Question Noticeably less bass than before ?

[Blingbo]

EDIT: I want to clarify only the low bass changes volume, mid and high bass remain the same.

I've noticed this issue after a month of low-volume music listening. For clarity, my default volume level is at -30dB (measures ~75dB room noise). Issue is something like this - song starts as usual, 10-15 seconds later the bass level drops to half. No settings were changed and no rearrangements were made to the room.

Audio system is 5.1ch and as follows:
Connection AUX->PC
Amp - Pioneer VSX-915 (100W per channel)
Fronts - Jamo C 407 (150W) 4sq mm copper/silver wires
Center - Jamo E 8CEN (140W) 4sq mm copper/silver wires
Sides - JBL MK 1000 (~80W, not much info online) 2sq mm copper wires
Subwoofer - Jamo SUB 200 (200W) RCA cable

Only Fronts and Sub are set to reproduce bass

I've read the amp's manual many times, looked into the settings, but cannot find a culprit. Single fan blows on a giant heat sink. Fan works, no noticeable change in temps felt by hand on case over my 2 year ownership. Only thing I haven't done is open the amp and look for some hidden dust buildup. I just blow some compressed air through the vents to clean it.
Any suggestions are welcome!

P.S. I may have gotten used to the volume levels haha

 

[Aeacus]

No settings were changed and no rearrangements were made to the room.

So, something died. Either AMP or subwoofer voice coil.

Btw, why do you use such a weak AMP with your speakers? Your Front and Center speakers need 50% more what AMP can deliver and sub needs twice as much. Using weak AMP, either overloads and burns the AMP, or fries speakers voice coil. With your speaker setup, i'd use an AMP with 400W per channel.

 

[Blingbo]

So, something died. Either AMP or subwoofer voice coil.

Btw, why do you use such a weak AMP with your speakers?

How can I understand/test what has failed? I'll get them tested by a shop anyway

I bought the speakers and Amp together and didn't bother looking for another. What not overly expensive amps would you recommend?
Also, how could an underpowered amp running at less than maximum output damage speakers rated for more than it could provide?

 

[Aeacus]

Also, how could an underpowered amp running at less than maximum output damage speakers rated for more than it could provide?

Further reading: https://www.audioreputation.com/speaker-wattage-vs-amp-wattage/

What not overly expensive amps would you recommend?

Read the link i shared to know how to properly look for a suitable AMP.

 

[devgen]

You can also try https://www.genderlessvoice.com/best-bookshelf-speakers/. These speakers come with lots of features.

 

[Aeacus]

You can also try https://www.genderlessvoice.com/best-bookshelf-speakers/. These speakers come with lots of features.

Here's a question to you; how your suggested bookshelf speakers help OP? OP, who's issue was using too weak of an AMP, which killed something within their setup. And based on OP needs, OP needs low bass, which those tiny bookshelf speakers are incapable of providing.