Going Dutch (& Dutch): a Conversation with Martijn Mensink

In 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.

420dutch.3

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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COMMENTS
Bogolu Haranath's picture

Audiophiles have ears like 'Yoda' ....... Normal people don't have those :-) ........

Bogolu Haranath's picture

D&D could consider making floor-standing speakers like the Eikon Audio Image1 integrated system :-) ......

Kal Rubinson's picture

Alternatively, they could make a woofer enclosure in the form of a stand that would integrate esthetically and acoustically with the 8c. :-)

Bogolu Haranath's picture

Like Kii Three + BXT ...... In that case, the woofers in the back of the cabinets of 8c would be superfluous, but they could also be used to augment the bass ....... They can also be sold separately and the previous owners of 8c could upgrade, if they wanted to ...... You (KR) could talk to those guys at D&D :-) .......

Bogolu Haranath's picture

The price of 8c + powered woofer stands should be competitive with the $25k price of Eikon Image1 system :-) ..........

Kal Rubinson's picture

...... You (KR) could talk to those guys at D&D :-) .......

I spent the better part of a day and evening talking with Martin during his visit to NYC. We talked about this and a lot of other stuff.

Bogolu Haranath's picture

Great ..... Waiting for a follow-up review ....... May be even another D&D new product review :-) .......

blang11's picture

I'm very much on board with what Dutch & Dutch is doing. Cheers to Stereophile for the continued coverage of the 8C.

Michael Fremer's picture

You realize that when you hear whiners say "the reason high end audio is drying up...." and "it's all a bunch of old men...." it's total nonsense.....

Anton's picture

I hadn't thought of it 'til you mentioned it.

Darned tootin' right!

From that pic, we can see it's only "half old men."

The 'whiners' got the "men" part dead right, though.

;-D

They share the same gender diversity as the Senate Committee for Women's Health!
https://www.google.com/url?sa=i&url=https%3A%2F%2Faction.momsrising.org%2Fsign%2Fahca_womens_health%2F&psig=AOvVaw1t145_l2YO5YPYa7LbTkA1&ust=1586646052969000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCODGrKf73ugCFQAAAAAdAAAAABAN

Not being partisan, just trying to cherchez la femme!

Bogolu Haranath's picture

They look like members of House 'Diversity and inclusion committee' :-) ........

Bogolu Haranath's picture

They look like they just received 'immunity certificates' :-) ..........

Ortofan's picture

... are:

1) Do the amplifiers built into the 8c perform as well (or better) than the Benchmark AHB2?

2) Why was aluminum chosen for the LF and MF driver cones?
Research performed by Harbeth supposedly determined that the plastic formula they developed has the most ideal properties for a loudspeaker driver cone.

Bogolu Haranath's picture
Bogolu Haranath's picture

Manufacturers like Revel, KEF and some others use aluminum, aluminum alloy and titanium metal cones ...... They measure well and also sound great :-) .......

Bogolu Haranath's picture

In most of the 'active' speakers, the amplifiers are directly connected to the drivers ....... There is no crossover in between ....... So, the distortion levels of both the drivers and the amplifiers, should be very low ...... There is no 'middle-man' crossover, interfering and making up the rules, so to speak ......... Also, the crossover itself is usually active ...... Active crossovers usually have low distortion compared to passive crossovers ...... DSP control further enhances the entire setup .........

Active DSP controlled speakers are the future, and are gonna dominate the market :-) .......

Bogolu Haranath's picture

It is amazing that, $12,500 D&D speakers can match the performance of over $60k Magico M2 ....... See, JA1's listening room measurements ........ That's what active DSP controlled speakers can do :-) ...........

Bogolu Haranath's picture

The total cost of M2 + Lamm amps + speaker cables is close to $100k :-) ........

John Atkinson's picture
Ortofan wrote:
1) Do the amplifiers built into the 8c perform as well (or better) than the Benchmark AHB2?

There isn't any way of knowing, as you can't access the amplifiers' inputs and outputs.

Ortofan wrote:
2) Why was aluminum chosen for the LF and MF driver cones? Research performed by Harbeth supposedly determined that the plastic formula they developed has the most ideal properties for a loudspeaker driver cone.

To operate as a pure piston within its intended passband, a drive-unit cone should be very stiff, as well as being lightweight. Aluminum's high stiffness pushes the cone's breakup modes sufficiently high in frequency that they will be eliminated by the crossover's low-pass filter. (Easier to write than do.)

Non-metallic cones, like paper and plastic go into breakup mode lower in frequency, and no longer behave pistonically over the entire passband required. So, to prevent the breakup modes from coloring the sound, the material needs to have high internal damping. (Again, easier to write than achieve.) This is what I understand Harbeth's statements to mean.

John Atkinson
Technical Editor, Stereophile

Ortofan's picture

... I would have liked to have heard what Martijn Mensink had to say in regard to speaker cone materials. Also, he should have been able to address the performance of the amplifiers they use.

KEF's designer, for example, opts for aluminum cones and believes that with appropriate selection of crossover frequency and slope that any cone breakup and resonance will not be a factor, whereas Harbeth's designer apparently believes that some trade-off between ultimate cone stiffness and damping is worthwhile.

I'd also like to hear Andrew Jones thoughts on the subject, given that ELAC uses different types of cone materials in their product line, including aluminum and aramid fiber. Also, Pioneer, with whom Andrew Jones was previously associated, makes some speakers with injection molded plastic cones, as does Harbeth.

Bogolu Haranath's picture

Aha ...... We found another use for recycled plastic ...... Just joking :-) ........

Bogolu Haranath's picture

Several of Class-D amps measured by Stereophile have SNR better than 110 db (19 to 20 Bits) ....... The new Purifi Class-D amp specs show close to 120 db SNR (20 Bits) ....... The amplifier performance also depends upon how much negative feedback the designer chose to use ........ Amplifier performance also depends upon what impedance the speaker driver(s) have .........

In case of active speakers, the specific amplifier performance can be optimized for the specific driver, because they are connected directly :-) .........

Ortofan's picture

1) the manner in which amplifier performance depends upon how much negative feedback the designer chose to use.

2) the manner in which amplifier performance also depends upon the impedance of the speaker driver(s).

3) the manner in which amplifier performance, in case of active speakers, can be optimized for the specific driver because they are connected directly.

Bogolu Haranath's picture

A general purpose amplifier designer chooses the negative feedback, which he/she thinks works best with many partnering loudspeakers and listener preferences ....... The distortion levels depend accordingly ........ If you look at the measurements of general purpose amplifiers, Class-D or otherwise, you can see the various distortion levels .......
General purpose amplifiers designed for the usual 8 or 4 Ohm loads, distort if 2 Ohm loads are presented, or they just shut-down .......
In case of active speakers, the individual drivers can be designed for ideal impedance and their individual partnering amplifier can be designed accordingly with proper negative feedback and impedance load :-) .........

Ortofan's picture

... some correlation exists between the value of speaker impedance and the appropriate amount of feedback to be designed into the driving amplifier?

If so, do provide further details.

Also, given that the impedance of most speakers is not a constant value, but varies over the operating frequency range, are you therefore implying that the amount of feedback designed into the driving amplifier should also not be constant across its operating frequency range?

Bogolu Haranath's picture

The usual dynamic drivers used in the active speakers present the partnering amplifier with variable impedance as the voice coil changes position in the magnetic gap ....... Since each driver is connected to one or more amplifiers, they can be considered as a single unit and can be designed more efficiently, with appropriate feedback control of the amplifiers for the connected driver and desired sound quality ........ There is no interference from the crossover network and interference from other drivers operating at different frequencies ....... Active speaker design is a better and more efficient way of doing things :-) .....

Ortofan's picture

... "appropriate" feedback control of the amplifiers for the connected driver and desired sound quality?

Bogolu Haranath's picture

No rules ...... If you want the speaker driver(s) to sound like they are being driven by tubes, use low negative feedback, meaning high output impedance of the partnering amplifier(s) :-) .......

Ortofan's picture

... having some relatively low level of negative feedback (and, thus a relatively higher output impedance) will ensure that a solid-state amp sounds like a tube amp?

If so, exactly what level of negative feedback is required to achieve that effect?

Will that effect still be audible if the speakers employ conjugate load matching?

Bogolu Haranath's picture

No .... I'm not implying that a SS amp can or will sound like a tube amp, with low negative feedback ...... It may sound less 'transistor-y' with less negative feedback ........ I don't know how that affects speakers which employ conjugate load matching ....... Do you have any examples of such speakers reviewed by Stereophile with measurements? :-) ........

Bogolu Haranath's picture

By 'cojugate load matching', do you mean, dynamic speakers with pure resistive load and no phase angles? :-) .......

Bogolu Haranath's picture

See, JA1's review of KEF Ref.207/2 speakers ........ That 207/2 model seems to be using 'conjugate load matching' in the bass frequencies ........ That speaker may not be suitable for tube amps with high output impedance, due to other reasons ........ See, JA1's comments in measurements section :-) .........

Bogolu Haranath's picture

Tube aficionados would say, 'tube sound can only be imitated, but never duplicated' :-) ........

Bogolu Haranath's picture

You may already know this ....... Wikipedia has information about 'Impedance matching' ....... There is also some information about 'conjugate load matching' in that article :-) ........

Bogolu Haranath's picture

BTW ...... Each 8c speaker has a total of 1000 watts of amplifier power ....... How much do you think D’Agostino would charge for 1000 WPC amplifier(s)? :-) ........

Bogolu Haranath's picture

You can read about both feedback as well as feed-forward designs, in Benchmark media blog ....... They explain what each technique can do ....... Benchmark uses both feedback as well as feed-forward techniques in their AHB2 and HPA4 :-) .........

Ortofan's picture

... appropriate design approach?
Using negative feedback, feed-forward - or no feedback?

Bogolu Haranath's picture

I don't know ...... Most of the amplifier designers seem to use negative feedback only .... and they choose variable output impedances of the amplifiers with variable amount of harmonic distortions ...... Benchmark chose both feedback and feed-forward techniques for their amplifiers ....... Benchmark chose to have the lowest distortion possible ........ That the reason why their products have around 20 Bit resolutions :-) .........

Bogolu Haranath's picture

JVS listens to 24 Bit music with his reference amps which have about 12 to 13 Bit resolution :-) .......

Bogolu Haranath's picture

Did you do 'water-boarding' for you know who before, Ortofan? :-) ........

Bogolu Haranath's picture

One good example of how negative feedback affects the distortion levels, see the measurements of CH Precision integrated amp ....... CH precision is one of the companies that offers user adjustable negative feedback for their power amps and integrated amps ........ Another company is Cary Audio ........ Carver also offers that adjustable controls :-) .........

Bogolu Haranath's picture

I suppose, even an active speaker designer could offer user adjustable negative feedback controls, and make the active speaker sound like it is being driven by a tube amp ...... You could talk those guys at D&D and ask them whether it is possible, Ortofan :-) ........

John Atkinson's picture
Ortofan wrote:
1) the manner in which amplifier performance depends upon how much negative feedback the designer chose to use.

The problem with negative feedback is that with a typical amplifier circuit's limited open-loop bandwidth, there is insufficient gain margin in the top audio octaves for non-linear behavior to be suppressed. A better strategy is to design a circuit that has a wide open-loop bandwidth and as fundamentally linear as it can be before feedback is applied.

And no, that isn't easy. Bob Cordell discusses this subject in the second edition of his book Designing Audio Power Amplifiers, which I review in the June issue of Stereophile.

John Atkinson
Technical Editor, Stereophile

Bogolu Haranath's picture

Does Bob Cordell advocate for 'feed forward' amplifier output, which Benchmark AHB2 uses? ....... I think the new models of Chord amplifiers are adapting that technology :-) .......

Ortofan's picture

... the "better strategy" of wide open-loop bandwidth?

Bogolu Haranath's picture

If you can come up with a way you can fit tube amps inside those 8c boxes, you could become a multi-millionaire, Ortofan :-) .......

Bogolu Haranath's picture

Graphene, an allotrope of carbon is supposed to be 200 times stronger than steel ...... It is also very light weight, lighter than paper ....... Manufacturers like Joseph Audio and Magico use Graphene cones ........ Graphene is expensive :-) .........

Bogolu Haranath's picture

Graphene is supposed to be stronger than diamond! ........ Perfectly made Graphene is supposed to handle 14 million pounds per square inch pressure before it breaks! :-) .........

Bogolu Haranath's picture

Tidal Akira ($215k, reviewed by JA1) uses diamond diaphragm tweeters and midrange drivers .... (JA1 is saving money to buy Tidal Akira) :-) .......

tonykaz's picture

$12,500 might seem a little pricy but it has it's own Amplification and Room Setup Brain.

All European, clean appearance .

Reminds me of Genelec and Meridian.

$12 Grand will buy a full Schiit & Klipsch or get a person a good running start on a PS Audio rig but it won't move the needle for the seasoned Audiophile about to spend 12 grand on a phono cartridge.

D & D is a bonafide Engineering Company, kinda like Porsche Design on a much smaller scale, I think that they belong here.

Tony in Venice

Bogolu Haranath's picture

Boris Johnson cleaned up his hair-style after he became PM :-) ........

tonykaz's picture

He rides a bike to work, I'm told.

Tony in Venice

Bogolu Haranath's picture

So, Boris Johnson is a clean European who uses clean energy :-) ..........

tonykaz's picture

Hmm, lets hope

Tony in Venice

Bogolu Haranath's picture

Boris Johnson may even ride an e-Jaguar, which uses clean battery power :-) .......

Ortofan's picture

... https://autojosh.com/new-uk-prime-minister-boris-johnson-will-use-armoured-jaguar-xj-sentinel-as-official-car/

tonykaz's picture

I'm as clean and pure as the Wind driven Snow, by comparison.

my-good

Tony in Venice

Bogolu Haranath's picture

Mr.Tony, you could talk to GM and ask them to come-up with a battery powered 'Beast' :-) .......

tonykaz's picture

rather disappointing overall.

but...

GM makes money from Service with the Cars needing regular service being the overall formula.

Cars like Tesla don't have Service Intervals, they're built to run 1,000,000 Miles, they're like Locomotives. Where's GM's profit in that?, where's the Dealer's profit?, where's the service Tech's profit?, where's the aftermarket parts profit?

By the way, Henry Ford built the FMC around the one car lasting the rest of your life concept back in Ford's early days. Ford didn't change to the 11 year durable good concept until after WW11 and Henry was dead ( 1947 ).

Henry Ford invented the Tesla concept.

Tony in Venice

Bogolu Haranath's picture

Armored Jaguar pales in comparison to the armored 'Beast' :-) ........

Anton's picture

I hear that during his off time he drives a Lotus that can turn into a submarine.

Ortofan's picture

... playing on the ICE system:

https://www.youtube.com/watch?v=BTFfW29DP24

Bogolu Haranath's picture

The PM also drives an AMC Metador coupe, which can turn into a flying machine :-) .......

Bogolu Haranath's picture

And ..... The PM used his 'Bell Rocket Belt' for his Brexit :-) ......

tonykaz's picture

but...

I hav'ta suggest that folks have a look at "The Jazz Shepherd" YouTube dailys.

Fascinating content from a fascinating person, a supporter of our "Community"

Tony in Venice

Robocop's picture

I have a query with rear firing woofers. The substrate makeup of the wall these are facing must surely have a major effect on the sound alongside the increase in db's. I guess DSP can potentially overcome this. I'm thinking particularly where one has a brick wall, concrete, concrete block, clad plaster or wood in all its variations. Even plaster board on wood supports which is what I have is not a total rigid surface and potentially with loud music is moving physically in the non supported parts. I have never played with rear firing woofers to ever consider this aspect.

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