OO1

Yamaha A-S 801 AB Class ( as low as 700$ brand new on Ebay ) , same specs / 1/2 the price of a D Class NAD C 3050 https://usa.yamaha.com/products/audio_visual/hifi_components/a-s801/specs.html

the serial numbers you provided are 2 different Heresy speakers with each Heresy speaker housing a different set of drivers and crossovers - the 1st serial # 8508682 is a 1985 Heresy , the 2nd serial # 65S781 refers to a 1978 Heresy ,

Klipsch part # 127123, ......OEM equipment CW- Forte-Heresy III / IV , cost is on par with aftermarkets

stick with the 400 , the connect app has been a source of software issues

Replacing the Power Supply will in most cases resolve the issue / AC to DC Isolated Power Supply Module DC 24V 4A 5V 1A Dual Output Power AC 120V https://www.amazon.com/NOYITO-Isolated-90-256V-50-60Hz-Industrial/dp/B07WKH5RZV?th=1 .https://www.amazon.com/dp/B07WKH5RZV/ref=srdp?keywords=noyito+ac+to+dc+power+supply+24v+5v&srpt=POWER_CONVERTER&sres=B07WKH5RZV%2CB07T9PJ9D7%2CB07BDL176B%2CB07JV7CN1T%2CB07C1JHBB3%2CB07CNTHTSP%2CB07FNFJTHH%2CB0816B34FR%2CB07CML2GXN%2CB081RGVJGD%2CB06XJVYDDW%2CB07BLTTX1W%2CB07C8R5PJD%2CB07HWP4TSX%2CB07G6J3PK1%2CB07BLQKW37&qsid=135-3283479-4546535

yet , they're not too far apart , if properly recapped with a revised power supply .

dust caps and black speaker cement glue are sold on Ebay in various sizes , most new dust caps have a lip , buy a pair since the new dust cap may not match the old dust cap on your 2nd speaker , use a hair dryer to melt off the glue and peel off the old dust cap if you're not comfortable using a precision knife , and gently does it .

scam Alert

M-5000 features low distortion up to 100 kHz,, stable at 2 Ohms @ 400 wpc ,C-5000 preamp runs on 2 discrete book matched circuit boards with 2 transformers , the AL-5 will do just fine

good to know

the 600 was discounted at very low prices , and it shows as sold out https://www.klipsch.com/sound-bars

city location ?

try doing a Factory Reset vs updating the Firmware https://support.klipsch.com/hc/en-us/articles/360051253192-Cinema-1200-Factory-Reset

WOW , the Chiefs have a Dynasty , unbelievable , seconds from losing and they win the SB

ok

1984 , last year of production for the Heresy 1

used klipsch parts can sell very fast if the price is right , for top dollar Ebay.....USAaudiomart.com

did you take out the tweeter ? we can do a few tests

......

nope , 2 dB less efficient if that

says who ?

grab the good tweeter and test it on 2 crossovers with music playing at low level , does it work ? yes both networks are A1 - if the good tweeter does not work on 1 of the 2 networks , you have a bad network you can do the same test with the 2nd tweeter to confirm. - However....... if 1 tweeter fails on both networks , you got a bad tweeter diaphragm https://reconingspeakers.com/products-page/klipsch-k77f-127126-diaphragm/

no affiliation https://www.ebay.com/itm/325823258608?hash=item4bdc945ff0:g:yesAAOSwo71lDdjc&amdata=enc%3AAQAIAAAA8FORaIgEinx9ZqKtBYNZCkzxsioc39jB15FfefHc4oVKJ2mRTfzXtrIcoCxALJ5rwEGK%2Fvq0uXw6CGHIV%2FvQBPXX13Y6v%2FPAEKc6yaHC6dSUkpDAVUt3bh%2Bm11M10lSZib%2BRK%2B0WAMwxKsVC%2FdmRnADFEsvw9xKlT6d1vdfJTqRKuC7kZv2F8RG8Txq38miCPufsfT2JUNL9N0DSAxMypYLTHpG%2FoOckjd2v0ZwJnGt2CpTC3PGOHChw8JxmsytFE34BfFsarGWFzUfF4iXj4I1s3xYV0ckw8z3%2BlMg%2B%2BkyNMFC8yl6pr%2FWCz%2BcFVhc36g%3D%3D|tkp%3ABk9SR8yikIeyYw

great price for 1982 Heresy 1's