We are introducing the new generation of Constant Directivity Wave Guides, as defined by our US Patent.
The new guides are simple add ons that attach directly to the mid and tweeter panels. They are lightweight, lack baffles, are inexpensive, eliminate treble rolloff, exhibit less than 1dB insertion loss, and may be used with planar drivers other than our own, such as DG Neo 8 and Neo 10, Hi-Vi, and EMIM’s. The waveguides can be used on dome tweeters and ribbon supertweeters, but are not designed for cone midranges. No crossover adjustment is required.
Beyond improving directivity, the new CDWG’s positively influence sound quality in other ways, such as midrange smoothness, bass solidity, naturalness, and of course, dispersion.
The principal of the diffraction slot is well known and is the basis for almost all constant directivity devices for 30 years now. With planars, unfortunately, simply making them narrower is no solution, as their sensitivity would be very low if made wide enough (2/3″) for CD dispersion up to 20kHz.
If you mask off part of the diaphragm to make a narrower slot it causes a lot of energy to be reflected back into the driver, and the resulting IM distortion is quite objectionable.
Our solution was a damped slot, with substantial absorbtive as well as reflective components. This is what made our CDWG patentable over the prior art. Many opponents objected to the granting of the patent, but after 5 years, we prevailed.
In the second generation CDWG, the device is reduced to its simplest components and attached directly to the driver frame. The opening here is about 1″, corresponding to a 12 kHz CD characteristic. This is fine for our panel, which rolls off mechanically at that frequency. Only half the diaphragm is forced into constant directivity, and then there is a gradual transitiion to narrow dispersion. In this fashion, there is little or no audible treble rolloff for the on-axis listener, and insertion loss is very low. The panel now mimics the cardioid dispersion pattern of many musical instruments and voice. The difference in disprsion patterns is what makes speakers sound so different from live sound as far as directivity is concerned.
A similar CDWG with a narrower opening, designed for planar tweeters, is also available, as are antiffraction masks for tweeters that are already narrow enough for CD behavior to 20 kHz.
It takes a pair of CDWG masks to treat a single panel or tweeter. You would need two pair to treat the panels in a pair of single panel speakers like the 626, or the single tweeter in any FST speaker.
