Something in prog rock from 1972  Must be in sync with your mind Dave    Artist - Emerson, Lake & Palmer  ‘Title – Trilogy  

As far as the hissing sound- keep the amp on but shut off your source-CD, stream, MP3, whatever. If the sound disappears, it's your source device. Try it with all your sources to see if it's isolated to one or more sources.   If the sound remains even after all your source devices are turned off, then it's your amp, receiver, etc.   The reason you may hear the sound from the rear of the enclosure vs. the front is, the cavity of the enclosure acts like a horn itself, amplifying the sound. Since  you don't hear it from the front, I don't see anything to worry about.   As to the tweeters, you could disconnect the wires to the tweeter (pay attention which wire connected to which terminal so you can reconnect them properly) and put a voltmeter across the tweeter terminals. It should read roughly 8 ohms. If they read a very high number or no number at all, they're toast.   You could then connect your voltmeter, set to AC volts, and attach the leads to the wires you disconnected from the tweeter. A pair of clip leads really helps here. Play some music and watch the voltmeter. It should bounce all over the place in response to the music. Watch the numbers and turn up the volume. The numbers should go up. Cool, right? It means the signal is getting to the tweeters.

"Suitable for use in: Klipschorn, LaScala, and Belle - ONLY with my CT120 or CT125 Tweeters"

You've been a member since 2016 and this is your first post? You'd do well in the Marshmallow Test. I know where one KV-4 is.  I hate shipping large cabinets. What is your location? 

All corners. Source is BluOs via the NAD

My name sake is on the cover  Indi band - The National     

Chill...   One amazing song right here.  So many are clueless...  Nice read under the youtube post.  Back in 1905 they were one of the best shows out there.  Relax and let it ALL go!  Their quad show in Cleveland @ Municipal Stadium was totally amazing.  One the best rides I EVER took.  😂      

Ugh...  MORE piles! 

Looking for a center channel KV-4. I see one on ebay right now but would like to find one with known history.