Speaker placement

Docfoster

I've been casually experimenting with the effects of moving my speakers forward and backwards slightly. This is not something I do regularly, although it is often something that I find myself doing when I introduce a new piece of kit and the sound of the system changes.

These most recent slidings around were prompted by my perceiving a slight lift in bass levels after I switched the IEC connector to my power amp. Obviously I might be going insane. I entirely accept this as one possibility...

With regard to movements to the speaker position I think the general effect (and one that I think is in line with conventional wisdom) is that the closer to the wall the speaker moves, the more bass energy there is reaching my ears / liver. However, my feeling is that "bass energy" is something of a blunt term here, as the increase in "bass energy" sounds like it is an increase to specific "bass" frequencies, creating the effect of a badly designed port (my speakers are closed boxes). The subjective effect of this is that bass sounds take on more of a uniform, one dimensional quality and sound a bit "lumpy". So although as the speakers move closer to the wall things do sound more "bassy" in the broadest sense, they do so in a rather monotone and untextured way. Not good.

Another, perhaps linked effect is that as the speakers approach the wall things sound less distinct; tonally and spatially.

I think I can notice differences even when the movements are quite small. Possibly just a few centimetres. The rear of the speakers were 26cm from the rear wall, now they are 30cm away (I suppose proportionally that's not insignificant (nearly 20%) and I am sure they sound better. Bass sounds (bass guitars, kick drums) are more authentic, and other, higher-up sounds are more unique (ie display more variance due to original instrument, recording techniques, etc.,...) and seem to hang more separately from each other. Perhaps all these symptoms spring from some disproportionate emphasis of certain frequencies brought on by their reinforcement by the rear wall.

I'm interested in people's thoughts on this, and any experiences with shifting speakers.

uglymusic

My mate Big Trev shifts a few speakers, if you're interested Ben.

He says he's got some good ones from a mobile disco.

Docfoster

Trev, yes. I got some white goods and a used laptop from him just before Christmas.
He said then that he was on the look-out for "AV stuff".

PAC

It's room dependant as well as speaker dependant Ben and also depends on the listening position.  Try entering your room dimensions into one of those on-line room mode calculators/simulators and have a look at where the bass energy peaks and troughs occur relative to your seating position.  Move just a metre and you can have significant impacts on perceived bass response in some rooms.

RE speakers (any speakers) the relationship between bass and wall placement is generally that you move from bass being omni-directional at lower frequencies (ie below baffle step frequencies) in free space to radiating more directly into 2Pi space with close-to-wall placement (ie the semi circle formed by the pressure wave in front of the speaker).  Whilst energy cannot be created or lost (law of energy conservation), you can get up to a 6dB gain (or more for corner placement) in direct radiated frequencies at frequencies occurring below baffle step.

How clean or otherwise can be as much to do with room acoustics as speaker design.  Place a speaker in the corner or equi-distant from rear wall and side wall and you can get formation of standing waves (reinforcement of certain frequencies depending upon distance to speaker) causing boom and muddy bass.  Move away from corners with speakers still plenty far enough apart and you should get a cleaner bass reinforcement.

It helps to look at where room modes occur at varying frequencies and compare with your seating position and see whether moving where you listen from improves or worsens matters once you've settled on best placement for the speakers.  All rooms are a compromise as we have to live in them too (unless lucky enough to have a dedicated listening space) so experimentation is the key.

Docfoster

Fascinating to read the physical explanations for things Paul. As always I love this stuff. And even nearly understand some of it.
May try the on-line thingies. Elsewhere, what you're talking about (corners, 6dB gain, and so on) seems to resonnate (see what I did there) with what I'm hearing.