2026-07-29 · Measurement
What a room does to the bottom two octaves
A speaker measured on a stand outdoors and the same speaker measured in your kitchen are not the same speaker. Below about 200 Hz the room is louder than the driver.
Every speaker specification you have ever read was measured in a room that is not yours, and above roughly 200 Hz that is mostly fine. Below it, the room stops being a container and becomes part of the instrument.
Why the bottom is the room’s
Long wavelengths do not care about the cabinet. A 40 Hz tone is about eight and a half metres from crest to crest, which is longer than most rooms, so what you hear at that frequency is the sum of the driver and every surface the sound has already bounced off. Two identical speakers a metre apart can measure ten decibels apart at the same note because one of them is nearer a corner.
That is not a defect and it cannot be engineered out of the cabinet. It can only be measured where you sit.
What the sweep actually does
Set-up plays a sweep from the listening seat and compares what arrives with what was sent. The difference is the room. The correction that comes out of it is stored on the speaker rather than in an app, which matters more than it sounds: it survives a new phone, a new router, a firmware update and a house move.
- It corrects level, not timing artefacts it cannot hear.
- It does not touch anything above the range where the room dominates.
- It is re-run in a minute if you move the speaker, and you should.
The part people expect and do not get
A correction cannot add bass a room refuses to make. If a null falls exactly at the listening seat, the honest fix is to move the speaker or the seat by half a metre, and set-up will say so rather than pushing forty watts into a frequency the room is cancelling.
That is the whole argument for measuring at all: not to flatten a curve, but to know which problems are worth solving with electronics and which ones are furniture.
