ProAc Response Four or Operly Intelligence III?

Two very different loudspeakers take turns on one French electronics chain here, the ProAc Response Four three-way tower and the Operly Intelligence III single-driver horn, both driven by YBA's Signature stereo power amplifier. A YBA Signature preamplifier and Signature CD player complete the line and a Thorens TD 1500 adds vinyl. The idea is simple - keep the amplification fixed and let the speaker choice decide the result.

The system at a glance

Six components, counting both speaker options, built around one source pair, one preamplifier and one stereo power amplifier. It suits a listener deciding between a multi-driver dynamic tower and a full-range horn. The Response Four sold for USD 19,000 per pair by 1998, the Operly launched at USD 40,000 per pair. Disc and vinyl get equal weight, with no streaming box in the chain.

Why these components work together

The Response Four spreads five drivers across a ported, plinth-mounted cabinet of about 136 kg, two 9 inch ATC woofers and two 3 inch ATC domes on 75 mm ribbon-wound coils plus a Scan-Speak tweeter. ProAc quotes 89 dB for 1 W and an 8 ohm nominal load. The Operly runs a hand-made full-range driver feeding a forward and a separate backward horn in a glass fibre monocoque, rated at 100 dB and 6 ohm from 41.5 Hz to 17.5 kHz. Against both loads the Signature Stereo delivers 200 W per channel into 8 ohm and 400 W into 4 ohm from a 1,000 VA UI-core transformer, and YBA builds it fully symmetrical with a transistor-only signal path. With 11 dB more sensitivity, the Operly asks only a small fraction of that power, while the ProAc uses the reserve on large bass swings. The Signature CD player reads discs on a Philips CD-PRO M mechanism and sends 4.6 V from its XLR outputs. The TD 1500 floats platter and arm on a sprung sub-chassis and arrives with the TP 150 arm and an Ortofon 2M Bronze moving magnet cartridge.

How it sounds

The ProAc puts a large, weighty floor under orchestral and rock material, its twin woofers and separate bass chambers filling the room. Changing to the Operly moves the focus to voices and small groups, since one driver without a crossover keeps timing coherent, though the 17.5 kHz upper limit leaves the top softer.

Considering a similar setup

The two speakers pull in opposite directions, so the amplifier should be sized for the less sensitive one. A horn-only owner could scale down the power amplifier, while a ProAc owner needs current into the bass section. The TD 1500 can later move up within the Thorens range without touching the YBA electronics.