Note that whether a word sequence such as "heavy + metal + detector" implies a "compound adjective + noun" or "bare adjective + compound noun" depends on the punctuation. For instance, "heavy-metal detector" and "heavy metal detector" can refer to quite different things: "heavy-metal detector" implies a device that detects heavy metals (wherein "heavy-metal" functions as a compound adjective that modifies the noun "detector"). By contrast, "heavy metal detector", without the hyphen, refers to a metal detector that is heavy. "" is a bare adjective that modifies the compound noun "metal detector". Thus, "heavy metal detector" is a "bare adjective + compound noun" sequence.