Mastering the RTA in Smaart v9: Beyond the “Bouncing Bars”
The Real-Time Analyser (RTA) is one of the most powerful yet frequently misunderstood tools in a sound engineer’s arsenal. At first glance, it appears deceptively simple, just a set of bouncing bars showing frequency content. But the data displayed is the result of sophisticated mathematical processing and deliberate trade-offs. To truly harness its potential, you need to understand and control key settings like banding, averaging, and underlying parameters such as FFT size.
Understanding Bandwidth: Fractional-Octave Banding
In Smaart v9, “bandwidth” in the RTA context refers to the fractional-octave banding resolution, which determines how the spectrum is grouped and displayed for easier interpretation.
- Smaart v9 offers resolutions ranging from full octave (1/1) down to an ultra-fine 1/48th octave, the highest available in the platform, delivering exceptional detail.
- Common options include 1/1, 1/3, 1/6, 1/12, 1/24, and 1/48 octave.
- How it works: Banding sums the energy (power) within defined bands centered on standard fractional-octave frequencies. This produces a smoother, perceptually relevant curve that better aligns with human hearing, wider bands in the lows, narrower in the highs.
Banding is a display mechanism distinct from smoothing (primarily used on transfer function magnitude and phase traces, where it averages dB values in overlapping octaves). You can adjust banding directly in the RTA plot controls or spectrum settings, and it applies to live traces, captured data, and spectrographs.
Higher resolutions (e.g., 1/48th octave) reveal fine details but can look noisier due to less inherent averaging. Lower resolutions (e.g., 1/3 octave) yield smoother traces, ideal for rapid system tuning or comparing against target curves.
The foundation of this display is the FFT size: Larger FFTs (e.g., 64k) provide narrower frequency bin resolution (calculated as sample rate ÷ FFT size), giving more raw data for banding to work with.
The Power of Averaging
Averaging acts as your “statistics filter,” stabilizing the display against rapid fluctuations and noise.
Smaart v9 provides progressive averaging from 0, none to 1–10 (plus Infinite):
- Lower settings (more responsive) are prone to noise and instability.
- Higher settings offer greater stability and noise rejection but reduced responsiveness.
Specifically:
- Settings 1–3 use FIFO (first-in, first-out) averaging.
- Settings 4–10 employ variable weighted averaging with frequency-dependent time constants. Shorter in high frequencies, longer in lows (following an S-curve).
This clever design makes the trace feel more intuitive, like smoothly turning a knob, while maintaining quick response in the highs and steady behavior in the lows. The default of “6” strikes an excellent balance for most scenarios. Adjust up or down based on whether you prioritize stability or immediacy.
Smaart also supports live averaging across multiple RTA engines, enabling spatial averaging (e.g., from several microphones positioned around the venue).
Decoupling Your Ears from the Screen
Remember: The RTA measures Sound Pressure Level (SPL) objectively, but it doesn’t “hear” like humans. Psychoacoustics play a huge role. A massive low-frequency peak (e.g., at 60 Hz) might look alarming on screen but could provide the desirable “weight” and impact audiences expect in a large venue. Always use the RTA to identify anomalies, then trust your ears to determine if they’re truly problematic.
Adding the Time Dimension: The Spectrograph
If the RTA is a static snapshot of the spectrum, the Spectrograph is a dynamic “movie.” It introduces time as the z-axis, revealing how frequencies evolve and decay over time.
For instance, a snare drum hit might produce a lingering horizontal streak at 200 Hz lasting 500 ms. Clear evidence of resonance that a standalone RTA could miss or underrepresent.
Pro Workflow Tip
For everyday system alignment and troubleshooting, try this setup: 1/24th octave banding on the RTA with a moderate FIFO average (e.g., around 2–3 seconds for responsiveness). Run the Spectrograph underneath for temporal context. This combination delivers high-resolution frequency insight while keeping an eye on how issues persist over time, striking the perfect balance for efficient, informed decisions.
You can also combine TF (transfer function measurements and RTA windows in one screen.
Smaart is excellent on its own, but most users find they get much more out of it after some structured training. That’s where our seminars come in. At TZ Audio we run practical seminars, both online and in-venue. We offer seminar-only or full “all you need packages” including software & hardware. It’s simply the fastest way to become comfortable and confident with the measuring a sound system.
If you’re in Norway, Sweden, Denmark or Iceland – or elsewhere – we offer is online seminars and traveling to Norway is a valid option too of course. We’re here if you have any questions about the software or upcoming seminars.
Thanks for reading!