DIY Bookshelf Speaker Cabinets¶
Project Overview¶
Designing and building a pair of bookshelf speakers from scratch — from selecting drivers and designing the crossover network, to milling the cabinets from Baltic birch plywood and applying a hand-rubbed oil finish.
Driver Selection¶
After extensive research and modeling in WinISD, I selected:
| Driver | Model | Size | Role |
|---|---|---|---|
| Woofer | Dayton Audio RS150-4 | 6" | Low/mid frequencies |
| Tweeter | SB Acoustics SB26STCN-C000-4 | 1" | High frequencies |
The RS150 provides smooth response up to 3kHz with excellent transient response, while the SB26 tweeter extends cleanly to 30kHz.
Cabinet Design¶
- Internal Volume: 12 liters (sealed)
- Material: 18mm Baltic Birch plywood
- Joinery: Rabbet joints with wood glue, clamped
- Bracing: Internal ladder brace at mid-height
- Damping: 1" polyester fill at 50% volume density
Panel Cutting¶
All panels were cut on a table saw with a crosscut sled for precision. The driver cutouts were made using a plunge router with circle-cutting jig.
Plywood Selection
Standard construction plywood has internal voids that resonate. Baltic birch has void-free cores that produce dead-quiet cabinets. The extra cost is well worth it.
Crossover Network¶
A 2nd-order Linkwitz-Riley crossover at 2.5kHz:
| Component | Value | Part |
|---|---|---|
| Woofer inductor | 1.0 mH | Air core |
| Woofer capacitor | 4.7 uF | Polypropylene |
| Tweeter capacitor | 3.3 uF | Polypropylene |
| Tweeter inductor | 0.33 mH | Air core |
| Tweeter resistor | 3.3 ohm | 10W wirewound |
The resistor on the tweeter leg provides level matching since the SB26 is about 3dB more sensitive than the RS150.
Finish¶
- Sand all surfaces to 220 grit
- Ease all edges with a 1/8" roundover bit
- Apply Rubio Monocoat Pure (single coat, amazing stuff)
- Buff with white Scotch-Brite pad after 5 days cure
- Apply felt pads to the bottom
Listening Impressions¶
The speakers produce a remarkably open and detailed sound. The imaging is precise, with a wide soundstage that extends well beyond the physical speaker locations. Bass extension reaches down to about 55Hz (-3dB) in-room, which is impressive for the cabinet size.
Compared to similarly priced commercial speakers, these hold their own easily. The total cost was approximately $180 for the pair — equivalent performance from a retail speaker would cost $400-600.