Infinity - RS 4000 Speaker set

The Infinity RS 4000 USA.
They are vintage 3-way passive speakers—classified as large bookshelf or monitor speakers—introduced by the American brand Infinity in the 80's and manufactured until 1990. They are highly regarded in the classic hi-fi world for the excellent quality and clarity of their high frequencies.
Technical Specifications: Driver configuration: 3-way sealed enclosure (acoustic suspension). Tweeter: EMIT K electromagnetic ribbon (a signature feature of Infinity's high-end range). Midrange: 3.5-inch (6.5 cm) polypropylene cone. The 8-inch (20.3 cm) polypropylene woofer has been upgraded, replaced with superb, brand-new Visaton WSP 21S drivers (see specifications*)
Frequency response: 45 Hz – 45 kHz (±3dB). Crossover frequencies: 800 Hz and 3500 Hz. Sensitivity: 89 dB at 1 watt / 1 meter. Nominal impedance: 6 ohms.
Recommended amplifier power: 25 – 125 watts RMS per channel.
Dimensions: 57 cm x 31.75 cm x 26 cm (Height x Width x Deep).
Without a doubt, the key highlight is the EMIT K ribbon tweeter—the model's crown jewel. It delivers incredibly crystal-clear, detailed, and extended highs that far surpass most conventional dome tweeters of that era. Truly impressive.
Acoustic Performance: Thanks to their solid, sealed enclosure design (lacking a rear bass-reflex port), the bass they produce is extremely fast and precise—unsurpassed for genres like jazz, classic rock, and acoustic pop—while still holding their own against the deeper low-end reach of reflex-ported designs.
* Technical Data: Woofers Visaton WSP 21S
Amplitude & Impedance Frequency
Rated power 100 Watts
Maximum power 130 Watts
Nominal impedance Z 8 Ohms
Frequency response fu – 8000 Hz
(fu: Lower cut-off frequency depending on cabinet)
Mean sound pressure level 91 dB (1W/1m)
Excursion limit 19 mm
Resonance frequency fs 28 Hz
Magnetic induction 1 Tesla
Magnetic flux 1100 µWeber
Height of front pole-plate 8 mm
Voice coil diameter 5 cm
Winding height 1.6 cm
Cutout diameter 18.5 cm
Net weight 2.3 kg
DC resistance Rdc 5.7 Ohms
Mechanical Q factor Qms 3.86
Electrical Q factor Qes 0.3
Total Q factor Qts 0.28
Equivalent volume Vas 80 L
Effective piston area Sd 213 cm²
Moving mass Mms 26 g
Force factor Bxl 9.3 T·m
Voice coil inductance L 1.2 mH
It stands out for incorporating a polypropylene cone with "nawi" geometry, specifically designed to provide high internal damping and reduce distortion at critical frequencies. It features a voice coil on a Kapton former and a ventilated magnet system (drilled pole core), which optimizes heat dissipation and allows for continuous high-power operation.
Everything is in superb condition, both cosmetically and in terms of operation.