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DLS SOUND HANDBOOK SPEAKER BOXES
BANDPASS BOXES
In all bandpass boxes the speakers are hidden
inside the box, all sound is coming out through the
ports. There are different types of bandpass boxes
and they have in common that they are a bit more
difficult to build.
BOX DESCRIPTION
Mechanical orders for speaker boxes:
1:th order
Speaker in free air. Not in practical use, the
speaker is acoustically shortened.
2:nd order
Speaker mounted on a baffle, normally called
"open air".
This is not a box, just a way of mounting the speaker. For
example in a hat-rack or behind the rear seat. Can create a
good sound with the correct speaker parameters. The speaker
should have a low resonant frequency.
3:rd order
Speaker mounted in a sealed box.
A sealed box is easy to build and calculate. It also has a high
power handling capacity. On the other hand it has low
efficiency and the box must be rather big to create a deep bass.
With a rather small box and a 20-40 Hz subsonic filter you will
get a box suitable for hard rock with a fast attack in the bass.
4:th order
Speaker mounted in a vented box, often called
bass reflex box.
A vented box has a higher efficiency and a higher power
handling capacity than the sealed box - but only if it´s correctly
calculated with a suitable speaker element. Suitable for all
kinds of music. The power handling capacity below the F-3db
point is rather weak. It is important that the ports are correctly
tuned, they must not be too small, then whistling sounds can
occcour. With a wrong port the sound from the ports comes out
phase reversed and causes a blurred sound.
5:th order
Speaker mounted in a sealed box, playing into
a vented box.
This type of box can play one octave only, but it has a high
power capacity and gives a 3-5 dB raise at it´s tuned frequency.
Suitable for disco and hard-rock music. Difficult to build and
calculate and you can´t have speaker cloth in front of the ports.
6:th order
Speaker mounted in a vented box where both the
speaker and the port is playing into another
ported box.
This box is also difficult to calculate and build. Plays 2 octaves
and gives a natural cut-off for higher frequencis with 12 dB/oct.
which reduces the audible distortion. It has a high efficiency
and power handling capacity. Low F-3dB and a top at the tuned
frquencies. Small ports gives a whistling sound and you can´t
have speaker cloth in front of the port. Build as isobaric it
creates a powerful and distinct deep bass.
SPEAKER CONSTRUCTION
speaker cone
chassie
voice coil
magnet
15
suspension
spider
dust cap
pole plates
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