Dynaudio Confidence 30 loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Dynaudio Confidence 30's frequency response in the farfield, and an Earthworks QTC-40 mike for the nearfield responses. I measured the speaker's impedance with Dayton Audio's DATS v2 system.

Dynaudio specifies the Confidence 30's sensitivity as 88dB/2.83V/m; my estimate was within experimental error of that figure, at 87.5dB(B)/2.83V/m. The Confidence 30's impedance is specified as 4 ohms with a minimum magnitude of 2.8 ohms at 85Hz. The impedance magnitude (fig.1, solid trace) remains above 8 ohms over most of the audioband; the minimum value is 2.7 ohms between 88Hz and 92Hz. The electrical phase angle (dashed trace) is occasionally high, which means that the EPDR (footnote 1) drops below 2 ohms between 53Hz and 101Hz and between 228Hz and 372kHz. The minimum EPDR value is 1 ohm from 68Hz to 80Hz and 1.28 ohms at 279Hz. The Confidence 30 should be used with amplifiers that don't have problems driving impedances of 4 ohms or lower. The shape of the impedance magnitude trace suggests that the Dynaudio's high frequencies will be emphasized if the loudspeaker is used with tube amplifiers that have a high output impedance.


Fig.1 Dynaudio Confidence 30, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The traces in fig.1 are free from the small discontinuities that would imply panel resonances. When I investigated the elegantly curved enclosure's vibrational behavior with a plastic-tape accelerometer, I found a single resonant mode at 563Hz, on the sidewalls (fig.2) and on the front baffle below the sub baffle that carries the drive-units. As this mode has a relatively high frequency and a high Q (Quality Factor), it is unlikely to have audible consequences.


Fig.2 Dynaudio Confidence 30, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel level with lower woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle centered on 28Hz in the impedance magnitude trace suggests that this is the tuning frequency of the downward-firing port. Both woofers behave identically, and 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 at the same frequency. The woofers' output rolls off rapidly above the 290Hz crossover frequency to the midrange unit (green trace—this trace and that of the woofers' output are truncated at frequencies where the measurement is affected by crosstalk from adjacent drive-units). The port's output (fig.3, red trace) has one peak centered on the tuning frequency and another one and a half times higher. The port's higher-frequency rolloff is clean, though there is some low-level output present between 300Hz and 500Hz. As the port fires downward, this higher-frequency behavior should not be audible.


Fig.3 Dynaudio Confidence 30, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the nearfield responses of the midrange unit (green), woofers (blue), and port (red), and the complex sum of the nearfield responses (black), respectively plotted below 500Hz, 450Hz, 525Hz, and 300Hz.

The black trace below 300Hz in fig.3 is the complex sum of the nearfield midrange, woofer, and port responses. The peak in the upper bass will be due in part (6dB) to the nearfield measurement technique, which assumes that the baffle extends to infinity in the vertical and horizontal planes. However, while the Dynaudio speaker offers extended low frequencies, those low frequencies are a little elevated in absolute terms. The Confidence 30's farfield response, averaged across a 30° horizontal window centered on the tweeter axis (footnote 2, fig.3, black trace above 300Hz), is even to the top of the audioband, with small dips balanced by small peaks. This graph was taken without the grille; repeating it with the grille in place depressed the loudspeaker's output between 3kHz and 5kHz by 1–2dB.

Fig.4 shows the Confidence 30's horizontal radiation pattern, normalized to the response on the tweeter axis, which thus appears as a straight line. The contour lines in this graph are even and reveal a well-controlled dispersion below the top audio octave, both of which correlate with accurate, stable stereo imaging. This graph also reveals that the small dip at 5kHz and the slight excess of energy below that frequency in the on-axis response flatten out to the speaker's sides. This suggests that experimentation with toe-in should allow for a neutral treble balance. In the vertical plane (fig.5), a suckout develops 10° above the tweeter axis, which represents what will be heard by a standing listener. However, the response 5° below the tweeter axis, which is what a seated listener will typically hear, is basically identical to the behavior on the tweeter axis.


Fig.4 Dynaudio Confidence 30, 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.5 Dynaudio Confidence 30, 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 5–15° below axis.

Turning to the time domain, the Confidence 30's step response on the tweeter axis (fig.6) reveals that with the amplifier's positive output connected to the speaker's red binding post, all four drive-units are connected in inverted polarity. (I confirmed this by looking at the step responses of the individual drivers.) The decay of the tweeter's step smoothly blends with the negative-going start of the midrange unit's step and the decay of that driver's step smoothly blends with the start of the woofers' step. This suggests optimal crossover implementation. The Confidence 30's cumulative spectral-decay plot (fig.7) is clean, though some very low-level hash is present in the treble. I suspect that the apparent ridges of low-level decayed energy that can be seen in the upper midrange are due to early reflections of the midrange unit's output. (The very slight discontinuities visible at 5ms and 6ms in the step response imply the existence of reflections.)


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


Fig.7 Dynaudio Confidence 30, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Overall, Dynaudio's Confidence 30 offers excellent measured performance.—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: As the Confidence 30's on-line manual doesn't mention the preferred listening axis, I used the tweeter axis, which is 41" from the floor, as the reference for the measurements.

Dynaudio A/S
US distributor: Dynaudio North America
500 Lindberg Ln.
Northbrook, IL 60062
(847) 730-3280

Anton's picture

I greatly appreciate your decision to talk about break in vs. 'listener accommodation.'

Very much neurologically pitch perfect!


Now, if only my budget was of the same high quality as your review!

If this product is Major League....or more like Triple A, given its place in their product lineup, that puts me at Single A...minor league!

georgehifi's picture

These things have an evil bass loading, almost as nasty as the Wilson Alexia's
JA's "should be used with amplifiers that don't have problems driving impedances of 4 ohms or lower" to me seems a little understated.

Cheers George

ZdzislawBoniek's picture

I wanted to get this speaker from my local Dynaudio dealer BUT they cannot get it for me because they are not "Confidence certified" dealer!
Its a nonsense - Dynaudio will loose sale because they will not let their dealer sell $21k speaker....
To become a "Confidence" dealer, one has to have at least 3 pair from the line as a demo - I do not blame dealer for now wanting stock something that might not sell.
sad....I emailed Dynaudio Denmark about this issue and am curious to see their response...

aRui's picture

I read the review and realized that the Revel Ultima2 series, which was almost 15 years old design, still stand strong against the New Dynaudio Confidence. I auditioned the Revel Salon2 vs Dynaudio Confidence 50 (about same prices when I auditioned) and end up picked the Revel Salon2 :) I had some more chances to audition the New Confidence after I purchased the Salon2. And I have never regretted my decision.

latinaudio's picture

The reason? There have not been great advances in the design and construction of loudspeakers as there has been in electronics. Subtle changes yes, but important breakthroughs no. Including the monstrous YG Acoustics speakers :)

w1000i's picture

The reason not new driver that revolutionize the consept.

georgehifi's picture

Yes drivers in particular, some inventor has to find a different way of pushing and pulling air into a room, and lowering the mass of whatever it is considerably.

Cheers George

a.wayne's picture

Smooth step response is not what fig 6 makes ...


Ortofan's picture

... these speakers may not have been the optimal choice due to their particularly low minimum impedance.

The manual for the AHB2 specifies an output current capability of 29A into a 1Ω, or about 840W.
However, peak output power tests conducted by HiFi News resulted in outputs of 108W / 200W / 346W / 230W into 8Ω / 4Ω / 2Ω / 1Ω.
The 230W output into 1Ω is equivalent to only about 15A, not 29A.

By comparison, the HiFI News test of the Rotel RB-1582 resulted in peak outputs of 295W / 555W / 1005W / 1630W into 8Ω / 4Ω / 2Ω / 1Ω.
The 1630W output into 1Ω is equivalent to about 40A.



Kal Rubinson's picture

Your comments are acknowledged but please note that the NAD C298, in stereo and monobloc, was also used in this review.

Ortofan's picture

... have significantly greater peak power output capability than a Benchmark AHB2 - assuming that it meets/exceeds those specs.
None of the tests I've seen, thus far, have measured the power output at loads of 2Ω, or lower.
The one review that attempted to measure peak power encountered issues with the protection circuit.

NAD claims peak power outputs in two-channel mode of 260W / 490W / 570W into 8Ω / 4Ω / 2Ω.
Further stated is a peak current output of 25A into 1Ω, which would equate to 625W.
In bridged/mono mode, NAD claims peak power outputs of 1000W / 1100W into 8Ω / 4Ω. The small power increase into 4Ω, versus 8Ω, suggests that some limiting mechanism is already coming into effect at that impedance.

Operating in bridged/mono mode increases the output voltage capability, but doesn't provide a higher power output at lower impedances if the amplifier can't supply the needed current and/or the protection circuit won't permit it.

JHL's picture

...the slow, inevitable spiral toward the drain of audio as an objective aural experience, to be replaced by a gross commoditization wrought by meter readers, detached techs, and pugilistic invaders with a short stack of random data, we're reminded that fifteen amperes of audio current is insufficient to drive a competent residential loudspeaker.

Maybe we need a new Paradigm. One overtly unmoored from the former realities we thought we'd built fifty years of rich audio experience upon. Apparently it was we who were deaf and the non-listener who, somehow, really knew what was going on.

Fifteen amperes.

Ortofan's picture

... power amp, with an output current capability exceeding 100A, would be simply ... pointless.

JHL's picture

How would we frame even fifteen amperes applied to voice coils that will promptly convert ninety-nine percent of that half a thousand watts into heat.

Kal Rubinson's picture

.....objective aural experience.....

All aural experiences are subjective.

jond's picture

Kal thanks for the heads up on Buster Williams Griot Liberte I gave it a listen and it was a lovely record. I'm now on a Buster Williams tear!