Examples Of DSP Use

It's quite interesting to see that the big Audaphon or Sitronik amplifiers with DSP are usually combined with:
- 1 to 4 Wavecor SW310WA01 or
- 1 to 4 Wavecor SW270WA01 or
- 1 to 4 Wavecor SW223BD01 or BD02 or
- a Wavecor SW312TU01 or
- 1 to 4 Visaton TIW 300 or
- with the Alcone AC 10.

The reason for this is that these drivers have strong a drive / magnet (only a strong drive forces the voice coil to move exactly within the magnetic gap according to the voltage applied).

The problem comes up that - even with strong drive systems - there is bass lacking. This is due to bass drivers that are too small: for reproducing a frequency of 20 Hz the driver needs to have a circumference of roughly 340m / 20H = 17 metres.

Bass is often added by weak drivers causing resonance, but also a lack of precision. There is another way, however.

The low sound pressure level coming from the deep bass may also be increased by using a subwoofer amplifier. Additionally, room and fixture resonance may be cut out partially by less agitating them.

We have chosen one of the best drivers for our subwoofer. Four Alcone AC10 SW4 (as in Sub 40) were used in our following sample.

Picture 1: frequency response of Sub 40
at 85 Hz upper crossover frequency
as closed cabinet (red curve),
and as bass reflex cabinet (blue curve)

The higher efficiency of the
bass reflex is clearly noticeable.
The characteristic curve corresponds to a sound pressure level at 2.83V measured at one metre.

Both frequency response curves have their own appeal. The closed subwoofer produces an absolutely tight and precise bass. The maximum volume is, however, much lower as with a bass reflex type.

We have chosen the Sub 40 because it's perfectly suited as closed and bass reflex version - and in addition to this using the same cabinet.

Using the digital sound processor the frequency response may be adjusted according to the listener's taste; either for bass reflex (extreme bass for home cinema or organ music) or a closed cabinet. Considering the closed cabinet we have adapted the frequency response for our room as follows:

Picture 2: recording by the PC software supplied with the Sitronik module. With this software package
the frequency response may be adjusted and then downloaded to the amplifier module (red curve:
frequency response of the subwoofer, blue curve: the satellites - in this case congruent).

If the Sitronik VP300 D is adjusted that way the light green curve in diagram 3 shows the result:

Picture 3: frequency response of Sub 30
at 85 Hz upper crossover frequency

- as closed cabinet (red curve),
- and with the parameters in picture 2 (green curve)
- compared with bass reflex set-up (blue curve)

After having completed the speaker we and many of our customers expect freedom of choice between:

All three solutions will allow the listeners to consider the room conditions (see previous page)

Subwoofer with DSP: Sub 10 DSP     Alcone Sub 20 Definition