You must be close, giving me for a (430L = 15.185ft³)
VB = 430.0 L, FB = 32.0 Hz
F-3 dB 33 Hz
F-12 dB 23 Hz
It needs max. excursion protection for this frequency (<25Hz).
I'll have protection. Well... whattya think? On paper is this box going to rock the house? I'll keep my expectations in check, but if it hits like something I would find in a stack at Red Rocks Amphitheater, I will be more than a happy camper.
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Apparently, there is only one place in Denver that sells BB plywood and it's $110 for a 4'x8'x3/4" sheet. HD cannot order from them. The place is called Austin Hardwood.
I'll keep checking around.
I'll keep checking around.
BR do provide the most SPL output per truck space, but use more power and drivers than TH to do that.
TH are relatively new, and the primary commercial vendor (Danley Sound Labs) is not well known in the touring industry.
Most sound companies must provide for riders, and it can be a hard sell convincing an engineer that a single 18" TH can keep up (or better) a dual 18 BR.
That said, having done A/B tests on side by side outdoor stages, I know that a pair of my Keystone TH can "keep up" with eight Meyers 650P dual 18".
Your new BC 18TBX100 cabinets should have slightly more clean output than the Meyers 650P, as the BC has a bit more Xmax than the drivers in the 650P.
Looks like in your part of the country, HD carries the birch faced columbia ply that seems to be fir core. About $46 per sheet. Fir is pretty much in the same ballpark as birch for stiffness and density. But but baltic birch will be a superior material.
Excellent. Personally, I like braces that are in line with direction of airflow, to cut down on flow losses. Braces perpendicular to the air flow cause resistance. I also feel its very important to roundover the entrance and exit to the ports to cut down on compression. Check out this quote from my recent build thread:
Inside end of the slot port inner wall, has an extra slat of wood for a larger 180 deg round over, picked up this idea from someone making high output slot port boxes with various rounded transitions...
Port wall mounted, 45 degree angle in place, should make for a reasonably smooth transition. I may bondo or add wood to the 45 to smooth it a bit further...
Inside of port, minimal braces, still need to add a port brace to the front...
Back of box without top, cross brace ties the side braces together making one very stiff section, but off the back wall, which will hopefully allow better flow to the port. The panels are very stiff here because the bracing is exceptionally stiff, even though the unsupported panel span is ~8"...
Box as it sits so far, need to fit baffle. Roundover on port is not glued in yet. Front face is 20x16". You can see where the woofer will screw into the braces. The baffle will be 1/2" ply also, recessed from the port face 1", giving space for a square grille around just the woofer area, the port will have no grille. Will probably do 45 degree bracing behind the baffle that will catch the other mounting screws. Need to internally dampen the box with coating or dynamat, because it certainly has some higher frequency resonances....
With a pair of 15's and an entire system that fits in a sedan, they sustain 110+ db in a 650 sqft room or at about 25 feet away outdoors, with extension to around 30-35hz. And sound fantastic.
http://www.diyaudio.com/forums/subwoofers/219923-ultra-compact-ported-15-dayton-ref-ho-8.html
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I love the idea of braces inline with the airflow, but I'm sure how to do that with box handles that will look identical to this.
QSC GP218-sw Passive PA Subwoofer
QSC GP218-sw Passive PA Subwoofer
thanks 🙂
I put masking tape on both sides of the 45° corners, about an inch away.
Then liberally put on Universal Construction Sealant and made the rounding with the back of an empty sealant container. Removed the masking tape, a bit of touching up (that's why the wood looks wet) Done!
I put masking tape on both sides of the 45° corners, about an inch away.
Then liberally put on Universal Construction Sealant and made the rounding with the back of an empty sealant container. Removed the masking tape, a bit of touching up (that's why the wood looks wet) Done!
Looking at standard size handles, they have a cutout of 6.75x4.25. Your internal dimension is 22.5", so two braces would be spaced at 7.5", which would clear the handle easy especially with a 3x1/2" brace. You could do the same on the other side walls, and also against the port. These braces would go right up to the back of the baffle and help support it, which may eliminate the need for a double thickness baffle, your choice. Then in the back tie them around in a U shape #, and also in the middle with cross braces. With 3x1/2" braces in a 3/4" box, this will be extremely solid. Sand or route sharp edges to improve air flow.
You may want to build one box and experiment with the port tuning to see what sort of extension you really want vs. output/punch. We haven't talked about port size at all, I would urge you to go as large as possible as to reduce compression at high output. My ports are 15x2.5 or 37.5sq inches, effective 24" length, 35hz tuning, which does about 25 m/s air speed at maximum output, high passed. 20m/s is preferable, but I had major space limitations and compensated with the roundovers. Also try to stay under a 8:1 ratio of W vs. H for the port, so at least a 22.5x3 port for 67.5 sq inches, assuming that will fit. The bigger the better to reduce compression in the low bass.
Some people like to stuff bass reflex boxes, this lowers tuning at the expense of output. I prefer to internally damp the panels with a rubbery material like roofing mastic, etc. The lack of stuffing maximizes air flow and output.
Post #31
Hi pognoot,
A center port may look better, but a single shelf port using an exterior panel uses less wood, and is easier to round of at the inside of the box. Either way I'd recommend, that you cross-brace the port at least twice.
Regards,
Hi pognoot,
A center port may look better, but a single shelf port using an exterior panel uses less wood, and is easier to round of at the inside of the box. Either way I'd recommend, that you cross-brace the port at least twice.
Regards,
The USB box seems like a good (bandpass horn) design, but it is really a kick bin (55hz -170 hz) intended to be used with multiple large horn subs in a very loud and large stack.
An externally hosted image should be here but it was not working when we last tested it.
Another nice thing about bass reflex subs is that they have enough bandwidth to cover both the sub bass and kick, you can run them 30hz - 200hz pretty easily.
For a subwoofer, what to you get from rounding over the braces and smoothing the bends, in a reflex box?
Rounding over and smoothing port parts reduces turbulence. At high drive levels, port turbulence can cause "chuffing" noises, and reduces output the port is capable of.
Rounding over braces and smoothing box parts not directly in the port path probably has no measurable effect, but it makes them easier to paint 😉.
i cant believe the cheapest you can find BB in denver is 110 dollars. Look around for 5x5. i mean hell. I pick up 3/4 BB here for 30 bucks a sheet in 5x5.. I could ship you a pallet and still make money lol.
EDIT. 3/4 is 41, 1/2 is 30. Previously 1/2 (this was six months ago) was 24 and 3/4 was 34. I just hit up the lumberyard.
btw, I'm in NC. you just have to find the right place to look. If I went to the easiest accessable lumberyard, 1/2 baltic birch would cost me 79 a sheet. after a couple days of searching, I found the prices I listed above about 25 miles away. turns out they sell the first lumberyard I visted the baltic birch they stock and all they do is mark it up 150 percent....
btw, I'm in NC. you just have to find the right place to look. If I went to the easiest accessable lumberyard, 1/2 baltic birch would cost me 79 a sheet. after a couple days of searching, I found the prices I listed above about 25 miles away. turns out they sell the first lumberyard I visted the baltic birch they stock and all they do is mark it up 150 percent....
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