A typical HTIB generally consists of a central receiver unit which usually contains a DVD player (some systems separate the DVD player into a separate unit), a multi-channel power amplifier and a series of speakers for surround sound use, generally including a subwoofer. Some HTIB systems also have a radio tuner or an Internet-based streaming audio platform (e.g. Spotify). The least expensive systems usually have a passive subwoofer, which is amplified by the receiver unit. HTIB systems do not include a television set or monitor with which to display the visual material or a stand to place the receiver unit on. Beside auxiliary inputs, many of them are equipped today with HDMI with ARC, optical and SPDIF inputs. Some HTIB systems are also equipped with a phono input, to allow the connection of a turntable with magnetic cartridge. However such systems are not suitable for vinyl playing as they are mainly focussed on movies and rarely for high fidelity. Some home theaters are just stereo or 2.1, but even so, they are not intended as hi fi, this is just a marketing strategy.