Originally Posted by mwmkravchenko
Front loaded Horns.***
Tradeoff? You want to go low? You gotta go large. Lots of cuts and fooling around.
Also, limited bandwidth. Don't forget about that. A 4th order bandpass ("front loaded horn") that has significant output at 20Hz isn't going to be worth anything at 100Hz...
The best way to look at different enclosure types is as an efficiency vs. bandwidth tradeoff.
There's no "better," really. Just the set of tradeoffs that matter to an individual.Monopole Bass
generally smallest, more tolerant of driver production variance, air spring protects driver to some degree, can pressurize a room below cutoff (stays a monopole), attenuates mechanical noise from driver best (important for extremely long-throw drivers; the only ones I've played with that are dead quiet at long throws are Aurasound's, and they're expensive when they're available) 2d order low-end rolloff makes them easier to integrate with subs (for mains)
less efficient than anything else listed except for OB, and requires the most excursion for a given output within its passband.
same as sealed generally, except invisible in the room and no airspring, BUT sound leakage is a serious (to me disqualifying) issue. Also, one should generally own the structure; renters need not apply.
4th order BP/"front-loaded horn":
more efficient than sealed in the passband, airspring protects driver to some extent, lower distortion because the coupling chamber filters distortion products acoustically, like a closed box stay monopole below cutoff so can pressurize a room down low
bigger than sealed, larger, upper bandwidth limitations may be an issue with many drivers in many systems (they're generally only good over about 2 octaves), often severe port resonance issues if one uses vents instead of a passive radiator, and they're a lot more sensitive to unit-unit variance in driver parameters.Hybrid Monopole/Dipole Bass
generally larger than sealed (given same woofer), considerably higher efficiency at the bottom of their passband (nearly equivalent to quadrupling amp power), requires lower excursion for a given LF level.
typical dipole problems down low (don't pressurize a room below cutoff, excursion goes way up below cutoff, leading to overall higher distortion if one doesn't employ a suitable highpass filter), more sensitive to parameter variations than sealed, excursion rises quite a bit just above tuning, pipe resonances from the vents are audible and deleterious (especially with very low tunings)
vented without the port resonance issues BUT add cost and if they the PR's don't have enough displacement can result in nasty sounds and/or parts destruction
6th order bandpass/"tapped horn"
more efficient than vented systems
typical dipole issues and larger, severely reduced bandwidth, often massive out-of-band resonancesDipole bass
often reach similar levels of smoothness in the upper bass with fewer units required than systems that are monopole in that region
least efficient, placement requirements make them impracticable in many rooms, LF cutoff often quite high.
All that said, the best bass is any one of the above (assuming sufficient bandwidth on the bottom and on the top), with enough of them used (and properly set up, with control each unit's individual level, delay/phase, and arguably though less important than the above, EQ.) Any single bass unit is going to lead to (to me) unacceptable variance in the room's modal region, unless the room is arena-sized.
For me, in a given system the choice will be between multiple sealed, 4th order BP, or PR subs, with the choice between sealed/PR and BP down to size constraints and the choice between sealed/PR based on available driver displacement and amplifier power.
I strongly prefer sealed mains speakers, because they are easiest to integrate with subwoofers.