"This creates the best soundstage and perceived tonal balance. The distance from speaker to ear should be at least five feet less than the distance from speaker to a reflective surface to ear. The reason for the 5-foot difference is that if reflected sound arrives 5 milliseconds or more after the primary sound, the brain knows it cannot be the source (sound travels 5 feet in 5ms)... Why do we place the listening chair near the rear wall? The first reason is bass reinforcement. Maximum sound pressure occurs at the room boundaries and pressure gives a sense of deep bass. Secondly, because the reflections off the rear wall are shorter than the circumference of the head, the brain cannot measure the time delay between the ears. If it cannot measure the time delay, it cannot localize the source of sound. And when the brain cannot localize reflections, it ignores them." Your next recon stop could be this report on a visit which Holger Barske had with Joachim. Even if you don't read German, the photos tell their own story. Some of them show developmental open baffles to test the Enviee in a box-less environment.


For English speakers, a fascinating glimpse into Joachim's R&D can be found here where he openly discusses progress on the earlier Kalasan project. His first step was measuring the raw drivers from SB Acoustics as a company he consults for. "I measured impedance curves by holding the drivers with my hand. The woofer had very low mechanical losses. You could see that the peak at the fundamental resonance was sharp and narrow to translate into a high Qms. The edge resonance at 1kHz was just visible in the phase of the impedance curve as a small wrinkle. For such a low-loss driver this was very well controlled and looked better than the preliminary data sheet. I didn't care much about the small hole it might create in the response at that frequency but undamped there would be a rise in distortion too. There was a sharper discontinuity at somewhat under 4kHz. That seemed to be the cone break-up frequency and a very high frequency for a paper cone to be quite stiff. The driver should be very useful to 3kHz. The tweeter looked simply perfect with a low, symmetric and well-damped fundamental resonance. Both drivers had a very flat impedance curve so had to have some copper in their magnetic gaps. Actually this kind of low rise was a rare sight. Modulation from changing inductance over level would be very well controlled. Inductive modulation is a very nasty type of distortion which I was very happy to see eroded here." He then measured driver behaviour in a 1.2x1.2m standard baffle for amplitude response on and off axis, phase, acoustic centres and distortion. "My plan was to start with a L/R 4th-order and then work down to Butterworth 3rd and L/R second. Ultimately I could try the Bessel approach or even 1st order. In general I found that fewer parts in a passive crossover sound better when certain limits of linearity and lobing are met. About the audibility of phase distortion, a lot has being said but none is conclusive. I made my own experiments in the 90s when we constructed a DSP-based speaker at the University of Essex. We could switch between an L/R4 and its phase-linear version without changing the frequency response and lobing. "


To document just some of the measurements Joachim performs as a matter of course on any speaker design, "above are two response measurements on the Satori tweeter from the 1.2m x 1.2m baffle. The bumps in the response below 3kHz are an artifact of the baffle. It disappears in the nearfield response. The on/off-axis response was measured at 50cm, the nearfield response at 10cm. The measurements where taken at 0°, 10°, 20°, 30° and 45°."


"Here are the nearfield measurements at 0°, 15° and 45°. The second measurement is in the nearfield at 45° and 60°. The characteristic notch is highest at 45° and shifts down in frequency and depth at 60°. That's a geometric artifact where parts of the membrane reached the microphone earlier and others later from the far side."



"Here is the 2nd and 3rd harmonic distortion at medium and high volume. The high volume was rather challenging on my ears. Measurements like this are hard to interpret because a comparison can only be made when a competing tweeter is measured at the same volume and distance. This measurement was also taken in the nearfield."


"Here is a multi-tone test. 31 frequencies were spread so as to not intermodulate much with themselves. This test is also know as spectral contamination. The first test is with the driving signal, the other shows the multitones notched out to become the so-called Belcher Test." This was followed by single-tone high-volume spectrum measurements at 1.8kHz and 4kHz for THD and much more before the same family of tests got repeated for the matching woofer. Interested parties can peruse the entire DIYAudio thread for more. For our purposes this shall suffice for some behind-the-scenes glimpses into our designer's approach. It informed the Puls well before its actual box and impedance correction filter were ever designed. It began with Joachim's input during the actual driver's multi-year development process.


On May 31st he checked in. "I had a lot of visitors to my home and factory after the Munich HighEnd show so I contact you a little late. I have the pair of Puls I played in the off-site Zenith Kulturhalle during the show [right]. It is a fully functional pair with the correct sound. But it is handmade so the surface is not perfect. I could bring you this pair for listening if you wish. Series production has started but transportation of the various elements is still on the way so I expect the series version to start delivery in ca. 6 weeks. Do you want to wait for a pair of the industrial made ones or do you prefer to get a scoop on the existing ones?"


I told Joachim I was less concerned with a scoop and more with doing a proper job. Hence I opted to wait. That way I could also report on final fit'n'finish relative to what a customer would buy. Seeing how the general Puls styling is already very much in the Spendor/Harbeth vintage vein and its über-monitor dimensions, bevy of exposed screw heads, unapologetic boxiness and massive plinth slash stand are all quite the antithesis of modern, I thought an inspection of those elements mandatory. Whilst this would delay the assignment, in the bigger scheme of thing another six weeks were nothing. That Joachim's next note took until August 26th to announce final receipt of cabinets and delivery for the following week was something. But low-volume production tends to be slow. Joachim was keen to show me how to set up the Puls. Given that my room's layout predetermines width whilst front-wall distance and seat position are flexible, I doubted he'd end up with something much different than my usual. So I said that I'd surely be able to figure it out myself to not need a personal visit.


By September 24th, Reinhold Schäffer of bFly Audio contacted me about his matching stands. He said that they should be used with the review Puls loaners. He wanted to know when I'd need them. I asked him to coordinate with Joachim. With delivery times having slipped a few times already, I was completely out of the loop by now. I thought it best to let these two manufacturers time logistics on their end. This—hurray!—prompted Joachim to reappear by sudden phone call. His son would now deliver the loaners on October 1st at ca. 20:00 hours. The stands would arrive by courier a week later.