Wall of Bass: Taming Room Modes with a Studio Bass Array Installation

#Acoustics#Studio Design#Bass Array#Subwoofer#Room Modes#DIY#Studio Build

Achieving accurate and consistent low-frequency reproduction is one of the biggest challenges in studio design. Room modes – resonances caused by bass waves reflecting off walls, floors, and ceilings – create peaks and nulls that drastically change the perceived bass response depending on where you sit. This problem is amplified in smaller rooms or when needing consistent sound across multiple listening positions.

Recently, I faced these exact challenges while designing a studio for Finnish artist Osmo Ikonen. The space was relatively small, needed to accommodate many instruments (leaving little room for bulky traditional bass traps), and required good listening conditions at several spots. Our solution? A “Wall of Bass” – implementing a bass array system.

See the installation and results in the video below:

This post delves into the concept and the real-world results.

The Problem: Room Modes and Spherical Waves

A single subwoofer radiates sound more or less spherically. In a typical room, these bass waves bounce off all surfaces, interfering with each other and creating complex patterns of high and low pressure zones – the room modes. This means moving your head just slightly can result in hearing significantly more or less bass at certain frequencies. Traditional solutions involve massive amounts of porous absorption (bass traps), which consume valuable space.

The Solution: Bass Array and Plane Waves

A bass array tackles the problem differently. By installing multiple, evenly spaced subwoofers across a large surface (typically the front wall), the system works collectively to generate a plane wave that travels down the length of the room, rather than a spherical wave expanding in all directions.

The key benefit? A theoretically perfect plane wave has a consistent frequency response at any point along its path. While perfection isn’t achievable in reality, this approach dramatically reduces the spatial variation caused by room modes interacting perpendicular to the array’s surface. It promotes bass consistency across a much wider listening area.

This system has an upper frequency limit, above which it no longer behaves as a coherent plane wave source. This limit is determined by the spacing between the subwoofers (specifically, half the wavelength of the largest distance between adjacent subs). In this project, the limit was around 120 Hz.

The Osmo Ikonen Studio Installation

For Osmo’s studio, we implemented the bass array on the front wall:

  • Drivers: Multiple 10-inch Focal car subwoofers were used. (I use similar drivers in my own studio, capable of reaching 20 Hz).
  • Enclosures: Each sub was housed in a sealed enclosure of approximately 30 liters (1 cubic foot).
  • Placement: The enclosures were mounted in an evenly spaced grid across the front wall.
  • Concealment: To maintain aesthetics, the entire array was hidden behind a custom-built “false wall” with slots carefully designed not to impede the low-frequency energy.

Measurement Results: Proof of Concept

The results were measured before extensive mid/high frequency acoustic treatment was finalized, focusing purely on the low-end performance. Measurements were taken from three slightly different positions around the main mixing spot:

  • Main Speaker Alone (20-100 Hz): As expected, measurements showed significant differences between the three positions, clearly illustrating the impact of room modes on a single sound source.
  • Bass Array Alone (20-120 Hz): In stark contrast, the measurements from the bass array were remarkably consistent across all three positions. Despite non-ideal room conditions (non-rigid walls, studio gear already present), the array delivered exceptionally uniform bass response within its operating range.

Even as the designer, I was impressed by how effectively the array controlled the low-end spatial variation.

The Next Level: Double Bass Array (DBA)

There’s an even more advanced configuration called a Double Bass Array (DBA). This involves installing a second, identical array on the opposing (rear) wall. This rear array is driven with inverted polarity and carefully calculated delay. It essentially functions as an active bass trap, absorbing the plane wave generated by the front array when it reaches the back wall. This cancels the dominant front-to-back axial mode, leading to even smoother decay times and response. You can read more about it on Wikipedia. Perhaps a future project!

Conclusion

The “Wall of Bass” array proved to be an incredibly effective solution for achieving consistent, high-quality low-frequency reproduction in a challenging studio environment. By generating a more controlled plane wave, it drastically minimized the spatial inconsistencies caused by room modes, providing a solid bass foundation across multiple listening positions without requiring excessive amounts of passive acoustic treatment. It’s a powerful technique to consider for critical listening spaces.