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Merging Hapi

Networked Audio Interface
By Hugh Robjohns

Networked audio is becoming ever more popular and affordable, as with Merging’s Hapi.

Merging Technologies are a Swiss pro-audio manufacturer who are well-known in the higher echelons of live sound, post-production, broadcast and mastering, especially throughout Europe, but less so in the music and project sectors. This is a great shame because Merging’s hardware and software products are, refreshingly, designed and built up to the task, not down to a price. Yet having said that, the prices really aren’t as scary as you might think, and the build quality is everything you would expect of a high-end manufacturer. In many ways, Merging are one of the best kept secrets in pro-audio!

I’ve used Merging’s Pyramix DAW software often over the years, but I was quite intrigued to discover that the company now offer hardware audio interfaces too, and more so when I learned that they function with any DAW — not just Merging’s — as a standard ASIO or Core Audio interface. Currently, Merging have two such interfaces: the Horus, and it’s smaller sibling, the Hapi, which is reviewed here.

Merging HapiIf you’re wondering about the names, they’re not acronyms; Merging just like ancient Egyptian deities. Horus was the son of the goddess Isis and her resurrected husband, Osiris. (There are some juicy extras to that particular story, but I’ll let you do your own research!). Hapi, not surprisingly, is one of Horus’s four sons, and is usually depicted with the head of a Hamadryas baboon. That is the figure you can see carved into the front panel of the hardware unit, next to the illuminated triangular on/off (large) and home (small) buttons. (The Horus features a carving of the head of a falcon, in case you were wondering).

Back in the modern world, the Hapi is essentially a very configurable and scalable ASIO/Core Audio interface that connects to the host computer not by USB or Thunderbolt, but via a standard Cat 5e or Cat 6 gigabit Ethernet network, using the Ravenna (layer-3 audio-over-IP) protocol. Ravenna is fully compliant with the AES67 standard for inter-operability with other network audio devices, and works with entirely standard off-the-shelf network equipment. I simply plugged the Hapi into a spare port on a gigabit router within my own domestic wired network. The Hapi can be used as a stand-alone interface, or in concert with Horus or other Ravenna products to provide additional I/O connectivity over the network — with potentially hundreds of channels of real-time, low-latency audio.


In its most basic form, the Hapi hardware provides eight AES3 (via AES59 D-Sub) and eight ADAT (light-pipe) inputs and outputs. The ADAT port can also be configured for two-channel optical S/PDIF, if required. The unit’s connectivity can also be expanded further via two option card slots, with options including eight or 16 channels of analogue I/O in various flavours (see box), or 64 channels of MADI, plus up to eight more channels of analogue inputs and outputs. And that’s all in an elegant, 1U rackmount case with an integrated mains power supply. For the record, the larger 2U Horus features 64 channels of MADI and 24 channels of AES3 I/O as standard, with six option card slots for up to 48 channels of analogue I/O or additional MADI ports.

All of the analogue input card options feature excellent high-quality mic/line preamps with all the usual functions, and most of the analogue boards are offered at two price levels, depending on whether you need a 384kHz sample rate and DXD/DSD format support or not. The standard cards support all the usual PCM sample rates up to 192kHz (see box). Digital synchronisation is provided via word-clock in and out on BNCs, and the unit also accepts linear time-code (LTC), MIDI and video references via a D-Sub connector. The Hapi can also serve as the Ravenna network’s master clock, if required, and in addition to a universal mains inlet IEC socket (90-260V AC), a 10-14V DC coaxial power input is also available as an option for mobile battery-powered applications.

The format setup page in the Hapi’s browser interface.The format setup page in the Hapi’s browser interface.The Hapi’s maximum channel count and minimum latency vary with operating system and sample rate. Under Core Audio on OS X (10.8 and later) the system can accommodate up to 64 channels at all sample rates with a 32-sample minimum latency. Under ASIO on Win 7 (and Win8, 32- or 64-bit) it supports 64 channels at base sample rates, 32 at double rate, 16 at quad rates, and eight at DXD and DSD. The minimum latency is also higher at 64 samples.

The hardware unit is finished in an off-white paint, and features removable rack-ears. The only controls on the front panel are illuminated power and home buttons on the left, and a colour 160x128-pixel OLED display and rotary encoder/button on the right. Both quarter-inch and 3.5mm headphone sockets are also provided on the front panel. The rear panel has an IEC mains inlet, two option card slots, a 25-pin D-Sub for the AES3 I/O, a pair of ADAT light-pipe ports, two word-clock BNCs, a 15-pin D-Sub for the time-code, MIDI and video sync connections, and two RJ45 network ports.

Hooking Up

The Ravenna protocol operates over standard gigabit networks, and the Hapi will negotiate its own IP address with the network’s DCHP host. It can also be configured manually, if preferred, which is what I had to do because of the unusual network configuration at Robjohns Manor. Once the hardware unit is on the network, and the supplied software is installed on the host computer, the unit can be fully configured via a web interface that runs on the computer’s default web browser. The software package includes ‘MT Discovery’, which is an application that finds the hardware on the network, and the ‘Ravenna Easy Connect’, which helps to hook the interface’s I/O into the DAW via the supplied ASIO or Core Audio drivers.

I found using the web browser to configure the unit more convenient than the hardware’s OLED screen (mainly because of screen size and where I’d installed the rack unit!), but both present all the same options and parameters. On the browser display, separate tabs are provided to access various aspects of the Hapi’s configuration, and these are replaced by individual menu items on the OLED display’s main page. For example, a Headphone tab selects the required source channels and level, while the Meters tab reveals whether signals are present (or not) on the A-D, D-A, AES and ADAT ports. On the browser these ‘meters’ are really signal present/overload indicators rather than proper meters — an aid to fault-finding rather than accurate level setting, which is better done in the DAW itself — although the OLED display includes proper bar-graphs for the analogue I/O. The signal levels at which the metering changes colour can also be configured, with the red section activated anywhere between 0.0 and -2.0 dBFS, and the green/yellow border between -24 and 0 dBFS. The meter decay time and peak hold can also be programmed.

The Ravenna Easy Connect application.The Ravenna Easy Connect application.An I/O & Sync tab indicates the status of external sync signals, and selects the system’s sync source from the digital inputs, the Ravenna network itself, or the internal clock. Additional pages indicate the clock frequency and accuracy, and the incoming and outgoing time-code values and levels.

If analogue Mic/line input cards are fitted, the Preamp tab displays the appropriate number of independent channel strips to control mic/line input selection, 48V phantom power, -10dB pad, polarity inversion, and 80Hz high-pass filter (at 12dB/octave). The applied gain (0-66 dB) is indicated numerically, and adjusted either by virtual faders or +/- nudge buttons (in 0.5dB increments). Any combination of channels can be allocated to one of eight control groups for stereo/multi-channel applications.

The last tab accesses the main Setup page, with seven sub-pages covering hardware information, network configuration, general system parameters, sample rate and DXD/DSD formats, internal audio routing, and individual I/O module finessing. Regularly used setups and configurations can also be saved and loaded as presets, if required, and another button resets the unit to the factory condition.

In Use

Setting up the Hapi is surprisingly straightforward, and once I’d persuaded it to talk to my (admittedly unusually configured) network router I was up and running very quickly, with the software finding the Hapi straight away and allowing me to configure it for the DAW of my choice. I used the Hapi as an ASIO interface with Reaper, SADiE and Adobe Audition without any issues. The interface was totally stable and rock solid throughout the review period, and the Ravenna network proved glitch free and with adequately low latency (see below).

I was greatly impressed by the analogue converters, especially the D-As which measured extremely well. Using an Audio Precision test system I recorded an AES17 (A-wtd) figure for the D-A stages of 126.3dB and a THD+N (noise and distortion) result of 0.0002 percent. The A-Ds measured 121dB and 0.001 percent, respectively. These figures place the Hapi very near the top of my AES17 performance charts, sitting in second place between the Apogee Symphony and Benchmark DAC2 HGC on the D-A side, and in fourth place between the Lynx Hilo and Apogee Symphony for the A-D side. Apparently the A-D converter is built around an Arda Technologies AT1201 chip, which is a design I had not come across before, but it clearly delivers superb performance, both measured and auditioned.

The Hapi browser’s preamp page.The Hapi browser’s preamp page.The analogue inputs and outputs accommodate signal levels up to +24dBu (+13dBu for the mic input with the pad off), and gain-matching between linked channels was easily within ±0.25dB. The mic preamps are very clean, neutral and quiet (EIN -128dBu), and compared very favourably with those in my SADiE LRX2 location recorder and GML 8304. I would certainly be very happy to use them for any kind of recording project as they have generous headroom, low noise, and a very transparent sound quality. Crosstalk between adjacent channels was better than 125dB at 1kHz in the A-D cards, and around 10dB better still in the D-As.

Routing signals between the physical inputs, outputs and the Ravenna network is very straightforward and flexible, allowing the unit to be used for audio format conversion and signal splitting in addition to its primary role as a DAW interface. The measured latency between the analogue inputs connected directly to the analogue outputs within the Hapi measured 1.2ms at 44.1kHz, and 0.50ms at 96kHz. Routing the analogue input signal over Ravenna to the DAW and back to the analogue output recorded latencies of 7.05ms (with a 64-sample buffer) at 44.1kHz, and 5.85 at 96kHz.


While I was well-aware of Merging’s Pyramix DAW software, Ovation media sequencer and VCube video player — all popular products in the post-production, theatre and live-sound arenas — the Company’s Horus and Hapi interfaces had somehow slipped under my radar unnoticed. However, network audio is a rapidly developing area; already massively popular in live and theatre applications, and increasingly so in the broadcast and educational markets, too. While conventional Firewire, USB and Thunderbolt interfaces are perfectly adequate for most music and project studios, networked audio solutions have some significant advantages in multi-room setups, or where it is preferable to place the audio interfaces within the studios (or live areas) rather than in the control room. After all, Cat 5e cable is a lot cheaper and easier to install than microphone snakes, especially for long cable runs, and sharing interface resources between multiple studios and control rooms is very easy with this technology, too.

There are several competing layer-3 audio-over-IP protocols, the better-known ones being Ravenna, Dante, Q-LAN, and AVB. The only other studio network interface I’ve reviewed to date (Sound On Sound, March 2013) was the Focusrite Rednet interface system, which uses Dante. However, Prism Sound’s Lyra and Titan interfaces have been designed with AVB in mind, and now we have Merging’s Hapi and Horus Ravenna interfaces to add to the steadily growing list of IP interfaces. Clearly, this is a market sector which many manufacturers think is important, and the Audio Engineering Society has underlined that by defining a unified audio-over-IP standard (AES67) which should make all of these layer-3 systems fully inter-operable when the individual manufacturers complete their compliance work. I expect to see a lot more activity in this area in the future, and Merging have set a high benchmark standard with the Hapi. If you are considering a new and expandable interface of the highest quality, I strongly urge you to investigate the Hapi.


The obvious alternative to the Hapi and Horus studio interfaces are the Focusrite RedNet Dante interfaces. The unit packaging is different, though, with Focusrite offering separate A-D, D-A, AES3 and MADI units, rather than the configurable integrated options of the Merging products. The Merging units are also generally more cost-effective, and boast slightly better technical performance specs.

Interface Cards

The Hapi shares a range of interface cards with the Horus. The analogue cards are available in standard and premium versions, the difference relating to the sample rates they support. The standard versions handle all the usual PCM sample rates up to 192kHz, while the premium cards go further to cater for 384kHz, plus the DXD (352.8kHz) and DSD256 formats as well.

The four original analogue boards provide eight input or output channels, so there are two eight-channel mic/line input cards (AD8D standard and AD8DP premium) and two eight-channel line-level output cards (DA8 and DA8P). Usefully, the standard and premium input cards also provide eight direct analogue outputs from the preamp channels to allow separate recording or mic-splitting duties.

However, the company have also just introduced a brand-new analogue I/O card (ADA8), which provides eight mic/line inputs and eight line outputs on the one card, supporting all sample rates up to 192kHz. Impressively, it has been priced the same as the current AD8DP mic/line premium input card. Fitting the new ADA8 card in both slots provides the Hapi with 16 analogue I/O channels, plus eight AES3 and eight ADAT, which is quite a lot of connectivity for a 1U box. In the Horus it allows 48 channels of analogue I/O, plus 24 channels of AES3 and 64 of MADI.

A MADI option card is also available in two formats (MADM multi-mode or MADS single-mode — referring to the type of optical fibre connection), but both provide 64 channels of I/O at sample rates up to 384kHz, plus DXD.


Hapi base unit (8xAES3, 8xADAT, Ravenna, ASIO, & Core Audio), £1834.80$2495.

Option cards:

  • AD8D standard eight-channel mic/line/direct out, £1294.80$1669.
  • AD8DP premium eight-channel mic/line/direct out, £1834.80$2353.
  • DA8 standard eight-channel line out, £864.00$1122.
  • DA8P Premium eight-channel line out, £1294.80$1669.
  • New ADA8 eight-channel mic/line I/O, £1834.80$2495.
  • MADM multi-mode MADI-64, £864.00$1122.
  • MADS single-mode MADI-64, £972.00$1259.


  • Extremely high technical performance.
  • DXD/DSD capability.
  • Flexible I/O facilities and options.
  • Mic/line capability on all analogue input cards.
  • MADI interfacing if required.
  • Very cost-effective network interface.
  • Comprehensive control interface in hardware and web browser.


  • I really can’t find any...


A compact but versatile, and very high-quality, high-channel-count audio interface using the Ravenna audio-over-IP network protocol and hooking into all standard DAWs via ASIO or Core Audio.


See pricing box.

Emerging Ltd +44 (0)118 402 5090

See pricing box.

Independent Audio +1 207 773 2424.

Published March 2015