I'm sorry to be late to this topic as I recently got a pair of these.
@Swerd – you found two brochures, but from the
@Griz1 answer, I'm guessing he has the same model as me – the closed box Series1 and these state 8Ohms nominal impedance (the coloured brochure).
I've been testing these wioth three different amps that are now at my disposal:
A NAD THX 2700 power amp
Power output: 150 watts per channel into 8Ω (stereo), 400W into 8Ω (mono)
Frequency response: 1Hz to 80kHz
Total harmonic distortion: 0.03%
Damping factor: 120
Input sensitivity: 1.2V
Signal to noise ratio: 122dB
Speaker load impedance: 2Ω (minimum)
Dimensions: 435 x 127 x 395mm
Weight: 13kg
Year: 1992
Hitachi HMA8300
Power output: 200 watts per channel into 8Ω (stereo)
Frequency response: 5Hz to 80kHz
Total harmonic distortion: 0.1%
Damping factor: 50
Input sensitivity: 1V
Signal to noise ratio: 110dB
Speaker load impedance: 4Ω to 16Ω
Semiconductors: 1 x IC, 40 x transistors, 51 x diodes
Dimensions: 435 x 182 x 404mm
Weight: 24kg
Year: 1977
and a
Yamaha AVR RX-V496
Tuning range: FM, MW
Power output: 70 watts per channel into 8Ω (stereo)
Surround output: 70W (front), 70W (center), 70W (rear)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.06%
Damping factor: 60
Input sensitivity: 150mV (line)
Signal to noise ratio: 100dB (line)
Channel separation: 45dB (line)
Output: 150mV (line)
Speaker load impedance: 4Ω (minimum)
Digital inputs: coaxial, optical
Video Connections: composite, SVHS
Dimensions: 435 x 151 x 391mm
Weight: 10kg
Power amps were each with its own pre amp; Hitachi HCA-8300 and NAD C106.
Having them in a medium room, playing almost unbearably high, through an entire new, pop, bass/strings-heavy album, I noticed no difference among the Yamaha and Hitachi amps (being 70 and 200 Wpch/8 respectively) and most notably, didn’t feel excess heat from the Yamaha AVR.
I did notice difference in sound from NAD (but as has been debated here, it might have been expectations), some sort of softness in the midds, let’s leave it at that (it was present with all sources).
I had them on the short wall, playing across the length of the room. I sat 3” from the back wall. In medium size room I’d never think of a sub, which is not all that unexpected considering it’s 4 large woofers in a closed box (49Hz Q – 0.7).
I’ve been interchanging CD albums playing from Yamaha Natural Sound DVD-S795 DVD Player, Lossless files from my Laptop (always with the same settings) and the Technics SL-Q202 TT (which is not working properly so I disregard everything I heard – I wasn’t happy with what I’ve heard)
IMPORTANT: However, none of these were proper ABX simply because I wasn’t trying to prove sound difference among the amps. I wanted to see would I find Yamaha AVR lacking and overheating and I didn’t. But even the heat test was only by hand hooking it up to LS50 and then back to B&W 802. I needed to be sure how much power these need before I give Hitachi to my brother.
@Griz1 I wouldn’t spend too much time/money on a quest for finding an external amp unless it makes you personally happy. An honestly rated AVR anywhere between 100 and 150Wpch/8 will suffice even for prolonged sessions at ear-damaging levels. My father had these in a HT and since they shook the floors, he never went for a sub. Also, that was why he had a THX standard amp.
I gave the Hitachi to my brother and he hates me for it because it is so heavy that he needed to add vertical support under the shelf where he put it.