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I would distinguish between two separate levels of my personal assessment - the subjective quality of the analogue stage; and the perceived general benefits of digital room optimization. These in my mind are two independent features which impact the overall result. Of course I will also try to sum them and share my thoughts about the overall performance. Let’s start with the analog side of things. At first I experienced the ST2-HiFi between my D/A converter and power amps used as a digital volume controller. I then added my Wyred4Sound STP-SE preamp and SPL Volume controllers to adjust the volume in the analog domain. Next I experienced the Trinnov room optimizer in the digital domain (i.e. between digital transport and DAC). Finally I used the Trinnov’s internal D/A converter to compare it to my personal references. The output stage is not what I consider to be the strongest virtue of the ST2-HiFi. Be mindful though that my consideration does not take into account the Trinnov’s asked price per se. I simply compared its various functionalities (corrector, DAC, volume controller) to what I had on hand. Let’s begin then my stating affirmatively that the ST2-HiFi is worth its price even when considering its analog output stage. It’s simply the case that its truly exceptional optimization software can also be plugged into more expensive audio components where the noise floor and transparency of the Trinnov’s own output stage (very good for a € 6.000 tag) will not always be commensurate with such a system’s full potential.

A very simple test was comparing the digital bypass—disabling all of Trinnov’s active corrections and EQ—with the same digital signal coming directly from the transport to the D/A converter without passing through the Trinnov. Here I’m referring exclusively to subjective auditions without measurements since I had no opportunity to measure the noise floor of the ST2-HiFi. The manufacturer quotes 119dB S/N ratio for A/D conversion and 118dB for D/A conversion. Please note that this simple bypass test added one more digital cable to the comparison. This test always resulted in a qualitative loss when passing through the Trinnov. You might demur and ask what kind of device can prevail to be fully transparent and you’d have made a valid point. It simply means that adding the Trinnov to other components of a high-end playback chain will certainly alter the overall quality of sound before considering any subsequent kind of sound optimization. I got the best results from reducing the number of components in my own system; or by using the Trinnov in the ‘source-most’ position right after the digital transport. Obviously there was direct self interest to limiting the number of A/D and D/A conversions in the signal chain. My use of the ST2-HiFi in the digital domain led to very satisfying results but I also obtained good results using a digital input into the Trinnov Optimizer and outputting analog directly into my power amplifier (which I believe to be state of the art). These results in either case seemed linked to the reduction of conversion stages.

As it turned out, the quality of Trinnov’s internal DAC was more than satisfactory. Even though the French device is reasonably priced considering its extreme versatility, the D/A converter section stands comparison with most high-end competitors without consideration of price. As a DAC I consider the Trinnov a very valuable component that can be associated with first-class audio partners. In this capacity the Trinnov has no discernable sonic signature and is able to do its job without any particular requirement regarding association. If my Totaldac and Yamamoto YDA-01 have their own personalities, the Trinnov DAC is slightly more neutral - closer to the previously reviewed Audio GD Ref 5 but without its dark-leaning flavor.

After three months of use I arrived at the complete conviction that one must avail oneself of Trinnov’s full suite of functionalities. Room for improvement obviously exists. I would champion a higher-end version of the ST2 especially for its preamplifier function where I’d honestly prefer to remain in the analogue domain. This would require a more sophisticated output/volume-control stage but I’m cognizant of the pricing issue involved. In relation to current high-end pricing conventions Trinnov’s analogue performance calls for no criticism. I actually preferred using Trinnov’s attenuator over adding an external preamplifier for that control. What you might gain in theoretical accuracy should be lost in greater wiring complexity and added circuitry. Of course these considerations are completely divorced from the optimizer’s core functions. Let’s see now what kind of result I was able to achieve with a full Trinnov optimization in the amplitude and phase domains. The benefits were more than obvious. The differences between bypass and full optimization mode were night and day. I honestly think it would be impossible during a blind test not to identify the correction mode ten out of ten. You first enjoy increased details due to a more linear in-room speaker response; and a more correct tonal balance. The correction of my Triangle Magellan monitors’ response can be seen in the graphs below:

Manufacturer’s frequency response curve in anechoic environment.

The Triangle amplitude curve in my listening room as measured by the ST2-HiFi before and after optimization.

As you can see, the most comfortable seat in my listening room tends to worsen the Duetto’s midrange suckout between 2 and 6kHz. This problem could be partially addressed by passive room treatments and a complete reorganization of the living room. That would simply lead to a near-field listening position and turn the loudspeakers by 90° - not the most suitable solution for a living room. The Trinnov lets you know about the nonlinearity of each speaker’s response as shown in the upper graph especially for the bass. Here the ST2-HiFi lets you adjust the equalization for each channel separately. My main challenge was correcting room mode notches and the hollowness of the midrange. One could define full amplitude equalization by increasing the boost limit as defined in the optimizer’s settings window. But 4dB in my opinion remain the recommended maximum. Beyond this threshold signal boost might result in more unpleasant distorted artefacts. With the ST2-HiFi I achieved a welcome recovery of my midrange issue and a subsequent improvement of timbres.

I experimented with both single and multi-point calibration and definitely preferred the multi-measurement profile to the exclusive sweet-spot profile. In my case it allowed for further flexibility and delivered a more liquid and relaxing sound than single-point calibration. This of course was a personal finding which could easily change with room and listener. Yet the tonal balance improvements were not the sole beneficiary. Better dynamics and a more three-dimensional soundstage were further stunning gains. This translated into noticeably high resolution of stereophonic imagery with well-focused phantom sources. On symphonic music pieces the soundstage seemed definitely more accurate sporting greater identification of each instrument's position. Another stunner was the fact that it became quite impossible to locate the speakers in my room. The phase optimization really is an impressive feature of the Trinnov. As you will see next, I would undoubtedly have enjoyed better results still with the support of a professional Trinnov installer but this graph already gives you an idea about what kind of mess the Trinnov can set in order. Phase smoothing is particularly relevant above 200Hz and reduces most time anomalies (i.e. all of a signal’s frequency components otherwise delayed when passed through an amplifier or  loudspeaker).

The ST2 HiFi's overall performance was outstanding in terms of tone, timing and soundstaging. I can easily declare that the Trinnov added coherence and delivered the highest fidelity to my usual playback chain I've yet encountered. From my various experiments with configuration settings, I definitely think that the best performance from the ST2-HiFi is achieved by exploiting its full range of functionalities when inserted between digital source and power amp/s. Another salient feature was the stunning improvement in soundstage accuracy and detail amount regardless of volume setting. The Trinnov allowed me to listen at loud or low volumes without any particular prejudice regarding comfort, intelligibility or resolution.

It also was very interesting to compare two different bookshelf speakers. The slightly smaller Athom GT1 usually exhibits the same overall behaviour in the listening room as the Triangle but with an unexpected emphasis especially in the bass. The Trinnov correction rendered the sound more open and spacious with perhaps a discrete loss of low-bass impact but these are completely different speakers and not exactly of the same size. This was a reminder to observe the room's acoustic importance on the overall result in action and to recognize is as finally being more important than the choice of speakers itself. It also highlighted the appeal of room correction independent of speaker size.

With both pairs, the 2.1 configuration was very instructive. The ST2-HiFi is one of the most efficient tools to properly set up a 2.1 or 2.2 system thanks to its advanced bass management. In case you already own a pair of very efficient monitors or small-sized floorstanders, the acquisition of a Trinnov with two quality subwoofers can represent a true upgrade path to compete with very ambitious high-end floorstanders. Integrating one or two subwoofers into a high-fidelity chain is always a delicate operation. The subwoofer should blend so seamlessly that its presence becomes indistinguishable. It should never call attention to itself and bass should simply be more detailed, extended and powerful, the overall sound more open, transparent and articulate. This consistency of the bass range with the upper frequencies as a natural coherence is quite essential to long-term listening enjoyment. This subtle alchemy makes the perfect setting more difficult to achieve than it might seem at first glance. The ST2-HiFi let you dial in the perfect blend with your front speakers, offering you the choice to activate the low frequency effects channel or to specifically adjust the crossover. The option of adding a second subwoofer will help smooth the bass response throughout the room (especially if you set different path lengths instead of using direct digital equalization for signal boost).

Using the Athom Rafale subwoofer with the Magellan Duettos was a great listening pleasure with big orchestral works by Mahler or Bruckner. Depth of soundstage and precise focalisation of instruments were particularly impressive. I am not a proper subwoofer guy but here must formally credit their utility when driven from such a sophisticated device to precisely equalize their response. The Trinnov would obviously call for more ambitious subs than the Athom which was a very affordable but stereo-compatible choice I had on hand.

Subwoofer equalization.

CD used during the test. Lizz Wright, Dreaming wide awake – Verve Music 2005 / Arturo Sandoval, Tumbaito - Messidor 1987 / Roberta Gambarini, Easy to love – Groovin'High 2006 / Wiener Philharmoniker & Pierre Boulez, Bruckner Symphony N°8 – DG 1999 / Berliner Philharmoniker & Claudio Abbado, Mahler Symphony N°7 – DG 2002 / Keith Jarrett @ Charlie Haden, Jasmine – ECM 2010 / Chitose Okashiro, Tchaikovsky Symphony N°6 piano transcription – ProPiano 2000 / Los Angeles Philharmonic & Esa-Pekka Salonen, Le Sacre du printemps – DG 2006 / Dave Holland & Pepe Habichuela, Hands – Dare2 Records 2010 / Anner Bylsma & Tafelmusik, Boccherini Cello concertos sinfonias – Deutsche Harmonia Mundi 2009 / New-York Philharmonic & Leonard Bernstein, Mahler Symphony N°1 – Sony 1998 / Sarah Nemtanu, Gypsic – Naïve 2010 / Berliner Philharmoniker & Claudio Abbado, Maxim Vengerov, Tchaikovsky Violin Concerto – Teldec 1995.

Summing up, the Trinnov ST2-HiFi is a definite bargain given its price and astonishing versatility. It represents a broad range of features that will have you reconsider your overall playback chain. It also requires of the new owner to get directly involved in the various settings and options available; or to perhaps engage specific assistance from a local dealer or room acoustics professional. But in general it adopts an open-door policy due to its relative simplicity of use and friendly menus. With the ST2-HiFi digital room correction no longer is a private secretive matter for specialists. Even the fully automated corrections calculated by the optimizer algorithms are a great improvement over the uncorrected prior performance. The ST2-HiFi can unite home theatre and hifi expectations in one single system. The range of prospective users is thus rather larger than purist audiophiles. It represents a very efficient way to manage low frequencies and oversee the successful integration of subwoofers. The results achieved with coherence especially relative to timbre and timing are truly amazing. There is no particular lack of dynamics as is unfortunately often the case with less sophisticated room correctors. The current limit of 2.2 is due merely to the license and additional channels required over the standard version..

Obviously the Trinnov cannot completely overcome severe room modes where passive room treatments would remain an augmentation need for any audiophile looking for a kind of acoustic heaven. I would also call for further improvements with an increase of D/A converter resolution as is already the case for professional Trinnov versions. The noise floor could be further lowered and the volume control managed in the analogue domain with the addition of a manual control knob. Then the Trinnov could—admittedly to the detriment of its current retail price—become a kind of ultimate audio weapon, summing its current capabilities with the reinforced illusion of presence and the uppermost harmonics that count so much with many valve amplification aficionados. The greatest appeal of the Trinnov ST2 Hifi resides in exploiting its full range of capabilities, that is to say actually use it as a room correcting computer, D /A converter, preamp and active crossover all at the same time. In a fully integrated setup it achieves today far more than its price should have had me imagine. For this overall performance I have no alternative but to issue a Blue Moon Award.
Trinnov website