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

Product Overview

The Williams AV FM 557-24 PRO is a large-area assistive listening system package sized for auditoriums, worship spaces, and other mid- to large-sized venues that must provide ADA-compliant hearing assistance. The FM+ T55 transmitter broadcasts on FM and streams over the venue Wi-Fi network simultaneously, while 24 PPA R37N body-pack receivers serve listeners who prefer dedicated hardware. The PRO package adds the installation accessories integrators expect — a remote coaxial antenna, rack panel kit, 12-bay chargers, and rechargeable batteries — so the system arrives rack-ready.

Product Description

This package is built around the FM+ T55 transmitter, the successor to the long-running T45 FM transmitter, which adds simultaneous Wi-Fi audio streaming for nearly the cost of a traditional FM-only system. The transmitter occupies half of one EIA rack space and mounts in a standard 19-inch rack using the included RPK 005 rack panel kit. Audio connects through a combination XLR/1/4-inch jack accepting balanced or unbalanced microphone or line-level sources, with selectable phantom power for condenser microphones. Onboard DSP provides selectable compression and high-pass/low-pass filtering tuned for speech intelligibility, and a 3.12-inch OLED display plus a hosted web interface make setup and day-to-day monitoring straightforward. For control system integration, the unit supports Telnet commands over its rear-panel Ethernet port. Each of the 24 PPA R37N receivers seeks across 17 wideband channels between 72.1 and 75.9 MHz, includes an EAR 022 surround earphone, and runs roughly 32 hours per charge on the included NiMH batteries — two CHG 3512 12-bay drop-in chargers manage the entire fleet. Six NKL 001 neckloops support hearing aid wearers with telecoils, and the IDP 008 ADA plaque posts hearing assistance availability at the entrance. The ANT 005 remote coaxial antenna delivers transmission range up to 1,000 feet; FCC rules require professional installation with an approved antenna. If your venue also needs Dante network audio input, see the FM 557-24 PRO D Dante package, or browse the complete Williams AV collection for receivers and accessories.

Key Features

• Dual FM and Wi-Fi Broadcast — A single T55 transmitter serves FM body-pack receivers and smartphone listeners on the venue network at the same time.
• 24-Receiver Fleet — Twenty-four PPA R37N receivers with surround earphones meet the receiver counts ADA guidelines call for in large assembly spaces.
• Complete Charging Solution — Two CHG 3512 12-bay drop-in chargers and 24 sets of AA NiMH batteries eliminate disposable battery management.
• Professional Install Kit — The RPK 005 rack panel kit and ANT 005 remote coaxial antenna prepare the system for a clean equipment-rack installation.
• 17 Selectable Channels — Wideband operation from 72.1 to 75.9 MHz lets multiple systems run side by side in multi-room facilities.
• DSP Speech Processing — Selectable compression ratios and filter settings keep amplified speech clear for hearing-impaired listeners.
• Web and Telnet Control — The hosted web page and Ethernet Telnet interface integrate with third-party room control systems for remote management.
• Telecoil Support — Six NKL 001 neckloops couple audio directly to hearing aids and cochlear implants equipped with telecoils.
• Unlimited Expansion — The FM broadcast accommodates any number of additional receivers as audience demand grows.

Typical Applications

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

Technical Specifications

Frequently Asked Questions

What audio sources can feed the transmitter?

The T55 accepts balanced or unbalanced microphone or line-level audio through its combination XLR/1/4-inch input, with menu-adjustable input gain and selectable phantom power. It connects easily to a DSP output, mixer bus, or dedicated microphone.

How does Wi-Fi listening work alongside the FM receivers?

The transmitter joins the venue's existing Wi-Fi network and streams the same program audio to listeners' smartphones, while the FM broadcast serves the included R37N body-pack receivers. The system does not create its own network, so venue Wi-Fi must be in place first.

Can multiple FM 557 systems operate in the same building?

Yes. With 17 selectable wideband channels between 72.1 and 75.9 MHz, several systems can run simultaneously in adjacent rooms as long as each is assigned a different channel.

Does the package require professional installation?

Yes. The FCC requires professional installation with an approved FCC 15.203-compliant antenna. The included ANT 005 is compliant; consult the Williams AV Antenna Selection Install Guide when planning the install.

How is the system controlled within a larger AV installation?

Beyond front-panel OLED navigation, the transmitter hosts a configuration web page and accepts Telnet commands over Ethernet, allowing integration with third-party control processors for remote monitoring and management.

What warranty applies to this system?

The transmitter is covered for two years parts and labor, and each PPA R37N receiver carries a Lifetime PLUS limited warranty, excluding earphones and batteries.