Wilson WATT loudspeaker

Landmarks in speaker design have been few and far between. There are a few certain contenders: in the UK, the original Quad Electrostatic and the ESL-63 qualify, while the Celestion SL600 scored a big point for all small monitors; the Spendor BC1 changed forever the notion that cone speakers were always colored and that big boxes were essential for good sound. In the States, Apogee has taught us much with their surprising mid-treble ribbon-based designs. Other technologies have shown promise but have not achieved real commercial success.

On the basis of reputation and personal experience, I had begun to suspect that the Wilson WATT would represent another such step forward. I knew from my own experience at the 1987 Chicago CES that the WATT was impressive; it was demonstrably one of the best speakers at the show despite its small size, proving capable of breathtaking clarity, transparency, and depth with appropriate soundsources.

I therefore awaited their delivery with some eagerness, cursing early delivery delays. However, they arrived at last, and some introduction is now in order. Notwithstanding the suggestions to the contrary in Stereophile's "Letters" columns, I certainly appreciate the merits of good, big speakers, and regret that nowadays there are so few of them that I can live with. I also enjoy small monitors, but only if they possess genuinely musical characters. In some respects, then, I was likely to be sympathetic to the WATT rather than dismissive, and would be prepared to take it to the limit in order to assess the full measure of its potential.

For such a small speaker, the WATT is incredibly heavy, dense, and inert. In fact, it feels as if it were made from solid concrete, an impression conveyed by its laminated construction of mineral-based panels and lead blocks. Gilbert Briggs, the founder of Wharfedale, always said that you could never fully appreciate the potential of a speaker driver until it was mounted in a brick enclosure. Certainly this was the case with the WATT, since its raw drive-units are well known but have never been mounted in such a manner before. In this approach, the WATT contrasts the philosophies of an independent US designer and a Japanese corporation. The Corporation approach to designing a costly miniature would be to "reinvent the wheel," applying a range of expensive and complex new drive-unit technologies, and employing costly cosmetic and engineering tooling wherever possible. Without fear or favor David Wilson has chosen to use two inexpensive but substantially good off-the-shelf drivers.

Wilson provides a 25-page treatise on speaker positioning and use which is guaranteed to improve the subjective performance of any speaker system, let alone the WATT. The difference between relatively casual positioning and listening and a precisely controlled placement of enclosures and subject is not a trivial one, assuming that the speakers themselves have excellent time-phase characteristics and are very well matched. Lock-in image focus based on accurate placement is also a major characteristic of low-diffraction miniature speaker systems.

Following the commercial introduction of the WATT, some comments were made concerning a lightness of tonal balance which was said to be addressed by an accessory generally known as the "Beard" or "2Pi Panel." This comprises a plate fixed to the lower front panel which extends the effective baffle area. The forward radiation characteristics are thereby improved by 1dB or so in the lower midrange, the aim being to fill out the tonal balance.

Superb stands are essential, Wilson recommending a solid box-section type such as the 24" "Gibraltar." I achieved good results, however, by using 24" custom Foundation Pi stands—heavy two-pillar jobs, with a lead-sand filling and a welded, heavily reinforced base plate. The latter was firmly spiked to the floor, while the upper plate was well keyed to the speaker underside via three TipToes (alloy cones). Placement on a solid subwoofer box such as the Entec can also work well. We tried the laminated body of the Ariston QLN woofer (a non-production item), but Wilson Audio has its own proposal for a subwoofer portion. They suggest the Entec SW5 placed against the back wall, with dedicated, low-coloration stands devoted to the WATTs. As the instruction manual correctly points out, the best stereo focus and definition will be obtained with free-space mounting well clear of the nearest wall boundaries—we found 3.5 feet from the side walls and 2.7 from the rear wall to be the most effective. Wilson also notes that a stronger 2Pi boundary improvement (footnote 1) can be obtained by floor mounting, this improvement in tonal "richness" achieved at the expense of pretty severe mid-treble coloration due to the comb-filter acoustic response imposed by the proximity of the speaker to the floor boundary.

It is said that the WATT was primarily designed for use as a desktop nearfield studio monitor, which is a very different acoustic environment from stand use in rooms at a normal listening distance. That may explain some of the emphasis placed on extending the tonal balance, for example the solid stands, the 2Pi Panel, etc. Should the WATT sold for domestic use require such artifices in the first place?

If we take the view that the cabinet is a superb example of controlled nonresonant clamped-wall technology, then what is the logic behind attaching an unclamped open panel such as the "Beard" or placing the speaker on a solid base, when an open stand can offer lower coloration? Some answers to this question will be found in the section on sound quality. In vibration terms the Beard may contribute more resonance than the entire cabinet, due to its unsupported nature.

As regards amplifier interfacing, two points arise. One concerns the rear port which is effective at low frequencies. Two types are supplied, one for high-damping-factor (100–400) solid-state amplifiers and the second with a different tuning intended for use with amplifiers that possess a higher output impedance, eg, valve models and hence a lower damping factor between 20 and 80. A damping factor of 80 relates to an output resistance of 0.1 ohm for an 8 ohm load; equivalent to a DF of 40 for a 4 ohm system like the WATT.

Interesting as this port option is, a few points are worth remembering. Most valve/tube amplifiers have output resistances of 0.2 to 0.4 ohms, whether set to a 4 ohm transformer tap or not, resulting in an effective damping factor of 20 to 10 for the 4 ohm WATT impedance. This figure does not take into account the loop resistance of the speaker cable. With high-damping-factor amplifiers, the low output resistance—eg, 0.05 ohm—cannot be applied to the speaker terminals except by feedback-sensing cables or by using very, very thick, short cable. Once in the box, the bass-unit voice-coil winding offers a minimum electrical resistance of 3.2 ohms (for a 4 ohm system), this appearing in the cable amplifier loop. This is why the sum of the cable and amplifier output resistance has virtually no further effect if held below 0.3 ohms for an 8 ohm system, and 0.15 ohm for a 4 ohm one.

While on this subject, the WATT manual notes that this 4 ohm speaker has an impedance dip to 1 ohm at 2kHz, which in my view represents a severe imposition to place on any amplifier. The manual suggests that direct-coupled Futterman and similar tubed amplifiers are inappropriate, but gives the OK for other tube models when used on their 4 ohm tap. I have to disagree. A 1 ohm load severely limits the output power from a tube amplifier. For example, a 100W output (17dBW, 8 ohm) into a 4 ohm load will typically fall to 7dBW, or 10W in level terms, when faced with 1 ohm. Simply, this means that the amplifier will clip 10dB earlier if a strong musical signal appears at 2kHz, which is not unlikely, since this frequency is well in the main music power band.

Let us also assume a typical case where the tube output impedance and cable loop are limited to 0.4 ohms. Overall there is a loss of 0.8dB over the whole range, but at the 2kHz minimum impedance the loss increases to nearly 3dB, this inducing a dip in acoustic frequency response of 2.2dB which may well alter the sound of the speaker.

Given these observations, I suggest that the WATTs be used with heavy, low-resistance cable and with low-output impedance, highly load-tolerant solid-state amplifiers if consistent results are to be obtained. More sonic variation than usual can be expected with differing speaker cables.

Design and Build
This compact two-way speaker encloses a small internal volume of approximately 9 liters, reflex-tuned in the 40Hz region by a ducted port mounted on the rear panel. The main port used, the "100-400," has a 1" exit of small flow capacity, backed by a sensibly short 2" duct. Larger port-length:duct-diameter ratios encourage rectification and back-pressure distortion.

Built on a diecast magnesium-alloy chassis, 175mm in diameter, the Norwegian SEAS bass unit is fitted with a 1" motor-coil, with a shallow, near-straight-sided soft-pulp cone of 125mm effective diameter. The front surface is factory-finished in a damping coating, the surround comprising a synthetic rubber half-roll. A generous magnet is fitted to give strong electromagnetic control of the bass-reflex loading.

Footnote 1: The "Pi" nomenclature refers to the solid angle in radians into which the speaker radiates. A speaker well away from all boundaries effectively radiates into a sphere, hence the 4Pi label. As a speaker flat against a boundary can only radiate into a hemisphere, this is referred to as 2Pi positioning.—John Atkinson
Wilson Audio Specialties
2233 Mountain Vista Lane
Provo, UT 84606
(801) 377-2233

Bogolu Haranath's picture

With a minimum impedance load of 0.33 Ohms, we need an amp like the Relentless to drive them :-) .......

Ortofan's picture

... could have afforded the B&W 801 Matrix Series 2, the Infinity IRS Delta, the KEF R107, the Magnapan Tympani IVa or the Martin-Logan Monolith.






Bogolu Haranath's picture

You are gonna receive thousands of 'hate-mail' from Wilson customers :-) .......

Michael Fremer's picture

Why hate mail? Because Wilson's first speaker produced not such great measurements? That's silly.

volvic's picture

At the time I was blown away by the Concept 90 made by B&W. I heard so many other speakers at the time including the more expensive B&W's and Elipsons, but the Concept 90's where the ones I always wanted. I've been looking for a pair lately but most are pretty battered.

Ortofan's picture

... were you "blown away" - the CM1 mini-monitor alone, or the CM1 plus the CM2 sub-bass module?

Frank Van Alstine raved about the Concept 90 speakers when they were introduced in 1987.
You can read his comments by downloading his newsletters here:

volvic's picture

The complete package. Played an MSO record on an Oracle table with an Ortofon MC cartridge. Do not remember the electronics, maybe Bryston. It was magnificent, and if I could find a nice pair in like-new condition, I would retire my Kans to a secondary system. I just loved those speakers sonically and esthetically.

Bogolu Haranath's picture

Hi fi shark has some B&W Concept 90s for sale :-) .........

AJ's picture

Reading this review including physical reality measurements, it's clear Mr Colloms is truly a kind gentleman. Hope he's safe and well.

Soundfield Audio

John Atkinson's picture
AJ wrote:
Reading this review including physical reality measurements, it's clear Mr Colloms is truly a kind gentleman. Hope he's safe and well.

I stay in touch with Martin on Facebook and he's doing okay, AJ. Thanks for asking.

John Atkinson
Technical Editor, Stereophile

Michael Fremer's picture

Martin is and was honest. I don't read where kindness was involved.

AJ's picture

Good to hear. Take care too John, happy Easter, hope all are staying safe and staying in, listening to music.

Michael Fremer's picture

When I interviewed recording engineer Roy Halee (Simon and Garfunkel, The Byrds, Dylan etc.) back in the late 1980's he took me into his listening room where he had two systems set up. One was essentially Harry Pearson's system: Infinity IRS speakers, Jadis electronics and i think the same Goldmund turntable HP had. The other system in the room consisted of a pair of these WATT speakers and Mark Levinson electronics. Halee remarked looking at the WATT system "When I want to hear what's in the recording I use this, when I want to enjoy listening to music for pleasure i listen to those (the IRS system). Halee's recordings tell me there's no point arguing with him. Halee moved on to big Wilsons and stuck wilth various upgrades until a few years ago when he switched to Vandersteen 7s....which is what he now uses with Audio Research electronics and a Basis turntable. Yes, Roy prefers vinyl, but then what does he know? He should talk to some recording engineers..oh right! He is a legendary one!