Floor & Ceiling Bounce, and how to deal with it

When sound travels from your speakers, it bounces off nearby surfaces. Reflections from the floor and ceiling, in particular, can significantly impact the overall sound you hear. These reflections arrive slightly later than the direct sound from the speaker, creating a phenomenon known as comb filtering.

Comb filtering essentially adds and subtracts certain frequencies at specific points in the listening area. This can lead to uneven tonal balance, with some frequencies being boosted and others being cancelled out.

How Directivity Affects the Bounce

The way a speaker distributes sound (directivity) plays a big role in how susceptible it is to floor and ceiling bounce.

Speakers with narrow vertical dispersion tend to excite less the rebound, minimizing the impact of reflections from above and below.

Total Early Reflection (TER) and the Room Equation

While speaker manufacturers typically provide a frequency response curve showing a speaker’s output at different frequencies, this is usually measured in an anechoic chamber – a special environment designed to absorb sound reflections. In a real room, reflections from the floor, ceiling, and walls significantly impact the sound you hear.

Total Early Reflection (TER) is a crucial concept that helps us understand this real-world sound experience. TER specifically measures the combined effect of the first reflections that arrive at the listening position after bouncing off nearby surfaces. These early reflections can significantly alter the tonal balance and overall clarity of the sound.

Evolutionary Adaptation and the Human Auditory System

Interestingly, our brains have likely adapted to compensate for the effects of room acoustics to some extent. For millennia, since the days of Homo sapiens living in caves, our auditory systems have been processing sound in environments with reflections.

This means our brains may be able to partially “correct” for some of the coloration caused by floor and ceiling bounce.

Crossover Design and Minimizing Interference

Another factor to consider is speaker crossover design. A crossover is a circuit that divides the audio signal into different frequency ranges and directs them to the appropriate speaker drivers (woofer, tweeter, etc.).

When the crossover frequencies are close to the resonant frequencies caused by floor bounce, it can be use, by looking power response, to diluate the bounce effect by taking account in crossover design.

Imagine two drivers in a speaker – one positioned higher and one positioned lower. If they are reproducing similar frequencies at the same time, but one is slightly delayed due to its distance from the floor (floor bounce), they can interfere with bounce effect differently.

Crossover design can plays a role in minimizing the impact of floor bounce. While the height difference between drivers can cause slight phase delays, a well-designed crossover can address this. By analyzing the power response, the crossover can be designed to “dilute” the bounce effect, reducing unwanted reflections but it shouldn’nt be done at the expense of putting mid-woofer/woofer as close at possible of tweeter section.

Taming the Bounce: Achieving Optimal Listening

By understanding the effects of floor and ceiling reflections, directivity, power response, and even our own evolutionary adaptations, we can achieve a more balanced and enjoyable listening experience in any room. Here are some tips:

• Speaker placement: Experiment with speaker positioning relative to the walls and your listening area. Even a few inches can make a difference.

• Room treatments: Consider acoustic panels or diffusers to absorb or scatter sound reflections, especially if your room has hard, reflective surfaces.

• Understanding crossover design: While not directly controllable by the listener, being aware of how crossover design can minimize interference due to floor bounce can be helpful when choosing speakers but it must not be done on the depend of the point below.

• Lower crossover frequency: As mentioned earlier, a lower crossover encourages the woofer to handle a wider range of frequencies at lower wavelengths. This promotes better directivity at the lower frequencies most susceptible to floor bounce, reducing the overall energy bouncing around the room.

• Narrower vertical dispersion: Speakers with wider vertical dispersion spread the sound out more, which can actually increase reflections off the floor and ceiling. Conversely, speakers with narrower vertical dispersion tend to focus the sound more towards the listening area, minimizing the interaction with reflective surfaces above and below. It’s one of the raison that the coverage should be choosen according to listening distance and acoustic.