HHB Circle 3

The Circle 3 nearfield monitors are the latest fruits of the collaboration between HHB and Harbeth. Hugh Robjohns tries them out.

Avid readers of Sound On Sound will recall our review of the Circle 5 active monitors back in January; that model is based on the very popular Harbeth Xpression DPM1 monitor, and is available in both active and passive versions. The latest addition to HHB's line is the Circle 3 — also available in both active and passive formats — which has been styled to maintain the distinctive appearance of the Circle 5, but in a much smaller package. HHB's own‑brand monitor line‑up will soon be completed with the imminent launch of the Circle 1 powered subwoofer.

The Circle 3 is intended as a cost‑effective nearfield monitor, and the passive version reviewed here competes in the same kind of market area as the Alesis Monitor 1, JBL 4206, Spirit Absolute 2, Tannoy System 600, Yamaha NS10, and my own nearfield reference, the PMC TB1S. The speaker is a very modest 270 x 175 x 197mm (hwd), and finished in a hard black paint. Designer Alan Shaw has used off‑the‑shelf components in this model, the target price and physical size making the use of his own bass/mid driver design impractical. Thus, the LF unit is a commercial 110mm paper‑coned Vifa design with a 25mm voice coil, and is complemented with a 25mm soft‑dome Audax tweeter with ferrofluid cooling, aluminium voice coil and neodymium magnet. Both units are magnetically shielded to allow use in close proximity to TV monitors and moving‑coil meters.

The Circle 3 has a moderately low sensitivity of 83dB/W at 1 metre (the Circle 5 passive manages 87 and the PMC TB1s a healthy 90dB/W) and, consequently, a fairly powerful amplifier is an advantage. I would recommend something capable of at least a comfortable 60W or so.

The relatively low sensitivity is because of the way Alan Shaw has chosen to provide a sensible bass extension, given the modest size of the cabinet. This required a reduction in the mid‑band level of the bass/mid driver, to maximise the low‑frequency performance, and consequently the overall speaker sensitivity is lower than is normally the case. Rather than opt for some kind of porting technique to bolster up the low end, the Circle 3 uses an infinite‑baffle enclosure (ie. a sealed box) — a direct result of Shaw's positive experiences with the classic BBC‑designed LS3/5A nearfield monitor, which Harbeth manufactured under licence. As a result, the bottom end rolls off very smoothly with a gentle Q of only 0.7 (a classic Butterworth curve in fact). The specifications quote a ‑3dB point of 70Hz, but there is meaningful bass for some way below this, and the advantage is that what you hear is what is actually in the audio signal — not an artificially bolstered and flattered version of it!

The Audax tweeter is the best quality speaker available for the price, with staggeringly good matching between units (better than +/‑0.2dB), and also the smallest face‑plate. The Morel tweeter used in the Circle 5 could not be employed in the Circle 3 because its front plate was almost as big as the chosen Vifa bass driver, and would obviously have upset the Circle speakers' generic baffle styling.

The terminal panel at the rear of the speaker carries a pair of heavy‑duty binding posts for bare wire connection.Choosing drive units is only a small part of the art of speaker design, and the real key to making a system work properly is the crossover. The two drive units integrate at 3.5kHz with critically damped filters to avoid ringing in the electrical circuitry, and the tweeter crossover incorporates time‑alignment, since the tweeter is physically in front of the voice coil for the bass driver. Top‑quality components have been used throughout, and the acoustic filtering performance (ie. the combination of drive unit rolloffs and the electrical filters together) amount to slopes of about 18dB/octave.

The terminal panel at the rear of the speaker carries a pair of heavy‑duty binding posts for bare wire connection. These also provide sockets for conventional 4mm plugs — but only after a pair of infuriatingly stubborn plastic bungs have been taken out. These proved too small and tight for removal with fingers, and too slippery for pliers: I resorted to using a pair of small wire‑cutters to ease them out... eventually! Apparently, European regulations decree that 4mm sockets must be protected in this way lest some lunatic tries to plug in a European‑style mains plug! My frustration already evident, I shall not comment further...

Listening

The proof of the pudding is in the eating — or listening, in this case — and the Circle 3 is a smashing little speaker, provided you accept it for what it is: a nearfield monitor speaker. On first listening it will probably not impress in the way a typical bright, compressed, overblown small speaker often does. However, it is remarkably neutral‑sounding, with a lovely transparent open mid‑range, fine stereo imaging and lots of detail — all of which shine through after just a few minutes of listening. The deep bass is essentially absent but there is more than enough clean, articulate low‑frequency information to make reliable decisions about what is going on, and to tune and balance equalisers effectively. Indeed, I found the Circle 3s were able to reveal some subtle aspects in the low‑mid region of a mix that remained obscured on my TB1s.

...it is remarkably neutral‑sounding, with a lovely transparent open mid‑range, fine stereo imaging and lots of detail...

The speaker can actually go pretty loud too, managing close to 110dBA in the mid‑range — only a few dBs shy of the Circle 5s' peak output capability! Impressive as these figures are, they have little relevance in the real world — in practice the Circle 3 will be used as a nearfield monitors, where no one in their right mind would want to listen at anything like that kind of level (I hope). However, the fact that the speaker can accommodate peaks of that magnitude is good news, and means that transient signals can be portrayed without dynamic compression, assuming the amplifier is up to the task — hence the need for something with a bit of meat behind it.

The acid test for speakers is to listen to some well‑recorded speech, as any mechanical or electrical imperfections tend to be readily apparent. As I expected, the Circle 3s performed well in this test, particularly so when considering their price. Much of this is probably due to the choice of a paper cone rather than a more typical polypropylene design: paper cones seem able to convey voices with greater naturalness than most polypropylene cones, and Alan Shaw certainly knows how to extract the best performance from such modest components.

With more complex music signals, the Circle 3s manage to produce a believable and stable sound stage with reasonable depth (on suitably recorded sources), and with the clarity to hear inside the music to the individual components. Obviously, there is a limit to what can be achieved from a box of this size and with drivers at this price and performance level, and that limit can be reached with reasonably complex and intricate material. However, in the right context, these really are cracking little speakers and the passive Circle 3 is perhaps the ideal choice for anyone working in a very restricted space or on a tight budget who is happy to work at moderate levels in the near field, and who wants accurate monitor loudspeakers worthy of the name.

Assuming the active version of this speaker is at least as good as the passives (and in all probability, it will be slightly better), HHB have put the cat amongst the pigeons, facing up against two very popular contenders, the Spirit Absolute 4s and the Genelec 1029A (see box). For both active and passive versions, the magnetic shielding is an important bonus, and the option of adding the imminent Circle 1 subwoofer to a pair of active Circle 3s at a later stage is attractive. Indeed, a further elevation in quality could come from the subsequent addition of three Circle 5s for the front trio in a well‑matched surround‑sound monitoring setup.

I am a fan of the Harbeth school of loudspeaker design, having been extremely impressed with all of the company's top‑end offerings. These diminutive monitors certainly don't disgrace the range in any way, providing many of the essential qualities of a true reference monitor at a very affordable and attractive price. The styling is distinctive and attractive, the sound quality is well balanced, natural and revealing, and I'm told that purple is the fashionable colour for this season too!