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Zobel Active One

Active Monitors By Paul White
Published September 1997

Paul White auditions a new name in active monitors, and discovers an interesting design approach that combines light weight, small size and a well‑controlled bass end.

Active monitors come in all shapes and sizes and, despite the physical limitations of moving‑coil loudspeakers, the ingenuity of speaker designers never ceases to amaze me. As a result of their almost fanatical devotion to sonic 'truth', we now have a wide choice of remarkably accurate loudspeaker systems that are both compact and affordable. Currently, the active speaker is flavour of the month, and there's a strong argument to suggest that active monitoring is the best way to go, but Zobel have approached the design of their active system in rather an unorthodox way.

Realising that desk reflections can be a real problem when nearfield monitors are used, they've designed their Active Ones to have an almost letterbox‑like dispersion pattern so that, in effect, the sweet spot is very wide but covers a relatively narrow vertical angle. This is achieved by using two bass/mid drivers, one above and the other below the tweeter — though this configuration is by no means unique: it was first researched properly by Joe D'Appolito, whose name has been adopted to describe the arrangement. I suppose the theory is not dissimilar to that of column‑type PA loudspeakers, which have a similar dispersion pattern, but it does mean that the speakers have to be mounted upright — if you lay them flat on the meter bridge, the 'letterbox' pattern will be rotated by 90 degrees, narrowing the sweet spot and spraying sound all over the surface of the console. The manual makes this quite clear, but I'll bet some users will still try using these horizontally, just because they look cooler that way!

Measuring a compact 38cm x 20cm x 31.5cm and weighing a very manageable 10kg each, the Active Ones come as a right/left mirror image pair; to make transport easier, they have a tough strap handle fixed to the rear panel, plus there's a solid protective baffle that clips onto the front of the box to protect the drivers in transit. These provisions, coupled with the light weight of the boxes, makes this a very practical portable reference system; in all other respects, the construction appears to be similar to that of other ported cabinets.

There's no built‑in EQ to compensate for changes in the bass end due to positioning, but a sensitivity switch allows the user to select ‑10dBV, 0dBu or +4dBu operating levels from the XLR input. The mains inlet and the power switch are on the rear panel. Both bass/mid drivers are fed from individual power amplifiers. Few specific amplifier details are available, as the manufacturer would prefer to keep some things secret, but I'm told that the high‑efficiency drivers make it possible to use relatively low‑power amplifiers, which help keep the weight down. The feedback circuit topography of the amplifiers effectively eliminates output impedance, and the result is a very high damping factor and very tight driver control.

These are very revealing monitors: if something is amiss in the mix, there's every chance these speakers will let you hear it.

The bass/mid drivers are built for Zobel by a major European manufacturer, and feature woven carbon‑fibre lightweight cones in roll surrounds. The effective cone diameter is only around 10cm per driver, and both speakers have a ported acoustic enclosure.

At the high‑frequency end is a 25mm soft‑dome tweeter, again built to Zobel's own specification, matched in pairs. The high end is run at reduced power, with the amplifier running in Class A mode to eliminate crossover distortion at high frequencies, and a fourth‑order crossover (based on the textbook Sallen and Key circuit) operates at 3kHz. The result is a response that's flat within ±2dB from 55Hz‑20kHz, but the trade‑off is that the maximum SPL is limited to 98dB at one metre. Although this is quite adequate for sensible nearfield monitoring, there will undoubtedly be those who disagree with my definition of the word sensible. Thermal protection is provided to shut down the system if the amplifiers are allowed to overheat, and clipping is monitored by a red LED adjacent to the green power LED on the front panel.


Tested with a wide variety of source material, the Active Ones impressed me with their deep, well‑controlled bass end and detailed, articulate mid and high end. The transient response seems to be particularly good, and though this tends to result in a slightly forward sound character, the result isn't edgy or abrasive at realistic listening levels. Certainly these are very revealing monitors: if something is amiss in the mix, there's every chance these speakers will let you hear it. Providing you keep an eye on the clip LEDs, you can get a quite a lot of level out of the Active Ones at the regulation one‑metre listening distance, but the tonality does start to become a little more brittle as the maximum level is approached. There's also quite a noticeable difference in tonality if the speakers are positioned for a seated monitoring position and you stand up. This is to be expected, due to the deliberately restricted vertical dispersion angle, but if you have to stand up to adjust effects or equalisers, it's something you have to remain aware of.


Zobel's Active Ones are priced to compete with the smaller and better established Dynaudio and Genelec active monitors, which means they're not going to have an easy run, but I get the impression that a lot of serious thought has gone into their design, and they are extremely good at their job. For me, their main strength is their revealing, detailed character when used at modest monitoring levels of 85‑90dB; considering that these are fairly small nearfield monitors, they deliver a creditably stable bass end. Stereo imaging is also good, and the integral carrying system should appeal to producers looking for a mobile reference that's easy to transport and set up. Some will find the maximum SPL a little limiting, and certainly the tonal smoothness suffers a little if you work these speakers near their limits, but used within 'safe' monitoring limits (sustained average levels of over 90dB are considered to be harmful to your hearing), they sound crisp and well integrated. You can certainly buy more flattering speakers, but Zobel's specific design aim was to deliver a reference you could trust to pinpoint any weaknesses in your mix, and in my view that's exactly what a good studio monitor should be. It's certainly worth calling Stirling to book a demo.


  • Detailed sound with an even bass end when used at moderate listening levels.
  • Compact and portable.
  • Handle and in‑transit driver protection baffle supplied as standard.


  • Sound quality tends to become noticeably harsher when the level is close to clipping.


These are very revealing monitors with a useful amount of bass extension, suitable for the discerning user who doesn't want to monitor at deafening levels, and who values portability.