Tag Archives: Rob Tavaglione

Dirac Live Room Calibration/Correction – A Real-World Review

Dirac Live
The Dirac Live software guides users through the steps of the measurement process.

Purpose-built rooms with ideal acoustic treatments may not need room correction software, but the rest of us do. With chart-topping artists producing hits in re-purposed bedrooms, basements, garages and hotel rooms, the need for acoustic analysis and correction is greater than ever.

I reviewed Sonarworks’ Reference 4 software for PSN back in 2018, so I was eager to compare this new calibration/correction system from Dirac, as it promises to bring some different methodologies, concepts and results.

Dirac Live seeks to correct room anomalies and inaccuracies in both the time domain and the frequency domain to improve the soundstage with greater imaging and localization of sound, increased clarity and intelligibility, as well as tighter bass response with fewer resonances. This is accomplished with a combination of linear- and minimum-phase IIR filters, as well as impulse response correction (affecting the timing of signals and the ratio of direct to reflected sound).


Out of the Box

Dirac Live is available in the ‘big four’ formats (VST, VST3, AAX and AU) for both Mac and Windows (OSX 10.11 and up, Windows 10, respectively). A measurement microphone is needed for calibration; I used a USB reference mic as provided by Dirac, but other models are suitable (at least models that a frequency response plot is available for). Dirac Live is compatible with all the major DAWs and supports nearly every multichannel format under the sun (2.0, 2.1, 3,1, 4.1, 5.0, 5.1, 5.0.2, 5.1.2, 6.0, 6.1, 7.0, 7.1, 7.0.2, 7.1.2, Quadraphonic, Pentagonal, Hexagonal, Octagonal and Ambisonic). The stereo version sells for $349, while the multi-channel version is $499. I tested Dirac Live in stereo, as Audio Units on a Mac Pro.

There are two components to utilizing Dirac Live—the Dirac Live processor plug-in that will be inserted within a DAW session, and the calibration tool program that will read your room’s response, create a custom filter(s) and communicate with the plug-in. After instantiating the plug-in, you open the calibration program which scans for a “device” that will ultimately store your filters and do the audio processing. Dirac also makes a hardware version for home hi-fi enthusiasts, but this pro version sees the plug-in as its “device.”

The measurement process is lengthy and very specific, but not difficult, just like all the other correction systems I’ve tried. The process involves setting system volume for the playback of frequency sweeps, measuring those sweeps from nine different positions surrounding your listening position and then fine tuning the correction filter that Dirac Live suggests. The whole process took only about 10 minutes and is rather interesting, as you can hear changes in room response as the full-bandwidth sweeps excite your room, creating some resonances and some dips, and it’s fun to correlate graphs of the measurement on screen.

Dirac Live’s Filter Design Page

Next, you’ll “proceed to filter design,” and this is where the really interesting part is. Dirac Live has automatically generated a response curve, but you can customize that curve by grabbing control nodes, moving them to desired frequencies and then boosting or cutting. You can also choose to move the “curtains”—the dotted vertical lines placed very low and very high on the frequency graph, which represent the lower and upper frequency limits of Dirac Live processing (it is not wise to try to achieve perfectly flat response all the way down to 20 Hz, or all the way up to 20 k; that would eat up a lot of headroom).

Furthermore, custom target curves can be loaded in .txt or .targetcurve formats and then “snapshots” can be taken of the current condition, modified and then easily compared to other stored snapshots without having to close the current project—nice for ultra-fine tuning of curves. For those of you who (like me) want to know exact frequency values of your room’s trouble spots, you can zoom into your response curve with your mouse scroll wheel and pan across the frequency spectrum with <hold+drag>.

Now that you’ve created (and possibly modified) your target curve, upon going back to your DAW session, the Dirac Live plug-in is now loaded with your correction curve. You’ll notice the output level of the plug-in may be attenuated; this is in order to give Dirac Live some headroom to apply processing (the amount of attenuation is about equal to the sum of your target curve’s positive and negative deviation). You can now turn the processing on and off as well as switch between different target curves you’ve stored without any jumps in level.

An impulse response page in Dirac Live
An impulse response page in Dirac Live

In Session

For in-the-box mixing and mastering work, an instance of Dirac Live inserted on the master fader informs your decisions and then must be bypassed during bounce/render, or else the Dirac Live processing would be applied to your mix. Wisely, Dirac Live can be automatically bypassed when bouncing/rendering with a simple preferences setting. For analog mixing, I inserted the plug-in on my stereo mix track, where I would monitor the processing but it would not be recorded into my mix file.

Even though it’s a little jarring to suddenly hear your system responding differently, I began mixing with Dirac Live and got slightly improved results on my first attempt. My room is in pretty good shape except for some low ceiling-induced bass issues (with adjacent dips and bumps) and a bit of low-mid mud. Dirac Live cleared up that mud and did quite a bit for that bass response, inducing me to fine tune my kick drum, boost that bass guitar and get my lead vocal right in the pocket. Frankly, it’s hard to describe the improvements I heard, as they were slightly different than what my system corrected with Sonarworks; not relegated to just frequency response, it sounded like phase accuracy had improved and imaging was more exacting, perhaps due to the impulse response correction, as well as precision filtering.

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One drawback to using Dirac Live was the inevitable switch to other monitors or headphones for reference. When using frequency challenged full-range monitors (Avantone Mixcubes), I had to bypass the Dirac Live processing, same as with headphones. I do wish that it offered correction for cans like Sonarworks does, which is as effective (if not more) as its correction for rooms/monitors.


The Final Mix

Even though it adds a little complication to mixing and mastering, Dirac Live can definitely improve monitoring accuracy to the point where it is worth the extra effort. At a cost of $349, the price is significant but not prohibitive, especially considering just how much knowledge can be gleaned from the measurement process. Furthermore, that knowledge can be very useful for the fine tuning of your room via furniture, bass traps, absorbers and diffusers that can help make Dirac Live’s job much easier.

If you work entirely in-the-box (and maybe even in a small boxy room), then software-based room correction is a no-brainer that should be utilized. If you do a lot of ensemble tracking or analog mixing like I do, then you may find the inevitable switching from unassisted monitoring to corrected monitoring to be a little jarring and maybe even disturbing to your “acclimation.” How I wish there was a freestanding hardware-based calibration/correction device that could be placed in-line before my main monitors so I could easily hear everything with proper correction, maybe even with headphone amps with their own specific correction.

Until that time comes, I still recommend Dirac Live for the wealth of knowledge it teaches you about your room, the tremendous flexibility it offers and what appears to be the best-sounding room correction algorithm on the market today.

Dirac Live • www.dirac.com

Original Resource is ProSoundNetwork.com

Austrian Audio OC818 Microphone – A Real-World Review

Austrian Audio OC818 Microphone
Austrian Audio OC818 Microphone

While plug-ins seem to gather most of the “revolutionary new product” excitement, a team of 20-plus ex-AKG engineers has formed Austrian Audio and put out the company’s new OC818 microphone, combining the best of the old with a healthy dose of some extraordinary new features.

While plug-ins seem to gather most of the “revolutionary new product” excitement, a team of 20-plus ex-AKG engineers has formed Austrian Audio and put out a new microphone that combines the best of the old with a healthy dose of some extraordinary new features.

Out of the Box

With a small, flat, rectangular body somewhat reminiscent of a C414, and a capsule (Austrian’s handmade CKR12) made with similar dimensions, not to mention properties similar to a CK12 capsule, comparisons to the AKG classic are certainly founded. The similarities continue with multiple polar patterns (cardioid, omnidirectional, figure 8, hypercardioid), two levels of defeatable padding/attenuation (-10 and -20 dB) and three levels of defeatable highpass filtering (40, 80 and 160 Hz). A major difference, however, is the ceramic capsule housing that contains the dual diaphragms. Ceramics are low in resonance, insensitive to temperature changes and quite stable, contributing to the consistent performance of the diaphragm. Such consistency is achieved that Austrian Audio boasts that all OC818s are close enough in performance to be a matched pair, and that in cardioid mode, any OC818 microphone is also a match for any other OC18 microphone (the OC818’s single-pattern little brother).

Beyond construction and materials, what really sets the 818 apart are its futuristic electronics, which include dual outputs, wireless remote control and post-production flexibility.

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Via a small LEMO connector on the rear of the mic (and a supplied short LEMO-to-XLR-M cable), each diaphragm of the 818 can be output separately, allowing astute engineers to combine the two signals and manipulate their polarity and gain for various polar patterns—or simply use the free PolarDesigner open source plug-in (VST, AAX, AU with Windows or Mac) to do the dirty work for you. Deep control is provided via one to five crossover bands with selectable crossover points, band solo/mute, full automation, EQ for dialed-in free or diffuse field response, proximity effect control, store/recall/share of presets and phase linear operation.

That same LEMO connector can conversely be connected to the optional OCR8 Bluetooth dongle, and with the mic’s polar pattern set in the “black circle” position, wireless control is achieved via the free PolarPilot application (Android or iOS). Real-time control is provided with the ability to create as many as 255 discrete polar patterns, save/recall/share settings, a 60-second overload/clipping monitor and logger, and storing of the last setting used within the 818, even without the PolarPilot app. This is all done with only microprocessor control of bias voltages. The actual signal path remains purely analog; there is no use of digital signal processing or conversion.

The kit is completed with an aluminum carrying case, a largely plastic (yet sturdy) shock mount, foam windscreen and standard mic stand mount.

In Session

Naturally, I started testing without any apps or wireless control, with cardioid usage on vocals, drum room, tambourine, cajón and acoustic guitar. Yes, I realize those are radically divergent sources, but I grouped them all together, as the 818 showed no difference in its response. About as neutral as a large-diaphragm condenser mic can be, the 818 always provided seemingly perfectly flat response, regardless of sound pressure level, placement or frequency content. Vocals (in cardioid with no pad and 40 Hz HPF) were completely un-hyped and natural, absent of excessive resonance, sibilance, mouth noises (i.e. clicks, pops), chestiness, high-mid frequency emphasis or excessive proximity effect. Drums (cardioid or omni, -10 dB pad or up full) showed only minimal cymbal preference (likely created by my room), an extended bottom end and very natural dynamics. Instruments, including tambo, lacked harshness, translated accurately and sounded just like being there. The 818 lacked the depth of a ribbon mounted low on my cajón and lacked the snap of a crispy condenser when mounted high, but with a neutrality that many engineers might just prefer for either position. Off-axis pickup was smoother than typical for an LDC.

At times, I found the OC818 microphone to be a little too neutral for vocal work, but the super-cardioid pattern brought a little more excitement and presence, as well as directional focus to my vox. The highpass filtering proved its mettle here too, with the second-order filters at 40 and 80 Hz being obviously useful, but the multi-order 160 Hz position (first order gently down to 80, a steep second order below) being nicely sloped and helpful for seriously thinning out backup vocal stacks.

Figure-eight patterns found the OC818 sounding more neutral and similar to its cardioid pattern than typical. For classic fig-eight apps like two-person harmony vocals, dual handclaps and drum room, you’ll find airy naturalism, balanced frequency response and nice null rejection.

PolarDesigner offers some seriously advanced uses for those who want deep control. I tracked some drum roomage using the supplied LEMO-to-XLR-M connector and sent both diaphragms to a stereo track. I then applied PolarDesigner and found a world of options. Changing the polar patterns was easy enough and quite useful, but having five bandwidths and allowing each to have its own directional property was more than I could find use for, considering my need and habit of working quickly. Basically, I found one full-frequency band of control sufficient. What I did find very useful was the proximity effect control; you can boost or cut it variably, and a little careful boost brought some very nice low-end girth and boom to my drum room. For those tracking either dialogue or Foley for film production, this app’s advanced control could be extremely useful, even if it may be a bit much for standard music production or those with shorter attention spans.

If you don’t need to track both diaphragms, then you can insert the OCR8 Bluetooth dongle into that same LEMO connector and enjoy some remote control via PolarPilot. Being able to change patterns, filters and pads remotely while seated right in the monitoring sweet spot obviously has its attractions, but I found myself at a distance of 35 feet plus, just barely outside the operating range of the current Bluetooth standard. (The newly announced standard will increase that range.) Unfortunately, my iPhone 8 Plus couldn’t manage to stay connected with the app even at close distances, with skittish performance and dropouts. What I did manage to do was quite useful, though; I set the 818 for a wide cardioid pattern, with no pad and the 80 Hz HPF, and enjoyed my very favorite setting for vocal work. With this setting stored in the 818, I could recall it when needed, even without the app. I hope that Austrian Audio can work the bugs out of the OCR8 dongle, as the app’s functionality could be a major benefit.

The Final Mix

Considering the incredible versatility of the OC818 microphone, the quality kit, the post-production flexibility and PolarPilot’s utility (even if hampered by quirks and distance), the 818 is an easy recommendation at a very reasonable $999. Easy stereo-pairing with other 818s and the OCR18 is another big plus that makes these mics a great choice for live show “tapers,” recording ambiences and classical recordists. It seems to me that Austrian Audio is off to a great start and are moving their legacy forward in worthwhile new directions.

Original Resource is ProSoundNetwork.com