...My DIY audio world...
How the 92dB CUB®
was born? Few years ago I decided to build new loudspeakers. I am
interesting many projects, as made by factory and as well DIY ones.
Finally I have chosen two loudspeakers: Merak of Rockport Technologies
and CUB Specialities of Wilson Audio. I am dreaming about them very
long time. Both loudspeakers have an intrigue design and high
quality drivers. The Merak has fantastic woofer made by Scaanings
and Esotar® tweeter made by Dynaudio. The CUB
uses two woofers made by Seas and a tweeter made by Focal.
Seas’ woofers were made from coated paper and they have a very
high efficiency (91dB). The Focal’s inverted dome tweeter was
made from Tioxid ® and has efficiency like a
tube tweeters: 93,5dB! So finally I have chosen more efficiency
loudspeakers. In this way the
loudspeakers were born. They can work as 2-ways bass-reflex
loudspeakers in d’Appolito configuration or 2,5-ways bass-reflex
loudspeakers in non d’Appolito configuration. They have two rectangular
bas-reflex ports placed on front side between woofers and outside of
tweeter. This configuration was named Center Unitized Bass (CUB) by
Wilson Audio. I first time saw drivers such placed with bass-ports
around. Thanks to the idea they looks very interesting and unlike
to other loudspeakers on the mass-market. Thanks to that front
ports, low frequency is not such depends on room wall like in
other loudspeakers with ports on back side. The back side of them
looks very intrigue too. There are two big cubic boxes include
crossovers. High and midrange X-over is placed in upper box
and lowmidrange one is placed in lower box.
you have seen the 92dB CUB’s first time you will never forget
How it was made
CUB® has an interesting feature:
as I wrote above it can work as d’Appolito and as well non d’Appolito
configuration. The configuration depends on used crossover type only. I
have chosen non d’Appolito configuration because vertical position of
listener less depends on position of loudspeakers. The non
d’Appolito configuration has a bit lower efficiency than d’Appolito
(0,5 dB) but give better positioned pole of good listening.
Designing the 92dB
I based on description placed on Wilson
Audio website and on Tony Gee
website about The Proteus project. Tony Gee used two Seas woofers
CB17RCY/P and Seas dome tweeter
Excel T25-001. In Wilson Audio’s loudspeakers were used two Seas
(H404) and Focal inverted dome tweeter TC120TD5.
So I used the same driver as Wilson Audio done. A crossover was based
on Tony Gee’s schematic but I had to change few components to adapt the
crossover to different tweeter than used by Tony Gee. Both types of
woofer have the same diameter but the tweeter is completely different,
so I changed a hole to fit it (instead round hole I made rounded square
one). I designed the same dimensions of cabinet like Wilson Audio’s
loudspeaker but different than Tony Gee done. And I fitted on back
panel two boxes with crossovers inside like in the Wilson Audio’s CUB.
My idea was to build a clone of the Wilson Audio’s CUB. Of course
it was impossible because Wilson Audio using a special composite
(phenolic resin) material for cabinets in his loudspeakers.
My the 92dB CUB®
was made of 22mm thick HDF and 30mm thick MDF. From 22mm HDF were
made both side panels and all internal baffles and brackets. This
material was used to made two front baffles for 17cm mid-woofers
too. Thicker MDF was used for bottom, top, front and back panels.
A back sub-panels with two boxes were made from 10mm thick MDF.
I used 5 internal brackets glued to back panel (3 pcs) and one
in lower chamber and one in upper chamber of woofers, glued to
both side panels. All these brackets have two 50mm holes for free
flow of air inside. Four baffles were glued between woofers
in shape H giving a closed chamber for tweeter and two symetrical
bass-reflex ports. All HDF/MDF baffles were glued using Soudal type
100A tubed glue only (I have not used any screws to join elements
of cabinets together). Screws were used to fit front baffles,
drivers, X-overs and back sub-panels only (with a special crown
nuts). All internal surface of woofers chambers were covered (glued)
by 100% wool carpet except bass-reflex ports, of course. Space in
back of woofers was filled by chopped foam and sheep wool. Back
plate of tweeter chamber was drilled of 10mm holes and filled by
special anti-resonant bitumic mass and covered by the same wool
carpet. Space of tweeter chamber was filled by the chopped foam
and sheep wool too. Back wal of tweeter was drilled in 10mm deeep
and all holes were filled by bitumic mass. Between front baffles
and main front panel was fitted 2mm cork mat. The same cork mat
was fitted between back side panel and sub-panel. All holes for
screws were drilled before any panels were glued together. All
wires were winded by foam in all places where they have contact
with cabinet, to avoid any resonances. After mountage, both
complete cabinets (without sheep wool and drivers) were painted
by 3-layer car varnish (first base varnish, next colour varnish,
and last transparet shiny varnish). All external surface was
polished, like a car body. After that I mounted double speaker
terminals on back sub-panel on polished small aluminium
plate. Next I soldered X-overs on two separated 10mm thick MDF
mini-panels and after screwed drivers I soldered internal wires.
Next I made a special stands for both loudspeakers. An upper plates
were made from 5mm aluminium sheets and bottom plates were made from
two 22mm thick MDF plates glued together with big rectangular
depressions on low surface for 20mm thick granite plates (as a
ballast). Both granite plates were glued inside
the rectangular depresion. Upper and bottom plates were join by steel
60mm diameter pipe screwed together with two aluminium rings by long
6mm diameter threaded steel rod, to get maximum stiffness and rigidity
of the stand. The steel pipes were filled by dried beach sand.
As cabinets as well stands were equiped with steel cones
as legs. To avoid moving cabinet caused by vibrations, upper plates of
stands have a special 8mm diameter screws joining stands with cabinets.
Stands and back sub-panels were painted with black mat car varnish.
All screws are Bulten non-magnetic and non-rust ones
with special unscrewed nuts (with plastic ring inside or crown
for wooden constructions). One loudspeaker weight 24 kilos and
stand weight 12 kilos, so it gives 36 kilos of total weight per
I used follow wires: the Klotz LaGrange OFC Cu 2x4mm2 for bass woofers,
and the Van den Hul The Clearwater Silver Coated OFC Cu 2x1,97mm2 for
mid-woofers and tweeters. As terminals I used screwed gold-plated
terminals similar to WBT ones. Wires were soldered by Pb-free WBT
solder tin. A schematic of X-over is on left submenu. I used
follow electronic components: 30W Caddock MP930 resistors
(case TO220) fitted to radiators, SCR foil MKP 250V capacitors,
Alpha-Core 12AWG Cu tape air-chokes for mid/highrange and Intertechnik
ferrite-chokes (with resistance lower than 0,15 ohm) for