Chario Aviator Amelia loudspeaker Measurements

Sidebar 3: Measurements

I measured the Chario Aviator Amelia's farfield and nearfield behavior with the DRA Labs MLSSA system, using calibrated DPA 4006 and Earthworks QTC-40 microphones and an Earthworks microphone preamplifier. I examined the loudspeaker's impedance magnitude and electrical phase with Dayton Audio's DATS V2 system. Before performing the measurements, I mounted one of the Amelias on its baseplate using the supplied conical spacers to ensure the correct distance below the downward-firing woofer and port.

Chario specifies the Amelia's sensitivity as 90dB/W/m. My B-weighted estimate, taken on the midrange axis (see later), was slightly lower, at 88.6dB(B)/2.83V/m. The Amelia's impedance, specified as 4 ohms with a minimum magnitude of 2.8 ohms at 119Hz, is higher than 4 ohms above 200Hz (fig.1, solid trace). The minimum magnitude was 2.6 ohms between 124Hz and 144Hz, and the impedance trace is free from discontinuities that would suggest the presence of enclosure resonances. The electrical phase angle (dashed trace) is relatively high in the lower midrange, and the resultant EPDR (footnote 1) lies below 3 ohms from 76Hz to 575Hz and below 2 ohms between 125Hz and 289Hz. The minimum value is 1.14 ohms at 125Hz. Used with a tube amplifier, the Amelia should work best with the 4 ohm output-transformer tap, though the shape of the impedance magnitude trace will mean that the low frequencies might sound shelved down a little.


Fig.1 Chario Aviator Amelia, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The Chario's enclosure seemed dead to a knuckle rap. When I investigated the panels' vibrational behavior with a plastic-tape accelerometer, the only resonant mode I found lay at 688Hz (fig.2). While this could be detected on all the cabinet's walls, it is low in level and has a high Q (Quality Factor). Together with the relatively high frequency, this mode is unlikely to have any subjective consequences.


Fig.2 Chario Aviator Amelia, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall level with woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle centered on 51Hz in the impedance magnitude trace suggests that this is the tuning frequency of the Chario's downward-firing port. The port's response (fig.3, red trace), measured in the nearfield, peaks sharply at this frequency, and other than a small spike of energy at 316Hz, the upper-frequency rolloff is clean. The nearfield response of the woofer mounted a third of the way up the rear panel (fig.3, blue trace) has the expected notch at the port-tuning frequency. I haven't shown the nearfield response of the second, downward-firing woofer, as my measurement was affected by crosstalk from the adjacent port. (I was able to minimize crosstalk in the opposite direction by inserting the tip of the microphone inside the port opening.) Because of the crosstalk contamination, it wasn't possible to calculate the complex sum of the nearfield woofer and port outputs. However, it appears that the manufacturer's specified low-frequency cutoff of –3dB at 48Hz is accurate.


Fig.3 Chario Aviator Amelia, anechoic response on midrange axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the nearfield responses of the midrange unit (black), rear woofer (blue), and port (red), respectively plotted below 350Hz, 600Hz, and 520Hz.

Both woofers appear to cross over to the midrange unit (black traces below 350Hz) at a lower frequency than the specified 200Hz, though this might be an artifact of the nearfield measurement technique. The midrange unit's highpass rolloff is 24dB/octave; the woofer's lowpass rolloff is closer to 12dB/octave.

Chario's importer made it clear that the Aviator is intended to be listened to with ears at tweeter height. However, with the speaker sitting on its base and spikes, the tweeter is just 32" from the floor, which is significantly lower than what we have found to be the average height of listeners' ears: 36". The Amelia's midrange unit, which is mounted above the tweeter, is 38" from the floor. I performed a complete set of farfield response, dispersion, and time-domain tests on the midrange axis then repeated some of the tests on the tweeter axis.

The black trace above 350Hz in fig.3 shows the Chario's farfield output averaged across a 30° horizontal window centered on the midrange axis. (The response on the tweeter axis was identical other than having up to 1dB more energy between 1.7kHz and 4kHz.) The response is flat and even through the midrange, with then a slight boost in the low treble and a slight depression in the mid-treble. There is then a significant peak in the top octave. I could hear this peak as a whistle superimposed on the sound of MLSSA's pseudo-random noise when I stood in front of the speaker.

Whether it will result in audible coloration with music will depend on the loudspeaker's horizontal dispersion. This is shown in fig.4, with the off-axis response normalized to the response on the midrange axis, which thus appears as a straight line. Not only does the very slight on-axis suckout at 6.4kHz fill in to the Amelia's sides; the loudspeaker becomes very directional above that frequency. The Chario loudspeaker's treble balance can therefore be adjusted by experimenting with toe-in: No toe-in and the top octaves will be too mellow; complete toe-in to the listener position and the high treble will sound fizzy. (The on-axis response peak is too high in frequency to be heard as "brightness.") The Amelia's vertical dispersion, again normalized to the response on the midrange axis, is shown in fig.5 and confirms that the response is maintained over a wide, +5°/–10° window.


Fig.4 Chario Aviator Amelia, lateral response family at 50", normalized to response on midrange axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.


Fig.5 Chario Aviator Amelia, vertical response family at 50", normalized to response on midrange axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

Turning to the time domain, the Amelia's step response on the midrange axis (fig.6) indicates that the tweeter and midrange drive unit are connected in positive acoustic polarity, with the tweeter's output arriving first at the microphone. The drivers' steps don't blend smoothly on this axis. Only well above the midrange axis do their outputs blend smoothly. The woofers are also connected in positive acoustic polarity. As both are significantly farther from the microphone for this measurement, their outputs are probably responsible for the bumps at 5.5ms and 7.2ms in the tail of the midrange unit's step. Other than some delayed energy in the low treble, the Amelia's cumulative spectral-decay plot (fig.7) is superbly clean.


Fig.6 Chario Aviator Amelia, step response on midrange axis at 50" (5ms time window, 30kHz bandwidth).


Fig.7 Chario Aviator Amelia. cumulative spectral-decay plot on midrange axis at 50" (0.15ms risetime).

The Chario Aviator Amelia's measured performance suggests both that its balance will be more dependent than usual on the choice of amplifier and that experimentation with placement and toe-in will be necessary to obtain a neutral tonal balance.—John Atkinson

Footnote 1: EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier's output devices as the loudspeaker. See "Audio Power Amplifiers for Loudspeaker Loads," JAES, Vol.42 No.9, September 1994, and

US distributor: Monarch Systems Ltd.
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Glotz's picture

in the bass were 48hz, given the down-firing and rear-firing woofer arrays.

I'm sure they are very tuneful and articulate though.

ednazarko's picture

Maybe it's because I performed for years - as a trombone and tuba player in a wide range of groups - and as an actor and singer/dancer - but I'm very sensitized to how some speakers make live recordings sound amazingly alive. Live recordings have led me to my ultimate speaker choices going back to the mid-1990s. In every case, the speakers I bought made live recordings sound more live than the other speakers I was auditioning.

One thing in common, I've noticed (with only recent exceptions.) In every case, the speakers I chose had speakers pointing in multiple directions. My Gradient Revolutions remain my favorite speakers of all, because they created an actual sound stage at the end of whatever room they lived in. Open baffle woofer, cardiod mid range. Their ability to create images of live performances bordered on creepy. More than once I had guests in a different room get up and walk into where the speakers were, looking around. Sadly they lost a crossover and a speaker (in different units) and since they're not sold in the US... no repair possible.

Replaced by Golden Ear Triton 2, and then Triton 1. The bass radiators on the side drive the sound stage. When I asked Sandy (at a new speaker into event) how much of the SPL was coming from the radiators, he said 3/4 or more. Well. The Golden Ear speakers created spooky enough live images that our dogs have gone looking for animals in the room when animal sounds were in a recording.

The exceptions were KEF active speakers, LSX and LS50. They had an identifiable sound stage when I first heard them. In both cases, when I added an external sub, the sound stage got round and robust.'s picture

Well- done.

tonykaz's picture

I've been reading and writing for well over 7 Decades and never once came across the usage of this term. What inspired you ?

Sitting close to a String Quartet will stimulate my nervous system but I don't recall my little hairs being electrified like being in a Science Exhibit.

So, if you buy the premise you buy the bit!

I bought your premise of "surprising degree" but your final summary doesn't seem to offer an electrified experience.

Can I presume that your MBLs are just too dam good to allow a lessor's hopeful comparison?

I'm writing because "horripilation" was click bait.

Like it or not, I'm flopping around in the bottom of your little boat.

Nice catch!

Tony in Florida

MikeP's picture

We heard these KMD Orchestalls Reference speakers at Axpona 2022 and they were hands down the Best Of Show Period ! They should be back at Axpona 2023 again maybe Stereophile could listen to these this time around. "The World's First Speakers that Sounds Like LIVE MUSIC in your home" More info on You Tube too.