Canton Reference 7K loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Canton Reference 7K's frequency response in the farfield. My reference axis for the measurements was level with the center of the midrange unit, which is 36" from the floor, the height of my ears in my listening chair. I used an Earthworks QTC-40 mike for the nearfield and in-room responses and Dayton Audio's DATS V2 system to measure the impedance.

Canton specifies the Reference 7K's sensitivity as 88.5dB, presumably for 2.83V at 1m, which was confirmed by my measurement. The Reference 7K's impedance is specified as 4–8 ohms. The solid trace in fig.1 indicates that the impedance magnitude lies between 4 and 9.5 ohms over most of the audioband, with minimum values of 3.2 ohms at 120Hz and 3 ohms at 305Hz. The electrical phase angle (dashed trace) is occasionally high, which means that the EPDR (footnote 1) drops below 2 ohms between 16Hz and 29Hz, between 83Hz and 123Hz, and between 395Hz and 745Hz, with minimum values of 1.7 ohms at 36Hz, 1.4 ohms at 103Hz, and 1.8 ohms between 480Hz and 600Hz. The Reference 7K must be used with amplifiers that don't have problems driving 4 ohms.

821CR7Kfig01

Fig.1 Canton Reference 7K, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The traces in fig.1 are free from the small discontinuities that would imply resonances of some kind. However, when I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I did find a single resonant mode at 168Hz on all the surfaces (fig.2). Because this mode has a relatively low level and a high Q (Quality Factor), I doubt that it will result in audible coloration. (The lower the Q of a resonance the greater the possibility that it will be excited.)

821CR7Kfig02

Fig.2 Canton Reference 7K, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel level with the midrange unit (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle centered on 42.7Hz in the impedance magnitude trace suggests that this is the tuning frequency of the downward-firing port. The two woofers have identical responses; the minimum-motion notch in their summed output (fig.3, blue trace), which is when the back pressure from the reflex resonance holds the woofer cones still, lies a little lower in frequency, at 35Hz. The port's nearfield output (fig.3, red trace) peaks between 25Hz and 90Hz, with a clean upper-frequency rolloff. The rise in the impedance magnitude below 25Hz in fig.1 confirms that there is a series high-pass filter in the woofer feed. The effect of this filter can be seen in fig.3, which indicates that both the woofers and the port roll off below the port tuning frequency with a much steeper slope than the usual 12dB/octave.

821CR7Kfig03

Fig.3 Canton Reference 7K, acoustic crossover on midrange axis at 50", corrected for microphone response, with the nearfield response of the midrange unit (green), the summed nearfield responses of the woofers (blue), and the port (red), respectively plotted below 450Hz, 400Hz, and 500Hz.

The black trace below 300Hz in fig.4 is the complex sum of the nearfield woofer and port responses, with the latter's acoustic phase compensated for the fact that it is on the loudspeaker's base. The peak in the upper bass, which is due to the nearfield measurement technique, is a little greater in amplitude than I usually see. The low frequencies roll off rapidly below 30Hz. The Canton's farfield response, averaged across a 30° horizontal window centered on the midrange axis (fig.4, black trace above 300Hz), is impressively even between 400Hz and 8kHz, with very slight dips balanced by equally small excesses of energy. The tweeter's on-axis response starts to rise above 8kHz then drops off quickly above 20kHz. Figs.3 and 4 were taken without the vestigial grilles; repeating the measurement with the grilles reduces the level between 4kHz and 10kHz by up to 3dB.

821CR7Kfig04

Fig.4 Canton Reference 7K, anechoic response on midrange axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the sum of the nearfield responses plotted below 300Hz.

Fig.5 shows the Reference 7K's horizontal dispersion, normalized to the response on the midrange axis, which thus appears as a straight line. The contour lines in this graph are smooth and evenly spaced, this correlating with the stable stereo imaging I noted in my auditioning. While there are ridges of off-axis energy between 13kHz and 22kHz, with a gulley between them, these will be inconsequential. In the vertical plane (fig.6), a suckout in the crossover region develops 15° above and below the midrange axis, but the response doesn't change by much over a ±5° window centered on the midrange axis.

821CR7Kfig05

Fig.5 Canton Reference 7K, 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.

821CR7Kfig06

Fig.6 Canton Reference 7K, vertical response family at 50", normalized to response on midrange axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–15° below axis.

Fig.7 shows the Canton Reference 7Ks' spatially averaged response in my room. (The spatial averaging, footnote 2, tends to average out the peaks and dips below 400Hz that are due to the room's resonant modes.) The Reference 7Ks get some help from the lowest frequency mode in my room, and the bass is well-extended. There is a little too much upper-bass energy in-room—that's the richness I heard with the lower register of the marimba—but the balance at the listening position is impressively even from 500Hz to the top of the audioband. A loudspeaker that offers a flat on-axis response and well-controlled lateral dispersion gives a gently sloped-down treble in the spatially averaged room response due to the increased absorption of the room's furnishings and the narrowing of the tweeter's radiation pattern at high frequencies. By that yardstick, the Cantons have a little too much output in the top two audio octaves.

821CR7Kfig07

Fig.7 Canton Reference 7K, spatially averaged, 1/6-octave response in JA's listening room.

Fig.8 compares the Reference 7K's spatially averaged response (red trace) with that of the Marten Oscar Duo that Michael Fremer reviewed in the November 2020 issue (blue trace). The Oscar Duo costs the same as the Reference 7K—$6995/pair—though the matching stands add $995/ pair to its price. The Canton speakers' in-room response is smoother in the treble with a little more top-octave output than the Martens'. The Oscar Duos excite the lowest frequency room mode just above 30Hz to a slightly greater extent, and the Reference 7Ks roll off faster below that frequency. The Marten is a two-way design; the three-way Canton, with its separate midrange unit and twin woofers, will play louder without strain.

821CR7Kfig08

Fig.8 Canton Reference 7K, spatially averaged, 1/6-octave response in JA's listening room (red) and of the Marten Oscar Duo (blue).

Turning to the time domain, the Reference 7K's step response on the midrange axis (fig.9) reveals that the tweeter and midrange unit are connected in positive acoustic polarity, the woofers in inverted polarity. (I confirmed this by looking at the step responses of the individual drive-units.) The decay of the tweeter's step smoothly blends with the positive-going start of the midrange unit's step, and the decay of the midrange unit's step smoothly blends with the negative-going start of the woofers' step. This implies optimal crossover design. The Reference 7K's cumulative spectral-decay plot (fig.10) is superbly clean.

821CR7Kfig09

Fig.9 Canton Reference 7K, step response on midrange axis at 50" (5ms time window, 30kHz bandwidth).

821CR7Kfig10

Fig.10 Canton Reference 7K, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

The Canton Reference 7K's excellent measured performance belies its relatively affordable price.—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 stereophile.com/reference/707heavy/index.html.

Footnote 2: Using the FuzzMeasure 3.0 program, a Metric Halo MIO2882 FireWire-connected audio interface, and a 96kHz sample rate, I average 20 1/6-octave–smoothed spectra, individually taken for the left and right speakers, in a rectangular grid 36" wide by 18" high and centered on the positions of my ears.

COMPANY INFO
Canton Elektronik GmbH + Co. KG
US distributor: Bluebird Music Ltd.
1100 Military Rd.
Kenmore, NY 14217
(416) 638-8207
ARTICLE CONTENTS

COMMENTS
MZKM's picture

At least the name matches the price.

Looks very solid, though I wonder if the wider dispersion at 2kHz-5kHz could lean it towards the brighter side. With 7” drivers though it is impressive how well controlled the 3kHz crossover region is.

latinaudio's picture

were reviewed just 8 days ago, for 70.000$, these Canton for just 7.000$. Both looks very nice, both have rave reviews, both have good measurements, and almost the same driver complement. I will look forward to the ranking of both speakers in October´s Recommended Components...

georgehifi's picture

Can you tell us which comes first JA, because it would be hard not to focus on areas with the listening review to any areas where the measurements shown were a bit off before hand.

Cheers George

John Atkinson's picture
georgehifi wrote:
Can you tell us which comes first JA, because it would be hard not to focus on areas with the listening review to any areas where the measurements shown were a bit off before hand.

Though this isn't always possible, I try to conclude my critical listening to a product before I perform the measurements. In the case of this Canton speaker, I was having some issues finding the optimal positions in the room with listening alone so I wanted to check the in-room response. That's when I blew the tweeter of one of the speakers.

John Atkinson
Technical Editor, Stereophile

mtrot's picture

If these beautiful Reference 7K are competitive, from a sound quality and measurements perspective, with similarly sized models from the likes of Focal Kanta or B&W 804D3, the Cantons have to be viewed as quite the value. To me, they are certainly equally or even more premium looking.

rusoaie's picture

Hello, John!
First of all thank you for this in-depth review.

If you have the time, could you please share some tips on positioning the Canton Ref speakers? What are the issues you encountered when trying to position the 7K? - and what worked best for you (distance between the speakers, toe-in or no toe-in or other adjustments to get focus the center image and widen the sound-stage)?

Thank you and keep up the great reviews & measurements.

Regards, Mihai

gpdavis2's picture

JA - when I read your speaker reviews I'm always left wanting............ as in, "how would these work with a lower power amp?". I listen to Canton Ref 9K speakers driven by 20wpc of Class A tubes (after several considerably higher power solid-state amps) and have often wondered about upgrading to the Ref 7K. Was really looking forward to your review, but, sadly, am still wondering about using them with my 20wpc amp. What do you think? Would this be a good match? Would like to see you (and MF & the other JA) do as HR and other reviewers and also give a listen with a smaller amp. Even a tube amp. Not all of us have nor want 450wpc amps.

rsleve's picture

Dear John Atkinson, I'm upgrading from my ProAc Response D8s moving to full-range 3-way, and considering both Canton R7s and Triangle Signature Deltas, both of which you have reviewed and are in the 8k range. I listen to Jazz, Classical, nuanced Rock, and love vocal music as well. I am running Hegel 190 and Gold Note DS-10 and PS-10 in a room 15 x 20. Can you tell me your sense of difference between the two loudspeakers? Rob

John Atkinson's picture
rsleve wrote:
I'm upgrading from my ProAc Response D8s moving to full-range 3-way, and considering both Canton R7s and Triangle Signature Deltas, both of which you have reviewed and are in the 8k range. . .

Been six years since I had the Triangle speakers in my system. I would choose the Cantons, as they have a more neutral high end, though the Triangle's high sensitivity means it would be a better match for low-powered amplifiers.

John Atkinson
Technical Editor, Stereophile

rsleve's picture

Thanks, John. I had a feeling that might be the case from your review. Rob

supamark's picture

Kevlar is a polyAmide, not a polyImide. Kapton is the most well known polyimide - pretty cool stuff, it's the clear orange film on stuff going to space and also used to form woofer voice coils. Sorry, biochem degree, couldn't not say something :)

Mark Phillips,
Contributor, Soundstage! Network.

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