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Dutch & Dutch 15C Discussion
- Thread starter EAXAE
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Jaxx1138
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I would really enjoy hearing about the results (especially room decay below 200 Hz). I like the idea of arrayed subwoofers for rooms whenever it is possible. Of course measurements (at least for me) tell the whole story.
So he basically want to get a barotrauma experience and liquefy his internal organs or is it maybe he just planned to make his house levitate? Or being a billionaire he just wants to train for a rocket launch I dunno really, these numbers are out of this world!
Jaxx1138
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If it is the application that I have seen before, half of those subs will be used to cancel much of the modal effects of the room.
Definitely an interesting project! I'd also be pretty much interested in comprehensive measurements (RT60 decay graphs etc. from around the listening area) of with and without the Trinnov "active noise cancelling" in place and a sketch of where the subwoofers had to be placed respectively. (Surely I also wouldn't want my system go public.) I can only imagine how a room would look like with let's say 20x JBL SUB18 around. They'd need to be placed all over the space at their respectively best locations for optimum performance. -- And still there would be channels left to expand for proper Dolby Atmos Music if desired.
One could argue that it might be more practical to use maximum possible acoustic room treatment (for bass) in such a scenario and hide it nicely behind fake walls and ceiling; or to combine both (that would be my way) and therefore require a lesser number of "noise-cancelling" subwoofers around the place.
However, I really hope that person will be satisfied and have the widest smile on their face when first auditioning the new system!
Jaxx1138
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For clarification: That is true in this case. But it can be done using the rear (or side) woofers if you should choose too. But it is better using the vented slots. But you are absolutely correct about the Dutch and Dutch. It seems to be the most popular way of doing it.
Waxx
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It's needed for the Trinitov waveforming, a way of making the bass soud good in a room, with a lot of cancelletions. And headroom is also key, to get undistorted bass to about 20Hz. And it's not that it's a small space to fill. And his moto for this was "overkill" (aka i never want to hear that the system is to weak to do this).
But running this as front sub full force, is indeed crazy. But that is not the goal. And the 100kW is peak power, (real life) RMS will be more like 40kW knowing those amps...
How was the choice of the M2's made?
And it is actually quite easy to see the SPL loss of the midwoofer in the nearfield measurements. Considering that in the far field the midwoofer will be 6dB below summing level at 100Hz and same level as the subwoofers, we see that the mid-woofer output is approximately 6dB higher than it would be without cardioid losses. As the subwoofer nearfield response seems a bit high in level, cardioid loss may even be somewhat higher (e.g. 8dB at 100Hz).It requires high output from the woofers to create the cardioid radiation pattern. These D&D 8C measurements are from Erin's Audio Corner.
Compared to Neumann KH150. (Note that -20 dB = 10%, -30 dB = 3.2%, -40 dB = 1%)
We also see a THD rise below 300Hz that correlates with the extra output for cardioid dispersion. Relatively high THD above 300Hz seems to be caused by general limitations of the midwoofer and also the tweeter, adding k3 around the mid/high crossover frequency. All of this could be improved with better drivers. I did not find IMD measuremets. Wonder how high these would be considering almost 10% THD at 100Hz/96dB.
Yet, despite the obvious shortcommings in distortion, the 8C is widely regarded as exceptionally good sounding speaker. This raises questions about audibility of distortion at high SPL. Considering that 100dB SPL (pink noise with 12dB crest factor and HP around 60Hz according IEC-268-1, A-weighted) is the regulatory limit for headphones in the EU, we should reming ourself that 96dB is quite high level. Nevertheless, considering the cost of the speaker they should use better drivers imho.
Waxx
Major Contributor
It's certainly true that bass distortion is a lot less audible due to how our hearing works but maybe there are different factors involved which smear the impression.
Most people are probably just used to hear boomy and distorting bass, as that's the norm wherever you go in publicly accessible places (besides the better movie theatres). Like I was invited recently to a party at a friend's house and the scene was concentrated in the living room where of course too loud and bassy music was played. Amongst the over 20 guests I was the only one to be annoyed - everybody else enjoyed the many hours of exposure to noise. Already when I entered the room I could hear the drivers distorting and the bass reflex ports "coughing" (for lack of better words how to describe the vent noise). But I enjoyed the spots with the nulls in that room.^^ Since I always carry some Alpine MusicSafe ear protection with me on my key chain I then still could blend in without going mad (or deaf).
Or as Erin put it on his D&D 8C review, regarding masking in his room: "Speaking of distortion, yes, the measured harmonic distortion is relatively high. But, in my listening tests I had this speaker playing as high as 105dB @ 4 meters with no audible distortion other than the things that were buzzing in my living room. I even used test tones to see if I could hear the distortion in my MLP but, alas, the fireplace was vibrating as were some of the items in the bookshelves. Not to mention room modes. I’m not saying that someone else couldn’t hear the distortion if trying. But in my case, in a real living room with other things about, the distortion measured didn’t correlate to distortion heard if for no other reason than it was masked by all the things that make a real room a room. [...]"
Having had the pleasure to listen to the JBL M2 several times which has remarkably low bass distortion, then obviously also in real rooms, I can say that at least for myself it does make a huge difference.
Waxx
Major Contributor
The M2 has a lot of headroom, so in a smaller space on low volume the woofer does not distort. But if you play loud in a big room, the distortion also comes. That's why in bigger rooms using seperate subs with the M2 highpassed at 80Hz is needed to have low bass distortion.
But it's certainly true that most people hear bass with a lot of distortion. Their subs are just to small to work without. An 8" driver can give you 20Hz, but not loud and low distortion at the same time, it's membrane is just to small for that. That is why big cones are still so popular for home use. On DIY audio a 3 way with a 12" woofer (whatever the alignment) seems the holy grail now and since long. Everything smaller is a compromise. And i tend to agree.
But it's certainly true that most people hear bass with a lot of distortion. Their subs are just to small to work without. An 8" driver can give you 20Hz, but not loud and low distortion at the same time, it's membrane is just to small for that. That is why big cones are still so popular for home use. On DIY audio a 3 way with a 12" woofer (whatever the alignment) seems the holy grail now and since long. Everything smaller is a compromise. And i tend to agree.
Yes, that's exactly the reason why HARMAN introduced the JBL SUB18 for use alongside the M2. And since the woofer works up to 800 Hz in the M2, that would also significantly improve midrange performance!
I think I never listened to the M2 in a room larger than maybe 80 m² or sitting farther away than 3 ½ m (by the "38% rule"), so I was quite impressed by its sole output.
Are the graphs using different values? The one for the 8c's are showing the distortion in db's while the Neumann's are showing the value in distrotion percentage. It appears to be apples and oranges to me, or am I wrong? Seriously asking here...It requires high output from the woofers to create the cardioid radiation pattern. These D&D 8C measurements are from Erin's Audio Corner.
Compared to Neumann KH150. (Note that -20 dB = 10%, -30 dB = 3.2%, -40 dB = 1%)
It's more like comparing red and green apples.
Granted, you need a minimum of imagination but he actually mentioned the correct conversion rates in the same post you just quoted:
dB and percents are just different ways of expressing a ratio, and we can easily convert one to the other. dB uses logarithmic scale, so easier to see the smaller values. For example, if we plot percentage using a linear vertical scale of 0% to 100%, you can hardly distinguish 0.1% from 0.01% when looking at the plot, because both are very close to the bottom. With dB scale, 0.1% is -60 dB and 0.01% is -80 dB and there is good separation between the 2 numbers if you plot using a vertical scale of, for example, -120 dB to 0 dB.
Here is an online converter for % to dB.
THD to dB - convert percent % to decibels dB percentage voltage % vs per cent converter THD+N total harmonic distortions calculation signal distortion factor attenuation in dB to distortion factor k in percent decibel damping - sengpielaudio Sengpiel
Calculate THD and distortions decibels dB to percentage % per cent percent voltage % vs converter and dB signal distortion THD+N total harmonic distortions factor attenuation damping - Eberhard Sengpiel sengpielaudio
So, if I used the calculator correctly - the Dutch&Dutch has approximately 1% THD at 50hz @86db /3.98% at 96db.....compared to 0.97% @86db /2.8% @96db for the KH150 (both at 50hz)It's more like comparing red and green apples.
Granted, you need a minimum of imagination but he actually mentioned the correct conversion rates in the same post you just quoted:
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