Hi, Yes, they are Quad 989s. I am using them for ambiance retrieval. Let me explain: Back in the early 70s, while in college, I had a “Quad” system with Tannoy 15″s in the front and 10″s in the rear. I was using a Marantz 7C and Marantz 9s in front and 8B in the rear. I was using an EV SQ decoder as I recall for the rear channels. Quad was being pushed, but there were not many Quad recordings but the decoding, as the simpler Hafler DynaQuad circuit, did a good job of pulling out the ambiance information and sending it to the rear. If properly set up it was subtle but excellent. I eventually replaced the Tannoy Quad set up with KLH 9s driven by Futtermans, and that clearly sounded better, even in plain stereo.
Fast forward to 2003. I had Quad 989s. They had replaced Martin Logan CLSs, which I still had in my storage area. I was speaking one day to Dave Gordon of Audio Research who brought up the ARC SDP 1 to me. This was a unit which had basically a line level Hafler circuit along with an adjustable digital delay line. It was originally intended to get ARC into the home theater market, and failed miserably at that. But Dave mentioned that he had a few friends that were using it in very high end music systems to extract and deliver ambiance information to the rear. I located one, set it up, with the Quads in front and CLSs in the rear, and was not overly happy and abandoned that project, but kept the SDP 1. As I found out later, I had not set the system up properly, using too much delay and having the level of the rear speakers too high.
Again fast forward to the summer of 2020. I had retired from GoldenEar and with the pandemic, was basically hunkered down in Maryland, not exactly bored, but looking for projects. For whatever reason, I thought I would try the SDP 1 again: nothing ventured, nothing gained. I spoke with Dave about it and he forwarded me some set up tip info, and I set it up again, this time with the Ultimate 845s in the front (which I love) and the Quads in the rear. The rest of the system is an Acoustic Signature Ascona turntable with Kuzma 14″ FourPoint arm and Lyra Etna cartridge, Channel D Lino C current based phono preamp, PS BHK preamp, PS BHK mono blocks, Atmosphere amp in the rear. As you can see, I listen very nearfield, maybe 7.5-8 feet from both the front and rear speakers.
And the sound is extraordinary!!! As I mentioned, the level of the rear speakers should be very low: you should not be able to identify discrete sound coming from them. Having the ambiance recovery speakers in the rear helps to take the room out of the equation, and overall the effect, if you want to call it an effect, is to improve the three dimensionality of the front soundstage and overall give a more relaxed and natural musical sound to the presentation. I wonder what the system would sound like if I dug out my old EV decoder and put it in the system? And clearly, what the SDP 1 is doing could be done better with updated technology. Here is a link to an article that Gordon Holt wrote about the SDP 1 in 1995 which helps give more insight. https://www.stereophile.com/tubepreamps/844/index.html