Dutch & Dutch 8c Review

[thewas]

MEG for example claims to use passive acoustic elements for their rear cardioid slots that lower the sound velocity to achieve the desired phase difference at the wanted frequency range for the cardioid pattern.

 

[ctrl]

If there's a resonance effect even though the wall thickness is negligible compared to the slot's area (unlike your example) and with the heavy damping necessary to get said phase rotation restricting air flow, I doubt it's strong or wanted.

Surely this is most unlikely?
I can't see any reason why a Helmholz resonator would be wanted in that location, and it certainly wouldn't do what is required to produce a cardioid response if it was.

No.

Okay, if this is so, then why does the simulation for the slot frequency response show the typical low-pass behavior of a Helmholtz resonator? Just like the impedance response (in attenuated form).

I would say that even with damping material, the effect shown in the simulation cannot be suppressed.

Is the effect undesirable or does it not exist in your eyes? The resonance at 200Hz can't be a cabinet resonance, since it was only 0.28 x 0.25 x 0.1 m in the simulation.

If no Helmholtz resonator is involved, then the 8C should not show a typical delayed resonator decay (with possible harmonics) in the 200-400Hz range.
Possible cabinet resonances of the midrange cabinet should be significantly higher in frequency, due to the small dimensions.

@hardisj
With Klippel data, can a single impulse response be exported as a 16-bit .wav file, for example?
Then one could have a closer look at the decay behavior.

Don't You Think If I were Wrong, I'd Know it? - Sheldon Cooper

 

[hardisj]

@hardisj
With Klippel data, can a single impulse response be exported as a 16-bit .wav file, for example?
Then one could have a closer look at the decay behavior.

Well, thanks to my chat with Christian, I know it can be done. I don't know how yet. I could export it as a text file but don't know how to export it as a .wav just yet. I'll try to remember to ask Christian how to do that.


See around this time stamp:

 

[ctrl]

I think this is getting a bit off the rails here WRT distortion.

It is without question an outstanding speaker and comes pretty close to being the perfect speaker.

However, even with a speaker that costs $ 12500 a pair, one should clearly name qualitative weak points.
You have even measured $90 shelf speakers, Neumi BS5, that partly show better THD in the frequency range 50-500Hz than the 8C.

 

[q3cpma]

Okay, if this is so, then why does the simulation for the slot frequency response show the typical low-pass behavior of a Helmholtz resonator? Just like the impedance response (in attenuated form).

I'd say that's because you made a (small) port. Try to make the slot 3~4 times larger.

 

[hardisj]

It is without question an outstanding speaker and comes pretty close to being the perfect speaker.

However, even with a speaker that costs $ 12500 a pair, one should clearly name qualitative weak points.
You have even measured $90 shelf speakers, Neumi BS5, that partly show better THD in the frequency range 50-500Hz than the 8C.

I don't disagree. It measures high and that's troubling, for sure. I can only relate my experience as to how it relates to listening.

As far as the reasons for it, someone already linked where Martijn eluded to this being a "trade off":

Now on to distortion. The 8c is a relatively compact full-range loudspeaker that offers low distortion at normal and somewhat elevated listening levels. At high levels distortion can become audible on some program material. This is the price we choose to pay for a cardioid radiation pattern in a speaker this size. However, 96 dB at one meter at a single frequency from a single speaker is very loud. In practice, in rooms with some reflections a pair of 8c’s can be played quite loudly and they do actually sound clean at quite high levels. But if you’re into very loud music, they certainly have their limits.

Source: https://www.audiosciencereview.com/forum/index.php?threads/soundstage’s-review-of-dutch-dutch’s-8c.7308/post-173726

Essentially the take-away is what others have said: that the reduced SPL from it being cardioid is one factor of the increased distortion profile. But, the choice was made that it was less important than the cardioid pattern itself. Based on my hearing, I'd agree. I'm not noticing any issues with distortion. Moreso, I'm not hearing any actual mechanical issues (which is always most noticeable in my other reviews). I never knew the distortion was high until I measured it. It wasn't an audible detriment. So, I'd say the trade-off was one for the better. Again, YMMV. Just relaying my experience having "lived with" them for a few months now.

 

[Ericglo]

I was going to resist commenting until you did the youtube review.

I noticed that you have modified the boom with copper tubing and something else. I am still waiting for Frank Dernie to design you a proper F1 performance boom.

As for the speaker, this is one of the few times I have thought about reaching for my credit card after reading a review. I love seeing new products that do something different and unique.

 

[Dialectic]

I was going to resist commenting until you did the youtube review.

I noticed that you have modified the boom with copper tubing and something else. I am still waiting for Frank Dernie to design you a proper F1 performance boom.

As for the speaker, this is one of the few times I have thought about reaching for my credit card after reading a review. I love seeing new products that do something different and unique.

Take the plunge.

One of the only three audio purchases I've made that I have not regretted in some way (the others being the Sennheiser HD600 and BACCH4Mac)...

 

[hardisj]

I was going to resist commenting until you did the youtube review.

I noticed that you have modified the boom with copper tubing and something else. I am still waiting for Frank Dernie to design you a proper F1 performance boom.

Yep. I made a video about it and have some discussion here. Make no mistake, the stock boom is an issue if your goal is to provide the highest of accuracy reviews. I also mentioned that I don't see this as an "oversight" on Klippel's part. They knew what they were doing and they are aware of the influence of the boom. In fact, I had a conversation with Christian about this before I made the below video. One can use an IEC mic or an XLR mic (or other types) so what they provide is pretty standard. I think that if I were to ask for a hollowed out tube entirely they would have been happy to provide that instead of the boom threaded for the mic adapter.

Link to thread with discussion:
https://www.audiosciencereview.com/...o-corner-gets-a-klippel-nfs.19445/post-671926


Video:

This was Klippel's response to my video:

Thanks to Erin for the video and thanks to all the people who are watching and commenting his videos. Here are some answers to the questions about the microphone mount and the safety cage:

As Erin explained in the video, the cage around the microphone is for safety reasons during measurement setup and during the measurement. As the manufacturer we have to make sure that the user cannot simply damage his expensive measurement microphone or the even more expensive DUT by automatically moving the microphone into the DUT. Additionally most customers are using the NFS for measurements during the development of a loudspeaker where the frequency ripple at higher frequencies is not that important because it's known and it stays the same for the comparison of different speakers / development stages. However, you can of course unmount this cage for the final "datasheet measurement" if you are sure that the hardware setup and measurement grid is correct.

Regarding the microphone mount: We know the influence of the relatively big ball joint very well and we are already in progress of finding a smaller microphone mounting solution. But in any case we need the flexibility of the angled microphone mount for our customers and we want to use standard components for this purpose as well. If one really wants to go into details, he could also complain about the different frequency response of the microphone depending on it's position in the measurement grid (due to the directivity of the mic). Therefor it's useful to angle the microphone by 90° in front of the DUT so that the angle of the microphone to the DUT is always the same over the whole grid. This would not be possible with a straight mount of the microphone.

Anyway, we really appreciate the thoughts and questions from this community. We will keep this in mind for future improvements or a small Tech Note

 

[Pritaudio]

It seems as if the amps being to a certain standard are the only definitive specification.
there is damping factor, and then it’s all of the rest of the components.
an algorithm for developing the rest not needing a supercomputer to compute feasible designs.

 

[dc655321]

Okay, if this is so, then why does the simulation for the slot frequency response show the typical low-pass behavior of a Helmholtz resonator? Just like the impedance response (in attenuated form).
View attachment 116823 View attachment 116824
I would say that even with damping material, the effect shown in the simulation cannot be suppressed.

Is the effect undesirable or does it not exist in your eyes? The resonance at 200Hz can't be a cabinet resonance, since it was only 0.28 x 0.25 x 0.1 m in the simulation.

If no Helmholtz resonator is involved, then the 8C should not show a typical delayed resonator decay (with possible harmonics) in the 200-400Hz range.
Possible cabinet resonances of the midrange cabinet should be significantly higher in frequency, due to the small dimensions.

@hardisj
With Klippel data, can a single impulse response be exported as a 16-bit .wav file, for example?
Then one could have a closer look at the decay behavior.

Don't You Think If I were Wrong, I'd Know it? - Sheldon Cooper

I cannot comment on your simulation, beyond saying I'm sure it demonstrates the effects you set out to simulate ;-)

I concede there are some similarities to Helmholtz resonator behaviour (loss of loading), but...
Here is now I think about this speaker's design (and I'm happy to be wrong!):

Think about a driver suspended in free air, no enclosure. The radiation pattern is dipolar, and there is no restorative force provided by the enclosure, so no acoustic loading. That spl loss could be overcome by more displacement: increase driver size or increase cone travel (or both). One can't increase the driver size on demand, so pushing the cone further is the only knob remaining. At some point distortion rises sharply when the driver is pushed into non-linear regions...

I still think the 8c is an incredibly elegant design

 

[ctrl]

I'd say that's because you made a port. Try to make the slot 3~4 times larger.

Okay, I made the slot five times as big.


Even if I make the slot ten times larger (last image slot SPL), the resonance remains. But the low-pass behavior has decreased significantly.
The influence of the resonance should therefore be kept as low as possible. With appropriate damping, this can certainly still be somewhat suppressed or "smudged".

A Helmholtz resonance is still present, but is undesirable?

 

[Ericglo]

Yep. I made a video about it and have some discussion here. Make no mistake, the stock boom is an issue if your goal is to provide the highest of accuracy reviews. I also mentioned that I don't see this as an "oversight" on Klippel's part. They knew what they were doing and they are aware of the influence of the boom. In fact, I had a conversation with Christian about this before I made the below video. One can use an IEC mic or an XLR mic (or other types) so what they provide is pretty standard. I think that if I were to ask for a hollowed out tube entirely they would have been happy to provide that instead of the boom threaded for the mic adapter.

Link to thread with discussion:
https://www.audiosciencereview.com/...o-corner-gets-a-klippel-nfs.19445/post-671926


Video:


This was Klippel's response to my video:

I am aware of the thread and video. I just noticed the updated copper tube.

 

[dc655321]

Okay, I made the slot five times as big.
View attachment 116833 View attachment 116836 View attachment 116835 View attachment 116845

Even if I make the slot ten times larger (last image slot SPL), the resonance remains. But the low-pass behavior has decreased significantly.
The influence of the resonance should therefore be kept as low as possible. With appropriate damping, this can certainly still be somewhat suppressed or "smudged".

A Helmholtz resonance is still present, but is undesirable?

FYI slot area should be approximately Sd of driver (~220cm^2 for 8").

 

[Ericglo]

Take the plunge.

One of the only three audio purchases I've made that I have not regretted in some way (the others being the Sennheiser HD600 and BACCH4Mac)...

I admit it is tempting. For you, it sounds like when I bought my Mercedes E diesel. The best car I ever bought and was something I looked forward to using.

 

[Purité Audio]

A dealer ‘should’ bring a pair to your place, set them up, acoustically measure discuss any adjustments, implement re-measure etc and then leave you to compare against your current system, if you are not physically near any D&D representative, contact Martijn directly, 8Cs can be optimised really successfully remotely.
Keith

 

[Lorenzo74]

• This speaker sounds phenomenal.
• Objectively speaking, the data indicates this is a terrific speaker. It is roughly ±1.5dB from 30Hz to 18kHz. That’s incredible.
• Speaking of distortion, I didn’t have any complaints even at much higher than typical listening levels (>100dB at 4 meters).
• The soundstage is something to behold.--- Crazy.
• The tonality of the speaker is great.
• 105dB full range at 4 meters is very loud.
• If you have the means and are considering this speaker, I recommend it.

---------

@hardisj Just Amazing Review of Amazing speaker.
Just Edit because my Irony was not fully captured by someone...: Even if M.Mensink would provide you a huge (90%?) discount to reward for the incredible and objective review you just publish, pls do not accept!! Pay the msrp or return both speakers...
Maybe you can ask to keep them for a follow up review, until the mk2 version will be available...

it is by far the best review of Dutch & Dutch 8c available today.
@Bruno Putzeys or to whom is concerned... pls let @hardisj or @amirm to review your Kii three so we finally have the winner among controlled directivity speaker below 15k€.
my best

 

[q3cpma]

Okay, I made the slot five times as big.
View attachment 116833 View attachment 116836 View attachment 116835 View attachment 116845

Even if I make the slot ten times larger (last image slot SPL), the resonance remains. But the low-pass behavior has decreased significantly.
The influence of the resonance should therefore be kept as low as possible. With appropriate damping, this can certainly still be somewhat suppressed or "smudged".

A Helmholtz resonance is still present, but is undesirable?

That's my guess. All I've read about it points to an acoustic line (including the aforementioned need for a wide bandwidth). Here's a repost of the most relevant part:

You could try to dissect an ME Geithain and see what magic they use to do it passively down to 30 Hz. There's a technical interview about it in https://www.me-geithain.de/en/assets/media/products/studio/RL901K/en/PPThomsen-RL901K-02-05-eng.pdf

Production Partner: Mr. Kiesler, how do you achieve cancellation of waves with
wavelength in meter range, and this not only for a few discreet Hz but within a
1:10 bandwidth? After all, we talk about wavelength, which extend between 1 and
10 meters.

Jochen Kiesler: Well, for sure not by deceiving physics. That won’t do. To sum
it up, the trick was to attach an acoustic phase-rotation line at the back of a
loudspeaker which produces a phase-shift of 160 degrees. Thereby both, the
phase and the amplitude must be kept constant within 5 degrees and – this is
the biggest problem – irrespective of pressure conditions. After all, the range
of pressure inside the box differs from 25 to 125 dB and for all that, the
specific flow resistance has to be the same.

PP: In other words, the flow resistance causes a wideband delay?

J. K.: You could say so. We use a combination of several materials which I
would not like to discuss in detail now. Inside the loudspeaker box RL 901K
there are two separated cabinets which close up with these flow resistances in
their back. The dimensions of the flow resistance and of the membrane
correspond to each other and if you choose the correct combination, it works
for frequencies down to 30 Hz.

PP: Why hasn’t anybody come up with this idea before?

J.K.: Well, there has not been any lack of attempts. Some approaches use two
subwoofer set up against each other – actually a plausible idea. In practice
however, you would need two high-quality low frequency drivers with an
amplifier and the matching enclosure for each. Therefore it never became a
commercial product. Whereas we have some experience with constructing
loudspeakers which emit a cardioid characteristic down to 100 Hz from working
with PA- systems. One day we asked ourselves if we could extend this principle
to still lower frequencies even if there was no theoretical basis for it.

PP: Delay actually implies that the sound velocity is reduced in the acoustic
line. Is this really true?

J. K.: Yes. It is reduced from the usual 330 m/s down to approximately 310 to
220 m/s. This can be determined indirectly by a phase measurement.

 

[HiFidFan]

...Just Amazing Review of Amazing speaker. I really hope M.Mensink would provide you a huge (90%?) discount to reward for the incredible and objective review you just publish. it is by far the best review of Dutch & Dutch 8c available today.
...*snipped*...

This is a terrible, terrible suggestion. Manufacturers rewarding reviewers for positive reviews?

 

[MZKM]

Well, thanks to my chat with Christian, I know it can be done. I don't know how yet. I could export it as a text file but don't know how to export it as a .wav just yet. I'll try to remember to ask Christian how to do that.


See around this time stamp:

I get an error saying you haven’t allowed this video to be viewed on other sites.