Can anybody help me design a tapped or folded horn sub ? I have the jbl driver laying around and I want to try to build one for it. The size of it won't really matter because I have plenty of space for it. I just need it to make as much sound as possible because it will be used for a college party in a 50x50 room. These are the specs I have found for it: JBL PB12 Re(ohms) 5.30 Fs(hz) 24.80 Le(mh) 3.44 Qm 8.14 Qe 0.331 QT 0.318 Vas(L) 164.30 Xmax(mm) 4.20 SPL(db) 91.00 BL(Tm) 15.18 Mms(g) 97.81 Cms(mm/n) 0.418 Sd(m^2) 0.053 I have tried to figure out how to use hornsrep and other programs but it is just way over my head. I do not need this thing to be perfect or hit insane lows, I just need as much thump as possible from it. Can anybody help me out with some rough measurements for this thing?? I need all the help I can get..
A quick search indicates the jbl pb12 is a complete commercial subwoofer that comes with its own box and amp. So how did you find t/s parameters? Did you measure or do you just know which woofer is in it? I'm guessing the latter since you have xmax listed and that's hard to measure.
Anyway, a woofer with 4 mm xmax isn't going to make much of a sub. Kind of a waste of wood.
What's your budget?
Can you afford a different driver?
Were you planning to use the pb12 amp?
If not, what amp?
If you need to use the pb12 driver, do you know the power rating?
And, as Bart said, what tuning do you want?
Anyway, a woofer with 4 mm xmax isn't going to make much of a sub. Kind of a waste of wood.
What's your budget?
Can you afford a different driver?
Were you planning to use the pb12 amp?
If not, what amp?
If you need to use the pb12 driver, do you know the power rating?
And, as Bart said, what tuning do you want?
Found them where? Where can you find specs (including xmax) on commercial subs? I'm willing to bet the specs are wrong. Even if not wrong you should still measure for yourself to make sure. And xmax is usually lower than published spec, not higher, just fyi.
But anyway, since this is what you want, here's a 3 minute sim. Box is 650 liters net (so add another 25 or 30 percent to account for wood and dead spaces). It's a front loaded horn with 100 watts.
First graph is response in 2 pi space (outside).
Second is excursion (you wanted 6mm, so that's what you get with 100 watts). This WILL need a high pass filter or bassy low frequency music like dubstep will kill the driver.
3rd is theoretical response if you put it in a rigid corner.
If you want my opinion, this is going to be a disaster unless you verify the t/s parameters. Even so, the theoretical response as shown isn't that impressive due to very low xmax so IMO this is a waste of time and wood.
An externally hosted image should be here but it was not working when we last tested it.
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That doesn't seem so great... Okay plan B, I also have a high performance competion subwoofer for car audio applications. It is a dual voice coil 12 inch woofer. It has much more impressive numbers and I have the EXACT specs from the website. I Have a Harman Kardon PA 2200 that I can power it with, at just over 100 watts per channel..
Model TREO ssi12.44
Revc Imp 8.1 (dual 4 ohm coils)
Rms 750 watts
spl 83.96
No 16%
Sd 74.9
Fo 27.66
Vas 1.574 (44.56 L)
qms 2.868
qes 0.584
qts 0.485
mmd 240.07g
mms 246.18g
BL 24.36TM
cms 134.49
Xmax 1.08 (27mm)
Driver Displacement 0.096 ft2 (2.73L)
Would this be a safe set up? If so what would the measurements for the box be?
Model TREO ssi12.44
Revc Imp 8.1 (dual 4 ohm coils)
Rms 750 watts
spl 83.96
No 16%
Sd 74.9
Fo 27.66
Vas 1.574 (44.56 L)
qms 2.868
qes 0.584
qts 0.485
mmd 240.07g
mms 246.18g
BL 24.36TM
cms 134.49
Xmax 1.08 (27mm)
Driver Displacement 0.096 ft2 (2.73L)
Would this be a safe set up? If so what would the measurements for the box be?
To put it in perspective, the horn I posted will kick the living crap out of the box it was previously in, but due to low xmax it's not great for a horn design since it's so large and wood is not really cheap.
FYI I can make any number of changes to make it smaller or louder, depends on what you want (low vs loud vs small).
It's still better to measure them yourself for a variety of reasons. It's not a requirement, but garbage in = garbage out. Especially for complex designs it's best not to trust the published specs.
If you are limited to 100 watts the other driver might be a better choice (but with a higher tuning than previously shown). This one is likely much less sensitive so probably won't go as loud if limited to 100 watts.
I can do a quick sim for you but I'm not going to design the box (fold the horn). That can take a lot of time unless you want a very simple single fold conical "horn". Even if you want the simple version I'm not going to draw it out (but the simple conical horns are super simple) and if you want a more complex horn I can give you a printout of cross sectional area vs length so you can fold it. The vast majority of time and effort in complex horn design is the folding. A quick sim takes about 3 minutes whereas folding a complex horn into a perfect rectangle can take weeks, especially if it was designed with no consideration for the fold.
The other option is to learn Hornresp (or convince someone to do the work for you) and simulate known designs (that already have plans) with your driver to see if there is already a design that will work with your driver. Hornresp isn't as hard as it might seem, especially if all you have to do is plug in the inputs from a picture and add your driver specs.
Just remember, some drivers don't perform very well in horns, you also have to do a quick ported box sim to compare and see if the extra effort and expense is worth it.
And if you want a sim, give a size limit or it's going to be very large, as you can see from my previous sim.
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What do you mean by possible? All you have to do is fold it and build it... It's going to take probably 5 or 6 sheets of plywood and it's going to be about 30 cubic feet externally.
On the other hand, here's a front loaded horn with a 6 inch driver with 13 mm xmax from my records. 96 liters (almost 7x smaller than the jbl sim I showed) in 2 pi space (so compare it to the first graph above, not the lower one). And this is safely within xmax (yours is shown 33 percent past xmax). Even so, the massive jbl horn is only a couple db louder than this tiny horn with similar tuning for a 6 inch driver.
An externally hosted image should be here but it was not working when we last tested it.
So you pick your compromises. And remember, that jbl horn (as shown) is going to take a LONG time to fold. If you absolutely must use the jbl driver I can make the horn smaller and louder but it won't go as low and it will be quite noticeable on bassy low frequency music like rap and dubstep (and even some rock and easy listening music).
Give me some clearly defined goals and I'll redesign it.
Simple to fold or complex?
Exact tuning frequency?
Size limit?
But no matter what you do with this jbl, it's never going to be a whole lot better than a good 6 inch driver in a MUCH smaller horn.
I think I'm going to to build the tuba ht.. I have been researching non stop and they make this thing sound like a beast. I have yet to find anybody saying anything negative about its performance. Your helping me realize it may be easier to just start from scratch and do it right from the beginning.
BFM designs are nothing special. You can find better designs here and at avsforum for free.
Lilmike's F20 cinema horn is similar to the tht, plans are free, drivers are affordable.
Lilmike's Cinema F-20
But the tht and the F20 are both tuned quite a bit lower than you were asking for, and if you limit them to 100 watts you probably won't be all that impressed.
Instead of picking a driver as a starting point, or building a design you heard was a "beast", you should probably start by setting some firm goals and asking if there's anything available that meets those goals.
Lilmike's F20 cinema horn is similar to the tht, plans are free, drivers are affordable.
Lilmike's Cinema F-20
But the tht and the F20 are both tuned quite a bit lower than you were asking for, and if you limit them to 100 watts you probably won't be all that impressed.
Instead of picking a driver as a starting point, or building a design you heard was a "beast", you should probably start by setting some firm goals and asking if there's anything available that meets those goals.
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With 4.2 mm to play with, forget about lows if you want a lot of thump.
A 6th order series-tuned bandpass might do the trick. Starting point 1 cu.ft. for the rear, 0.75 cu.ft. for the front, Fr~34 Hz, Ff~88 Hz, gives just about 3dB extra output, in a box that should work out to around 2 cu.ft. in size, which isn't too bad for a 12" driver. Not much below 50 Hz, but it should still thump good enough. Use HornResp or a similar tool to fine-tune the box size and venting before committing to a build, and be prepared to make adjustments to the vent lengths (particularly the front vent length) to get the best results.
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