IK Multimedia ARC System 2.5 by Sound-Guy
What's an ARC?
ARC is IK Multimedia's electronic "Advanced Room Correction" system, a combination of hardware (microphone) and software that is intended to improve room acoustics. The original version was introduced in 2007, and was the first software-based room correction product. Version 2.0 was released in 2012 with better software and an improved mic. ARC 2.5 was introduced in late 2017 with improved software and yet another mic.
Speaking of Mics
Why another mic? Traditional condenser mics are subject to unit to unit variation, and drift in frequency response over time, as much as several dB. Although the ARC software has always taken into account the nominal performance of each mic model, there could be up to 3 dB variation from mic to mic. The new MEMS mic alone costs about $/€70, which is not much considering what this mic can do. Used with ARC 2.5 software, it is flat to within half a dB from 20 Hz to 20 kHz.
The ARC 2.5 software is free to current ARC 2.x owners (and will be familiar with little visible change other than the new mic choice, although it's been improved under the hood with better frequency resolution among other tweaks). If you don’t have ARC 2.x already, the software with the new mic is $/€200.
I’ve used ARC for several years and found it to be a valuable asset. I just noticed that a full review of ARC hasn't been presented on this site in six years. That review covered ARC 1.0, although the article has a picture of the ARC 2 box! ARC 2.0 was a significant improvement over version 1, so is this "half" revision 2.5 only a slight improvement, or worth the upgrade? And if you don't already own an ARC version, is it worth the cost?
A New Mic
MEMS stands for MicroElectro Mechanical Systems, a technology that has been used for the microphones in millions of phones, tablets and laptops over the past decade. But until now MEMS mics have not been used for any studio applications, since their extremely small diaphragms yield lower signal-to-noise ratios than we like in a studio mic. But that may change in the next few years with new MEMS technologies being developed, and for a measurement mic, the signal to noise issue is not a serious problem, especially considering the upside of these mics. They are extremely consistent from one unit to the next. Millions of them can be made with frequency responses tracking within half a dB. And unlike traditional condensers, they are extremely rugged to physical shock and high humidity, and are very stable over time.
The Whole Package
I've used ARC 2.0 since 2012, so I had to buy only the new MIC and download the free upgrade. The mic is unlike the previous heavy metal body condensers - it is a small, black plastic device that weighs only 25 grams! That's under an ounce. The previous metal mic weighed about 150 grams, over five ounces. In spite of appearances, the MEMS mic is rugged - dropping it on a floor will likely do nothing whereas dropping a metal body condenser mic is likely to end it's usefulness. It comes with a mic clip and adapter that attaches to both US and European mic stands.
The software, as before, includes two programs, a measurement module which runs standalone (and is now 64 bit only) and a correction module available both in 32 bit and 64 bit versions. As with the previous versions, you start with measurements of your speakers and room. The idea is to make the first measurement at the engineer's position, equidistant from the speakers, then make additional measurements, some closer, some farther from the speakers, and some left and right of the center line. ARC works fine even if you use subwoofers along with your left/right speakers. A minimum of seven measurements is required, although you can make up to 16. Note that ARC not only makes corrections in the frequency domain, but also provides some adjustments in the time domain which helps tame delayed reflections.
The measurement module starts off with a choice of mic, which includes the original two condenser mics and the new MEMS mic. It also has settings for your mic input interface and the audio outputs to your speakers. Next is a level test using quick 20 Hz - 22.5 kH sweeps, which can be painful if run too loudly. IKM suggest using a level for the test signal similar to your normal monitoring level. I found the MEMS mic to be sensitive enough to make measurements with an audio level of about 60 dB SPL (A-weighted), which is not very loud, and ran my tests at about 75 dB, which is a good level for mixing. Although the MEMS mic does not have a published sensitivity spec, my measurements showed it to be about -38 dB (rel 1v/Pa) or about 13mV/Pa, which is typical for a small capsule capacitor mic. The equivalent noise (or “self-noise”) is rated at 29 dB which yields a snr of 65 dB. Not great for recording quiet sources, but as good as many other small diaphragm mics. It requires phantom power, and anything in the range of 12 to 48 volts will work.
After making a set of measurements you are given a window to enter a name for the set - I use three speaker sets in my control room and have named each measurement set appropriately. Here are a couple, with the first being my iconic Yamaha NS10M Studio monitors, which as you can see by the orange and white plots (before and after calibration) roll off rapidly below 100 Hz. ARC actually measures your speakers frequency response and does not try to artificially boost lows or highs, though there is a Full Range Bass Correction mode that will bump up the lowest frequencies as high as possible without over driving the speakers. I leave this turned off myself.
And below is the correction module showing results with my full range system which includes a sub-woofer, and ends up pretty flat (white plot) down to 30 Hz, though room modes had originally caused a few big bumps and dips (orange).
It's easy to switch the correction module to match the speaker set in use. And there are a number of additional settings to "tune" the sound to your liking! You can see under Target Curve I used HR Rolloff 1, which I prefer to a fully flat high end. You can also see I used different graphics for these two speaker systems, a white cone style for the NS10 (although it is not an accurate NS10 image!) and a fancy looking multi-way cabinet for the full range set.
Wait, I Thought ARC Would Perfect My Sound!
As you probably know, even the best, multi-thousand dollar studio monitors from different manufacturers, even different models from the same vendor, all sound a little different. In fact, most monitors have some built-in EQ to compensate for positioning (near a wall, in a corner, etc.) and reviews of high end monitors focus on issues such as the stability of the phantom centre image, stereo positioning and three-dimensional perspective. Expert reviewers make comments like "this is a very self-controlled monitor that always sounds smooth" or "I was very impressed by the level of definition and transient detail that it delivered". It's detail and definition that suffers in a poor room, even with an excellent speaker. But there is no such thing as a perfect speaker, and different people prefer the "tones" of different speakers and different EQ settings.
ARC will help increase detail and definition in a room, but it does not force you to use a particular EQ "tone". You are free to adjust the overall EQ to your liking, or to use one of the built-in target curves which include High Frequency Roll Off, Flat with Mid Compensation, and HF Roll-off with Mid Compensation. There is also a Virtual Monitoring menu with a number of EQ curves covering some small speakers, TV sets, car audio, boom boxes, desktop and laptop speakers. This enables hearing how your mix would sound on a restricted fidelity system, a good way to estimate how well your mixes translate to other systems.
How Does It Work?
In short, very well! The actual processing going on is proprietary, but as other reviewers have noted over the years, whatever it does, ARC does it well. Of course, as many have written before, the first 'project' you should accomplish in a studio space is acoustic treatment. You should apply whatever treatment you can afford to eliminate direct reflections and standing waves. For medium to high frequencies, the three "mirror points" are critical (left, right and ceiling). Bass traps in the corners, and broadband absorbers on walls and on wall-to-ceiling sections will help tame a room. There should also be some "uneven" reflecting surfaces to create diffusion. There are many articles online and in the usual recording technology magazines to help with this. You can spend as little as a few hundred dollars using a DIY approach, or you can spend well over a thousand dollars using commercial 'kits'. But once you’ve tamed the reflections and standing waves to within 5 to 10 dB or so, it will likely cost a lot more to make the room significantly better, especially the bass frequencies. This is where the ARC system can more than pay for itself. In my estimation, ARC 2.5 will deliver a much better result than $200 worth of additional sound control material, and in the case of a small room, no amount of acoustic treatment can fully fix the low end.
ARC is not a substitute for proper acoustic treatment, but unless your room is a large, professionally designed control room, ARC will improve your sonic experience notably.
If you already have ARC 2, getting the free software is a no-brainer. Even using the older ARC 2 mic will result in better correction using the new software. But for $/€70 the new MEMS mic can provide more precise measurements and is a very reasonable deal. And it can be used for other studio duties, on loud sources, after calibrating your room. If you have ARC 1, now is the time to upgrade! ARC 2.5 is vastly improved over version 1.0, and the MEMS mic is also a significant improvement over your original mic, which by now has likely a different frequency response than it did when new.
If you have no ARC system, consider how your room sounds. Are your mixes clear, with tight bass, and no "boxiness" or smearing? If your room is very good already, you may detect only a small improvement using ARC correction (but will likely hear some improvement), but if your room sounds like most "bedroom" studios, you'll likely be amazed at the improvement.
The version 2.5 software update is free to anyone with version 2.x and works with previous ARC mics.
The new MEMS mic is reasonably priced and provides very precise measurements when used with ARC 2.5.
The new MEMS mic can be used for other studio recording activities after studio calibration is completed.
The Virtual Monitoring mode can be useful to audition how mixes might sound on boomboxes and other modest sound systems.
The PDF manual has very good tips on using ARC and is a MUST READ before you make measurements.
For best results the measurement process requires accurate placement of mic in all three dimensions, and can take the better part of an hour to do right. However, the measurement process is needed only once (unless you modify your studio layout or change speakers) and the correction module can be (and should be) used for all subsequent mixing and mastering.
Product Info: IK Multimedia | ARC System 2 with MEMS Microphone
All prices in US dollars and Euros
ARC 2.5 with MEMS Mic is $/€199.99; MEMS Mic alone is $/€69.99
ARC 2.5 software alone is free for ARC 2.x owners.