1. I still can't find it ANYWHERE on your website. I have looked on the product pages, support page (where I thought it would be) and the about us page.
2. I can't see in that Warranty Disclosure where it says if you use the easily accessible menu option and change those frequency settings, the warranty is the void.
I believe that if this is the case, you should be including that in the Warranty Disclosure. And the Warranty Disclosure should be easily accessible via the product sale page and / or the support page.
It would also be courteous to have a warning on the Miner Configuration > Advanced Settings page in the Antminer firmware. Something like "WARNING: Setting the Frequency greater than 200M or Voltage greater than 0725 will void your warranty!"
These are just suggestions to help lessen the confusion of customers. I only know about the warranty because I follow this thread, but a first time user would not expect to look in the forum for it.
Even I follow the thread, there are over 106 pages and counting. I too have not seen where it said changing the setting will avoid warranty. Anyhow, I have clock down from default to lesser since when it gets warm, S4 tend to stop mining and fan speed goes to near 4000 RPM and shakes. So, far at fan speeds below 3300 RPM seemed to be most stable