Just had an old school Zapco Ref 100.4 installed running a set of Morel Hybrid components active. Told the installer the HU (pioneer 4200nex) had more than sufficient crossovers to do the job. I acquired the equipment. I thought, being a zapco dealer, the installer would have the required symbilinks, and gave him the only one I had. He asked the local zapco sales rep to bring him one. Next day, installer told me zapco rep failed to bring one, so still one short, but he'd "make it work". Later that day, I was told car was ready. When I picked up car installer had gone home. Everything seems to work, but I'm a bit of a noob. How can speakers (2 mids & 2 tweets) be running active from the 4 channel zapco with only a single symbilink? Aren't symbilinks required on that model....meaning you can't sub in rca's instead and still be running a single driver per channel?