How do you make select monitors? By isolating the woofer from the tweeter, studying exhaustively which absorbent material to use (pore size, etc.), the exact length of the "tube" and, above all, the design of the output port. The goal is to avoid any unwanted coloration in the low frequencies, and to make the sound coming out of that port emerge IN PHASE with the sound coming from the front of the midrange driver.

PMC: The company
The British company PMC is one of the most specialized in the world in professional monitors and monitoring systems. One of the most innovative and revolutionary concepts in the development of its products is its exclusive, patented ATL (Advanced Transmission Line) technology. According to the company, this development offers perfect signal response, clarity and tonal perfection.

Looking through the list of international clients that use this company's gear gives us an idea of what “territory” it moves in. To name a few for reference: Bryan Ferry, Brian May, Capitol Records (Los Angeles), Delta Studios (Australia), the BBC, Abbey Road Studios (U.K.), BHF Sport, Gosh Studios (Vienna) and a long list of other artists and major broadcast and production companies.

Advanced Transmission Line
Let's briefly look at what ATL development involves. To produce sound, a speaker's driver needs to "separate" its rear and front sides according to the wavelength of the sound being reproduced. The ideal speaker would therefore need a wall 17 m wide to reproduce the lowest frequencies. Impossible to install anywhere. The solution? Enclose the speaker in a box (hence "speaker cabinet" or "acoustic enclosure"). At high frequencies there's no problem, but at low frequencies the drawback is that the sound pressure generated at the rear (that is, inside the box) prevents the speaker from moving, so there's no sound. To avoid this and be able to reproduce low frequencies, there is the transmission line, which is nothing more than a way of "tricking" the sound wave generated at the back of the speaker so that it doesn't interfere with the front, while also making use of that energy to improve the speaker's response.

Theory is one thing and practice another, since it usually works but only with very large enclosures (more space and more material to absorb that excess energy). Not to mention that the "theoretical design" would call for an enclosure of almost infinite length. The transmission line is turned into a set of S-shaped tunnels to make the most of the "spare" space inside the small enclosure (like a labyrinth).

PMC has developed this technique exceptionally well with ATL: isolating the woofer from the tweeter, studying exhaustively which absorbent material to use (pore size, etc.), the exact length of the "tube" and, above all, the design of the output port. The goal is to avoid any unwanted coloration in the low frequencies, and to make the sound coming out of that port emerge IN PHASE with the sound coming from the front of the midrange driver.

The result is excellent, since it achieves a very harmonious reproduction of low frequencies, incredible for an enclosure this size. There's no distortion, thanks to the ability to control air pressure at the rear and to allow the cone to move back quickly and freely.

The concept: DB1S-A
This is the smallest of the active nearfield monitor models introduced by PMC. The company claims that no other monitor this size offers such high-quality performance. A little further down we'll detail our impressions from the listening sessions we carried out with this and other monitors of recognized prestige.

A compact monitor packed with the luxury of the most advanced technology. It's offered as a solution for places where space dictates the size of the gear to be installed: small rooms where quality is a parameter that can't be neglected. An active, two-way nearfield monitor with 120W of power.

It combines traditional handcrafting, for the most meticulous processes, with the most advanced technology through computer-aided design. The aim is perfection, total stability at any volume and the radical elimination of any kind of unwanted coloration. You can visit the website www.pmcloudspeaker.com to browse more technical manufacturing details. There you'll find additional information about the careful choice of materials, types of soldering with optimal materials, detailed explanations of the systems' technological development and much more.

In practice
We had already had the chance to put other PMC products on the test bench. The previous review was of a higher-end product (and a higher-priced one, of course). The test results were extraordinary, although I personally didn't get to attend the listening sessions or take part in that test. The truth is I was left really wanting to hear those monitors (AML1) for myself.

The listening test
For the tests this time, we set up the monitors next to a pair of Mackie HR624s. After placing the DB1S-As in their optimal position, we selected the material we were going to listen to.

The way I usually get familiar with the response of monitors I don't know is by playing various pieces of very different character. I mean: acoustic songs, songs combining acoustic and electric, vocal passages, crystal-clear guitar passages, heavy music passages, and so on.

I tend to look for very natural acoustic instrument passages. But I also like to know how they respond on complex productions with extravagant compression and dynamics. The idea is to perceive clearly whether the monitors being tested are faithful, whether they accentuate certain frequencies in any way and, in short, whether they're really reliable.

Even without trying to set up a comparison between the two (four) monitors, I have to confess that the response is radically different. It's curious how, at times, two sets of monitors can both be valid and reliable for a mix while being so far apart.

Our impressions after playing a good number of pieces (many of them recorded in this same studio) can be summed up as impressive transparency. A crystal-clear feeling washes over us when we listen through these PMCs. The image the DB1S-As project is truly impressive. You get the feeling you can mentally place each musician playing the various tracks. We really liked this transparency. I don't think we've heard monitors that offered more detail and such impeccable definition.

As a mix reference they're really interesting. I say this because when you listen to a bad mix through this pair, the mistakes are highlighted considerably. This means they let us see very clearly where we're overdoing it, where we've fallen short, what's grating and what's missing.

What convinced us least was the pressure and impact of the sound. I'm convinced that choosing professional monitors should involve weighing several parameters: definition, clarity, sharpness, stereo imaging, power (depending on needs), etc. But in addition to these and other factors, we have to add a really important one: each producer's personal taste. By that I mean it's very important to work comfortably. First we have to decide whether we'll use the same monitors for recording and mixing or work with several pairs depending on the stage of production we're at. Once these points are settled (which may depend on budget), we should consider what kind of signal (all of them faithful, defined and pristine) we find most pleasant to work with.

In this respect, I think the Mackie HR624 and the PMC DB1S-A are polar opposites. With considerable quality in both cases, the former give us a punchy sound with great pressure. Without losing definition, the sound at high volumes is the kind that blows your hair back. In the case of the DB1S-A, its greatest quality comes in the form of sharpness and transparency. It's easy to locate each layer of each track, although the process becomes, in general, more scientific, and some may find it lacking in warmth. Hence my point about the importance of the “personal taste” parameter among high-quality options.

It should be stressed that the PMC cabinets under test are small and designed to provide an effective solution while taking up little space. Obviously, larger cabinets from this company will show more depth, action and character. In any case, I'm sure that PMC's greatest quality isn't pressure and energy, but the radical sharpness of the sonic “image”.

Conclusions
After working with various monitors, you ask yourself what the priority is. Knowing in advance that what you need is a true, clear reference, ideally the work should feel pleasant (not tiresome) when you listen. The ear gets very used to certain references, and when you switch so drastically from one type of sound to another, the impact is significant. Once you've spent some time getting used to them, in this case the PMCs, you start to grow very fond of them for their exquisite definition. I think I'd keep both pairs (I mean the ones tested and mentioned in this review), precisely because they're so opposite, contrasting mixes from one set of monitors and reference to the other. The trickiest part is the investment needed to put together such an appealing range of monitors.

Before finishing, I should mention that we also think the DB1S-A are excellent monitors for surround work (with the right number of units) thanks to their most brilliant characteristic: the perfect placement of each layer in the mix and their exquisite transparency.