Part Four
CONSTRUCTION DRAWINGS AND NOTES
PLEASE NOTE WAVEGUIDE REQUIREMENT CHANGES FRONT
PANEL
PLEASE SEE NEW! BELOW
I
Bernard and his Masterpieces (Proud Daddy)
(He may still build them for A$600 each as shown)
See Construction
Drawings further below.
IMPORTANT: The way you implement the
Waveguide will influence your box design, Particularly the Front Panel
construction. There is basically two ways this can be done, the
original construction using a Waveguide similar to that constructed like
this:
We can call this the Square
Waveguide. The alternative is the Round
Waveguide as shown here:
The difference is clear, the 18mm Front Panel becomes a single piece
rather than two. The 25mm Sub Front Panel stays the same.
Want to buy a Round
Waveguide?
Contact Joel Wesseling
neverenoughmusic@hotmail.com.
Post Box Construction
After the box has been assembled, then use plenty of white wood glue as a
sealant. Use your finger by running glue up and down on all internal joins. This
will ensure that joins are air-tight.
Some may question why a vented box should be air-tight when it has a dirty
big vent there. Surely any pressure would escape there rather than gaps in
the woodwork. This also means that we don’t understand how a
Helmholtz resonator works. At the box frequency, when the cone moves in, so
also in the vent the air is also moving in. Both the cone and the vent is
pressurising the internal volume. In fact, the pressures in a vented box are
potentially larger than those of a sealed box. So, bottom line, make sure
that only air in the vent can get in and out of the box.
Other than that, if you have DIY experience, the rest is doable. Please
note, this is a sizeable box of considerable mass, so if you have a bad back
or not prepared to lift some weight, then beg off or get a friend or other
to help. The finished boxes are likely to be 40-50Kg each.
The internal of the box will be stuffed with 60/40 Wool/Dacron bats made by
Insulco (although Bradford makes them too). About fourty to fifty percent of
the volume will be covered. The stuffing will be kept away and not to close
to the rear of the drivers, especially the two top ones. Some experimenting
may be needed, but this is excellent material that breathes a great deal and
has low mass. The Dacron (polyester fibres) keeps the 60% wool as a binding
material and becomes a ‘slab’ about 75mm thick. It’s very easy to work with;
gives excellent results and non-critical as well. Can’t ask for more.
Below shows Mark 3 - but applies to Square
Waveguide:
This shows the old Mark 3:
OLD:
Square Wave Guide
NEW:
New Round Waveguide
Now the 18mm Front Panel will become
one piece, not
two. Mostly the cut-out for the Round Waveguide will be 150mm as it is made
out of 150mm round aluminium. I recommend that you do not cut this
until you have the Round Waveguide on hand, as that 150mm may need to be a
little larger in diameter?
Please Note: The Sub Front Panel does not
change
The
Tweeter mounts behind the Waveguide on the Sub Front Panel. The square
Cut-Outs allows the back of the drivers to have good air-flow into the
internal volume.
This is added to the rear of the Sub Front Panel.
Please Note: Cut-Out must be
precisely in the centre and lineup with the Tweeter on Sub Front Panel.
This is how the above are fitted together:
OLD:
NEW:
If you are using a Round Waveguide, then this will look a little
different.
The Main Brace sits 170mm behind the Sub Front
Panels. Later we will show what part of the volume will be treated with
Wool/Dacron Bats.
NOTE: There is a TOP and Bottom - so orientate in
the box as shown.
IMPORTANT: The UPPER round
78mm Cut-Out is for the Tweeter Terminal (two of them). The square Cut-Out
is for MidBass & Bass Terminals (four in all). IF you are using different
types of terminals, then do these Cut-Outs accordingly. Same applies to 91mm
Port Cut-Out. This may need to be changed, so check that the outside
diameter of your port you will be using.
Next: Internal Wiring & Box Damping
Only Mark 3 Felt Pieces
The Felt is nominally
6.4mm from our supplier - but uncompressed it is near 8- 9mm thick.
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