IK Multimedia ARC System by Sound-Guy
IK Multimedia ARC System 3
As previously reviewed on Gearslutz, IK Multimedia ARC is a software based room correction system that was last updated in 2017 with new software and a new impressive MEMS solid-state microphone. Spring of 2020 saw the release of ARC System 3 which can still use the MEMS mic, but introduces a totally new analysis program using a new measurement approach that can use any calibrated measurement microphone. Since I have four such mics, I was eager to check it out.
As before you get an analysis program to use with a measurement mic and the correction plug-in to use for playback in your DAW or other audio program. The measurement program has been totally changed and now “steps” you through the procedure, from mic selection to specifying your audio interface to indicating your listening environment. And the measurement process is new – you always make the same number of measurements (21) and you make them in three dimensions!
What Is System 3?
As with ARC 2.5, ARC System 3 (ARC 3) can be purchased with the MEMS mic or as software only. The big difference is that you have more choices of mics to use with the new analysis software – you can use the MEMS mic if you have one, use either of the previous two ARC condenser mics, or any RTA measurement mic that you have. You can even use the calibration file supplied with a good measurement mic to get the best measurement accuracy. I checked this out with two of my mics and it worked fine. BTW, a calibrated measurement mic is not one of your studio mics! It is a small capsule omni-directional microphone specifically designed for room measurement and there are good models available for well under $100 (and great ones for over $1,000!). Suggestions I’ve read saying you can use a studio mic like an AKG C414 set to omni are fine if you don’t care about erroneous peaks and dips as large as 8 to12 dB!
Measuring the Room
After mic and interface set-up you specify the listening environment from a choice of five rooms, project studio to home theater. Then you begin the measurements starting with the mic at the center location, but with it lowered about 6 inches (15 cm) below nominal “sitting” ear-height. Each measurement location is shown graphically in the analysis window with a ‘Capture Point’ button used to start each test. You make seven measurements at this height starting at the center location and symmetrically on the left and right. Then the program tells you to raise the mic up to ear height and run the same locations again. Finally it tells you to move the mic up another 6 inches and make the last seven measurements.
I was pleased that the measurements do not just start running automatically, forcing you to move quickly. You can carefully position the mic at each location, click the “Capture Point” button, and then have a few seconds to get out of the way before the test signals start. Another great feature is that the analysis window can be resized up to your full video monitor width making it easy to see the text and graphics from behind a mic stand. And I was also happy to see that IKM stress the need to get out of the way when measurements are made – the manual states “Try to use a mic stand with a boom arm that is extended as far away from the stand as possible. This helps avoid reflections from the stand that will interfere with the analysis at high frequencies. Do not stand or sit near the microphone while the analysis are running.”
This is very important since your body will distort measurements, especially at mid to high frequencies (I’ve measured 6-10 dB changes standing or sitting in different locations within a foot or two of a measurement mic). You should not sit in your listening position, odd as that may seem, and the best location is directly behind the mic, low to the floor. One audio engineer has even said it’s best if you can leave the room during measurements, which is not really practical! I crouch low directly behind the mic stand as each measurement is made, always in the same location, and use a mic boom oriented horizontally with the mic body parallel to the boom and aimed over the chair back, facing toward the front. This allows moving the mic side to side by swinging the boom and forward and back by sliding the boom. And I can slide the mic column up and down for the high and low measurement “layers”.
Measurement spacing depends on the chosen listening area and while IKM do not specify actual horizontal locations, the graphic shown for each listening area gives you an idea of useful positions. I checked with IKM and found the measurement system works out the actual locations from signal timing, so the graphic view is only a guideline and you can select positions that make sense for your room use, just be sure the first measurement at each level is centered equally from each speaker (I check only this first position with a tape measure) and that the following measurements are close to symmetrical around the center location and made in the same order at each of the three levels.
Note that the tighter the grouping you use for measurements, the more precise the monitoring system will perform in that area. If you have a small project studio and are the sole operator, use a tight pattern with mics moved only a foot (30 cm) or so around the center point. If you need to cover a larger area, the response will be more “averaged” and correction in a single spot less precise and less linear.
After measurements are made you name the calibration file and can choose a speaker graphic – IKM have cleverly provided images for a couple of their actual monitor speakers along with several well known models from other manufacturers, but the image is just a visual key to your calibration and has no effect on the correction.
Ready to Play!
Just as the measurement module is a totally new design, the ARC plug-in looks a little different and is functionally very different from earlier versions. Note that ARC 3 calibration files do not work with any previous versions and the ARC 3 plug-in can use only files made with the ARC 3 measurement program. However, both versions of ARC can coexist on your computer at the same time so you can keep ARC 2.5 (or earlier) if you like, but I’d bet you’ll go forward using ARC 3.
The new plug-in has two modes, Play and Edit. As the screen-shot shows, Play is similar to previous ARC main screens listing the Measurement file used, the Target profile (flat and four custom curves), and Virtual Monitoring selection (Off being the choice for full speaker correction). Virtual Monitoring has been expanded to 14 playback system emulations including IKM’s own iLoud Micro, iLoud MTM, an NS-10, and some Adam and Genelec speakers (indicated with hints rather than actual names!). Virtual Monitoring includes nine speakers plus a “boxy” car stereo, two TV’s, a laptop computer, and even a smart phone! These are very useful for auditioning mixes as they would sound in some extremely different listening environments.
Play mode also shows the measured and corrected frequency plots, the filter phase control (Natural or Linear), and the metering panel with choice of Peak, RMS, or a new LUFS/Dynamic Range display that should be very useful. Metering can still be viewed either pre or post processing which is crucial to assuring true peak levels of the input signal don’t exceed 0 dBFS (actually should be -1 dBFS or so, but that’s a whole topic in itself). There is a Correction on/off button, an RTA switch to show the new real-time spectrum plot, and a Trim control. I found that ARC 3 provides automatic loudness compensation when you compare sound with ARC correction on or off. The Trim control is to prevent your amp/speakers/audio interface from pushing sounds into distortion since, if your room has large dips, ARC will increase gain at those frequencies which could lead to trouble. The plug-in detects the maximum boost level in the correction filter and automatically sets the Trim control to compensate, but you can change this setting as you wish (I found in my studio I can safely set it to full output which keeps my monitor reference level calibration intact). ARC 3 itself will not clip or distort even if its output exceeds full scale by 24 dB (plenty of bits used in processing). Use good speaker loudness calibration and you should have plenty of headroom even with Trim at maximum.
The other main screen is Edit which includes the Target profile window and the same plots and lower controls as the Play panel, but the frequency plot now includes six “handles” that can be used to modify the overall response (which can be saved as custom targets). This may seem at odds with “flattening” your room, but as many acousticians and audio engineers will tell you, Fletcher-Munson is out to fool you unless you mix at high (and dangerous) levels. If you don’t know these guys (Fletcher and Munson) or the newer ISO 226:2003 standard for loudness versus frequency response, you should look it up. Using a smooth rise below about 200 Hz, up 6-8 dB at 20-40 Hz (your lowest reproducible frequency) will enable hearing low bass at safe listening levels (76-80 dBA is often suggested as an average level for a small room).
The Edit screen also has a button to combine the left and right corrections into one (only needed in a terribly asymmetrical room) and Low Range/High Range controls to limit the frequency range of the correction which is helpful if you want to maintain some of the speaker’s mid or upper frequency voicing or if ARC tries to boost the bass level of a small speaker too much (hopefully you’ll not need either of these controls). And at the right side is a resolution control (Correction Type – Default, Broad or Sharp) which affects how smooth the correction curve is – the broad setting does not apply precise correction, but the audible effect from broad to sharp is subtle, demonstrating that our hearing is not as keen as an RTA mic and spectrum analyzer!
Is ARC 3 a Better ARC?
I compared ARC 3 to ARC 2.5 with a quick listening test and the results were similar, but I heard a noticeable improvement with ARC 3 on vocals, which were clearer and more focused. With ARC 2.5 (and more so with no correction) listening to a vocal, or any phantom image center signal, and moving my head a little side-to-side results in a "phasey" effect in the mid and high frequencies. This is likely comb-filtering of residual room reflections varying a little at each ear. And even sitting still this effect “blurs” the sound some. More critical listening found this improved “focus” applies across the full stereo field. ARC 3 sounds more "natural" than my previous versions and much, much better than my room without using ARC correction. It provides better focus and better depth to the sound stage than I’ve ever heard in my room.
The new 3-D measurement procedure process is easier to perform than previous methods, even though it requires a few more measurements than the maximum of ARC 2.5, and the results are a more detailed acoustic “map” of your room/speaker system. This and the added features like frequency range control, correction type, and enhanced metering make ARC 3 a major improvement over the already fine ARC 2.5 version.
ARC 3 can significantly improve a moderately treated room and make a well controlled room sound excellent, improving clarity and stereo imaging. While IKM marketing folks can honestly say “ARC System 3 improves frequency balance and stereo imaging in any room”, it is always best to first put what you can afford into room treatment – if you are reading this article you already know that! And you likely have found that trying to control the lowest few octaves is not the least bit easy! This is where ARC can really deliver. If you already have basic treatment in place, for the price of the ARC System 3 you won’t get as much improvement from additional physical room treatment, especially below a kilohertz or so.
If you already have a good calibrated measurement mic or have ARC 2.5 with the MEMS mic, you can get the software alone (and with a good discount for previous ARC versions). Otherwise ARC System 3 with the MEMS mic is an excellent investment. Highly recommended!
New easy to follow, comprehensive 3-D measurement process provides excellent, natural sounding correction
New controls like Range, Phase, and Correction Type expand adjustability
New real-time spectrum can be viewed on the frequency plot
Virtual Monitoring provides 14 difference “playback systems” to evaluate mixes in a range of simulated environments
Automated Trim prevents clipping in your audio interface, with user control over the final level
Enhanced pre and post process metering with Peak, RMS, or LUFS/DR readings
Can be used with any good measurement mic, and can even use a calibration file for the most accurate results
Excellent PDF manual and step-by-step measurement instructions
None I can determine