A 2.1 hi-fi system built around DML (Distributed Mode Loudspeaker) flat panels for the mids/highs and a powered subwoofer for the bottom end. Two exciters turn two flat panels into full-range-ish speakers; a small Class-D amp drives them and feeds the sub.
- Budget: ~$660 total
- Difficulty: Beginner-friendly (no crossover math, no soldering required)
- Use case: Music-first listening in a small/medium room
- Time: An afternoon
A normal speaker pushes a rigid cone back and forth. A DML panel works completely differently: an exciter (basically a voice coil without a cone) is glued to a thin, stiff, lightweight panel and vibrates the whole surface. The panel breaks into thousands of tiny "distributed modes" that radiate sound in every direction. The result is a big, open, room- filling sound that images unusually well and doesn't beam like a conventional tweeter.
The catch: panels can't do bass. Below ~100–150 Hz they run out of steam. So we cross them over to a real subwoofer that handles everything low. That's why this is a 2.1 system:
.2— two DML panels (left + right), one exciter each1— one powered subwoofer for the lows
| # | Part | Spec | Qty | Where to buy | ~Price |
|---|---|---|---|---|---|
| 1 | RSL Speedwoofer 10S MKII | Powered 10" ported sub, 22 Hz, built-in 400 W amp | 1 | RSL direct (rslspeakers.com — factory-direct only) | $449 |
| 2 | Dayton Audio DAEX32U-4 "Ultra" exciter | 32 mm, 20 W, 4 Ω, best-SQ panel exciter | 2 | Parts Express (#295-235) or Amazon | ~$33 ea → $66 |
| 3 | Fosi Audio BT20A amplifier | Stereo Class D + sub-out w/ 80 Hz high-pass, Bluetooth | 1 | Fosi Audio direct or Amazon | $80 |
| 4 | XPS foam panels | Owens Corning Foamular 150, cut to ~24" × 32" | 2 | Home Depot / Lowe's (insulation aisle) | ~$25 |
| 5 | RCA subwoofer cable | Single RCA, ~10–15 ft | 1 | Amazon / Parts Express | ~$12 |
| 6 | Speaker wire | 16 AWG, ~50 ft roll | 1 | Amazon / Parts Express | ~$15 |
| 7 | Panel edging / suspension | Foam weatherstrip, OR picture-frame + felt | — | Home Depot / Amazon | ~$15 |
| Total | ~$660 |
- RSL is direct-only: rslspeakers.com. Free US shipping, 30-day in-home trial. Not sold on Amazon or through dealers.
- Exciters: Parts Express DAEX32U-4 is the primary source; also on Amazon. Ships with pre-applied 3M VHB adhesive — peel and stick.
- Amp: Fosi Audio, ~$80. The BT20A Pro ($100) is a drop-in upgrade with more power and the same sub-out if you want headroom.
- Panels: any big-box hardware store. Buy one 4' × 8' sheet of rigid XPS foam (~$30) and cut both panels from it.
| Want... | Swap to | Why |
|---|---|---|
| Louder, more low-panel output | DAEX32EP-4 "Thruster" (40 W, PE #295-230, ~$36 ea) | Double the power handling; a bit less refined than the Ultra |
| Deeper rumble / big room / movies | RSL Speedwoofer 12S ($799) | 16 Hz extension, 12" driver — overkill for a small music room |
| Smoother, more even bass | Second Speedwoofer 10S MKII ($898 total) | Dual subs beat one big sub for room-mode smoothing |
| Better panel sound later | Plywood, carbon-fiber skin, or plywood-skinned foam | Panel material is the #1 sound variable in DML |
- Utility/craft knife or hot-wire foam cutter (for XPS)
- Straightedge + tape measure + pencil
- Isopropyl alcohol + rag (clean the panel where the exciter sticks)
- Wire strippers
- Optional: small screwdriver, hot glue gun, painter's tape
Cut two identical panels ~24" × 32" from the XPS foam. This ratio (roughly the golden ratio) spreads the panel's resonant modes out evenly, which smooths the frequency response. Exact size isn't critical — bigger panels go a little lower, smaller panels are tidier. Keep both panels the same size so left and right match.
Where the exciter sits on the panel matters a lot — a bad spot sounds hollow and uneven. The well-known starting point is an off-center position at roughly 2/5 (0.4) of the panel's width and height from one corner — deliberately not centered, because dead-center excites symmetric modes and cancels others.
+---------------------------+
| |
| (panel) |
| |
| X <-- exciter | X ≈ 40% across, 40% up
| (~2/5, 2/5) | from a corner
| |
+---------------------------+
Tip: before gluing, tape the exciter on and listen. Nudge it around a few inches and you'll hear the tone even out. Glue once it sounds balanced. Mirror the position on the second panel so the pair matches.
- Clean the panel surface at the chosen spot with isopropyl alcohol; let it dry.
- Peel the 3M VHB backing on the exciter.
- Press firmly for ~30 seconds. The VHB bond strengthens over the next 24 hours — don't stress it hard right away.
The panel must be free to vibrate — do not clamp it rigidly. Two easy options:
- Simplest: run foam weatherstrip around the panel edge and set/lean it in a light frame, or hang it from two top corners with fishing line.
- Nicer: build a light picture-frame border and float the panel inside it on a soft foam/felt gasket so the edges aren't hard-mounted.
Aim to have the panels roughly at ear height, angled toward the listening position, spaced apart like normal stereo speakers.
Phone / PC ──(Bluetooth or RCA)──► Fosi BT20A
├─ L speaker out ──► Left panel exciter
├─ R speaker out ──► Right panel exciter
└─ SUB OUT (RCA) ──► RSL Speedwoofer 10S MKII (line in)
- Each exciter is a simple 4 Ω load on its own amp channel — one exciter per channel, so there's no series/parallel wiring to figure out.
- Observe polarity: amp + to exciter +, both panels wired the same way, so they move in phase.
- Run the single RCA from the Fosi's sub out to the RSL's line-level input.
- Turn on the amp's 80 Hz high-pass (the switch by the BT20A sub-out). This stops the panels from straining for bass they can't make and hands everything below 80 Hz to the sub.
- Set the sub's crossover (dial on the RSL) to around 80 Hz to match, then trust the high-pass on the amp. If your amp's HPF is fixed, use the sub's crossover to blend.
- Level-match the sub. Start with the sub volume low, play bass-heavy music, and bring it up until the bass feels even with the panels — not boomy. If you can consciously "hear the sub" as a separate thing, it's too loud.
- Sub placement. Try it in a corner first (more output), then experiment. The classic trick: put the sub at your listening seat, play music, crawl around the floor, and put the sub where the bass sounded best.
- Panel toe-in. Angle the panels toward you and experiment with distance from the wall — DMLs radiate from both faces, so wall reflection changes the tonal balance.
| Symptom | Likely cause | Fix |
|---|---|---|
| Thin / hollow midrange | Exciter too close to panel center or a bad node | Reposition exciter toward the 2/5 sweet spot |
| Boomy, one-note bass | Sub too loud or bad placement | Lower sub level; move sub; do the crawl test |
| Bass disconnected from panels | Crossover mismatch | Set amp HPF + sub crossover both ~80 Hz |
| Panel buzzes/rattles | Edge hard-mounted or loose exciter | Float the panel on soft gasket; re-seat exciter |
| One side quieter | Reversed/loose wire or polarity | Check both channels wired + to + |
| No bass at all | Sub cable in wrong jack | Confirm amp SUB OUT → sub LINE IN |
- RSL Speedwoofer 10S MKII — punches far above $449, digs to 22 Hz (plenty for music), and is powered, so it brings its own amp and only needs one RCA cable. A 12" was overkill for a music-first small/medium room.
- Dayton DAEX32U-4 "Ultra" — widely regarded as the best-sounding readily-available exciter for clarity; 4 Ω so it's happy on cheap Class-D amps; pre-applied VHB makes mounting trivial.
- Fosi BT20A — cheap, clean Class-D that happens to have a sub-out with an 80 Hz high-pass, giving you a complete 2.1 crossover in one $80 box. No separate sub amp or outboard crossover needed.
- XPS foam panels — the cheap, forgiving material to learn DML on. Panel material is the biggest sonic variable, so start here for $25 before chasing exotic panels.
- RSL Speedwoofer 10S MKII — https://rslspeakers.com/products/rsl-speedwoofer-10s-mkii
- Dayton DAEX32U-4 Ultra exciter — https://www.parts-express.com/Dayton-Audio-DAEX32U-4-Ultra-32mm-20W-4-Ohm-295-235
- Dayton DAEX32EP-4 Thruster (louder alt) — https://www.parts-express.com/Dayton-Audio-DAEX32EP-4-Thruster-32mm-Exciter-40W-4-Ohm-295-230
- Fosi Audio BT20A amp — https://fosiaudio.com
- XPS foam board — Home Depot / Lowe's insulation aisle
Built as a music-first 2.1 DML system. Panels for the magic, sub for the muscle. Start with foam, tune by ear, and upgrade the panel material once you're hooked.