Evidence-based Speaker Designs

[Sergei]

You are attempting to parse every word of mine in a useless semantic battle. Your problem is a complete inability to see the big picture. The unacceptable flaw you find in the LS50 is far more likely the result of science than sloppy engineering. The so-called BBC dip you obviously abhor is there because of an intentional design choice and it works as intended. The uneven frequency response seen in B&W speakers is intentional. Some say it gives the sound the illusion that it is layered.

No doubt there is a lot of in house research which isn't published because they are trade secrets.

Not pertinent to this particular post. Just realized that "Equidistant From Everywhere" means center of the Earth. Who lives there? Devil of course I'm flattered to participate in a forum frequented by one of Them

 

[Ron Texas]

Not pertinent to this particular post. Just realized that "Equidistant From Everywhere" means center of the Earth. Who lives there? Devil of course I'm flattered to participate in a forum frequented by one of Them

I wish that was my only problem.

 

[Ilkless]

I think we are getting carried away. No one is trying to tell you, the audiophiles that Soundbar , Sonos or Bose Acoustimass, etc sound better than your favorite brand or model of speakers. We are simply saying that some mundane speakers and components designs are based on serious Scientific principles. They are not for most of us IOW we are not their market target but have to admit that sometimes they fill our space and lives with what many of us are after: Music.

Precisely - and some are so much more sophisticated than "hi-fi" speakers, but are crippled by their small size, price constraints and peculiar tuning choices. The natural question to ask is: what if such technology was harnessed in a less compromised form factor? And why hasn't anything like that emerged outside of DD or Kii?

 

[Sergei]

Again, when the talk comes up of the sound being bigger due to some bass hump in the Devore, I wonder how that figures in to the impression that everything, at any frequency, sounded "bigger" on the Devores. I played tracks that litterally started with just drum cymbals, or a wood block, or a high pitched flute, and those instruments sounded consistantly bigger, more life sized, than on the slim Joseph speakers. So that part puzzles me if it's *only* going to be due to a frequency response hump somewhere in the bass region.

I think it can be explained by how we perceive the size of objects emitting sound. With a "point source" transducers, a slight turn of head may significantly change the sounds received by Left and Right ear, due to HRTF. With a huge "half room across" speaker, the effect is much smaller.

Devores must be somewhere in between. HRTF is operational, yet to a smaller degree than it is with smaller transducers. Correspondingly, the sound objects are perceived as larger. I also noticed this effect in some mastering rooms, which use speakers with large-diameter transducers.

 

[Sergei]

Until I read this, I thought I was going mad. I bought a pair of KH120s after seeing the 270 {100%} five star reviews. I compared them to my twenty year old Linn hifi system in an instant a/b test. It was a night and day difference. When switching to the Neumanns, the whole sound came "into the centre" almost as if it was mono. By comparison the Linn hifi system sound is spread out between the speakers.
Any idea why this would be so?

I own four KH120s, used as surround speakers, placed at a short distance from the listening position. KH120's tweeter waveguide is designed for a very wide horizontal dispersion, and correspondingly produces a large sweet spot at a close distance, which is good for near-field monitoring.

When placed farther away, the stereo sweet spot devolves into a sound field that is rather uniformly irradiated from the left and from the right speaker, which creates the sensation of mono-ish sound. Place them right around a typical computer monitor though, and you may be much more delighted.

Another KH120 characteristic is port-based cancellation of woofer response at the range of angles which would otherwise cause reflections from a mixing console, and relatively narrow vertical dispersion of the tweeter waveguide serving same purpose.

While they may look like typical bookshelf speakers, they are not. Please make sure that your ear is located above the center horizontal plane of the woofer, ideally at the horizontal plane right between the woofer and the tweeter.

And of course use them with a subwoofer. They can only realistically go noticeably-distortion-free down to 80 Hz at their maximum SPL. That's how I use them - crossed at 80 Hz - and they sound good. Only tried once sending a full-spectrum signal to them - will not repeat.

 

[JJB70]

I think we are getting carried away. No one is trying to tell you, the audiophiles that Soundbar , Sonos or Bose Acoustimass, etc sound better than your favorite brand or model of speakers. We are simply saying that some mundane speakers and components designs are based on serious Scientific principles. They are not for most of us IOW we are not their market target but have to admit that sometimes they fill our space and lives with what many of us are after: Music.

I find it odd that the audiophile segment is so conservative. As you say, D&D and Kii have embraced a lot of the ideas which are now common in the consumer wireless and AV soundbar segments but these are not cheap and very few will be willing or able to spend that much (even though the value is much better than it looks when you consider that you don't need to buy an amp or DAC). Professional studio gear has embraced a lot of the same tech with active monitors pretty much the norm now and things like built in placement correction built into quite a few models. There are some nice active digital and wireless consumer stereo speakers which are very affordable such those made by Edifier and Audioengine, even KEF make some but for some reason the audiophile segment seems reluctant to make the transition. I think it is quite telling that although companies Naim and B&W have been pretty successful developing wireless digital speakers they seem to market them as parallel lifestyle ranges alongside their audiophile ranges.
Part of it is no doubt that many like tinkering with equipment and systems and the idea of a system speaker would kill a lot of their enjoyment, which I can understand. Part of it may be concern at putting everything into a single basket and worry about what if one of these system speakers goes pop and is out of support. And the magazines and reviewers have spent so many years convincing people that everything should go in a separate box that the idea of replacing a transport, DAC, master clock, pre-amp, twin mono blocs, power supply etc with just a pair of speakers probably seems ridiculous and something only half deaf idiots could ever consider.
Yet for all that I still find it odd that so many of these technologies and ideas which are the norm in the mainstream consumer segment and professional studio segments and which work are still at the margin in the audiophile world.
Especially when some of the wireless speakers are not cheap. I am familiar with the Sonos 5 and Sonos Playbar with the Sonos sub. I have a close friend who has invested heavily in the Sonos system and the Playbar and 5 speakers are genuinely impressive with the sub, and I don't just mean "for a soundbar and wireless speakers" but properly good but if you look at what he must have paid he could have bought some seriously good alternatives so it is not even like the wireless segment exists for cheap skates. Some of the Devialet speakers are very expensive but still appear to sell. And companies like Sonos and Bose are not known for deep discounting or fire sales so there is clearly a large and lucrative market for these systems.

 

[SIY]

I find it odd that the audiophile segment is so conservative.

Well, single-ended direct heated triode amps with 1930s design and performance, horribly colored horn systems, phonographs... I mean, how can you call that conservative? It's cutting edge!

 

[JohnBooty]

Precisely - and some are so much more sophisticated than "hi-fi" speakers, but are crippled by their small size, price constraints and peculiar tuning choices. The natural question to ask is: what if such technology was harnessed in a less compromised form factor? And why hasn't anything like that emerged outside of DD or Kii?

I agree. This is why I was hoping that the Apple HomePod would be a hit. In some ways it's comparable to (a baby version of) the tech in the BeoLab 90s.

Not because it's a product for me, but because there's some geniunely fascinating audio tech in there. Was hoping it was going to be one of those things where Apple truly raised the bar (like they've done with a few product categories over the years) and everybody benefitted in the long run, even if you'd rather die than own one of their products.

I'm still holding onto some slim hope they release a "HomePod XL" with proper midrange drivers, etc.

 

[Juhazi]

I own four KH120s,..
Another KH120 characteristic is port-based cancellation of woofer response at the range of angles which would otherwise cause reflections from a mixing console, and relatively narrow vertical dispersion of the tweeter waveguide serving same purpose..

Wow, that sounds interesting! I can't find anything about that in their material - how does it work?

https://en-de.neumann.com/kh-120-a-g says only that because of front-firing reflex ports the speaker can be positioned in tight places.

 

[Sergei]

Wow, that sounds interesting! I can't find anything about that in their material - how does it work?

https://en-de.neumann.com/kh-120-a-g says only that because of front-firing reflex ports the speaker can be positioned in tight places.

I first saw the explanation in one of the reviews. Official vertical directivity plot corroborates this (bottom of the page https://en-de.neumann.com/kh-120-a-g#technical-data). See how the SPL in the 1KHz - 2 KHz range falls quicker at negative angles than at positive ones. The price paid for this tradeoff is unusually messy frequency response even at moderate negative angles.

 

[jhaider]

Note: never owned KH120s, though I've thought about buying them many times.

When placed farther away, the stereo sweet spot devolves into a sound field that is rather uniformly irradiated from the left and from the right speaker, which creates the sensation of mono-ish sound. Place them right around a typical computer monitor though, and you may be much more delighted.

Do you think with speakers with even wider dispersion (flat baffle waveguides), "the stereo sweet spot devolves into a sound field that is rather uniformly irradiated from the left and from the right speaker, which creates the sensation of mono-ish sound." If not, why does the more constrained treble of the KH120 do so?

Another KH120 characteristic is port-based cancellation of woofer response at the range of angles which would otherwise cause reflections from a mixing console, and relatively narrow vertical dispersion of the tweeter waveguide serving same purpose.

Can you substantiate those claims with their performance as measured compared to other speakers with similar center-to-center spacing? Sound und Recording has published horizontal and vertical polars of a number of speakers (including KH120) under consistent lab conditions.

The measured vertical polar you describe above is just the result of non-concentric drivers through the crossover. The port isn't doing anything at 1-2 kHz.

 

[Sergei]

Do you think with speakers with even wider dispersion (flat baffle waveguides), "the stereo sweet spot devolves into a sound field that is rather uniformly irradiated from the left and from the right speaker, which creates the sensation of mono-ish sound." If not, why does the more constrained treble of the KH120 do so?

I'm not sure that a traditional tweeter placed in a flat baffle would have a wider dispersion. Neumann tweeter has a non-traditional dome shape, then there is a mesh in front of it, and then a rather deep waveguide - quite a few dispersion-affecting elements. I relayed my first-hand experience: KH120 is one of the most purely-near-field monitors I ever used.

Can you substantiate those claims with their performance as measured compared to other speakers with similar center-to-center spacing? Sound und Recording has published horizontal and vertical polars of a number of speakers (including KH120) under consistent lab conditions.

The measured vertical polar you describe above is just the result of non-concentric drivers through the crossover. The port isn't doing anything at 1-2 kHz.

KH310, which I also own, uses either same or very similar tweeter and waveguide, with similar distance between tweeter and woofer centers (~ 2cm difference). See for yourself, the vertical polar plot is quite a bit smoother: https://en-de.neumann.com/kh-310-a#technical-data.

From the first principles of acoustics, of course the ports will affect the radiated sound field. I haven't disassembled KH120, so I don't know precisely how long the ports are, and thus what their phase behavior is depending on frequency, but with sound wavelength at 1 KHz being an order of a third of a meter, the sound field in the 1 KHz to 2KHz range shall be affected asymmetrically by the KH120 asymmetrically placed ports.

 

[q3cpma]

As the KH310 is the model I'm currently eyeing, could I have your opinion? Solely based on measurements, it seems already very good.
The only thing I don't understand is why are they're not using a class D but AB amp in a small sealed enclosure where heat buildup could be a problem.

 

[Sergei]

As the KH310 is the model I'm currently eyeing, could I have your opinion? Solely based on measurements, it seems already very good.
The only thing I don't understand is why are they're not using a class D but AB amp in a small sealed enclosure where heat buildup could be a problem.

I've been using my first pair of KH310A monitors for almost five years now: I obviously like them Like in any design, there are tradeoffs. Two best characteristics are low distortion and accurate transient response. Two worst characteristics are somewhat fuzzy imaging and unimpressive bass extension. I cross them over at 80 Hz to servo-driven subs, so the bass extension is taken care of. I learned to live with their imaging.

KH310A is of course a conservative update of fairly old Klein + Hummel O300 design. Which was excellent to start with. Back then, best class D amps weren't as low-distorting as they are now. The choice of AB was a sensible one. Even though, my impression is that KH310A amps have an unusually high quiescent current (their heat sinks are quite warm in idle state), and thus operate and sound more like class A amps at low output.

Heat buildup isn't really a problem in practice. Their heat sinks are designed properly and are massive enough. I use another pair as mains in a surround system which runs loud at times, and used a pair of them as PA speakers at a party in a rather large hall. Never a problem. Even if you manage to overload or overheat them, their protection mechanisms won't let you damage the transducers or amps.

Fraunhofer agrees that KH310A is excellent.

 

[jhaider]

I'm not sure that a traditional tweeter placed in a flat baffle would have a wider dispersion.
Neumann tweeter has a non-traditional dome shape, then there is a mesh in front of it, and then a rather deep waveguide - quite a few dispersion-affecting elements.

That is wholly incorrect from a technical perspective. A waveguide's dispersion is determined by two factors: diameter and depth. The deeper, the narrower the dispersion. The only waveguide that would have wider dispersion than a flat baffle is a swept back baffle.

Also, the "non-traditional" tweeter is actually a standard Tymphany (Peerless) part. I've held one in my hand. The woofer is, as well.

I relayed my first-hand experience: KH120 is one of the most purely-near-field monitors I ever used.

Your subjective experience is your experience. Nobody's trying to take that away from you. But given that your technical explanation is demonstrably and obviously false, would you mind answering my question as written instead of trying to justify a subjective experience that you have had when it needs no such thing?

KH310, which I also own, uses either same or very similar tweeter and waveguide, with similar distance between tweeter and woofer centers (~ 2cm difference). See for yourself, the vertical polar plot is quite a bit smoother: https://en-de.neumann.com/kh-310-a#technical-data.

Actually, the center-to-center distance matters quite a bit. There's a reason the KH80 has verticals much like the KH310, and other monitors with 5" woofers - JBL with slot port, Focal with PR, and the like - have vertical polars substantially the same as the KH120's.

Again, look at vertical polars for other 5" speakers. The best source I know of is the Sound und Recording monitor special.

From the first principles of acoustics, of course the ports will affect the radiated sound field. I haven't disassembled KH120,

Unlike in some other small monitors (e.g. JBL LSR705i) there is just no evidence of midrange port contamination in the KH120's measurements.

 

[Ilkless]

lAso, the "non-traditional" tweeter is actually a standard Tymphany (Peerless) part. I've held one in my hand. The woofer is, as well.

This is my understanding as well. Really puts lie to the notion that exotic custom-built drivers are what matter the most, when low-diffraction cabinets and dispersion-matching waveguides + crossovers provide more marginal benefit. Look at Dynaudio for instance. Great drivers. But mediocre first-order XOs and typical MDF cabinet unlike the optimised low-diffraction stuff from Neumann or Genelec.

 

[jhaider]

This is my understanding as well. Really puts lie to the notion that exotic custom-built drivers are what matter the most, when low-diffraction cabinets and dispersion-matching waveguides + crossovers provide more marginal benefit. Look at Dynaudio for instance. Great drivers. But mediocre first-order XOs and typical MDF cabinet unlike the optimised low-diffraction stuff from Neumann or Genelec.

Drivers matter too. Per Sound und Recording's interpretation of their measurements, the KH120 is good for 98dB/1m from 50-100Hz (10% THD). The JBL LSR705P, which is proportioned differently but very close in overall cabinet volume, is good for 101dB under the same conditions. The JBL woofer has much more throw than the Peerless woofers used in Neumann and Genelec 5" monitors.

On the flip side, JBL's fancy neo ring radiator compression driver does not give the LSR705P a wideband SPL advantage over the KH120's pedesriran ferrite-magnet dome. The opposite, in fact. S&R rates the KH120 as capable of an average of 104dB from 100-10,000 Hz (3% THD) but the LSR705P as capable of 102dB under the same conditions.

 

[Ilkless]

Drivers matter too. Per Sound und Recording's interpretation of their measurements, the KH120 is good for 98dB/1m from 50-100Hz (10% THD). The JBL LSR705P, which is proportioned differently but very close in overall cabinet volume, is good for 101dB under the same conditions. The JBL woofer has much more throw than the Peerless woofers used in Neumann and Genelec 5" monitors.

On the flip side, JBL's fancy neo ring radiator compression driver does not give the LSR705P a wideband SPL advantage over the KH120's pedesriran ferrite-magnet dome. The opposite, in fact. S&R rates the KH120 as capable of an average of 104dB from 100-10,000 Hz (3% THD) but the LSR705P as capable of 102dB under the same conditions.

Yes, but I was referring to speakers that single-mindedly pursue driver innovations without considering that the limiting factor may not be the drivers beyond a certain point. Dynaudio and ATC are great examples OTOH. Very idiosyncratic XOs that don't even match dispersion well, and a conventional MDF box rather than some low-diffraction design.

 

[Sergei]

That is wholly incorrect from a technical perspective. A waveguide's dispersion is determined by two factors: diameter and depth. The deeper, the narrower the dispersion. The only waveguide that would have wider dispersion than a flat baffle is a swept back baffle.

Are you referring to the "line of sight" directivity principle? Or to the single-mode approximation, exemplified by the Webster Horn Equation? My "I'm not sure" stems from more recent and more accurate approaches, such as Dr Geddes'. Please note what he writes on page 156: "It is interesting to note that the velocity distribution in Fig.6-18 goes well beyond the 30° point on the sphere, which is in stark contrast to the established principle of “line of sight” directivity of a spherical source.".

Your subjective experience is your experience. Nobody's trying to take that away from you. But given that your technical explanation is demonstrably and obviously false, would you mind answering my question as written instead of trying to justify a subjective experience that you have had when it needs no such thing?

False based on the line of sight directivity principle? You do realize that the actual sound field is a scalar function in four-dimensional space (three spacial coordinates + frequency), formed by device with four radiating openings, one of them equipped with mesh + a semblance of phase plug (that small plate in the center of the tweeter mesh) + waveguide, and the other two having irregular form while being attached to internal waveguides of complex form?

It is not easy at all to judge such four-dimensional sound field by a two-dimensional plot. Yet, anyone who has access to KH120 and a piece of music they know by heart can easily verify what I was saying. Start listening with your ears level with the horizontal plane equidistant from the tweeter and woofer centers. Then gradually squat and observe changes in sound. For added effect, move you head left and right while squatting.

Actually, the center-to-center distance matters quite a bit. There's a reason the KH80 has verticals much like the KH310, and other monitors with 5" woofers - JBL with slot port, Focal with PR, and the like - have vertical polars substantially the same as the KH120's.

Again, look at vertical polars for other 5" speakers. The best source I know of is the Sound und Recording monitor special.

Agreed. A similarly-sized two-way monitor with a port opening under the woofer will exhibit qualitatively similar dispersion pattern. As much as I don't find this pattern attractive, such design has its uses: in my case three of the surround speakers had to be placed close to the walls, so the back firing ports or hot back plates weren't acceptable.

Unlike in some other small monitors (e.g. JBL LSR705i) there is just no evidence of midrange port contamination in the KH120's measurements.

I wouldn't call it a "contamination". Just a normal consequence of a design tradeoff. My original response was to those who found KH120 puzzlingly inaccurate while they evaluated it. My experience corroborated this, but only when I listened to KH120 monitors while they were placed too high. After placing and angling them in such a way that the lower "twirly" pattern isn't heard directly, their other advantages more than compensated for this quirk.

 

[Sergei]

Also, the "non-traditional" tweeter is actually a standard Tymphany (Peerless) part. I've held one in my hand. The woofer is, as well.

Would you care to comment on the following? Can you name the Tymphany (Peerless) part numbers? Provide their photos?

From https://www.soundonsound.com/reviews/neumann-kh420:
"Developed with Neumann’s modelling and optimisation tools, the 25mm tweeter is the same as that used in both the KH120 and KH310 monitors".

From https://en-de.neumann.com/product_files/1710/download:
"The 1” tweeter will become the new standard for all new monitors in the KH-series by Neumann. The selection was therefore done extremely carefully using countless prototypes and tests until the desired properties were reached.The final choice was a titanium sandwich cone. Developer Markus Wolff told us that the decision in favour of a metal cone instead of a pure fabric membrane was based on the significantly more pistonic motion of the metal cone.This usually comes with the disadvantage of a pronounced resonance, but this is above 30 kHz and in this case very well damped. Actually a resonance in this frequency range way above the audible spectrum would not be a problem anyhow. But if the resonance is started, it could lead to intermodulation distortion even within the audible frequency range, which makes suppression of the resonance worthwhile. A pure fabric tweeter cone does not have this problem, but would vibrate unevenly way below 20 kHz and therefore would lead to an uncontrollable dispersion behaviour."