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Lexicon MPX500

Dual-channel Effects Processor By Paul White
Published February 2000

Lexicon MPX500

Lexicon's new mid‑priced unit strikes a balance between the ease of use of their budget gear and the flexibility and sonic class of their high‑end products. Paul White gets an exclusive first look...

The quality of artificial reverberation effects makes a huge difference to the perceived quality of a finished project, especially where acoustic instruments are involved. High‑end studio reverbs, such as the Lexicon 240 and 480L models, have always been very expensive, though their mid‑price PCM90/91 models are popular with both project and professional facilities as they approach high‑end performance at a rather lower price point. Even so, one of these units will still cost you as much as a complete PC‑based studio, which is probably why Lexicon felt the need to introduce their lower‑cost MPX range. The Lexicon MPX1 is an established multi‑effects/reverb all‑rounder that started life at over a grand, but now sells for little over half its original price, while the more recent MPX100 is an altogether simpler device based on presets with limited editability at under £200. I think it's fair to say that the MPX100 set a new standard for very‑low‑cost reverb/effects, but although it sounds impressive for the price, if you put it up against a PCM90 or 91 you can hear straight away that the more expensive unit sounds richer, smoother and more spacious.

While the MPX100 is a fine reverb for the fiscally challenged project studio, the more serious user may demand a little more sonic refinement and more editability, which is why Lexicon developed the subject of this review — the MPX500. Based on the same Lexichip III reverb engine that powers the new generation of Lexicon reverb processors, the MPX500 expands on the MPX100's philosophy while offering a sound quality that lies somewhere between the MPX100 and the PCM90/91. So new is this processor that I had to visit the Lexicon factory in Boston in order to get my hands on one in time for this review, and while I was there, I was able to perform a direct comparison with other Lexicon products in a studio environment before bringing it home to do further tests. If the MPX100 sits at 1 on a scale of 1 to 10 with the PCM90 at 10, I'd say the reverbs of the MPX500 score a 5 or better.

The MPX500 is a mains‑powered 1U processor (no wall‑warts) with balanced analogue I/O on both XLRs and jacks, and S/PDIF digital I/O on phono connectors. The converters are 24‑bit and an analogue dynamic range of 105dB is claimed. The unit features stereo operation and the signal path provides a number of routing options, from stereo‑in, stereo‑out to dual mono‑in, stereo‑out or dual mono‑in, dual mono‑out. It's also possible to select from a number of dual effects connected either in series or in parallel and, in the case of series connection, to vary the amount of the first effect feeding the second: normally, the Effects Level parameter accessed via the third Edit knob in parameter page one sets the balance of the two effects in a dual effect program, but in serial configurations, it varies the balance of effect one/dry signal that feeds effect two. In this respect, the paradigm isn't very different from that of the MPX100.

MIDI In and Out/Thru connectors are provided for patch dumping, real‑time parameter control or tempo control, and live users will be glad to find a TRS footswitch jack that allows two switches to be connected for control over both bypass and tap tempo.

The MPX500 features balanced analogue I/O on jacks and XLRs, as well as S/PDIF‑format digital I/O.The MPX500 features balanced analogue I/O on jacks and XLRs, as well as S/PDIF‑format digital I/O.

The main operational difference between this machine and the MPX100 is in the degree of editing that's possible, although the system adopted is actually very straightforward and still far less comprehensive than for the PCM90/91 or the MPX1. Essentially, the LCD window shows up to four parameters at any one time, each of which can be directly adjusted via one of four rotary Edit knobs. The first knob in the first row is always designated as the Adjust knob, a concept existing Lexicon users will probably be familiar with. Adjust is generally mapped to change several parameters simultaneously in order to provide a straightforward and meaningful way of tweaking a patch if you don't want to get involved with too much editing; in some cases, Adjust even accesses parameters that aren't available in the standard edit menu. For many of the reverbs, it changes the apparent liveness of the virtual room by simultaneously altering the decay time, EQ and room size.

Pressing the Edit Pages button steps around a maximum of four screens, so it follows that each effect can have up to 16 different user‑adjustable parameters. The LCD also handles the input stereo metering and output‑level adjustment as well as showing patch name and location details. A further rotary control is used to step through the available programs, and the system setup page provides the option to have patches load automatically after just under a second when you stop turning the knob; alternatively, you can opt for the more traditional Lexicon approach of using the Load button to load in the selected patch. In all, there are 240 factory preset effects and effect combinations, with space to store 30 user edits.

If the MPX100 sits at 1 on a scale of 1 to 10 with the PCM90 at 10, I'd say the reverbs of the MPX500 score a 5 or better.

A new touch is the cue feature — if you select a new patch but don't load it, the display will switch back to showing the original effect after a few seconds, but the location of the new one is remembered (and displayed as being cued) so that it can be loaded at any time by hitting Load. This will be particularly welcomed by live sound users, as will the dual mono‑in, dual mono‑out mode. Other than that, there are relatively few controls. A Trim control provides a useful degree of input gain adjustment (though it isn't a conventional pot that goes down to full attenuation), while the System button accesses system functions such as the patch loading method, the way the bypass switch operates (Dry, Full Mute/Input mute), output level adjustment, MIDI functions, sample rate/external sync, input source and so on. You can also decide here whether the wet/dry Mix settings should apply globally or be set per patch: this option can be useful if you're working with a mixer and want to kill the dry sound for all patches.

A front‑panel Bypass button may be used instead of a footswitch, and in addition to the usual Load and Store buttons, there's also a Tap/Cancel button used for setting tempo‑related effects directly or for cancelling certain operations. Pressing Tap/Cancel and Store at the same time activates a MIDI learn mode that enables any of the 16 edit parameters to be linked to any continuous MIDI controller 1 to 31, 33 to 119, aftertouch or pitch‑bend. This is a very simple auto‑recognise routine that involves twiddling the edit knob relating to the destination parameter, then sending the type of MIDI controller you want to control it with. There's also a simple routine for clearing assignments that are no longer wanted.

The Tap button may be used to set the delay time or modulation rate of relevant effects, but these may also be locked to MTC or MIDI Clock.

Using The MPX500

I suffered a moment of panic when I first switched on the unit and was greeted by a uniformly green display window, but after adjusting the screen contrast using the rear‑panel twiddle pot, the display took on a more familiar appearance. I found the operating system of the MPX500 really friendly: there's more than enough flexibility to satisfy all but the most anorakish programmer, yet everything can be accessed so quickly that adjusting effects mid‑session is quite a trivial operation. Creating a new effect program is achieved by finding a preset that already uses the combination and routing arrangement of the effects you need, then editing it. If you're short on effects boxes, you can connect one aux send to the left input and another to the right, then use one of the dual effect modes to provide two independently adjustable effects that are either mono‑in, mono‑out or mono‑in, stereo‑out with both stereo outputs mixed together. The choices here generally break down into reverb plus something else or delay plus something else.

The MPX500 is designed to make editing straightforward. For each algorithm, the first of the four assignable edit knobs is designated Adjust, and controls several of the most important parameters together.The MPX500 is designed to make editing straightforward. For each algorithm, the first of the four assignable edit knobs is designated Adjust, and controls several of the most important parameters together.

There are a number of presets for each effect type (as indicated in the sidebar) and the algorithms are quite similar to those offered by the MPX100, with all the regular modulation, delay and pitch effects included alongside reverb. It's probably fair to say that the greatest improvement in quality over the MPX100 is noticeable on the reverb settings, which are generally denser and more spacious. In addition to the usual suspects of plate, hall, chamber and room, the unit offers its version of the classic Lexicon Ambience algorithm that simulates a live environment using a pattern of early reflections. This is a hugely useful treatment when you want a sense of space without adding obvious reverb.

One of Lexicon's proprietary tricks in producing smooth reverb or ambience effects is to slowly modulate the early reflection spacing using parameters called 'Spin' and 'Wander'. I'm not sure how (or even if) these are applied in the MPX500 algorithms, but there's no user control over them. However, the plate reverbs have independent left and right post‑reverb delay settings as well as pre‑delay, which can make for some interesting spatial treatments.

For quick‑and‑dirty reverb adjustment, the Adjust parameter in the first row generally affects the size or liveness of the virtual room, and often that's the only tweak that will be needed. However, if you need to get in deeper, the editability of the MPX500 means you can change things like the pre‑delay, decay time, attack shape, HF roll‑off, relative high and low decay times and diffusion very quickly. Most importantly, the reverbs have that true Lexicon character which helps keep a sound in focus while adding space.

The non‑reverb effects also stand up extremely well. The delay offers a choice of tape‑like high cut or straight delays, and the rotary speaker emulates the speed‑change rate of the real thing. The stereo chorus uses up to six delay taps to provide a really smooth, rich chorus, while flanging passes through the zero delay point, just as tape flanging does. Most of these non‑reverb effects sound quite similar to their counterparts on the MPX100, which I felt were very strong when I reviewed that unit, and the only obvious weak spot is the warble you get when using large amounts of pitch shift. Sadly this seems to be a fact of life for any pitch‑shifter costing less than a car, but it's perfect for detuning and ADT effects.


You can buy more versatile multi‑effects boxes than the MPX500 for around the same price, but I don't think any of them offers the quality of reverb available here. Similarly, the non‑reverb effects may provide nothing new, but they sound just right. Is the MPX500 an alternative, or even a replacement, for the more expensive MPX1? Their reverb quality is certainly comparable, but the MPX1 is a far more capable multi‑effects unit, with rather more depth to its editability. At the same time, more flexibility makes the MPX1 more time‑consuming to program, and for tweaking effects during a session, the MPX500 is about as close to perfection as you can get.

In fact, the only real criticism I can make of the MPX500, given its very attractive price, is its limited number of user memories. I'd recommend the MPX500 either as a second reverb/general effects box for someone who already has something better, or as a main reverb for the smaller studio owner who appreciates the benefits of a Lexicon reverb. I'm buying one to back up my PCM90!

Tap Timing

As with the MPX100, Lexicon have made it very easy to synchronize delay and modulation parameters in the range 40 to 400bpm. The current tempo rate is displayed in the LCD window, and the Tap Tempo button LED will flash at the appropriate rate. It's possible to set a global tempo for all the effects patches or to have each user program stored with its own tempo setting. Tapping the button twice will set a delay time equal to the spacing between taps up to a maximum of 5.5 seconds for a mono delay or half this for a stereo delay. You can also set up the unit to extract tempo from audio events by holding down the Tap button.

For those wanting MIDI control over tempo/mod rate, tempo can be derived from MIDI Program Changes, MIDI foot controllers, continuous controllers, MTC or MIDI Clock. The parameter set by Tap varies from preset to preset — sometimes it's a delay time, sometimes it's a reverb pre‑delay, sometimes it's a modulation rate — so you may need to read the manual at least once! Whether or not the unit syncs to MIDI Clock can be set in the System menu.

The Effects

• Plates 9
• Gated Reverb 10
• Hall Reverb 10
• Chamber Reverb 10
• Ambience 10
• Room Reverb 10
• Tremolo 5
• Rotary 5
• Chorus 5
• Flange 5
• Pitch 5
• Detune 5
• Delay‑Echo 15
• Special FX 15
• Flange‑Delay 10
• Pitch‑Delay 10
• Chorus‑Delay 10
• Delay‑Reverb 10
• Flange‑Reverb 10
• Pitch‑Reverb 10
• Chorus‑Reverb 10
• Mono Split Delay 15
• Mono Split Reverb 20
• Dual Mono 16


  • Approaches high‑end reverb quality.
  • Affordable.
  • Straightforward user interface.
  • Good‑quality delay and modulation effects.


  • My only quibble at the price is that having only 30 user memories seems a little sparse.


A good combination of sound quality, ease of use and price.


£449 including VAT.