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The CLD1 Compact Loop Driver is designed for counter systems and small area perimeter loop systems. Measuring only 5 x 2.9 x 1.4 in. (128 x 74 x 35 mm) and with an output current of 2.4 A (RMS), the CLD1 is the smallest and highest performance amplifier in its class. Based on proven and highly reliable technology it is backed by a 5 year warranty and Listen technical support. The CLD1 offers certainty of performance and the lowest lifetime cost available.

Audio quality is ensured with metal loss correction (MLC) combined with usual high standards of design. The CLD1 is designed for flexibility and convenience, featuring two (2) separate microphone inputs with independent level controls, one of which can be configured as a line input. All cable connections are made on a single face of the unit, adding flexibility and further simplifying installation.


One (1) CLD1 Compact Loop Driver
One (1) Handbook and Installation Instructions
One (1) 12 VDC Power Supply (North America)


  • Low lifetime cost
  • 5 Year warranty
  • Very compact
  • Two (2) independent inputs featuring one (1) microphone input and one (1) switchable microphone/line input
  • Metal loss compensation
  • All connections to a single face for installation convenience
Configurations & Architectural Specs


CLD1-XX Compact Loop Driver (No Mic, No Loop)

Architectural Specs

The audio hearing loop driver shall, in accordance with IEC60118-4, continuously deliver 2.4 A (RMS) when excited with a continuous 1 kHz sine wave. It shall cover an area of at least 377 sqft. (35 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 equipped hearing aid. The unit shall incorporate metal loss correction to rectify frequency caused adjacent metal structures. The CLD1-XX Compact 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
Microphone InputUnbalaced 3.5mm Mono Connector for Electret Micorphone, 6 VDC Bias
Line InputSwitchable Line/Microphone, Unbalaced 3.5mm Mono Connector


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


Drive Current IndicationFront Panel LED Indicates Current Peaks


Loop Connector/sLevel Cable Clamp


Perimeter Loop - Coverage1:1 Aspect Ratio - 215 sq ft. (20 m²), 2:1 Aspect Ratio - 323 sq ft. (30 m²), 3:1 Aspect Ratio - 377 sq ft. (35 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


VOX SwitchingTo control prioritization of micorphone 1 input
ComplianceUL Listed
Power12 VDC, 1.0 A, 18 W, 45-65 Hz, Power Switch/Led on Front Panel
Drive Voltage3.2 V (RMS), 4.5 V Peak at Maximum Output Current
Drive Current2.4 A (RMS), 3.4 A Peak with 1 kHz Sine Wave
Drive Current PeaksShort Term > 4.8 A


Width5.0 in. (128 mm)
Height1.4 in. (35 mm)
Depth2.9 in. (74 mm)
Shipping Weight1.7 lbs. (0.77 kg)
MountingFreestanding, Wall Mounting
Cable Length10 AWG - Max distance at full current -268 ft. (82 m), 14 AWG - Max distance at full current -247 ft. (75 m), 18 AWG - Max distance at full current - 168 ft. (51 m), 22 AWG - Max distance at full current - 94 ft. (29 m), FB1.8 - Max distance at full current - 328 ft. (100 m)
Weight1.0 lbs. (454 g)


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.
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.
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