Rockford Fosgate RFS-1408, Installation & Operation Manual

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Building an Enclosure
To work properly, the walls of the enclosure must be rigid and not flex
when subjected to the high pressures generated by the speaker's
operation. For optimum performance, we recommend using 3/4"
MDF (Medium Density Fiberboard) and internal bracing. The enclo-
sure should be glued together and secured with nails or screws. MDF
is porous; therefore, it is suggested to also seal the outside walls with
polyurethane.

Calculating Volume
Calculating volume is merely a matter of measuring the dimensions
in inches and using the formula:

1728"

Height x Width x Depth

Box Volume =

   (cubic feet)

If two facing sides are of uneven length, add them together and divide
by two to take the average. Using this number will give you the
volume without the necessity of calculating the box in sections and
adding the sections together. The thickness of the baffle material
reduces the internal volume so this must be subtracted from the
outside dimensions to determine the internal volume. The speaker
itself also reduces the internal volume. The amount of air displaced
by each model is listed on the specification sheet and should also be
subtracted from the gross volume calculation.

Subwoofer Crossovers
There are two operational types of crossovers, passive and active.
Passive crossovers (coils or inductors) are placed on the speaker leads
between the amplifier and speaker. An active crossover is an elec-
tronic filter which separates the audio signal fed to different amplifi-
ers. 

For optimum subwoofer performance, we recommend using an

active 80-100Hz low-pass crossover at 12dB/octave.

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