I just bought a super nice pair of Altec Model 18 studio Monitors.These have the 604 8H drivers.One speaker is working properly.The other has no HF.The diaphragm looks good and the wires are not broken.GPA said there was a tweeter in the HF section.I thought they were a two way.Also they are no where near published effeciency. of 100 db.My cornwalls play twice as loud almost although not as clear.I really want to get these going,beecause I know what they are capable of.