Need Help for Subwoofer Problem

[TukangUsapEmenq]

Got a little DIY build of my room's 2.1 speaker. Actually, this is a kind-of old build I built 4 years back.

Here's the setup that I use.

 

Spoiler

 

I use that old small computer speaker amplifier-small subwoofer combo as the main amplifier for the home-theater speakers (which sounds nice already btw), and since the Simbadda amp actually includes a small subwoofer speaker inside it (and it sounds kind of bad, barely punching my ear), so I cut the cable to the output of the included woofer, and connect it to the big-one subwoofer I have laying around. It works, really, flawlessly for years....

 

Till now.

 

Here's the problem: the subwoofer kind of got a distorted output lately. First issue is, when I wanna setting the volume, sometimes it distorts really a lot that it actually vibrates till outside of the house, or it went so small that it barely heard able, or worse, when even a slight touch to the volume potentiometer already make those distortion. I'm using the RCA input (amplified input from the big woofer I think) on the woofer, and probably only set the volume at 3-5%. More than that, probably I can blow the whole house. I think, probably, I damaged a part inside the big woofer (I suppose the volume potentiometer of the big-bass got damaged by the years of resisting the power input from the already amplified bass output from the Simbadda one).

 

It annoys me when the distortion came more occasionally lately, so I kind of temporarily solved this problem by using the high-level input of the woofer itself, but, yeah. The old Simbadda amp actually can't handle the power that it sounds so small on mid-volume bass music, but it hits so hard on high-volume bass songs, that I can't increase the volume anymore of what I like, because of that bass hit so hard on high-intensity bass songs.

 

I recorded how it actually behaves right now. Here's the link.

First song, 'the humans are dead' lyrics, bass feels too low. But after 'come on sakar lek ma batereh', it's actually good for me.

Second song, you probably know how kind of little bit of bassy the intro is: I barely feel the bass.

Third and fourth, it actually vibrates the whole block.

Fifth, again, barely feel the bass.

 

Conclusion is, it bit lack of power on high-level input, but it suffers a lot either from the RCA input.

 

I actually got few way to solve this nicely:

1. Use the RCA input, but add additional resistor or voltage dividing circuit to reduce the power that go inside to the big-woofer.
2. Get another amplifier to amplify the bass only. Because... The home-theater speakers already sounds good. And that's enough for me.
3. ... or anything else?

Thanks for you guys help here, kind of... need those things done, since.. Yeah. Got no good entertainment since the lockdown around the world.