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Alesis DEQ230D Digital Graphic Equalizer

Alesis has come up with a highly impressive 1/3-octave graphic EQ and real-time analyzer. With the DEQ230D, you can see a speaker's response and flatten it, reduce feedback, tweak an instrument's timbre, enhance a mix, filter out hum and noise, or create tonal effects. You might even put the device in a monitor chain to emulate various speakers.

Alesis has come up with a highly impressive 1/3-octave graphic EQ and real-time analyzer. With the DEQ230D, you can see a speaker’s response and flatten it, reduce feedback, tweak an instrument’s timbre, enhance a mix, filter out hum and noise, or create tonal effects. You might even put the device in a monitor chain to emulate various speakers.
Product PointsApplications: Studio, installation, live sound

Features: Two-channel; 30-band; 1/3-octave; programmable

Price: $449

Contact: Alesis at 401-658-3131, Web Site.

The DEQ230D ($449) allows you to edit the gain in any frequency band or group of bands, save the resulting EQ curve as a user program or recall factory EQ programs at the touch of a button. The unit is intended for recording studios, portable PA, touring sound and amplified instruments.

Its two channels of equalization can be independent or linked. Each channel has 30 1/3-octave EQ bands from 25 Hz to 20 kHz. Each band can be boosted or cut 12 dB with constant Q (bandwidth), and each band has an LED bargraph display. The device includes 30 preset EQ curves and 30 user-programmable EQ curves. Note that the DEQ230D displays its frequency-response curve on multiple LED bargraph meters. An analog graphic equalizer indicates its curve by the positions of its boost/cut knobs.

A one-rack-space device, the DEQ230D has a clean, contemporary look. Controls on the front include power, bypass, a Select button for each band, up and down buttons to adjust gains and select program numbers, a Link/Exit button to apply Channel A changes to both channels, and a Store button to store user EQ curves. Signal and clip LEDs show signal presence and clipping. By pressing multiple buttons, you can adjust master level and channel level. A numeric LED display shows either the program number or the amount of boost/cut.

On the back are connectors for AC power, two channels of balanced TRS analog line in/out, S/PDIF in/out, and MIDI in/out for MIDI control. A +4/-10 level switch adapts the unit to connected equipment.

A lower-cost version, DEQ230, omits digital I/O, MIDI, RTA mode, and the +4/-10 switch. It works with a separate power-supply adapter.

The DEQ230D is packed with advanced features. A Lock function prevents others from changing settings. Real-time Analysis (RTA) mode displays the spectrum of the audio signal. The digital output can be set at 44.1K or 48K sampling rate. When storing a user program, settings may be copied from Channel A to Channel B. You can configure the editing modes to suit the way you work.

The device can be used as an A/D converter between an analog mixer and digital recorder, or as a D/A converter between a digital mixer and power amp.

As for other features, Band Solo allows you to apply full boost or cut to a selected band, helping you to isolate it by ear. Audition mode lets you choose certain programs and put them into an Audition List, which you use to audition only the programs you want to hear. Pressing Bypass not only removes EQ, it also compensates for the perceived volume change of the EQ.

The DEQ230D functions as a real-time analyzer as well as a graphic EQ. To see the spectrum of the output signal, just press the two leftmost band-select buttons. Press Bypass to see the spectrum of the incoming signal. RTA metering modes include one-second peak hold, two-second peak hold, no peak hold, and hold peaks continuously.

There are several more features that we will not go into here, such as relative gain display and even a blinking light show. A lot of thought has gone into this product.


Published specs are impressive: signal-to-noise ratio is >96 dB A-weighted, THD and noise are < 0.005% and frequency response is 22 Hz – 22 kHz ±0.5 dB. Digital I/O is 24-bit resolution with 28-bit internal processing.

I found the DEQ230D fast and easy to use. Right after unpacking the unit, I was able to make connections and do basic EQ without reading the manual – with one exception. It would not store my user settings when I pressed the Store button. That is because I needed to press Store, select a program number, then press Store again. The manual explained this and also helped me access the advanced features.

Here is a typical equalizing procedure with the DEQ230D:

1. Start with a flat EQ curve by pressing Up and Down simultaneously.

2. Select a band you want to adjust by pressing the button under that band. (Multiple bands can be selected as well).

3. Adjust that band’s gain by pressing Up or Down. The band’s LED bargraph meter responds accordingly.

4. Repeat this process for all the bands you want to adjust.

5. Press Exit if you want to hear the result without storing it. If you want to save your settings, press Store, press the Up or Down button to select a program number, and press Store again.

You can recall the stored program with the Up/Down buttons. Programs 55 through 59 are blank and can be used for storing programs without overwriting the factory presets. Alesis made it easy to find programs quickly: press and hold an Up or Down button for rapid scanning. Another method increments program numbers in steps of 10.

The DEQ230D comes loaded with 30 useful EQ curves with names like “Smile,” “Darken,” “Comb Filter, ” “Hum Reduction” and “Megaphone Bandlimit.” I think their characteristics were well chosen, and it was entertaining to try them out.

I noticed that the unit sounded clean and the EQ curves were easy to read from a distance.

The operation manual is very thorough and clearly written. It covers features, safety, quick-start, connections, EQ operations and theory, advanced modes, applications, troubleshooting and specs. It even includes charts for logging program settings. Some applications described are “rock kick drum,” “telephone sound” and “tape hiss removal.”


The Alesis DEQ230D is easy to operate and sounds clean. What is more, it lets you instantly see and hear a variety of EQ curves, which is highly educational. This makes it a great teaching tool for audio schools. Major features are its RTA display and its ability to store and recall EQ curves. Thanks to that recall feature, you can instantly configure the unit for a variety of applications. I highly recommend it.