Harman Audio offers the JBL Reference 510 Over-Ear Headphones in Gray, model no. JBLREF510BLK-H, for $149.95. Coupon code "29REF510" drops them to $19. With free shipping, that's $131 off list and the lowest total price we could find. They feature 12Hz to 28kHz frequency response, 123dB sensitivity, and folding ear cups. Deal ends May 10.