B&W; CDM1

B&W's new hi‑fi speakers turn in an impressive performance as small studio monitors as Paul White discovers. But can they compete with the dedicated monitors already on the market...?

B&W are one of the few British hi‑fi loudspeaker manufacturers who have managed to maintain a prominent market position while sticking to basic engineering principles, rather than following the quasi‑mystic fashions of the hi‑fi tweaker. The CDM1s under review might look a little unusual, but even the cabinet shape is based on established principles, and the speaker system itself is a fairly conventional, two‑way, passive arrangement in a ported cabinet. Although designed as hi‑fi speakers, the CDM1s are quite capable of producing monitoring level SPLs when used in the near field, and the tonal integrity holds together well up to surprisingly high levels.

At the heart of the system is a 165mm bass/mid driver comprising a woven Kevlar cone suspended in a substantial die‑cast basket, and driven by a 31mm voice coil. Handling the top end is a free‑mounted, 26mm, alloy dome tweeter, incorporating a high‑power voice coil working in a magnetic fluid‑filled gap for cooling. Feeding the two drivers is a passive crossover, which, when combined with the natural characteristics of the drivers, produces a 4th order filter characteristic with a crossover point at 3kHz. The resulting system has a usefully wide frequency range, covering 64Hz to 20kHz +/‑ 2dB, and is only 6dB down at 46Hz and 25kHz. This isn't as extended as you'd expect from a larger mid‑sized, or main monitoring system, but is more than adequate for nearfield work, and is much less likely to excite modal resonance problems in small rooms which have little, or no, acoustic treatment.

Considering their small size, the CDM1s are surprisingly efficient at 88dB for 2.83V input at 1m, which, in non‑technical terms, means that an amplifier capable of delivering between 50W and 120W will give you sufficient wellie for monitoring without clipping. For hi‑fi use, you can go as low as 30W per channel, but in the studio, I'd be inclined to think along the lines of 75W a side, or more, unless you are in the habit of always monitoring at restrained levels. Although nominally rated as 8Ω speakers, the impedance drops to almost half that value near resonance, so be sure to use an amplifier capable of driving 4Ω loads or below.

The cabinet itself deserves comment, as apart from being very stylish, the radiused edges are there to reduce cabinet edge diffraction, and while the sloping tweeter baffle may look like a cosmetic add‑on, it was probably introduced to deflect baffle reflections away from the listener. The tweeter itself is free‑mounted (not fixed directly to the baffle), so that it still points directly forward, and a mesh dome is fixed over it for protection.

Connection to the speakers is via chunky terminals on the back panel, and two sets of terminals are fitted for those who prefer bi‑wiring. The holes in the terminal (which accept either bare wires or banana plugs) are generously large, and should accommodate all but the most esoterically butch speaker cables.

Performance

I tested the CDM1s using an amplifier rated close to the top end of their power handling range, and found that I could achieve quite deafening monitoring levels without the clip LEDs so much as winking at me, but in order to preserve what's left of my hearing, I quickly dropped the level to something more sensible, and put on the usual selection of test CDs. Overall, the speakers deliver a well‑balanced tonality, which makes them very suitable for general purpose mixing work, with the usual caveat that the bass lacks any real depth, and even though it does pick up at higher listening levels, there's still no real punch.

As I have said on more than one occasion, loudspeaker design is about balancing compromises, and in the case of the CDM1s, some of the compromises show if you listen for them. For example, such bass as there is can start to sound just a hint 'tubby' when you crank up the level, and if you gently tap the cone of the bass driver with the amp switched off, the resulting pitched thud seems to be at the frequency of the offending tubbiness, which suggests the system is a little under‑damped. This effect is only slight, and by no means spoils the performance of these monitors, but at £600 a pair, it is something you should be aware of.

The top end is surprisingly smooth for an alloy tweeter, but still isn't as smooth as you'd expect from a well‑designed, soft‑dome tweeter. On well‑mixed material, you notice just a slight lack of focus in the upper registers, but on anything that's mixed over‑brightly, the sound takes on a slightly ragged edge, hinting at something misbehaving in the 5 to 7kHz part of the spectrum. Compared with some established nearfield monitors, this effect is fairly subtle, but it still needs to be mentioned.

On balance, the B&W CDM1s are a good example of small loudspeaker design, and even though they're not perfect, they do acquit themselves pretty well. For a user working in a small room with limited space, the CDM1's are a viable choice for nearfield monitoring, although I have to admit that given this kind of budget to spend on a monitoring system, they wouldn't be top of my list. Perhaps the high price of the CDM1s is partly down to the stylish cabinet construction, but in the studio, most of us are more concerned with value for money and sound, than appearances.