Transcript
Pro Sound Web Live Chat With Craig Janssen
Moderator: Greetings Craig :-) And welcome, everyone, to the chat. Let's get started.
Charles: What analysis packages do you use for designing and tuning systems and why?
Craig: For designing we use a number of packages. We have JBL CADP, EASE, F-Chart (EAW), EV Array show, Renkus ALS and George Augspurbers custom program. We use different programs to solve different problems. CADP2 for coverage, and array programs to model array behaviour. As for "tuning', we own and use a bunch of stuff. Mostly I use SMAART and TEF. Mostly Smaart though. SMAART allows us to get quick and accurate measurements from a variety of clusters. We use a Soundweb to switch up to 6 mics. Usually I use 2 computers concurrently, one in measurement mode and one as resultant.
Moderator: We have a couple related follow-up questions…
yamama3000: What is the F-Chart and how does it work?
Craig: F-chart is a custom program from EAW (not sold) which allows extremely accurate predictions of device interaction. It's a pain to use, but provides tremendous accuracy and allows each device to have filters inserted upon it and adjusted, and then predicts the results.
Brendan: Do you feel SMAART has gained equal acceptance as TEF?
Craig: I think that SMAART has surpassed TEF for industry acceptance by a wide margin.
Michael: So no go on the SIMM system? How come?
Craig: As to Meyer SIMM, I am supposedly "qualified" (been to training) but can't justify the cost of the unit. Also it is not nearly as flexible as SMAART for complex system tuning. If I was on the road touring, I would love to have SIMM.
lilbob: Which of these (software) in your opinion gives the most accurate actual HF coverage results in both the design and after the install?
Craig: All of the prediction packages (as they relate to sound coverage) are limited by the accuracy of the information provided by the manufacturers. Most info is a little suspect in that until recently has all been in 10 degree increments. Need at least 5 degrees for good accuracy. Also these programs do not consistently predict interference accurately. The prediction of coverage is being complicated by the use of "shaded array" systems which have (currently) no way of being inserted in modeling programs. EASE and others are working on this.
Charles: What makes SIMM better for road use than SMAART? Or are they equal?
Craig: SIMM is extremely good at allowing you to use repeatable configurations (called branches) which switch mics on and off and reconfigure the delays. Additionally SIMM has 3 separate DSP processors which allow 3 concurrent measurements. SMAART is only 1 processor (unless you use multiple computers, which is clunky at best.)
Tucci: Could you explain your dual computer use within a SMAART measurement rig? I don't follow what you said.
Craig: Tucci, I assume that you have knowledge of SMAART?
Tucci: Yes, I do
Craig: I use one computer to measure the response. Using same computer I switch to the EQ input and reverse the trace. Thus as I adjust the response, I can't see the result. I run a second computer so that I can see the response in real time.
Chris Kathman: Have you ever seen the SpectraFoo program ?
Craig: Yes, but only briefly. Not enough to discuss it intelligently....
Jeff Waluch: The Potters House install was quite impressive, How did you come to your component decision?
Craig: Potters House is an interesting project (understatement...) because of the tremendous sound pressure levels that needed to be achieved, even with a lav mic. Basically the system is capable (and needed) of getting to around 125db at the console. To get this level, we needed really powerful and compact speakers. There are limited options for this. We chose to use the EAW KF900 series. Probably could also have done it with VDOSC.
Chris Kathman: Wally or Craig, maybe you could tell the viewers at home what Potter's House is.
Craig: Potters House is a 8200-seat church in Dallas.
Chris Kathman: Wow! How many zones/delays?
Craig: Left-center-right cluster each with 3 KF900 MH boxes and 4 (4x15" drivers) cabinets. First delay was 12 ASV7652 boxes (2x15, 2x10, 1x2") and rear delay of 16 boxes (12 and 1").
Charles: Why was there the need for 125db at the console in a church? Even allowing 10db for headroom, that's 115db average!
Craig: The pastor of this church is T.D. Jakes, who does a lot of stadium gigs and is used to concert levels. Also the crowd is so LOUD that the system has to get over them. I know it sounds crazy...but you have to be there. Of course they only hit those levels for brief moments of time.
yam4000vca: Did the client specify that 125db level number? I have done quite a few kickin’ churches and never needed that much.
Craig: The client insured that I went to one of their arena gigs and wanted me to understand that they did not want to run out of system for any level of concert that they might do. 125dB is just what the system is capable of, not what they run it at all the time.
Michael: Is Potters House the place with the 3 InnovaSons - house/mon/video?
Craig: We specified the Yamaha PM1D's for this project (3 units) but as they have not been released yet, they currently have a 64-channel Soundcraft Series 5 and a SM20 at console.
lilbob: Who supplied the equipment for you on the Potter's House install?
Craig: SPL
yamama3000: Can you explain 'beam steering' and it's advantages?
Craig: Beam steering is the technique of loudspeaker placement and signal processing implementation that allows you to control and direct the projection of sound. A simple example: Say you are on stage with side stacks of sub-bass, it is a relatively easy task to position the subs so that you achieve a null in energy projection to the center of the stage.
Michael: How does beam steering work?
Craig: It's pretty simple really. If two waves from a speaker (any frequency) coincide at the same path length, then we get 6dB of summation. If they are space apart by 1/2 a wavelength of the frequency of interest, then they cancel completely. It's using this cancellation that is tricky.
yamama3000: When you say "loudspeaker placement" are you talking about the boxes themselves or the drivers within the boxes?
Craig: If we look at the sub bass example, then spacing the subs 8 feet apart horizontally will result in at least 15 dB cancellation at 65hz at 90 degrres off axis to the palne of the subs. The wavelengths don't care if the drivers are in the same box or in different boxes. What counts is the spacing and the frequency of interest.
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?
Moderator: For those who asked, we now have 29 users in the audience.
Craig: Line arrays have of course existed for over 40 years now and are all based on the physics papers published in the early 50's. 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 VDOSC) 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 VDOSC 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 100hz in your example?
Craig: At 80 or 100Hz you will have about 6dB drop, same at around 30hz. If subs go higher, say 140Hz, 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 it's design, is extremely knowledgeable in array inferenace stuff.
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.
Craig: To reduce "power alley" we have to have horizontal directional control at LF. Difficult to do unless the array is large. Possible but complex. Also RE power alley reduction we need asymetrical horizontal pattern control of the array with LF angled off stage considerably and HF and Mids unaffected. Tricky. Steering subs is much easier by simply adding delay to the outer subs and "decorrelating" the summation down the center line.
Moderator: Would it be possible with, say, 8 boxes?
Craig: What 8 boxes? (product?)
Moderator: Any box with 2 front-loaded woofers.
Craig: Assuming 8 (dual 15" vertical placed) boxes a side horizontally placed, then you would get substantial horizontal inconsistency in LF performance. This could be mitigated by frequency shading the outer drivers but then you would lose LF output. You can test this out by down loading the EV Array Show program from the EV site. It's free and a great education.
Weogo Reed: What about simply placing all subs on one side of the stage? Get rid of power alley and have a little more volume on one side and lower on the other?
Craig: Putting subs to one side would sound pretty weird, I think. Rather steer the beam a little.
yamama3000: If subs are ground stacked you get a +3-6dB through coupling...is the 6dB drop part of this equation?
Craig: No, the 3 dB (half-space loading) does not affect the horizontal null at all. You would get the same result with the subs in the air. (Keeping in mind that the stage position would then be asymmetrical to the array null.)
Tucci: To get the subs decorrelated, how much phase change/time are you talking about? You'd want the outer subs to show up "late" at the center line. That could be a significant amount of time, no?
Craig: Time and wavelength are simply two sides of the same coin. The wavelength at 60Hz is around 16 feet, so if you added 4-6ms of delay you would get significant beam steering.
yamama3000: To the outer boxes only...correct?
Craig: Yes, the outer boxes only. Of course if you wanted to impress the guest engineer, you could align all of the time to point subs at the mix location...
Denny Strauser: What proportion of boxes must be delayed for effective steering?
Craig: Impossible to answer without more info as to the number of boxes, size of boxes, etc.
Tucci: How about doing it the inexpensive way? If 4ms is 90 degrees at 60Hz, why not just turn the outer sub at a right angle?? Clever eh?
Craig: Tucci, you jest of course....
Tucci: Yes, of course.
yamama3000: And to add to Denny's question: Will SMAART help in the equation?
Craig: SMAART will only help you to tell what the result of predictions are, not do any predictions itself. Good to know that what you tried worked, or not of course, and then SMAART is a great tool.
Weogo Reed: Going back to the all-subs-in-one-place theme, do you ever use all subs at the front of the stage?
Craig: Yes we do use subs on the floor in front of the stage. However we almost always spread them out so that we get an infinite line array, thus losing only 3dB per doubling of distance instead of 6dB.
David Gunness: I have to go to bed now (early flight), but I wanted to say "hi" and "nice job"!
Craig: Oh boy, if I knew Dave (horn dog) was on the session I would have felt much more intimidated...
yamama3000: Explain "horn dog".
Craig: You can reach Dave Gunness at EAW on horndog@eaw.com. He designs horns and other things, and is also the author of the FChart program.
Moderator: Dave Gunness will be our guest here next Monday night.
Craig: Dave has more knowledge about array "beam steering" than anyone I have ever met. I've met a lot of really good engineers.
Dale Shirk: Craig, When you roll off upper frequencies on the outer drivers of a line to shorten it, what is the affect of the phase shift (group delay) of the HPF in the passband of those drivers? Do the center drivers need wide-band delay to match?
Craig: In general the filters are pretty shallow and the delays are not too bad as long as you know what it is you are doing. If the shading is symetrical then it is easy to correct the delays.
Tucci: Would that not be a LPF, Dale?
Craig: No, Dale is right, it’s a HPF.
Weogo Reed: Cool. Do you do any shading to make coverage more even?
Craig: Yup, we shade just about all of our clusters in one way or another. This shading thing is really no great mystery really although audio gods like me try to use as many big words as possible to that people will not realize how easy it actually is.
lilbob: Do you have a favorite subwoofer in general?
Craig: The two most frustrating things in my audio life is getting great sub sounds and getting a great piano sound... I currently use a lot of the Bag End ELF subs and considering trying those in conjunction with EAW horn-loaded subs. The Bag Ends have great extended lows and the EAW's have great "punch"...
yamama3000: What do you think about the use of extended bass frequencies like the Servodrives?
Craig: I am not personally a fan of the Servodrive sound. I have friends who like it a lot though.
yamama3000: Why?
Craig: One of my personal sub tests is to hear a bass guitarist with a five string bass scale down to an open "D" string. I want to hear distinct pitch changes. My tests with Servodrive did not seem to give great definition in my opinion. I don't want to use this forum as a negative for any product though.
Michael: Why one Prism rig sound beautiful and even and another sound gak nasty? Operator error?
Craig: Lots of reasons why one show sounds different to another. Mix engineer, system engineer set up, sucky poo band (a technical term), bad acoustics.
Michael: Have you used HLA sub?
Craig: I have not used the HLA sub itself but have used the same JBL driver in similar box constructions and porting. It is a good 18" sub.
miffe: Which one of the HLA sub drivers? DCD or the older Super Vented Gap?
Craig: Older Super Vented Gap.
Denny Strauser: Are the Bag End Subs capable of doing large shows? (Indoor Arenas & Sheds)
Craig: Sure. Just remember that they are a sealed box and thus do not have the efficiency of a port. In larger arrays this becomes less of an issue, though. Ground loading helps greatly as well. The efficiency of a sealed box allows you to get a huge number of drivers in a given space. Lots of good approaches to subs.
Van Metschke: I was quite impressed with the Bag End sub you showed me in Dallas.
Craig: Hi Van! Call me tomorrow, I have an answer to your Yamaha question.
Van Metschke: I look forward to it!
Charles: On a slightly different topic, do you find yourself installing more LCR systems today than stereo systems? If so, why? Is it a specific client request or your suggestion?
Craig: We do a lot of LCR systems because many of our clients are large churches where both music (best supported by stereo) and speech (best supported by center cluster) are needed. I personally really like to mix on a true LCR system as it provides a lot more opportunity to "image" the sound and pull the lead vocal out of the mix.
yamama3000: Then the need for a LCR console or center off a matrice?
Craig: Mixing a LCR system with a LR console is a pain in the butt. I like what Midas has done with the proportional mix split approach to LCR. Allen & Heath do a similar thing on their LCR boards.
yamama3000: Vocal OUT of the mix? You mean IN, right??
Craig: Sorry - I mean the vocal jumps "out" at you.
lilbob: How do you deal with coverage issues with vocal only in a center cluster?
Craig: Each cluster must cover all of the room ...or the signal from the center must be matrixed to the outer firing cabinets of the LR clusters. The latter is the more common.
yamama3000: How much mixing do you get to do these days?
Craig: I still mix on contract once in a while. Often mix the opening event of our projects. I'm a better designer than mixer though....
lilbob: Do you spec a broader coverage array in the center?
Craig: Yup, sometimes the center coverage is a little wider. It really depends on the seating configuration and how much of a thrust stage there is.
Scott R: Where do you like reverb (on the vocal) on a LCR? C, LR, or both?
Craig: For solo vocal I like to place it in the center and pan verb to LR. Depends on song though.
lilbob: I'm confused a little about each cluster covering "all of the room" as it relates to LCR imaging. Would you perhaps have center channel cabinet(s) in the L & R clusters to complete the coverage?
Craig: A true LCR system must allow you to pan say the SAT (sop-left, alto-cent, tenor-right) you should have a stable mix balance anywhere in the room. Thus each cluster must cover most of the room. We often use cabinets within the LR clusters to feeed center signal to. These are not separate cabinets, but cabinets (usually off stage cabinet) fed with a mix of C and L (or R if right cluster).
Michael: Do you notice any difference in result with dual-coil drive speakers? Do you think speakers with two voice coils will be developed on a broader basis than at present?
Janssen: To be honest, I have not paid a lot of attention to the make up of the driver units. I work extensively with the specifications of the unit. Can't answer your question as well as I would like too...
Moderator: Craig, what are your views of the advantages/limitations of powered speakers?
Craig: Powered speakers have the great advantage of a controlled signal to the speakers. Best use is in portable applications. In permanent, it is tricky and often expensive to get power to the clusters. Also maintenance on high clusters in interesting if the amps are up there...
yamama3000: Do you agree that the quality of glues used in speaker manufacturing makes for a more reliable driver?
Craig: I ain't a glue guy. Have no idea.... All of the main manufacturers are very good at driver design and I trust that they are using the best adhesives. As to music-store grade stuff...who knows?
Angus-Young: What do you think of sonic maximizers or exciters made by BBE or etc? Do any of the big sound companies use them?
Craig: I can’t really say what everyone uses. I have not ever seen one on the main system of any touring rig... Sometimes, not very often you will see them in a rack. I personally don't like them in a well-designed rig.
Moderator: We've got time for a couple more questions.
lilbob: Thanks. Any venues asking for surround or 5.1 installs?
Craig: We often use surround sound effects speakers, but not in the formal 5:1 that you refer to. It's really up to the sound designer of the show.
Chris Kathman: I am going off-com. Thanks for the LCR explanations!
Craig: You are welcome.
Ken: I noticed in one of recent baseball stadium designs, you placed a center point-source system in center field, and 2 banks of effects speakers to the left and right. What is the exact purpose of these effects speakers?
Craig: You are referring to the Dodgers Stadium rig, I assume. We are intending to use the LR arrays (6 by MSL-4's each) for feeds from the "Click Effects" computer. Definitely not vocals or this instance music, due to limited output of the LR arrays.
lilbob: Any single piece of live gear that really impresses you?
Craig: I think that the new Yamaha PM1D is going to revolutionize the industry. I think that Peavey MediaMatrix did that last decade.
Moderator: lilbob's will be the last question of the evening.
dave: On behalf of the folks here at ProSoundWeb.com/Universal Concept, I'd like to thank you, Craig!
Craig: Great fun. Hope others enjoyed as much as I did!
dave: I'd also like to thank all of those that stopped by, as well.
Moderator: Throw microphones!
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NEXT PSW Installed Sound Live Chat: David Gunness, “Horn Dog” and Director of R & D for EAW.
9:30 pm Eastern time, Monday, Jan. 15.
ALSO: Pat Brown of Syn Aud Con is Scheduled For Live Chat
Monday, Jan. 29, beginning at 9:30 pm Eastern
(Please send questions and comments regarding PSW Installed Sound Live Chat to Keith Clark, editor, at keith@prosoundweb.com)