It could be that you’re like me, and like a bit of bass. The HD600 doesn’t have much at all (fight me Senn fans) so you keep turning it up to get some impact until the upper midrange starts to hurt you.

Try a little bass shelf and see if your experience doesn’t improve.

(it won’t solve the soundstage issue with those headphones, however)

You could try gently with a credit card wrapped in a tissue or similar, but the risk of scratching the veneer is real, and considering how great the condition is on these I think a less sharp, more purpose made implement would be better.

Cap replacement on a speaker this old is probably a good idea - the crossover is just first order I think so not at all intimidating to work on.

I am quite jealous TBH. Lovely speakers you have there.

Having worked retail for 20 years (electronics stores, bike shops, book shops, groceries), I can tell you there are 4 types of retail assistant:

1. enthused and empathetic and genuinely trying to help you
2. just getting by, trying to earn a living, largely indifferent
3. jaded grizzled types whose filter has been completely eroded, if it was ever there (usually the final state of type 2)
4. testosterone-fuelled borderline sociopaths who would rip your head off and slam dunk it in the till for a sale, and whose attitude to you will turn in a dime based on whether or not you are going to buy something ‘worth their time’.

Retail, sadly, tends to reward the fourth type only.

It should default to Stereo, which will just output to the front L&R speakers, maybe your sub.

Marantz typically have 3 modes that might apply for phono - Stereo (2 channel with some processing), Direct (whatever channels on the input are output unprocessed, other than phono stage stuff in the case of the phono input), and Pure Direct (same as direct, but all the video circuitry is turned off also).

All Channel Stereo, and potentially some of the surround modes (Neo: whatever) may create a centre channel out of the existing stereo signal and output it through that centre speaker, which you don’t want. Basically, if there’s no audio on the centre when you play a record, that setting is fine.

From memory, the receiver should remember the processing mode last used for each input.

I was going to say, “hey, don’t put the turntable on the same surface as a speaker”, but then I realised it’s fine as long as you’re not in ‘All Ch. Stereo’ when playing records. So, don’t mind me, I’m just having a molasses brain day.

My OG setup was a Marantz Receiver and KEF towers (Qs, because I couldn’t spring for Rs at the time). Still have the KEFs. They make a great speaker. Looks like you’re all set!

Also, yes, excellent dog, would pat.

Depends on the speaker and the room. If the speaker is near my kid, grille on. If the speaker has an exposed or vulnerable/delicate tweeter, especially if it’s a dome that’s proud of the baffle (hello Dynaudio), grille on. If the tweeter is recessed, has a guard, is horn loaded, or is a straight up horn+compression driver, usually grille off, unless the speaker is too bright-sounding.

Everyone likes to laugh at audiophile nonsense, until it’s their specific brand of audiophile nonsense.

A sub like that would just devolve into very long arguments between defensive people about ‘not very crazy, maybe plausible but probably not worth it’ stuff.