Being a previous owner of the Nola Viper 1A, (which have been upgraded to the Viper 1X's), the brightness/sibilance you are hearing is most likely RF infiltration into your system somewhere upstream and the speaker is only revealing that problem.
The Vipers use high quality M-caps in the mid/high frequency x-overs so these are not the issue as I experienced very little brightness/sibilance in my setup with the 1A version. The Reference lll AlNiCo tweeter upgrades completely eliminate any brightness and are a huge step forward in transparancy/musical detail and reveal that the stock 25mm magnesium dipole domes can sound forward but this indicates a problem elsewhere as mentioned before.
RF infiltration comes from several places but mainly from poor power isolation especially from digital components and from appliances used in the home/community. If you can, try isolating your digital component(s) with an isolation transformer or a PS Audio UO. In addition, poor/budget quality IC's/Speaker cables will be a factor here as well as the Viper is a very detailed speaker and as such will reveal any shortcomings in the cable chain.
In short, the cleaner your AC mains and the level of isolation with regards to RF will pay large dividends here
and should be given due consideration.
Cheers
The Vipers use high quality M-caps in the mid/high frequency x-overs so these are not the issue as I experienced very little brightness/sibilance in my setup with the 1A version. The Reference lll AlNiCo tweeter upgrades completely eliminate any brightness and are a huge step forward in transparancy/musical detail and reveal that the stock 25mm magnesium dipole domes can sound forward but this indicates a problem elsewhere as mentioned before.
RF infiltration comes from several places but mainly from poor power isolation especially from digital components and from appliances used in the home/community. If you can, try isolating your digital component(s) with an isolation transformer or a PS Audio UO. In addition, poor/budget quality IC's/Speaker cables will be a factor here as well as the Viper is a very detailed speaker and as such will reveal any shortcomings in the cable chain.
In short, the cleaner your AC mains and the level of isolation with regards to RF will pay large dividends here
and should be given due consideration.
Cheers