Product Review:
Whatmough P33 Loudspeakers
Product Type: Loudspeakers
Reviewed By: Greg Borrowman and tested by Steve Holding
Magazine: Australian Hi-Fi: September 2007
Distributor: Whatmough Pty Ltd
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 bi-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.
Performance
Despite the height of the P33 cabinets, the tweeters are a very ear-friendly 910mm above floor level when the speakers are standing on spikes. My initial ‘rough-in’ for siting the speakers in my listening room was so extraordinarily successful, with the speakers delivering such great bass and a superb stereo stage, that I was congratulating myself on my skill until further attempts at improving things even further proved beyond any shadow of a doubt that it was the speakers themselves that had permitted my instant success. My further experiments then simply confirmed that the P33s perform well across a very wide range of positioning options. It doesn’t matter whether you push them close against a wall or bring them out into the room; angle them in to face the listening position, or over-angle them, or simply place their backs parallel with the rear wall so they fire straight up the room, they’ll always sound great. Yes, there will be minor differences in all these positions, but the critical word here is ‘minor’: in every circumstance the P33s really delivered the musical goods, any small adjustments you decide to make will be for your personal preferences and to suit your room more exactly.
The thing that struck me immediately about the P33s was the strength of their presentation, with the sound surging into the room with a cohesion that linked the disparate drivers into a single musical whole. This feeling of musical strength extended beyond simply the overall balance from low bass to extreme treble to encompass the space between the speakers as well. I had no sense of the sounds of the left and right speakers combining to form a soundstage, just an image of the performers at the front of the room, as if there were no speakers at all.
When there was just a single performer, the illusion was so uncanny it was spooky. Listening to a new-found favourite of mine, John Couch, it was as if I’d invited him around to my place and asked him to bring his guitar. (I hasten to add that I don’t know him at all: it’s a metaphor.) I hadn’t heard of him at all before his new CD ‘Desdemona’s Song’ was brought to my attention. It’s available via www.indie-cds.com. Couch is a Kiwi currently living in Canberra, where this CD was recorded by Michael Grafton-Green at the Wesley Music Centre. The Whatmough P33s transferred the sense of acoustic space that’s been captured in the recording directly into my lounge-room, along with the guitar. I knew I was listening to something special immediately from the sound quality of first soft notes of Isaac Albeniz’s Asturias (Leyenda) Suite Espanola No 5, Op 47, but when I heard the sound of the first major fret board slip (24 seconds in) my head really snapped up, because it sounded so live. The superb tone of the P33s (and of Couch’s Philip/Smallman guitar) is rendered beautifully and rather gently in the following track, Jorge Cardoso’s Milonga. This CD closes with a track that’ll bring a tear to the eye of all ex-pat New Zealanders: it’s Couch’s arrangement of Princess Te Rangi Paire’s Hine e Hine, better known as Goodnight Kiwi, due to it being used to signal the midnight shut-down of NZ’s Channel 2 TV for nearly two decades. Fabulous CD on all three counts: its sound quality, Couch’s performance and the repertoire!
Needing something just a bit more meaty to test the bass regions and the extreme treble, I span up Tim Bruer’s rather unimaginatively titled debut CD (The Tim Bruer Quartet). I did so because previously listenings had revealed that Bruer’s music is far more imaginative than his album titles, though I have to say that it’s Sean Coffin’s work on tenor sax that I find most interesting on this CD. I didn’t have to go further than Brett Hirst’s long bass solo
on Like John to hear that the P33s could really deliver in the nether regions of low bass, seeming to go down and down effortlessly and without any loss of volume at all. The sparse sound of the quartet allowed the tweeter to strut its stuff thanks to Simon Barker’s high-hats, with the treble positioned exactly where it should be and not even a hint of being too ‘hot’ in the mix. I also couldn’t not mention the sound of Bruer’s piano which is full and warm. This, plus the fact that Bruer is in top form made me wonder why engineer Ross A’hern leaves it so distant in the mix at both Sony and Megaphon studios. The tracks recorded at the Q Studios bring it more to the fore, but only because everything else is pushed back. Still, it’s really only because the Whatmough P33s are so revealing that I was able to pick this so easily.
Vocals through the P33s are sublime. If you need to be reminded of one of the three-way speaker design’s major strengths, just put on a CD with vocals: male, female or child prodigy, and settle back. The crystal clarity and etched detail you’ll hear from the P33s will be their own object lesson. I played Joanna Loth’s interesting new CD Slow Secret Smile which has her singing all her own original tunes, including the title song. Her unforced, natural voice dominates against the sparse piano (Steve Newcomb) and double-bass (Georgia Weber) backing and the P33s let me follow—and thoroughly enjoy—every note, every subtle nuance, until the end of the CD came around all too soon (which it actually always does anyway, because at a shade over 20 minutes, it’s far too short, for all reasons…)
Conclusion
In the several months these were in my listening room, there wasn’t a single visitor who wasn’t knocked out by the sound issuing from the P33s, but I have to say that I was rather surprised at the range of comments about the design, particularly the most obvious element, which is that ‘cows lick’ on the top. I was surprised because although I prefer the graphite finish, rather than the Bubinga finish that was on my review pair, I think the speakers look fabulous—and that’s notwithstanding the fact that I am probably appreciating the technical reasons for the cabinet shape as well as the aesthetics—so I was really surprised to find such a divergence of opinion, sometimes quite strongly expressed! However, when it comes to sound quality, there was no divergence of opinion whatsoever. The sound is fabulous— everything you could want in a pair of loudspeakers, and when you consider not only the sound, but the parts that go into making up the whole, you’ll see that at an asking price of less than five grand, the P33s are a steal.
LAB REPORT
Readers interested in a full technical appraisal of the performance of the Whatmough Performance 33 Loudspeakers should continue on and read the LABORATORY REPORT published on the following pages. All readers should note that the results mentioned in the report, tabulated in performance charts and/ or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.
Test Results
The measured performance of the Whatmough P33 loudspeakers was excellent. Graph 1 shows the frequency response that results from feeding the Whatmough P33s a band limited pink noise signal, which requires the amplifier to simultaneously produce every frequency between 20Hz and 20kHz at the required level. It’s a far more diffi cult test than either the gated sine technique (LMS) or the impulse test (MLSSA, et al). In this graph, the ‘raw’ unsmoothed trace is shown, measured at 3.0 metres, with a 2.83V input (nominally one watt, assuming an 8Ω nominal impedance). You can see that it’s spectacularly fl at, particularly in the region spanning 250Hz to 8kHz. Below 250Hz there’s a slight ‘bump’ in the response before the roll-off to 20Hz, and above 8kHz, there’s a slow roll-off to 20kHz. However, overall, this raw response extends from 22Hz to 20kHz ±4dB.