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Description and main features:
Compared to previous pro versions, the ST2 chassis and electronics have been redesigned inside and out. The front panel is sleek brushed aluminium while the rear panel is specifically geared toward home audio use. Inside a new Trinnov digital audio engine combines with Trinnov's new generation of AD/DA converters designed to meet the requirements of demanding audiophiles. The ST2-HiFi is powered by the same software that has established Trinnov's reputation as one of the best-in-class loudspeaker optimizers for music and film studios around the world. The embedded software is extremely easy to use and offers unique room EQ features such as multi-point measurements, target curves and automatic phase optimization.

The Trinnov processor provides all basic functionalities one expects from a digital audio processor such as routing and level settings of various inputs  and outputs, word clock i/o, remote control options via Ethernet, presets save, backup and restore, basic peak level metering, calibrated global gain adjustments and so on. The ST2 offers direct manual equalization in addition to the main Optimizer functionality. It offers a comprehensive tool kit to fine-tune the results of automated correction. This post tweaking is usually accomplished with further separate acoustic measurement tools to improve over the results achieved via automatic correction. I did not use such advanced post calibration measurements during my assessment and my laudatory conclusion as to this unit’s capabilities should thus be considered very conservative as it does not take into account the more advanced capabilities of this French room optimizer.

The Trinnov has two main options for manual equalization:
  • a sophisticated FIR EQ based on finite impulse response filters that allows accurate equalization without introducing additional phase problems
  • a 1/3rd octave EQ with 31-band graphic equalizers
For large multi-way speaker systems with active crossovers, Trinnov's intelligent crossover alignment dramatically reduces the effort required to set up gain and delay for each driver. While a 2-way system can be managed with a single ST2, 3-way and 4-way systems can be accommodated by combining two ST2s. Let’s now inspect the optimizer module’s main features. Based on its acoustic measurements, the optimizer automatically aligns the relative output levels of each speaker drive unit and where necessary applies delays to time-align the system. This setting can be adjusted separately for the front and optional surround speakers in the settings panel. It uses state-of-the-art time frequency algorithms to analyze the calibration measurements and distinguishes between/compensate for direct sound, first reflections, reverberation and room modes. The optimizer adjusts the loudspeakers’ frequency response for both amplitude and phase to achieve tonal balance corrections with correct time domain functions to deliver a high-resolution stereophonic landscape with well-focused phantom images. The target curves define the filters which will achieve the desired frequency response as input by the target curve the user selected. Phase and group delay may also be defined separately. Other fine-tuning options are available to customize the room correction algorithms.

Another interesting functionality is the loudspeaker positioning remapping where the measurements are rematrixed and applied to the input signal to generate the same acoustic field that would be achieved if the speakers could be positioned correctly. The ST2 HiFi’s software running this math is the Optimizer Bundle 4 (4-channel licence for Optimizer Runtime and Toolbox). From a pure hardware angle the ST2 Hifi is equipped with new audio boards. The Trinnov audio core is the central component of the processor. It provides routing of audio workflow between physical i/o ports and software, activation of relays when user instructed to safely shut down, hardware source selection and clocking up to 192kHz. The Trinnov ADA4 module interfaces with the audio Core, produces AD/DA conversions and oversees 4 analog inputs/outputs. The Trinnov AES4 connects likewise to the audio core and manages up to 4 digital i/o ports. On the rear panel up to 4 channels can be configured as follows:
  • 4 channels with balanced analog inputs/outputs on XLR
  • 4 channels with single-ended analog inputs/outputs on RCA
  • 2 channels with digital AES inputs/outputs on XLR
  • 2 channels with S/PDIF inputs/outputs on RCA.
The ST2-HiFi claims very decent audio specs with a S/N ratio of 119dB (A-weighted) for A/D conversion and one dB less (118dB) in D/A mode. Jitter attenuation is said to be better than 50dB above 100Hz. The optimizer itself is a potent multi-core PC based on an Intel multithread 64-bit floating point CPU. The ST2 processors are very silent despite the use of two fans. They operate in flash disk mode to avoid mechanical hard drives and ensure mechanical robustness. The size of the ST2 HiFi of 169 x 427 x 410mm HxWxD will require a standard shelf and the big slow fan will not want another component directly beneath the Trinnov.

Getting started – calibration process.
The Trinnov needs to be connected to an external monitor screen with keyboard and mouse for the first time. It will retrieve necessary information (IP address and password) to complete a network setup if you desire control directly from your computer or from a remote device like a smartphone or tablet through a VNC client software. I personally chose to install the Chicken of the VNC freeware on my iMac. I did not succeed however in using my iPad to control the Trinnov due to my poor grasp of IT connections. I only experienced the remote control of my iMac from the iPad app Mocha VNC but it was obviously not as flexible as it could have been with a direct connection of iPad and Trinnov through my wireless domestic network. That would seem a very interesting option compared to an external screen or wired PC connection. All required information about VNC parameters can be retrieved in the setup/system status page.

The ST2-HiFi is designed to be configured with a 3D measurement microphone sporting four micro-pyramid transmission capsules (the central tallest element being surrounded by a triangle of shorter ones). Its purpose is to measure the characteristics of the loudspeaker layout in the room, that is to say capture an exact 3D mapping with a declared precision of 0.1° plus amplitude and phase response.

The microphone sits with its red dot facing forward to determine sound directionality. It must be placed at the exact listening position and at equal distance to both front speakers (or in front of the center channel if applicable). The microphone runs off a standard 9V PP3 LR61 battery located in its base. It has to be screwed on a mike stand or tripod to be completely stable during the acquisition process.

This obviously sets the base for and precision whereby the correction functionalities will process single or multi-point data referenced to the favored listening seat at ear height. Trinnov’s sophisticated multi-point algorithms can take into account the measurements of different positions to arrive at optimization for a wider sweat spot wherein a higher weighting can be assigned to the most important listening positions, a lower weighting to less crucial ones. Trinnov resellers can also assist remotely during this phase by having you connect the optimizer to your internet router.

The calibration is almost child's play but must be performed accurately. This requires a very precise position of the triangle formed by the two front loudspeakers and measurement microphone. The 3D mic arrives with four XLR tails which connect to the four balanced analog inputs. The order of each plug has to be carefully respected. I used my camera tripod to fix the data acquisition pyramid perfectly aligned vertically and horizontally.

I think the mike stand is the best option if you do not want to move your sofa to install your tripod at the exact listening point. In my case I had to push the sofa one meter behind its original/final position to position the tripod correctly. I subsequently modified the room acoustics partially.