Pro Tools HD Demystified

Walk into the typical professional recording studio, and chances are very likely you are going to see Avid’s Pro Tools running as the DAW of choice, even among increasingly stiff competition from other software and recording systems. While many are familiar with Pro Tools from home and project studios, thanks to the host-based versions of Pro Tools (meaning they require no external hardware outside of an audio interface), most studios running Pro Tools are using a Pro Tools HD system. Since no DAW provides an inherent “sound” (the audio being digital at that point), what’s the deal here? What is the difference between “standard” software-only Pro Tools and Pro Tools HD?

The short answer is that HD systems are a combination of an advanced feature-set version of Pro Tools software and specific external hardware, besides converters or an audio interface. However, to understand where Pro Tools HD systems are today, it helps to take a look at their origins. A long, long time ago, before the era of iOS devices and computers with 64GB of RAM, engineers and musicians lived in a place known as the late 1990s. We take for granted current laptops and desktops that can handle our 60-plus track mixes today, but go back just 15 or so years ago, and top-of-the-line computing saw you limited to dual 500 MHz processing. Needless to say, these machines were not going to be able to hack 32-track recordings by themselves with low latency and stability. Enter Pro Tools HD.

Rather than leave all the processing to your computer, HD’s hardware is composed of DSP acceleration chips, which offset many of the computing tasks required by the software, famously supporting its Time Division Multiplexing (TDM) and now AAX DSP plug-in formats. The benefits here are obvious, especially in a somewhat historical context, since your typical desktop, in 2000, was not packing the power to handle the required processing on its own. In addition to lowering your recording’s latency to essentially imperceptible levels (necessarily for multi-track recording), the acceleration chips gave you the ability to monitor through TDM plug-ins; a feat that might be commonplace now, but was ground-breaking at the time.

Outside of the added punch of more processing power (including not having to rely on your computer for a good chunk of plug-in processing), the Pro Tools software that completes the HD system offers some advanced features not found in the “standard” host-based versions of Pro Tools, historically giving you access to input monitoring (though this feature trickled down to all versions of Pro Tools 12), surround mixing, advanced video support, and many others. The software/hardware one-two punch also helps reduce latency, an integral feature when overdubbing audio and mixing with outboard gear in addition to plug-ins.

Needless to say, computing power has increased exponentially since the early days of Pro Tools HD systems, and while the benefits of external DSP are still the same as before (less taxing on your computer, improved latency), they are certainly no longer required to complete complex recording and mixing tasks. The current lineup of HD systems reflects this, providing options for DSP and non-DSP powered systems. Let’s get in deeper with each of them!

Pro Tools | HD Native

Introduced in 2011, the HD Native system is Avid’s response to a changing market and the way more and more artists and engineers make music. As the rise of the “laptop producer” took hold, it became apparent that there was a need for the software elements of Pro Tools HD, but not necessarily the hardware-provided DSP boost. As the “native” in the title suggests, this system provides no additional processing power (meaning no access to AAX DSP plug-ins) in favor of relying solely on your computer. As many modern producers work completely in the box, their machines tend to be pretty powerful and can easily handle the tasks at hand. HD Native Systems, like most HD systems, has a few configurations to suit different setups. You can select between an external Thunderbolt interface (ideal for those using a laptop or iMac), or a PCIe core card (for those working with a desktop machine). To this you can add one of Avid’s HD-series audio interfaces, such as the Omni, HD I/O, or HD MADI, or a compatible third-party converter, and you are all set.

HD Native gives you up to 256 audio tracks (at 44.1 kHz), if your computer can handle them, of course, along with 256 instrument and 516 MIDI tracks. Depending on which interfaces you choose, the system supports up to 64 channels of I/O with a latency of 1.7 ms.

A Native rig makes sense for those who do not require a lot of I/O, say for outboard gear or tracking multiple sources at once, but still need the advanced functionality of an HD system. If you travel from studio to studio for writing sessions, and work mainly on a laptop, the Thunderbolt option is especially appealing, as you can grab your laptop easily and go, and then easily re-connect to your HD system when you’re back at your home base.

Pro Tools | HDX

Pro Tools HDX, on the other hand, is the direct descendant of the external-DSP-powered HD systems on which many veteran recording engineers learned digital audio. Geared toward those with a professional or advanced project studio setup, HDX systems are based on the HDX PCIe card, which will require a desktop with a PCIe slot, or a PCIe to Thunderbolt chassis. One HDX card will get you 256 voices, with up to 64 tracks of I/O. You can create a system with up to 3 cards, so HDX is the way to go for any large-scale mixing studio that has an analog console or a solid collection of outboard gear.

Unlike the Native Rig, HDX gives you access to AAX DSP plug-ins, the 64-bit replacement for TDM plug-ins used in previous versions of HD systems. By off-loading some of your plug-in processing from your computer, the HDX system allows you to handle more plug-in-intensive, higher-track-count mixes than you might be able to, just working on even a well-powered computer. The DSP power of HDX also gives you slightly improved latency on the HD Native rig, always an important consideration with multi-tracking and overdubbing.

HDX sees its latency drop down to 0.7 ms, compared to the 1.7 ms of the Native version.

The Software

So those are the hardware options available, but how about the software? Regardless of Native or HDX, Pro Tools HD offers the same advanced options and perks that can make a world of difference to power users who are used to finding the most efficient ways to work under deadlines. A host of tools and commands not available in non-HD versions of Pro Tools, such as Continuous Scrolling, a Replace Clip command, TrackPunch, and others are designed to optimize workflow.

If you are working with audio for film, an HD system is essentially a must-have when working within the Pro Tools environment. Aside from 7.1 surround and Dolby Atmos mixing formats, HD gives you the ability to work with up to 64 video tracks in the timeline. At the end of the day, many pro studios rely on an HD system exactly for these reasons, and it’s an indicator of why so many recording and post-production studios use them.