This product is available through authorized resellers.

Request Quote

The CLS1 is a professional installation loop driver capable of driving loop areas in excess of 2,150 sqft. (200 m²) with an unsurpassed clarity of sound for both music and speech for superior intelligibility. Designed for simple discrete installation, the CLS1 offers the most cost effective and capable solution in its class. The driver is very compact and designed specifically for wall mounting. All connections and controls are secured behind a tamper resistant, hinged, detachable cover. Combined with its small size, the range of mounting and cabling options ensure that installation is convenient and tidy in any environment. Input options are comprehensive, with three independent inputs for balanced microphone, balanced and unbalanced line, low impedance and 100 V line speaker systems.


One (1) CLS1 Installation Loop Driver (3.5 Amps)
One (1) Handbook and Installation Instructions
One (1) “T” Logo Installed Adhesive Sign – Large (11.7″ x 8.3″)
One (1) P-clip, Nut and Washer


  • Area coverage to 2,150 sqft. (200 m²)
  • Designed for simple discrete installations
  • Simple and fast installation
  • Wall mounted
  • Low lifetime cost
  • Excellent proven reliability
  • 5-year warranty
  • Unparalleled sound quality and intelligibility
  • Speech optimized gain control
  • Metal loss corrector corrects frequency dependent loss from metal structures
  • Extensive input adaptors available for any audio input requirements
Configurations & Architectural Specs


CLS1 Installation Loop Driver (3.5 Amps)

Architectural Specs

The Installation Loop Driver shall, in accordance with IEC60118-4, continuously deliver 3.3 A (RMS) when excited with a continuous 1 kHz sine wave. It shall cover an area of at least 2,150 sqft. (200 m²) with a room aspect ratio 3:1 according to IEC 60118-4:2006 standard.  The driver shall have a frequency response of at least 80 Hz to 6.5 kHz +/- 3 dB with THD+N less than 0.2%.  The unit shall incorporate audio processing to maximize the intelligibility for individuals with a t-coil hearing aid.  The unit shall incorporate metal loss correction to rectify frequency caused adjacent metal structures.  The unit shall be wall mounted and all cables shall be terminated within the wall enclosure.  The CLS1 Installation Loop Driver is specified.

Product Specifications


Frequency Response80 Hz to 6.5 kHz ± 3 dB
DistortionTHD+N < 0.2 %, 1 kHz Sine Wave at Full Current
AGCOptimized for Speech, Dynamic Range > 36 dB


Gain ControlFront recessed input level control
Metal Loss CorrectionCorrect system frequency response due to metal structures
CoolingNatural Convection


LEDsAGC is Activated, Loop Current, Power
Drive Current IndicationLED


Loop Connector/sScrew Terminal


Input/sInput 1: Balanced Mic/Line (-73/-31 dBu), 12 VDC Phantom Power, Input 2: Balanced Line (-33 dBu), Input 3: Isolated 100 V/ Low Impedence Mono/Stereo Speaker, Input Impedance (Ohms) 120k, 120k, 7.8k, Min Level (dBu) +14/+14/-9, Max level (dBu) +47/+47/+27


Perimeter Loop - Coverage1:1 Aspect Ratio - 1,290 sq ft. (120 m²), 2:1 Aspect Ratio - 1,615 sq ft. (150 m²), 3:1 Aspect Ratio - 2,150 sq ft. (200 m²)Condition 1 - Loop must be 3-6 ft. (1-2 m) above or below the receiver height, Condition 2 - There should be no metal structures in the plane of the loop, Condition 3 - There must be sufficient voltage to drive the loop


ComplianceETL Listed
Power230/115 VAC, 30W, 45-65 Hz, Connected via Chassis Screw Terminals
Drive Voltage6.4 V (RMS) at Maximum Output Current
Drive Current3.5 A (RMS), 5.0 A (Peak) with 1 kHz Sine Wave
Drive Current PeaksShort Term > 7 A
Input Power FuseT250 mA


Width7.9 in. (200 mm)
Height1.7 in. (44 mm)
Depth7.9 in. (200 mm)
Shipping Weight5.1 lbs. (2.31 kg)
MountingVertical Panel Mounting
Cable Length10 AWG - Max distance at full current - 357 ft. (109 m), 14 AWG - Max distance at full current - 330 ft. (101 m), 18 AWG - Max distance at full current - 224 ft. (68 m), 22 AWG - Max distance at full current - 125 ft. (38 m), FB1.8 - Max distance at full current - 436 ft. (133 m)
Weight4.0 lbs. (1.81 kg)


Relative HumidityIP20 Protection, 20 to 90% Relative Humidity, 32 F (0 C) to 95 F (35 C)
Used With
QShould I purchase a field strength meter?
AAbsolutely, it’s the only way you’ll be able to determine if a loop system is operating properly. Any venue that owns and operates a loop system should also have some equipment to monitor the operation of the loop on a regular basis. This should either be a field strength meter (R1), (FSM) or a receiver with field strength indication (IR-IL-1).
QWhat is an array system and how do I design one?
AAn array uses two loop drivers and an SP5 phase shifter to create two overlaid magnetic fields, capable of accurately controlling the field within and around the loop system. They can be used to prevent ‘spill’ of magnetic field allowing loops to be used in adjacent rooms, and to give good even coverage in areas with metal building structures or complex installations. Arrays need a special layout design that can be provided by Listen. Arrays will always give a better field coverage and higher certainty of excellent performance than a perimeter loop, however the installation is more demanding and requires loop cables to cross the floor or ceiling of the area of use.
QWhat audio input should I use on an induction/hearing loop?
AEither an existing audio system can be used, or a dedicated microphone or other audio source may need to be provided. The objective is to ensure the loop system receives the required audio source (e.g. a voice) and not any background noise. The most essential job of any assistive listening system is to increase the level of the signal (the voice) relative to the background.
QWhich type of cable should I use for an induction/hearing loop?
AFor cable intended to go under a carpet, you should use 1.8mm2 flat copper tape. Otherwise, you should choose the cable based on the maximum total cable length in the specifications chart.
QWhat is spill or overspill?
AOverspill occurs when the magnetic field created by hearing loop can be heard outside of the looped area (such as a room). The field is “spilling” outside of the looped area and can affect other nearby loop systems.
QHow do you minimize overspill?
AThis is done by using an array, consisting of two loop drivers and a SP5 phase shifter that controls the field within the looped area and reduces it rapidly outside the loop perimeter. The overspill can be reduced to as little as 5 ft (1.5m) with a good design.
QWhat is metal loss correction?
AMany buildings have embedded metal in the structure such as reinforcements in concrete, metal computer floors or suspended ceiling grids. This metal causes a distortion of the frequency response if the metal is in the same plane as the loop cable. The metal loss correction equalizes the audio to make up for or “correct” this loss. Note that metal loss will also reduce the signal level in general, and may require additional power, or indeed an array system to achieve the right level of performance.
QWhy do loop drivers have extensive audio processing?
ABecause the people who benefit from hearing loops (individuals with t-coil hearing aids), have limited dynamic range due to hearing loss. Thus, these users require significantly reduced dynamic range so they can hear the softest of sounds and so that very loud sounds are brought to nominal level.
QWhy is it important for a loop driver to be ‘constant current’?
AA current drive or constant current driver will deliver a current to the loop that is independent of the loop impedance. A normal audio amplifier will not be able to deliver constant current into a loop, meaning lower output at higher frequencies where the loop impedance is higher. A constant current driver can deliver flat frequency response, essential for delivering intelligible sound and performance that meets the loop performance standard.
QHow do I choose which loop driver is best for my installation?
AGenerally, this depends on the size of the room, the construction of the building, and the type of loop system you need. Refer to the Designing a Hearing Loop System Guide and Listen support to help you specify and design your system.
QWhen should I use a perimeter loop system and when do I need an array?
AA perimeter loop is the simplest form of loop system requiring a single loop of cable around the area to be used. However perimeter loops cannot be used if (1) other loop systems or areas where t-coil receivers are used are nearer than 3 times the room width (shortest side); (2) the room width is over 15ft and there is significant metal in the plane of the loop, such as reinforcement in a concrete floor. In these cases an array system is usually required. You may be able to conduct a site survey to confirm whether an array is necessary – contact Listen for details.
Copyright © 1998 - 2020 Listen Technologies Corporation. All rights reserved.
Listen, ListenPoint and related marks and logos are registered trademarks of Listen Technologies Corporation. Terms of Use | Privacy Policy
Listen Technologies