Loudspeaker Materials

Baltic Birch plywood is a top-class plywood with good hardness, strength and stability.
These attributes are important to our use in furniture and loudspeaker cabinets but are also
the main reason why the plywood is expensive in the market place. There are cheaper but
inferior materials we could utilise but that would defeat the objectives that we are striving
to meet.

Traditional plywood is made up of veneers, generally quite thick with the cores made of softer
materials than the face and with internal voids. All layers of Baltic Birch are actually veneers
of Birch. They tend to have a thick outer veneer and a void free core made up of 1.5mm
veneers. As a result, you get clean dadoes, rabbets, dovetails, mitres and fingers for strong,
and when appropriate, great looking joints. As the core is free of voids, your joinery also
won’t suffer from glue starvation—they’ll get 100% glue coverage. Anything you build out of
Baltic Birch should last a good, long time.
The sheets are made of many more layers and being cross-banded layers of approximately
1.5 mm thick Birch the sheets balanced, which promises a flatter product.
One of the fortunate benefits to Baltic Birch, too, is that you can leave the edges exposed if
you like the look. 

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Baltic Birch Plywood comes in numerous thicknesses and we make use of most of them
when necessary.
The sizes are:
3 mm (3 plies)
6 mm (5 plies)
9 mm (7 plies)
12 mm (9 plies)
15mm (11 plies)
18 mm (13 plies)
21mm (15 plies)
24mm (17 plies)
30mm (21 plies)
38mm (28plies)

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Baltic Birch Plywood also comes in several grades. We only use the better grades as we
require an attractive finish to the wood and anything that we make from it. The grading for
Baltic Birch is established by the Russian intergovernmental standard GOST 3916.1-96.

Grading is given as the two outer faces of the plywood, in the format of front/back. For
instance, Baltic Birch with a “B/BB” grade would have a B grade front ply, and a BB grade
back ply, where B is slightly better than BB.

The grades are:
A: Nearly perfect and flawless face veneer ply. This grade is no longer available
commercially. (Also designated grade “E” according to GOST 3916.1-96.)

B: Generally uniform light colour, with no plugs, or open cracks/splits. A limited amount of
pin knots, and minor colour inconsistencies are allowed. (Also designated grade “I”
according to GOST 3916.1-96.)

BB: Generally uniform colour, though colour variations/stains are allowed. Limited number
of plugs, cracks/splits, and unlimited amount of pin knots allowed. (Also designated grade
“II” according to GOST 3916.1-96.)
There are several more categories of inferior plywood but we are not concerned with them
as they are not suitable for the products we make.

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Sheet weight:
3 mm (3 plies) 13.15Kg
6 mm (5 plies) 19.50Kg
9 mm (7 plies) 25.4Kg
12 mm (9 plies) 32.66Kg
15mm (11 plies) 38.1Kg
18 mm (13 plies) 52.62Kg
21mm (15 plies) 56.25Kg
24mm (17 plies) 59.87Kg
30mm (21 plies) 70.31Kg
38mm (28plies) 83.91Kg

The density has been measured for each size over many samples with the mean value
coming out at around 693.0 kg/m3.

Birch plywood is considered to be relatively homogeneous in terms of the strength
properties, such that even the lowest strength properties are competitive to the strength of
most of the structural softwood alternatives commonly used such as structural lumber C24
or glulam GL 30c. However, these are only ‘strong’ in one direction whilst Baltic Birch
plywood exhibits better ‘strength’ in tension, shear and compression. Moreover, Birch
plywood also exhibits decreased variability compared to the sawn timber in the properties
mentioned above.
The hardness of a timber can be measured and Baltic Birch ply compares well to several
other common timbers used in HiFi.
According to the Janka hardness test, the hardness value given for the Baltic Birch is 5600 N.
Black Walnut, North American Walnut 4,500 N, Cherry 4,430 N

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These qualities make Baltic Birch Plywood ideal for our uses and it is the tensile strength of
the product which lends itself so well to making speakers. It exhibits properties not
dissimilar to that of a stringed instrument under tension.