The material

The Bremen 3D8 loudspeakers are moulded in a highly durable plastic called Dicyclopentadiene DCPD. The moulding process is called R.I.M. Reaction Injection Moulding. DCPD is widely used in very demanding environments.

Some examples:

• Volvo trucks total front part is moulded in one piece with DCPD.
• Caterpillar’s very large and three-dimensional hoods for its excavators.
• Large body panels for agricultural tractors and buses.
• Swimming pools because DCPD does not oxidize.

DCPD does not crack when being struck by mechanical shocks such as polyurethane or other plastics do. Therefore it is sometimes called steel plastic. The high durability and high internal damping of DCPD together with a high density makes it the perfect plastic for the Bremen loudspeakers.

The Moulding process

In the moulding process DCPD is in the form of a two component liquid plastic with a catalytic system split into two parts. One two specific parts of the catalytic system are together with DCPD but split in two containers, each with a different compound. Both the DCPD monomer formulations are mixed together in a mixing head and then injected into the moulding tool where the curing will start leading to exothermicity with temperatures up to 270°C.

The temperature is controlled within one degree C by liquid cooling channels in the tool. The moulding process for Bremen Loudspeakers takes place in a closed tool at medium fast cycle times, typically from 8 to 10 minutes to maintain best quality moulds. The plastic has approximately the same viscosity as water and therefore DCPD easily fills in all the small spaces in the moulding tool. Out comes a perfectly shaped durable Bremen 3D8 loudspeaker part.

TECHNICAL SPECIFICATIONS

Wall mounted 2-way vented port (bass reflex).

Dispersion: Half sphere 2π from the wall.
Vented port tuning frequency: 36 Hz.
Frequency response: 35 Hz - 25 kHz mounted on wall in room.
Bass/midrange: One 5½” long-throw Midwoofer with titanium voice coil former with symmetric air ventilation.
Treble: Two 1-inch soft dome Tweeters with silk fabric diaphragm and a unique 30μ Titanium voice coil former with symmetric air ventilation.
Tolerances: Bremen 3D8 loudspeakers are matched to be virtually identical in each matched pair, with a frequency response tolerance within ± 0.5 dB.
Sensitivity: 88 dB SPL (2.83 V/1m).
Nominal Impedance: 4 ohm. Very smooth impedance curve above 200 Hz.
Recommended amplifier power: 30-500W per speaker.
Wall Brackets: Included is a Hangman wall bracket with a built in groove for the bubble vial.
Connection terminals: Gold plated binding posts.
Maximum Dimensions: cm (inch”); Height: 54.5 (21-½”), Width: 37 (14-½”), Depth: 17.5 (6-⅞”).
Net Weight: 10 kg (22 lbs).
Colours: Shell: Tuxedo White. Soon to come: Piano Black, Silver Grey, Swedish Bronze, Italian Red.
Back Side: Orange colour with soft lacquer.
Front cover: Black fabric. Soon to come: Light Grey fabric.