Hi chaps,
I have a pair of JBL GTO1214 drivers (4ohm each) that aren't currently in use.
I'm thinking of putting these into a cabinet for PA/party use: a similar idea to Art Welter's dual Lab12 ported design.
The way I see it, a pair of these drivers will have a cone area similar to that of an 18" driver. With 1/2" one-way travel, there should be some considerable output available.
That said, these are heavy cones (mms ~200g IIRC) so they'll need a considerable amount of power to boogie.
Because the cones are rather heavy, some force cancellation would be handy as this ought to stop the cabinet walking around. This pushed me toward the idea of a PPSL enclosure. Distortion is reduced by the opposite mounting of the drivers, and the drivers themselves are also out of the way of prying fingers, drinks, feet etc.
That said, the plenum adds a fair amount to the cabinet volume, so this might dissuade me yet: I'd like to keep this compact in order to keep transporting the thing nice and easy. One-man lifts only (though I can move two-way 2x15" cabs without much bother, so the weight won't be a huge issue).
The enclosure will be in the 80-120L range, probably ported tuned to the mid-low 30s. I'd be open to other design suggestions such as tapped horns, but I'm struggling to get a decent 35Hz TH with these drivers without going to ~150L, which is definitely bigger than I'd like to use.
Advise would be appreciated, even if its just "sell those drivers and get something worthwhile".
Cheers
Chris
I have a pair of JBL GTO1214 drivers (4ohm each) that aren't currently in use.
I'm thinking of putting these into a cabinet for PA/party use: a similar idea to Art Welter's dual Lab12 ported design.
The way I see it, a pair of these drivers will have a cone area similar to that of an 18" driver. With 1/2" one-way travel, there should be some considerable output available.
That said, these are heavy cones (mms ~200g IIRC) so they'll need a considerable amount of power to boogie.
Because the cones are rather heavy, some force cancellation would be handy as this ought to stop the cabinet walking around. This pushed me toward the idea of a PPSL enclosure. Distortion is reduced by the opposite mounting of the drivers, and the drivers themselves are also out of the way of prying fingers, drinks, feet etc.
That said, the plenum adds a fair amount to the cabinet volume, so this might dissuade me yet: I'd like to keep this compact in order to keep transporting the thing nice and easy. One-man lifts only (though I can move two-way 2x15" cabs without much bother, so the weight won't be a huge issue).
The enclosure will be in the 80-120L range, probably ported tuned to the mid-low 30s. I'd be open to other design suggestions such as tapped horns, but I'm struggling to get a decent 35Hz TH with these drivers without going to ~150L, which is definitely bigger than I'd like to use.
Advise would be appreciated, even if its just "sell those drivers and get something worthwhile".
Cheers
Chris
Hi GM,
I was thinking of buying a 2nd hand Behringer EP1500 on eBay, and put the JBLs in parallel. Bench tests indicate it won't stand both channels driving 2ohm (the PSU current draw gets silly), but I'd expect it to be fine driving only one channel at 2ohm: the other channel is blown.
Here's a link to the power amp tests:
Measuring Amplifiers - Page 2
I'll have another look at TQWTs and see what can be done
Cheers
Chris
I was thinking of buying a 2nd hand Behringer EP1500 on eBay, and put the JBLs in parallel. Bench tests indicate it won't stand both channels driving 2ohm (the PSU current draw gets silly), but I'd expect it to be fine driving only one channel at 2ohm: the other channel is blown.
Here's a link to the power amp tests:
Measuring Amplifiers - Page 2
I'll have another look at TQWTs and see what can be done
Cheers
Chris
Chris,
The average power draw using sine waves is around 10 times (or more) what it will be playing music.
Have you tried modeling the JBL speakers in Hornresp using any of the usual TH enclosure specs?
For party/PA use the extra output per watt is a good thing.
Absolutely - I've been playing around with GTO driver numbers in WinISD and Hornresp, the response looks great but then you look at Max SPL and the power it takes to get there... it's not so great.
If you already own them, go ahead and build a reflex box to see what they do! Don't expect huge output for party use and I wouldn't run out to buy them for PA either, but they'd definitely make for a decent home theatre/music sub
Well, seeing that option is already nixed, have you considered a 4th order BP design? You might get a few more dB out of them with something like that, at the expense of some low end which will likely not be missed anyway considering the planned use.
Build your own 2x12" TH (The Kraken 212 TH)
Its 500 liters though.
Its 500 liters though.
An externally hosted image should be here but it was not working when we last tested it.
Yep, the Kraken is waaay too big, but the low end extension is handy.
Brian, I've never heard the term "nixed" before. Would you mind explaining?
I'll have a play on Hornresp to see if 4th order BP designs are worth a go. I must admit that I hadn't really considered them.
BitSmasher, I agree the sensitivity will be an issue. The other way of looking at it is that, with these drivers I'll get quite a lot of LF extension in a fairly small box. A powerful amplifier will be needed, but that'll be re-usable for bigger projects when I have more space to play with.
The drivers are quite hardy, though: I pushed a 600w amp to clipping, driving a pair of the drivers in a 35L sealed box, at 5Hz. They smelt warm, but still work fine. I expect with a bigger enclosure and a less demanding duty cycle, you could get away with 500w per driver.
Cheers all, looks like there's more simulation to be done.
Chris
PS - BitSmasher, I used a single 1214 in a 75L ported box with a big slot port tuned to 18Hz, then added eq to flatten the response down to Fb (like a Linkwitz Transform, but not quite). If you've got a couple of hundred watts to play with, its an impressive sub.
Brian, I've never heard the term "nixed" before. Would you mind explaining?
I'll have a play on Hornresp to see if 4th order BP designs are worth a go. I must admit that I hadn't really considered them.
BitSmasher, I agree the sensitivity will be an issue. The other way of looking at it is that, with these drivers I'll get quite a lot of LF extension in a fairly small box. A powerful amplifier will be needed, but that'll be re-usable for bigger projects when I have more space to play with.
The drivers are quite hardy, though: I pushed a 600w amp to clipping, driving a pair of the drivers in a 35L sealed box, at 5Hz. They smelt warm, but still work fine. I expect with a bigger enclosure and a less demanding duty cycle, you could get away with 500w per driver.
Cheers all, looks like there's more simulation to be done.
Chris
PS - BitSmasher, I used a single 1214 in a 75L ported box with a big slot port tuned to 18Hz, then added eq to flatten the response down to Fb (like a Linkwitz Transform, but not quite). If you've got a couple of hundred watts to play with, its an impressive sub.
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Google is your friend :
https://www.google.com/search?q=nix...57&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8
GM
: https://www.google.com/search?q=nix...57&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8
GM
Me again,
Dragging this back up as I definitely need more output from my subs: last night I blew my Tannoy T40 (pictures over on the PA forum) with a combination of ample amplifier ratings and mashing pop music into the compressor. In hindsight, the sub didn't stand much chance - compression is just as bad as clipping as the power delivery still increases as you bring the average level toward the peak. I'll avoid that in future - expensive mistake, too: those RCF drivers are £160 each.
I think I'll throw some ported boxes together for the JBLs - a pair of 50L cabs tuned to ~30Hz looks decent on the graphs, and would be a much easier lift than 100L and both drivers.
6th order bandpass looks reasonably promising, but you can get similar at the bottom end with a 20% smaller ported box (above the very bottom end, ported box wins 40-50Hz, but the BP wins 60-80Hz - I'd call it a draw). 4th order BP just doesn't get the sensitivity up enough, so I've ruled those out.
Chris
Dragging this back up as I definitely need more output from my subs: last night I blew my Tannoy T40 (pictures over on the PA forum) with a combination of ample amplifier ratings and mashing pop music into the compressor. In hindsight, the sub didn't stand much chance - compression is just as bad as clipping as the power delivery still increases as you bring the average level toward the peak. I'll avoid that in future - expensive mistake, too: those RCF drivers are £160 each.
I think I'll throw some ported boxes together for the JBLs - a pair of 50L cabs tuned to ~30Hz looks decent on the graphs, and would be a much easier lift than 100L and both drivers.
6th order bandpass looks reasonably promising, but you can get similar at the bottom end with a 20% smaller ported box (above the very bottom end, ported box wins 40-50Hz, but the BP wins 60-80Hz - I'd call it a draw). 4th order BP just doesn't get the sensitivity up enough, so I've ruled those out.
Chris
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