Vented Floorstanding Speaker - Construction
Latest update (1/3/99) :
of these speakers which always bugged me was the appearance
of the top plate or cover. This plate covers the crossover
chamber and is made of oak plywood glued to a substrate with
solid oak on the edges. The edging was applied quickly and
was not mitered. This left endgrain showing on the sides -
ugly ! I finally got around to fixing this by making new tops
for both speakers. I used 3/4 inch cabinet grade oak plywood
and 3/8 inch solid oak all around. Corners are mitered and
the entire top has a 1/4 inch roundover applied to the edge.
in the body of the text (below), R19 fiberglass insulation
was stuffed in parts of the box. The effects of this stuffing
was never tested. Until recently, I had all but forgotten
that I had done this. I recently removed the stuffing from
these speakers, and the resulting bass seemed to be "tighter"
but only by a slight amount. I don't really note any other
changes in the sound, but when time allows, I 'll go back
and tinker with this some more.
out by getting the drivers. This turned out to be the longest
lead items because I waited for sales in order to minimize
the cost of the project. Since I was working on another project
at the time (subwoofer), this was not a problem. Both the
AC-10 and 5N313
were sale items and saved me about $25 combined for each speaker.
The D2905/9000 also comes
in a D2905/9300 version
which became available just as was going to purchase the /9000.
I decided to stay with the former due to its proven reputation.
The woofer came direct from AC Components, a division of ACI,
while the midrange and tweeter were purchased from A&S
(no longer in business).
material is an area where great savings can be had without
sacrificing overall quality. I browsed through Howlett's
Bargain Bay, a local store that sells closeouts, recycled
and reclaimed materials and found 1 inch and 3/4 inch MDF
at prices below that of warehouse or lumber stores. The 1/4
inch oak plywood was purchased from HomeQuarters Warehouse
(HQ) and is the single largest expense on the enclosure totalling
about half of the materials cost. Shopping around on the materials
can really pay off. Note that while such savings are nice,
this is not an area to "cheap out" and use low cost
particle board or flake board. It doesn't make sense to save
a few dollar when the drivers used cost so much more. If you
can't find the bargains I found, splurge and buy the MDF at
retail prices - it'll make a different you can feel and hear.
is made is two layers - an inside MDF box and an external
oak plywood layer for that finished look. I started out by
cutting all panels down the size. The actual dimensions of
the box was dictated by the MDF stock I had purchased. This
stock came in 4 ft sheets by roughly 1 ft width. I made the
outside dimensions of this box 11.25 wide X 14.75 deep X 48
are simple butt joints held with wood (yellow) glue and particle
board screws. Most screw extend at least 0.75 inch into the
substrate and are countersunk to keep them at or below surface
level. Biscuits are used in some places for alignment but
are not required. Caulking is applied to all inner seams.
Looks don't count here, since the oak plywood covers everything
later. Clamps (lots of them) really helps on this project
baffle is 11.25 X 48 X 1 inch MDF. The rear panel is the same
but in 0.75 inch MDF. The side panels are 13 X 48 X 0.75.
Where the woofer and midrange are mounted, and additional
3/4 inch layer of plywood is glued onto the MDF on the inside
for improved stiffness and better screw holding. There are
three compartments in this box for the woofer, midrange and
is located on the top of the speaker to satisfy the goal of
accessibility. A 9.75 x 13 x 0.75 inch MDF board isolates
the top 3 inches into a seperate compartment. An 8 post terminals
cup passes the input signal to the crossover and returns signals
for the 3 drivers. Crossover components are mounted on a board
and screwed to wooden standoffs in this compartment. The top
of the speaker covers this compartment but is not held down
with fasteners thus allowing access to the crossover. This
top is 0.75 inch MDF plus 0.25 inch oak veneered plywood and
solid oak banding. It measures 11.75 X 15.75 so that it sticks
out the front by about the same amount as the lower skirt
does. Small adjustable wood blocks on the underside of the
top protrude into the crossover chamber to form a snug fit.
chamber is 0.25 cu. ft. in volume. The internal dimensions
of this chamber is roughly 7 inches tall, 6.5 inches deep
and the full width of the speaker or 9.75 inches. Wiring to
the midrange is made via a small hole in the chamber along
one of the wall which is then sealed with caulking. The lower
edge of the chamber starts 24.25 inches from the bottom. Chamber
walls are made of 0.75 inch MDF.
of the enclosure above, below and behind the midrange chamber
provides the roughly 2.9 cu. ft. space for the woofer. This
space is braced in three places. The first two are at the
top and bottom of the midrange chamber. Since this chamber
extends more than halfway into the enclosure, bracing the
rest is easy. I glued and screwed 1.5 inch wide X 0.75 inch
thick plywood strips along the side and rear walls at both
these locations to form part-I beams. The third bracing location
is just beneath the woofer where a similar brace is used all
around the perimeter of the inside. Note that these three
locations correspond to the seperation between port, woofer,
midrange, and tweeter.
baffle has 4 cutouts to hold the port and drivers. All circular
cutouts were made with a circle cutting guide attached to
a router and a straight cutting carbide bit. Dust collection
at this point is real handy as routing MDF causes a real mess.
A dusk mask is a must, and a respirator is recommended. The
router jig is mounted at the center of the opening and is
first used to cut the driver mounting flange. The depth of
this depends on the driver used. The router is then used to
used to cut most of the way through the MDF for the driver
body. Don't cut all the way through since the router is attached
to the middle. I used a jigsaw to finish the cut through.
The port is a 5 inch long piece of 3 inch I.D. PVC pipe and
is centered about 8 inches from the bottom. It's important
that the hole be snug. Caulking is applied on the inside seam.
cutout is centered about 18 inches from the bottom. Note that
the inside width of the enclosure is 9.75 inches but the driver
is 10 inches in diameter. The outside width of the baffle
is 11.25 inches. The 1.5 inch difference is used by the two
0.75 inch joints with the side panels. There are 8 mounting
screws on the woofer; one every 45 degrees. When mounted,
the woofer is rotated such that two screws form a vertical
line on the edges. This alignment keeps the screws away from
the side panels. Note that screwing into the side panels is
not a bad thing; screwing into the edge of the side panel
would be since it could split the panel.
center is located 28.5 inches from the bottom and offset 0.5
inches to one side. The two speakers are mirror pairs so the
offset of one is the opposite of the other. This location
should place the midrange entirely in its chamber. Unlike
most drivers, the Focal 5N313
has a square mounting plate with rounded corners. I used the
circle cutter to cut the rounded corners, drew a line connected
them to form the straight portion and chisels along this line
to the right depth. An alternative way would be to build a
template out of plywood and use a template-following router
is offset by 1.5 inches in the same direction as the midrange.
It is centered 34.5 inches from the bottom. The eventual addition
of a skirt around the base will add 1.5 inches to this height
placing it 36 inches off the ground.
of the chassis is made from a 9.75 x 13 x 0.75 inch MDF board
with a circular cutout for a 2 post terminal cup. I used 16
Shack Megacable to connect the input terminal cup to the
crossover terminal cup. Wiring from the crossover to the drivers
was then added. All wiring is held against the walls by caulk
and hot melt glue.
and back panels are covered with 3 layers of 50 pound roofing
felt (about 0.25 inches thick). I used a combination of caulking
adhesive and roofing nails to attach the felt to the panels.
R19 fiberglass insulation is then added before the chamber
is sealed. The area behind the port is not filled. I didn't
play with the stuffing for optimal quantity or type.
inner box done, the outer oak plywood is added. This plywood
has "A" and "B" sides - the better "A"
side is the visible side. The plywood covers the sides and
rear only, not the front. This is because the MDF I used for
the front panel already has an oak veneer on it (though in
the wrong grain orienation; but it gets covered by the grill).
The plywood is undersized in width to allow solid oak to cover
the plywood edges. I milled 0.25 inch thick solid oak for
this purpose and like the plywood, is glued to the MDF box.
My oak trim is about 5/8 inch wide.
bottom of the speaker is a skirt made of solid oak. The skirt
is about 5.5 inches tall and 0.75 inch thick. It wraps around
the entire bottom and is beveled along the rear and sides.
The front is not beveled due to the grill. I used miter joints
on the skirt corners for the rear and butt joints for the
front by mistake - use miter joints all around for a better
look. The skirt entends below the box by about 0.625 (5/8)
inches and is attached to the box by glue and particle board
screws. Since these screws are visible, they are not only
countersunk but also covered with an oak plug cut from the
same oak stock using a plug cutter drill attachment. The skirt
holds four 0.75 inch solid oak feet, each 2.75 inches on a
side. These are glued, screwed and countersunk from the bottom.
Because the speakers are to be used on hardwood flooring,
self-adhesive felt pads from the local home center are added
to the feet. Final clearance under the speaker is less than
1.5 inches to allow connection to the terminal cup. Wires
to the speaker can come out from any side at the bottom.
finish used is Watco Danish Oil in dark walnut, darkened with
some Minwax Jacobean stain. Two coats are applied, followed
with a coat of hand rubbed wax.
from the port at the bottom to the tweeter at top is quite
large. Therefore I decided to let the grill cover the entire
front baffle, including the unused area above the tweeter.
The grill will be flanked on top by the crossover cover and
at the bottom by the skirt. The grill measures 11.75 X 43
inches and is made of scrap ash glued together and milled
to approximately 1 inch in thickness. Horizontal and vertical
members are doweled together and MDF corner blocks are added
on the inside corners. All but the inside facing portins of
the grill frame is spray painted black. This hides the frame
when the black grill cloth is stretched over the frame.
socket connectors are used to mount the grill to the speaker.
To allign the ball and socket connectors, I used a drill press
to drill holes through the corner blocks at 90 degrees to
the blocks. With the grill frame placed over the baffle and
temprarily secured with clamps, I then drilled through the
same holes on the grill into the baffle. These pilot holes
are then used to start the final correctly sized holes for
the ball (grill) and socket (baffle) connectors.
mentioned, the grill is flanked at the top and the at bottom
by the crossover cover and lower skirt respectively. The sides
howevers are exposed thus the grill cloth is made to wrap
around its frame to cover the frame itself. Due to the size
of the grill, I decided not to use spray adhesive, hot glue,
staples or other common method of fabric fastening. Instead
my wife came up with a simple yet effective way to fasten
grill cloth described in a seperate
box done, it's time to mount the drivers. Be extremely careful
with the ScanSpeak tweeter as the damping material coating
the dome is extremely sticky. Dust, dirt and just about any
construction particle will stick to it and be very hard to
remove. I soldered a short length of wire to each driver which
is then connected with the internal wiring of the enclosure
with standard wiring nuts. This allows me to remove the driver
at some later point without needing a soldering iron. Metal
screws hold the drivers in place to complete the installation.
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