Speaks well for the quality of your process.
So all I need to do this is a Umik, REW, cake turntable, and a homemade protractor? I may try it one of these days just for S and G.
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Dutch & Dutch 8c Review
- Thread starter hardisj
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So all I need to do this is a Umik, REW, cake turntable, and a homemade protractor? I may try it one of these days just for S and G.
And the patience to do 70 measurements (of if the speaker is symmetrical, you can just do 1 side of the horizontal off-axis and duplicate the results).
Your windowing will determine how low in frequency you can measure, and I guess ground plane is the best method, so you need quite a distance (see Erin’s videos), and to angle the speaker so the tweeter is facing the mic).
It is not fun.
Please help me understand:
If we have a dac, an amp, and a speaker in three different boxes, and the amp or dac has low SINAD, heads are chopped.
If we put everything in one box, then it’s a complete product and low SINAD of components is irrelevant.
If someone loans you a car engine to review, you perform a certain set of measurements.
When someone loans you a car to review, you do so using another set of measurements (which may or may not overlap).
Whether a product can be torn down and its components reviewed individually is subject to real world restrictions (whether the owner or company allows it? Is warranty voided?). Surely that's obvious to anyone what the reviewers (and their readers) have to be mindful of. Unless you're just trolling.
To take it further, by your rationale, should reviewers disconnect/desolder the power supply component in the review of a power amplifier and review it separately? Test every capacitor on the circuit board?
Specifically on your 'low SINAD' comment:
The products are reviewed in different 'categories'. Each product has a ranking relative to other equivalent products.
A basketball player's 3-point percentage could be ranked 'lowly' in NBA league, but the same performance may be ranked 'highly' in a lesser league elsewhere. His performance ranking is dependent on external conditions around him. I'd admit it's not a perfect analogy, but hope it helps paint a clearer picture.
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Interesting that you preferred the 8351b. Also your room must be pretty big. I get ~30Hz extension with the 8351b here, and 8C went down to 20Hz iirc.
I meant affiliate links. I changed the post.
Here on DIYAUDIO a dozen years ago, I think it's part of the genesis of these great speakers. There are some interesting conversations with Earl Geddes ...https://www.diyaudio.com/forums/multi-way/192737-2-waveguide-cardioid-6.html
I quite like the pedastal stand they sell which can be had in a veneer to match the speakers, there is a broad choice.I kind of like the metal stand look they have, it takes no prisoners.
Interesting measurement and thanks for posting. The horizontal directivity changes from 100° at 3200 Hz to 140° at 1000 Hz. Widens some further before it narrows slightly at around 350 Hz. The vertical directivity and distortion is what you expect from a speaker design like this.
Not to start an argument, but you tried out affiliate links too…
Or was it affiliate links but to Amazon in general and not reviewed products, but there was some issues with getting that to work properly (which is why you stopped)?
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TabCam
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Odd that they do not give the measurements above 10 kHz. The 100-10.000 Hz looks remarkably clean. Btw, the Magico s5 seems to have simular clean distortion figures although I am not sure as it is hard to compare dB and % graphs.
Probably because all harmonics of fundamentals above 10kHz are outside the range of human hearing.
Would like to expand on my "theory" from post#218 about the cause of the high harmonic distortion of the 8C around 100Hz.
Nevertheless, the slots are Helmholtz resonators, on that we agree - right?
Are you saying that in your simulations you didn't see a significant increase in midrange driver excursion (compared to sealed cabinet) when using the side slots and the source of the increased HD3 is not caused by the midrange driver excursion?
The side slots have a maximum effect around their tuning frequency. However, this means that the midrange driver must still emit sound pressure below the tuning frequency of the slots, otherwise the slots cannot perform their full effect.
I have created a very simple simulation with one slot and an 8'' woofer with a small cabinet.
The tuning frequency is much lower than the D&D 8C, but this would be shifted to higher frequencies when using multiple slots.
To demonstrate my "theory" one slot is sufficient (who wants more, has to pay me for it
).
The views show a cutaway view of the simulated loudspeakers. The closed speaker has a bit more volume than the one with the slot - but that doesn't matter for the comparison.
Sealed version:
Slot version:
The fact that the slot is located on the front is also irrelevant for the intended comparison of driver impedance and driver excursion.
First, we compare the driver impedance of the sealed version with the sloted version:
The closed loudspeaker shows a typical impedance curve with a resonance frequency fc at around 93Hz.
If a slot is now attached (the slot is only as deep as the material thickness of the speaker walls), the picture changes completely.
The result is an impedance curve typical for bass reflex systems, with the decisive difference that the two impedance maxima are very far apart.
This means that the sound radiation of the slot extends over a very wide frequency range.
It is therefore not the damping of the slot, but the slot itself that is responsible for this.
The slot reaches its maximum sound pressure at the "small" impedance hump. In the case of the simulation at 200Hz:
Around this frequency the cancellation (the cardioid effect) is therefore greatest - since the radiated sound from the slot is phase inverted to the radiated sound from the driver.
Looking at @hardisj's measurements, for the 8C this could be around 350Hz.
So, what happens if the midrange driver, for example, has to deliver almost full sound pressure two octaves below the maximum slot sound pressure (200Hz in the simulation)?
In our simulation, this would be down to about 50Hz. Therefore, a fourth order filter was set at 40Hz.
Let's look at the driver excursion of the two concepts (sealed vs. slot):
At 50Hz, the typical behavior of a ported driver operated below its tuning frequency becomes apparent.
In our example, the driver of the slot version must displace twice as much at 50Hz as the sealed version.
The solution would be to simply cross the midrange driver at a higher crossover frequency. But this would also shift the lower limit of the cardioid effect to higher frequencies.
On top of that, the midrange driver probably have to deliver a bit more sound pressure to partially replace the one destroyed by cancellation, so that the speaker does not to sound too "thin" in the bass and lower midrange.
As @Kvalsvoll has already indicated:
Important: This is only my "theory" for the cause of the immensely high HD3 around 100Hz of the 8C. To verify this, one would have to simulate the cabinet with slots and driver of the 8C.
Nevertheless, the 3% third-order harmonic distortion shown by the 8C in the frequency range around 100Hz, at just 86dB SPL, is very bad for a speaker in this price range.
@amirm tested bookshelf loudspeaker for under $300 that remained well below 1% THD in this frequency range
.
Nevertheless, the slots are Helmholtz resonators, on that we agree - right?
Are you saying that in your simulations you didn't see a significant increase in midrange driver excursion (compared to sealed cabinet) when using the side slots and the source of the increased HD3 is not caused by the midrange driver excursion?
The side slots have a maximum effect around their tuning frequency. However, this means that the midrange driver must still emit sound pressure below the tuning frequency of the slots, otherwise the slots cannot perform their full effect.
I have created a very simple simulation with one slot and an 8'' woofer with a small cabinet.
The tuning frequency is much lower than the D&D 8C, but this would be shifted to higher frequencies when using multiple slots.
To demonstrate my "theory" one slot is sufficient (who wants more, has to pay me for it
).The views show a cutaway view of the simulated loudspeakers. The closed speaker has a bit more volume than the one with the slot - but that doesn't matter for the comparison.
Sealed version:
Slot version:
The fact that the slot is located on the front is also irrelevant for the intended comparison of driver impedance and driver excursion.
First, we compare the driver impedance of the sealed version with the sloted version:
The closed loudspeaker shows a typical impedance curve with a resonance frequency fc at around 93Hz.
If a slot is now attached (the slot is only as deep as the material thickness of the speaker walls), the picture changes completely.
The result is an impedance curve typical for bass reflex systems, with the decisive difference that the two impedance maxima are very far apart.
This means that the sound radiation of the slot extends over a very wide frequency range.
It is therefore not the damping of the slot, but the slot itself that is responsible for this.
The slot reaches its maximum sound pressure at the "small" impedance hump. In the case of the simulation at 200Hz:
Around this frequency the cancellation (the cardioid effect) is therefore greatest - since the radiated sound from the slot is phase inverted to the radiated sound from the driver.
Looking at @hardisj's measurements, for the 8C this could be around 350Hz.
So, what happens if the midrange driver, for example, has to deliver almost full sound pressure two octaves below the maximum slot sound pressure (200Hz in the simulation)?
In our simulation, this would be down to about 50Hz. Therefore, a fourth order filter was set at 40Hz.
Let's look at the driver excursion of the two concepts (sealed vs. slot):
At 50Hz, the typical behavior of a ported driver operated below its tuning frequency becomes apparent.
In our example, the driver of the slot version must displace twice as much at 50Hz as the sealed version.
The solution would be to simply cross the midrange driver at a higher crossover frequency. But this would also shift the lower limit of the cardioid effect to higher frequencies.
On top of that, the midrange driver probably have to deliver a bit more sound pressure to partially replace the one destroyed by cancellation, so that the speaker does not to sound too "thin" in the bass and lower midrange.
As @Kvalsvoll has already indicated:
Important: This is only my "theory" for the cause of the immensely high HD3 around 100Hz of the 8C. To verify this, one would have to simulate the cabinet with slots and driver of the 8C.
Nevertheless, the 3% third-order harmonic distortion shown by the 8C in the frequency range around 100Hz, at just 86dB SPL, is very bad for a speaker in this price range.
@amirm tested bookshelf loudspeaker for under $300 that remained well below 1% THD in this frequency range
.
I've always seen them described as "acoustic phase-rotation line" or the like by MEG. 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. As others said, I just see it as a way to manipulate the phase of the backwave so that it's in inverse polarity of the front when they meet.
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Probably the 12 foot vaulted ceiling and there is an opening on one side leading to dining room. In my case the Genelec has a positive wife factor she likes them better than any speaker I've ever had. Of course that might be her way of attempting to keep me from buying more speakers.
Most likely because mic is not calibrated above 20kHz and measurement is most likely done with 48kHz/24bit sampling. Most measurement programs limit distortion scale automatically based on sampling limits.
Would like to expand on my "theory" from post#218 about the cause of the high harmonic distortion of the 8C around 100Hz.
Nevertheless, the slots are Helmholtz resonators, on that we agree - right?
Are you saying that in your simulations you didn't see a significant increase in midrange driver excursion (compared to sealed cabinet) when using the side slots and the source of the increased HD3 is not caused by the midrange driver excursion?
The side slots have a maximum effect around their tuning frequency. However, this means that the midrange driver must still emit sound pressure below the tuning frequency of the slots, otherwise the slots cannot perform their full effect.
I have created a very simple simulation with one slot and an 8'' woofer with a small cabinet.
The tuning frequency is much lower than the D&D 8C, but this would be shifted to higher frequencies when using multiple slots.
To demonstrate my "theory" one slot is sufficient (who wants more, has to pay me for it
The views show a cutaway view of the simulated loudspeakers. The closed speaker has a bit more volume than the one with the slot - but that doesn't matter for the comparison.
Sealed version:
View attachment 116780
Slot version:
View attachment 116781 View attachment 116782
The fact that the slot is located on the front is also irrelevant for the intended comparison of driver impedance and driver excursion.
First, we compare the driver impedance of the sealed version with the sloted version:
View attachment 116785
The closed loudspeaker shows a typical impedance curve with a resonance frequency fc at around 93Hz.
If a slot is now attached (the slot is only as deep as the material thickness of the speaker walls), the picture changes completely.
The result is an impedance curve typical for bass reflex systems, with the decisive difference that the two impedance maxima are very far apart.
This means that the sound radiation of the slot extends over a very wide frequency range.
It is therefore not the damping of the slot, but the slot itself that is responsible for this.
The slot reaches its maximum sound pressure at the "small" impedance hump. In the case of the simulation at 200Hz:
View attachment 116790
Around this frequency the cancellation (the cardioid effect) is therefore greatest - since the radiated sound from the slot is phase inverted to the radiated sound from the driver.
Looking at @hardisj's measurements, for the 8C this could be around 350Hz.
View attachment 116789
So, what happens if the midrange driver, for example, has to deliver almost full sound pressure two octaves below the maximum slot sound pressure (200Hz in the simulation)?
In our simulation, this would be down to about 50Hz. Therefore, a fourth order filter was set at 40Hz.
Let's look at the driver excursion of the two concepts (sealed vs. slot):
View attachment 116791
At 50Hz, the typical behavior of a ported driver operated below its tuning frequency becomes apparent.
In our example, the driver of the slot version must displace twice as much at 50Hz as the sealed version.
The solution would be to simply cross the midrange driver at a higher crossover frequency. But this would also shift the lower limit of the cardioid effect to higher frequencies.
On top of that, the midrange driver probably have to deliver a bit more sound pressure to partially replace the one destroyed by cancellation, so that the speaker does not to sound too "thin" in the bass and lower midrange.
As @Kvalsvoll has already indicated:
Important: This is only my "theory" for the cause of the immensely high HD3 around 100Hz of the 8C. To verify this, one would have to simulate the cabinet with slots and driver of the 8C.
Nevertheless, the 3% third-order harmonic distortion shown by the 8C in the frequency range around 100Hz, at just 86dB SPL, is very bad for a speaker in this price range.
@amirm tested bookshelf loudspeaker for under $300 that remained well below 1% THD in this frequency range
.
Interesting discussion, but now we are moving in to details that is problematic to further discuss in this thread, as they are not very relevant to the review, and it would be wrong to present theories and solutions that will be linked to a speaker that someone else has designed.
If there is interest in further discussion, I suggest starting a new thread in appropriate section of the forum. Then we can start out by discussing general solutions, not related to one specific product. I will not show how to design such speakers, but some explanation of how it works can not hurt.
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.
It needs to radiate over the whole range of frequencies of the mid unit, with appropriate phase shift.
dc655321
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OP
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I think this is getting a bit off the rails here WRT distortion.
As I mentioned in my review, I had this speaker playing above 100dB @ 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.
Aside from THD/HD profiles, the real "selling point" was the lack of mechanical issues. I have had numerous speakers in my room that couldn't get past 90 or 95dB without bottoming out, flopping around, or otherwise emitting audible issues. These issues are much, much more audible than distortion. And in all of those cases, those issues still remained even when a HPF was implemented to help diminish those things. Yet, at >100dB, the DD8c speaker had no such issues while playing down to 20Hz. I can't name another speaker I have tested thus far that has done this. Not even the venerable F226Be which rolled off at around 50Hz.
I'm not making excuses. Truthfully, I was surprised by the relatively high level of HD components. But, in my real-world listening they didn't manifest in to issues. YMMV.
As I mentioned in my review, I had this speaker playing above 100dB @ 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.
Aside from THD/HD profiles, the real "selling point" was the lack of mechanical issues. I have had numerous speakers in my room that couldn't get past 90 or 95dB without bottoming out, flopping around, or otherwise emitting audible issues. These issues are much, much more audible than distortion. And in all of those cases, those issues still remained even when a HPF was implemented to help diminish those things. Yet, at >100dB, the DD8c speaker had no such issues while playing down to 20Hz. I can't name another speaker I have tested thus far that has done this. Not even the venerable F226Be which rolled off at around 50Hz.
I'm not making excuses. Truthfully, I was surprised by the relatively high level of HD components. But, in my real-world listening they didn't manifest in to issues. YMMV.
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