Spirit Absolute Zero

Spirit's new baby monitors incorporate some of the design principles used in pro monitors costing many times the price. But have too many corners been cut to keep the price so low? Paul White finds out.

How do you build a cheap monitor that sounds brilliant, delivers plenty of bottom end, goes as loud as you like, and produces an accurate representation of what's fed into it? If you know the answer, you know a lot more than the people who actually build loudspeakers, because using existing technology, low cost invariably means compromise in some areas. The trick is to keep the consequences of compromise to a minimum. Another neat trick is to have a parent company that owns at least two of the world's foremost loudspeaker driver manufacturers!

Design

Spirit's previous Absolute 2s (see SOS March 1995) have done very well as project studio monitors for the budget conscious, but now the company have decided to add to the range by bringing out a smaller, cheaper model. The Absolute Zero is no bookshelf speaker, though: its twin drivers still manage to cover the 55Hz‑18kHz part of the audio spectrum, while delivering a respectable level from amplifiers rated at up to 95W per channel.

There are two slightly unusual features of this monitor: the rear bass port (which saves front‑panel space and reduces mid‑range coloration), and the acoustic waveguide tweeter baffle, the latter being designed to control the listening angle so that the tweeter doesn't have a wider dispersion than the bass driver at the crossover point. The design of this waveguide also sets the driver back from the baffle, allowing it to be time‑aligned with the bass driver. This waveguide approach isn't new, of course — Genelec, for example, have been using waveguide technology for a long time.

The tweeter is a 25mm, 'catenary' profile soft‑dome unit. 'Catenary' describes the mathematical curve which results when you hold a piece of string at the ends and allow it to sag in the middle. Arches built using this curve are very strong, because forces are distributed directly along the curve, so that the material is compressed rather than being subjected to shearing or bending. In the context of a tweeter, this obviously helps to avoid dome deformation when the tweeter is driven hard.

At the bass end, there's a 170mm driver with a 30mm voice coil and a soft roll surround. The cone is made of paper, with a metallic red paint finish and a reassuringly heavy magnetic structure. Conventional porting technology is used to tune the cabinet, which itself is built from laminated particle‑board with rounded front edges to help reduce cabinet‑edge diffraction. This method of cabinet construction is quite cost‑effective and is used in many consumer speaker systems.

A much under‑rated component in any speaker system is the crossover: Spirit have chosen a fourth‑order, Linkwitz‑Riley response because of its sharp roll‑off characteristic and lack of phase shift at the crossover point. Because the crossover operates at 2.5kHz, many critical mid‑band musical and vocal sounds overlap the crossover point, where they are likely to illuminate any shortcomings in the design. Connections to the crossover are via a rear‑panel terminal strip fitted with gold‑plated binding posts that will accept either bare wires or banana plugs.

Performance

Accepting the limited bass response of this type of design, the Absolute Zeros actually hold up very well, delivering a generally well‑balanced, detailed sound, marred only by a hint of harshness, which seems to be concentrated around or just above the crossover point. Given the price of these speakers, this coloration isn't very serious.

The Absolute Zeros actually hold up very well, delivering a generally well‑balanced, detailed sound.

At the bass end, the sound lacks a little punch at very low listening levels, but delivers a more satisfying kick when the speakers are asked to work a little harder. You don't get the same depth as from full‑range monitors, but then most domestic studios perform so unpredictably with full‑range speakers that you're probably better off using a smaller monitor. A modest power amplifier delivers adequate level for near‑field work — the sensitivity is quoted as being 89dB/2.83V/m when operating into 'half space'. This simply means when the backs of the speakers are close to a wall, in order to exploit any low‑frequency reflections and increase the SPL at the bass end.

Stereo imaging is generally good, and you can move around the listening area without the sound changing too much. Moving too much to one side of the 'sweet spot' causes a drop in level, as you'd expect, but the overall sound character remains pretty even. On balance, the Absolute Zeros paint a pretty accurate picture of what's going on in your music — and after all, that's a monitor's job.

Verdict

By adopting consumer hi‑fi construction techniques, and by sourcing drivers from within the Harman parent company, Spirit have managed to produce a very creditable‑sounding monitor right at the bottom end of the project studio monitor price range. While there may be small flaws in the overall detail of the sound, when compared with top‑end monitors the 'broad strokes' representation of the source material is actually pretty good, with only the edginess in the upper mid, which I mentioned previously, detracting from an otherwise smooth performance. If these speakers had cost three or four hundred pounds, I think I'd have been justified in being a little more critical, but at only slightly over £200, they look imposing and represent very good value.