Trouble Maker
Addicted to Fun and Learning
Why doesn't, say, KEF make speakers with wide baffles? Because they want their speakers to sell.
I mean, it does visually look good from the front, but the depth is an issue for me from an efficient use of space viewpoint. Speakers that are more than a foot deep that I'm supposed to have out from the wall and my room is only 12 feet deep. What is the point of having a TV that is an inch thick mounted within an inch of the wall if I'm going to need speakers that stick out two feet into the room? And 1 of them is kind of by the front door. I guess it works for people with McMansions, but not as well in my smallish 1925 bungalow farmhouse. For me the Left/Right is not as big of a deal as the center depth.
But there is also this. I'm not offering credence to the validity of this, but simply saying they do have some technical reason behind why they say they use narrow front baffles. It seems like many, many speakers follow something along this guideline so there must be something more than just looks behind it.
https://us.kef.com/pub/media/documents/rseries/rseries2018-white-paper.pdf
It has been known for many years, and is illustrated by Leo Beranek in his book “Acoustics”, published in 1954, that the acoustic impedance of a driver (the interface between the diaphragm motion and radiated sound) is smooth when mounted both in an infinite baffle (as expected) and at the end of a long tube the same diameter as the diaphragm. This latter situation comes about because the dispersion of the driver is such that it doesn’t acoustically “see” the edges of the tube. The physics of this situation can be bent a little and it can be shown that a driver mounted in a cabinet not much wider than itself has a very low level of diffraction. It’s not perfect, but the level of diffraction is much lower than it would otherwise be.
If we look at the drivers used in the R Series systems, we can see that the bass drivers follow this requirement, but the midrange and tweeter drivers do not. Normally, the tweeter would be the most to suffer because it is much smaller than the width of the cabinet, which is determined by the diameter of the bass drivers. However, in the Uni-Q driver (more of which later), the tweeter fires into an acoustic waveguide formed by the midrange diaphragm and it is the diameter of this relative to the width of the cabinet that determines the level of diffraction.
There is more work to be done, because the diameter of the midrange (for other reasons) is smaller than that of the bass drivers, and it is here that the lateral thinking comes into play.
Around the Uni-Q driver array is what is normally called a trim ring. Not simply a decorative piece, the R Series trim ring is specially shaped and engineered. It increases the effective diameter of the waveguide such that the driver array “sees” the edges of the cabinet much less than if it were mounted normally. Hence the name “Shadow Flare”. The level of secondary radiation is decreased, resulting in less time-smearing, greater clarity and a smoother response.