Optimus PRO LX5 Loudspeaker

Not once but twice this year the Tandy Corporation has begged from us the question, “What’s going on at Radio Shack?” First, they wow us with a pocket-money CD portable which has the audiophile community in a dither. We sat back, assured that it was a fluke. Not. Now the chain-store giant has released the Optimus PRO LX5 loudspeaker and it’s going to cause another mad rush when people find out just what it is: a Linæum in cheap clothing. Like $300 per pair! And the nearest Linæum equivalent costs double.

Linæum’s claim to fame is a radical tweeter which (we can now say with hindsight) was just begging to be sold under license. And it came to pass that Tandy fitted this brilliant high-frequency unit to a speaker of its own. The Linæum tweeter, unlike a cone or dome, rests on the top surface of the speaker rather than in the baffle. And it radiates in such a way that it begs to be used in home cinema systems where a wide sound spread is so crucial.

It looks more like a home-made transformer surrounded by a couple of loops of cellophane than a tweeter. These “cellophane loops” are Mylar strips which turn out to be the actual diaphragms. Viewed from the top, it reveals itself to be made of centrally-positioned magnets linked by a suspension, beneath an upside-down-U-shaped metal frame. The Mylar sheets are attached to the outer edges of the frame and curve back to meet at the coil between the magnets, thus forming a pair of “cylinders”. The coil is suspended within a balanced magnetic gap under the center of the frame. Signal flows into the coil, interacting with the fields of the magnet assembly, causing coil movement to provide the wave motion through the diaphragm. It’s simple, compact, and effective. Best news of all: it’s able to cover the frequency range from 2kHz to better than 30kHz.

Tandy has matched the Linæum tweeter to a high-compliance 4in bass unit operating from around 90Hz up to 2.5kHz, all housed in a neat 9x6x6in fronmt-ported metal enclosure fitted with gold-plated, multi-way speaker terminals. It’s cute, high-techy in its matt-grey finish yet all-but-indistinguishable from the myriad nonsensical boom-box add-ons which also wear Mighty Morphin’ Power Rangers clothing. Until you switch it on.

With a dispersion pattern that seems to be nearly all horizontal, the sound radiating in a dipole manner, you can anticipate the need for a reasonable amount of breathing space. As Linæum suggests with its own, similar mini-speaker, ideal positioning calls for 24in stands, three feet from all walls and around 6-7ft in between the speakers. I preferred them with slight toe-in, which creates a “hot seat”, but not so bad as to be deemed anti-social. In the interests of testing for universality, I also tried the PRO LX5s on bookshelves and the damage to the sound was less than I feared. The expected bass reinforcement added weight, but the loss of airiness and three-dimensionality confirms the superiority of stand mounting out in the open.

Tandy doesn’t cite the speaker’s sensitivity, but 50W RMS is the recommended maximum amplifier power rating and an 8 ohm impedance means easy amplifier matching. Which is not to suggest that weedy little A/V receivers will do the trick. I worked the PRO LX5 with some top-flight amplifiers of triple-figure power ratings to learn that this speaker will reveal an amplifier’s shortcomings. Whatever your choice of amplifier make certain that it has lots of clean wattage. Even though horrid little dirt-cheap amplifiers will drive the PRO LX5, it deserves much better.

It’s because Linæum’s tweeter is incredibly revealing even though it’s sweet and smooth. The driver is unforgiving of amplifier clipping but tolerant of hard-edged sources like brighter CD players and most laserdisc and video-tape audio output. It didn’t emphasise the more negative aspects of CD playback, nor did it roll off the sound to eliminate nasties. In effect, the PRO LX5 acts like a serious, full-range product which just happens to be an octave or two short of realism. Which means that this speaker demands to be used with a subwoofer in A/V applications.

At $300 per pair, this speaker is a giveaway: fast, crisp, articulate and musical. Indeed, it’s so inexpensive that you could make a terrific Pro-Logic surround-sound system with three pairs plus any sensible subwoofer, using three PRO LX5s across the front, two at the back and keeping one as a spare. And so surface-covering is the dispersion that I’ll bet a pair at the sides in pseudo-THX manner will work like a dream. And I say that at the risk of incurring the wrath of THX acolyte-nerds.

Whatever way you slice it, the Optimus PRO LX5 is a ridiculously generous bargain. Less refined overall than its dearer Linæum equivalent, true, but still a giveaway.

What is going on at Radio Shack?

(Sound & Image, 1996)