{"product_id":"earthquake-21-21-inch-sealed-subwoofer-build-plans","title":"Earthquake 21 — 21-Inch Sealed Subwoofer Build Plans","description":"\u003cp\u003eThe Earthquake 21 started with a theory: could I put a 21-inch subwoofer in a small sealed box and get the kind of output you'd normally expect from a much bigger enclosure? I built two of them for my theater to find out. These are the plans for that build.\u003c\/p\u003e\n\n\u003ch2\u003eWhat the Earthquake 21 Is\u003c\/h2\u003e\n\u003cp\u003eIt's a sealed subwoofer built around the SB Audience Rosso 21SW800, a 21-inch driver, in a cabinet that's only about 2 feet in each direction. The idea was to let the natural room gain in my theater and some DSP do the work a bigger box would normally do.\u003c\/p\u003e\n\u003cp\u003eWhen I modeled it, it looked like I could get a flat response down to about 20 Hz in my room with a little DSP. After building it, I measured it at the sub and again at my seat. Even before DSP, the response came out very close to what I predicted. With DSP on my Crown XTi 2002, I was able to get it flat down to 10 Hz in my room. That's my room, though. Your room will give you different results.\u003c\/p\u003e\n\u003cp\u003eWhat surprised me most was the feel. With these, I wasn't just hearing the bass in my favorite movie scenes, I was feeling it. Each one has more than twice the cone area of the single 15-inch sub it replaced.\u003c\/p\u003e\n\n\u003ch2\u003eEarthquake 21 Specs\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDriver:\u003c\/strong\u003e SB Audience Rosso 21SW800 (21-inch)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEnclosure:\u003c\/strong\u003e sealed, heavily braced\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutside size:\u003c\/strong\u003e about 24\" x 24\" x 24\" (about 8 cubic feet)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInternal volume:\u003c\/strong\u003e about 6 cubic feet\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e MDF. I ended up needing about 2 sheets of MDF, mostly because of the bracing and the front baffle.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConnection:\u003c\/strong\u003e Speakon\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWhat I powered mine with:\u003c\/strong\u003e a Crown XTi 2002 with its built-in DSP, running my two 8-ohm subs in parallel for a 4-ohm load\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat's in the Plans\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003ePanel cut list for the main enclosure panels\u003c\/li\u003e\n\u003cli\u003eInternal bracing layout showing where each brace sits\u003c\/li\u003e\n\u003cli\u003eInternal bracing cut list\u003c\/li\u003e\n\u003cli\u003eCabinet dimensions and enclosure layout\u003c\/li\u003e\n\u003cli\u003eBasic assembly information\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThis is a digital download (PDF) for personal use. The driver, amplifier, MDF and other parts are not included.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eThis can be dangerous. If you don't know what you're doing, get help.\u003c\/strong\u003e It's a big, heavy cabinet built with power tools, and it runs on a high-power amp. I needed a friend to help me carry each one up the stairs.\u003c\/p\u003e\n\n\u003ch2\u003eWatch the Earthquake 21 Build\u003c\/h2\u003e\n\u003cp\u003eThe full build is on my YouTube channel: \u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\" target=\"_blank\" rel=\"noopener\"\u003eDive Into Deep BASS: Build Dual 21 Inch Subwoofers Yourself! - Earthquake 21's\u003c\/a\u003e (14 minutes).\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\u0026amp;t=54s\" target=\"_blank\" rel=\"noopener\"\u003e0:54\u003c\/a\u003e Design and planning\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\u0026amp;t=144s\" target=\"_blank\" rel=\"noopener\"\u003e2:24\u003c\/a\u003e Construction\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\u0026amp;t=332s\" target=\"_blank\" rel=\"noopener\"\u003e5:32\u003c\/a\u003e Sanding and finishing\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\u0026amp;t=440s\" target=\"_blank\" rel=\"noopener\"\u003e7:20\u003c\/a\u003e Driver installation\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.youtube.com\/watch?v=mM7F6dWM_dc\u0026amp;t=624s\" target=\"_blank\" rel=\"noopener\"\u003e10:24\u003c\/a\u003e Testing and results\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eParts Used and Mentioned\u003c\/h2\u003e\n\u003cp\u003e\u003cem\u003eDisclosure: some links below are affiliate links. As an Amazon Associate I earn from qualifying purchases, and Toid may earn a commission from Parts Express links at no extra cost to you. Prices change, so check the current price before you order.\u003c\/em\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/www.madisoundspeakerstore.com\/audience-subwoofers\/sb-audience-rosso-21sw800-21-subwoofer\/\" target=\"_blank\" rel=\"noopener\"\u003eSB Audience Rosso 21SW800 21\" subwoofer\u003c\/a\u003e (Madisound), 1 per sub\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/parts-express.sjv.io\/c\/3586166\/1370857\/16448?u=https%3A%2F%2Fwww.parts-express.com%2FCrown-XTi-2002-Power-Amplifier-2-x-800W-at-4-Ohms-245-407\" target=\"_blank\" rel=\"sponsored noopener\"\u003eCrown XTi 2002 power amplifier\u003c\/a\u003e (Parts Express)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/www.amazon.com\/dp\/B07PFNFNKP?tag=tdaudio-20\" target=\"_blank\" rel=\"sponsored noopener\"\u003eSpeakon panel-mount jack\u003c\/a\u003e (Amazon), 1 per speaker\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/www.amazon.com\/dp\/B00LW8VLRU?tag=tdaudio-20\" target=\"_blank\" rel=\"sponsored noopener\"\u003eSpeakon plug\u003c\/a\u003e (Amazon)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/www.amazon.com\/dp\/B003L170C6?tag=tdaudio-20\" target=\"_blank\" rel=\"sponsored noopener\"\u003eMonoprice 12 AWG speaker wire\u003c\/a\u003e (Amazon)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/parts-express.sjv.io\/c\/3586166\/1370857\/16448?u=https%3A%2F%2Fwww.parts-express.com%2FExoHyde-Pro-Grade-Textured-Protective-Speaker-Cabinet-Coating-Quart-260-2100\" target=\"_blank\" rel=\"sponsored noopener\"\u003eExoHyde textured cabinet coating\u003c\/a\u003e (Parts Express)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/parts-express.sjv.io\/c\/3586166\/1370857\/16448?u=https%3A%2F%2Fwww.parts-express.com%2FfoamPRO-4-Textured-Roller-with-Handle-260-115\" target=\"_blank\" rel=\"sponsored noopener\"\u003efoamPRO 4\" textured roller\u003c\/a\u003e (Parts Express)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e \u003ca href=\"https:\/\/www.amazon.com\/dp\/B086DTV28M?tag=tdaudio-20\" target=\"_blank\" rel=\"sponsored noopener\"\u003eX-Tronic soldering station\u003c\/a\u003e (Amazon)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e T-nuts and machine screws to hold the driver in (details are in the plans)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e MDF, about 2 sheets (source it locally)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUsed:\u003c\/strong\u003e Rockwool (Roxul) Safe'n'Sound insulation in the brace cavities\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRelated Plans and Posts\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"\/products\/audience-212-dual-12-diy-home-theater-speaker-plans-toid\"\u003eAudience 212 Dual 12\" DIY Home Theater Speaker Plans\u003c\/a\u003e, the speakers built around SB Audience woofers\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/products\/dinas-do-i-need-a-subwoofer-build-plans\"\u003eDINAS DIY Speaker Plans\u003c\/a\u003e, if you'd rather build the bass into the speakers\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/blogs\/news\/iso-100-diy-subwoofer-under-100-isobaric-grs-10sw-4\"\u003eThe Best Subwoofer for Under $100?\u003c\/a\u003e, my ISO-100 isobaric sub build\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/blogs\/news\/audience-212-diy-jtr-212-inspired-home-theater-speaker\"\u003eDIY Attempt at $14,000 JTR Speakers\u003c\/a\u003e, the Audience 212 build story\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/collections\/diy-speaker-plans\"\u003eAll DIY Speaker Plans\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/pages\/diy\"\u003eMore DIY builds from Toid\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Toid","offers":[{"title":"Default Title","offer_id":67941223104878,"sku":null,"price":20.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1007\/9001\/0222\/files\/Earthquake21website.jpg?v=1793407389","url":"https:\/\/toidtech.com\/products\/earthquake-21-21-inch-sealed-subwoofer-build-plans","provider":"Toid","version":"1.0","type":"link"}