Mike,
I owned DQ10s in the mid 70’s. Mirror imaging is a good thing. Drivers outside in my room back then. YMMV. I like to set coherent speakers toed in slightly so they align about 1 foot behind my head. In a narrow room w reflective walls next to the speaker, drivers inside and firing straight back may be preferred.
Ditto pzo tweeter replacement. IMO, they sound better up off the floor and less angled than the stock feet. Today, I’d add a pair of subs, probably XO ≈60-80Hz, depending on the room. Definitely recap with PP to get rid of the electrolytics, ceramics. I don’t remember the details, but I changed the woofer XO / damping / ???. You might be able to turn up something similar.
IIRC, I had Ampzilla, maybe a big Yamaha, but also listened with several amps belonging to friends. The original 405, APT 1 & other era of similar power drove the DQs easily.
As far as recapping the 405, the service manual is available @ HiFi Engine
https://www.hifiengine.com/manual_library/quad/405.shtml
The parts lists does not indicate the capacitor types. Any ceramic, mylar should probably be upgraded with PP or PS. The WIMA MKP are well regarded PP https://www.tawelectronics.com/wima/WIMA_MKP_10.pdf
Our caps dry out, our resistors drift, ours tubes fade...
I owned DQ10s in the mid 70’s. Mirror imaging is a good thing. Drivers outside in my room back then. YMMV. I like to set coherent speakers toed in slightly so they align about 1 foot behind my head. In a narrow room w reflective walls next to the speaker, drivers inside and firing straight back may be preferred.
Ditto pzo tweeter replacement. IMO, they sound better up off the floor and less angled than the stock feet. Today, I’d add a pair of subs, probably XO ≈60-80Hz, depending on the room. Definitely recap with PP to get rid of the electrolytics, ceramics. I don’t remember the details, but I changed the woofer XO / damping / ???. You might be able to turn up something similar.
IIRC, I had Ampzilla, maybe a big Yamaha, but also listened with several amps belonging to friends. The original 405, APT 1 & other era of similar power drove the DQs easily.
As far as recapping the 405, the service manual is available @ HiFi Engine
https://www.hifiengine.com/manual_library/quad/405.shtml
The parts lists does not indicate the capacitor types. Any ceramic, mylar should probably be upgraded with PP or PS. The WIMA MKP are well regarded PP https://www.tawelectronics.com/wima/WIMA_MKP_10.pdf
-- Al (also a retired EE)Al, we never ’retire’.
Our caps dry out, our resistors drift, ours tubes fade...