Acoustic Image Corus Series IV Combo Amplifier 2010s - Black

The Acoustic Image Corus is a highly regarded, ultra-lightweight solid-state combo amplifier specifically engineered for acoustic and clean electric stringed instruments (such as jazz archtops, nylon and steel-string acoustic guitars, violins, and mandolins).

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While Acoustic Image initially built its reputation serving upright bassists with their Contra and Coda models, the Corus was specifically tuned to provide a more forward midrange presence and tailored bass response ideal for higher-voiced instruments.

Key Design Philosophy & Features1. The Enclosure and Speaker Configuration

The Corus uses a distinct, cylindrical, injection-molded polymer enclosure that is acoustically inert and keeps the entire unit extremely light (typically between 19 to 22 lbs, depending on the Series generation).

• Downward-Firing 10-inch Woofer: Instead of a traditional front-facing cabinet, the low-end driver fires downward against the floor. This omnidirectional design creates a wide, 3D soundstage that fills a room and allows bandmates to hear you clearly without harsh "beaming."
• Front-Firing 5-inch Midrange Driver: Delivers clear, articulate high-mid and treble response directly forward.
• The "Corus" Voice: Unlike the Coda model, which extends flat down into the sub-bass for upright bassists, the Corus utilizes a modified woofer and crossover (typically crossed over around 800 Hz) to roll off frequencies below 60 Hz. This eliminates low-end mud, reduces feedback prone to acoustic tops, and pushes the crucial mid-range slightly forward to help guitars cut through an ensemble mix.

2. The Head / Preamp System

Depending on the generation (Series III, Series IV, or S4/S4+), the Corus paired its cabinet with Acoustic Image’s legendary Clarus Class-D power amplifier section.

• Cabrio Docking System: In later generations, the amplifier head can be physically unlatched and slipped out of the combo chassis. This allows you to use the lightweight head independently for direct recording or to drive a separate external speaker cabinet (like a Raezer's Edge).
• Massive Headroom: Despite its size, the integrated Class-D power amp delivers huge, uncolored power—ranging from 400W to 800W at 4 ohms depending on the specific series version.