Stereo RMS Combined RMS

[musicainbasso]

What is the difference between the stereo rms and combined rms options that I see in the Master Meter settings. I asked AI and they told me this:
The difference between **Stereo RMS** and **Combined RMS** lies in how they calculate the **average level** of a stereo audio signal:

---

### **1. Stereo RMS**
- Measures the **Left (L)** and **Right (R)** channels **independently**, giving two separate RMS values.
- **Use Case**:
- Detecting stereo imbalances (e.g., a panned instrument louder in one channel).
- Mixing adjustments (e.g., fixing uneven bass distribution).

### **2. Combined RMS**
- Merges the L and R channels **into a single mono signal** before calculating RMS.
- **Use Case**:
- Loudness metering (e.g., LUFS in mastering).
- Compliance with broadcast/streaming standards (e.g., Spotify’s -14 LUFS).
---

### **Key Differences**
| Aspect | Stereo RMS | Combined RMS |
|-------------------|-------------------------------------|---------------------------------------|
| **Output** | Two values (L and R) | One averaged value |
| **Stereo Info** | Preserves panning/balance details | Ignores stereo separation |
| **Typical Use** | Mixing, diagnostics | Mastering, loudness normalization |

---

### **Practical Example**
- A song has:
- Left RMS = -12 dB
- Right RMS = -16 dB (due to a hard-panned guitar).
- **Stereo RMS**: Shows the imbalance (-12 dB vs. -16 dB).
- **Combined RMS**: Reports **≈ -13.3 dB** (the "average loudness").

---

### **When to Use Which?**
- **Stereo RMS**:
- Fixing mix issues (e.g., "Why does my left speaker sound louder?").
- **Combined RMS**:
- Preparing for streaming (e.g., checking if your track hits -14 LUFS).

**Note**: Modern loudness meters (like LUFS) use a **weighted** version of Combined RMS to account for human hearing perception.

Is everything correct?
Thanks!!!

[Hugh Robjohns]

Sounds plausible to me.

[musicainbasso]

Sounds plausible to me.

Ok thanks! I'm trying to learn the deep and difficult world of Meter Levels (RMS, LUFS, Peak, True Peak....) that is very difficult to me!

[Drew Stephenson]

This article from Hugh gives a pretty comprehensive take on metering: https://www.soundonsound.com/sound-advice/metering
I think there's been a more recent update too with a nice graphic showing how the different scales align but I can't seem to find that one at the moment.

[Hugh Robjohns]

This one?

[Drew Stephenson]

That's the one.

[musicainbasso]

This article from Hugh gives a pretty comprehensive take on metering: https://www.soundonsound.com/sound-advice/metering
I think there's been a more recent update too with a nice graphic showing how the different scales align but I can't seem to find that one at the moment.

Yes I read it! It's good. Thanks

[musicainbasso]

This one?
Audio Meter Scales TWEAKED HR 2013.jpg

Oh great!!! Thanks