LOUDSPEAKERS 2, DIY.

Content :-

Design details,  Sublime speakers shown at Loudspeakers 1, premium quality.

Design details, Single box full range floor stander speaker with full explanations
with reasons for using this design.

Image 1,  SUBLIME from 2000.

sublime271w360h.jpg

Drawing 1. Sublime Bass speaker box. Sublime-13-may-2012-bass-box-58L.GIF
Drawing 1 shows all construction details for the bass box using 40mm thick plywood,
or multiple layers of ply such as 2 x 17mm plus 4.5mm finishing ply, or from 40mm joined
hardwood planks which have been kiln dried to prevent severe expansion and contraction.

In my original Sublime from 2000, I used 2 layers of 17mm pine marine grade plywood for top,
bottom and two sides, with a final 4.5mm thick veneered finishing plywood. To hide end grain of
plywood at rounded corners I used solid timber quadrants well fitted and glued. For all veneers
and solid timber I used Victorian Mountain Ash which I found easily available locally.
It is possible to use veneer finished particle board and MDF but these products are very
inferior products to real plywood.
I have been told that bamboo plywood has become very preferable but I have yet to see a
sample in my hand or try to work with it and until I am proven wrong, bamboo ply is a cheap
low quality product which may provide some cheap solution to the huge future increase in
demand for some sort of timber finish that is affordable by teeming billions becoming more
able to purchase the pretentious western way of life.

DIYers may not be so good with woodwork, and since having a nice finish that feels like
touching a Norwegian Goddess does not make the sound any better, I could suggest all
panels can be made using a single layer of suitable plywood 40mm thick, planed, filled, and
sanded smooth to give the shapes shown, and then given several coats of acrylic water based
semi gloss house paint with color chosen by the missus. Such paint is best applied using
a small 100mm long fine hair roller which will leave no roller or brush marks, and leave a
slightly orange peel texture to the paint surface. Try it, you will like it, and save yourself
a pile of time and unnecessary expense of trying to be pretentious.

My bass box uses one 210mm SEAS driver unit with Vb = 50L to get maximum LF extension.
Some 200mm bass drivers work OK to make low bass in only 40L, so for two drivers, 80L would
be OK. The bass box Vb is easily changed during the design stage, and for 80L instead of
50L, with two bass drivers in the front panel, the internal front to rear box dimension is simply
increased from 400mm to 640mm.

And BTW, the bass box recipe as I have it could be used to make a good sub-woofer.

Drawing 2. Sublime Midrange and Tweeter box.

Sublime-13-may-2012-mid-treble-box-11L.GIF

The Supreme two box recipe using rectangular shapes will give excellent sound.

One older customer of mine built a very good pair of enclosures using 35mm
thick Australian blue gum planks normally used for roof trusses. This material
has a density close to 1 gram/cc, much more than pine plywood at about
0.55 gram/cc. If real timber is used it must be kiln dried, not just air dried lest it
shrink unevenly too much after the speaker is built.
My Supreme and Sublime have laminated ply sides, top and bottom, with real
hardwood timber planks for front and rear panels. Fronts are held to sides with
internal aluminium angles with slotted holes and many wood screws with a
foam gasket, thus allowing real timber to expand and contract across more
rigid sides+top+bottom which does not expand/contract because it is plywood.
Rear panels are also hardwood real timber, 32mm thick, with 75mm long
screws from the outside and a foam gasket used between the join which
squeezes up to less than 1mm thick.
 
The foam join also absorbs vibration "around the corners".

The most important property for speaker boxes is to make them acoustically dead
so panel vibration, internal standing waves, and coloration of the music is minimized.
The technique is the opposite of building a
cello.

The Supreme speakers use a D'Apolito arrangement of two x 125mm MF and one HF
dome tweeter in a 20L box. When using more MF drivers, the Vb needs to be increased
proportionately.

If say 4 x 5" Peerless MF units, type P850489 are used with two Peerless HF 810921,
then box Vb = 36L, so oa sizes become 720mm x 238mm x 380mm. The D'Apolito
arrangement with Mf-MF-HF-HF-MF-MF would be OK,
and best with small dia HF now available, so that box height could be kept under
720mm, and box Vb maintained by increasing the front to rear dimension.
The Peerless MF 4" 830881 plus HF 1" 810921 could also be used to keep box size smaller
yet still give the wanted 200Hz to 20kHz F range.

___________________________________________________________________________________

For those without much skill or money, they might allow themselves to make a full range floor stander
with a 3-way set of drivers. A couple of DIYers have done just this and gained excellent results.
One fellow made his boxes as detailed below, then sent them to me to have drivers installed and have
crossovers designed, built, and all fully tested. So I know this idea works well.

Drawing 3.

3way-speakers-tapered-box-may2012.gif
The above speaker design features the following :-

1, Sloping sides to make the speaker tall enough for good treble and mid-range height
so that speaker stands are not necessary.
2, Has enough total volume to form the TWO separate bass and mid-range rear chambers
to suit most brands of available drivers, not just Peerless.
3, Sloping sides minimizes standing waves between sides inside the enclosure.
4, The speaker shape is much less likely to fall over than a tall narrow rectangle shape,
and the speaker weight with large base dimensions gives good stability without
needing floor spikes.
5, The project does require a diyer to be capable of working with angles other than 90 degrees.
Although this is challenging, and more difficult than making just one tall rectangular box,
the acoustic properties with sloped sides as shown will be superior.
6, The appearance is more interesting, and more functional because the
"pointy top"
and well rounded small width amount of front panel around the tweeter will
minimize diffraction and give a flatter frequency response, better imaging, and and less "beaming".

7, The slope of the front baffle panel gives some vertical alignment of voice coils.
8, The design is suitable for those extremely well skilled with timber finishes
or for those who may wish to just apply paint.
9, The angle chosen for the "lean" of every side off the vertical is the same so setting
out the cutting of the sheet of plywood, MDF or other material is fairly waste free.

The 8 vertical panels shown should be able to be cut from a single 1,200mm x 2,400mm standard
sized sheet of material. The cut out pattern is on the above Drawing 3.

As long as anyone adheres to the INSIDE dimensions of the box, then the panel material
can be any timber type above at least 33mm.
I personally do not like 33mm MDF or pine particle board. What I DO LIKE is marine grade
pine plywood. It is not always easy to buy from a builder's supplier, so you may have to
search around for it, and it costs more than MDF, but the expense on good plywood is
minimal compared to all the other things you will have to purchase plus the value
of YOUR TIME.   

OPTIONS.
Let us suppose you wanted to have say 150mm midrange and 250mm bass.
The box can have the same angles of slope, and same overall height, but may be 30mm wider.
The two Vb would probably need to be increased to say 25L and 65L. The front to back
overall size would need to be increased perhaps to 650mm, but you would have to work that
out yourself. The amount of plywood needed will increase, and the number of braces should
also increase.

SPECIAL CHALLENGES.
Because the vertical panels all slope towards each then at the vertical corners any
two meeting panel joins will not meet perfectly if the all edges are cut with "square edges".
The panel which butts to the surface of another at a corner will need to be planed with
a slight angle of a few degrees, or slightly "beveled" to get good meeting surfaces.
Even though the drawing looks quite simple, the woodwork is quite tricky because
of the angles of cut and bevels involved.
Some DIY carpenters will probably curse and swear when they must return to the
timber store to buy ply more after cutting something wrong.
But a DIY person could indeed get all panels cut with square edges but say
+2mm larger in size all around, so that the required edge beveling may be
done using a hand plane carefully to establish the required angles, and so
gradually get all 4 vertical panels to have straight corners, and with gap free
meeting surfaces that will hold glue when applied.

The design aim is to create something above the ordinary.

While I am alive, I shall not imitate or promote mediocre speaker designs and
nor will I promote your tendency to be lazy.

Remember the golden rule, check measurements 3 times, cut once for plywood.
( If you measure just once, then cut once for FIREWOOD ! )

DIFFICULT GEOMETRY!
I can say that many will struggle to handle the geometry of these boxes where
there are almost no 90 degree angles. If have very poor woodwork skills, and
you don't have a good set of tools and a workshop, then DON'T build these
speakers.   


Suppose you use two sheets of marine ply, each 1.2M x 2.4M and one is 16mm thick
and the other is 25mm thick, and you glue the two sheets together while laid out on a
dead flat surface, then you would get a panel 41mm thick. You should be able to cut
the 4 fronts, backs, sides, tops and bottoms for BOTH boxes from the 1.2M x 2.4
standard ply sheet size with little waste. You may find you need some extra ply for
the dividing bulkhead and the braces, but this material can be ordinary low grade ply
of at least 17mm thick.
The weight of the two boxes will be about the weight of the 41mm thick sheet
= 1.2M x 2.4M x 41mm x 0.55gms/cc = 65Kgs. So each speaker with drivers will weigh
about 39Kg.

1. TEMPLATE.
Before anything is sawn or glued, a full size drawing of the box is produced on a
spare clean blank sheet of thin MDF material which becomes the TEMPLATE
for the work. When panels are cut to size and edges planed to fit and they may be
laid on the template to check sizes and angles. Working with a template avoids
mistakes, and the first time anyone uses a template they will appreciate it fully,
and wonder why they didn't use one before.

2. SMART ARSES might just employ a plan printer to enlarge my drawing until
it comes up to the actual sizes, and they would then glue the full size drawing to
a thin sheet of MDF, or thin plywood to make the template.
 
3. MY DRAWING was prepared in MS Paint with box dimensions TO 1:5 SCALE,
using a scale ruler laid over the PC monitor to adjust the line positions to the nearest
pixel. How it looks on your PC is anyone's guess, but the .gif drawing shown be
able to be reproduced in the printer's image program and enlarged, keeping the
aspect ratio constant, and sizes correct.

4. CROSSOVER FILTER BOARD is not shown on the Drawing 3. The filter board
can be made using 12mm plywood about 180mm x 250mm and with all L and C and
R parts glued to the board with Selleys 401 silicone. Circuit tracks should be
1.2mm solid copper wire soldered around 16mm long x 4guage brass wood screws
in 12mm ply.
Crossovers filters are fitted after box is finished and testing of response is completed.
These boards should be screwed to the bottom panel on a layer of 6mm foam.
The boards and all their parts should be entirely well painted with polyurethane
varnish to all surfaces before final installation.

5. SPEAKER TERMINALS should be for recessed 4mm banana plugs only, because
I don't like any other type. I like to have 4 terminals for using bi-wiring or bi-amping.
These should be set at least 40mm apart to void letting strands of cables causing
all to easy short circuits. The detail may as I show in Drawings 1 and 2 above for
my Sublime speakers. If binding post action is wanted, use Drawing 1 detail
where the posts fit into a removable ply panel, and such binding posts are unlikely
to all too easily be snapped off when speakers are moved around.

6. SETTING OUT shapes of vertical sides on the 1.2M x 2.4M bulk sheet of ply
should be done with care and to allow for saw blade thickness, so allow 3mm between
lines if the saw is a 170mm circular type with 2mm blade cut. Don't try to cut beveled
edges to panels, its far to confusing, just cut all panels with a square saw cut, and then
apply beveling to meeting surfaces as try to assemble panels.
The assembly of ALL panels, bulkhead and braces should be achieved BEFORE
any glue is applied. Rounding off external corners is done after gluing and dowel
fixing is complete.    

7. FOUR VERTICAL PANELS should be joined at each corner after careful adjustment
of edges with a plane. 60mm long wood screws may be used to hold panels together
temporarily as you proceed. You will find external surfaces at corners will need to
be planed flush, but leave that until all glued including dowels.
After the 2 sides, front and back are together, the back may be removed, and bulkhead
and braces fitted and held by screws.
The back is then re-fitted to ensure the bulkhead and braces all fit with nothing binding
or causing bulges. 

8. THE BULKHEAD should ensure the 4 vertical panels are at 90degrees to each other in
the vertical plane.

9. TOPS AND BOTTOMS are shown fitting BETWEEN the vertical panels so that
the joins tend to be hidden. The positions of where the tops and bottoms butt into
the front, sides and back must be well drawn while setting out so that after planing
tops and bottom edges of verticals to make over all surfaces, your box will stand
straight, without any "wonky lean", or un-level top surface.

10. My Drawing 3 shows the top and bottom panels fitting between the vertical sides.
But if anyone wanted to fit tops and bottoms extending over the vertical panels, it
won't make much difference to the box volumes of frequency behavior, and many
DIYers would find the construction easier. The height of vertical panels may be kept
at 1,000 mm, and with tops and bottoms fixed over this height, the overall height
1,066mm, quite acceptable. Dowels are later fitted vertically.

11. SPEAKER DRIVER HOLES in the front panel may be set out and cut with a
jigsaw before fitting anything together. 

12. BASS PORT HOLE in the rear panel may be set out and cut with jigsaw
before fitting anything together. For this, you will need a 300mm long piece of
PVC sewer drain pipe, and the hole is cut and trimmed to allow a horizontal
pipe position, and a sliding fit, to that later the port can be glued with top quality
silicone such as Selleys 401. The internal retaining block at the internal port
end can be fabricated later after assembly and glued in then entries rounded
up to prevent port wind noise. The port length cannot be determined until
the bass driver is tested in the box. The port and support block are fixed after
driver tests are complete, and access to internal block positioning is through
the front bass driver hole.


13. BRACES AND THE INTERNAL BULKHEAD between mid-range and bass
should all be fitted and temporarily screwed in place when 3 sides are together,
so you can see what you are doing, before the 4th panel is fitted.
75mm long phillips head screws about 10 gauge meant for particle board fixing
are ideal, and should be placed where a dowel is to be placed later.
I use lots of masking tape to hold panels before drilling a 4mm hole for screws.
I only have 2 hands, and I wouldn't mind 3 more pairs.

14. WHEN EVERYTHING FITS WELL, mark meeting panels and items with A & A,
B & B so that when temporary screws are removed, you will know what has
to fit together during the gluing procedure.

13. MARK OUT DOWELS. All positions for 8mm dia dowels need to be marked
out neatly in pencil.

14. GLUING UP EVERYTHING. Gluing may commence with one side panel
laid flat on the bench. Use generous beads of PVA glue from a 1Litre glue bottle.
Bring say a front panel to lay against the side and insert screws and tighten.
Excess glue will overflow from joints, which means you have plenty of glue
where its needed. Proceed to glue and screw another side, then braces and
bulkhead. glue the back on, then top and bottom, and don't forget to leave anything
out!
Have a bucket of water and piece of towel cloth sitting ready to wipe away excess glue
on the outside of the box. Leave it standing upright for a day so glue cures.

15. Fixing Dowels.
Use only 8mm hardwood dowels. Cut enough 80mm long x 8mm
dia dowels for the number required.
Usually 8mm dia dowels are available at good builder's hardware stores. Drill ONE
dowel hole 75mm deep using an 8mm drill, and try the dowel fit to make sure the dowel
is an easy sliding fit, and does not need to be hammered into the hole and is not a
a sloppy and loose fit.
A d
ay after everything is glued, the screws may all be removed. The box will be fairly strong.
To ensure a 500 year life, 8mm holes are drilled 75mm deep where the dowel positions
are marked, which should include where temporary screws had been used. 
Squirt some glue down each dowel hole.
Get a 6mm dowel or "stick" and stir the glue
around in the hole to ensure all surfaces are wetted. Twirl one end of each dowel in a pot
of glue to wet the dowel well before insertion. Slide dowels in gently, and allow time for
excess glue to rise around the sinking dowel. Doweling done properly like this are
Fabulously Strong.
Wipe away excess glue, then leave all alone for a few says for all to cure and DRY.

16. PLANING AND SANDING. The box will look messy, with plywood edges and corners
untidy, and dowels partially extending outwards. Use a panel saw to cut all dowel ends
flush with panels. Rounding all corners may be done initially with a hand held
electric planer. You should have enough experience to plane off corners with course
facets around a curve. The facets may then be planed further with a non-electric hand
plane to make facets much finer, and to make sure butt joints are nicely flushed.
18mm to 12mm radius rounding to all corners is enough except for the top
part of the front panel where the midrange and tweeter is located. So one can increase
rounding radius of 8mm at the bottom of front panel to become up to 33mm radius at the top
of the front panel all around the tweeter.
Once you have planed it all, then comes the sanding. Hand sanding is the best, and
I suggest you have a wall plasterer's hand grip sanding tool to which one can clamp
fine sanding paper. The trick here is to use some 3mm foam sheet between the
sandpaper and the tool plate, and when sanding curved corners the sandpaper
will wrap around the curve and remove all facets left by planing. With care, and the
use of increasingly fine sand paper up to 800 grit size, you should get the most
beautifully smooth and flawless finish, like the shoulder of the Danish Goddess.

17. SPEAKER HOLE REBATES. Most hi-end speakers have the speaker drivers neatly
fitting into a shallow recess around the driver holes, called a rebate. It looks pretty, but
does nothing to improve the sound, and where I have used SEAS drivers I have not
bothered to rebate driver holes and thus fit drivers so their outermost metal flange
is flush with timber. SEAS flanges are fairly thin, and look tidy, so thus rebates are
not necessary. If you are going to rebate for the drivers, now is the time, and you
will need a very steady hand with a router, or perhaps a curved chisel, and a very
careful use of sand paper to ensure all looks perfect after finishes are applied.
The drivers will need to be tried in you cut outs to ensure they will fit OK allowing
for compressible 3mm plastic foam. Using routers or tools over sanded surfaces
requires you cover around the holes with masking tape to prevent stray damage.
The better you want the finish, the more you need to think ahead and the harder
you have to work and more time you take.

17. FINISHING OFF. If you have done an exceptionally fine amount of work with
plywood, then you probably will have open timber grain and stray gaps and holes.
I suggest some turps based grain filler to be rubbed in with a fine cloth, and
the filler color should match your timber color. Excessive smearing of filler must
be avoided, and surfaces rubbed clean as filling proceeds, so that only
open grain and gaps are filled. Boxes should be left alone for a couple of days
for filler to cure.  Boxes can then be dry sanded with 800 grit to remove any upstanding
wood or fibres. If all looks well, and no more filling or sanding is needed, then semi-gloss
polyurethane varnish may be applied with a fine new clean brush.
Make sure polyurethane is thinned  with 20% white spirits. 5 coats are recommended,
with 3 days between coats and fine sanding with 1,200 paper lightly to remove surface
fur between coats. A dust free environment is essential, so apply varnish late at night in
the workshop. The final surface is allowed to harden for a few days. The surface may
be further rubbed up with the finest steel wool you can find plus some danish furniture
oil which should not dissolve the applied varnish. Use fine clean cloth to rub off excess
oil and you should have a very good surface.

Use the WinISD to confirm drivers chosen will work OK in box volumes.
When using say Peerless 5" 831882 as a midrange for F above 150Hz,
there is no need for a large critical Vb for best ported bass performance
and closed box design is OK. As the closed box size is reduced, the
resonant Fo of driver in the box rises and could be 90Hz.
The top chamber Vb of about 7 litres should work OK and should be filled
with high density polyester wool which is normally used for acoustic damping
in timber frame walls. Lower density insulation may be used but packed tight
enough halve the loose volume. 

The bottom chamber is about 47 Litres allowing for ports and braces etc,
and about right to get a good bass response from many modern 8" dia
speakers such as the Peerless 831868 or 830869. The wool filling should
be light density and fill should not be crammed in but about 1/2 fill the
ported chamber without obstructing the port opening. It should be secured with
a few staples and threaded up around the braces of the enclosure.

Crossover filter design is at  Loudspeakers 3, Crossovers.

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