Community headquarters: Strange sounds emanate from this building…

An affable sort, Howden was more than happy to invite ProSoundWeb into his lair for a look and listen. The following interview offers a rare glimpse into a private world responsible for producing information vital to many within our industry.

ProSoundWeb: Sometimes the most obvious questions need answering first. That said, what is the real importance of the measurement and testing process anyway?

Dave Howden: In its most basic sense, it provides the raw data which confirms the operational capabilities of a loudspeaker or loudspeaker system. This raw data is processed and published, then distributed to consultants, end users, or anyone else who may have a use for our products.

Dave Howden in his test and measurement lair.

PSW: What is the nature and scope of the measurements you make? Dave: I measure physical properties such as dimensions and weight; and everything else you can think of including acoustic capabilities, frequency response, impedance, output level, operational limits, and pattern control if a product is used in conjunction with a horn.

All of my data is collected using a TEF 20 acoustical analyzer with a high-speed interface. Beyond the basics I just outlined, I also collect polar data on all of our single loudspeaker components and loudspeaker systems.

This data is especially useful for the computer-aided modeling of sound systems and the world of acoustical simulation, which has grown by leaps and bounds, and is becoming more accepted as the price of computer processing power drops and software becomes more user-friendly. As an example of this trend, consider that only a handful of people could operate the first versions of EASE. You had to type in every little loudspeaker spec by hand. Today it's a much more automated process, and has much higher resolution that it had in its first releases.

PSW: Does Community measure EVERY product in its catalog this way?

Dave: Yes, and we actually go beyond just measuring every product. Let me illustrate further: I have measurements for our two-inch compression driver, the M200, on every horn that can be coupled to it. I also have measurements for every horn coupled with every compatible driver that we build or OEM, and I have measurements for every single loudspeaker component by itself and as used in our various systems.

We're also getting into measuring complete arrays for consultants, as trying to accurately create an array based upon the specs of individual components is difficult at best. What you see on the screen provided by your acoustical simulation program is not quite reality. We are grabbing the torch here and making some serious headway in the publication of data on actual arrays. Now there's accurate data available out there for some of our more commonly grouped loudspeaker products, and it's making consultants' lives easier. We haven't released all of our data on arrayed products to the public yet, but we will shortly, once we know what the needs of the forthcoming version of EASE will be.

PSW: When you first came to Community, you inherited a catalog of measurements, right?

Dave: Yes, that's correct. But based upon a number of factors, we were due for some updating, and decided to re-measure the entire catalog. Basically, it was just time to do it. We had new products, improved products, better measurement tools, and a keen desire to keep pace with the new software being used by consultants, which provided them with more precision and modeling power than ever before.

PSW: In many respects, your current measurement system replicates the functions of the free field experiments conducted by Bruce Howze and John Wiggins back in '75 which produced the data in the White Catalog...

Dave: Yes, we are doing many of the same things, just on a more precise and convenient scale. Automation and modern electronics play a large role today. Rather than moving a microphone around a stationary speaker by hand using ballasts to hold everything in place, and then quickly trying to get a measurement before the wind blows everything over, we can determine precise rotation of the loudspeaker in five degree increments using a stationary mic. The original system was good for its day. What we have now reflects the new technologies available.

Precision rotation as part of the data collection process.

PSW: Beyond the TEF 20, loudspeaker rotator and all of the rest of the hardware the measurement system uses (see sidebar for a detailed overview), what are some of your other important working tools?

Dave: Test signal amplitudes are measured using three meters including Fluke 87 Series 3 and Hewlett-Packard 3468A true RMS meters, and a Ballantine 310A analog meter. Both the Fluke and HP meter are traceable to the National Institute of Standards and Technology. (see Figure 1).

Figure 1.

A B&K (Brüel & Kjær) 4007 microphone is used to collect the data, and is calibrated for every set of measurements using a B&K 4230 piston-phone. Comparisons are also made at regular intervals with a B&K 2209 SPL meter with a B&K 4165 capsule as a further check. Resistors, measured to 1/100th of an ohm using the HP 3468A meter, are utilized to maintain calibration for impedance measurements.