Is More Better?

When I ran Dahlquist DQ10’s with double Dahlquist subwoofo, the placement turned out to be important for the best imaging. Low frequencies are supposed to be non-directional, but I think it matters depending on your crossover point and the steepness of the high filtering. I thought two worked much better than one for integration, but it made for a physically unwieldy system. I simplified my system, getting rid of the subwoofers when I changed speakers, as I found the system more cohesive and imaging better, even though I lost the bottom half octive.

More subs located and setup properly will give you a smoother response. You will also have less distortion. I would recommend a minidsp 2x4 for distance and phase control If you are locating them around the room. 

You might find some of the this helpful.

https://www.harman.com/documents/multsubs_0.pdf

https://www.youtube.com/watch?v=RE6g2IawzSQ

Unless you’re setup is in an aircraft hanger, that’s crazy overkill, but you do you.

This too-clever-by-half comment is not that clever. It reflects a misunderstanding of why multiple subs are helpful. It’s about the room’s acoustics. It depends a lot on the room (see comment in next paragraph about measuring). 

Having three subwoofers isn’t about more bass, but achieving a more articulate and even bass response throughout your room. A single subwoofer creates "hot spots" and "nulls," leading to muddy or boomy or weak bass. Multiple, strategically placed subwoofers smooth out these peaks and dips, providing tight, detailed, and clear bass across a wider listening area. You should be prepared to put them where the sound is best, not where they "look good." The goal is audio balance not visual symmetry or prettiness.

You will need to learn a little. Measurement and Digital Signal Processing (DSP) are essential. Using a microphone (UMik) and software (REW, for example) can help measure your room to reveal problem areas. DSP then allows precise equalization and time alignment for each subwoofer, ensuring they work harmoniously. 

I recommend Rythmik sealed subs as better options than REL, e.g. They are more flexible (adjustable phase, for one) and more economical.

is more subs better?

The answer is “yes, but….”

For 2 channel audio, Smoother Frequency Response: Multiple subwoofers can help to even out the bass response across the listening area, reducing peaks and nulls (dead spots) that are common with a single subwoofer.  The second subwoofer makes a huge difference, but each subwoofer added afterwards yields increasingly smaller benefits.

So yes, each added subwoofer benefits a smoother frequency response, “but” is adding 2 more subwoofers better than spending the funds somewhere else for greater sonic benefit…..?