Room Treatment on the cheap-ish

Making a silk purse out of a sow’s ear? Maybe.

So, following up on the previous build.

Trap that sound

Let’s test whether there are any measurable results, shall we?

Here they are: the odd squad.

Testing was done with playing an impulse through the monitors https://www.akaipro.com/rpm3 and recording with a condensor mic. https://www.audio-technica.com/en-gb/catalog/product/view/id/4010/s/at2035

Impulse response - Wikipedia

The principle of emitting an impulse is that an even band of all the audio frequencies is emitted into the space and then the outcomes are recorded.
A perfect setup would look the same — good luck with that, by the way, and any sonic colouration due to reverberation across the reflective surfaces will be revealed. Resonances will result in peaks in frequencies and also a slow decay of that frequency. Anti-resonances will result in deadening of sounds and notches.

Here’s the input impulse and the recorded waveforms for before and after (at the bottom).

We can see the decay time is faster for after treatment, and the sonic difference to the human ear is pretty clear.

Input, before and after.

Spectrum from the impulse before treatment

Spectrum from the impulse after treatment

The spectra do not show a very convincing story: the bass and treble peaks are maybe smaller, but it’s hard to tell from that.

Sonogram of the input and measured traces

In contrast the sonogram very clearly shows the differences.

Conclusion

Even with the minor area coverage, those annoying reverberations are gone, and no doubt more would make more of a difference. This much is enough for now, but maybe later we’ll do more.