What is a good substitute for "echoey"?

As in "an echoey room". People do use this word in speech, but it isn't proper in writing. I thought of "echoing", but that implies that something is currently making an echo, whereas what I'm looking for would mean that if there was a noise in the room, it would echo. Are there any real words for this?

Reverberant - having a tendency to reverberate or be repeatedly reflected; "a reverberant room"; "the reverberant booms of cannon".

The other word I've seen used is "live" or perhaps "lively", used as a direct opposite of "flat" or "dead" (used in a musical or acoustic context).

Aside from "echoey" itself and "live" (as @BradC suggests), I might use "resonant".