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Helix M Four Amplifier Installation Guide

1998 through 2013 Installation Note

It is not recommended to install these amplifiers in the fairings of bikes earlier than 2014. Substantial modifications and fabrication will be required for fitment in earlier year bikes.

Batwing Fairing Installation for 2014 and Later Bikes

The Helix M Four and M Four DSP amplifiers fit ‘14 and later Street, Ultra, and Electra Glides nicely without any modifications to the bike. The amplifier can be mounted on top of the radio using an amplifier mounting pad like the ones that come with American Hard Bag fairing amplifier power kits.

Be sure to locate the amplifier as far back as possible. Arrange the gauge cluster wiring so that the amplifier can be located right up against the rear of the gauges.

Road Glide Fairing Installation for 2015 and Later Bikes

A few simple modifications to the bike are required when installing an M Four series amplifier in the fairing of a Road Glide.Tip: Remove the fairing sub-harness by unplugging it from the chassis harness on the left and right sides below the radio (black and grey multi-pin connectors) while installing the amplifier. This will make the bike much easier to work on.


Shave off the tips of the upper headlight mounting tabs. Using a die grinder, take the material back to the outside of the threaded portion of both upper headlight mounting points. Do not cut into the threads. Only up to the outside of the threaded bung. Be sure to use a paint pen to paint the exposed metal.


Remove some plastic material from the headlight between the two upper mounting points (both left and right sides). This also can be done with a die grinder. Be sure not to grind past or into the brass inserts. Only remove the portion marked in red in the pic below.


Remove the two plastic wire retainer tabs at the front of the headlight. Cut them off and grind the surface flush. These two tabs are only for holding factory wire harnesses in place and are not structural. After the installation is complete these two mounting points will no longer be needed for those wire harnesses.

Once done, your headlight should look like the one pictured below. Note that a little satin black spray paint can be used to make the headlight look unmodified. 


Route the power cables and tie the factory wire harnesses behind the headlight so that they will stay clear of the amplifier when it is installed. In the pic below the arrows point to where zip ties should be placed in order to keep the harnesses to the far left and the far right. The white pointers show the route of the power cables. Run the cables from the battery forward, and then route the cables alongside the throttle side harness. Thread the cables through the triangular hole in the radio bracket under the radio, and then route them down into the amplifier mounting area. Leave enough length in the cables so that the amplifier can slide out and be serviceable.


Install a sheet of Velcro to the rear of the radio bracket. Only use the soft fuzzy side. Do this so that the amplifier can be positioned as far back in the fairing as possible without causing abrasion issues for the cables. The amplifier should be arranged with the power cables and speaker connections to the rear and the signal input/output to the front of the bike. If you decide to use wire ferrules on the ends of the power cables be sure to remove the plastic insulators (cut them off with wire cutters), and use heat shrink tube in place of the insulator. There will not be enough room for the added space that the wire ferrule's insulators require. As with any amplifier installation, be sure that there is no exposed wire at all outside of the amplifier power terminals even when the cables are bent upward at 90 degrees. This can be accomplished by using heat shrink tube that extends past the end of the power cable insulation as pictured below. When the cables are inserted into the amplifier the heat shrink covered wire should extend right into the power terminal by about 5/16 of an inch. You will want to strip off an extra long portion of the power cables insulation than you otherwise would. About 1.25 inches worth.

With the headlight reinstalled in the bike, it should now look like the pic below.


Install Velcro on top of the headlight where indicated in the pic below.

Install a matching section of velcro to the underside of your amplifier. Now put your amplifier in the bike as shown below. Be sure that the amplifier is placed as far back as possible.


Modify the radio harness. The radio harness has two plastic components that need to be removed in order for the harness to clear the top of the amplifier once the radio is installed.

Mark the C-shaped latch mechanism with a silver sharpie to indicate the side that faces up when plugged into the radio. Also, mark the top side of the connector housing. Remove the C-shaped latch mechanism. When clocked in the correct position, the latch can be pried outward and removed. Set it aside for now.

Remove the cone-shaped plastic wire cover from the back of the multi-pin connector. You will find two very small retaining tabs that can be bent outwards to release the cover. The cover is on plastic tracks and slides to the side to be removed.

Cut the C-shaped latch you removed in the first step so that it is now two parts without the lever.

Radio Signal Input

When using an aftermarket radio with RCA type signal connections, use the low level RCA inputs of the Helix amplifier. Note:you must enable RCA input in the PC-Tool software later when setting up your amplifier with a PC. 

When using a factory Harley radio, follow the directions below for signal input. 


Front input signal is acquired by disconnecting the front fairing speaker pods and connecting the male black two pin Molex connectors pictured above. The two male black two pin Molex connectors are then connected to Channel A and B high level inputs.

Now that you have re-routed the front signal to the amplifier instead of the fairing speakers, nothing is connected to the fairing speakers. Use the included fairing speaker pod connectors to connect the fairing speaker pods to the amplifier speaker outputs. These connectors are two pin female with 18" long wire leads on them.

Some CVO Models: Black four pin Molex connector under seat on top of battery cover.


If you got an optional rear signal adapter for your helix amplifier, you will need to connect the rear signal adapter to high level inputs C and D of the amplifier. Then connect the Molex end of the adapter into the rear speaker output of your bike. The rear speaker output of your factory Harley radio will be in one of three locations depending on the model of your bike.

Ultra Models: Under the seat at the tour pack quick disconnect point.

Non-Ultra Models: Behind radio in four pin male Molex connector. Connector is black with a rubber plug in it. Note that non-Ultra models will need to have the radio flashed if you want to use the rear outputs of the radio to be active. As pictured below.

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Helix M Four Amplifier Installation Guide

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