Danish resident expert and loudspeaker designer Bjørn Johannesen knows a thing or two about audio. He has been involved in the do it yourself community on diyaudio and elsewhere for decades now and recently co-founded speaker company Kvart & Bølge. The company is giving rebirth to vintage designs and truly providing goose bump inducing sound. We recently had a chance to talk with Bjørn about how he got involved in loudspeaker building, the unique modeling tool he uses, and more.
HDtracks: can you tell us a little bit about how you got involved in loudspeaker building?
Bjørn Johannesen: Started in my teen years, building amplifiers and speakers. I made several speakers designed by others, and fell i love with full range designs. However, not all the speakers where doing well and I got more and more interested in how to design a loudspeaker. When I got familiar with Martin J. King’s models to simulate the predicted result, the speaker design got a boost. Gone where the days of trial and error. It ended up with three articles in the magazine AudioXpress.
HD: your TABAQ design that was the baseline platform that the Sound Sommeliers are built on caused tremendous resonance in the DIY community. Can you explain what people find so appealing about this design?
BJ: First of all the design is simple, the performance is very good and people liked my building instruction. I got the idea when several people complained about the performance of their own speakers which often where based on rather complicated designs. I got immediate good response to my design.
HD: You use a unique modeling tool based on Martin Kings Matlab system on transmission lines. Can you explain what that system does and what advantages you get from it?
BJ: Kvart&Bølge is a quarter wave / Transmission line which has been known for years. However there was a lot of misunderstanding and myth explaining TL designs. This was stopped by Martin J. King and others, who explained and documented the behaviour of a quarter wave pipe. The models for MJK can simulate any shape of enclosure and gives you a very good picture of what to expect in the final construction. MJK´s software gave me a good understanding of the effect of the various parameters in quarter wave / TL design: Type of driver, tuning frequency, volume of the enclosure, shape of the enclosure, placement of the driver, density and distribution of the stuffing and so on.
HD: How close are the modeled results to the reality?
BJ: The predicted result is very close to real life. MJK has documented this, and this is also my own experience. The final fine tuning is the stuffing. There will, of course be differences. The simulation is in an anchoretic environment.
HD: At our sister company Chesky Records their particular interest is to make binaural recordings that provide a very precise and immersive three dimensional Stereo Imaging. All the reviews we read about your speakers pick up on an attribute of being particularly expansive and precise. Can you explain the underlying technological considerations that make your design so successful in this area? BJ: Using only one driver gives you a single source of the sound. The enclosure itself, designed by Arved Deecke reduces external and internal reflections. The quality of the drives is also a part of it.
HD: We find it surprising that a loudspeaker so small can reproduce such large a frequency range and employ no electronics that may distort the sound. Can you explain how a quarter wave compares to a more standard bass reflex or sealed design and how it is accomplished to produce neutral uncolored basses that are completely congruent to the overtones that come with any musical instrument?
BJ: I have tuned the pipe rather aggressively, far lower than the Fs of the driver. Normally this is “no good”. However, I found is works well with drivers having the right properties. The output from the port is in phase with the sound from the driver and contributes to the bass. The result is a sound you would not expect from such a small driver. Compared to a closed box with the same volume, you have more bass. Bass reflex is not my favourite. A badly design bass reflex has an dominating one tone bass and noise caused by air turbulence in the port. Even without this problems, the cone of the driver is uncontrolled below the tuning frequency making noise and could damage the driver. TL is also an open enclosure, but there is stuffing between the driver and the opening. This dampen the movements of the cone below tuning and is also controlling the level of the bass. The result is a clean low end that is not dominating. The come movement is very well controlled in a sealed box at the cost of bass performance. My personal preference would be a sealed box over bass reflex. My favourite is of course quarter wave / TL. Not only because of the sound, but because it is a challenge to design them with all the parameters you can play with.
For more information on Kvart & Bølge visit www.kvart-bolge.com and our friend Steve Guttenberg’s in depth review on CNET.
Gilbert Hetherwick worked for over thirty years in the classical music business doing various jobs for PolyGram Classics, Telarc, Angel/EMI, Sony Classical, BMG Classics, and finally as President of Sony/BMG Masterworks before the whole business came crashing down around him in 2006. Or as he likes to say… “I rode the business down like Slim Pickens on the bomb!” He is also a songwriter and guitarist and works with a variety of artists and companies at his Grouse House Studio near Woodstock New York. www.GROUSE-HOUSE.com