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At the beginning of the 80th I had the pleasure to hear the famous HQD loudspeaker system from Mark Levinson. It was an active 3 way system with driver components from the companies Hartley, Quad and Decca. Two Quad ESL 57 were mounted on top of each other in a stand which are responsible for the frequencies between 100Hz and 7kHz. The frequencies above 7kHz are reproduced with a Decca ribbon tweeter modified by ML (without the horn) located between the two electrostatic speakers. For the bass below 100Hz two 24″ subwoofer systems from Hartley were used. Some ML LNC-2 active mono frequency crossovers and a couple of class A power amplifiers ML-2 are also part of the system.
I had a strong impression from this great listening experience, especially because I was at that time already an owner of Stacked Quads. When I started with the assembly of my subwoofer in 2008 it was clear for me that at the end I have my own interpretation of the HQD system. At least it became a RQM system with the following components
- RiPol subwoofer with a frequency range up to 125Hz
- Quad ESL 57 in a stacked configuration, frequency range from 125Hz up to 7kHz
- Mundorf AMT 1908c Air Motion Transformer for all frequencies above 7kHz
In contrast to the original system I have a mono subwoofer in use, this is more than enough for my small listening room.
To split the frequencies I have a self developed active crossover with 24dB Linkwitz-Riley filter. For the Quads I use 2× ES4 (XA30.8 clones – one channel per speaker) and for the Mundorfs I take one of my ES2 (Aleph J clone). The RiPol I drive very successful since years with the ES3 (Hypex Class D amp).
All informations to assemble a RiPol you find on my page for this really exceptional subwoofer.
Front View of the Finished RiPol
Meanwhile I operate the RiPol without the passive compensation circuit. The two 30cm drivers are directly connected to my Hypex power amp. The necessary suppression of the resonance frequencies at approx. 300Hz takes place in the SubDSP.