Review: Merging Technologies Hapi

Stephen Bennett puts the Swiss manufacturer’s latest piece of Ravenna-compatible hardware through its paces.

No, this isn’t a review of a piece of equipment that will improve your mood – Hapi is actually the latest audio interface from Merging Technologies.

Continuing to name its interfaces after Egyptian deities, the new boy on Merging’s block gets its moniker from one of the four sons of Horus, which is another Merging product, so surely we can expect at least three more siblings spawned from the company’s flagship interface? The naming of Hapi makes a lot of sense really as it shares many of the features of its parent interface, albeit in a smaller, less expandable package.

Hapi is unusual in the world of rack mount interfaces, as it utilises Ethernet-based connectivity to communicate with the computer, shifting audio via a single Cat cable. Hapi talks with the outside world via Ravenna, an AES67-compatible layer 3 IP-based audio networking protocol, which provides up to 88 input and 90 output channels over a single Cat5e or Cat6 cable to any other Ravenna-based devices on the network, including the Horus interface. Hapi will happily – see what I did there? – play ball with any existing computer networks. The use of Ravenna enables the interface to work at extremely low latencies and jitter rates and synchronisation information – including Linear Time code (LTC), Video Reference and Wordclock – is also handled alongside Ravenna.

Hapi is a 19in one-unit-high modular multichannel, networked audio interface and A/D converter. It is beautifully finished in ivory white and, as you may expect from a device built by the Swiss, it feels solidly constructed with the minimalist front panel featuring just a data entry knob, an OLED screen a headphone jack and a backlit Merging logo that doubles as an on/off switch. 

Merging boasts that the Hapi is extremely frugal in power usage, going so far as to provide display of power consumption, and is happy to print detailed technical specifications of the unit in the user manual, right down to the gain behaviour of the direct output section. 

The rear panel of the basic Hapi features a D–connector for AES channels 1-8, an SPDIF/ADAT connection, BNC connectors for Wordclock, a D-connector for Sync purposes and two Ethernet sockets for connection to the computer and other Hapi or Horus interfaces. The two slots for the optional input and output modules sit next to the IEC mains connector – the Hapi’s switchable power supply will work at 240V or 110V AC and there’s also a DC power supply option that can be used to directly power the unit on location or act as a backup supply in situations where you think you may lose mains power. All the inputs and outputs on Hapi are handled by D-subs, which makes sense as most professional installations use the Tascam connectors these days, although Merging can provide you with breakout cables if you’re so uncool as to be still using XLR and TRS connectors. 

Hapi is a modular unit, working happily – look, I’ll stop now – with Apple’s Core Audio and Steinberg’s ASIO 2.2 audio protocols. The interface can handle two modules at a time and are the same ones that can be fitted to the Horus, providing quite a few operational options. The base unit provides eight channels of AES digital I/O and eight channels of ADAT interfacing, which can then be expanded by filling the two module slots. Most modules are available in ‘standard’ and ‘premium’ versions – the former are able to work at sample rates of up to 192kHz, while the latter are DSD/DXD compatible. Merging produces modules that offer eight-channel microphone and line level input cards with direct outputs (AD8D and AD8DP) and eight-channel line output cards in both versions (DA8 and DA8P), a standard eight-channel microphone/line digital to analogue (D-A) card (ADA8) and a MADI I/O card. The direct outputs on the mic/line cards enable the user to split off the analogue signal immediately after the mic preamplifier, which can then be used to feed monitors or another recording device. The A-D converters on the premium cards feature extended headroom for DSD work and the stated technical specification of both types of standard module is very impressive and comparable with the best audio interfaces on the market today. 

This modular flexibility means that you can specify precisely what connectivity you require from your interface and, as Hapi is perfectly capable of working as a standalone unit, I can see it getting a lot of love from those of us who create permanent audio installations. The MADI module provides users with up to 64 channels of I/O, and both coaxial and optical interfaces are available simultaneously and configurable in blocks of eight channels – the one limitation being that Hapi can only handle one MADI module at a time. Modules can be changed by the user so it’s conceivable that you could purchase more than two and swap them out for specific tasks.

The supplied software installs the Ravenna control and MTDiscovery applications and the ASIO and Core Audio drivers. MTDiscovery displays all of the Ravenna-compatible devices that you have connected, including Hapi and Horus, ASIO, Core Audio and MassCore, the real-time engine used by Merging’s Pyramix DAW. The Merging/Ravenna Easy Connect application allows you to connect and view the various Ravenna streams on your network. 

Once your physical connections have been set up, Hapi can be controlled from the front panel display via a ‘push and turn’ menu system or a web browser on the computer. The browser interface presents a graphic view of the interface on the screen, with various function menus located under the Hapi logo. The Meters menu provides an onscreen display of the audio coming into, and out of Hapi but the latency in the display makes this feature only useful for ‘signal present or absent’ duties – although it does enable you to easily see if the audio is coming in too hot. The meters on the unit itself provide a more accurate indication of actual input and output signal levels. The Preamp menu displays an on screen mixer, showing the available analogue inputs. Here, users can switch between mic or line level inputs, engage the +48V phantom power and swap the phase of the channel. Pad and 80Hz high pass filter buttons sit alongside a low impedance input setting, while the long throw input level faders can easily be grouped together. The I/O and Sync menu allows the user to adjust various synchronisation settings, while the Headphone menu has the routing options for the front panel headphone jack. 

The Setup menu opens a page where you can view and control most of the Hapi’s other parameters, including system and Wordclock output sample rates and a section where the user can override the default Network settings to let Hapi play nicely with existing infrastructure. The Presets sub-menu enables the user to store and load up to five preset banks of Hapi configurations at one time. The Routing menu requires some extra explanation as Ravenna offers some quite complex routing options – Merging has applied a ‘route to’ instead of the more common ‘route from’ philosophy in its connection methodology and the company says that, after an initial learning period, this presents a more efficient process for connecting Ravenna inputs and outputs – and they are probably right! You choose where you want your audio to go, decide what input you want to feed to that output, and the software offers up all the possible connectivity options. To avoid confusion – they hope – Merging has limited the routing options to blocks of eight channels so you can, for example, route eight AES input channels to eight MADI outputs. It sounds a tad complicated when written down, but it’s much simpler to grasp in operation.

The front panel of the Hapi can also be used to set these options, so you don’t need to use a computer to adjust the settings. The OLED screen is clear and the menu system relatively simple to use. 

In Use

The Hapi that was supplied for the review by UK distributor emerging was loaded with both standard and premium mic/line cards, so I connected the monitor outputs to my ATC SCM50A powered monitors and got to work right away. Setup of the unit went swimmingly and my first port of call was to listen to some familiar mixes through the ATCs. It was obvious from the word go that the D/A converters and analogue electronics on the Hapi are of an extremely high quality and easily up to par with my current beau, the two-channel Metric Halo ULN-2 interface, while also being audibly superior to the Apogee Duet II, RME and Digidesign 192 I/O interfaces I compared it with. The microphone inputs are extraordinarily clean with bags of headroom and again, are similar in quality to those in my Metric Halo unit, which are themselves considered exceptional, so the Merging unit is impressive in this respect. I used the Hapi to record acoustic guitars, a string quartet and drums using a brace of AKG 414 XLS and Neumann KM84 microphones. I have a lot of experience of recording similar instruments using these microphones and the Hapi did not disappoint. Merging’s interface also passed my ‘if it’s a good preamp it’ll make the Shure SM57 microphone shine’ test on snare drum and Celestion-filled guitar cab, which is not something that all microphone preamplifiers that I’ve used can do.

The Hapi is a compact, flexible and relatively inexpensive high-quality audio interface that will be equally at home in the studio, on the road or in a fixed installation. The Ravenna audio network means that latencies are ultra low, and the flexibility of the connectivity with other devices using the same protocol, even over standard networks infrastructure, means complex systems are easy to manage. Merging has taken the technology it premiered in its Horus interface and created an impressive offspring that any self-respecting audio engineer would be Hapi to own.

Stephen Bennett has been involved in music production for over 30 years. Based in Norwich he splits his time between writing books and articles on music technology, recording and touring, and lecturing at the University of East Anglia.