Nubert Typ 471 A specifications

Category : Speakers

General

Tech nical data

Special equipment

Other (historical) models of the same series: Nubert type 388 (85 W / 45 x 25 x 23 cm), Nubert type 554 (180 W /65 x 36 x 32 cm)

Subject: Aging of foam beads < /b> (Text Nubert electronic 2004)

Since about 1972, the outer diaphragm clamps of bass and midrange loudspeakers (so-called "beads") have increasingly been made of foam instead of folded paper, fabric or rubber, because this material has very favorable acoustic properties due to its internal damping. 5 Years of endurance testing in discotheques did not bring any problems to light, - so almost unlimited durability in everyday life seemed logical. However, it is now clear that all foam beads from the 70s to the mid-80s (mainly depending on temperature and UV radiation) will become unusable after about 13 to 20 years. Most often they "disintegrate", because their mechanical strength (similar to wet newsprint) is becoming less and less. All speaker manufacturers are affected by this problem. In most cases, a bass speaker works perfectly acoustically until a sudden failure; - sometimes even (at lower volumes) better than a new chassis, because due to the softening of the clamping, the resonant frequency decreases and thus deeper basses can be radiated. In principle, it would be possible to replace the beads on the defective speaker systems if the speaker has not yet made any strong scratching noises. However, the sick exchange is time-consuming and not crowned with success with absolute certainty. As a rule of thumb, one can assume that this exchange is only profitable for "exotic" woofers that cost more than about € 100.- and for which there is no longer a supply of spare parts. For several years now, there have also been repair companies that have specialized in replacing the beads (with a membrane). However, one can assume that the sound differences are rather greater than is the case with the replacement types recommended by us. Since we have recognized the aging of foam beads as a problem, we only use loudspeaker chassis with special rubber beads, which, however, require more complex crossovers in order to achieve equally good acoustic properties in the transition area to the tweeter. For repairs of our previous box models with foam beads, we use the special silicone-coated successor types, which have only been available since the beginning of the 90s, and which, according to the manufacturer, should last "forever". After lengthy series of experiments with regard to "artificial aging" (in climatic chambers and with different infrared and UV irradiation), we assume at least a 50 % longer service life (20-30 years). For some speaker models, we can also offer a replacement with speakers with rubber beads, which are almost indistinguishable in sound (even without changing the crossover).

• Manufacturer: Günther Nubert electronic GmbH Schwäbisch Gmünd
• Model: Type 471 A
• Years of construction: 1980/81
• Manufactured in: Germany
• Color: Walnut (veneer + corner sticks)
• Dimensions: 585 x 315 x 275mm (HxWxD)< /li>
• Weight: 14 kg
• Factory price approx.: 405.- DM

• Type of construction: Bass reflex
• Chassis:
  • TT 205mm
  • HT 106x82mm (25 mm dome)
• Load capacity: 100 watts
• Efficiency: 86 dB / 1 W / 1m
• Frequency response: 42 - 18,000Hz +- 3 dB (at beam angle 30°)
• Transition ranges: approx. 2 kHz
• Impedance: 4 643961b8da111c0a15d770a1109a86d4s

• TT 205mm
• HT 106x82mm (25 mm dome)

• Height adjustment switch

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