Trenner & Friedl Sun loudspeaker

Roughly half the size of a breadbox—remember those?—the Trenner & Friedl Sun ($3450/pair) is arguably the smallest stand-mounted loudspeaker presently available for serious home listening: only 8.5" high by 6.25" wide by 5.5" deep and weighing just 7.5 lbs. The Sun is the entry-level model from this Austrian loudspeaker manufacturer, and its ported, solid-birch cabinet is designed and built to golden-ratio proportions (footnote 1) It has a single, coaxial driver from SEAS and a crossover made by Mundorf. The Sun boasts a frequency response of 55Hz–25kHz, +0/–3dB; friends of mine have heard the speaker plumb remarkable depths when paired with the right amplifier. And though they're barely bigger than a pair of Audeze LCD-4 planar-magnetic headphones, the Suns do play louder!

With their unusually small dimensions and not-small price, you're probably wondering how two such speakers can fill a room—heck, a bookcase—with real-world frequency range, organic tone, credible bass extension, and lifelike dynamics. I wondered that too, the moment my eyes spotted the Suns' lovely birch cabinets in Greenwich Village hi-fi emporium In Living Stereo.

At first glance, the Sun reminded me of the Auratone 5C Super-Sound-Cube: a similarly small speaker that, from the 1970s through the '80s, was seen in professional recording studios from Albany to Anaheim. (Such albums as the Bee Gees' Saturday Night Fever soundtrack and Michael Jackson's Thriller were mixed using Auratones—which, I should add, some recording engineers referred to as "horrortones.") Andreas Friedl designed the Trenner & Friedl Sun as a small monitor speaker to use in his own recording studio—but this isn't 1980, and his Sun is no tricked-out Auratone. For one thing, with its sensitivity of 82dB and impedance of 4 ohms, this mighty mite is a bear to drive. And though the Sun's visual appeal is subtle and its finish is silky to the touch, its Cardas single-action binding posts accept only spade-terminated speaker cables. Boo-hoo!

Loudspeakers with coaxial drive-units—the commonest examples of which have separate woofer and tweeter diaphragms, the latter positioned either at the front or rear of the former's pole-piece—seem to come back into fashion every decade or so. The 1940s saw the predominance of the Altec 604 driver. Tannoy's Dual Concentric design gained popularity in the 1950s. The Altec 604 rose again in UREI's 813 studio monitor of the 1980s. More recently, KEF introduced the UniQ; Cabasse came up with its four-way concentric QC-55 driver; and Andrew Jones got his mojo seriously working with the concentric driver of the Elac Uni-Fi UB5. I wanted to know: have Trenner & Friedl brought a new big bang to the coax party?


Trenner & Friedl's loudspeakers are hand-built in the mountainous, forested countryside of Styria, Austria, with final assembly near Styria's capital, Graz. Austria is home to some of the finest luthiers in the world; woodworking and music are in their blood. Peter Trenner and Andreas Friedl have designed and developed a line of seven speaker models—from the entry-level Sun to the mid-tier, floorstanding Pharaoh ($13,000/pair), to their top model, the Duke ($175,000/pair)—all made almost entirely of natural hardwoods.

"Wherever possible, we use natural materials," states T&F's website. "Thus, we damp our loudspeakers with sheep's wool. We long ago ceased the use of endangered tropical hardwood veneers in favor of locally grown hardwoods for our cabinets. The surrounds of many of our drivers are made of cloth, which is extremely durable."

Sheep's-wool damping? Cloth surrounds? I genuinely admire this small company's organic approach to crafting music-reproducing machines. Further wisdom from the T&F site: "All of this not only serves to protect our Mother Earth, but also has sound technical foundations: our ears are extremely sensitive to the resonances that occur in artificial materials."

Perhaps this explains why I always haul ass away from giant-robot (thanks, Herb Reichert!) loudspeakers sporting metalflake finishes, beryllium tweeters, and ceramic woofers. Like my women, my coffee, and my hairstyles, I like my loudspeakers au naturel. Same as it ever was.

The Sun's coaxial driver—the SEAS L12RE/XFC—consists of a 1" silk-dome tweeter set into a 4.7" black-anodized aluminum mid/woofer coupled to a ferrite magnet 3.5" (90mm) in diameter and weighing 3.3 lbs (1.5kg). In the Sun enclosure, this two-way coaxial unit is ported to the rear via four very small, cute funnels that look as if some worker bee drilled them clear to China.

The advantages of a coaxial driver? Bob Clarke of Profundo, T&F's US distributor, gave me a lesson in electromechanics: "The difficulty with coaxial systems is to design them with no colorations; to locate the tweeter in exactly the right position, in order to have the same temporal point of origin as the woofer (time alignment); to harmonize the drivers; and to achieve focus of the whole, including the cabinet. Then, the coaxial principle has clear advantages: Ideal, point-source design that is independent of listening angle; [consistent] impulse behavior to produce the same sonic character: homogeneity. This sounds more natural and one doesn't need to spend so much time worrying about listening/mounting height/angle etc."

Clarke explained that the Sun's cabinet is dimensioned according to the golden ratio of 1:1.618 . . . , which, he claimed, "creates a more rigid box, reduces internal standing waves, and spreads out more evenly the resonant frequencies of the panels of the box, so that none 'stick out' to cause a tonal imbalance." (footnote 2)

After Trenner & Friedl had researched the resonant qualities of various ecologically sensitive materials, they chose to build the Sun's cabinet walls of birch ply of varying densities, to further reduce standing waves.


Clarke describes the Sun's crossover, handmade in Germany by Mundorf, as "employing Linkwitz-Riley functions with a very steep and flat 4th-order acoustic roll-off curve." According to T&F's website, Mundorf uses "premium Mundorf capacitors . . . baked-lacquer, flat copper coils with extremely low skin-effect, [and] metal-film resistors for purest reproduction of high-frequencies."

Systems and Setup
I evaluated the Trenner & Friedl Sun in two different systems. In both, the Suns were marginally toed in.

The system in my larger, 12' by 13' room comprises a Kuzma Stogi turntable with Stabi tonearm, a MacBook computer with PS Audio NuWave DAC, Shindo Laboratory Allegro preamplifier and Haut-Brion power amp, and AudioQuest Castle Rock speaker cables. I placed the Suns 14½" from the front wall and 7' 6" from my listening chair.

In my second, more tightly packed room (11' by 12'), I listened in the nearfield using a Music Hall MMF-7.3 turntable and arm, a Heed Quasar phono stage and Heed Elixir integrated amplifier, and Auditorium 23 speaker cables. Here the Suns sat 6" from the front wall and 5' 7" from my chair, each speaker on four small squares of mahogany to control ringing, atop a 24"-high steel stand from Bowers & Wilkins.

I feared that banana plugs sliding up against speaker posts designed for spades would be less than optimal. Soon, I requested and received a loaner set of Cardas banana-to-spade adapters ($60/four) from Dan Muzquiz of Blackbird Audio, near San Diego, California ( The difference wasn't subtle. The adapters opened the Sun's top end to reveal perhaps its most consistent trait: absolute transparency to the source.

Footnote 1: Merriam-Webster's Collegiate Dictionary, 11th Edition defines golden section, aka golden ratio, as "a proportion (as one involving a line divided into two segments or the length and width of a rectangle and their sum) in which the ratio of the whole to the larger part is the same as the ratio of the larger part to the smaller."

Footnote 2: As the Golden Ratio is either 1.618 or its reciprocal, 0.618, as the ratio of the Sun's height to its width is 1.3125, that of its height to its depth 1.5, and that of the width to the depth, 1.1, Trenner & Friedl's use of the Golden Ratio in its promotional literature is both incorrect and misleading.—John Atkinson

Trenner & Friedl GmbH
US distributor: Profundo
2051 Gattis School Road, Suite 540/123
Round Rock, TX 78664
(510) 375-8651

fetuso's picture

When i saw the picture of these speakers I thought they were my Vandersteen VLR Wood bookshelf speakers. They look remarkably similar. The VLR'S also have coaxial drivers and are about 12 inches tall. Vandersteen also states in the manual that spades are required, but i have mine connected with bananas while i shop for new wire. I'm gonna look into those Cardas adapters. The VLR'S also have wood cabinets, but the face of the speakers are not wood. One other difference is the vlr have a sealed cabinet.

popluhv's picture

how these compare to Harbeth P3ESRs. I see one of these in my future!

Kal Rubinson's picture

This is a fascinating report and, between the subjective report and the bench measurements, I am motivated to hear them. The only piece of info I do not see is some objective measure of what the dynamic capabilities are. How can those little cones play loud enough (for me)?

IgAK's picture

There was also the RCA MI-11411 series "coaxial" driver in the 40's to mention another. (Actually "coincident" is more appropriate where coaxial actually may involve a bridge such auto speaker drivers often have.)

But as to the "Golden Ratio" it possible the internal dimensions conform more closely to that than the external ones? Those would be the ones that matter more.

RelaxWithPep's picture

These are very good looking speakers whose design has clearly been given a great deal of thought. I would be delighted to own them. I'm sure they produce excellent sound. However, the review doesn't seem to support the conclusion. "The finest stand mount speaker I've ever heard," with no qualifiers? Really? Not "at its price" or "for its size" or "for those listening in small spaces"? Could the reviewer comment on the differences between these and the KEF LS-50, another small, highly touted, bookshelf speaker with a coaxial design?

jmsent's picture

it's pretty easy to compare them. Leaving aside the subjective comments, the KEF certainly has more bass extension and somewhat higher sensitivity. I believe the cone area on the KEF is larger as well, which accounts for the bass response. I have heard the LS-50 more than once and I own a set of speakers based on the coaxial unit that is one size up from the one used in the T & F speaker. These coaxial drivers all have a unique coherence to their sound, which is reminiscent of what you get in a full range driver. Done right they're very smooth with no obvious handover between drivers. Their vertical and lateral responses are virtually identical and as you can see in John's dispersion graphs there are no major holes or peaks off axis. All of this points to a good sounding speaker. Where I see the problem is in dynamic ability and ultimate SPL capability, which has to limited by the small cone size. Also, at high levels you run into intermodulation problems because the cone acts as a waveguide for the tweeter's radiation. As the woofer cone moves, you then modulate the energy coming from the tweeter as well. I'd think these would be good candidates for a subwoofer, but getting a seamless match might not be that easy.

Anon2's picture

Thank you for this review and taking the time to review this product. I'm sure that its makers put thought and workmanship into the speaker under review.

I don't have the access to listen to as many products as the Stereophile staff. Forgive me for asking if $3,450 is a sum that we should spend on a speaker with 82dB sensitivity (requiring a new amplifier in many cases), and that weighs in comparably to speakers that cost less than $500 in many cases.

A major kit retailer sells a DIY product whose driver is probably the same as the one we see on this product. I'll let the curious investigate this product, and its cost.

Before we declare this product "the finest stand-mount ever," we might benefit from a few more reviews of similarly priced products that are available. For about $345 more per pair, and for a tank-like product weighing in at 16 lbs. more per unit, Stereophile could provide some more perspective, for all, by testing this recently released product:

And for some unique engineering and solid manufacturing, we are still awaiting the SP test for this product. It has just been enhanced with a passive radiator, it has good sensitivity, deep bass, its own waveguide technology, and has an impedance curve that can accommodate virtually any amplification. It's also about $600 less than the product we read about in this review. A European sound engineer called it "the best nearfield monitor he had ever used in his studio."

Let's have a few more tests, in some cases long overdue, before we make such sweeping declarations about a single product.

John Atkinson's picture
low2midhifi wrote:
Stereophile could provide some more perspective, for all, by testing this recently released product:

My review of the Aerial 5T will appear in our March 2017 issue. However, it won't include comparisons with the Trenner & Friedl Sun, as that speaker was returned to the distributor after the review.

John Atkinson
Editor, Stereophile

Anon2's picture

Fair enough. I know you guys can't test everything, and do a lot as things stand. I look forward to the 5T review, and your listening and test-bench results. I'd also enjoy, if circumstances permit, a test of the new Dynaudio Excite X18. I heard this product in a dealer open house, and was impressed, though I had to turn the volume knob up quite a ways on the Arcam FMJ A19 integrated to get a serviceable level of sound. Still, the sound was great. Any thoughts as to when the B&W 805 D3 might be making it's way towards a test? Keep up the good work.

John Atkinson's picture
low2midhifi wrote:
I'd also enjoy, if circumstances permit, a test of the new Dynaudio Excite X18.

Herb Reichert was going to to review the Excite X18 but decided instead to review the smallest in Dynaudio's new Contour series. That review is scheduled for our April issue.

low2midhifi wrote:
Any thoughts as to when the B&W 805 D3 might be making its way towards a test?

My review of the 805 D3 will be in March, the same issue as the Aerial 5T.

John Atkinson
Editor, Stereophile

JohnG's picture

Footnote 2: As the Golden Ratio is either 1.618 or its reciprocal, 0.618, as the ratio of the Sun's height to its width is 1.3125, that of its height to its depth 1.5, and that of the width to the depth, 1.1, Trenner & Friedl's use of the Golden Ratio in its promotional literature is both incorrect and misleading.—John Atkinson

Could it be that the interior dimensions of the enclosure match the golden-section proportions? After all, if there is some magical audio property to that ratio, it would presumably have its effect inside the box rather than outside.

John Atkinson's picture
JohnG wrote:
Could it be that the interior dimensions of the enclosure match the golden-section proportions?

Although I didn't dismantle the Sun speaker, I very much doubt it. That would mean some of the interior walls being inches thick.

John Atkinson
Editor, Stereophile

homebrew's picture

They may sound wonderful, but I fail to understand how a pair of $150 drivers and $75 for crossover parts and cabinets can add up to a $3500/pr. speakers.

HansRamon's picture

Could be interesting with a test of the large Trenner&Friedl Ra's, since it appears to be DeVores Orangotangs, which are Your's uncrowned king. (probably mine too..)

dronepunkFPV's picture

God this makes me laugh at all the disposable income.
If you people buying these are business owners you are not paying your employees enough.
Status seeking chumps.