Room size and bass

Dave from Cheltenham writes:

I came across a comment on an audio website recently that said something to the effect that a small room or a large room will reduce bass response from speakers. I have a pair of Tannoy Arden speakers (15″ dual concentrics) in a large room, 4.5m W 11.5m L and 3.9m H and the bass response does seem to be rather less than in some other smaller spaces they’ve occupied in other houses. Are you able to shed any light on this for me

I haven’t done any rigorous work on this issue, but I suspect that these kind of claims — which have been around as long as I’ve been interested in the game (thirty-odd years) — are overblown and somewhat of a misinterpretation of what happens.

In fact, unless one is outside or in a huge room (some kind of indoor stadium), the major problem with bass is a lumpy response due to constructive and destructive interference. The reason I say ‘huge’ becomes obvious when you consider the wavelengths of bass frequencies. At 20C, a 40 hertz tone has a wavelength of around 8.6 metres. At 20 hertz, it is 17.2 metres. At these kinds of frequencies the wave will have bounced from several surfaces before even producing a full cycle!

In most modern homes, even large dimensions in a listening room don’t solve these problems because few have ceiling heights much more than 2.5 metres (although you have a wonderfully high ceiling, I see).

The bass performance of any speakers will vary according to the various dimensions which determine which frequencies are subject to destructive and constructive interference. The relevant dimensions are the distances between the major surfaces (walls, ceiling and floor), the distances between the speakers and the surfaces, and the distances between the listening position and the surfaces and speakers. The best bet is trying to make sure that none of those distances are whole multiples of any of the other distances … but then we will be getting into multi-dimensional matrices to try to solve that one!

The other way to best achieve smooth bass response is to follow tradition and simply experiment. It is hard to change room dimensions, but try moving the speakers around, even by a few feet, and experiment with different listening locations.

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