Avlex 4U2SET Two-Channel Audio Analyzer

There has been a bump in "new" audio analyzers hitting the market in the last year. Not to be left behind Avlex has brought out 4U2SET ($1,199), a two-channel analyzer with some unusual features.
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Fast FactsApplications: Contracting; studio, live sound, sound reinforcement, broadcast

Features: Handheld analyzer; measurement mics; two-channel; RTA; sound level meter; polarity; reverb; THD+N; difference modes; CD with test signals

Price: $1,199

Contact: Avlex at 913-906-9216, www.avlex.com.


+ Lots of measurements

+ Dual channel

+ Large, high-contrast display


- Multiple parts might get lost

The Score

A feature-packed handheld test system for above average use.There has been a bump in "new" audio analyzers hitting the market in the last year. Not to be left behind Avlex has brought out 4U2SET ($1,199), a two-channel analyzer with some unusual features.

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The 4U2SET is a complete system including these components in a carrying case: the analyzer itself; two microphones with 1/8-inch mic capsules; two mic cables; two mic shockmounts; an AC power adapter; a line level variable attenuator to accommodate line level signals; two mic batteries; PDA-type pen; tripod table mount; a CD-ROM with audio test signals and PC software to upload data to a computer and an RS-232 port cable for data transfer to PC (via a DB-9 connector).

Another notable feature: The analyzer has two input channels, so it can difference two measurements done at the same time. For example, plug a PA console output into analyzer Input 1. Plug a mic into analyzer Input 2. As music is playing through the house system, the analyzer displays the difference spectrum so you can apply house EQ - even with an audience present. Another application of Difference mode is to measure the transmission loss of a wall, with two mics placed on either side of the wall.

The 4U2SET has a large, easy-to-read touch screen that operates with a pen like a PDA. It also works with keys (buttons) on the analyzer. Using the touch screen, you can select two menus. Main Menu 1 contains all the tests: RTA, sound level meter, two-channel difference RTA, polarity check, reverb time, THD + N, spectrum average, and equalizer calculation. That is a generous number of tests for a handheld device.

Main Menu 2 includes file management tools (including an on-screen QWERTY keyboard), fundamental frequency range of musical instruments (for high-pass filtering and EQ), and system setup (battery meter, back light, power saving, PC data link, etc.).

The analyzer can be powered by its internal rechargeable battery or by the included AC power adapter. You can select either manual or automatic shut-off of the power and back light.

If you power the analyzer from the included DC power supply, and the batteries are not fully charged, the analyzer will not turn on. So charge the batteries before use. With the unit turned off, the batteries die after three days. It's a good idea to charge the batteries after each use. Fred Canning, National Sales & Marketing Coordinator for Avlex, told me that Avlex Engineering is working on reducing the current drain so that the batteries will last longer.

On the analyzer are the LCD screen, function keys, a power button, power status lights, two mini phone-jack mic inputs, a power connector and a mini RS-232 connector.

The instruction manual is clearly written and has an exceptional layout appearance. It includes a helpful troubleshooting guide.

In Use

To use the analyzer as a self-contained unit, you must assemble it first. Screw a mic adapter plate onto the analyzer, screw on a mic shockmount, open a mic and place a battery inside, put the mic in the shock mount, and attach a mic cable to the mic and analyzer.

When you first power-on the unit, it is important to select the touch panel alignment. You tap the included pen on spots that show up on screen. That way the pen will activate the correct menu items.

At times, the analyzer can be awkward to use. Because the microphone attaches to the side of the unit, the weight is not evenly balanced when you hold the analyzer. Unlike a self-contained analyzer, the 4U2SET system has a number of components that you need to assemble and keep track of. [Avlex points out that the unit is not designed to be a handheld unit but a portable unit with more features than a handheld tester.]

Also, the controls and connectors are not labeled. Unless you can remember their function, you might want to label them yourself.

I will describe each of the test functions.

The Realtime Analyzer displays 31 bands from 20 Hz to 20 kHz, plus the overall level. Keys on the analyzer let you zoom in/out and shift the range. Weighting can be A, C, or flat. Touching a single bar in the graph pauses the display and shows that filter's level. You can save the RTA data to files and open them at a later date.

Several RTA files can be averaged, useful for equalizing a sound system. A suggested equalizer setting can be calculated from the RTA spectrum or the spectrum average files. You can set the desired slope of high and low-frequency rolloffs as part of the house-curve EQ.

A sub-menu called SET allows you to set RTA parameters for Channels 1 and 2. Decay time and vertical-scale units are adjustable. You can turn peak mode on or off, and overlay NC or equal-loudness curves on the display. The two channels can be displayed on the same screen, one above the other.

I even used the RTA function to equalize my car's sound system. The analyzer was straightforward to use once I read the manual. I popped the included CD into the car's CD player, played the pink noise track, and adjusted the CD player's tone controls for the flattest response.

The Sound Level Meter works with either one or two channels. Both a bargraph and numerical display are on-screen. There is a choice of scales, decay time, weighting, and peak hold. The measurement can be calibrated with a sound level calibrator (not included).

I used the SLM function to make sure that I was monitoring my recording mixes at 85 dB SPL. Mixes that are monitored louder than 85 dB SPL tend to sound weak in the bass and treble when played back at a lower level.

The Difference Analyzer lets you see the spectral and level differences between the two input channels, when each is fed a signal at the same time. As in the RTA function, you can adjust the weighting, scale, and decay time. Absolute mode displays the actual level difference between the two channels, while relative mode shows only the spectral difference.

Polarity check is easy to use. Play the positive-pulse track on the CD, and the screen indicates the speakerÕs polarity as + or - relative to that track.

Reverberation time can be measured handily as follows: Enable RTA mode. When the analyzer has measured the background noise level, it will say "Ready." Play pink noise (at least 50 dB louder than the background noise) for a few seconds and shut it off. The RT60 is displayed as an overall value rather than in frequency bands. You can take multiple measurements by pressing Next, then average their values. Results can be saved to a file and recalled.

The analyzer measures THD + N by comparing a sine-wave source on Channel 1 to the test device output on Channel 2. For example, you might plug a mic into Channel 2 and measure the THD of a loudspeaker, one frequency at a time.


The Avlex 4U2SET provides a very wide range of measurements in a handheld, portable device. Its dual-channel capability gives it more functions than most competing analyzers. For example, it easily measures transmission loss vs. frequency.

Because it is a system with many parts, it is more complex to assemble but more flexible than a self-contained analyzer. Like most other handheld devices, the 4U2SET unit lacks multiple-frequency RT60 testing and time-selective spectral measurements, which might limit its use by acoustic consultants. Still, for most users the Avlex 4U2SET will adequately measure sound systems, room acoustics, and many electronic devices.