Definitive Demand D11 Speaker Review

[watchnerd]

In a pinch, you could probably use it for some other kind of plug.

That's something @Thomas savage would think.

 

[KaiserSoze]

Yah and also the one on the MM de Capo Reference 3a Be, is pretty unusual.
I think both are hoping to draw attention to what is otherwise not interesting. Sales and or maybe they actually have developed a useful design ala KEF tangerine tweeter guides.

View attachment 80016View attachment 80017

That one looks straight out of Buck Rogers, like its gonna start emitting Tesla arcs any second now, or maybe emit a sound like a theremin

 

[watchnerd]

Steel appliances and piano gloss audio gear.

My speakers are piano gloss white and aluminum.

 

[Maiky76]

An interesting post. I would like to know more about how it was determined that the surround is the cause of the nasty and peculiar resonance at 615 Hz.

I've been intrigued by Definitive's dual surround drivers for a while. I've only been able to think of one possible rationale, but haven't been able to follow up on it because I haven't had the raw driver to inspect. Possibly, the inner surround eliminates the need for the spider and improves the linearity of the suspension. I have no idea whether this is correct; it is just something that occurred to me as a possible rationale for the inner surround. If it happens that the spider is eliminated, it apparently did not have the intended effect of lowering distortion, judging by the distortion measurements.

I was not aware of their surround IP.
Audax did is in the past, it should work well to help the symmetry of the driver excursion decreasing odd distortion Harmonics, if correctly done.

Anyways here is why:

1. Both the 615Hz and 1230Hz can be seen in power response, so most likely this not an interference. Something is radiating energy.

2. If you look at the near field measurement of the mid-woofer:
You can clearly see the peaks (and some other features like the tuning of the PR at around 56Hz and smaller peaks).
This data should be highly dominated by the Mid-woofer contribution.
If we were looking at a box wall issue, it would probably not show up that much (being 5dB up so nearly double the output of the Mid-woofer) in the near field unless something really really wrong is happening, it would also show up in the THD to a crazy level.

3. In the directivity plot I published you can see the peaks not having the same directivity as the Mid-Woofer almost omnidirectional.
This means it is a small object, much smaller that the entire driver, therefore fully eliminating the wall issue walls are large so they have narrow directivity, and don't move much normally.

So we know it is something small (smaller than the driver) with therefore a small area, and therefore this means large displacement/high efficiency.
Small area must have large excursion to radiate large SPL.

4. Wave length = Sound speed / frequency L = 343/615
The wave length we can calculate is about 56cm.
Note that 1230Hz is exactly the first harmonic half the wavelength.
This is the critical dimension of the "issue".

The external size of the box is 33x18x32cm
difficult to know the exact internal dimensions but 56cm or (23cm) does not seem to fit easily inside, so internal resonance are not likely but difficult to rule that 100% out. However, the amplitude seems really really high and the directivity does not match what one would expect from an internal acoustic mode.

On the other hand if that is the perimeter of something the full wavelength should fit for the resonance to occur, then
piDiameter = 56cm Diameter = 17.75cm give or take, plus the temp/humidity/model limitations

5. Now the driver is a 16.51cm which not accurate usually
Not a coincidence
The 615Hz is most probably the fundamental mode of the surround and 1230Hz the first harmonic (double the resonance pattern can fit in the same dimension) both can be seen in the impedance plot

 

[restorer-john]

That's something @Thomas savage would think.

Thomas doesn't just think- he's a doer. I think he's done with his various phase plugs and moved on to bigger and better things. Actually, they remind me of those plaster roof things- what are they called- you know like the ceiling air-conditioning toroidal ring vents?

 

[Doodski]

like the ceiling air-conditioning toroidal ring vents?

A whirly bird thingymajiggy, doomaflooper scoobydoo.

 

[restorer-john]

A whirly bird thingymajiggy, doomaflooper scoobydoo.

Like these:

 

[YSC]

I would say the design and look of it is definitely catching my liking but the measurements don’t, kind of feeling for the kef LS 50 in my book, after reading all these I think those powered studio monitors will be my only choice like Genelec, Neumann, Adam and focal etc.

 

[MZKM]

P.s., I'd suggest posting the negative and positive horizontal angles when tweeters are offset. They are usually quite different.

I thought about that, I currently show the average of both, as you are going to be listening to both at the same time.

 

[napilopez]

I read your post several times, and each time I tried scratching my head to see if it would help me figure out the point you were trying to make. Sadly, it did not help. As for the part I excerpted above, which relates to the question of value, it does not seem to me that there would be any alternative way to take the measurements that would change what seems obvious to me. Aside from the rather industrial aesthetics that appeal to some people, perhaps the majority, the D11 is a mediocre speaker at a premium price. For people who really like the industrial aesthetic, they might be worth the price, but of course this is very subjective. They will look right in a room with modern decor, the kind of room you see in Modern Architecture, but out of place in a room with more traditional decor. Warm in appearance they are not. Frigid would be a better word. Some people like frigid, other people do not. I'm kind of on the fence. I like modern architecture, and if I had a room decorated in the modern style I would probably look more than once at the D11, but I would likely decide in the end that the aesthetic does not justify the price. One speaker that comes to mind as an alternative is the DBR62. It is almost certainly a better speaker, it costs a lot less (unless you catch the D11 on sale for $500 and the DBR62 still has not been put on sale...), and to my eye the white one is more attractive than the D11 even in a modern decor setting. All of this is very subjective of course, except for the fact that the DBR62 is a better speaker that ordinarily costs less.

Sorry if my post wasn't clear, as the concept is really quite simple. I will try to clarify.

When tweeters are offset, each half of the speaker will radiate sound differently, and one side of the speaker's radiation will almost inevitably be better than the other. This is certainly the case for D11, as shown in my earlier post, as well as the D9 I'd tested. You, therefore, want to be careful about how you position the speakers.

Problem is, the spinorama weighs both sides of the speaker equally, probably because most speakers are indeed symmetrical. But my anecdotal experience suggests that whichever side of the speaker is closest to your sidewall will be perceptually dominant -- which I believe is an intuitive result. If the good side is closer to your sidewall, it will have a louder and earlier reflection.

Deftech clearly designed the speakers with this in mind, and it's why the speakers are specifically labeled as 'Left' and 'Right.'

I made a drawing to better illustrate what I mean:

Because the offset is mirrored, you get the same perceptual 'weighting' to the good side with the left speaker as well.

Anecdotally, the advantage of this approach was very obvious to me during testing. When I tried switching the D9 to the opposite side of what Deftech recommended, it was like a different speaker; timbrally similar, but the soundstage had compressed majorly and become relatively 'fuzzy'. (You could of course argue confirmation bias, but that's a risk we take with any sighted listening.). I also tried positioning the speakers a little bit wider to compensate for the difference in the tweeter-to-tweeter width, to no avail.

Anyway, all this is to say that I expect D11 sounds (at least a little) better than the spinorama and preference score suggest, but the reasons why are still apparent from the detailed measurements. You can of course achieve good directivity without an offset tweeter, but I believe the approach here is effective too (at least for the D9). A waveguide will usually narrow directivity, and a slightly rounded edge will only do so much. The D9 illustrates how this can work more clearly than the D11. Its 'good side', for example, had some pretty excellent results for a simple cone and dome. The 'bad' side on the other hand, was awful, but it's not what my ears picked up on... except when I inverted the setup.

As for whether the DBR-62 would be better, I agree that it's probably the better speaker, but I'm not convinced it's the better speaker. Its on-axis is kind of janky, and though it doesn't have as sharp of resonance at 600Hz, it still has a sizeable one that is wider. On-axis and PIR of the D11 and the Elac:

As for the design, the Elac is definitely closer to my personal aesthetic actually. But the deftech is really built on the exterior like a fairly high end speaker -- the aluminum faceplate is rare and it just feels all fancy - higher-end than say, the Focal Chora or Buchardt S400. It feels just as well built as the KEF R3 imo. From what I can tell the elac looks pretty nice but the finish is fairly cheap. Of course, this is all very subjective.

There are pretty much always going to be better options for cheaper of course, but I thought I'd illustrate why the speakers might not be horrendous. My pick for the price would be the Focal Chora 806, but they're definitely a step down in build quality (though more to my aesthetic).

 

[napilopez]

I thought about that, I currently show the average of both, as you are going to be listening to both at the same time.

See above =]

 

[thewas]

What's going on with the woofer dust cap?

From the picture, it's hard to tell if it's "decoration" or some kind of functional aspect?

Or a strange mushroom shaped phase plug?

Its always funny how in Hifi stuff that was already very short-lived in the 70s comes back again and again

Source of photo: https://www.hifi-wiki.de/index.php/Dual_CL_730

 

[ctrl]

2. If you look at the near field measurement of the mid-woofer:
You can clearly see the peaks (and some other features like the tuning of the PR at around 56Hz and smaller peaks).
This data should be highly dominated by the Mid-woofer contribution.

The interpretation of Amir's near-field measurement is difficult because the distance of the measuring microphone to the woofer is not specified.
The rule of thumb for a reliable near-field measurement (the term is used differently in this context than in studio technology) would be
Measuring distance < 0.11 * Dimension sound source
The measuring distance for the woofer with a surround diameter of about 0.13m would therefore be <0.015m (<0.6'').
If the measuring distance is greater, the measurement becomes less reliable and in this case captures sound from the other chassis.

A surround resonance behaves in antiphase to the chassis membrane. It should therefore lead to a frequency response dip (due to the phase shift a sound cancelling occurs) and not to an peak as in Amir's measurement.

5. Now the driver is a 16.51cm which not accurate usually
Not a coincidence
The 615Hz is most probably the fundamental mode of the surround and 1230Hz the first harmonic (double the resonance pattern can fit in the same dimension) both can be seen in the impedance plot

The diameter of the woofer surround is about 0.13m, so this doesn't really fit.

The frequency of the surround resonance depends not only on the diameter of the chassis but also on the driver cone material and the surround material (specific mass, stiffness of the material,...), surround shape,...

 

[gowla]

It was on sale for $530usd between Dec 17, 2019 - Jan 5, 2020 on amazon.

I got the D9's in White for €370 back in December from Amazon Italy, Currys in the UK had the D7's as low as £180 a few months ago. Nice if you can get for the sale prices as they seem quite generous

 

[Maiky76]

The interpretation of Amir's near-field measurement is difficult because the distance of the measuring microphone to the woofer is not specified.
The rule of thumb for a reliable near-field measurement (the term is used differently in this context than in studio technology) would be
Measuring distance < 0.11 * Dimension sound source
The measuring distance for the woofer with a surround diameter of about 0.13m would therefore be <0.015m (<0.6'').
If the measuring distance is greater, the measurement becomes less reliable and in this case captures sound from the other chassis.

View attachment 80039


A surround resonance behaves in antiphase to the chassis membrane. It should therefore lead to a frequency response dip (due to the phase shift a sound cancelling occurs) and not to an peak as in Amir's measurement.
View attachment 80049

View attachment 80050




The diameter of the woofer surround is about 0.13m, so this doesn't really fit.

The frequency of the surround resonance depends not only on the diameter of the chassis but also on the driver cone material and the surround material (specific mass, stiffness of the material,...), surround shape,...

Good rebuttal,
I am aware that the near field as measured by Amirm might not be perfect but that's all we've got.

What do reckon it could be then to be 5dB above the regular driver output, almost omnidirectional at 615Hz (with an harmonic at 1230Hz) and show up on the driver impedance?

some drivers do show some similar issues:
https://bcspeakers.com/en/products/lf-driver/15-0/8/15tbx100-8

 

[ctrl]

What do reckon it could be then to be 5dB above the regular driver output, almost omnidirectional at 615Hz (with an harmonic at 1230Hz) and show up on the driver impedance?

some drivers do show some similar issues:
https://bcspeakers.com/en/products/lf-driver/15-0/8/15tbx100-8

It could be a different kind of chassis resonance , although I don't believe that a chassis with a 5dB resonance would be used for a 2-way concept.

You had written:

The external size of the box is 33x18x32cm
difficult to know the exact internal dimensions but 56cm or (23cm) does not seem to fit easily inside, so internal resonance are not likely but difficult to rule that 100% out.

There is a small error in the consideration, the first resonance point is triggered by the first standing half-wave in the speaker cabinet.
The cabinet dimensions are HxWxD 0.33x0.18x0.32m and two sides are almost the same size - which is rarely a good idea. If we subtract about 4cm for the thickness of the case walls, the first half-wave is in the range 590-610Hz and the fundamental wave is at 1180-1220Hz.
That would fit in pretty well.
A cabinet resonance would also be seen as a peak on the impedance curve.

Added to this are possible influences of the passive radiator, which, as others have said, may be identical to that used in the Buchardt A400.

 

[temujin44]

wondering if you ever listen first and then take measurements. any chance you could be biased by your measurements?

 

[JohnBooty]

Thanks for the tip on that site, accessories 4 less. It looks like they have great prices on a lot of stuff, including some of those Yamaha integrated amps that I like. Even some newer models that aren't yet shown on Yamaha's site!

I will second the recommendation for Accessories4Less.com ...despite their slightly worrisome name.

We've recommended them for a few years now at r/budgetaudiophile and I've not heard any complaints. I got my own Denon receiver from them a few years back and it was pristine. When I am in the market again, they will be at the top of my list if they are selling what I'm looking for.

To the best of my knowledge they appear to be selling "legitimate" factory refurbs sourced from the original manufacturers as opposed to customer returns or display units.

wondering if you ever listen first and then take measurements. any chance you could be biased by your measurements?

You don't need to be wondering. It's the very first sentence of his subjective impressions: "I listened to the D11 without seeing the measurements. First impression was positive...."

 

[napilopez]

wondering if you ever listen first and then take measurements. any chance you could be biased by your measurements?

Most of the time amir does not. You'll be biased either way though. There have been a few times amir hasn't liked a speaker with very good measurements too.

 

[KaiserSoze]

I was not aware of their surround IP.
Audax did is in the past, it should work well to help the symmetry of the driver excursion decreasing odd distortion Harmonics, if correctly done.

Anyways here is why:

1. Both the 615Hz and 1230Hz can be seen in power response, so most likely this not an interference. Something is radiating energy.

2. If you look at the near field measurement of the mid-woofer:
You can clearly see the peaks (and some other features like the tuning of the PR at around 56Hz and smaller peaks).
This data should be highly dominated by the Mid-woofer contribution.
If we were looking at a box wall issue, it would probably not show up that much (being 5dB up so nearly double the output of the Mid-woofer) in the near field unless something really really wrong is happening, it would also show up in the THD to a crazy level.

View attachment 80023

3. In the directivity plot I published you can see the peaks not having the same directivity as the Mid-Woofer almost omnidirectional.
This means it is a small object, much smaller that the entire driver, therefore fully eliminating the wall issue walls are large so they have narrow directivity, and don't move much normally.

So we know it is something small (smaller than the driver) with therefore a small area, and therefore this means large displacement/high efficiency.
Small area must have large excursion to radiate large SPL.

4. Wave length = Sound speed / frequency L = 343/615
The wave length we can calculate is about 56cm.
Note that 1230Hz is exactly the first harmonic half the wavelength.
This is the critical dimension of the "issue".

The external size of the box is 33x18x32cm
difficult to know the exact internal dimensions but 56cm or (23cm) does not seem to fit easily inside, so internal resonance are not likely but difficult to rule that 100% out. However, the amplitude seems really really high and the directivity does not match what one would expect from an internal acoustic mode.

On the other hand if that is the perimeter of something the full wavelength should fit for the resonance to occur, then
piDiameter = 56cm Diameter = 17.75cm give or take, plus the temp/humidity/model limitations

5. Now the driver is a 16.51cm which not accurate usually
Not a coincidence
The 615Hz is most probably the fundamental mode of the surround and 1230Hz the first harmonic (double the resonance pattern can fit in the same dimension) both can be seen in the impedance plot

I think you have enough reason there to formulate a weak hypothesis, but not nearly enough to say with any certainty or confidence that the anomalies are caused by the driver surround. I carefully read what you wrote but was not able to discern whether you are suggesting a standing wave in the air at the throat of the driver, between the inner surface of the surround, or whether you are suggesting a standing wave within the surround itself. Either way, I did not see anything in what you wrote that would attempt to explain the sharp dip appearing at frequency very slightly below the sharp peak. Since this is a definitive characteristic of the phenomenon, any hypothesis would need to include an explanation for this. If you are proposing a standing wave in the air associated with the distance between opposing parts of the surround (i.e., the inner diameter of the surround), then it is not apparent to me how this would explain the sharp dip that immediately precedes the sharp peak. And if this were the correct explanation, we should see the very same thing in virtually every speaker that is measured. Which of course we do not. If you are proposing a standing wave in the surround itself, then none of the calculations apply because the velocity of sound within the surround itself will be entirely different from the velocity of sound in the air.

The wavelength associated with 615 Hz is 56 cm. The inner diameter of the surround is 13 cm. The inner diameter of the surround would potentially support a standing wave at 2 x 13 cm = 26 cm => 1.32 kHz. It would also support standing waves at higher frequencies, but I cannot see as how it would support a standing wave at 615 Hz, where wavelength/2 is 28 cm.

A conspicuous attribute shared by this speaker and another speaker where the same apparent phenomenon was observed (i.e., a sharp dip immediately preceding the sharp peak) is the use of a passive radiator. Since all speakers have surrounds but not all have passive radiators, it is substantially more likely that the explanation involves the passive radiator than the surround. An interesting fact about passive radiators is that they reside at the surface of the enclosure; ported speakers are not like this, i.e., the port extends well into the interior of the enclosure.

Two of the exterior dimensions of the enclosure are 33 cm and 31.8 cm. These are so close that the associated standing waves will mutually reinforce. Given this, and given that the passive radiator resides at the enclosure surface, it seems appropriate to investigate a hypothesis that the passive radiator is both supporting the modes of the enclosure and allowing them to escape. There is a standard formula for calculating room modes, which applies just the same to a speaker enclosure. It involves taking the inverse of the internal dimensions, multiplying by small positive integers starting with 1, adding these values together then taking the square root, etc. I haven't taken any time to play with it, but I would not be surprised if it turned out that the two nearly identical dimensions of the enclosure produce strong modes at frequencies where the resonances appear. If so, the conclusion would then be that the passive radiator is both supporting the modes and allowing them to escape into the air. Since the passive radiator sits on top, this would potentially explain the difference in directivity for the resonances.

I do not think that Amir attempted to measure the output of the passive radiator directly, by placing the microphone just a few centimeters from the center of the passive radiator. If he had and if the resonances were clearly evident in the passive radiator, this would constitute compelling evidence that internal standing waves are the source of the resonances and that they are escaping partly through the passive radiator. Amir cannot do any modifications, but if it were possible to open the enclosure and stuff it tightly with good damping material, and if the resonances were definitively reduced by doing so, this would constitute further evidence in favor of this hypothesis.