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M-Audio EX66 Powered Closefield Monitor

The EX66 is a large step up for Digidesign’s overachieving little brother, and is equipped with three drivers, a high-power onboard amp, digital processing and digital input.

(click thumbnail)M-Audio has been making powered monitors for several years, focusing on inexpensive closefield models that sounded pretty good for not much money. The EX66 is a large step up for Digidesign’s overachieving little brother, and is equipped with three drivers, a high-power onboard amp, digital processing and digital input.


Priced at $1,399 per pair retail, the designed-in-US/made-in-China EX66 sports two six-inch woofers and a one-inch titanium dome tweeter. The well-braced MDF cabinet utilizes a rear port for bass extension.Specs include a claimed 37 Hz – 22 kHz frequency response (50 Hz – 19 kHz +/- 1 db). The EX66 features two 104-watt (dynamic power) Class D amplifier sections: one for the bass, one for the treble. The two-way driver arrangement contains a 2.56 kHz 4th order Linkwitz-Riley crossover. All signals — analog or digital — are converted to digital.

The clock accepts any sampling frequency up to 216 kHz and re-clocks it at 96 kHz. The tone-tailoring controls are DSP-based and include high-frequency adjustment, low-frequency cutoff, acoustic space bass compensation (full, half and quarter) and midrange boost.

Inputs and outputs include AES/EBU input and S/PDIF input for the digital, and 1/4-inch input balanced and XLR balanced for the analog. There are also digital pass-thru jacks to feed separate left and right signals. The cabinet measures 19-inches tall by 8.25-inches wide and 9.5-inches deep. Weight is a not-too-heavy 25 pounds each. The drivers are shielded to prevent video screen coloration.

In Use

I set up the EX66s in my studio, mounting them on custom Apollo stands and moving them about three feet from the wall and about six feet apart, angled in slightly for better dispersion to the listener’s position. I fed analog audio to the speakers via a Legacy/Coda high-current monitor preamp and a Trident 8T console I had on hand for another review. Digital audio — 96 kHz and 192 kHz — was relayed from a Lynx L22 PCI card/Mac G5 workstation.

All audio was routed via Alpha Core solid silver XLR or Westlake Low PE XLR cables. Audio included 192 kHz and 96 kHz PCM acoustic guitar mixes, several reference SACDs and DVD-As, as well as some bluegrass music done at 44.1 kHz. I also listened to a house dance recording that I remastered a couple of years ago.

Fast FactsApplications
Studio, project studio, broadcast, postproduction

Key Features
216 kHz digital input for re-clocked 96k playback; two six-inch woofers and a one-inch titanium dome tweeter; a rear port; two 104-watt Class D amplifier sections

$699 each

M-Audio | 626-633-9055 | www.m-audio.comOther speakers I had on hand to compare with the EX66s included Legacy Studios and Lipinski L-505s — both passive speakers, but about the same size. The Lipinski L-505s are about as accurate as PAR has ever measured, and are good speakers to compare with closefield monitors. The passive speakers were driven by amps ranging from a high-end Pass Labs X-350.5 to a $150 Behringer amp.

I left the speaker tone controls in the flat position, though I did play with the acoustic space control and found it to work best in the half-space mode for my room.

After a week’s worth of break-in time, I sat down and listened to the EX66. Upon first listening to some reference jazz SACDs, I thought the EX66s were quite articulate on the top end. I could clearly hear room reverb tails from drum cymbals and the speakers did a good job of reproducing instrument timbre.

The bass was excellent — with depth and tightness, but without mid-bass boom I have heard in other small, ported speakers. Acoustic guitar recordings — especially an Audix SCX-25-miked Martin custom 00-28 — sounded really good. Imaging was wide, with good detail filled in between the speakers.

In comparison to the Lipinski and Legacy passive speakers, I heard many of the musical nuances with the EX66s — especially in the transients. The M-Audio has more low bass than the Lipinskis.

The EX66s delivered lower-to-moderate SPL pretty cleanly, but lost clarity when really cranked up. The highly modulated recordings with horns or keyboard music got a bit congested sounding; I thought they sounded better loud with acoustic music and classical than busy pop and jazz music.

Ergonomically, the speaker controls and settings were easy to use. And, unlike its pricier Digidesign cousins I reviewed a few issues ago, the EX66s can run 192 kHz signals via the digital input and hear the audio (albeit down-sampled).


At $1,199 per pair on the street, the EX66 is priced in a very competitive niche for a powered studio monitor, and I think M-Audio has done a good job providing a full-featured speaker with good performance. It’s not a speaker that sounds its best really loud, but it does a reasonable job reproducing accurate audio at low-to-medium levels and delivering precision in the stereo image.

(click thumbnail)BENCHTEST
Bench Measurement Data

Frequency Response:
On-axis 67 Hz to 19.1 kHz +/- 3.0 dB

Bass Limit:
75 dB SPL @ 50 Hz @ 2 meters (<10% Distortion)

Control Action:
Low Cutoff:
37 Hz Actual Frequency 69 Hz
80 Hz Actual Frequency 82 Hz
100 Hz Actual Frequency 94 Hz

Midrange Boost:
+ 2dB; Actual Boost 1.5 dB 400 Hz to 7.5 kHz

High Frequency Adjustments:
+2 dB; Actual Response +2 dB > 2 kHz
-2 dB; Actual Response – 2 dB > 2 kHz

Acoustic Space: (Compared to Full Space)
Quarter Space: -3.7 dB < 500 Hz
Half Space: – 3.0 dB < 500 Hz

Bench Measurement Commentary

The Bass Limit of the speaker is the Sound Pressure generated at 2 meters in an acoustically large (7600 cubic foot room.) The figure of merit 10% distortion is used because operating characteristics of drivers (using DLC Design DUMAX) shows that when a speaker has reached the end of its linear operating range (BL product has fallen to 70% of the rest position value or the suspension compliance has stiffened by a factor of 4) the unit will still sound clean, but distortion increases exponentially with further drive. With powered speakers amplifier output or limiting may also limit sound pressure capability.

Basic measurements here have been taken at a full 2 meters in a large room on a 6 foot stand. Using time windows then gives equivalent anechoic results above 200 Hz including front panel reflections, cabinet diffraction and true acoustical summation of all drivers and passive radiating elements. Control action was measured using the same microphone set-up.

Of the original pair of EX66s I received one of them had a response anomaly at 8 kHz that clearly showed the speaker was defective. Potential customers should make certain that return privilege is assured. Control action of everything except Low Cutoff matches specification closely. In the lower operating range of the speaker it can be seen that the port only acoustically adds response well below the true operating range of the upper frequency drivers at reasonable listening distance of 2 meters and 90 dB SPL. This is also true of much of the competition and loudspeaker specifications are frequently made under conditions that do not emulate actual usage conditions. This is why Pro Audio Review measurements are made at a full 2 meters, a reasonable listening distance, which allows true acoustical summation of all radiating elements in a real environment. The EX66 has a 4-5 dB elevation between 2 and 6 kHz that forms the basic sonic character of the system. Directivity is well controlled and the system will sound similar at all listening positions. Dynamic capability is relatively limited. The EX66 can produce 75 dB SPL at 50 Hz and 2 meters but at that sound level the system is quite sensitive to system noise with small increases in drive level. Be sure to use a woofer system with wide band low frequency program material.

— Tom Nousaine