Which advantages does a subwoofer offer at all?
A subwoofer is not only meaningful for use in home cinemas, but also offers a wide range of advantages when high performance in music reproduction is required:
- Due to the separate bass and main speaker units it is possible to positively influence any resonances that inevitably occur in the listening room, as the physically separated units can be positioned in a more flexible and efficient way.
- In most cases the user will notice that a position that yields optimal acoustic performance for the mid- and high-range as well as for the spatial representation of the sound would prove totally unsuitable for the representation of low frequencies. On the other hand a position where the least room resonances would be caused by the woofer would prove as totally impractical (see example).
- The main speakers can be designed as considerably smaller units with regard to their volume.
- Even when using big main speakers the above-mentioned advantages can be reached provided that the main speaker units and the subwoofer interact correctly, while additionally reducing the load on the main speakers caused by the reproduction of low frequencies. This results in considerably increased spatiality and airiness of the sound. Furthermore the load on the amplifier of the main speaker is reduced, as it is no longer exposed to the power-intensive low-frequency signal components.
My practical experiences have shown that roll-overs and peaks in the bass frequency response, which are caused due to room resonances, may well be in the range of +/- 20 – 30 dB and may even extend up to a full octave even when positioning the main speaker in a suitable way.
When working with separate subwoofer and main speaker units the use of digital room correction systems pays off, as for various reasons major roll-overs in the frequency response cannot simply be levelled out by means of adequate amplification.
Correct use of digital room correction systems enables an optimum adaptation of all speakers to the room both on a frequency and on a time level. In this way a balanced frequency response as well as a substantially increased spatial representation of the sound at the user’s listening place can be achieved.
Such devices are available both for stereo and for multi-channel film sound reproduction and also include all required filters to limit the transmission range of the respective speakers.
Typical frequency response of a suitable positioned High-end loudspeaker at the listening place
Frequency response of a suitable positioned subwoofer at the same listening place