HOFA Room Mode Calculator
The influence of room modes on your room acoustics
Acoustics have a significant impact on the overall sound quality of a room.
This is especially true in recording studios, home cinemas, and hi-fi listening rooms, where good room acoustics are essential for professional use. Conversely, even the outstanding sound of high-end studio monitors or hi-fi speakers can be severely compromised by poor room acoustics. In untreated rooms, the bass range in particular often sounds unbalanced, muddy, and lacks dynamics. The main cause of this is what are known as room modes.
All sound waves are reflected by the solid boundaries of a room. When these reflections overlap between parallel surfaces, they create unwanted room modes – also known as standing waves.
The good news: the occurrence of these waves can be calculated and specifically addressed using the right acoustic treatment.
How to use the room mode calculator
First, enter the dimensions of your room to calculate its various room modes. Then you can test how your room responds to bass frequencies and how these are perceived at your listening position. To do this, click the small play icon next to the calculated frequencies. Your speaker will then play a sine wave at that frequency, allowing you to hear volume peaks and dips as you move around the room. When you stop playback, you’ll also notice how long the standing wave takes to decay. This prolonged decay caused by the room is exactly what leads to an unbalanced, muddy, and lifeless bass response.
Enter your room dimensions here:
Axial room modes
Axial room modes are the modes with the strongest effect on the sound in a room and at the listening position. They occur between two parallel surfaces – such as opposing walls, or between the floor and the ceiling.
Length
Width
Height
Tangential room modes
Tangential room modes involve four surfaces. They carry only half the energy of axial modes but are still clearly audible and can noticeably affect the frequency response.
Length
Width
Height
Oblique room modes
Oblique room modes have only a quarter of the energy of axial modes, and therefore have less impact on the room’s sound than axial or tangential modes. They involve all six surfaces and primarily originate from interactions across the room’s corners.
Explanation of the effects of room modes
Let’s take the axial room mode with the lowest frequency as an example. Its half wavelength fits exactly between the short walls of the room. This mode causes boosts and dips in volume throughout the space. Near the walls, sound pressure is much higher (indicated in blue and red), while further away from the walls, the pressure is significantly lower. Exactly at the midpoint of the room’s length, sound pressure can be extremely low, or even virtually inaudible.
Each of the calculated modes above causes similar boosts and dips in volume. The higher the frequency, the more pressure peaks and nulls occur throughout the room. At the same time, the mode’s energy decreases with frequency, making it less audible and thus less disruptive.
Now that you’ve identified your room modes, here’s what you can do about them:
1. Positioning of speakers and listening position
The high and low sound pressure zones mentioned above make it essential to carefully choose both the speaker positions and the listening position in order to achieve an accurate bass response. You can do this even in an empty room: set up your desk, laptop, audio interface, and speakers, then play some of your favorite tracks.
If the bass sounds full and powerful, there’s nothing standing in the way of your planned setup. But if it sounds either too weak or overly emphasized and boomy, we recommend experimenting with the placement. Shifting the speakers or the listening position by just 30 to 70 cm can already lead to significant improvements. In some cases, it may even be necessary to rotate the entire setup by 90° to achieve the best possible sound.
Upgrading a 2.0 system to a 2.1 setup by adding a subwoofer can also be highly effective in reducing bass problems. This allows the frequency ranges to be split, giving more flexibility in placing the subwoofer for optimal performance.
These aspects of listening position optimization are also part of HOFA-Akustik’s room acoustics consulting and planning services.
2. Using HOFA Basstraps
While proper positioning of the listening spot and speakers already helps significantly in minimizing the impact of disturbing room modes, this measure alone is usually not sufficient for a fully satisfying acoustic result.
To further improve the reverberation time and overall sound quality, additional acoustic treatment is necessary. In the bass range and for reducing room modes, HOFA Basstraps are particularly effective, as they primarily absorb low frequencies. For optimal performance, basstraps should be placed at pressure maxima-locations where the problematic frequencies are most prominent.
We would be happy to create a custom acoustic plan for your room and calculate the amount of basstraps and acoustic modules you need to achieve optimal sound.
