Hilmar Lehnert
Hilmar Lehnert is an accomplished audio professional with 35+ years of experience. He holds a Ph.D. in Acoustics, spent 8 years in Academia and held various leadership positions in the industry. Notably, Hilmar led the Acoustics and DSP teams at Bose Corporation and Sonos. He thrives at the intersection of Physics and Perception: looking deep dive into physics and Math to understand why things sound good (or not!). Currently, he works as an independent consultant and serves on the board of several startups.
He has authored 30+ conference and journal papers, holds 36+ granted patents, and has been active an musician for over 45 years
Frequency and Damping: a handy map of the Z-plane
Status: Not yet available - Stay tuned!Almost all discrete LTI systems can be represented as a rational function in the Z-domain. This rational function can be fully characterized by a gain and the roots of the polynomials, which are, of course, the poles and the zeros of that transfer function. Any real transfer function can be broken down into cascaded second order sections each with a pair of zeros and a pair of poles. The direct interpretation of these root pairs in terms of real or imaginary part or magnitude and phase or two real roots isn’t straight forward.
In this presentation we show an alternative interpretation where each root pair can be represented as the resonance frequency and the damping of a second order resonator. We’ll show how these parameters map to the Z-plane and that each point in the z-plane can be uniquely associated with a specific frequency & damping. In other words, we can answer “What is the Q of a pole” or at least a pole pair.
Finally, we’ll demonstrate how some popular filter types can be intuitively designed using this representation.
Crossover Design and Trade Offs
Status: Available NowCrossovers are heavily used in many aspects of audio signal processing. Crossover design involves a significant amount of trade offs. The presentation describes what these tradeoffs are, presents different architectures (Linkwitz Riley, odd order Butterworth, linear phase FIR, etc) derives their properties and discusses the pros and cons and how they map to typical real world requirements.
Introduction to Warped FIR Filters
Status: Available NowWarped FIR (WFIR) filters are a hybrid between FIR and IIR filters combining some of the advantages of both. Design methods are similar to FIR filters including arbitrary magnitude and phase response but in contrast to FIR filters, they offer good resolution at low frequencies at very low orders and they can be implemented efficiently. They are a particularly good fit for loudspeaker arrays as deployed in soundbars and Atmos speakers.
The talk will cover:
- mathematical fundamentals,
- design process,
- a few examples,
- common real-world issues,
- discussion pros and cons.