I finally got around to getting a Bluetooth speaker for bird photography. I went out to my bittern spot to test out the low frequencies on it...the bittern has a song with lots of "bass"....a great test for it (although I already knew from testing in the store). Well, turns out it works just fine indeed!
Canon 7D + 500mm f/4 II, manual exposure, evaluative metering, 1/3200s., f/5, ISO 400, natural light, handheld, more than FF (added canvas right and below - the bittern came in quite close), audio used.