Live Interview

ProSoundWeb Live Chat With Dale Alexander about DSP.


The following is a transcript from Dale is recognized as an expert in his field. That is demonstrated in this question and answer discussion below.

Moderator: Welcome to PSW Church Talk, and welcome Dale.

Dale Alexander: Thank you, Gary.

Moderator: Dale, please give us your professional background.

Dale Alexander: I am a Senior Consultant with Acoustic Dimensions in Dallas, and I have a BSEE degree from Oklahoma State University. Married for almost 30 years with two great kids. I’ve been at Acoustic Dimensions for over 6 yrs and have had a great time.

Tim: BSEE?

Dale Alexander: Bachelor of Science in Electrical Engineering.

yam4000vca: Not much touring, I see 🙂

Dale Alexander: No, not much touring, however I did own my own small sound company in a small southeast New Mexico town for most of the ‘80s.

Jack: What are some of the more interesting projects, from a DSP standpoint, that you’ve worked on lately?

Dale Alexander: As with most consultants, the more interesting projects involve (Peavey) MediaMatrix. We’ve done several large church jobs with LCR (left-center-right) systems that require the power of MediaMatrix.

CharlieH: What are your primary functions at Acoustic Dimensions?

Dale Alexander: I am a system designer and project manager.

Bill: What kind of DSP chips work best in audio applications?

Dale Alexander: One of the more interesting jobs I have designed recently was a custom (EAW) KF900 system in a 5000-seat church in Austin, TX. I personally like the Shaark chip from Analog Devices. However, any quality chip with floating point capability is going to work OK for almost any sound application.

Tim: Which provides the most power?

Dale Alexander: The Shaark and the new Motorola chip are both very powerful. Several manufacturers are using both of them. I think QSC uses the Motorola and White and Symetrix are using the Shaark.

GW: How do you chooses a DSP box for an application?

Dale Alexander: That is a very good question. First, we evaluate the needs of the client/job and decide what kind of system is required. Then we decide on the type of DSP platform is required to achieve the specified goals.

John: Have you used products like Crown’s IQ DSP card that plug into the back of their amps? And, why or why not?

Dale Alexander: At AD (Acoustic Dimensions), we have used most of the devices out there and have developed opinions that we would rather keep to ourselves. However, I will say that the software to program and access the DSP is very important and has to function flawlessly.

EDDY: What are some common-sense DSP boxes for medium to smaller church applications?

Dale Alexander: In my opinion the best bang for the buck in DSP today is the White Paramedic 26. The XTA DP226 is also a good unit but more expensive than the White unit.

CharlieH: What is your preferred method for setting gain structure through a DSP-based unit?

Dale Alexander: Good Question! I prefer to set the gain structure of a system so that everything goes into clip at the same time. This means that I usually set the DSP to unity, which works OK for most of the DSP units out there but sometimes you may have to do some fine-tuning.

Dale (continued): For this I like to run a tone into the units and set them just below clip on the input. Over the years we have found that gain structure through DSP devices is usually not a problem.

Bryant: So way back when you got your BSEE, did you think you would have to know as much about software and programming as you do?

Dale Alexander: Actually, I was a late bloomer, I started college when I was 36 years old and graduated in 1994 at the age of 42.

yam4000vca: Do you mean real clip or when a light comes on?

Dale Alexander: I mean real clip. The limiting part of the DSP device is the ability of the A-D converter to handle the incoming signal.

Bill M: Do you foresee a time, sooner or later, when dedicated audio-only DSP boxes go away, replaced by some form of off-the-shelf PC or whatever?

Dale Alexander: I haven’t really thought about it much. We are seeing some amazing stuff that manufacturers are working and I think it is going to get more cost effective, and have a much more open platform. Very similar to the MediaMatrix platform.

Dale (continued): By the way, everybody in the crowd needs to applaud the guys at Peak for what they have done to help this emerging technology.

CharlieH: To prevent the A/D converter from overflow, do you ever put an analog limiter in front of it?

Dale Alexander: Always!!! As a matter of fact, we have convinced White to make an analog comp/limiter as a option on their new 37 & 48 devices.

yam4000vca: I have been displeased with EAW KF750 boxes in touring situations. Have you used these in any installs and what have you done to tame them a bit? Any magical suggestions?

Dale Alexander: The EAW KF750 and KF850 boxes are definitely designed to get loud. However we do not use them in permanent install situations. We prefer to use the MQ Series boxes, they sound much better. They also do require a little work to make them sound really good but, in my opinion, they sound better than the KF series boxes in general. As to how to tame them, be cautious around 2.5Khz.

Jeff: Where do you put the DSP in the audio chain?

Dale Alexander: Immediately ahead of the power amplifiers. Usually, the signal comes from the console to the analog comp/limiter, then to the DSP and then to the amps.

yam4000vca: As a consultant do you at all stress the need for qualified operators after the install or do you just deal with the hardware and software to make it do what it should?

Dale Alexander: As a consultant who has done a lot of mixing in high power worship situations, I prefer to set the DSP using all the tools I have available to me and lock the DSP away. If a system is properly set up and EQ’d, there is no reason for the mix engineer to need to “sweeten” the EQ.

Marc: How much control to the end user? Complete lock out?

Dale Alexander: Typically, we do a complete lockout for the first year for warranty reasons, to protect the contractor and the client. After that time, if clients want to change things, they do so at their own risk. It is our experience that most churches do not have the technical expertise or the equipment to properly EQ a system.

Tim: Have you ever had an end user where you left it open?

Dale Alexander: Not for the first year. At least not on purpose. yam4000vca: This is an interesting concept to me. Are you saying that in a contemporary music service there is no need for a person to provide a “mix” if the system is tuned properly?

Dale Alexander: No, what I am saying is that there is no reason for the mix engineer to need to re-EQ the system on a week-to-week or service-by-service basis. The mix engineer, whom I call the “Mix Musician” in the church, has a great deal of responsibility to provide an excellent mix. It is just that he/she doesn’t need to EQ the system.

yam4000vca: I see. Do you make changes available for room usage and type of service, such as a different setting that can be accessed?

Dale Alexander: Yes, if required, we will program in preset memory settings that the owner can recall at a moment’s notice to change the configuration of the system or even mute different aspects of the system.

Sobe: Do you know of good DSP-oriented educational programs out there for those of us wanting to learn the basic concepts of DSP?

Dale Alexander: Are you talking about the machine level programming of the DSP, or are you talking about using the DSP in a pro sound application?

Sobe: Pro sound application.

Dale Alexander: The best way to learn about how to use the DSP in a specific application is to download the software and play around with it in a “virtual” unit mode. However, you must understand basic sound system physics to know, what to do with the crossovers, gain, time delay & filters.

Ellen: What about machine level programming?

Dale Alexander: You would need to go to a good college to learn assembler or machine language programming. I guess there is some people who have taught themselves how to do this but I don’t know of any. At OSU there were many different courses on machine level programming. I opted to specialize in other areas of EE.

Marc: Have your checked out (BSS) Soundweb versus MediaMatrix. If so, can you contrast them, specifically?

Dale Alexander: Without being disparaging to any manufacturer, I will say that we much prefer the MediaMatrix, primarily because of the software.

Marc: What about horsepower?

Dale Alexander: The more the better. At the present MediaMatrix is hard to beat on horsepower. If you have a large system as you can add DSP cards as required. However, in the single box DSP’s, the most horsepower is found in the White PM Series boxes.

Bob: How many webs have you networked together? And have you used MediaMatrix CABS?

Dale Alexander: We don’t use the Soundweb much, and most of our systems are large single-venue systems so we have not had the need to use the CABS. Even on the large stadium projects we have used fiber and the QSC control system.

Bob: Have you ever networked audio over Cat 5, like CobraNet?

Dale Alexander: Yes, with the QSC QSControl system.

CharlieH: What equipment do you use to tune a system & set-up the DSP?

Dale Alexander: We started out years ago using the TEF20 and were one of the beta sites for Smaart. So we have been pretty much a Smaart house for the last few years.

JH: What else do you use to set a system?

Dale Alexander: With Smaart you really don’t need much of anything else, except an Ivie IE30 for balancing the system.

JH: Scope?

Dale Alexander: Yes, when we have a distribution amplifier or some similar device that requires gain stage setting, we will use a scope and signal generator.

CharlieH: Please elaborate on balancing the system with the IE30.

Dale Alexander: Once the loudspeakers have been properly EQ’d, we go around the room with pink noise through the system and set the amplifiers so that the volume levels in all the seats are within 1-2dB. We will typically start with the individual clusters and then integrate all the speakers to make sure there is even loudness throughout the room.

Steve: What about interference?

Dale Alexander: There will always be interference if you have more than one loudspeaker. The trick is to aim the interference to the areas where people are not, and to try to minimize it where the people are. This is why the test results put out by the manufacturers is so important.

Dale (continued): If a loudspeaker doesn’t perform like the manufacturer says it will, we tend to shy away from them. There are a few out there who do this. No, I won’t say who. Steve: Do you go for coverage over interference? Where and how do you compromise? What gives first?

Dale Alexander: I try to get the maximum coverage with the least amount of interference. When music or speech is played over the loudspeaker system it is usually very difficult to hear the interference because it is so random.

Dale (continued): If you are listening with pink noise playing, you can usually hear interference of some frequency just about everywhere in the room. So I tend to put more emphasis on coverage.

GZ: What is acceptable coverage? +/- 2dB?

Dale Alexander: It really depends on the program and the room. But generally, yes, +/-2db is what we strive for.

yam4000vca: Have you gone the next step in some of your installs and used a digital console? If so, what types seem to work the best for this type of application?

Dale Alexander: Yes, we recently specified three Yamaha digital consoles, the PM1D, for the Potter’s House in Dallas. I am currently specifying the Innova-Son compact for a Methodist Church in Plano, TX. I really like the user interface of the Innova-Son but the Yamaha is more powerful and flexible. We have been specifying the Yamaha 01’s & 02R’s for years as sub-mixers

JM: We hear about beam steering and etc., accomplished in the DSP realm. How much of this is really true? Can you really “steer” a beam with DSP?

Dale Alexander: It depends on the loudspeaker. If you are using the EAW TD Series low-frequency line arrays in the active mode, yes, you can steer the beam using the DSP and gain controls.

kevin: What are the biggest advantages of a digital console? As a worship tech director, what would be the advantages, what would make my life easier if we were to go with a digital console?

Dale Alexander: The biggest requirement would be multiple services of differing programs. This would require multiple setups and EQ settings on the console and make the digital console very attractive.

JM: How easy is operation on a digital console?

Dale Alexander: It is different with each console. Every console, either analog or digital, will require some learning curve. I have found that the Innova-Son is the easiest to learn.

Curtis: Have you run across a good DSP solution for those of us with smaller budgets and smaller tastes/needs?

Dale Alexander: Absolutely, the QSC DSP-3. It attaches on the back of the PL & CX amplifiers, uses very open architecture, and is powerful for its size. Also, the White PM2600 is typically selling for around $1,700 and gives you two “ins” and six “outs” with enough DSP that I have never been able to use it all, and I’ve gotten pretty silly with some of the post crossover EQing.

Jeffro: What about the Rane unit?

Dale Alexander: I will say this only because I said it to Steve Macatee the other night. The Rane RPM is a box waiting for a DSP. Once you set the crossovers, you only get two filters per output, and are only left with two filters on the input. That’s not enough and Rane knows it.

Marc: Interesting that certain manufacturer names come up – what do you value most in your relationships with manufacturers?

Dale Alexander: Whether they make equipment that solves the problems we run into. We are not beholden to any manufacturer and the ones I have talked about here have proven themselves to be problem solvers.

CharlieH: What sort of loudspeaker protection, if any, do you program into the DSP units you use?

Dale Alexander: I don’t ever use the on-board limiters in the DSP units. If you set the gain structure of the system properly and limit the input to the DSP, you will not blow up loudspeakers.

Bill: Have you ever had a DSP “wig out” and blow stuff up?

Dale Alexander: Yes, we have a very high profile project here in the DFW area where MediaMatrix wigged out and blew up several loudspeakers. The manufacturer stood behind his product and made it good.

Bill: Is wigging out just a fact of life or can you protect yourself?

Dale Alexander: It is really a fact of life. Typically you lose HF devices because when the DSP goes, it usually sends low-frequency and/or dc to the high-frequency drivers.

yam4000vca: What kind of redundancy do you incorporate in the design, if any?

Dale Alexander: It depends on the system and the budget. In all of the MediaMatrix jobs, we always specify the main units with redundant power supplies and hard drives. In the smaller jobs it just isn’t feasible most of the time.

GZ: What is the most reliable DSP box, in your humble opinion?

Dale With the units that are on the market today, I would have to say the XTA DP series and the White PMs.

Bob: What else makes the White special?

Dale Alexander: White has proven to be a company that listens to the consulting and contracting crowd and then provides solutions to the problems that we encounter. They were very late in getting into the DSP game but when they did, they were the first to use the Shaark chip. They also are installing RS-485 communications protocol in the new units so that you can remotely communicate/program multiple units a time.

Marc: Back to steering… did you steer that KF900 rig in Austin?

Dale Alexander: Yes, we are doing some steering with the system in Austin using MediaMatrix. We also designed a very similar system that does beam steering in the Potter’s House. It is very effective when you are trying to keep low-frequencies and low-mid-frequencies off the platform, allowing the system to have the maximum gain before feedback.

Marc: How “low” can you steer? 110hz?

Dale Alexander: The lowest frequency you can steer is really determined by the distance between the drivers. Remember, we are talking about where we are going to aim a lobe and that all loudspeakers exhibit some lobing.

Marc: How low on the EAW TD Series box? (By the way, did you collaborate on the design of that box?)

Dale Alexander: I did not design the box, Craig Janssen (our illustrious leader) designed that box. The TD415 exhibits pattern control down to about 40Hz. The TD412 is a little smaller and controls down to about 60Hz. Remember, we are talking about some pretty interesting physics and the interaction between multiple devices using dipole principals.

Rem: Analog… analog… will there still be a place in the world for analog processing in the (foreseeable) future?

Dale Alexander: No, I don’t think so. As A-D converters get better, faster and quieter, I think you will see analog EQ’s die a slow death. There is just too much power in the digital (z domain) world.

Rem: Doesn’t analog sound “better”, more natural?

Dale Alexander: That used to be the case in the early days of DSP. However, the advent of more power feedback loops, introduced into the algorithms, help give us the natural sound. I will admit that a good-quality loudspeaker with no EQ and a good quality power amp are hard to beat for natural sound.

Moderator: Final question. Favorite speaker….favorite amp…favorite DSP…favorite project…favorite person…

Dale Alexander: Favorite Speaker, higher price: EAW MQ2364, with TD415.

Dale Alexander: Medium price: Frazier CAT Series.

Dale Alexander: Favorite Amplifier: QSC PowerLite and CX (same technology).

Dale Alexander: Favorite DSP: I think everybody knows by now that on the upper end is the MediaMatrix and on the single box scene is the White PMs. However, look out for Symetrix and QSC.

Dale Alexander: Favorite Project : A small (1,500 seats) church in south Dallas called Concord Missionary Baptist Church. I designed an LCR system that I think is the best I have ever done.

Dale Alexander: Favorite Person: Now don’t throw stones at me, but it has to be Rush Limbaugh.

Moderator: Thanks Dale! See you all next Tuesday at 9:30 pm EDT as Tim Hamilton talks favorite gear!

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