The Subwoofer DIY Page
Examples of EBS systems - (2)
last updated:13 April 2011
The Subwoofer DIY Page

Example 2:
The following is another example of an EBS system. The driver is a Focal 8v416 with the following T/S parameters:

    Fs = 22.83 Hz
    Vas = 112.3 litres (3.96 cu.ft.)
    Qts = 0.297

The following are two possible ported alignments for this driver. The first alignment is a maximally-flat alignment. The second alignment is an EBS alignment using a box that's more than twice the size and a lower tuning frequency. From the graph below, you will notice that the EBS alignment produces more output below 35 Hz (and significantly more below 30 Hz), but 2dB of midband efficiency is lost. Midband power handling is also reduced, but there's an increase in the power handling at lower frequencies due to the lower tuning frequency. The response at 20 Hz (-9dB) should produce excellent results when the average room gain is factored in.

    Alignment: Maximally Flat
    Vb = 1.52 cu.ft.
    Fb = 30.4 Hz

    Alignment: EBS
    Vb = 3.22 cu.ft.
    Fb = 24.5 Hz

Graph of EBS frequency response

    My thanks to Gary Markowitz of the BASS and DIY Loudspeakers Mailing List for providing me with this particular example of an EBS system. The graph was generated using my PORTED.XLS design spreasheet.