5
Calculating the internal volume
"Free air" installation
The 40 V2 has also been designed to work in "free air" installations, for example into the rear
parcel shelf. With this type of acoustic charge the subwoofer can work to an optimum level
without a huge loss in performance. For such installations it is important to observe these
following rules:
• If mounted into the rear parcel shelf it must be strong enough to support such a heavy
mass of subwoofer. Thus for this reason it is quite likely that the parcel shelf may have to be
reinforced with wooden bracing. Alternatively a custom designed rear parcel shelf made from
thick MDF, can be designed to replace the existing one.
• If a weak shelf is used, the acoustic performance of the subwoofer will be dramatically
reduced. A weak shelf that emits loud vibrations can in effect create an acoustic short circuit.
Recommended power ratings
Polyglass subwoofers are already highly efficient, with improved sensitivity. Therefore, their use
with amplifiers will produce comfortable listening pleasure.
However used in a more high-end system, with more powerful amplification, the audio quality
will be greatly improved. It is very important to check that rated power of the amplifier is
suitable to the subwoofers. Otherwise they may distort, or possible damage could occur.
Always consult the owners manual of the principal source (head unit/amplifier), to ensure the
power rating is compatible. A safe guide is to ensure the maximum power of the amplifier is
not greater than the nominal power of the speakers.
Warning!
The improved power handling has allowed Focal subwoofers to play at very loud sound volumes.
For this reason, we recommend caution be wisely applied, especially during long listening
periods. Excessive volume levels of more than 110dB can cause permanent hearing damage.
Internal
volume
20 L
0,71 cu. ft.
30 L
1,06 cu. ft.
40 L
1,41 cu. ft.
50 L
1,77 cu. ft.
60 L
2,12 cu. ft.
80 L
2,83 cu. ft.
External sizes in inches
and millimetres
with sides of 19mm thickness
(6/8") in medite
A
B
C
D
11
3/4
"
300
14
9/16
"
370
14
9/16
"
370
14
9/16
"
370
15
3/4
"
400
17
11/16
"
450
11
3/4
"
300
14
9/16
"
370
14
9/16
"
370
14
9/16
"
370
15
3/4
"
400
17
11/16
"
450
16
1/8
"
410
14
15/16
"
380
19
1/4
"
490
23
13/16
"
605
28
5/16
"
720
28
11/16
"
730
7
7/16
"
190
9
5/16
"
237
12 L
0,42 cu. ft.
15 L
0,53 cu. ft.
10
1/4
"
260
11
"
280
10
1/4
"
260
11
"
280
13
3/8
"
340
14
3/16
"
360
7
1/16
"
180
7
1/16
"
180
9
5/16
"
237
9
5/16
"
237
6
11/16
"
170
7
7/16
"
190
POLYGLASS SUBWOOFERS MANUAL
U s e r
M a n u a l
notice sub polyglass 2.indd 5
notice sub polyglass 2.indd 5
16/04/07 15:25:59
16/04/07 15:25:59
