Williams AV FM 557-24 PRO D – Dante FM+ Assistive Listening System, 24 Receivers

Product Overview

The Williams AV FM 557-24 PRO D is a Dante-enabled large-area assistive listening system built for mid- to large-sized venues that need ADA-compliant hearing assistance at scale. The package pairs the FM+ T55 D transmitter — which broadcasts over FM and Wi-Fi simultaneously — with 24 PPA R37N body-pack FM receivers, rechargeable battery infrastructure, and professional installation accessories. Because the transmitter accepts a Dante audio network input, integrators can feed program audio directly from a Dante-enabled DSP or mixer without analog conversion. It is a complete, rack-ready assistive listening package for auditoriums, houses of worship, and government assembly spaces.

Product Description

At the core of the FM 557-24 PRO D is the FM+ T55 D transmitter, a half-rack-width unit that transmits on 17 selectable wideband channels between 72.1 and 75.9 MHz while simultaneously streaming audio over the venue's existing Wi-Fi network to smartphones running the listening app. The Dante input lets the transmitter sit on the audio network alongside the rest of a commercial AV system, while the combination XLR/1/4-inch input still accepts balanced mic or line-level sources with selectable phantom power. DSP-based audio processing with selectable compression ratios and high-pass/low-pass filtering keeps speech intelligible for hearing-impaired listeners. A 3.12-inch OLED display, hosted web page, and Telnet-over-Ethernet control make the unit straightforward to configure and to integrate with third-party room control systems. The 24 included PPA R37N receivers tune across all 17 channels via a seek button, run up to 50 hours on alkaline cells or about 32 hours on the included NiMH rechargeables, and carry a Lifetime PLUS limited warranty. Two CHG 3512 12-bay drop-in chargers keep the full receiver fleet ready between events, and the ANT 005 remote coaxial antenna extends transmission range up to 1,000 feet. The RPK 005 rack panel kit mounts the transmitter in a standard 19-inch equipment rack, and the included IDP 008 ADA wall plaque signals hearing assistance availability to visitors. Note that FCC rules require professional installation with an approved FCC 15.203-compliant antenna, and the Wi-Fi stream requires an existing venue network. Smaller deployments can start with the FM 557 PRO D four-receiver package, and the full line of transmitters, receivers, and accessories is available in our Williams AV collection.

Key Features

• Dante Network Audio Input — The T55 D transmitter accepts audio directly from a Dante network, eliminating analog tie lines between the DSP and the assistive listening rack.
• Dual FM and Wi-Fi Transmission — One transmitter serves dedicated FM body-pack receivers and personal smartphones over the venue Wi-Fi network at the same time.
• 24 R37N Receivers Included — Two dozen body-pack receivers with surround earphones and six neckloops cover large audiences and satisfy ADA receiver-count requirements for bigger venues.
• Rechargeable Battery Infrastructure — Two CHG 3512 12-bay chargers and 24 NiMH battery sets keep every receiver charged and deployable without consumable battery costs.
• 17 Selectable Wideband Channels — Operation between 72.1 and 75.9 MHz allows multiple systems to coexist in adjacent rooms without interference.
• DSP Audio Processing — Selectable compression and filter settings optimize speech intelligibility for listeners with hearing loss.
• Network Control and Monitoring — A hosted web page and Telnet over Ethernet enable remote management and integration with third-party control processors.
• Rack-Mount Installation Kit — The RPK 005 panel kit mounts the half-rack transmitter in one EIA rack space alongside the rest of the AV rack.
• Extended Coverage — The ANT 005 remote coaxial antenna supports a transmission range up to 1,000 feet for full-building coverage.
• ADA Compliance Package — The included IDP 008 wall plaque and unlimited-listener FM broadcast help venues meet 2010 ADA hearing assistance guidelines.

Typical Applications

• Auditorium
• House of worship
• Government space
• Multi-purpose room
• All-hands room
• Commercial meeting space

Technical Specifications

Frequently Asked Questions

How does the Dante input integrate with an existing AV system?

The T55 D transmitter appears as a Dante receive device on the audio network, so you can route program audio from any Dante-enabled DSP, mixer, or paging system directly to the assistive listening transmitter over standard network cabling — no analog tie line required.

Does the Wi-Fi streaming feature require special network hardware?

The FM+ connects to the venue's existing Wi-Fi network; it does not generate its own. The network must be in place before the Wi-Fi audio stream can be used, and Williams AV publishes a WaveCAST networking guide with recommended configuration practices.

Can the system serve more than 24 listeners?

Yes. The FM broadcast supports an unlimited number of receivers, and smartphone users can join over Wi-Fi. Additional PPA R37N receivers can be added at any time as audience needs grow.

Is professional installation required?

Yes. The FCC requires this transmitter to be professionally installed with an approved FCC 15.203-compliant antenna (ANT 005, ANT 021, ANT 024, or ANT 025). Refer to the Williams AV Antenna Selection Install Guide during system design.

What warranty coverage is included?

The transmitter carries a two-year parts and labor warranty, and the R37N receivers are covered by a Lifetime PLUS limited warranty (earphones, headphones, and batteries excluded).

Does this package help meet ADA requirements?

Yes. The system complies with 2010 ADA guidelines for hearing assistance, includes neckloops for hearing aid users with telecoils, and ships with an IDP 008 ADA wall plaque to post assistive listening availability.