm.
Qts .33, maybe 5.5ft3 with 28hz tuning, you'd be 9db down at 28hz, that's perceivably not much rumble.
I'm estimating that be ideal 4th order.
You have an ebs, extended bass shelf, box thats bigger and tune below expected f3.
Lean, or not much low bass in my book.
A qts .33 driver works well for big boosting at fs or your tuning frequency.
Dont be afraid to add 6db boost at 30hz, then ideally subsonic filter below that.
Actually you could clip the small amp easily for sub use, then square waves come out, that will bottom out the driver real quick.
Qts .33, maybe 5.5ft3 with 28hz tuning, you'd be 9db down at 28hz, that's perceivably not much rumble.
I'm estimating that be ideal 4th order.
You have an ebs, extended bass shelf, box thats bigger and tune below expected f3.
Lean, or not much low bass in my book.
A qts .33 driver works well for big boosting at fs or your tuning frequency.
Dont be afraid to add 6db boost at 30hz, then ideally subsonic filter below that.
Actually you could clip the small amp easily for sub use, then square waves come out, that will bottom out the driver real quick.
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