Speakers replace or improve?

I think you are wrong about Loudness control. Below is that the manual says about Loudness:

"Making it easier to hear the high- and low-frequency ranges even at low volume (LOUDNESS)

Enjoy natural sound even at low volume by lowering the mid-range sound level and compensating for the human ears’ loss of sensitivity to high- and low-frequency ranges at low volume.

And I am not a self-described bass freak. I just want my sound to be balanced. I don't want to hear only highs and mids.

Thanks a lot for all your answers and suggestions. I am sure the speakers are wired correctly. I checked that several times.

Occasionally, when I am lazy, I play CDs using my old Sony CD CDP-CE415. It is also connected to the same amp and the speakers. The bass is much better when I play compacts. Maybe I need to get a decent preamp?

I am not expecting room-shaking bass. I just want to hear the bass when I play vinyl records.

I think I will connect the subwoofer for now until I find the best solution for my problem.

Before I make any investments I will try few things.

1. I will try to temporary swap the YAMAHA amp with my 28 years old Sony STR-D665 which has bass boost option. It sits in my basement and plays very well with my 20 something years old Sony SS-MF315 speakers.

2. I will try to use the Sony STR-D665 as a second amp for bi-amp option.

3. I will try to temporary swap Polk Audio speakers with my old Sony speakers to see if the problem with the speakers.

No, I don't have a friend who can let me borrow his sub. But when I turn on my sub it produces more than I need bass. I just need to learn how to use it properly because it has two knobs and two switches. 

I was trying to avoid using the sub because I can't put it in front. It sits close to the right side wall. But it looks like I need to use my subwoofer all the time. And probably buy a second sub. 

My sub allows wiring speakers to the sub. Is this a good option? Right now my speakers wired to the amp and the sub connected to the amp.

Well, sometimes it looks like the issue is with the turntable. But when I played records on my previous turntable (Audio-Technica AT-LP120 with Shure M97xE Cartridge)  I experienced the same problem. Probably preamp in the phono input on my YAMAHA amplifier is not working well. I am thinking to get a preamp and try to connect the Fluance RT85 Turntable  to CD input to see if it makes any difference. 

But for now I will sue my Polk Audio sub.

Great site. Thanks.

@grislybutter 

Hello, 

Thank you very much for your suggestions. 

Normally, I don't use loudness control to boost the bass. I was experimenting to see if speakers can produce the bass. I found that they can. They just need much more volume/power then I can apply in my small living room. If I put more volume then treble and mids will be way too loud.

So, my option right now is to use my Polk Audio sub. Not the best sub but it does its job. 

Then, when I have more time, I will try bi-amp option. I will try to connect woofers on the speakers to my 25 years old more powerful Sony receiver. I just need to order speakers wires and RCA splitter.

Thanks