Rare tweeter used in various Heybrook and Harbeth models.
These compact units feature Neodymium magnets, ferrofluid and are incredibly rare. The 25mm woven textile dome is moderately horn loaded resulting in a good efficiency of 92dB. As to be expected from legendary maker Audax, these sound superb. These long discontinued tweeters are in factory fresh condition & test perfectly to specification ~ they are probably the only ones available anywhere.