Speakers replace or improve?

1. No

2. Probably not. Although, I’ve a sneaking suspicion that you are expecting room-shaking bass. Are you sure they are wired correctly? Out of phase connections will have poor bass. I think you need to connect the sub somehow and reappraise. Otherwise, better amplification is on the cards.

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.

You are in a difficult situation. Pushing your speakers to produce more bass is going to increase distortion and rob you of headroom. Your main problem is where you live. If you want to improve your bass you will require a new living situation. Having said that many digital preamp processors have very functional EQ capabilities. Examples are Trinnov, DEQX, Anthem and MiniDSP.

If this is the case, the issue is with your turntable and or the phono amplification. Buy a $149 Schiit Mani 2 and bypass the integrated phono input. Ensure the turntable is mounted on a solid surface. Remove lid if possible when playing.

It is also connected to the same amp and the speakers. The bass is much better when I play compacts

Is this a joke?

Keep in mind, bass is only part/not a lot of the music you are playing. To cut higher frequencies out all the time is not the way to solve it.

"The treble and mids are ok but the bass is very weak."

(Polk's two 8" woofers and a front port, in a small room should sound good)

"To make the speakers to produce some bass I reduce treble"

(bad!), (the speakers are producing all the bass they can, cutting treble from everything, all the time will not sound good)

"reduce the Loudness setting  from Flat to -30db"

(bad!) ('loudness' is for low volume listening. it boosts bass, progressively as you lower the volume) (cutting the effect of loudness is going opposite to what you want)

"and turn volume to very high. But I live in a townhouse and can’t do that most of the time".

('loudness' is what you want, especially at low volume).

(normally at normal/loud volumes, the 'loudness' filter should be OFF to prevent too much bass).

(for you, a self-described bass freak: you could try leaving 'loudness' on when listening loud, leaving every other frequency alone, just boosting bass))

"If possible I would like to increase the bass. I know that this question was asked many times and there is no universal solution. My home stereo is located in the small living room which practically doesn’t have a back wall because there is a big opening between the living room and the dining room.

(are there partial walls at the sides, i.e. corners?)

(if not, you could build short walls, say 3' long behind each speaker, put the speakers close to both side and rear wall).

I also have the Polk Audio PSW108 subwoofer but I don’t use it because there is no room for the sub in my living room."

(you need to figure out how to use a PAIR of subs, self-powered, front firing, located adjacent to the Polks).