Sonus Faber Aida loudspeaker Measurements

Sidebar 3: Measurements

As the Aida weighs a backbreaking 364 lb, I drove my test gear to Mikey Fremer's place to measure the speakers in situ. After I'd done the in-room measurements, my plan was to perform the quasi-anechoic measurements in Mikey's driveway. Sonus Faber's reps had placed one of the speakers on a wheeled dolly and rolled it from the listening room to the garage. However, for the first day in weeks, it was raining, and with no end to the downpour in sight, I ended up measuring the Aida in the garage with the door open. I could position the speaker well away from the sidewalls, but reflections of its output from the ceiling and floor limited the anechoic time window used for the analysis to 3ms, which reduces the measurements' resolution in the midrange. I didn't measure the Aida's output to its rear, but the High, Low, and Depth controls were left set to the positions MF had used.

As usual, I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Sonus Faber Aida's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. The Aida's voltage sensitivity is specified as 92dB/2.83V/m; my B-weighted estimate was a little lower, at 90.5dB/2.83V/m, but this is still high. Specified as a nominal 4 ohm load, the Sonus Faber's impedance remains below 6 ohms over the entire audioband (fig.1), with minimum magnitudes of 2.23 ohms at 35Hz and 2.33 ohms between 11.3 and 14kHz. Although the electrical phase angle remains low, the Aida will need to be partnered with an amplifier capable of supplying a lot of current.

The traces in fig.1 are free from the small wrinkles that would imply the presence of cabinet-wall resonances, but when I reached for my accelerometer to investigate the enclosure's vibrational behavior, I found that its preamplifier wasn't working—and my tool kit was 45 miles away. I listened to the enclosure with a stethoscope while it played pink noise and found it relatively inert.


Fig.1 Sonus Faber Aida, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The impedance traces are difficult to interpret with respect to the tuning of the woofers and subwoofer. In addition, there is always the possibility of crosstalk between the low-frequency radiators when I perform nearfield measurements. Nevertheless, there was a null at 33Hz in the front-facing woofers' nearfield responses, which suggests that this is the tuning frequency of the two vertical slot ports on the enclosure's rear. The woofers themselves have slightly different responses, the lower woofer rolling off a little earlier in the midrange than the upper. The complex sum of the outputs of the two woofers and their ports, measured in the nearfield and taking into account acoustic phase and the different distances from a nominal farfield microphone position, is shown in fig.2 (red trace). It peaks broadly between 30 and 120Hz, and the upper-frequency rolloff is free from any resonant spikes. I haven't shown in this graph the nearfield output of the downward-firing subwoofer—it was undoubtedly affected by crosstalk from the front-firing woofers—but it appears to reinforce the Aida's low-frequency response to a true 20Hz.


Fig.2 Sonus Faber Aida, anechoic response of midrange unit and tweeter averaged across 30° horizontal window centered on tweeter axis at 50" and corrected for microphone response (blue), with nearfield response of midrange unit (blue) and complex sum of nearfield responses of front-firing woofers and their ports (red), respectively plotted below 300Hz and 900Hz.

The blue trace below 300Hz in fig.2 shows the nearfield output of the midrange unit; above that frequency, it shows the farfield response of the midrange unit and tweeter averaged across a 30° horizontal window centered on the listening axis. The Sonus Faber's response is impressively flat, other than a small plateau in energy in the top octave. As shown by the plot of the Aida's lateral dispersion, normalized to the tweeter-axis response (fig.3), this plateau will compensate for the fact that the tweeter starts to become directional above 7kHz, which would otherwise make the speaker sound a bit lacking in top-octave air in large or overdamped rooms. In the vertical plane (fig.4), the Aida maintains its even tweeter-axis response for up to 10° below that axis, which is just as well given that the tweeter is 48" above the ground.


Fig.3 Sonus Faber Aida, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.


Fig.4 Sonus Faber Aida, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–10° below axis.

MF's reference is the Wilson Audio Alexx, which he reviewed in May 2017. Fig.5 compares the spatially averaged response in his room of the Sonus Fabers (red trace) and the Wilsons (blue). (The traces were generated by averaging 20 1/6-octave–smoothed spectra, taken for the left and right speakers individually using SMUGSoftware's FuzzMeasure 3.0 program and a 96kHz sample rate, in a vertical rectangular grid 36" wide by 18" high and centered on the positions of MF's ears.) The two speakers appear to have broadly similar responses below 300Hz, where the spatial averaging has not eliminated major room-acoustic issues. Both speakers offer effective output to 20Hz, but the Wilsons have a little more output below 20Hz, if that matters. The Sonus Fabers have a little more midrange energy than the Wilsons and a little less presence-region energy, but of more subjective significance is how smooth and even the Aida's in-room response is throughout the midrange and treble. The output smoothly slopes down by about 5dB from 400Hz to 18kHz, which is almost exactly the in-room behavior you need from a pair of speakers for them to sound flat. Certainly in my own auditioning of the Aidas when I visited Mikey, the sound quality was as superb as this graph implies. Incidentally, the individual measured responses of the left and right speakers at the listening position indicated superb pair matching, the two outputs matching within 0.5dB from 600Hz to 8kHz.


Fig.5 Sonus Faber Aida, spatially averaged, 1/6 -octave response in MF's listening room (red); and of Wilson Audio Alexx (blue).

In the time domain, the Aida's step response on the tweeter axis is shown in fig.6; it reveals that the tweeter and midrange unit are connected in positive acoustic polarity, with the tweeter's output arriving at the microphone before that of the woofer. The woofers are all connected in inverted acoustic polarity, but the beginning of their step is smoothly integrated with the decay of the midrange step, implying optimal crossover implementation. The same is true for the time-domain integration of the tweeter and midrange outputs. The Sonus Faber's cumulative spectral-decay plot is very clean (fig.7).


Fig.6 Sonus Faber Aida, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).


Fig.7 Sonus Faber Aida, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

The excellent measured performance of Sonus Faber's Aida indicates that some serious engineering talent was involved in its design.—John Atkinson

Sonus Faber
US distributor: Sumiko
2431 Fifth Street
Berkeley, CA 94710
(510) 843-4500

retro's picture

So a $130,000 loudspeaker can "fart"..? I'm sorry, but this just explains what's wrong in high-end audio these days. I began my journey into truthful audio reproduction in the eighties, not being impressed by the acronyms of the day, only interested in the sound that caught my ears. You guys apparently always get so excited to review a 6-figure product that you seem to forget about being objective.. This is still a MDF box with some drivers. Cabinet is not made of gold. Drivers are not beryllium, or even diamond. This industry has gone sick. I'm sure they will sell, but not because they sound good (which I'm sure they do, BTW), but because they are an ultra expensive add-on to your lifestyle. Like a Rolex, although without diamonds....
If something TRULY comes along as being groundbreaking and advancing the technology, sure, slap a high price tag on it. An example, Bang & Olufsen Beolab 90? At a lower, reasonable price point, maybe the Kii..??
But this....

Michael Fremer's picture

The speaker didn't "fart". The word was used by a CONDUCTOR to describe a particular confluence of instruments in Beethoven's SCORE.

What's wrong with high end audio "these days" are people who can't read with comprehension, or are so busy grinding axes, they read what they wish to read and not what's in the words written.

YOU are the one not being objective. But you are objectionable.

retro's picture

The "fart" thing was of course a joke from my side..
I assumed most people understood that.

As for the rest of my comments, I stand behind them 100%.

Indydan's picture

But, if the speaker did fart, it would surely produce a warm sound.

jeffhenning's picture

It's no surprise that a $130K speaker sounds really good. So what? Yes, it's beautiful and, again, so what?

The real test is whether it's worth the asking price. Is it? Not from what I can ascertain from this review.

The future is Kii (as previously posted), Legacy, may be B&O (if their stuff isn't too crazy or crazy expensive) and KEF if they make something bigger than the LS50 Wireless that has all that goodness. And any forward thinking company like them.

At this point in time, it's absurd that people are hanging on to moderately updated tech from 50 to 100 years ago.

The future of the speaker industry is DSP. Bruno Putzeys stated that the reason he started Kii Audio was that he felt that amp tech had hit a point of very diminishing returns, but that speakers had not seen the revolution that had been made with amps.

DEQX, Dirac and Audessy have been sounding the call for DSP for a while. And when you have a fully DSP'd speaker that has an amp for every driver, you can achieve something close to perfection.

The industry, for the most part, though, is holding on to the past. And I mean all of the industry (this site, too).

Case in point: you are playing the vinyl release of a high resolution digital recording to review these speakers. That's like taking a Blu-ray disc, recording it to VHS and, then, viewing it on a new hi-def TV.

It's nonsensical.

Just like these huge, incredibly heavy speakers.

Bogolu Haranath's picture

The new KEF LS-50 Nocturnes use built-in DSP ......... Genelec studio monitors have been using built-in DSP for some time ........ Also, the new smart speakers like HomePod, Google Home Max etc. have built-in DSP .......... More of these types of speakers are gonna be coming out ..........

Bogolu Haranath's picture

May be Stereophile could review the Kii Three powered book-shelf speakers, with built-in DSP? :-) ........

tonykaz's picture

KR reviewed the Kii, they're rather pricy but wonderful.

Tony in Michigan

Michael Fremer's picture

Some new cars.

Robin Landseadel's picture

Works for Jeff Dorgay.

Indydan's picture

Dorgay, the guy who doesn't know how an RSS feed works...

supamark's picture

That's Ken Pohlmann's gig over at Sound and Vision... ;)

Anton's picture

Are you changing formats?


Bogolu Haranath's picture

"Turn Up the Music" ........... Chris Brown :-) ........

256Kbps AAC ..... iTunes :-) ............

Michael Fremer's picture


Bogolu Haranath's picture

So ...... The world is changing :-) ........

dalethorn's picture

If the large loudspeaker (sans DSP) is properly designed and built, its superiority over the small DSP-served speaker should be obvious in a short listening session. If not, you just saved a lot of money, as people often do when they buy those Bose Wave radio/CD players.

Bogolu Haranath's picture

Things have come a long way since Bose Wave radio ........ Have you listened to any DSP speakers recently? ......... You can always add a powered subwoofer to extend the bass response :-) .........

dalethorn's picture

It's hard to make a smallish speaker compare to a much larger speaker. No EQ can get you there, but to fool yourself that you can, you'd probably make your comparison to a larger speaker that's not the best for its size. In just one example, getting equivalent power output requires small drivers that will distort more, or cost many times as much. But there are good shortcuts and bargains available for those who accept the compromises.

misterc59's picture

A lot of the speakers that are reviewed state "for the money" or something to that effect, which would obviously suggest a compromise in some area. With today's technology only so much can be done regarding speaker size, power handling, efficiency, etc. If someone wants to spend the bucks, all the power to them. Is this a crime? Taking into consideration the law of diminishing returns, there are likely thousands of products categories, including speakers, where a multitude of people fall into and have biases, likes, dislikes, for any product. For some, is the cost of a product worth the value one gets out of it? If someone prefers the sound, why not? I will not tell someone that one of their components sounds like crap to me, or should sound like something I like including something that "measures well". Mr. Dalethorn makes a good point. I will not begrudge anyone who likes "the sound" as I am POSITIVE there are many who would not like the sound(s) I prefer, and that is ok by me. I chase the sound that makes me feel good, whatever that product may be.


Indydan's picture

Bose has no place in an audiophile system.

dalethorn's picture

Neither do you.

supamark's picture

studio speaker companies (on the high end) have moved almost entirely to active and DSP controlled monitoring, but the sound and use cases are very different and probably not what consumers actually want.

Audiophiles like to mix and match components to find the synergy that gives them the sound they want - whether it's actually accurate or not is a different discussion. AD is hardly the only person who likes the old Altec sound like the 604 coax or Model 19 2-way (modified) that Bob Ludwig used to master a LOT of 80's hit records.

I really like active speakers myself (need to refurb my very low serial number Genelec 1031's) because they're dynamically far less compressed than most passive speakers and the amp/speaker match is superior... but most audiophiles are tweakers who like to try new combos and passive separates makes that easier.

ok's picture

if any of the "technically accomplished" or alternally cash-conscious, progress-fascinated, moral indignation-filled comments ever comes from people who can actually afford to hear and buy these beautiful things.

jeffhenning's picture

You don't need to afford a Bugatti Charon to know that it's absurd and the end of the road for gas-powered hypercars.

This is the same for non-DSP loudspeakers the likes of this one, anything from Wilson Audio and the like. There are still gigantic problems with passive loudspeakers that can never be fixed by a better cabinet or analog crossover. It's not possible. I have spent time with Meridian's DSP8000's (forgot to mention them). Even without room correction, they are stunning and half the price of the Aidas.

Even if I had the cash to spend on Aidas, I wouldn't. They aren't worth it.

I'm going to be replacing the LS50's and Rythmik servo subs in my main system with custom built mains using a Raven Line Source ribbon and eight BG Neo10's per side. The subs are being replaced by a stacked tower of custom, cardioid subs per side that will employ ten 8" Rythmik servo sub drivers and associated amps. I'm going to use a Xilica XD-4080 FIR speaker processor as a crossover and the mains will be driven by a pair of Benchmark AHB2 amps. DSP will be Dirac Live.

At 20% of the price of these Sonus Faber behemoths before you even buy the amp(s), this design will eviscerate the Aidas in every possible metric. And, yes, they will just sound better as well.

Again, I don't doubt that these are great sounding speakers, but they are not state of the art and never will be as long as they are passive.

hb72's picture

Are you seriously comparing a DIY project with commerical systems?? I suppose most ppl who tinker around in the DIY world are more than a lightyear & a lifetime away from being able to purchase a hifi system of several 100k. Those who can, I imagine, will not be able to hold a soldering iron, nor want to, in their scarce free time.

Plus, lets not forget, super expensive stuff is not only slightly obscene, but (more thant that) also a valid way to recycle money from accounts of the super rich to those of mid-class people. Nothing wrong with that, infact the higher the price the better. :)

Joe8423's picture

You can tinker as much as you want, no need for portability, no margin, no marketing budget, etc. Several hundred thousand dollar systems are luxury products and performance isn't the priority in that market. Since hardly anybody has ever gotten really familiar with those systems nobody knows how they perform but there's no reason to think they're particularly exceptional. The best engineers aren't designing that stuff.

a.wayne's picture

I guess you are in for a big let down , Gas powered supercars will be here tomorrow and DSP speakers sounds so unnatural i dont see them replacing conventional passive loudspeakers ...


supamark's picture

just different. you're DIY'ing a very different kind of speaker than the Aida, which will certainly sound different (and not look as good) - but whether that = better depends on taste. You're going to have some real problems integrating the ribbon/planars/cones into a coherent whole... and looking at the specs, 4 of the planar mids would probably gel better than 8 - the efficiency numbers match up better so less processing required.

JRT's picture

This is something very different from your stated plans, but worth some significant consideration.

Take a look at the presentation given by Ulrich Horbach and D.B. (Don) Keele, Jr. on the subject of "Application of linear-phase digital crossover filters to pair-wise symmetric multi-way loudspeakers" given at the AES 32nd International Conference in September 2007. Below are links to the pdfs for the powerpoint slides in two parts, and links to the associated AES papers also in two parts.

Siegfried Linkwitz stated his opinion on this as follows, "Here is a truly ground breaking, sensible and practical application of DSP to the design of crossover filters and the polar response of large multi-way active loudspeakers. Very exciting work!"

Part 1: Control of off-axis frequency response

Part 2: Control of beamwidth and polar shape

Part 1: Control of Off-Axis Frequency Response

Part 2: Control of Beamwidth and Polar Shape

ABSTRACT (associated with part one of the paper)
"Various methods exist for crossing over multi-way loudspeaker systems. These methods include those loosely classified as Linkwitz-Riley filters, constant-voltage filters, and D’Appolito configurations. All these methods do not provide broad-band constant-beamwidth or constant-directivity operation because their vertical radiation patterns change shape as a function of frequency. This paper describes a simple, non-iterative linear-phase crossover filter design technique that provides uniform frequency responses vertically off-axis for a given multi-way loudspeaker. Distances between the individual drivers, and desired off-axis attenuation are prescribed as input parameters for the design process, the outcome of which is a set of crossover frequencies and unique filter frequency responses in each band. In order to obtain wide-band constant-beamwidth, a loudspeaker array configuration composed of a single central tweeter surrounded symmetrically by pairs of lower-operating-frequency transducers arranged in a vertical line is required. Practical implementation issues are outlined in the paper by means of various design examples. Two design methods are presented in in two-parts: Part 1: a general method which emphasizes flatness of arbitrary off-axis frequency responses and Part 2: a simplified method that emphasizes frequency uniformity of beam shape and coverage angle (vertical beamwidth) of the polar patterns."

ABSTRACT (associated with part two of the paper)
"In part 2, we present an alternate simplified design technique that is based not on Part 1’s specification of frequency responses at arbitrary off-axis vertical angles, but on specification of the total shape and coverage angle (vertical beamwidth) of the polar patterns generated by pairs of separated point sources. Here we show that when only a single pair of drivers is operating at a specific frequency (Part 1 called these the “critical frequencies”), the spacing of these drivers is a constant distant apart in terms of acoustic wavelength. The design procedure of Part 2 simplifies that of part 1 by restricting the level of the forced-to-be-flat off-axis angle to -6 dB thus making it equal to the level of the polar beamwidth specification, i.e. beamwidth is defined as the angle between the 6-dB-down points from on axis. Thus restricted, Part 2 shows that the spacing of each pair of drivers at their critical frequencies should be in the range of 0.4 to 0.6 wavelength to yield well-behaved polar shapes with beamwidths in the range of 67º to 113º. Part 2 also shows that that spacing ratios between successive pairs of drivers should preferably be in the range of 2:1 to 2.5:1, but can extend out to 4:1, but at the expense of polar uniformity at angles beyond the 6-dB-down points."

retro's picture

You really think that's what this is about? Maybe I'm not as "technically accomplished" as much as you think. But I've been in this hobby (it is a hobby, isn't it?), to have learned that more $$$ does not equal better sound quality..
Now hear this:
I believe, and hear, difference, in power chords.
Ditto, signal cables.
Ditto, speaker cables.
Different DAC's, Amp's, Speakers sound different all the time, depending on what they're hooked up to. So yes, I'm a subjectivist. And yes, I can afford them. But why spend $130.000 on an MDF-box of regular drivers, no matter how beautiful the side trims are, when they don't do ANYTHING to advance loudspeaker engineering...

Bogolu Haranath's picture

Aida may be a better value for the money than Stormy :-) ............

Jason P Jackson's picture

Licorice. Mikey, I wish you didn't say that word. I'm addicted to the stuff. And there's only one brand I like, well 2 brands. Good grief, how to distract myself from the thought...speakers, amplifier design, women, vacuum the car...

Robin Landseadel's picture

"In 1959, in their musical revue At the Drop of a Hat, the British musical-comedy team of Flanders and Swann sang their "Song of Reproduction." "

Parlophone PMC 1033. Looking at it right now, next to my 10" copy of "Songs by Tom Lehrer" on Lehrer Records TLP-1.

davidrmoran's picture

Years ago JA did an in-use measurement of a Wilson and another speaker showing a large audible frequency response notch below middle C. He identified it properly for what it was, an example of the Allison effect. It was wonderful to be able to use it to discuss what happens when you misdesign a speaker with respect to the three near boundaries and get an unnatural thinning suckout in the lower midrange.

(AE has nothing to do with bass, as is commonly misunderstood.)

And now this design is even better in that regard, meaning even more starkly misdesigned for accurate playback in a room.

What a great example and what a great terrible curve figure 5 is!

Textbook, perfectly textbook of what not to do --- unless you don't care about natural sound and accuracy of playback. Roy Allison is wincing and chortling in his grave.

supamark's picture

That's not due to speaker design, that's MF's room - literally every speaker has a response depression in the low mid in his room (check his other speaker reviews). He even explicitly mentions it in the review itself (which you probably didn't even read, for if you had you would not have made this comment).

davidrmoran's picture

Of course I read it, and your "analysis" represents further comedy in this area. It shows misunderstanding of how the phenomenon works. (Just because Fremer doesn't understand something doesn't make anything any clearer.)

It's not a room effect in the way that resonances are; it has nothing to do with room resonances. No room inherently has the consistent lower-midrange dip.

Any speaker designed such that the driver(s) reproducing the two 90-360Hz octaves approach equidistance from the three near boundaries, as with a speaker on a stand or equivalent, meaning the said driver(s) are at standlike height, will show suckout problems somewhere within those octaves. In any room. To first order it is room-invariant and, crudely, also listening-position-invariant.

With pink noise and a smartphone RTA set to averaging you can check it for yourself.

Conversely, a speaker designed to enforce *staggered* ( = non-equidistant) distances to the three near boundaries, 2'/3'/4' or 2'/3'/5' are nice, or simply with the woofer close to the floor, will have no, or much less of a, constant power notch below middle C, even if the room is, you know, an 11' cube.

That room will have terrible other problems, but they will vary as you move about, whereas this one not so much. Allison effect is unrelated to room resonances.

Having the crossover seam there sure appears to aggravate the problems.

dcolak's picture

-10dB at 23Hz.

That's it not stellar, at all.

dalethorn's picture

The lowest orchestral note (ignoring giant pipe organs) is 27.5 hz as far as I know. It would be good to know what the response is at that frequency, but more importantly, how it sounds compared to other speakers in its price/size range, at that frequency.

nirodha's picture

I heard the speakers in combination with the entire Nagra HD-line and I was very impressed: coherent and full of soul from top to bottom. I never was a Sonus Faber fan but these really wowed me.

Reluctant_Audiophile's picture

I spent several hours over two days listening to the Aidas at the 2018 AXPONA show. I heard a lot of great sounding speakers at AXPONA, even one costing over twice the price of the Aidas (Von Schweikert Ultra 11 - $300,000), but I kept going back to the Aidas. The Aidas presented a life-size sound stage with the most dynamic, most life-like music presentation I have ever heard from a loudspeaker. As a musician, I appreciate realism and accuracy in music reproduction. I particularly appreciated Michael's video on the Aida installation in his listening room. It's nice to know they will work in modestly sized mine.

hnipen's picture

I auditioned the previous iteration of Aida and it’s an unreal experience. Up until now you would have to choose between the magic of a mini monitor or the large scale big loudspeaker. In Aida you have both in a way that is just far-out. Aida has the utter magic that you only get from the absolutely best small monitors... and it scales without limitations, and it provides the full weight of a symphony orchestra.

I live in a small flat and my better half asked me after auditioning if we would have space for Aida at home. Possibly but we would not be able to see the outside world.

If I had the money and space I would buy them, without any second thought. Aida is a masterpiece !

Mars2k's picture

Saw the youtube...I'm busting you out as a Hoarder...looks like my place (sometimes)