Short answer: build your own when you want a lot of bass for the money, you've got room for a proper box, and you're happy adding an amp with some EQ. Buy one when you want it small, finished and plug-in, with room EQ in an app and a warranty on the lot. Subwoofers are the easiest DIY project going (no crossover to design) and the place where DIY saves the most.
What you're paying for in a commercial sub
A good powered sub is a driver, a box, an amplifier, a DSP and, often, an app with room correction, all designed together and finished nicely. Buying one gets you:
- Integration. The amp, DSP and driver are matched. Plug it in, run the app, done.
- Size. Good commercial subs use long-throw drivers, big amps and heavy DSP to get deep bass out of a small box. That's genuinely hard to replicate cheaply.
- Finish and warranty. A nice piece of furniture with a warranty on the whole thing.
- Resale. A known brand holds its value.
What you're also paying for is everything in the chain between the factory and your lounge room: the dealer, the distributor, marketing and freight on a very heavy box.
What DIY gets you
- More driver for the money. You can afford a bigger driver, or two.
- The box you want. Sealed, ported, big or small, shaped to fit your room.
- Choice of amp. A plate amp in the box, or an external amp.
- Easy upgrades. Add a second sub later, swap the amp, change the EQ.
A costed example: two sealed 18" subs
From our Sealed 18SW500 build guide, re-costed with everything in it (prices as of 3 October 2026):
| Part | Price |
|---|---|
| 2 x SB Audience BIANCO-18SW500 @ $349.95 | $699.90 |
| Behringer NX3000D amp (we don't sell it; see below) | about $489 to $539 |
| 2 sheets 18 mm MDF, 2400 x 1200 | about $102 to $118 |
| PVA wood glue, 1 L | $19.00 |
| 3 pairs of binding posts | about $75 to $87 |
| Polyfill, about 1 kg per box | about $60 to $74 |
| Paint | your choice |
| Total | about $1,445 to $1,540, plus paint |
We don't sell the NX3000D; it's just the amp the guide was designed around. Any amp with enough clean power into 4 ohms and some parametric EQ will do the job.
For comparison, the nearest commercial sealed subs we could find in Australia are SVS's 15" SB-5000 R|Evolution at $4,999 each and the 17" SB17-Ultra R|Evolution at $5,999 each (no one sells an 18" sealed home sub here). Those come with the amp built in, room EQ, a lovely finish and a warranty. The DIY pair is about output per dollar, not convenience.
When buying makes more sense
Being honest about it:
- You want a small sub. Deep bass from a small box needs serious excursion, a big amp and clever DSP. Good commercial subs do this very well, and DIY doesn't save much in this corner.
- You want it to look like furniture. A factory finish is hard to match at home.
- You want plug-and-play room correction. Apps with built-in room EQ are genuinely useful. You can do the same with a measurement mic and REW, but it's more work.
- Budget subs. At the cheap end, mass production wins. A small budget sub is hard to beat by building.
- No space for a big box or the tools to build one.
Choosing an amplifier
Plate amplifier (mounted in the sub): the tidy option. One box, one power lead, one signal lead. Most have a low-pass filter and phase control, and some add DSP and EQ.
External amplifier: a pro-audio power amp with DSP (like the NX3000D in our guide) gives a lot of power per dollar and can drive two subs. It needs a rack or shelf and has a fan. Pro amps usually have Speakon outputs, so a Speakon panel socket on the sub box keeps it neat.
Adding EQ to an amp that doesn't have it: a standalone subwoofer DSP sits between your receiver and the amp.
Whichever you pick, check it's happy with the load. Two 8-ohm subs in parallel make 4 ohms, as in our guide. Speaker wiring and impedance covers the maths.
Sealed or ported?
- Sealed: smaller box, gentle roll-off that blends well with room gain, easy to build, loves EQ and power. The usual pick for home subs with DSP.
- Ported: more output for the same driver and amp near the tuning frequency, but a bigger box and a steep roll-off below tuning, so you'll want a subsonic filter.
Sealed vs ported vs passive radiator goes into the details, and How to read driver specs shows how to tell which a driver suits.
One sub or two?
Two is usually better than one, and not just for volume. Room modes make bass uneven from seat to seat. Research by Todd Welti and Allan Devantier (Harman, published in the Journal of the Audio Engineering Society in 2006) found that multiple subwoofers in the right positions give much more even bass across a room than a single sub.
Two subs also share the work, so each one moves less for the same level. If you're building, the second sub costs much less than doubling up on a commercial one.
Setting it up
- Placement: try the "sub crawl". Put the sub at your listening seat, play bass, and crawl around the room to find where it sounds smoothest. Put the sub there.
- Measure: a calibrated mic and REW show what the room is doing (Measuring speakers on a budget).
- EQ the peaks, not the nulls. Cut the room's peaks. Don't try to boost a null: move the sub or the seat.
- Crossover: typically around 80 Hz to the main speakers, set in your receiver or DSP.
Quick questions
Is it cheaper to build a subwoofer? Usually much cheaper for the same driver size and output, especially for big subs. Less so for very small subs.
Do I need a plate amp? Either a plate amp or an external amp. A plate amp is tidier; an external pro amp gives more power per dollar.
Can I build a subwoofer with no woodworking experience? A sealed sub is about as easy as it gets: a box, a hole, a driver and a terminal. If you can cut straight and glue square, you can build one.
What size subwoofer should I build? As big as your room, budget and partner allow. Bigger drivers move more air with less effort.