Measuring Your Room with REW (Room EQ Wizard)
Home studio acoustics is not something you can fix by guesswork.
If Episode 1 was about choosing the right room, Episode 2 is about understanding what is actually happening inside your room — and for that we need measurements.
The tool I will be using throughout this entire series is REW (Room EQ Wizard).
It is free, incredibly powerful, and widely used by both home studio producers and professional acoustic engineers.
What is REW and Why It Matters
REW (Room EQ Wizard) is a measurement software that allows you to analyze how your speakers behave inside your room.
And this is an important distinction:
We are not measuring the speakers themselves —
we are measuring the speakers inside the acoustic environment of the room.
This includes:
• room modes
• reflections
• frequency response
• time behaviour of sound
Understanding this is the foundation of good home studio acoustics.
Measurement Basics
To measure your room with REW, you need:
• a measurement microphone (e.g. Earthworks, UMIK-1)
• a calibration file for the microphone
• your speakers
• your listening position
The basic process is simple:
REW sends a frequency sweep from around 20 Hz to 20 kHz through your speakers.
The microphone captures how that signal behaves inside your room.
From that, REW generates a frequency response curve.
What Are We Measuring?
There are two main types of measurements we are interested in.
1. Frequency Response
This shows how balanced your speakers sound in your room.
You will typically see:
• peaks (too loud frequencies)
• dips (missing frequencies)
Most of these issues come from room acoustics, not the speakers themselves.
2. SPL (Sound Pressure Level)
This measures loudness.
It helps you:
• calibrate your listening level
• ensure consistent monitoring conditions
Understanding a Measurement
In REW, you typically measure:
• left speaker
• right speaker
• both speakers together
This gives you a clear overview of how your system behaves.
For example:
• red curve → both speakers
• green → left speaker
• blue → right speaker
This allows you to identify imbalances between speakers and room interaction.
The Most Important Insight
One of the most important things I learned:
We are not fixing the entire frequency spectrum.
We focus mainly on:
20 Hz – 300 Hz
Why?
Because this is where:
• room modes exist
• the biggest problems occur
• acoustic treatment has the biggest impact
Everything above that is heavily influenced by:
• listening position
• reflections
• small movements
Trying to “EQ” the entire spectrum often leads to unnatural results.
Using REW’s EQ Feature
One of the most powerful features in REW is the EQ section.
After a measurement, REW can generate:
• a target curve
• suggested EQ filters
• a predicted corrected response
This allows you to linearize your system.
You can then export these EQ settings and use them in:
• DSP software
• monitor calibration tools
• TotalMix (RME)
Important: Don’t Over-Correct
This is where many people make mistakes.
REW might suggest very aggressive EQ moves, for example:
• -10 dB
• -15 dB
While mathematically correct, this can cause:
• phase issues
• unnatural sound
• overprocessed monitoring
In practice, I recommend:
👉 Use about 60–70% of the suggested correction
Always trust your ears.
REW Room Simulator
In Episode 1 we used the Room Simulator.
This is another powerful feature inside REW.
You can enter:
• room dimensions
• speaker position
• listening position
REW then predicts:
• modal distribution
• frequency response
This helps you understand your room before even placing treatment.
Speaker & Listening Position
REW also helps visualize how positioning affects sound.
When you move:
• speakers
• listening position
You will notice:
• big changes in mid frequencies
• smaller changes in low frequencies
Important insight:
👉 Room modes stay roughly the same
👉 Position mainly affects how you experience them
Waterfall Diagram – Time Matters
One of the most important tools in REW is the waterfall diagram.
This shows not only frequency, but also time behaviour.
Sound is not just amplitude — it exists over time.
In the waterfall plot you can see:
• how long frequencies decay
• which frequencies “ring” in the room
Room modes are not only a frequency problem —
👉 they are also a time problem
Low frequencies can:
• build up
• continue oscillating
• smear your perception of bass
This is why bass traps are essential.
Why REW is Essential
REW gives you something incredibly important:
👉 clarity
Instead of guessing, you can:
• measure your room
• understand problems
• make informed decisions
This is the foundation of professional home studio acoustics.
What Comes Next – Episode 3
In the next episode we will go deeper into:
• microphone placement
• how to properly measure your room
• SPL calibration
• real-world measurement workflow
We will turn theory into practice.
Watch the Episode
👉 https://www.youtube.com/@phable
Key Takeaways
• REW is an essential tool for home studio acoustics
• Always measure speakers inside the room
• Focus on 20–300 Hz for acoustic problems
• Avoid over-correcting with EQ
• Room modes affect both frequency and time
• Use measurements to guide treatment decisions
Frequently Asked Questions
What is REW used for?
REW is used to measure and analyze room acoustics, including frequency response, room modes, and decay behaviour.
Do I need a measurement microphone?
Yes. A calibrated measurement microphone ensures accurate results.
Should I EQ my entire frequency response?
No. Focus mainly on low frequencies (20–300 Hz). Over-correction can harm sound quality.
What is a waterfall diagram?
It is a 3D visualization showing how frequencies decay over time, helping identify ringing and modal issues.