mobanmarketIn his review of the three-way, active Dutch & Dutch 8c loudspeaker in the August 2019 issue of Stereophile, Kalman Rubinson concluded that “The D&D 8c demonstrates that active, DSP-empowered speakers are the future.” I was equally impressed by the 8c’s measured performance—a superbly flat on-axis response and an unmatched control of dispersion over the entire audioband—and asked to borrow a pair so I could experience the speakers in my own listening room.
My follow-up review was published in the magazine’s April 2020 issue, where I agreed with Kal’s praise for the 8c’s sound quality. I also explored the improvement made to its sound by using the Room Equalization Wizard app (REW) to correct for the room’s acoustic problems. As D&D co-founder Martijn Mensink (holding the 8c in the photo above) had visited me to demonstrate the use of REW with the 8cs, I took advantage of his visit to ask him not just about the loudspeaker’s design principles, but also about the company and audio in general.
John Atkinson: I hadn’t heard of Dutch & Dutch until the spring of 2019, when it exploded on to the audio scene, seemingly out of nowhere. When did Dutch & Dutch get started?
Martijn Mensink: Dutch & Dutch was started about 6 years ago, in 2014. Basically, we were five guys with different backgrounds, all related to audio. One of us was an industrial designer; one had experience with pro audio, primarily in a rental company; one of us has a background in software primarily, evolutionary programming, things like that; I have a background in hi-fi— I had had a small speaker company before D&D . . . we tried to start a company but we never actually sold a product.
We were all still in university, we put together some money, we had some ideas, we gave this money to a party that would invest in tooling and make the first products for us. After a couple of weeks we didn’t hear anything . . . to cut a long story short they went bankrupt and we lost all our money . . . [laughs] that was endeavor No.1!
Atkinson: Not an unfamiliar story. These were conventional passive loudspeakers?
Mensink: Passive yes, conventional no, because these were already cardioid speakers with a waveguide.
Atkinson: And that was where you had the idea for controlling the directivity with cardioid dispersion on the woofer and a waveguide on the tweeter?
Mensink: Yes, constant directivity.
Atkinson: In his review Kal Rubinson had written that “The engineering that has gone into the Dutch & Dutch 8c is an all-out attempt to meet the goals that all designers of high-end speakers hope to attain . . . [including] control of the dispersion of sound energy throughout the audioband.” What had given you the idea for controlling the directivity in that manner?
Mensink: We had been building speakers for a long time . . . I built my first loudspeaker when I was about 16 years old—that very first speaker was the only speaker I ever finished. I veneered it, it looked beautiful, and I sold it after about three months. I never actually finished a speaker again.
I experimented with everything. I started with traditional box speakers and chamfering the edges to reduce the effects of diffraction. I played around with driver sizes and gradually moved on to dipole speakers with electrodynamic drivers inspired by among others [Siegfried] Linkwitz. I played around with floor-to-ceiling line arrays, horn speakers—around the same time I read a lot about audio, about speaker design, I learned about Floyd Toole and his research. and that has been a big influence on me.
Atkinson: In his classic book Sound Reproduction: Loudspeakers and Rooms, Floyd was the first one to write that if you control a loudspeaker’s directivity so that the off-axis behavior is not very different from the on-axis sound, people will prefer it in blind listening tests.
Mensink: I think that Floyd Toole was perhaps not the first who thought of that but he was the one who proved that it was actually true. So yes, it’s not just the direct sound, it’s not just the power response, everything matters, and with a speaker like [the 8c] you can take that all into account.
Atkinson: Whereas almost all box speakers are omnidirectional below the midrange, my measurements showed that with its cardioid pattern the 8c’s output rolls off to the sides down to low frequencies. And that makes the interaction between the speaker and the room easier to manage?
Mensink: Correct, yes. So the tweeter works above 1250Hz, the cardioid midrange operates between 100Hz and 1250Hz—it is actually cardioid down to below 100Hz, but that’s where the woofers on the back take over. If you placed the speaker relatively close to the front wall, about 50cm [24″] or less between the back of the speaker and the wall itself, then the speaker and the wall become a single system . . .
Atkinson: The reflection is in phase with the output of the woofers?
Mensink: Exactly, you get a hemispherical radiation pattern with a directivity index that is quite close to that of a cardioid. Even in relatively large rooms you get a more or less constant directivity all the way down to the bass.
Atkinson: One thing about the 8c is that it isn’t just drive-units in a box, it’s actually a complete system with amplification but most importantly, the use of digital signal processing (DSP) to achieve your goals.
Mensink: While you can do all sorts of interesting things with DSP, we try to do as little as possible. We try to do everything you can in the acoustic domain and use the DSP as the icing on the cake, to make it even better . . . we start out with a speaker that has a relatively flat and smooth response within its intended bandwidth. So the drive-units themselves have very smooth responses and then we use the DSP to do some EQ, the crossovers, and linearize the phase response. [The 8c] uses what in my mind is the best crossover you can use , which is a Linkwitz-Riley 4th-order crossover . . . if you can then linearize the phase response you basically have an inaudible crossover.
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