Brendan: With so many production boxes on the market, why do we still see so many “customs boxes” in bid packages.
Craig: Broad question this. It may be that the project needs a particular rigging solution… or the coverage of available boxes does not work. We used to use lots of custom boxes, but most of the products now exist and solve our problems, so we usually only do extensive custom for stadiums, theme parks, etc.
yamaha3000: And what do you think about the whole line array explosion from the manufacturers?
Craig: Line arrays have of course existed for over 40 years now and are all based on the physics papers published in the early 1950s. They solve lots of problems in the vertical plane…can also get you in trouble, but are limited in horizontal plane.
Chris Kathman: Get you in trouble how?
Craig: Line arrays (similar to V-DOSC) tend to have very defined vertical pattern control but loose horizontal control. This is not a negative in itself, but it does mean that you need to keep them spaced apart by at least one wavelength at the lowest frequency of usage unless you want horizontal LF interference.
yamama3000: How are the manufacturers getting around the copyright laws concerning horn flares which make the VDOSC work?
Craig: I can’t tell you exactly what the V-DOSC patent covers, but I can tell you as a patent holder that there are many ways to circumvent the process. The competing manufacturers (EAW, JBL, EV, etc.) will all say that they are not infringing the patent. Note that the patent does not cover line arrays, but the HF waveguide itself.
Moderator: Craig, I’d like to go back to the beam steering topic if we may…We have a couple follow-up questions.
Craig: Shoot.
Michael: Is there any written text or paper that explains how to use beam steering effectively—examples of productive use and problem solving? If not, will you consider issuing such?
Craig: Lots of papers available. Beranek “Acoustics” and Olsen “Acoustics” are both excellent. Beranek is no longer published, but Olsen is published by American Acoustical Society. Many, many papers published in AES journals. Some good…some confusing.
Tucci: But how wide a range can you effectively null? What’s happening at 80 or 100 Hz in your example?
Craig: At 80 or 100 Hz you will have about 6 dB drop, same at around 30 Hz. If subs go higher, say 140 Hz, then you will get a side lobe as loud as the front lobe and a null at 45 degrees. Nasty.
yamama3000: Is beam steering Showco’s whole “secret”? With the Prism rig?
Craig: Showco Prism uses a lot of “beam steering.” Jim Brawley, who was heavily involved in its design, is extremely knowledgeable.
Michael: Do you have an engineering degree in acoustics? Just curious. [i.e. what does it take to be a design consultant?]
Craig: Oh boy, great question. Actually I trained and studied to be a mechanical engineer in an oil refinery. Just spent a lot of years gettting mad that I could hear things with arrays and not predict them. Kept asking questions until I started to get an understanding. Still a bunch to learn though.
Tucci: Have you successfully used the directional subs from Meyer?
Craig: No, I have not used the Meyer subs, although I look forward to a client who has enough money…Actually it is a cool piece of gear. It is relatively simple to achieve the same thing with two separate boxes and a basic DSP. Same as the techniques for cardioid mics.
Charles: With regards to beam steering, are there any “rule of thumb” ways for alleviating the “power alley” effect?
Craig: By power alley I assume that you mean the LF build-up in the center of the room…right?
Charles: Correct.