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In this episode of Sound Design Live I talk with the vice president of engineering at Fulcrum Acoustic, David Gunness. We discuss the improved gain-before-feedback with coaxial speakers, the cell phone material that helped crack the code on passive cardioid subs, and ground-stacked vs flown subwoofers.

I ask:

• “Fulcrum’s revolutionary coaxial designs allow for improved intelligibility, higher gain before feedback…” How does a coaxial design improve GBF?
• When most of us think of a directional subwoofer, we think of multiple elements arrayed together. Even when it’s a single box, like the old Meyer Sound M3D subs, there were multiple drivers in the box to create the directional result. But your cardioid subs have a single driver. How does it work?
• In The Best Place To Put Subwoofers Is… ? Jerrold Stevens writes that it’s best to ground stack your subs if the entire system is ground-stacked, but better to fly the subs if you’re flying the mains. In Comments On Half Space in the section on subwoofer deployment, you write about the height of the subs affecting the difference in path lengths between direct sound and ground bounce and the resulting comb filter. If my mains are flown and my subs are flown, then should the comb filter affect my design choices and limit the subwoofer height? Is there a maximum angle I can use relative to the listener’s perspective to remove the comb filter from the operating range of my subwoofer? Or does the improved SPL distribution with flown subs out-weigh the potential comb filter throughout the audience?
• Tell us about the biggest or maybe most painful mistake you’ve made on the job and how you recovered.
• From FB
  • Nathan Riddel: What is his process for developing the FIR presets? What type of tonal shaping EQ does he pre-bake into the presets for his speakers (if any)? What compromises do the passive-cardioid boxes have or where wouldn’t they be a good idea?
  • Bodo Felusch: What was your biggest challenge by the time you created EAW focused NT series?… and how did you solved it
  • Menno Zijlstra Fulcrum is based on Dsp. How will he see the future develop in the years to come. What can we expect?
• What’s in your work bag?

I’ve encountered people over the years who when they developed an important skill, wanted to keep it close to the vest and not let someone else figure out how to do it. But then you’re stuck doing that for the rest of your career.

Dave Gunness

Notes

1. All music in this episode by Hospitalized and JNGS.
2. The Mom Test
3. Hydrophobic: Tending to repel or fail to mix with water. The opposite of hydrophilic.
4. Workbag: RF measurement mic
5. Book: Acoustics, Acoustical Engineering
6. Quotes
   1. The biggest area of mistakes is EQing finished systems.
   2. The house curve for Fulcrum is flat through the mids.
   3. It’s not how good you can make FOH. It’s how even you can make it everywhere.
   4. It’s easy to say, this is how you make a passive cardioid, but when you try to make it work you discover the material challenges.
   5. [Sub-cardioid] is generally more useful. Even with a subwoofer sitting on the floor, if you walk around behind it, your ears are not on-axis with the cabinet. You are above it. Having more attention at 135º makes it feel like more attenuation than from an active pure cardioid.
   6. How tympanic is the stage?
   7. In sheds, [subwoofers] are on the floor and in the air. In some cases that means you overlap the subs with the response of the mains. In a line array situation, you’re extending the line all the way to the floor. That’s particularly helpful in sheds with a metal roof. Extending that line makes it long enough that you’re putting less energy into the roof, which means it’s less likely to rattle and bounce back down 80ms late.
   8. The one I don’t like is flying [subs] at the top of a line array. They’re coupled tightly but can’t have the same phase relationship as you move forward and backward in the room. It’s better if they are next to the line array.
   9. I’ve encountered people over the years who when they developed an important skill, wanted to keep it close to the vest and not let someone else figure out how to do it. But then you’re stuck doing that for the rest of your career.
   10. The things that you do to make a loudspeaker flat out of the box don’t make it sound better. You can always make it sound better if you don’t try to make it flat out of the box. You let the compression driver run flat out. That means there’s no high impedance between the amp and the compression driver, etc.