I,ve built a cabinet 36 x 24 x 24 in 1" MDF using 2 x JBL GT5 12" drivers. With internal bracing and drivers it has a little over 260 Lt volume. I've made up 2 front baffles to try both tuned (4 x 4" x 22" pipes - thanks John) and the sealed cabinet methods (thanks Moonfly). I,m trying to source an amp, but it will most likely be a used Behringer (driving 2 ohms) Europower or Inuke. My Yamaha DSP E800 outputs to a subwoofer at a fixed 90 Hz. My speakers are full range and the Yamaha is operating in stereo mode into a NAD amplifier. I think 90Hz is on the high side and may leave a hole in the subwoofer response curve. Am I better taking off the subwoofer feed directly from the preamp output from the Yamaha and use some kind of low pass filter 40-60Hz? arrangement, or just go with the 90Hz output??
That ported sub will be good to 22hz so you will definitely need a HPF (tune is about 25hz in 240ish litres). You will get a ton more output from the ported sub though, in the region of 6-8db more, while the sealed sub would go deeper. So you will be basically deciding if the sealed sub has enough output, and if not, then ported would be the way forward.
I would install the ported baffle first, and simply stuff the ports to seal it, re-eq, then see what you think of the differences. Its would be easier than swapping baffles, and if you can turn the HPF on and off, you would have a sub you can run sealed or ported.
Only thing I would say, is I would run with 3 of those ports rather than 4. It lowers the tune to about 22 hz, which still offers high spl output but offers slightly more extension while air velocity is still fine. The HPF could be lowered to 18hz then, but thats just my opinion.
Thanks Moonfly. I,m going to use the sub for films and music equally, so I,m just looking for a solid and tight bass rather than outright volume - certainly not too reference levels. I,ve already cut both the baffles (vented one has 4 plastic pipes glued in!) so I,ll be needing a foam bung. Where can I buy a HPF, how do I wire it and how much - will the sealed version need a HPF? Which option offers the best high frequency response, vented/sealed, I,m going to need it to to respond well up to 90Hz any ideas?
Both models will be similar in the upper bass region, just the ported will have more low end output, and obviously you will have the sound of the port contributing to the overall sound. The sealed sub would go deeper, but it really pushes the drivers to their limits so its really a case of which you like. Only the ported would need a HPF.
For a HPF, I like this one as it comes with a 2 band PEQ and bi-passable HPF (subsonic filter). I may know someone in the UK who owns one as well, and isnt using it so may sell on.
That wont work. The action of the drivers would result in perfect phase cancellation and the sub would output very little audio even with the drivers pushing hard. Push pull only works if you flip one driver around. In any scenario, both driver must move towards and away form the cabinet together.
If you want that HPF, its going for £75. It would need to be sold via the classifieds, but I can let the owner know and post a link to his sale thread if you wished.
Thanks Moonfly, I,ll bear the HPF filter in mind. Surprisingly, so far this sub has only cost me £100 including the drivers to build, but I still have to get the amplifier and paint. Do you think a Behringer EP1500 has enough power for a sealed or vented option at 2 ohms?. The box measures 24 x 24 x 36 which sounds alright, but in the room it,s huge - like a small table!!
You can do more with a BFD but it only works to 20hz and you will need to spend a great deal more time learning how to use it properly before you can implement it properly. If you need a HPF, and one setting below 20hz, chances are you will need a stand alone unit.
Thanks Moonfly. Does anybody know where I can buy that foam/rubber tape with sticky on the one side. I,ve just unwrapped the drivers and found they come with the rubber gasket stuck to the front rather than the back face??