Waves UltraMixer Model L2 Processor

The new Waves L2 hardware is based on the L1 software, known by almost everyone who's used the Waves processing available for Pro Tools, Premiere and other programs. I've tried some other digital limiters and the L1 was best at removing digital overs while raising level.
Publish date:
Social count:

The new Waves L2 hardware is based on the L1 software, known by almost everyone who's used the Waves processing available for Pro Tools, Premiere and other programs. I've tried some other digital limiters and the L1 was best at removing digital overs while raising level.
Product PointsApplications: Analog and digital recording; mixing; mastering; sound reinforcement; broadcast production; etc.

Key Features:
24/96 A/D-D/A, AES/EBU and S/PDIF interface; double-precision limiting algorithm; high-resolution version of Waves IDR dither


Waves at 423-689-5395; www.waves.com
There was, however, a limit (pun intended), and for discerning listeners, that was at around 3 dB of gain reduction. Any more action and we either heard distortion and serious loss of soundstage with short release times, or pumping and alteration of the internal mix with longer release times. There was no ideal release time for larger amounts of limiting.

Waves told me it was developing a hardware standalone product reportedly with significant improvements on the L1 algorithms. The company was interested in my comments on sound quality, and sent a preproduction model for review. After only five minutes listening - and pushing the heck out of the L2 just to see - I was astounded at the sonic improvements they had made.


The L2 is packaged in a black-faced two-rack-space box with large, easy-to-read LED readouts. It has both analog and digital inputs. The analog section is not a throw-in, but a serious quality offering, making the L2 suitable for use in analog-only production environments.

Analog I/O uses high-quality (24-bit) A/D and D/A converters with both balanced and unbalanced I/O, internal and external sync (via word clock), and the standard sample rates from 44.1 kHz to 96 kHz. A 24-bit digital I/O is on both AES and S/PDIF connectors, switchable on input, and both active on output.

Both digital outputs are set to the same consumer channel status, which means you may not be able to feed pro and consumer recorders at once. The entire chain inside has been extended to double precision (48- bit), including the dither. The 48 bits of dither are calculated, so telling the box to dither at 24 bits really does something - it's not just making noise.

The IDR Ultra algorithm has been extended to ninth order. The two channels may be unlinked for dual-mono operation, and an auto-release function has been added.

Most of the time I use a limiter at the end of a digital chain, so I have relatively little use for the L2's analog section, but I did some careful listening. The L2 has great potential in analog mix situations, including sound reinforcement and broadcast preproduction.

It can be used as a combination A/D converter and mix protection limiter. First, I confirmed that the bypass button really bypassed all DSP functions, with a bitscope and null test. Then, using reference-quality 1/2" master tapes, I compared the sound of the L2's A/D against my reference, a custom-built Ultra-Analog. I was pleasantly surprised. It's warm sounding and clean at 44.1 kHz and a little bit more open at the higher sample rates.

You can consider the L2 as a functional replacement for other well-known products that are primarily converters, as long as you don't need bit-split and ADAT-TDIF features. Waves has put as much quality work into the A/D side of its product as many manufacturers of standalone products, without all the other L2 features. This would be a bargain at twice the price, when you consider the other features.

The L2 DAC is less impressive-sounding than its A/D. With a low-jitter source, tonally, it is very accurate and smooth, better than the Entech Model 203 DAC I reviewed in PAR (8/99, p. 82) and better than many professional DACs costing much more. But the L2 DAC does not have the depth and spaciousness or quite the dynamics of my Ultra-Analog-based Counterpoint DAC. Nevertheless, because of its tonal accuracy, I give it a B+.

The L2 IDR (increased digital resolution, a form of noise-shaped dither) is impressive and represents significant improvements over the algorithms in the Waves plug-ins. The new Ultra curve sounds very neutral at 16 bits and would have become my instant favorite if I hadn't discovered the Weiss Engineering POW-R dither (PAR, 10/99, p. 46).

In fact, the new Waves Ultra dither is so good that it's converted a number of UV-22 lovers to noise-shaped dither because it has the tonal neutrality of UV-22 with far greater resolution. The L2 dither has a pinch less resolution (soundstage) than Meridian's Shape D, but better tonal neutrality. IDR should be left on at 24 bits, even when capturing 24-bit output from the L2, to prevent the loss of critical low-level detail. This results in up to 27-bit performance, according to Waves. My bench tests confirmed an improvement when dither is left on all the time, even with 24-bit sources.

The manual is comprehensive, though a bit repetitive; with careful editing it could lose about eight pages. The tutorial on dither is a must-read. I have some important objections to the manual. For a company so interested in maintaining fidelity, it's surprising there is little discussion on how to maintain signal quality at high levels, short of occasional admonitions to not overdo it.

The manual does not cover the many conservative uses for a limiter, from occasional use with classical music to protecting a sound system installation. More seriously, it encourages potential misuse of the product, and does not provide suggestions on how to detect signs of misuse.

In use

Though I miss the L1's ability to store and retrieve settings, the box is easy to use, with high-resolution, wide-range meters and peak-hold reset functions.

To properly evaluate a digital limiter we must use a pristine musical source that has previously undergone no compression or limiting, and audition on monitors that have excellent transient response, along with a DAC and power amplifiers with good headroom. If the L2 passes a listening test using transparent, minimalist-miked recordings - without losing the sense of depth, space and transient impact, then we can extrapolate it should do very well with more typical compressed multi-generation, multitrack recordings.

My first test was with Bill Alred's eight-piece jazz band, which I had previously mastered with processors including the L1.

This is audiophile material with great purity of tone. The producer and I could only tolerate about 3 dB of limiting with the L1 before reaching an unacceptable change of tonality in the trumpets and a loss of depth and space.

When I replaced the L1 with the L2, I was astounded to hear no audible degradation in transient response or tonality until we exceeded 7 dB of limiting.

Remarkably, the sound of the L2 remains warm and involving beyond 7 dB; though it becomes squashed, it doesn't become hard or edgy, as with some other limiters.

In the next few weeks, subsequent listening tests using the processor in the digital domain confirmed the L2's superb performance. I invited two experienced engineer/producers to audition 24-bit audiophile material that you would normally never process with a limiter.

We reluctantly agreed that with uncompressed, digitally recorded material, we could not detect up to 7 dB of limiting, no matter how hard we tried. I tested it at 44.1 and 96 kHz, with similar results - it was even more pure-sounding at the higher rate. The L2's ceiling control was adjusted for a unity-gain bypass in these comparisons.

With more conventional multitracked pop music sources I was astounded that the L2 could even be used as a compressor, because at 7-10 dB gain reduction the L2 still kicks, despite an infinite compression ratio! If you don't have a good compressor in your kit, you could use the L2 in an emergency or even in place of an 1176 limiter while tracking, without fear of digital brittleness.

The Alred project did not need more than 2 or 3 dB of limiting to reach a proper average level at a monitor calibration of 80 dB, but it's good to know we're not even pushing the capability of the processor.

Operating it conservatively - far from the threshold where critical listeners agree the sound is degraded - is assurance that no one will perceive a problem. However, I fear that many people will use the terrible power of the L2 to create super-hot, "squashed and small" recordings instead of using it to get even better sound quality. I admit that even when you overpush the L2, the sound is less harsh and more acceptable than with any other limiter I've heard. But that's a left-handed compliment. In the audio profession we should be dedicated to achieving quality over quantity.

I attribute the sound improvement to the double-precision dithered processing, and especially, the new auto-release algorithm. Auto-release algorithms for compressors are fairly useless for me, but for limiters they make a lot of sense. The L2 measures lower distortion on the bench when auto-release is turned on. I was never able to find a manual release setting that sounded as good as the L2's auto-release.


The L2 limiter is the best-sounding digital limiter I have ever heard. Its sound (or lack of sound) is transparent and warm, and it protects from overs while maintaining stereo space and depth with gain reductions that are impossible with any other product.

Bravo, Waves - although you've reopened Pandora's box - I commend you for the great sonics when the L2 is properly used