Projects' Details

How it is built

Image 1: Schematic

Image 2: Overview Inside

Image 3: Front View

Image 4: Back View

Image 5: Damped Wall

Image 6: Tweeter's Cabin

Image 7: Cables' Damping

Image 8: Front Subbaffles

Image 9: X-overs' Cover

Image 10: Parts of Stands

Image 11: Tweeter

Image 12: Woofer

Image 13: X-over' cover opened

Image 14: X-overs' overview

Image 15: High-Midrange X-over

Image 16: Lowrange X-over

Image 17: Plugs

Image 18: Spikes

Image 19: Overview of finish

--------------------------------------- Datasheets of parts:

Datasheet 1: TC120TD5

Datasheet 2: CB17RCY

Datasheet 3: MP900/9000

Datasheet 4: MKP

Datasheet 5: HQ58-46

Datasheet 6: 0,47mH 12AWG

Datasheet 7: 0765E


...My DIY audio world...
92dB CUB


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 92dB CUB 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. After you have seen the 92dB CUB’s first time you will never forget their design.

How it was made

92dB 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 CUB 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 CB17RCY (H404) and Focal inverted dome tweeter TC120TD5.
92dB CUB
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 one loudspeaker.

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 low range.