Most of you know me primarily as a booster of panel speakers, electrostatics and ribbons in particular. So, too, you may know of my love for certain dynamic, ostensibly 'conventional' speakers such as the BBC LS3/5A, Sonus Faber Homages and Wilson's WATT Puppy combination. Indeed, it's easier to list my dislikes - horns, speakers that fire off the walls, etc - than to tell you my preferences. But what I'd drifted away from was a closet love for a speaker topology practiced by fewer and fewer manufacturers: transmission line systems.

We've all heard the same drill, that transmission line systems have one-note bass, although incredibly extended and with plenty of it relative to cabinet size. I never found it to be that way - one-note-y, that is - and I rue the missed opportunities when, due to lack of space and/or money, I passed up buying my personal faves - large IMFs in particular. Throw in a couple of Radford models, and here's a sub-genre awaiting rediscovery. But they were larger examples of the art. Quietly, PMC has been making a genuine transmission line speaker no bigger than an LS3/5A, and it's been upgraded to a level of performance so disproportionate to its price, let alone size, that I couldn't resist a go with them. My adventures ended up with one friend immediately deciding to buy a pair.

How they came to my attention is reason enough to review them: Peter Thomas of PMC worked for many years at the BBC, testing - yup, you guessed it - LS3/5As. So he was a bit puzzled by my failure to include the DB1+ in a recent round-up of wannabes. It fit the size and price profile, but, above all, it was conceived by a company with its roots in the BBC. Red faced am I, or what? My only excuse was that there are a few dozen contenders and our choice was random.

Now the DB1 has been upgraded to DB1+ status, and the metamorphosis is not merely a refinement. The DB1+ is a little monster, a deceptive mini that's able to punch way above its weight. The mods, also applied to the FB1 and TB2, include the use of the high performance 27mm fabric soft dome tweeter found in far more costly PMC passive monitor systems. This tweeter upgrade also inspired improvements to the crossover design, while the TB2 and FB1 also benefit from 're-engineering' of their acoustic damping.

According to PMC, these changes not only improve the acoustic characteristics of the monitors, for lower distortion, better-controlled vertical and off-axis dispersion, better stereo imagery and higher power-handling, they also strengthen the sonic family resemblance to the larger PMC systems. Thus, these more compact, affordable models exhibit 'similar high signal definition, consistent on/off axis dispersion, extended frequency response, and tonal consistency at all volume levels.' If you're wondering why this was desirable, think outside of the stereo box: the greater the sonic resemblance across the range, the easier it is for customers to create a mix-and-match line-up for home cinema packages from within a single catalogue.

There are no free lunches, so PMC made the incorporation of the dearer tweeter possible by increasing economies of scale in the manufacture of the less expensive models. The improvements to the crossover, to match the new tweeter, included lowering the crossover point to 2kHz from 3kHz, 'to provide true second order roll off,' and the use of hand-selected and matched components. Also added was a drive unit impedance compensation network to enhance driver integration and power handling. Frequency response is 50Hz-25kHz and sensitivity remains 87dB. Impedance is nominally 8 ohms, and the speakers proved remarkably easy to drive despite sensitivity considered a bit on the low side by today's standards.

So exciting was the initial burst that I couldn't resist trying the DB1+ with a ludicrously varied array of amplifiers, from £799 to £10k-plus. They included the PrimaLuna ProLogue One valve amp, the Muscial Fidelity NuVista integrated, the McIntosh C2200/MC2102 pre-power combination and the Ayre AX-7 integrated amplifier, representing a spread of 35-130W/ch, solid-state and tube. All cabling came from Transparent's Reference range, while sources included the Marantz CD12/DA12 and Musical Fidelity NuVista CD players, and the SME Series V tonearm/SME 30 Mk II turntable with Koetsu Urushi Black and London Reference cartridges.

Because PMC's Keith Tonge and Pete Thomas delivered the speakers in person, I was treated to a lazy set-up: they took care of optimising the pair, using the IF stands and setting them up as far apart as possible, beyond the outer edges of the WATT Puppy 7s, with severe toe-in. The resultant positioning - some 9ft apart, and far more spacing than I would have used - created no hole in the middle. Instead, and this was something every visitor remarked upon, the sound was simply huge, a wide, deep and tall soundstage more reminiscent of a 5ft tall MartinLogan than a small two-way speaker the size of a loaf of Hovis.

Their reproduction of scale was the overwhelming trait that provided the DB1+ with both its 'personality' and its main selling point. More than any speaker I've heard with similar dimensions and a price under £1000, the DB1+ does the most convincing hatchet job of all on the argument that big sound needs big speakers. Then again, we're talking about a 5ft transmission line folded into that wee cabinet.

Sheer size wouldn't be convincing without the mass to back it up, and the quantity of bass produced by the DB1+ added convincing bulk to the sound, even with material that upsets most small monitors. The new album of Dylan covers performed reggae style, Is It Rolling, Bob?, is filled with tracks boasting exaggerated lower registers that cause the LS3/5A to fluff and fart. The DB1+ handled them with aplomb, and it was only when turning to the Wilson WATT Puppy System 7 that one noticed the absence of the bottom-most frequencies. What's clear, however, is that PMC wanted to be able to play the DB1+ along side the LS3/5A and other killer mini-monitors and hammer them into submission.

They did so, too, with playback levels. Power handling is stated as up to 150W; I don't know quite how much power I fed them, but I yielded before the speakers did. The sheer room-filling capability of this speaker must be a direct result of PMC's primary market: heavy-handed professionals who don't expect things to break. If you need a mini that can go loud without sacrificing refinement, thank your lucky stars for the DB1+.

So far, so good. Here's a speaker than no BWFH could complain about regarding size or price, let alone notice, yet it acts as if it were the bastard mutant child of an LS3/5A and a Cerwin-Vega. It rocks like a studio monitor, but with the sort of finesse usually lacking in speakers designed for reliability under extreme conditions, rather than absolute sound quality in front of picky audiophiles. And its BBC pedigree is no more vividly revealed than through the midband, especially with voice.

It's abundantly clear that Thomas, though he's been non-BBC for over a decade, retains allegiance to old-school Beeb standards. Vocals are warm, natural and full-bodied, with plenty of detail to provide near-LS3/5A realism. What differs is a bushel of sparkle up at the top, just ornery enough to grab you by the shoulders, shake you and tell you why these speakers sound much better with tubes than transistors. At least, to my ears. Clearly, these are 'modern'-sounding if added snap and crisper transients are what distances us from the era of the Spendor BC1. Suffice it to say, every person who heard them was knocked out by both the pedigreed performance and sound that belies size.

Better still is the pricing. A pair of DB1+s will set you back only £625 in the standard finishes of maple, cherry or oak, with other veneers available at extra cost; the dedicated brackets sell for £50. (Current owners of the DB1 can purchase an upgrade kit, including the hand-selected and matched components, through PMC dealers for £198.) For this kind of performance, that's a nothing short of astounding. And if I had to do that wannabe round-up all over again, I think this would be the winner. While the return of the genuine LS3/5A remains in limbo, here's an LS3/5A substitute without the tears.