Originally Posted by A9X-308
I saw those JBLs just the other day and thought they looked cute, so I might try a couple out for the bedroom especially if they sound decent as well.
JBL has done something very VERY clever with the Control Now. It's easy to miss, because it looks like a plain ol' MTM. But it's actually very unique. Here's why:
In a waveguide or a horn, the ideal transducer would have wide bandwidth and would be very small. For instance, if I could get a 1" driver to cover 100hz to 20000hz, that would be fantastic. And this is the reason that Danley uses those ultra-expensive BMS coaxes. They are expensive but they are worth it, because they come as close to an ultra-wide bandwidth transducer as we can get.
And I think that most people don't appreciate how important it is to use a small driver. For instance, if you put a 1" dome tweeter in a horn you can't get very good results because the ideal transducer is a flat piston. And this isn't some academic argument - you can see the results immediately if you try it. The top octave goes to hell, particularly as the diaphragm gets bigger.
In summary, the ideal driver for a waveguide is small and has wide bandwith. And the ideal wavefront is flat.
And again, I want to stress that this isn't a subjective comment. I'm not saying "Scan Speak sounds better than Vifa." That's a subjective opinion. The idea that the ideal transducer has a flat wavefront and wide bandwidth is a fact
, based on simple geometry. If we deviate from this ideal, we get higher order modes and the top octave of our speaker will have awful frequency response. It's just geometry, and it's why my reference speakers have a 1" transducer.
If you can find a transducer that produces a flat wavefront, there's really nothing stopping you from using a VERY large waveguide. The $1400 BMS compression driver works very nicely on a 30" horn, and the only limity factor is your wallet and your tolerance for loudspeakers that are the width of a refrigerator.
So here's The Really Cool Thing about the Control Now, which is that it's designed to produce a flat wavefront, and it uses your wall as the waveguide.
It's not obvious until you look at the cabinet from the side, but once you do, you'll notice that all of the diaphragms are time aligned. In addition to that, the frequency response is REALLY REALLY hot, but I'm convinced that this is by design. A horn is a physical low pass filter, so when you bolt those JBLs into a corner, the horn loading that's provided by the wall brings up the low end, and you end with flat response in-room. I've measured them myself, and without reinforcement, the top end is tipped up to a huge extent.
But put them in a corner and they sing.
This is similar in some respects to the old Klipschorns. But the JBL excels because the drivers are very small and very close together, which is critical to pull off this trick. (As noted earlier, the ideal transducer would be small and wide bandwidth. If we can't get it small enough, we need it to be flat, like a disc.)
The attention to detail is admirable too; for instance the dome of the JBL tweeter isn't a semi-sphere, it's much shallower than a conventional dome. This is done for a couple of reasons. The ideal transducer would be flat, but if you use a flat dome, it won't work. (It's not strong enough.)
So the use of a semi-flattened semi-sphere gets us closer to 'ideal', and is just one of a million details that shows some serious thought went into the JBL design.