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PMC TB2S AII

Active Nearfield Monitors
Published July 2010
By Hugh Robjohns

PMC broke new ground a decade ago with their TB2 monitors, but the competition have been catching up. Does PMC's new 'activated' design nudge them back to the front of the pack?

PMC TB2S AII

I first reviewed PMC's TB2 passive nearfield monitors way back in SOS November 2001. The TB in the name stands for 'tiny box' (which it is when compared to the company's gargantuan 'big box' BB5 system!), and the '2' signifies that it superseded the original TB1. The improvements that warranted the name change were small but significant, affecting not only the internal 'Advanced Transmission Line' dimensions and the crossover, but also several largely cosmetic differences, such as a smaller removable cloth grille on the baffle, larger PMC badges and radiused baffle edges — although it should be said that the radiused baffle edges made an appreciable improvement to the already very good stereo imaging.

I revisited the TB2 once again in May 2005, when the self‑powered TB2SA version was launched. The 'A' indicated that this was an 'activated' or self‑powered speaker, providing exactly the same convenience as the fully active monitor speakers that dominate the market at this price level — but PMC argued that their 'activated' approach delivered better performance than was achievable from its competition. The argument centres on the claim that it is better to use one good-quality amplifier coupled with a well-designed passive crossover than two cheaper, potentially less good amps and an active crossover, and there is certainly some validity to that claim.

That 2005 TB2SA model not only incorporated a compact Flying Mole DAD M100pro amplifier module to 'activate' it, but also benefited from a revised tweeter and crossover. The economies of scale afforded by PMC's growing market share allowed the company to replace the original Vifa metal‑dome tweeter with the same soft‑dome model that they were using on many of the larger and more expensive monitors. This was a very worthwhile change, signified by adding a '+' suffix to the passive versions of the speaker.

The Flying Mole amplifier module employed in the TB2SA, a Class‑D design, delivered astonishingly good performance for such a small and lightweight unit, driving the speaker with a nominal 100W of power. Unlike a good number of class‑D amps, the DAD M100pro actually stood serious listening comparison with conventional class AB amps very well indeed. I auditioned it against Bryston Power Pac 120 monobloc amplifiers and was surprised at how well it compared.

TB2S AII

The new PMC‑designed amplifier packs, which are also available separately, add quite some bulk to the rear of the TB2S AII speakers.The new PMC‑designed amplifier packs, which are also available separately, add quite some bulk to the rear of the TB2S AII speakers.

So why the new model with an 'AII' suffix? Well, unfortunately the Flying Mole company was taken over last year and ceased production of the DAD M100 modules — which left PMC with a bit of a problem! After looking around for alternative amps that could be integrated into the cabinet — and finding nothing of adequate quality — PMC decided the solution was to manufacture their own power modules for the TB2SA and DB1SA speakers. The result is the PMC DS001, a unit with an identical form‑factor to the old DAD M100pro (a diminutive 130 x 215 x 41mm), but boasting twice the power output (200W), and a useful step up in sonic performance.

The new amplifier module is a class‑D design again, with a claimed 92 percent power efficiency, although this model does run significantly hotter than the Flying Mole model — so you won't want to leave your hand on the top plate for more than a few seconds when it's being driven hard, unless perhaps you're planning a bank job and need to lose your fingerprints!

The physical arrangement of the amp is virtually identical to the Flying Mole units: the audio input is connected at the bottom via a balanced XLR, and the output to the speaker is via a Neutrik NL4 Speakon, the cable disappearing into the speaker's internal passive crossover through the rear ATL vent's foam. The mains on‑off switch is in the top panel, along with a volume control that spans a gain range of 16dB to 33dB.

In addition to the change of power‑amp module, PMC's owner and designer, Pete Thomas, has taken the opportunity to revisit the design, and has had a bit of a fiddle with the crossover too, managing to improve the performance slightly. The tweaks have resulted in a slightly more complex passive crossover circuit, with the addition of a few more — inevitably expensive — components, but I think the benefits justify the expense.

The new TB2S AII retains the same Vifa soft‑dome tweeter as used in the previous '+' variants of the TB2, mainly because the same tweeter is employed in all the smaller professional PMC speakers. However, the crossover has been re‑voiced to bring the mid‑range slightly more forward. It's a fairly subtle change, but it makes the TB2S AII sit more comfortably alongside the larger PMC professional monitors in 'mix and match' surround‑sound systems. It has also resulted in a slightly flatter off‑axis response in the vertical plane when compared with the previous version, and the vertical listening axis has been tilted down a little, so that the listening window is even wider in a typical studio setting than with the old version.

The benefit is that the balance of the speaker is maintained even when listening on an axis below the bass unit — something that PMC found to be surprisingly common amongst typical TB2SA installations, apparently. The crossover revisions also attenuate the output of the woofer more accurately through the crossover region, giving better body to voices and reducing coloration even further. If you're looking at the PMC web site, though, it is worth noting that the passive domestic hi‑fi version of this speaker (the TB2i) uses a Seas Solonex tweeter, albeit with near‑identical voicing.

These revisions are all relatively small and subtle tweaks, and ones which will probably go largely unnoticed by the majority of users, but they demonstrate the ongoing development and continuing attention to detail that is a hallmark of PMC's standing as one of the top‑flight professional monitor loudspeaker manufacturers, and hint at the fierce competition in this market sector. There's no room for complacency!

Listening

I set up the new TB2S AII speakers alongside my old TB2 units (actually, TB2+ drivers and crossover in an original but modified TB1 cabinet), and fed them via a remote A‑B switch box to route my listening source to either system at the flick of a switch. My initial listening impression was as I anticipated: there was a distinctly tight, dry, and anaemic bass response. This is completely normal for a new PMC speaker and is because of the way the bespoke bass drivers are built and are loaded by the ATL cabinet design. They take a while to 'loosen up' when new, and although the review models were 'run in' for several hours before they came to me, they still needed a good couple of days' use before they really opened up at the bottom end to match my well‑used TB2s.

My own TB2s are powered with Bryston Power Pac 120 amplifiers, which are rated very conservatively at 120W into 8Ω. On paper, this should compare well with the old 100W Flying Mole amplifier, but in practice the Bryston easily out-performs it when the going gets tough, so I started my review listening by wiring up a pair of standard Flying Mole amps to my old TB2s instead. At normal nearfield listening levels, the old Flying Moles deliver an impressive performance, and with that baseline established for comparison I switched to the new TB2S AII and the DS001 amps. The difference in a straight comparison is immediately obvious, with a subtly different tonality. The upper-mid range is, indeed, a little more forward, improving usefully on the politely recessed character it had before, presenting mix details a little more firmly — but isn't in any way fatiguing or hard edged, just very well judged and a little more accurate and revealing than before. The lower‑mid frequencies are also slightly different, bringing an improved clarity to this critical frequency region.

Doing the 'sit‑stand' test, moving vertically in front of the speaker as you often do when moving up and down a large mixing console, the integration between the drivers through the crossover region remains as good as before, with a well‑controlled, even sound and negligible phasiness. The sweet spot for good imaging also remains very broad but, as usual, the speakers don't need to be pointed directly at the listening position. The best tonal balance is still achieved when their axes are aimed to cross a few feet behind the nominal listening position. I also found that they're not fussy about being tilted vertically to aim the tweeter at ear height: the balance remains good even if the speakers are pointing out horizontally a little above the main listening plane (something I proved by standing the new speakers temporarily on top of my old ones!).

The biggest improvement, though, is the better control, resolution and generous power reserves of the new amplifier module. I think it's fair to say that the DS001 easily outperforms the Flying Mole amps it replaces, and it's much closer to matching the sonic performance of the Bryston Power Pac 120s at all but silly levels. That's impressive: here in the UK, the Bryston PP120 retails for more than two-and-a-half times the price of the DS001 in stand‑alone form.

Verdict

I've long been a fan of the TB2 and its insanely accomplished little brother, the DB1. They are reliable, workhorse, nearfield monitors that deliver good-quality, accurate and neutral sound that doesn't fatigue the listener, doesn't vary with listening level, and does provide informative bass far beyond what might be expected for the cabinet size. But the TB2 has always needed a powerful amplifier to extract the performance it is capable of, and good though the Flying Moles were, they didn't quite enable the speaker to equal the performance that was possible with the might of a hefty Bryston behind it. The new DS001 amplifiers have raised the performance level much closer to the speaker's true capabilities, and the crossover tweaks have added some fine polish to an already exemplary showing.

However, the monitor world has moved on since the TB2 was first introduced, nearly a decade ago. Although the speaker set a very high benchmark when it was launched — and its subsequent tweeter replacement, crossover tweaks and especially the new amplifier have kept it towards the forefront — several other manufacturers have developed a range of very competitive products in the intervening time. Of particular note are the PMC‑designed Digidesign RM2 monitors, which are fully active speakers, and the astonishing new flagship speaker from Event, the Opal (reviewed in SOS August 2009). And my favourite compact monitor, the three‑way K+H O300, is only slightly more expensive.

So the TB2S AII faces some very tough competition... but when reviewing the original TB2S A, I said it was hard to find fault with the combination in any way at all, and I stand by that — except that the new version is even better, and it still delivers a remarkable bass extension with tight control, allied to a tonal balance that remains consistent and neutral, and with stable three‑dimensional stereo imaging and excellent resolution for a compact two‑way speaker at this price. An audition is thoroughly recommended, but please do make sure they've been properly run‑in beforehand, and aren't being tested straight out of the box!  

Alternatives

There are a lot of excellent compact monitors available for a similar cost to the PMC TB2S AIIs. ATC's smallest active speaker, the SCM16A, the PMC‑designed fully‑active and DSP‑controlled Digidesign RM2 and the remarkable Event Opal monitor are all priced almost identically to the TB2. The Adam S2.5A, the company's largest two‑way model, is only slightly more expensive, while the Adam S2X is a little cheaper, and the same applies to the Dynaudio M1.5 and M1, and the Genelec 8050A and 8250A, each pair spanning the TB2S AII's price point by a couple of hundred pounds in each direction. Geithain's RL906 is also slightly less expensive, while the three‑way Klein + Hummel 0300 is a little more expensive.

Published July 2010

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