RTA Sweep SPLs Read Differently than Real World Content Measurments - Why?

[acconstantinescu]

Recently I got a new AVR that came with Dirac Live. I've been playing with different tunes and I still have to find one that I really like. Anyway, a few days ago i remembered that I could actually look at the frequencies I may be missing due to the tune, the room characteristics, etc in real time. So I recorded a fight scene in the latest Godzilla & Kong movie using the RTA tool. This is what I got. The yellow line is the sweep did before using the same settings and volume, the red line is the maximum measured by RTA during the fight scene and the black line is the last reading before I stopped RTA. What I found really weird is the very low SPL values at high frequencies. The maximum of 84db at 30Hz is consistent with the SPL meter that didn't cross 90db during the entire scene (I like to listen to about 60db dialogue).

So, does the RTA reading make sense to you? Am I doing something obviously wrong?

I used a UMIK-1 on a Windows 11 laptop with REW V5.40 Beta 65.

 

[John Mulcahy]

You may be confusing a sweep measurement, which measures a system's transfer function (how it changes signals that pass through it), with an RTA measurement, which measures the energy distribution of the signal that was captured. Most content has little high frequency energy as high frequency content generally has very short durations. There's more on that in the REW help: Signals and measurements.

 

[acconstantinescu]

You may be confusing a sweep measurement, which measures a system's transfer function (how it changes signals that pass through it), with an RTA measurement, which measures the energy distribution of the signal that was captured. Most content has little high frequency energy as high frequency content generally has very short durations. There's more on that in the REW help: Signals and measurements.

Is there any way I i can get the equivalent of the sweep measurement but live, while I'm watching a movie? Like the SPL meter but as a function of freq?

When I watch action scenes, sometimes certain explosions sound not that great. I'd like to see what kind of reading my mic gets. Is it just my ear that doesn't catch certain frequencies? Is my seating position? The perceived lack of loudness happens at low frequencies or even above the sub crossover? That's what I'm trying to figure out.

 

[John Mulcahy]

Sweep measurements show how the system behaves when it tries to reproduce any signal. If you think there's a problem with the soundtrack you can't tell that by looking at what a mic picks up as you can't distinguish between the soundtrack and what your system is doing to it.

 

[ddude003]

@acconstantinescu you might ask @Todd Anderson what spectrogram tools he uses for his Bass Hunter series here on AVNirvana... Maybe that might give you some insight into your issues...

Thread 'Bass Hunters 1: Gear and Methods'

Nov 5, 2022

In this episode of Bass Hunters, we introduce the gear and methods used in our hunt for reference-grade, demo-worthy bass. Future episodes will focus on specific movies, head-to-head comparisons, and other bass topics!

**To learn about the theater system and software used in Bass Hunters, including gear made by @Kaleidescape, Inc. @StormAudio @SVS Sound R|Evolution @Power Sound Audio @Power Sound Audio @Emotiva Audio Seymour Screen Excellence, and JVC, watch the video below.

**To read a full review of...

• Todd Anderson
• Replies: 0
• Forum: Bass Hunters