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Evidence-based Speaker Designs

QMuse

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Close to the speaker, e.g. 1 metre, preferably with the speaker in the middle of the room. Level depends on what playback level you want to see the figures for, since distortion will increase with level.

Ok, I understand. What would you say is a good value for high quality speakers? Would it be, for example, <0.5% north of 200Hz?
 

tuga

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I'm not finished, point to another science where one single study has been held up as fact? That's not how science works if you want to look at science you can pretty much prove anything or try to prove anything science is a bunch of people trying to prove things it's a battle but eventually there's a consensus.

it's not and never has been one source of information held above all else without any challenge.


The harman research is a factor in audio science but it's not audio science.

Claiming otherwise is basically to form a religion around harming research.

NkkKAyy.gif
 

Jon AA

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Out of interest though, could you be more specific about the kind of felt underlay you're talking about?
This from his book:

CarpetAbsorbption.jpg



Obviously, clipped-pile carpet by itself will have most of its effect in the mid-high frequencies. But with the underlay, you do get some usable absorption in the lower-mid/upper bass frequencies.
 

QMuse

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I just noticed that the speaker is only 0.32m deep. This means that the driver offset is probably 0.2m instead of the previously assumed 0.28m.

If the simulation is corrected with this, the result might reflect your room measurements a bit better.
View attachment 64787

@ctrl , @andreasmaaan , I found the uncorrected measurement, this is where the dip is:

Capture.JPG
 

andreasmaaan

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The Harman search was all about selling speakers into home environments.

That's the dollar they were chasing, not ultimate performance if that was the case the enclosures would have been different and it all would have been different.

I reckon you're right as to their intentions @Thomas savage, but then I also think that if that's the case, they arguably went about it the wrong way, as they did the tests in quite nicely set-up, well-treated rooms, with speakers placed in pretty optimal positions (at least for conventional designs).

If they were looking at speakers that were preferred in typical home environments, wouldn't it have made more sense to set them up in more difficult positions, in less optimal test rooms? More like what Bruel & Kjaer did back in the 70s?

Given what Harman actually did, whether they intended it or not, I think their findings hold weight for people who have well treated, well set-up rooms, i.e. people who have a serious listening room, a home theatre, etc. (That's not to say necessarily they don't also hold for less optimal rooms, too.)

EDIT: removed pics after realising they were of the of the wrong room :facepalm:
 
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ctrl

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@ctrl , @andreasmaaan , I found the uncorrected measurement, this is where the dip is:
You really want to know! ;)

My guess would be that the dip at 750Hz is caused by cancellation due to phase shifting of the rearward offset chassis - that fits the simulation pretty well.

If your measurement without EQ is again valid for 4m listening distance, the dip at 400Hz might be the floor bounce. To be really sure, you would have to change the mirror point of the floor bounce - either with absorbing material or a reflecting surface (e.g. a wooden board).
If the dip disappears or shifts, you have the proof.
1590223591727.png
 

QMuse

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You really want to know! ;)

My guess would be that the dip at 750Hz is caused by cancellation due to phase shifting of the rearward offset chassis - that fits the simulation pretty well.

If your measurement without EQ is again valid for 4m listening distance, the dip at 400Hz might be the floor bounce. To be really sure, you would have to change the mirror point of the floor bounce - either with absorbing material or a reflecting surface (e.g. a wooden board).
If the dip disappears or shifts, you have the proof.
View attachment 64927

Yes, this is the same MMM measurement without EQ done at LP, so 4m.
It may be indeed floor bounce as right channel (blue line) has thick carpet at the mirror point while left channel doesn't, hence the difference.

Once again I thank you for your effort!

I will try to do 40:600Hz IMD distortion from small distance as you suggested. Is there any other frequency pair that is interesting for measuring IMD? Maybe 400:4000Hz?
 

ctrl

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I will try to do 40:600Hz IMD distortion from small distance as you suggested. Is there any other frequency pair that is interesting for measuring IMD? Maybe 400:4000Hz?
First of all, I am not an expert in IMD measurements.
With my DIY speakers I measure IMD with a multitone signal at different sound pressures (85, 95, 105 dB) to see if and at what sound level something unusual happens.
In the current beta version of REW, the signal generator has probably been extended considerably, so that it can generate different multitone signals.
http://www.roomeqwizard.com/betahelp/help_en-GB/html/siggen.html#multitone
So REW should be able to provide the complete range of IMD measurements in the next major version.

With 2-way speakers I also use two-tone measurements to see what happens e.g. with high excursion of the chassis in the area of the chassis surround resonance - depending on the chassis this could happen with e.g. 40Hz/1200Hz excitation.

To find abnormalities I usually use impedance measurement (which the normal hifi enthusiast does not measure) and THD measurements at different sound pressures. If a THD at 800Hz shows an increased HD3, then it's a good idea to look at it with a larger excursion of the chassis and take a two-tone measurement with e.g. 40/800Hz.
 

Darvis

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Changelog
10/5/20 -
Added ME Geithain, Sausalito Audio/Grimani Systems and GGNTKT entry.
28/2/19 - Placed HEDD entry on main list.
6/2/19 - Expanded the Danley entry and placed it in the main list.
2/2/19 - Expanded the Keele/Dayton CBT entry and placed it in the main list.
27/1/19 - Expanded the NHT, Technics SB-C700, KS Digital and Arendal entries. Added the Gradient Audio Finland entry into the main list.
___________________________________--
There is a "State-of-the-art Loudspeakers" thread on this forum already. A slight semantic distinction from that thread and my intention here has to be made from the outset. The focus is not on absolute pinnacle performance from cost-no-object speakers. Instead, I hope to share about more affordable loudspeaker designs and manufacturers that have a demonstrable commitment to releasing evidence-based designs consistent with acoustical physics and psychoacoustics, even if they do not quite reach the levels of unsurpassed excellence often appearing in that other thread. There is a surprising variety of driver configurations and design choices in the list that follows - much more so than proponents of subjective intuition-led audio reproduction often assert when they speak of a "boring" homogeneity/convergence arising from evidence-based audio.

However, the nature of divergence in the loudspeakers I describe here is, in my view, consistent with what one might call a "reasonable pluralism". I will attempt to point out the different priorities of each design and the relative compromises their designers accept. However, what all these designs share is a spirit of progressiveness, advancement and commitment to making rationally-defensible engineering choices - and are most importantly well-priced. From my perspective, it is actually the conventional "hifi" market that is far more homogeneous in its stagnation of design format - think passive flat-baffle "monkey coffins" without any care to match dispersion.

Note: the list is unsorted, work-in-progress (hence the empty entries) and largely stream-of-consciousness for now. If this thread gains traction, I will probably reformat it with a taxonomy based on driver configuration (2-way, 3-way, coaxial etc.) and expand my descriptions. At least one speaker in every listed manufacturer's line has been independently tested to measure well. Special mention has to be given to German magazine Sound and Recording for world-class measurements for several speakers. They deserve all the support we can give for their contributions. You can do so by purchasing a PDF collating measurements of over 80 speakers (mostly active monitors). You can read more about their measurements in this thread.

Neumann - The German studio legend, now under Sennheiser, has a line of active monitors that have impeccable horizontal dispersion (note: refraining from using the more technical term "directivity" in the interests of making this piece accessible). The designs show a clear lineage tracing back to manufacturer Klein+Hummel, which Sennheiser bought over, rebranding their loudspeakers as Neumann products and releasing new designs under the Neumann name. There is existing material on ASR about the importance of at least smooth horizontal dispersion for accurate (and likely preferable) playback from Toole et al.

The Neumanns are perhaps some of the most conventional speakers you will see in this thread. The entire line uses the multi-way non-coaxial driver configuration that dominates audio. However, they use computationally-optimised waveguides (see here for explanation on what a waveguide is, as well as the importance of seamless horizontal dispersion at least) to ensure a seamless transition in dispersion. Tools like computational fluid dynamics have been used to minimise any sort of anomalous movement of air (think port chuffing and baffle diffraction) within the physical limits intrinsic to the size of each speaker. This explains the complex port shapes and seamless baffles (either cast aluminium or polycarbonate) with no edges. Incredibly advanced construction techniques compared to boring old veneered MDF boxes. All their speakers are excellent, but it is the two babies in the line - the KH80DSP and KH120A - that are conspicuous value leaders for their performance level. The KH80DSP is the latest design. It uses a DSP crossover. It has a 4-inch midwoofer, which basically restricts it to very nearfield or desktop use. However, it is perhaps at the absolute limit of loudspeaker engineering for its size. This is a speaker, that when tested independently at a German acoustics lab, achieves a +/-0.6 dB (you read that right) on-axis response out of the box (scroll down for measurements). It is flat to 60Hz and has a -6dB point at 52Hz - great for the size. Distortion is state-of-the-art, which allows maximum SPL to be above 90dB right down to 60Hz. It has linear phase response even at crossover due to the use of FIR filtering. The crossover works in tandem with the waveguide to achieve absolute seamless and uniform horizontal dispersion. It has vertical dispersion as good as possible for a non-coaxial, non-symmetrical driver placement (aided no doubt by tight centre-to-centre spacing made possible with the tiny woofer). All that for $1000 a pair. It is pricey, but (in my reckoning) commensurate with the amount of R&D. Did I mention the hiss (always a complaint against active monitors) of the KH80DSP is not just inaudible in the typical sense of being masked by room noise? No, it was tested at 0dbA/1m - just about the absolute threshold of human hearing acuity under any circumstances. The KH80 upstages its older, larger brother, the KH120A, which is designed similarly (and measures quite similarly), but is "only" +/-1.2dB on-axis, has a bit more vertical lobing due to the larger midbass driver, uses an analog active crossover and doesn't have FIR filtering. Still a very good value as I've outlined. Hopefully a KH120DSP is in the works.

Genelec - A famous name. Much of their product line is like Neumann's. Smooth, seamless low-diffraction enclosures, smooth dispersion for their non-coaxial loudspeaker designs. Neumann is slightly more accurate. Genelec is sold in more places. Here are polar maps of the most common 2-way Genelecs (provided by the company) compared to the Kali LP-6. However, they have released 'The Ones' - comprising the 8331A, 8341A and 8351A in order of size. This uses coaxial driver loaded in a large waveguide, crossed to double oval-shaped woofers that fire out of slots made by the large waveguide and the rest of the cabinet. There is no baffle in the conventional sense to speak of. The entire front of the speaker is a waveguide. Sound and Recording has measured the 8331A and 8351A. At the bottom of this post, I explain the advantages and disadvantages (have edited it from the original for clarity):



Kali - I don't need to introduce them, there is a thread on this forum already. Their story (top designer, blank slate, budget positioning) is well-known, the design well-optimised for its constraints. I have heard reports of both hiss and no hiss. But the acoustic radiation of the speakers is otherwise beyond any reproach for the price and even much more (see my link early in the post about waveguides and dispersion to understand how to read a polar map). There are some minor response anomalies to consider though, like a slightly-depressed treble.

KS Digital - A highly under-the-radar active monitor manufacturer outside of Germany. Their speakers tick a lot of boxes. Coaxial. Sealed. Active DSP with class AB amplifiers. FIR filtering for linear phase at crossover. Aluminium enclosures (with hardwood trim). German-made even. All that for around KEF LS50 passive pricing. Scarcely believable, right? The model I'm referring to, the C5 Reference, uses a 6.5-inch SEAS Prestige coaxial driver imported from Norway. This entry is special, because it is the C5 Reference inspired this thread. Sound and Recording measurements here.

It has some issues but there is, as I wrote, a broader significance to this product:



KSD also has a newer line that load the coaxial tweeter in a rigid waveguide, reminiscent of Presonus and the old Altec coaxials. I have not seen detailed measurements or indeed much information at all about it.

NHT - I think their fairly long history means they should really be in the "usual suspects" section below. However, the brand was in the woods for a short span in the 2000s, before re-emerging with a direct-sale model. They also seem to have a mediocre reputation among pure subjective audiophiles for their ho-hum Chinese OEM provenance, nondescript aesthetic and association with home theatre (all of which do not predict any acoustic property of their speaker design).

Their speakers are highly well-designed across the entire line and (in a welcome departure) sealed. The idea of a well-engineered flat-baffle 3-way is to offer near-seamless dispersion wider than a waveguide speaker. Waveguides narrow dispersion to help achieve a seamless transition between drivers with a large disparity in radiating diameter. The larger driver's dispersion gradually narrows with higher frequency (and shorter wavelength). Sound path length differences between different points of the radiating surface at HF become significant relative to the wavelength of the frequencies in question.

This necessarily entails acoustic interference (due to the addition and subtraction of out-of-phase signals) that accumulate into highly-attenuated SPL at oblique angles compared to on-axis - ie. a narrowing of the net acoustic radiation a.k.a dispersion with increasing frequency. A flat-baffle 3-way with carefully chosen driver diameters splits the difference so the dispersion mismatch is small enough to be almost eliminated (at least on the horizontal plane of the design axis) through optimising driver placement and crossover topology. This is evident in the NHT C3, as well as the Philharmonic BMR.

What of flat-baffle 2-ways? The mismatch in dispersion is very large, and minimising it requires crossing tweeters lower and woofers higher than they'd be comfortable with in virtually all circumstances.

Arendal Sound - Another direct-sale Scandinavian brand, but Arendal hails from Norway instead of Sweden like XTZ. They sell a line of high-SPL speakers, . They provide on-axis and off-axis curves as well as impedance response. Drivers are integrated well with a deep waveguide and good crossover. That sort of waveguide promises narrower dispersion but higher SPL capability (together with what look like beefy woofers), which is good perhaps for rooms with harsh specular early reflections from sidewalls. Unfortunately we don't know what smoothing technique they used for the curve, but the graphs don't seem excessively-smoothed.

Technics - The venerable brand's return to high-performance audio was muted, not least because What Hi-Fi gave a two-star review for their coaxial SB-C700 that has no basis in empirical reality. I will not dignify that site with a direct link on my pose. Stereophile measured them. These are way better designed than the LS50 passive. LS50 has shelved up response (+3dB within the listening window per NRC measurements at Soundstage Network) from 2-5kHz. That's stupidly bright. Its the result of a dispersion mismatch at the crossover frequency - rather ironic because coaxials provide a better basis for smooth-dispersing speakers to be engineered. In contrast, the SB-C700 is totally seamless in dispersion and flat throughout the crossover range. Going by raw driver performance, the Technics is only very slightly behind the Genelec seamless coaxial that covers the midrange up and the KEF Uni-Q. As a complete speaker, the SB-C700 leaves the LS50 (and the other 2-way KEF coaxs without a separate woofer) in the dust. In fact it is to my knowledge, the best implementation of a pure 2-way coaxial, despite using a passive crossover. It extends cleanly (see distortion measurements in the third pic of the first post) right down to its 48Hz tuning frequency, giving up little in bass performance to a non-coaxial midwoofer of similar size.

The "peaks and dips" are mostly artifacts of the normalisation technique as mentioned in the KS Digital entry. Also the midwoofers are much larger (6.5-inch vs 5.25 for LS50), which means more headroom and bass extension. In my opinion their white low-diffraction curved enclosures and flat aluminium honeycomb midwoofer look a damn sight better than the LS50's industrial design too.

Gradient Audio Finland - Read up on Jorma Salmi's contributions to audio engineering, talking about his wide-ranging research publications would be beyond the scope of this thread. Suffice to say he, like Siegfried Linkwitz, was concerned about room-agnostic performance and optimising designs using both in-room measurements and a solid foundation in engineering. To this end, Gradient's top offerings are dedicated to exotic driver configurations that achieve unconventional polar patterns like cardioid, dipole or a mix of both. All their speakers are built in Finland using birch ply. Their entry-level offerings are the Gradient Five standmount and Gradient Six standmount, both of which using SEAS coaxials customised to their specs and passive radiator bass loading. I have no measurements and only an useless subjective report that they did not sound severely coloured in my experience and were enjoyable on and off-axis. Their flagship, the Revolution mixes cardioid (in the midrange below baffle step), dipolar (in the bass) and monopolar (in the treble) radiation. They use dual 12-inch woofers mated to a coaxial acting as MF/HF. The 1997 version of the speaker is exemplary for its era and still good by today's standards. It has been incrementally-revised to keep up with driver and active crossover advances of course. The Revolution now is not that of 1997. The Five and Six use the same coaxial as the current Revolution, except those are used "full-range".

Note that even way back then, the custom coaxial they specced does not have any major on-axis dips below 10kHz, and only one at 16kHz, which is more than can be said for some coaxial drivers today (not that it should be a problem IF it fills in immediately off-axis). The in-room response John Atkinson measured falls within +/-1.3dB at 1/3-octave, one of the best results Atkinson ever measured. Robert E. Greene of The Absolute Sound reports similarly in his own room.

Constant Beamwidth Transducers (Dayton/DB Keele) - There are two CBTs you can buy as manufactured products: the CBT36 kit and the CBT24 kit/complete speaker, both offered by Dayton. The CBT24 is on sale for $1495/pr as of February 2, 2019. For mini-monitor money, you can get a bleeding-edge driver array, albeit limited by driver performance. I would personally love to see someone stick in Vifa TG9s or some other widebander with smoother dispersion and FR. Rick Craig of Selah Audio also does custom CBT work at a much higher price range. The CBT isn't a line array. Despite its looks it is as far as one can get from a line source. The curvature and gradually-decreasing SPL (called "shading") emitted by drivers as one moves up the array come together - as someone described brilliantly on DIYAudio - a "slice" (like an orange) of the wavefront of a perfect point source placed on the ground plane. Project an imaginary line backwards from each driver at the angle at which the driver is pivoted. Do you see the slice of a sphere now? Exceptionally uniform coverage both vertically and horizontally. No floor bounce because the speaker is on the ground plane. Floyd Toole mused that it could be the "perfect" surround loudspeaker due to the uniformity of coverage allowing similar sound over a larger seating area. There is more discussion on another ASR thread.

Note that the CBTs will require subs and ideally DSP to equalise driver response. Don Keele (ex-JBL, designer of the JBL biradials before the CBT array for audio) has an excellent lecture series that examines the properties of CBTs:


Danley - Tom Danley was instrumental to popularising and improving the multiple-entry horn, through the Unity and Synergy horn designs. The designs allow point-source dispersion, without vertical lobing, yet also without the SPL limitations of direct-radiating coaxial drivers. Instead, Danley would load drivers, each firing from a different aperture along the sides of a horn with a single exit point. The spacing between apertures (and hence drivers that were mounted into it) were calculated to approach a quarter wavelength of the crossover frequency. This is to promote optimal driver summation, such that the wavefronts of drivers playing different frequency ranges (woofer, midrange and tweeter) do not destructively interfere with each other within the horn, and instead can be directed outwards smoothly, without major FR discontinuities. Anecdotally, the Synergy horns have drivers so well-integrated that one could stick their head into the horn and still not hear any significant interference between the drivers.

By optimising the driver configuration, crossover and placement, the Danley horns are coaxial, have immense SPL capability and offer very controlled directivity. Moreover the Synergy horns are linear-phase and have relatively flat frequency response. A critique of these horns (regardless of multiple-entry or otherwise) is the diffraction that they introduce due to their relatively sharp edges and straight sides, which have been maligned by researchers such as Earl Geddes as the source of the stereotypical horn "honk" (see page 8 onwards of the linked PDF), even if the FR does not seem to imply that much roughness or brightness.

The alternative per Geddes is a highly-contoured "waveguide" with a minimal amount of sharp edges that focuses purely on having smooth dispersion that gradually fades away outside of its optimal zone. In contrast, horns like the Synergy aim for a dispersion pattern with sharply-defined borders (because of the high-end sound reinforcement applications Danley had in mind, which require ensuring that the Synergies would have a sharply-defined guaranteed-linear coverage within a stipulated area for say, concerts). Think having a blurry, smooth border of constant width versus a border created with a sharp, straight line. A matter of priorities and reasonable tradeoffs between both methods, which captures the spirit of this thread. Here is a comprehensive video of the acoustics behind the Synergy design that might do better than words in explaining how much different it is from the typical loudspeaker we see:


HEDD - ADAM's co-founder starts a new firm. AMT active monitors, all assembled in Berlin (starting to see a German slant here...). More expensive than ADAMs of a similar design made offshore (T5V and T7V). Originally, the only third-party measurements I could find were from Russian sources with measuring conditions I'm not so sure of. I have since found a detailed teardown from Italy, which shows the HEDD Type 05 uses an asymmetric analog active crossover with 6th and 8th-order Butterworth crossover slopes. ICEPower modules (which have detailed AP measurements from B&O datasheets) are indeed used. The midwoofer is beefy too, with a cast frame. FR is fairly wavy, at +/- 2dB, despite the sophisticated crossover, but they have a DSP plugin (HEDD Lineariser) to linearise phase and FR. Arguably, its net effect is similar to that of a DSP crossover without incurring an AD/DA conversion should you be using a computer as source. The only thing this upstream DSP cannot correct is the narrow-band off-axis flare centred at 3.5kHz. Add-on support for either Ravenna or Dante is available through slot-in modules. Clever I think. Trivial to add a card if either protocol takes off, but one isn't left with a white elephant if it doesn't.

ME Geithain - ME Geithain has had a cult following in studio circles for the last 2 decades, with a small following of diehard followers that proclaim it to be at or near the pinnacle of active loudspeaker engineering. The German pro audio manufacturer's offerings are coaxial and active. Models designated with a 'K' suffix are cardioid. They provide datasheets with rudimentary on and off-axis measurements, and Sound And Recording magazine has measured their speakers in further detail before. The cardioid dispersion uses a passive approach, a complex internal cabinet that allows delayed back radiation from the driver to emit from carefully-calculated slots that induce destructive interference. This is a contrast to DSP beamforming with electronics (Kii Three) and hybrid approaches with both DSP and slots (DD 8C). With proprietary coaxial driver assemblies involving MF/HF drivers suspended in front of woofers on driver grilles (as opposed to mounted within), rare cardioid enclosure construction and German manufacturing, MEG speakers are often priced at the top-end of their size class. For instance, the RL-906 workhorse, which is in a similar form factor as the likes of Genelec's 8030 and Neumann's KH120, costs nearly 2,600€ per pair. The cheapest cardioid offering is over 8,000 per pair, utilising a 10" woofer and a 3-tweeter array mounted in front it. Although the cardioid configuration works as advertised (especially on larger mid-field offerings with a wider baffle), considerations include the likelihood of diffraction around the sub-assemblies and relatively ragged response of the cardioid.

Sausalito Audio/Grimani Systems - Audio engineer Manny LaCarrubba designed a novel acoustic lens under his then-company Sausalito Audio Works. It was licensed by B&O and put into several iconic designs, such as the Beolab 5, as well as in the Audi A8. The lens was further developed as the Conic Section Array (CSA) lens under a new company, Sausalito Audio. The CSA be licensed for anyone so inclined. The company has not been shy with measurements, showing Spinorama-style graphs (data is anechoic >500Hz) of CSA designs in various form factors, including the Grimani Systems Alpha. Grimani was co-founded by LaCarrubba with two associates, with an entire lineup of speakers using the CSA targeted at the high-end HT/installation market. Despite the relative obscurity of the CSA design in the stereo market, the Spinorama shows remarkably constant and wide directivity, with HF power response being almost exactly the same as on-axis/listening window, while maintaining a smooth response. Unfortunately, the cost of entry for free-standing CSA-based loudspeakers are expensive; the cheapest is the Grimani Tau, which is a $9000/pair active floorstander with dual 6.5" woofers. However, the Sausalito Audio page shows a proof-of-concept prototype of a 6" woofer + CSA waveguide standmounter with good spins, keeping hopes for a compact and hopefully more affordable standmount alive.

Moreover, Sausalito Audio should also be applauded for releasing spinorama measurements of consumer smart speakers. They released spinorama data of the Apple Homepod and Sonus Play One. Both measure excellently, in an indictment of the conventional hifi market. There is absolutely unfathomable amount of R&D thrown at such speakers to overcome the severe form factor and cost constraints. The economies of scale to manufacture these sophisticated designs cost-effectively are immense. Wilson and Devore need not compare. 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? But we digress - Sausalito has done the community a great service in providing evidence to raise these questions, and help us hold loudspeaker manufacturers to a higher standard.

GGNTKT - Startup German brand GGNTKT (from the German word "Gegentakt" - "push-pull" - with the vowels removed) released their Model M1, a wide-format 2-way sealed active speaker with DSP-based cardioid radiation (through 2 rear woofers) and a large, computationally-optimised waveguide tweeter that appears to use a variation of the diffraction-blending waveguide geometry popularised by the JBL M2. The GGNTKT M1 shows excellent measured performance, as seen in the detailed spec sheet with polar maps and off-axis curves. Directivity control down to 200Hz is demonstrably achieved through a combination of wide baffle and beamforming DSP with the rear woofers, representing a twist on the progressive style of beamforming speaker design first pioneered by Kii, then DD. Power amplification is achieved with Pascal modules. (thanks to @q3cpmafor the reminder)

<<<<<<<<<<<<<<<<Entries below are work-in-progress>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Merovinger - Custom installer from Germany with a DSP coaxial speaker using an air-motion transformer tweeter. I know the Fluid Audio FPX7 does so too, but the DSP for Merovinger seems more extensive. It is used to linearise both phase and FR, as well as time-align. Need to do more research on these. Intriguing.

ABACUS Electronics - Germany again. Active speakers, preamps, power amps and streamers with built-in Acourate functionality. However, speaker measurements are limited to only one out-of-production model (on German magazine AUDIO). Nonetheless, rudimentary measurement of their proprietary class AB amp modules suggest incredibly low output impedance, that might bode well for overall engineering.

The usual suspects (residual category for evidence-based brands that seem to be well-known, so I'll get to them last or simply leave this list unelaborated. Lots of information available from a Google search anyway) - Salk, Philharmonic, ELAC, Ascend, Selah, Seaton Sound, PSB, B&O, Revel, JBL (LSR and Synthesis), ADAM, Buchardt Audio, Vanatoo
Pylon could be one of them, worth of investigation at least. It's a relatively new (2011) manufacturer based in Poland. I intend to listen to some of their speakers and, hopefully, compare them to things I know. http://www.pylonaudio.com/
 

Duke

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Would AudioKinesis fit the bill?

They now "outsource" their speakers but still make the Swarm subwoofer mesh:

http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html

https://jamesromeyn.com/audiokinesis-speaker-design/#philosophy

Regarding the apparent "outsourcing", my partner Jim Romeyn lives close enough to my old cabinetmaker that he has been working directly with him on our latest round of products. Jim also has a suitable demo facility in his home while I do not. I'm the guy in the lab coat, but Jim has contributed some extremely valuable ideas.

I am aware of AudioKinesis from Audiocircle but I haven't been able to find detailed measurements to verify their performance. Hence, I haven't added them yet. Promising though, with the recognition of multisubs and directivity control. Also one of only two companies I know selling fully-built speakers with the SEOS waveguide.

I don't publish my measurements, sorry. I follow the measurement protocol Earl Geddes taught me (you can see me next to Earl in one of the photos in post 1223, and I was his behind-the-curtains speaker-shuffler at the blind listening test in the other photo). I routinely generate time-gated data down low enough for my crossover design work, but not low enough if the goal is to "show off". Maybe one of these days I'll rent a big space. My current designs include a (user-adjustable) additional set of directional drivers dedicated to the reverberant field, so the off-axis response of my main array wouldn't tell the whole story anyway. The frequency response of those additional drivers is a trade secret, but (among other things) they improve the spectral balance of the reverberant field beyond what the off-axis response of the main array does all by itself, without contributing any undesirable early reflections.

So, what I do is conceptually science-y, but controversial. In fact the psychoacoustician I draw from the most (David Griesinger) studies concert halls, not home audio. I might be able to talk a good game but I don't have proof, and I understand that this forum is about what can be proven.

We did have one of Harmon's [oops - "Harman's"] trained listeners spend some time in our room at T.H.E. Show 2019, and he said some nice things, so we THINK we might be barking up some of the right trees. But then so does every other speaker designer, be they professional or amateur or armchair.

Who is that other company using SEOS waveguides? Whoever they are, I tip my virtual hat to them. I have tried just about everything on the market that looks remotely promising, and the SEOS waveguides are imo the best off-the-shelf horns or waveguides currently available, if constant directivity without relying on diffraction is the priority. Recently I've started designing my own Oblate Spheroid waveguides, and we'll be trending more in that direction in the future.
 
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Duke

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Sounds are never, and hear I mean literally never, composed mainly of harmonics. :D

Well... I'm not so sure about that.

I design speakers for bass players, and the fundamentals of the lowest notes are much weaker than the first overtone, to the extent that very few bass rigs even try to amplify the lowest fundamentals. My bass cabs don't because the penalties in size and/or efficiency are prohibitive - I target the first overtone of whatever the lowest note is (usually low-B). To the best of my knowledge Acme is the only bass cab manufacturer that really delivers full-power fundamentals of the lowest notes.

Once an electric piano player asked me to come up with a cab for him to gig with. I looked at the spectrum of the lowest piano notes to figure out where the goal posts are. The fundamental of low-A (27 Hz) is so weak as to be effectively inaudible. So is the first overtone. It is not until the second overtone (81 Hz) that the energy is loud enough to be worth amplifying. Anyway I found that the lowest frequency signal from a piano that is arguably worth amplifiying is the 62 Hz first overtone of low-B. (Thus the low-end "goal posts" are sort of in the same place as for electric bass, except that the linear excursion requirements are much greater for a plucked electric bass string to prevent "fart-out".)

So for the lowest notes of at least some instruments, the fundamentals are too weak to matter. The ear/brain system recognizes the overtone structure and fills in the missing fundamental.
 
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thewas

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We did have one of Harmon's trained listeners
Sorry for the off topic parenthesis, but as a non native English speaker I keep wondering why so many people write Harmon instead of Harman in this forum, is it a kind of old joke or word play and if yes, could please someone explain it?
 

Duke

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Sorry for the off topic parenthesis, but as a non native English speaker I keep wondering why so many people write Harmon instead of Harman in this forum, is it a kind of old joke or word play and if yes, could please someone explain it?

Oops. My mistake! For some reason in my mind I hear "Harmon" instead of "Harman", and obviously I haven't learned the correct spelling. I tip my virtual hat to you, my non-native-English-speaking friend, for schooling me in my own language.

So if there's a joke there, it's on me - you know my language better than I do!
 

thewas

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Thank you and no jokes on you either for your kind and sincere reply. :)
By the way I had also considered that it is an auto-correct thing, but had looked it up and it didn't really gave a frequently used term https://en.wikipedia.org/wiki/Harmon
 
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I don't publish my measurements, sorry. I follow the measurement protocol Earl Geddes taught me (you can see me next to Earl in one of the photos in post 1223, and I was his behind-the-curtains speaker-shuffler at the blind listening test in the other photo). I routinely generate time-gated data down low enough for my crossover design work, but not low enough if the goal is to "show off". Maybe one of these days I'll rent a big space. My current designs include a (user-adjustable) additional set of directional drivers dedicated to the reverberant field, so the off-axis response of my main array wouldn't tell the whole story anyway. The frequency response of those additional drivers is a trade secret, but (among other things) they improve the spectral balance of the reverberant field beyond what the off-axis response of the main array does all by itself, without contributing any undesirable early reflections.

So, what I do is conceptually science-y, but controversial. In fact the psychoacoustician I draw from the most (David Griesinger) studies concert halls, not home audio. I might be able to talk a good game but I don't have proof, and I understand that this forum is about what can be proven.

Who is that other company using SEOS waveguides? Whoever they are, I tip my virtual hat to them. I have tried just about everything on the market that looks remotely promising, and the SEOS waveguides are imo the best off-the-shelf horns or waveguides currently available, if constant directivity without relying on diffraction is the priority. Recently I've started designing my own Oblate Spheroid waveguides, and we'll be trending more in that direction in the future.

Hi Duke,

I admire your commitment to accurate data - that is an entirely fair concern, especially since Amir's system has started to show that bass response can deviate substantially even between different anechoic chambers. Perhaps one of these days you or an owner could send something to Amir to measure.

I follow David's work as well - in fact, I refer to his work in some detail in an article I wrote on psychoacoustics. I'm glad that someone has synthesised the insights of Earl and David in a way that seems rational.

As for the other company, it's hORNS from Poland. Unfortunately their speakers appear quite a lot more expensive than your offering.
 

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Is a one-piece curved ribbon with smoothly decreasing drive level (eg. through the physical design of the motor) feasible as an extreme implementation?

I hope you don't mind me going back and responding to old posts here and there as I slowly wade through this thread...

Imo what you describe could be done with a faceted curve, but it would be a major challenge with a continuous curve, assuming the continuously curved diaphragm could be suspended properly.

The issue is this: You can think of a continuous curve as section of the surface of an expanding cylinder. As the diaphragm moves forward, it gets tensioned. As it moves backwards, that tension is relaxed. The tensioning in particular puts a lot of stress on the diaphragm.

This is one of the challenges Martin Logan faced with the continuously-curved diaphragms of their electrostatic speakers, particularly the fullrange CLS model. Their solution was to use a very tough diaphragm material, the downside being that it was relatively thick and heavy, compared to competitors who used flat-panel electrostats. And even with this extra-tough diaphragm material, one failure mode of the CLS when pushed too hard for too long was a cracked diaphragm.

In contast SoundLab went with a faceted-curved geometry, using a single large diaphragm clamped (between foam) at regular intervals (a least horizontally, the plane in which it was curved), with the angle between facets being small enough to effectively provide continuous coverage at short wavelengths without "picket fence" effects. This more benign geometry allows them to get away with using a much thinner diaphragm material.

Imo the faceted-curved geometry would be the more promising for a tall curved constant-beamwidth ribbon transducer.
 
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Duke

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Perhaps one of these days you or an owner could send something to Amir to measure.

I didn't realize Amir was able to do speaker measurements... haven't kept up with developments here.

Right now I am doing some product development work, "evolving" in a particular direction. Once I'm reasonably satisfied that the evolution has run its course (and assuming we're satisfied with the results), I would DEFINITELY be interested in exploring the possibility of independent measurements.

As for the other company, it's hORNS from Poland. Unfortunately their speakers appear quite a lot more expensive than your offering.

Of course - I should have known! I once came thiiiiiis close to ordering a dozen or so 18" fiberglass SEOS waveguides... instead decided that the thing to do was make my own Oblate Spheroids. Easier said than done. Figuring out the best manufacturing technique for our situation, then working out the specifics, has taken a long time. We just took delivery of some custom tooling last week, so there is light at the end of the tunnel.

I follow David [Griesinger]'s work as well - in fact, I refer to his work in some detail in an article I wrote on psychoacoustics. I'm glad that someone has synthesised the insights of Earl and David in a way that seems rational.

Excellent article - very educational and enjoyable! Definitely stretched my brain but didn't quite snap it. I'm not much of a headphone guy but have watched David's headphone calibration video, so I was waiting for that to show up in your article. I watch pretty much anything David has uploaded because every now and then he drops little nuggets of unique insight which are applicable to home-audio loudspeaker design, in my opinion anyway.

Informed by (my interpretation of) some of David's ideas, I hope one of my forthcoming designs will compete sonically with the latest version of the hORNS Universum. But I don't have a chance of competing aesthetically... the Universum would be completely at home in a museum of modern art.
 
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I didn't realize Amir was able to do speaker measurements... haven't kept up with developments here.

Right now I am doing some product development work, "evolving" in a particular direction. Once I'm reasonably satisfied that the evolution has run its course (and assuming we're satisfied with the results), I would DEFINITELY be interested in exploring the possibility of independent measurements.

Of course - I should have known! I once came thiiiiiis close to ordering a dozen or so 18" fiberglass SEOS waveguides... instead decided that the thing to do was make my own Oblate Spheroids. Easier said than done. Figuring out the best manufacturing technique for our situation, then working out the specifics, has taken a long time. We just took delivery of some custom tooling last week, so there is light at the end of the tunnel.

Excellent article - very educational and enjoyable! Definitely stretched my brain but didn't quite snap it. I'm not much of a headphone guy but have watched David's headphone calibration video, so I was waiting for that to show up in your article. I watch pretty much anything David has uploaded because every now and then he drops little nuggets of unique insight which are applicable to home-audio loudspeaker design, in my opinion anyway.

Informed by (my interpretation of) some of David's ideas, I hope one of my forthcoming designs will compete sonically with the latest version of the hORNS Universum. But I don't have a chance of competing aesthetically... the Universum would be completely at home in a museum of modern art.

Hi Duke,

Yes, Amir bought a very sophisticated measurement setup that allows full-range anechoic measurements without gating in a typical room. Here are example measurements. There have been some slight teething issues (as expected with such an advanced rig), but many users smarter than me have helped Amir troubleshoot the issues very effectively and they are largely ironed out.

Earl's website mentions that someone is "preparing" to make speakers from his product line. Would that be you by any chance? Would you be able to use Earl's foam plug?

I can't wait to see what you have in store for a massive waveguide design. Modern compression drivers and low-diffraction waveguides have come a long way, and the market sadly hasn't really caught up.
 
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