Will the sound quality deminish over the years?

"11-09-14: Phasecorrect
Hate to be a buzzkill...but FM frequency cuts out @ 15 kHz...so the improvements attributed to the Nad are largely imaginative...that said, its a very good tuner."

"11-10-14: Mceljo
Nonoise - I like how your perspective shifted from the Marantz lacking the highs to it adding mid and bass. The change in perspective caused you to no longer think of it as not sounding as good as the NAD. Now that your assumption has changed for the Marantz, you will likely enjoy it rather than wish it sounded like the NAD. You may still prefer the NAD, but I am fascinated by how our brains work."

Why the assumption that the change is imagined? That's pretty far fetched. He listened to the NAD tuner on a regular basis for over 20 years. I think its far more likely his guess that the extension in the HF's are too blame is wrong, and that there is some other real cause for the difference between the 2 tuners.

Hello folks you are far away from the initial subject: degradation of a pair of speakers over the years not the ears ..........

Perhaps a another way to phrase the OP's Q is whether current model speakers use better materials and employ better technology that the SOTA of 40 years ago. And hence, sound better than the old stuff.

I suspect the answer is in the affirmative. Stated differently, if the OP was to stack an old pair of B&Ws against an equivalent current model, I surmise the newer model very well might sound better.

Technology has advanced across the board.

Short post-script to my last post.

If the OP's Q also goes to whether old speakers mechanically wear out like old car shocks over time, I surmise that some speaker parts will degrade over time. For example, the caps used in the cross-over may change values. Also, speaker surrounds may disintegrate over time. Possibly voice coil spiders too.

In short entropy is part of the natural world. Ain't no stopping it.

Zd542 - I didn't suggest that the change wasn't real. I did, however suggest that when his perspective changed he no longer viewed the Marantz as lacking highs, but rather have a more full mid and bass range. The sound of the Marantz was constant, but his assumption about it changed resulting in a different experience.