Dual Earthquake 21’s

Dual Earthquake 21’s


A.J. Love

Project Category:


Project Level:


Project Time:

8-20 Hours

Project Cost:


Project Description:

Sealed, dual 21″ subwoofer, internal volume of roughly 6ft^3

Design Goals:

The goal of this design was to build a MONSTER subwoofer for my home theater system that is capable of massive output down in the single digits. It’s based on the Toids DIY Audio “Earthquake 21” subwoofer build, but I decided to double the enclosure size, to house two subwoofers in one enclosure. “BIG” was a huge part of the design-remix decision, as my front soundstage LCR speakers are rather large speakers (the Soundstage 15’s, also a Toid’s DIY Audio speaker design)

Driver Selection:

The original Earthquake 21 plans were made around the SB Audience 21SW800. After lots of research, I found that the specs for the Dayton Audio PSS555-8 21″ Pro Subwoofer are close enough that they would make for a more-than-decent replacement

Enclosure Design:

The enclosure is a simple sealed enclosure.

Outside measurements are 24″x24″x46.5″

Crossover Design:


Tips & Tricks:



These subwoofer drivers DELIVER. They cost less than half the price of the next cheapest mainstream 21″ driver offered, with nearly the same specs/TS parameters.

With enough power (I’m using one channel of a Sinbosen FP14K), I don’t see many people needing more bass than these deliver, and I’m actually sure a single would be more than enough for the vast majority of homes. During music and movie scenes, these can and literally HAVE shaken the light fixtures loose on my homes exterior; it’s impressive to say the least.

About the Designer:

I’m just a guy trying to save some money by DIY’ing my own home theater system.

*Again, the original design these were based on was made by Toid’s DIY Audio.

Project Parts List:

Part #DescriptionQty:
295-050Dayton Audio PSS555-8 21″ Pro Subwoofer with 4.5″ Voice Coil 8 Ohm2

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