Visible speaker boxes are unacceptable in premium residential and hospitality interiors. Hidden speaker technology conceals acoustic drivers behind finished surfaces — drywall, glass, and wood — while maintaining room aesthetic. KNX multi-zone amplifiers (Zennio ZAS-AUDIO8B) connect to these speakers exactly as conventional ones, but the installation technique differs entirely.

In-Wall Drywall Speakers

Mark the cutout position before first-fix plastering — impossible to add later without damage. Use a 200mm diameter hole saw (Sonance SR1 requires 208mm cutout). Run 2x2.5mm2 speaker cable through the stud cavity to the backbox position.

Sonance SR Series in-wall: frameless aluminium surround, paintable grille, 8-ohm, 100W peak. Installation steps: cut hole, pull cable through, connect to speaker terminals (red to red, no polarity on passive speakers but observe consistency for phase), push speaker into hole, tighten 4 spring-clip anchors from the front. Grille paint: use same emulsion as wall, apply with foam roller through the grille cloth — cloth absorbs paint and becomes acoustically transparent. Two coats, let dry 48 hours before listening test.

For stereo imaging: place L and R speakers symmetrically (equal distance from centre listening position, equal height). In-wall stereo pair: 2-3m apart at 1.2m height for a seated listening position.

In-Ceiling Speakers

Standard plasterboard ceiling: same hole-saw process as in-wall. Run cable in ceiling void before boarding. Use fire-rated backbox (Tenmat FF130E) in commercial buildings and partition zones — required by EN 13501-1 for fire compartment integrity. Secure backbox to noggin (blocking timber between joists) with screws.

Suspended tile ceiling: use 600x600mm tile-replacement speakers (Biamp Desono C-IC6) or dedicated drop-in circular speakers (JBL Control 24CT, ceiling tile adaptor). No cutting required — speaker replaces one tile.

Bathroom and wet areas: Sonance Mariner Series or Monitor Audio AW800-LCR (IP55 rated). Polypropylene cone does not absorb moisture. Use vapour-barrier backbox sealed with acoustic sealant at perimeter. Silicone seal between speaker flange and plasterboard after installation.

Glass Resonance Panels

An exciter transducer bonded to glass causes the entire glass pane to vibrate as a speaker. No driver visible. Products: SoundTile Pro exciter (50W, 4 ohm), Feonic ExactHush, Invisible Wave IW-GE.

Mounting: clean glass surface with isopropyl alcohol. Apply 40mm circle of Loctite EA 9455 structural adhesive to exciter mounting face. Press firmly at 1/3 panel width from one edge, 1/3 panel height from top (modal sweet spot). Hold for 60 seconds, full cure 24h before testing.

Two exciters per pane for stereo (left pane = L channel, right pane = R channel of double glass door). Feed from ZAS-AUDIO8B zone output via 2x1mm2 screened cable. Exciter impedance 4-8 ohm — zone should not drive more than two exciters in parallel (4 ohm minimum load).

Acoustic characteristics: strong midrange (300Hz-4kHz), weak bass below 150Hz. Supplement with a discreet subwoofer (under-floor or hidden in furniture) for full-range performance.

Wooden Ceiling Membrane Panels

Lightweight plywood panel (6-8mm birch) suspended 40mm below structural ceiling on 4 elastic cord mounts (Vibro-Acoustics VRC isolator). Exciter (SoundTile Pro or Dayton Audio DAEX32EP-4) bonded to panel centre-back. Panel surface: veneered, fabric-covered, or painted.

Construction sequence: install ceiling mounting plates, hang 4 elastic cords at corners, attach aluminium L-frame to cord ends, screw birch panel to frame from behind. Bond exciter to panel centre. Route speaker cable up through one elastic cord to ceiling box.

Panel tuning: thicker panel (8mm) = stiffer = higher resonance frequency = less bass. Softer elastic mounts = lower resonance. Aim for panel fundamental resonance at 80-100Hz for good bass integration with in-ceiling midrange drivers.

Cable Standards

Speaker cable gauge selection: 2x1.5mm2 to 12m run (below 0.5 ohm resistance per conductor leg), 2x2.5mm2 for 12-25m. Glass exciters and membrane drivers: 2x1mm2 screened sufficient (low power path, short run). Label all speaker cables at both ends with zone number and L/R before in-wall installation — after plastering, relabelling is impossible.

Connection to KNX amplifier: at the amplifier (Zennio ZAS-AUDIO8B rear panel), connect L+ L- and R+ R- per zone. No polarity issue on passive speakers, but wire all zones consistently (red to L+, black to L-, etc.) for professional presentation and future troubleshooting.