Chario, Academy, Sonnet
Copyright 2010 Troels Gravesen

Discontinued as kit from Jantzen Audio. Source components locally.


Download Sonnet Manual      Link to Chario website     Crossover Up-grade Kit

Do not expect a Stereophile type of review of these charming Chario Academy Sonnet loudspeakers. I cannot write page after page of how a loudspeaker sounds. It takes special skills to extend listening impressions page after page. Sometimes I enjoy reading reviews and sometimes I'm utterly bored by a writer repeating himself time after time on recordings I don't even know. What I usually try to extract from speaker reviews is any tiny reservation, any subtle selection of words or phrases that may imply that the reviewer is not entirely satisfied with the product. Obviously a review has to be positive, otherwise no adds from the manufacturer next month. I have to give in that Stereophile had two negative reviews early this year - and my God, the manufacturers got mad! How Vince Bruzzese of Totem Acoustic could make a total ass of himself in his response was truly embarrassing for Totem. Read Stereophile Jan-10.

Anyway, I had a mail from nnnn, asking me to make a new crossover for his newly acquired Chario Sonnets, and having only recently heard these speakers at the Copenhagen dealer - and being pleased with what I heard - I was somewhat surprised and responded that these Chario guys were probably not any guys - and I felt pretty sure they'd given the crossover some deep thought before launch. Hmm..... Two months went by and nnnn had found himself very pleased with the speakers, but offered me to borrow the speakers and check out the crossover for possible up-grades. Not a new crossover, but better components, because what we find in the Sonnet is a bunch of tiny cored coils and loads of electrolytic caps! The quality of crossover components is in severe contrast to the meticulously crafted cabinet, binding post and everything else you can observe from this speaker. Good crossover components are expensive and seriously add to production cost and even in excessively expensive speakers we may find so-and-so components. It doesn't help being uncompromised if it puts you out of business. As always, we're into diminishing return of our investment when going to the extreme and for most people it may not count at all. Most speakers are bought based on looks, rather on sound quality.

The Sonnet cabinet is a masterpiece of CNC manufacture. Solid walnut sides and top. Front and rear panels from sculptured MDF a diy'er can only dream about ever making. Binding posts specially made for Chario (expensive) and both drivers are bolted to the cabinet by state of the art T-nuts. Even the screws holding the drivers are specially made to fit the chassis and finished by what looks like the same nextel coating applied to rear and front panel. Total yummy to the eye and for the hands holding them.
Both drivers are custom made and ooze quality. Bass driver features machined magnet parts and a proprietary Rohacell cone, molded in one piece with none of the problems often seen from poorly made dust caps. Chario has chosen not to do anything about the all too common 1 kHz rubber surround resonance problem, but it's not severe and finding the "right" rubber surround may cause other problems.
Chario is a true believer in large domes and I like it. Read
TQWT article. Here we find a 32 mm dome with silver coating and before I had the opportunity to dismantle the Sonnet, I had a suspicion this dome was a variant of the venerable Audax TW034, but this is not the case. Once more a proprietary driver*. Cloning this speaker is not possible, thus I have no reservation in revealing the crossover in detail. And by the way; I've read (or rather seen as I don't read Italian) several Italian speaker reviews with thorough description of crossovers incl. schematics. Apparently comme il faut beyond the Alps.
*: I actually think the Sonnet tweeter is a derivative of Ciare MT320 with another face plate and rear chamber. The larger domes in some of Chario's portfolio for sure look like Ciare PT383 so I guess Chario is a frequent customer at Ciare company.

The crossover is not the least interesting part of this speaker. Basically a 2nd order filter at 1180 Hz. End of story? Not quite. You need to read the manual for this speaker to get the story behind the chosen point of crossover because it's a long one. Here some quotes:

"As a corollary to this rigorous scientific status, we at Chario Loudspeakers assert once again that it is always possible to work miracles in doing our job, but it is never possible working miraculous designs beyond physical laws boundaries. Sonnet proudly stands at the borderline of audio knowledge waiting for audiophiles to listen to their authoritative voice, because …we think differently!"

Hmm...Who wrote this pretentious academic monbojumbo? I find a contradiction between what's written in these manuals and the honest product performance claims. Because for once we get performance data and measurements that appear to truly reveal what their speakers do. Sonnet: Claimed 90 dB sensitivity is exactly what I measure. Impedance plots, frequency plots, etc., all in accordance with my findings. Excellent!!
BTW: If we go to the Copenhagen dealer on Chario speakers we find 93 dB sensitivity and F3 = 50 Hz. Chario website (and manual) states 90 dB/2.8V and F3 = 55 Hz. I guess this is what we can expect from an Audio Note dealer......

"Frequencies below about 700 Hz are processed by determining the arrival time to each earpinnae and this is referred to as IT ). Frequencies above about 1,400 Hz are processed by determining the energy flow delivered to each era-pinnae and this is referred to as IAD (inter-aural amplitude difference). We soon recognize Duplex Theory not to be exhaustive because it fails to correctly explain the localization process within the missing 700-1,400 Hz range. At these frequencies head & torso are enough obstructive to modify the incoming wavefront (diffraction) so that the crossover from ITD to IAD is not linear and localization cues are not flawless."

What appears to be the long and the short of it, is this: The ear detects sound in two ways as described above. I've checked Wikipedia and this seems sound knowledge. So, between ~700 and ~1400 Hz our brain has trouble finding out what the heck is going on, so by placing the point of crossover between these two frequences, we fool the ear/brain and we can't find out whether the sound comes from one driver or the other. Result: Perfect driver integration! Does this make sense to you? If not, please post me your interpretation. By the way: In the laboratory where I work, we have three incubators side by side. Whenever an alarm (~1 kHz sine wave) goes on, it's impossible to hear from which incubator the damn sound comes, so maybe we have trouble localising sounds from this frequency range). Just a thought.
What is a bit disturbing is that the Sonnet drivers integrate very well. And not only well, but excellent. Came to think of my SP44 speaker with the Accuton dome dome crossed at 900 Hz...
Overall phase integration between the Sonnet drivers is not perfect and with the speaker tilt, the bass driver is serious behind the tweeter making this an anything but time or phase coherent speaker. Check step response below.

Chario Sonnet also features proprietary WMTTM technology. So, what is WMT? Basically it means woofer-mid-tweeter with the woofer on top. Like Dynaudio used to do - and sometimes still do, so this can't be all that proprietary. You get the lower mid - in particular - off the floor and reduce floor bounce. Not a bad idea at all.

The choice of crossover components is disturbing too. A strange blend of film and electrolytic caps. For the bass driver's shunt cap two different film caps to make 50 uF. Why not a single e.g. 47 uF Solen cap. For the bass LCR circuit (to flatten upper bass impedance peak) four different electrolytics bypassed by a 1.2 uF film cap to make 322.2 uF. Why not a single 320 uF electrolytic? No problem in finding that. For the tweeter a 2.2 uF film cap and next 21.3 uF from two different film caps. Why not a single 22 uF polyprop? No problem in finding that either. I don't get it. In particular the bunch of strange electrolytics for the bass LCR. The use of a PC board is another no-no for bewildered audiophiles. The possibility of targeting a particular sound from the blend of these particular caps simply doesn't make sense. I'm sure this is not the case. The simple reason may be to minimise the general wide spread of electrolytic capacitor values. Usually electrolytic caps are +/- 5-10%, but for this LCR circuit precision is not overly critical, so this really doesn't make sense either.
I guess the Chario crew doesn't give a damn about my preference for high-cost super caps and the like. Audiophile woodoo and snake oil! These Sonnets' owner will replace all caps with super caps and polyprops and time will tell whether this is worthwhile.
With regard to the coils used, my only objection is the bass driver's 1.75 mH series coil made from very thin wire wound around a long ferrit core. This will be replaced by a huge air-cored coil from 1.6 mm wire.
All resistors appear to be wire-wound low inductance types. No tweaking here. The cabinets' solid wood panels are rather resonant and will de damped by 4 mm bitumen pads. Finally the internal wires will be replaced by gold-plated silver wires as nnnn has a preference for this. That's all.

There are many ways to make good speakers and Chario Sonnet is certainly one of the better. Bass appear deeper than cabinet size and measurements suggest. It may not be the most punchy and precise, but it has good volume and overall something most people could live with. Next you have a "Half-exponential Hourglass Type" vent according to manual! How about that?
Midrange is nothing short of excellent with great level of transparency and lack of colouration. As mentioned earlier, mid-tweeter integration is perfect and the large dome has no trouble providing airiness to the presentation, most likely thanks to a serious elevated response from 6 kHz to beyond my hearing. The dip between 2-5 kHz probably adds to the fact that this speaker is quite tolerant on program material.
These Chario guys have their own ideas and thanks for that! It's been a pleasure investigating their product and hear what they have made of a classic six-plus-five-quarter-inch stand-mount speaker. I'm looking forward to hearing the two speakers with an up-graded crossover - and playing equally loud! Read below.

Further information on interaural time difference can be found here:
More info by google
"duplex theory"

By the way: After having finished the page here, I found a review in Stereophile of the Chario Academy Sovran speaker. This 3-way has the same upper drivers - and most likely crossover similar to this Sonnet speaker. I was pleased to see my measurements confirmed by John Atkinson, i.e. the lack of response the the 2.5-5 kHz region, the seriously elevated response above 7-8 kHz and not least reading Michael Fremer's sonic impressions, which were well in accordance with my own:
The Sovran impressed me most with its rock-solid rhythmic coherence and its clean, nimble attack, followed by its smooth tonal balance. Add to that its solid imaging and impressive soundstaging—depending on the speaker positions, you have a choice of a deep, narrow soundstage or one that's a lot wider and a bit shallower, but with consistent reproduction of timbres either way. Add to that the meticulously finished cabinets of solid hardwood, exceptional resolution of high-frequency detail with only a slight tilt toward brightness, and you have a speaker that, while not inexpensive, offers exceptional performance with fit'n'finish to match. But equally impressive was what I didn't hear from the Sovran: bloat, false warmth, etch, grain, or—especially—congestion.
- even without the subwoofer.

Sonnet bass driver. Rubber surround, kapton voice coil former, neodym magnets and machined magnet parts. Nice driver!

Sonnet crossover
LspCAD simulation

Simulated crossover with dZ = 45 mm. Very close to actual measurement.

Predicted system impedance.

Impedance from various values of R2031.
Some bass-tuning may be possible depending on placement in room.

Sonnet, measurements

Left: Actual SPL/2.8V @ 1 meter for left and right speaker, tweeter axis (speaker mounted on Chario stand). Hmm.... gotta be something wrong here...
Right: Measured system impedance of both speakers. Quite some difference!
Measuring Re of both bass drivers reveal 3.21 and 6.16 ohms. Both have labels stating 4 ohms, but one is certainly an 8 ohms driver. Now, considering the overall impeccable fit'n finish and a ~1700 EUR/ea price tag, this is a major flaw by Chario. No quality control? The Sonnet speaker is rated 4 ohms and I'm sure the correct bass driver has 4 ohms impedance. Bad, bad....

NB: The owner immediately contacted the dealer and two new woofers are on the road from Italy. Excellent service! Chario suggested the "8 ohm driver" has a damaged litze wire - or something - as they don't produce this driver in 8 ohms version. This makes sense as TS measurement suggests an unusual high Qt of 0.65. A straight 8 ohms voice coil would not alter the Qt that much.

Left: Free air impedance of both bass drivers.
Right: Response of individual drivers and summed response (red) driven from crossover (4 ohms bass driver).

Measurements below all on 4 ohms speaker.

Left: Tweeter with correct (red) and inverted (blue) polarity. Measured at tweeter height. Speaker on original stands.
Right: Response with inverted tweeter polarity at 5 deg. below tweeter axis (1 meter).

Left: Horizontal dispersion at 0, 10, 20, 30 and 40 deg. Chario recommends placement parallel to front wall, thus a fairly flat response at listening position.
Right: Vertical dispersion (1 meter) from lower edge of cab to upper edge of cab).

Left: CSD, 40 dB scaling. Right: CSD, 20 dB scaling.

Left: Step response. Right: ETC plot.

Drivers, no crossover:

Left: Response of bass driver in cabinet without crossover. As can be seen the bass driver's rubber surround has problems at 1 kHz as is the case for a lot of drivers.
Right: Impedance of bass driver in cabinet without crossover. Minor resonances at 1, 3 and 4 kHz.

Left: Blue = tweeter response without crossover. Very sensitive driver!
Right: Measured TS data for one driver. Cabinet volume ~17.5 liter. Port tuning (Fb) = 46 Hz. F3 = 60 Hz. This is quite an efficient driver thanks to the 4 ohms voice coil.

Sonnet Tweeter

Tweeter features fabric dome and suspension, kapton voice coil former, vented pole piece and not least: Symmetric drive! The copper sleeve reducing eddy currents goes all the way to the bottom of the center pole piece and this is the way it should be made. A copper ring here and there doesn't quite make it.
The dome itself is special having surround and dome made from the same fabric, yet glued together right above voice coil. The surround almost rises vertical before being glued to the dome. This may improve energy transfer from the voice coil to the dome and enhance high frequency response.
The thin walled plastic cup making the rear chamber is highly resonant and may benefit from a MDF disc glued to the cup.
All in all it seems Chario knows where to spend the money.

The tweeter here is by large identical to the Ciare MT320 tweeter. The Sonnet tweeter does not have the rounded edges of the center pole piece like the MT320 and it comes with a larger rear housing, something that based on measurements is hardle needed. Finally the Sonnet dome has a silver coating where the MT320 comes in black, obviously nothing that will impact the sound. Read here:

Unconventional damping of tweeter pole piece. A large foam plug is stuck within voice coil former. The entire dome is resting on this pillow.

Crossover Up-grade Kit

Discontinued as kit from Jantzen Audio. Source components locally.

Suggested hard-wired crossover. The board is 9 x 145 x 180 mm Baltic birch.

All technical questions to


The original crossover board.

Identifying the capacitors and coils. This is the weirdest collection of caps I've ever seen:
e.g. 5 different caps to make up 330 uF! What's going on?


Below the up-graded, hard-wired crossover.

Click images to view large.


Having installed the new crossover we could hardly wait hearing the result - and we were not disappointed. I'm not much of a believer in crossover burn-in and right out of the workshop, hooked up with the Jungson class A amp, High Life from the Pawnshop was as transparent as I'm used to from the DTQWT although not with the same low-end extension and dynamics - for obvious reasons.
The overall sound is more tight and transparent compared to the standard crossover, revealing more layers in the acoustic image and I couldn't help noticing the even power response making your placement in front of the speakers less critical than many other speakers. No hot spot here! Treble is more fresh and clean and without any aggressiveness from even that most near-miked saxophones or vocals. These large domes have made me think - once more - of future projects.

Response to Chario article. Comments may be posted if found relevant to the article and may be edited.

Q: Regarding the X-over for the Chario Sonnet where you question the use of multiple, paralleled capacitors I have a simple suggestion. If we view the capacitor as a dynamic device with a complex impedance then I would argue that the circuits reactance is; Reactance(Cap A) + Reactance (Cap B) and NOT Reactance (Cap A + Cap B), especially for complex wave-forms. My assumption is that the multiple paralleled capacitors "sound" different. Maybe it is worth a hearing test - though I am quite clueless as how  to choose the appropriate waveforms. Richard.
A: Been thinking the same thing. It has to seen (heard) whether this really impacts performance. The filter is active below 100 Hz and my best guess is that the quality of the cap(s) is irrelevant, but I wouldn't be surprised if Chario think it is. Troels.

Q: Do you know, where the midwoofer are available to buy, for some Diy Projects? Thanks in front. Alex.
A: Hi, all drivers are proprietary. Only made for Chario. Troels