The Dirac Path
When DSP smooths things over
Above, some see a beautiful room. Others see an acoustic nightmare and its solution.
If you designed an amplifier or preamp or DAC with a frequency response curve that matched the frequency response of the best loudspeakers in the world, you'd probably throw that circuit design straight into the trash can. Loudspeakers, being mechanical devices, are the most inaccurate part of an audio system (potentially matched or exceeded only by turntable cartridges), and their response is made even worse when they couple with the room, whose quirks and non-linearities are superimposed on the speaker output.
This is why hi-fi experts, including Kevin Deal, place so much emphasis on physical loudspeaker setup, as there is no easier way to decimate the value of your audio system than to simply plonk your loudspeakers anywhere in the room. Good placement greatly helps to even out and flatten that response curve.
Another way to alleviate these issues is to use digital signal processing (DSP) software. These programs analyze the room using test tones and a microphone and then modify the audio signal in real time to fill in gaps or reduce excesses along the frequency range.
Many purist audiophiles refuse to use DSP, relying instead on careful speaker placement (including good stands and feet as needed), subwoofers, acoustic treatments, electronics isolation, supertweeters, and so on, to get as neutral a sound as possible. However, not everyone can deploy bass traps, quadratic diffusers, and multiple subwoofers, and so we support the use of DSP with one strong caveat: Always get your speakers positioned as best as you possibly can! Do not try to use DSP to fix gross errors.
Dirac Onboard
Perhaps the most famous room correction suite is by Dirac, a company headquartered in Sweden. The Dirac software is installed on a laptop, and you need a Dirac-compatible product, which can be a receiver, amplifier, preamp, DAC, or even powered loudspeakers. A calibrated USB microphone is connected to the laptop which needs to be on the same Wi-Fi network as the component, so that the Dirac program can play a series of test tones through the system as the microphone is placed at various points in the listening area (you will need a tripod for this). The sound files are analyzed, and an equalization file is created and uploaded to the component.
The Upscale brands that offer Dirac on some or all models are Arcam, Denon, Integra, Marantz, NAD, and Onkyo. Some come with it free, others charge a nominal fee, and some require you to pay the whole fee. Out of the Dirac-compatible brands, Arcam, NAD, and Onkyo ship with USB microphones, but either way, we recommend buying the dedicated $79 Dirac-recommended UMIK-1 by MiniDSP.
Dirac Versions
The Dirac suite comes in three versions. Dirac Live Room Correction Full Bandwidth is the most expensive, which offers frequency response correction from 20 Hz to 20 kHz. The slightly cheaper Limited Bandwidth version addresses only the 20 Hz to 500 Hz range to fix bass and upper-bass issues. People who choose this option often correct higher frequency issues with absorbers and diffusers in the room. Bass is a lot trickier to physically control, needing large living-room-unfriendly bass traps.
Don't confuse Limited Bandwidth with the third version, Bass Control, which is like an expansion pack for either of the Dirac Live versions, and is for audio systems that use one or more subwoofers.
Dirac Effects
While DSP correction can bring huge changes even to stereo systems, some of our favorite before/after moments are when you run Dirac on a cinema system and replay your favorite movie scene. Breaking glass shards get sharper, shrapnel whizzes over your head more convincingly, distant sounds seem properly far away (not just quiet), and you'll notice that not only does the bass kick in swiftly, it also comes to a dead halt instead of ringing through the room. In action scenes, the effect is almost brutal in its immersion. It's hard to go back after you Dirac.
Digital Interactive Room Audio Correction? Nope, Not At All
Dirac is plausibly an acronym of an engineering department mouthful such as Digital Interactive Room Audio Correction, but it's actually named after the English physicist Paul Dirac, who among other things developed the Dirac delta function which is used at the heart of impulse response testing.
If you stand in your room and sing out notes from as low as you can go to as high as you can go while remembering which notes resonate and which ones seem sucked out, you are testing the frequency response of your room.
If you clap your hands listening for echoes and seeing how long before they die out, you are testing the impulse response of the room. In an audio system, impulse response can be affected by things such as driver overshoot or speaker cabinet resonance. Dirac is unusual among DSPs in that it offers impulse response correction as well as frequency response correction.
A $7,000 amp to anchor a $50,000 system?
Recently, Craig Chase reviewed the PrimaLuna EVO 300 Hybrid Integrated Amplifier on 'Secrets of Home Theater and High Fidelity'. He put it through its paces for music and movies, and also auditioned it as a headphone amp, and wrote, "The thought hit that it was going to be a sad day when this amp had to go back to PrimaLuna. It is more than an outstanding amplifier."
Craig found that the PrimaLuna worked beautifully with whatever speakers he tried it with, including a system featuring Diptyque Audio and Sonus Faber. This led him to conclude, "This $7,000 PrimaLuna amp would be quite happy to be the anchor of this $50,000 system."
Subwoofer and headphone outputs tend to be afterthoughts on many amplifiers, but not on PrimaLunas. Both are transformer coupled, using the MOSFET output stages. For subwoofers, this means that they share the same sonic signature and timing as the speakers. Headphone users will find that the PrimaLuna hybrid will drive any headphone and do so with incredible fidelity.
"This amplifier will be sorely missed," writes Craig at the end of his review, and we understand completely. PrimaLuna's growing line of hybrid products is on the radar of people interested in both tube and solid-state designs and can keep listeners in both camps extremely happy.
New Video: Auris Audio Headonia 300B
The hedonistic Auris Headonia is a $13,000 300B tube headphone amp with an amazing 7 W of power that'll drive even two pairs of Hifiman Susvaras. Jordan and Kevin report.