Tributaries 2S-010D 1-Meter Series 2 Subwoofer Cable All Series 2 audio cables are assembled by hand in Orlando, Florida. The Series 2 Subwoofer Mono cables are designed to work in Low Frequency Effects (LFE) Subwoofer outputs of a pre-amp or receiver. Series 2 uses ultra-pure oxygen-free copper (OFC) developed specifically for audio applications. Since stranded wire supports higher frequencies and cause distortion, Series 2 uses a single solid-gauge wire chosen to support low frequency bass signals.