Trenner & Friedl Osiris loudspeaker

Austrian loudspeaker manufacturer Trenner & Friedl has a thing for coaxial drivers. They’re used in at least three of the company’s eight loudspeaker models, including the diminutive Sun bookshelf speaker and the large floorstanding Taliesin. In these models, T&F eschew more conventional stacked drivers for a putatively time-aligned, wide-frequency range coaxial design.

I first encountered T&F’s approach when I reviewed the above-mentioned Sun, which proved to be the best small loudspeaker experience I’ve ever had. And I do mean small, as in 8.25″ high by 6.25″ wide by 5.5″ deep and weighing a scant 7lb. The Sun did tone, soundstaging, image weight, and dynamics so well for its size that I felt compelled to review the No.3 speaker in Trenner & Friedl’s lineup, the floorstanding Osiris ($8500/pair).

T&F likes to name its speakers after Egyptian deities, including Osiris but also Ra, Isis, and (generically, or maybe not—see below) Pharoah. As explained to me via email by Bob Clarke of Profundo, which distributes T&F products in the US, company co-founder and principal designer Andreas Friedl also identifies his speakers with jazz musicians—hence, “Pharoah” is also, very likely, a reference to Pharoah Sanders (note the spelling), “Ra” to Sun Ra.

Regardless, all Trenner & Friedl loudspeakers share such characteristics as cabinets built with multiple birch panels of varying thicknesses, multilayered lacquer finishes, oil-lacquered cones, crossovers built with Mundorf capacitors, locally sourced damping materials, and Cardas Audio cabling and binding posts.


The Osiris’s eye-catching 10-degree rearward slope gives it a windswept look recalling to my crusty memory the “blown away guy” from Maxell’s print and television advertisements of the 1980s. The Osiris’s proportions—it measures 33.5″ high by 14.25″ wide by 14.56″ deep—reveal it for what it is: a small floorstander that should fit well in most living rooms.

On their website, T&F claims that proportions are determined by the Golden Ratio, that irrational number with mathematical, architectural, and mystical significance; designing a loudspeaker cabinet with “golden ratio” dimensions can avoid overlapping internal resonances. But when I asked Friedl how he arrived at the Osiris’s particular dimensions, he responded with an email, writing, “the dimensions are chosen to fit perfect to the woofer [that the] Osiris should be a kind of egglaying, milkbearing woolly sow.” To my immense relief, Clarke later explained that this is a German-based idiomatic expression for “something that can do many things, similar to jack-of-all-trades, Swiss Army knife, etc.”

“The key to a cabinet design like this,” Clarke elaborated, “is always going to be finding the correct size/shape and loading scheme, here, a hybrid horn-port, to support optimal bass performance of the particular woofer being implemented, as well as HF extension, to project an image and soundstage, even while placed near the wall.” The Golden Ratio thing is just a guideline, not a hard-and-fast rule.

Clarke explained that the sloped-back design of the Osiris was partially a cosmetic choice to diversify T&F’s heretofore boxy-looking loudspeaker line, but the design is also functional. “The more irregular internal shapes of the Osiris cabinet help to reduce internal standing waves,” Clarke wrote in an email. “Also, sloped speaker fronts create shifting radiation angles of the drivers relative to the room and listener. If the radiation pattern is angled, it will help to reduce standing waves as the frequency moves upward and becomes more directional. It also puts the listener a bit off-axis in the tweeter radiation pattern, which tends to be less directional in this area, so there’s less of a head-in-a-vise ‘sweet spot.'”

Two black-painted wooden rails, each measuring 14.25″ long by 1.125″ wide by 3″ high, attach to the bottom of the Osiris, forming its base. This creates a small (approximately 1″) space between the floor and the bottom of the cabinet, which is entirely open, exposing a separate V-shaped wooden internal “port” attached within the lower portion of the cabinet. The “V-port”—my phrase—measures 6″ wide at its base and 14” high, fanning out at the top of the V to cover almost the entire width of the cabinet.

“The port is a hybrid between a classic bass reflex design and a horn,” Friedl explained. “We use the floor as part of the system, so the alignment is not so dependent on the room. It’s a very efficient solution. But much smaller than a real horn construction.”


Barely visible around the cabinet’s port when viewing the speaker from below, an inner chamber behind the woofer is damped with a material that, according to Clarke, is made from a composite of recycled fibers and a long-staple local sheep’s wool. Clarke added, “The horn/port construction constitutes its own considerable internal bracing, which also is internally angled to both create the horn/port and also to reduce any particular resonant frequencies, as the frequency of any resonance will change along the angled path of the brace-horn/port.”

The Osiris’s circular front grille can be removed by loosening two Allen screws on the rear of the cabinet, opposite the grille. Just as I was ready to do that myself, Clarke emailed photos of the 6.5″ coaxial woofer/tweeter assembly, clearly showing its 1″ compression tweeter, loaded by a hard plastic horn set within the woofer’s paper cone; the horn protrudes approximately 0.25″ and obscures much of the cone.

Manufactured by an unidentified pro-audio company, the Osiris’s coaxial driver has a basket made of die-cast aluminum. The woofer cone is suspended via a rubber surround, and the driver has a 120mm ferrite magnet, while the compression tweeter is backed by a 110mm ferrite magnet. “Baked-in-lacquer, flat-copper Mundorf voice-coils” reportedly resist internal vibrations, Clarke wrote. The woofer’s paper cone is coated with seven layers of Italian violin varnish to “optimize elasticity, damping and stiffness, and reduce cone resonances and distortion,” Friedl said.

“Manufacturers have doped their paper cones with various materials, but none have used violin lacquer, which stiffens the cone overall, without making it completely rigid, which could introduce non-linearities. Many of the doped cones in the past were treated to simply damp nonlinearities (resonances), while [our] treatment makes the paper cone stiffer and improves bass without creating ringing problems in the upper frequencies.”

Trenner & Friedl claims a nominal impedance of 8 ohms for the Osiris. “In the bass region,” Clarke wrote, “where resonance points often bring about a big dip, the impedance never drops below 6 ohms. There is also a slight dip above 10–15k, due to a bypass in order to deliver superhigh frequencies unfiltered, which allows for an increase in precision and clarity. Between 20Hz–20kHz, impedance does not dip below 6 ohms.”

The Osirises were the most finicky pair of loudspeakers to set up that I’ve ever reviewed. They required extensive break-in time to shed a dull sound and to gain warmth and extension in the bass. At first they sounded closed-in and listless. I played them 24/7 for two months via a $149 Sony STR-DH190 receiver transmitting Jersey City, New Jersey’s excellent radio station WFMU.

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Trenner & Friedl Graz Trenner & Friedl GmbH

US distributor: Profundo

2051 Gattis School Road, Suite 540/123

Round Rock, TX 78664

(510) 375-8651



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