X, as you know, over on the OB thread one well known and respected OB aficionado opined that SLOB is effectively a waste of time.
This might seem like a naive question but perhaps there are factors in play that I’m not aware of, so: do you get the same level of output to the rear of the cone as at the front and does the frame / magnet structure etc not create distortions?X, your structure is smallish, it is still indirect coupling -- bracing the drivers magnet to magnet (and use ready rod as bolts for pairs of opposed drivers, you can maximize the effect. If you don’t like seeing the magnets or the baskets get intrusive sonically, it gets a bit trickier, you need 2 slots on the front (but you get even more structural integrity).
Force cancellation of dual opposed woofers with direct magnet to magnet bracing and rods is hard core. In a sealed sub with monster drivers and kilowatt amps that would be a beautiful thing. I can imagine a sealed sub in full cry with no box vibration while the ceiling implodes and the walls crack.it is still indirect coupling
Hi Studley,This might seem like a naive question but perhaps there are factors in play that I’m not aware of, so: do you get the same level of output to the rear of the cone as at the front and does the frame / magnet structure etc not create distortions?
wired out of phase but the front slot radiation alternates between front and back side of the woofers so summing in phase acoustically (every other woofer is inverted electrically and acoustically so still in phase). All even order distortion cancelled if woofers are matching.Newtonian forces yes, but why a reduction in second. One set would need to be wired acoustically out-of-phase (ie no bass) to acheive that.
yes that distortion graph is impressive. Where does the unEQ’ed woofer response roll off from? are there a resonance from the cavity on the back (hollow back)? maybe what the pyramid shaped damping is for?Assuming distortion comes in part from suspension K(x) and motor BL(x) non linearity. By having one driver move in opposite direction but mechanically, still having both pushing air out is how the distortion is cancelled - sort of like how long tail pair (LTP) input stages cancel even order distortion.
That’s why the drivers are arranged cone to magnet and wired anti-phase electrically but in phase mechanically.
Note the extremely low 2nd harmonic distortion below 60Hz. About -55dB at 50Hz (that’s very low for open baffle 90dB).
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