Antone Atmarama Bajor wrote on Sun, 01 January 2006 20:49 |
The BS-212 is the first speaker cab I've ever Built. I wasn't ready to build something like the Lab Sub.
I am planing on doing a lab sub in a sealed box.
I wasn't sure if I should do the linkwitz Transform or a dual integrator. 4Lab subs in an ~3cu' Cab can produce ~110dB @ 20Hz. I think it would be good for 1/4 or 1/8th space loading to get several dB of Gain.
The only problem with a lab box with a Q of .707 is its tuned to around 50Hz so an integrator would make it only useful to ~ 50Hz.
Is the linkwitz transform a 12dB per octave Slope?
I could get as much output @ 20Hz as the BS-212 with a sealed box if I had optimal boundary loading.
I could get much greater SPL with a lab 12. But I would need to corner load it to get smooth response down to cutoff (Or have 4 of them). I would also need a delay to align them with my top boxes. 2 BS-212's are almost as large as 1 Lab 12 (No where near as efficient except bellow 30Hz). I think the BS 212's are great for a stage rig. They radiating surface is shallower so more practical than a horn sub.
The biggest problem I have with them is if I'm not careful I can over excurd them in the 30Hz range (just above port resonance) They don't overecurd gracefully (Are there any drivers that do?) They sorta Clack. A sealed box would help control that problem.
Anyhow thats why I built the BS-212. I think its probably close to the best most portable (as two separate cabs) direct radiator "SUB" that anyone can build for the cost (Not specifically my design but just the volume tuning and driver).
Using larger drivers Like the Adire 18's would require a very large enclosure that would not be very portable especially if you wanted to do a diff configuration since this would double the required Volume.
But is it musically Relevant? It sure feels good.
Blah Blah Blah
Happy New Years.
Antone-
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I have not played around with it so forgive me if I am in error. That is why I sent along John Murphy's web page.
First to the room and any loading from floor, walls or in corners a sealed box is the same as a ported box.
My simplistic understanding is you start out with a driver in a sealed box, so you have a 12dB/oct slope. The Linkwitz transform moves that down in frequency, but maintains the 12dB slope.
So it may be possible that you could tune a ported box a little lower, but with a ported box's 24dB/oct slope. So considering a shallower slope perhaps the Linkwitz transform will not get the last couple of cycles of low end.
Or maybe the LAB 12 driver is not suitable candidate for a Linkwitz transform?
If you have the software you might run the numbers.