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Ultimate Harley Radio Flash Guide for Aftermarket Speakers and Amplifiers

The following is a complete guide to performing your own radio flash and getting all of the performance you ever wanted out of your factory 2014 or newer Harley Davidson radio. This guide assumes that you already know what a radio flash is and have some idea of why you need to get one done, but I will explain the details of what options you should program for and why. Be aware that there is a ton of misinformation out there about what flash you should get and who should do it. This article sets the record straight. Be careful of the blind leading the blind on forums and Facebook.


A proper radio flash will get the best features of your radio turned on but you still need to make the right choices when connecting your new gear to your radio. Always use the proper Harley radio signal harnesses from American Hard Bag so that the radio is properly loaded and balanced, and never use high to low level converters. Skipping the correct interface harnesses will result in a bunch of new problems that you don’t need and ultimately amplifier and speaker failures. You can find all of our factory radio integration harnesses here.



The first thing you need to do is decide if you will have your bike taken to a shop to have the flash done for you or if you will be doing the flash yourself. In either case the same software will be used and in either case you should be aware of all your options.

Let’s be clear. The factory system that Harley dealers use to flash a radio is not what you should be using. All factory Harley flashes are intended to be used for factory Harley speakers and amplifiers and not aftermarket equipment.

There is only one flash tool to use. It’s made by a company called TechnoResearch. Fortunately Virtually all non-Harley bike shops that have a flash tool, have a TechnoResearch tool. This tool has become so popular that many factory Harley dealerships now also have this tool that they use as well as their factory supplied equipment. So in this article I will only be referring to the TechnoResearch tool and software.


What Do You Want to Accomplish by Flashing Your Radio?

Here are some of the things you can accomplish

  • Enable or disable the rear audio channels. This is an important setting since all bikes that originally only came with two speakers have the rear channels disabled, so there is no fader ability. Also bikes that came with factory amplifiers have no fader ability once the factory amplifiers are removed from the system. So those bikes also need to be flashed to a configuration that enables fading to the rear channels without the factory amplifier(s) in place.

  • Enable or disable the factory amplifier status. There is a secondary menu that allows you to tell the radio that a factory amplifier is or is not present for front channels and for rear channels. If you enable the amplifier option, the audio signal on those channels will drop to a voltage level of just under 2 volts. This is a good thing for most aftermarket sound processors and amplifiers. It keeps the signal from being too high and clipping the inputs of the following device in the audio chain. For those of you who plan to use the factory radio's onboard power to directly drive your speakers in lieu of an aftermarket amplifier, it is important that you set your channels to disable factory amplifier status for both front and rear. This will boost the audio output from the radio to around 10 volts, which is what you need to directly drive a speaker.

  • Enable Apple CarPlay without the need for any special hardware or adapters (GTS Radio Only)


If you are going to be using aftermarket amplifier(s) simply load the Rockford Fosgate flash profile as shown in the video. The Rockford Fosgate flash profile works equally as well with all aftermarket amplifiers and speakers (not just Rockford). Though the point of this article is to explain many of the fine details of flashing your factory radio, there is a single flash solution that takes care of multiple settings all at once. So let’s just do that.

This Profile Will

  • Reduce Audio Signal to Line Level

  • Load a Great Sounding EQ Curve (better than flat)

  • Enable Rear Speaker Output

  • Enable Amalog Fade Function

  • Enable Tone Controls



The TechnoResearch software is simple enough but it does have one quark that you should know about.When launching the app (PC only), nothing will happen when you click on the yellow Centurion Audio button. This is normal. Don’t go clicking it several times. Unlike an elevator or a crosswalk, clicking this button several times will not make anything happen any faster. The reason that nothing happens right away is that the app has to communicate with TechnoResearch servers via an internet connection for authorization before moving on to the next step.



In this video, we take you through each step of enabling CarPlay to your GTS radio using the TechnoResearch flash tool. It is very simple unless you have never done it before. The menu and procedure for adding CarPlay is a bit hidden and not at all self-explanatory. This video makes it simple.

Enabling CarPlay can be done on GTS radios (2019 and later) but not on GT radios (2018 and earlier). CarPlay works from the factory on GTS radios but only if you add a headset or if you buy a special wire harness that emulates a headset being attached to the bike. But with the TechnoResearch flash tool, you can enable CarPlay and skip any need for additional hardware. It is just a click of a button and it is free!



The next step is to get your hands on the right plug & play adapters so that you can now connect your factory Harley radio to your aftermarket amplifiers and speakers.

Here Is What People Often Do Wrong

  • They use a line leveler or high-to-low-level adapter (big mistake!). These devices are junk and never have a place in a bike sound system. Line levelers are old-school car audio parts that were originally made for adding a subwoofer amplifier to a factory car radio back in the days of tape decks. These adapters mess your sound up on multiple levels.

  • They use amplifiers that do not have a high-level input. Any good amplifier will either have a dedicated speaker-level input or even better will be able to accept a speaker-level input over an RCA-type connection. All Velocity Speaker Design amplifiers for example can handle the full speaker-level output of any Harley radio directly at the RCA inputs. No line levelers are ever required.

  • They don’t use Harley radio adapters with built-in load circuits. American Hard Bag radio to RCA adapters have a specialized load circuit built right into them that keeps your factory radio happy when using a DSP or aftermarket amplifier. At American Hard Bag we make the right adapter for your factory Harley radio.



The answer to that question depends on two things.

  1. What type of speakers are you using? Pro audio type speakers (speakers with horns or designed to work with horns) for example are designed to work with a DSP to function properly. If you are using pro audio type speakers you should definitely get yourself a good sound processor. Consumer-level speakers on the other hand (such as car audio speakers) are designed to sound pretty good right out of the box at the expense of output. Even the best and most expensive consumer-level speakers can not produce the level of output of even a mediocre pro audio speaker.

  2. What are your expectations? If you have higher aspirations than just making a bunch of noise then you should get yourself a DSP. Also keep in mind that a DSP allows you to squeeze a lot more output as well as sound quality out of your sound system. Even if making a lot of noise is your highest priority, you should still probably get your hands on a good DSP.


A Harley sound system with consumer-level speakers and moderate output can often be successfully set up without a digital sound processor, but if you are going big with your audio system you need a DSP. The only exception to this rule that we have ever seen is when using Velocity RZ65H and RZ69H speakers. These speakers though hold no resemblance to other pro audio speakers. We designed these speakers to function exceptionally well without a DSP. As of the writing of this article, we know of no other pro audio type speakers that can accomplish this feat.


Not All Sound Processors Are Good Sound ProcessorsHere at American Hard Bag we have access to pretty much any digital sound processor ever made but what we have found out over the years though is that many of the sound processors out there have no place in a Harley sound system. So be careful about what sound processor you get into. At American Hard Bag we only sell DSP units that have a high reliability, no noise issues, and that fit properly in the fairing.

These Processors Are

DSR1 - Simple, Effective, Reliable, No Advanced FeaturesMusway M4+ - All In One Amplifier/DSP Solution, Simple, Effective, Some Advanced FeaturesVelocity 8 - Reliable, Small, Built-In Amplifier for Tweeters, Very Advanced Features

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Ultimate Harley Radio Flash Guide for Aftermarket Speakers and Amplifiers

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