PURIFI ApS, Lars Risbo A Symphony in 4 Movements Prolog I recently gave an invited keynote at the AES convention, "Unreasonable Audio Innovation." We posted it on our web for you to enjoy. The writing process made me reflect on the state of our indu... Sep 17, 2026 0 1179
PURIFI ApS, Claus Neesgaard Building Purifi: From a Cold Office in "Siberia" to Powering the World's Best Audio Purifi builds the amplifier and transducer technology inside some of the best-sounding products in high-end audio — NAD, T+A, Lyngdorf, and Kii Audio all run on our engineering. Last week, we hosted D... Sep 11, 2026 0 1138
PURIFI ApS, Lars Risbo Unreasonable Audio Innovation 1. OPENING Good afternoon. I am told this room has some acoustic challenges. Consider that a live demonstration of one of my central arguments. A few years ago we received a review of one of our produ... Jun 1, 2026 0 8946
PURIFI ApS, Lars Risbo What is the Baffle Step? Introduction You are perhaps familiar with the terms baffle step and box diffraction. But what is this exactly? The short story is that a driver mounted on a box will radiate sound uniformly in all di... Mar 25, 2026 0 10281
PURIFI ApS, Bruno Putzeys Discrete Op Amps: When and Why It Actually Matters “Discrete is an old audiophile hobby horse,” said Lars. “It proves nothing. Consider writing a few words.” Yes, precisely. Doing things discretely has no inherent value. The normal procedure is that y... Eigentakt Jun 24, 2025 0 11833
PURIFI ApS, Lars Risbo The PURIFI Tweeter Project - Part 2 Introduction In Part 1 we learned why we chose touse a hard dome as the radiator: the dome simply yields the best dispersion for a given size. A further advantage of a dome is that has high geometric ... Jan 31, 2025 0 14515
PURIFI ApS, Lars Risbo Side effects of Passive Crossover Filters Introduction We use crossover filters to partition the frequency bands between drivers in a multiway speaker. In addition, the crossover filter may provide EQ such as baffle-step compensation. A passi... Ushindi Oct 8, 2024 0 16027 App Notes
PURIFI ApS, Lars Risbo The PURIFI Tweeter Project - Part 1 Introduction The tweeter project has been an intensive R&D effort for the last 3 years. Yes, we know, the long waiting time until it is released is painful for all of us. Since we are getting closer, ... Ushindi May 24, 2024 0 22537
PURIFI ApS, Lars Risbo Time/Phase Alignment, Acoustic Center, Lobing etc. Introduction There is widespread confusion regarding the terms phase and time-alignment of loudspeakers. Moreover, the fundamental concepts of latency, delay, phase-delay and group delay are often con... Ushindi Sep 22, 2023 0 31386
PURIFI ApS, Lars Risbo SPK16 Reference Design Note: SPK16 is now released as a kit with build description SPK16 is a passive 2 way speaker system with a 6.5X-NAA alu cone woofer assisted by two passive radiators on the sides of the box combined w... Ushindi May 9, 2023 0 57188
PURIFI ApS Low Distortion Filter for PTT6.5X04-NAA In the following, we show that not all methods of equalization are created equal. In particular, using a series notch reduces distortion, which does not happen with alternative methods. The proposed circuit results in an extremely clean low-pass response combined with low distortion... Ushindi Nov 17, 2022 0 24064 App Notes
PURIFI ApS Some Speaker Problems That Needed Solving Some time ago we posted on our website a pair of sound demos that we thought were quite instructive. One showed that Doppler distortion was much less audible than an equivalent amount of amplitude modulation, thereby sinking a lot of “masking theory” based audio discourse... Ushindi Oct 14, 2021 0 12362
