First Reflection Point Calculator

Room, Speaker and Listening Information

Find Reflection Points

Top View — Side Wall Reflection

Side View — Ceiling Reflection

Results

Why does delay matter? The effect of reflected sound depends entirely on how much later it arrives compared to direct sound — and both very short and very long delays are problematic:

• Below 1 ms: Overlaps with direct sound causing comb filtering, certain frequencies cancel out — tonal color degrades. This is the most damaging region.
• 1–15 ms: Due to precedence effect (Haas), it is not perceived as a separate sound and the source direction is still correctly localized. However, the reflection mixes with direct sound blurring the stereo image and making instrument positions unclear. This is the interval treated first in studio design.
• 15–40 ms: Can add sense of spaciousness and envelopment without degrading source localization. Completely eliminating reflections in this range can make the room feel dead and artificial.
• Above 40 ms: Now perceived as a separate event — echo — and degrades clarity. However, reaching this delay requires the reflected sound to travel approximately 15 meters more than direct sound; first reflections in home-sized rooms physically cannot reach this threshold. For this reason, the real battle in homes is against the first two ranges.

Delay alone is not sufficient: The intensity of reflection is equally important as its delay. Reflection from the far wall travels a longer path so it arrives both later and weaker due to distance; also, due to the speaker's off-axis radiation character it is typically at lower level. Therefore, far-wall reflection is generally less problematic than near-wall reflection. Furthermore, Floyd Toole's research shows that in home environments, complete elimination of side-wall reflections does not always yield the best result; a measured approach can produce more natural outcomes — this topic remains debated in the acoustics community.

How to find it (you can reach the same result manually): Slide a flat mirror along the wall at ear level; the point where you see the speaker driver directly reflected in the mirror is the first reflection point on that wall. This tool calculates the same result using the mirror-source method based on the principle "angle of reflection equals angle of incidence" (Snell).

If you wish to convert the distances you found to wavelengths: Sound Wavelength Calculator →