Whatmough PERFORMANCE P33 Review

Review in Australian HiFi - 2007

Greg Borrowman and tested by Steve Holding

No-one could fail to be impressed by Whatmough’s P33s. They’re finished in a superb Bubinga real wood veneer (a piano metallic finish is also available) and stand 1.2 metres tall on a 260×430mm footprint. But more than that, they’re shaped more like pieces of modern sculpture than loudspeakers.

The Equipment

A true three-way loudspeaker, the P33 design calls for two 180mm diameter dual-layer fibreglass/Nomex cones to deliver the bass. These operate in tandem, to increase piston area, before crossing to a single 125mm midrange driver. Handling the high frequencies is a 35mm dual concentric tweeter with a waveguide centre plug. This type of tweeter is a relatively new design, and is sometimes called a ‘ring radiator’ to distinguish it from the ordinary ‘dome’ tweeter design. Ring radiator tweeters have far smoother frequency responses than ordinary dome tweeters, and extend high-frequency response beyond 30kHz. This would not be so unusual except that ring radiator tweeters can also handle far more power than conventional domes, so high frequencies don’t get attenuated after prolonged playing. Unlike the similar-looking tweeters on some other speakers, the P33 uses a genuine Vifa XT25—though one that’s modified to Whatmough’s own specification.

Although Whatmough rates the bass drivers as having a diameter of 170mm the all-important dimension is the effective piston area (SD), which is derived from measuring the diameter of the cone, and adding the width of the roll surround. (A distance often referred to as the Thiele/Small diameter, after Australian engineers Neville Thiele and Richard Small.) The P33 has a T/S diameter of 135mm, which gives an SD of 143cm². However, because the two drivers operate together, the SD for the system is twice this, or 286cm². This means that if Whatmough wanted to achieve the same SD using just a single driver, it would have to have a T/S diameter of 191mm, which would equate to an overall cone size of around 236mm, based on a similar frame size and roll surround.

The driver does not have a central dustcap. Instead, at its centre is an exposed, bullet- shaped, pole-piece, whose size indicates that the voice-coil is approximately 30mm in diameter. This so-called ‘exposed voice-coil’ design means that you should always operate the speakers with their fabric grilles in place, to prevent small particles of dust or grit from lodging between the voice-coil and the polepiece. The basket supporting the cone is very large, and made from cast alloy. This means that it’s very rigid, and also can’t act as a ‘path’ to weaken the magnetic field from the magnet. In the case of the P33, this wouldn’t be likely in any case, because the magnet’s field is constrained by a second magnet attached to the rear of the main drive magnet.

The midrange driver also sports a heavy-duty cast alloy chassis that supports a large, vented, unshielded magnet. This driver has a cone that appeared to me to be made from coated paper. Unlike the bass driver, it has a conventional dustcap, but it, too, has a rubber roll surround.

As with all Australian-made Whatmough designs, the internal wires (which are solid five nines copper) are silver-soldered to the driver terminals, rather than connected with spade/lug connections, which can deteriorate over time, as well as to the crossover network. The network is all hard-wired using audiophile-grade components, including hand-wound, air-cored inductors (all crossmounted to eliminate magnetic coupling effects), 250Vd.c. Solen and Bennic capacitors and ceramic resistors.

The P33 is a bass-reflex design, using a front-firing port. The port is quite short (120mm) with an 80mm diameter. The tube is radiused at both ends and has ‘dual-coat’ interior, where half of the port is very smooth, whereas the other half is quite rough. If you were wondering about the size of the port, it comes about because within the P33 is a separate sub-enclosure that houses the midrange driver and the tweeter. This allows Whatmough to optimise the rear-loading for the midrange driver, and also means the rear radiation from the midrange cannot interfere with that of the bass drivers (or vice versa). The rear of the tweeter is, of course, completely sealed.

The P33 is also available in ‘Signature’ version. According to designer Colin Whatmough, the Signature version of the P33 replaces the Solen and Bennic polypropylene capacitors with Hovland film and foil capacitors in critical positions. Hovland’s capacitors typically cost 10 times as much as the equivalent Solen capacitors and even more for Bennic. The Signature version also replaces the solid internal cables with Litz cables made by Cardas in the US. Whatmough says that he uses the Litz cable even though it’s very tedious to wire up, due to every single strand being individually insulated, because ‘the sonic results of Cardas cables are stunning.’ Cardas also gets a foot in when it comes to speaker terminals, with the P33 Signature version benefiting from Cardas’ ‘rhodium over silver’ solid copper binding posts. Unusually, the P33s are intended to be tri-wired, and Whatmough is so adamant that they should be so wired that the usual bridging links are not supplied, so as to encourage users to at least bi-wire. According to the Whatmough’s website: ‘To obtain their optimum performance, [the P33s] should be trii-wired.

This involves using a tri-wireable (six-core) cable or three sets of normal two-core speaker cables. These cables can be connected to one or two sets of speaker terminals at the amplifier. One pair of cables is connected to the speaker’s top (tweeter) terminals, one to the middle (midrange and the other to the bottom (bass) terminals… If tri-wiring is not being used, (hopefully only a temporary measure) a link should be made from the same type of speaker cable that is being used to connect the speakers to the amplifier. Using this cable, the three positive terminals (red) should be connected together and the three negative terminals (black) should be connected together.’

However the most obvious (visual and audible) difference between the standard P33 and the Signature version is that the Signature uses the same ultra-expensive tweeter as Whatmough’s flagship speaker, the Paragon, which extends the response ultra-fl at to beyond 40kHz.

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Whatmough PERFORMANCE P33 Review