An 8-person Thermowood cabin with what may be the best sauna sound system in the world
Hear About the Sound SystemThe sauna sits in Sparadise, the outdoor spa area at the Playhouse, alongside the cold plunge and the swim spa. It's a Redwood Outdoors Thermowood Garden cabin — spacious, cedar-scented, and wired with a four-way immersive audio rig that puts a subwoofer in the room and tactile bass transducers underneath the benches, so you don't just hear the music, you feel it through the wood.
The cabin, the build, and the audio install. Click any image to open it full size — then use the arrows or your keyboard to move through the set.
Most of these come from the Sauna mods album on Google Photos. More of the property is on the Photos & Media page.
See the sauna experience in motion.
The cabin is a Redwood Outdoors Thermowood Garden 8-Person Sauna. The interior is spacious, with an average height of about 8 feet sloping up to 10 feet at the peak. Thermowood is heat-treated timber, which makes for a more stable, rot-resistant shell — and, acoustically, a livelier room than a typical small sauna. That liveliness is wonderful for music and a real challenge for even coverage: the sloped ceiling means sound levels and frequency response shift noticeably between seating positions, which is exactly why the audio system is tuned the way it is.
A multi-channel immersive audio system built for sublime low end. Traditional speakers handle the music; bass shaker transducers bolted to the seating handle everything you feel rather than hear.
A single source feeds a Behringer Flow 8 digital mixer, which handles mixing and volume, and a miniDSP Flex 8, which handles the digital signal processing. From there the signal fans out to four independent paths — stereo mains, a dedicated subwoofer, and two chains of tactile transducers.
Design principle: the two Buttkicker amps are daisy-chained through the Line Out on the BKA-300-4 rather than fed by a splitter. No signal splitting, no integrity loss, and each amp keeps its own gain and filter settings.
| Device | Role |
|---|---|
| Sonos Connect Gen 2 | Signal input source (discontinued model) |
| WiiM Pro | AirPlay 2 receiver / input source |
| Behringer Flow 8 Mixer | Main mixer & DSP — 4 outputs (L/R + 2 monitors) |
| miniDSP Flex 8 | 8-channel DSP — crossovers, EQ, time alignment, Dirac room correction |
| Dirac UMIK-1 Microphone | Room measurement & calibration |
| Device | Drives |
|---|---|
| Yamaha RX-V871 AV Receiver | Main stereo speakers (Polk Atrium 8) |
| LAB Gruppen E8:2 | JBL subwoofer |
| Buttkicker BKA-300-4 | Aurasound bass shakers |
| Buttkicker BKA-1000P | Buttkicker Concert + Advance transducers |
| LAB Gruppen E4:2 | Spare / expansion |
| Device | Purpose |
|---|---|
| Polk Audio Atrium 8 SDI (×2) | Main stereo outdoor speakers (L/R) |
| JBL C29AV-1 Professional | 8" subwoofer |
| Buttkicker Concert Transducer | Tactile bass, mounted to the seating platform |
| Buttkicker Advance Transducer | Tactile bass, mounted to the seating platform |
| Aurasound AST-2B-4 Pro (×2) | Tactile bass shakers, mounted to the bench |
Each path is crossed over so the three layers stack instead of fighting each other:
| Path | Filters | Level |
|---|---|---|
| Flow 8 → Main Out (Yamaha) | High-pass 80 Hz, EQ flat | 75% (−7.5 dB) |
| Flow 8 → Monitor 1 (sub) | Low-pass 100 Hz, high-pass 20 Hz | 100% (0 dB) |
| Flow 8 → Monitor 2 (tactile) | Low-pass 100 Hz, high-pass 25 Hz | 85% (−3 dB) |
| Yamaha RX-V871 | Pure Direct, speakers "Small", crossover 80 Hz, EQ bypassed | Start at −20 dB |
| LAB Gruppen E8:2 | HPF 25 Hz / LPF 100 Hz, −24 dB/oct, mono in, 4 Ω | Start at 50% |
| BKA-300-4 (Auras) | Low cut 25 Hz / high cut 80 Hz, −12 dB/oct, Line Out on | Start at 40% |
| BKA-1000P (Buttkickers) | Low cut 25 Hz / high cut 80 Hz, bridged, 1.4 V sensitivity | Start at 50% |
These are the amp-side settings the system was commissioned with. Once the Flex 8 tuning pass happens, the filtering collapses onto the Flex 8 and these downstream crossovers get flattened out — see The miniDSP Flex 8 below.
Wiring throughout is 12 AWG minimum. The Aurasound shakers run in true parallel for a 2 Ω load; the two Buttkickers run in series for 6 Ω. Phase alignment matters more than usual here — a transducer wired backwards cancels the very thing it exists to produce.
The miniDSP Flex 8 sits between the Flow 8 and the amplifiers, and it's installed and running. It's the piece that lets one device own all the crossovers, EQ, time alignment, and Dirac room correction. The Flow 8 stays on in front of it as the mixer and volume control. With the Flex 8 in charge, each amp gets set to full-range with only its gain adjusted — no double or triple filtering, and consistent phase response across every output. Outputs 6–8 are spare, left for future expansion.