How to Properly Set up Razor Subwoofers Systems

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Notice: This guide was written specifically for Razor subwoofers but does apply to any 8” or 10” bag woofer installation.

Please take the time to read and fully understand this article if you want to get the most out of your Razor subwoofer system. 


It’s Not a Car

American Hard Bag subwoofers systems are designed specifically for Harley Davidson saddlebags and they are not designed to be setup the same way a subwoofer would be setup in a car or a boat or in a home. There are very important differences. The subwoofers are a completely different design so what you might already know about subwoofer systems will not likely apply here. 

DSR1 or Other Equivalent Sound Processor 

It is highly recommended that you use a digital sound processor in any sound system that is large enough of a scale to include subwoofers. Subwoofers on bikes in particular can benefit greatly from the added tuning flexibility that a good DSP adds to a system. You can find lots of information about how to best setup and use a DSR1 at https://www.americanhardbag.com/pages/installation-guides

The Basics

  • Crossover Settings
  • Radio Settings
  • Amplifier Power and Gain Settings
  • What to Know About Lid Speakers When Using Subwoofers
  • Relative Speaker Phase

You need to have the above conditions optimized if you want to get great results. A subwoofer on a bike is not as simple of a setup as it is in a car. If it is not setup correctly you will not get impressive bass.  

Crossover Settings↓

Razor subwoofers must be high passed (not low passed) at 40hz. This can be done using the crossover built into your amplifier but we recommend using a quality external crossover instead whenever possible (like the one built into the Rockford Fosgate DSR1). It is a very common mistake to low pass the subwoofers like you would with a car. DO NOT LOW PASS THE SUBWOOFERS.

Below is an example of the typical crossover settings that you will find on an amplifier. In step one set the crossover selector switch to HP (High Pass). In step two set the frequency dial to 40hz. 

Amplifier Gain Settings Harley Davidson Subwoofer

This will cut all music below 40hz. That is a critical step in getting high volume bass out of your bike. Below 40hz there is no bass that you will be able to hear on a bike. Not high passing the subwoofers at 40hz will result in the subs beating themselves to death and a much reduced output. This can also easily lead to overheating the subwoofer which voids its warranty.  

Below is a screenshot of how these same settings should be made when using a DSR1 processor instead of the crossovers built into your amplifier. The crossover settings in the DSR1 are much more accurate and effective than the crossovers that you will find on any amplifier. Do not use both the amplifier and DSR1 crossovers!

DSR1 SUbwoofer Crossover Settings for Harley Davidson

There are three settings to make here.

  1. Set for high pass
  2. Set the slope to 24db. Always use 24db per octave crossovers for all speakers ona bike system. 
  3. Frequency (40hz) 

Why we don’t low pass the subwoofers. 

The Razor subwoofers have an unusually smooth frequency response between 40 and 2khz. Subwoofers in other applications (car, boat, home) have a high voice coil inductance that makes the frequency response from 100hz and up sound very bad. So in those applications a low pass crossover is used to block out those frequencies. There is a distinct advantage to not low passing the Razor subwoofers. Allowing the subwoofer to play well into the midbass and lower midrange frequencies adds a lot of energy to that range of sound. Additionally the midbass energy (punch) is greatly increased when you have a single (or group of identical) speakers producing a wide frequency range without crossovers in that range. This has to do with the phase shift that all crossovers introduce into the audio signal.  

Why we High Pass the Subwoofers

By eliminating the lowest frequencies that we can’t hear, more energy can be focused on the region that we can hear. This amounts up to louder bass. 

Radio Settings↓

Factory Harley Radios (‘14 & Up)

Factory Harley radios need to be flashed using the Rockford Fosgate flash or a DSR1 with an American Hard bag tune must be used. Alternate flashes that are done with the factory Harley flashing system are not ideal for subwoofer systems. Bass tone controls must be set to zero (middle) and the speed controlled volume feature has to be turned off. Bass boost from the factory radio should never be used.  

Aftermarket Radios↓ 

Tone controls, loudness, and other “sound enhancement” features should not be used at the radio to boost bass. 

If using the subwoofer output of the radio, make sure that the output is not low passed 

Amplifier Settings↓ 

Amplifier power

It is a myth that more power gets you more output. A certain amount of power is required to get the speaker moving at maximum mechanical potential. That ideal amount is 100 - 150 watts depending on the music selection and recording quality. After that point driving the subwoofers with more power (Power = capable amplifier + volume level) is only creating heat in the voice coil and mechanical stress on the moving parts of the speaker. This does not result in more output or bass.  

Amplifier Gains

The gain control on the subwoofer amplifier should always be set last after the gain settings for all other speakers have been set and the bike is screaming loud. Then and only then turn the gain setting for the subwoofers so that the level of the subwoofers matches and compliments the rest of the system at high volumes.  

Starting with the subwoofer gain and then raising the rest of the system is not going to get you good results.  

What to Know About Lid Speakers When Using Subwoofers↓ 

The Razor subwoofers work really well with lid speakers as long as the lid speakers have the mechanical power to push back on the air pressure generated by the subwoofers. The cone material of the lid speakers needs to be sufficiently rigid and the surround of the speaker needs to be somewhat stiff. A loose bouncy speaker with a soft cone is a bad combination with any subwoofer.  

Air Space

The exact airspace inside the saddlebag and the effect that a lid speaker has on the available air space inside the bag when used along with Razor woofers is not critical to the performance of the Razor subwoofers. This is because the Razor subwoofers use a high Q design (resonant magnitude) that allows the subwoofer to operate just the same in a very wide range of enclosure volumes with minimal to zero effect on the subwoofer performance.  

Relative Speaker Phase↓ (Especially Lid Speakers) 

The following does not refer to how a speaker is wired. The speaker wiring must also be phase correct but the following refers to how in multi speaker systems the signal phase between channels is often out of alignment. The most misunderstood aspect to setting up a subwoofer system on a bike, especially with lid speakers is the subwoofers phase relative to the lid speakers (and other speakers on the bike). Phase refers to the direction of cone movement of one speaker in relation to the direction of cone movement of other speakers in a system. Speakers make sound by moving back and forth and pushing air. If you have a two speaker system and one speaker is pushing air in the opposite direction as the second speaker, the two speakers will at least in part cancel each other out. This is a much bigger potential problem when dealing with subwoofers than when dealing with smaller size (high frequency) speakers. So lid speakers that are out of phase with subwoofers can kill the bass. 

What Causes Speaker Phase Issues? 

The phase of a speaker is dictated by the phase of the signal. The signal path of a typical system starts at the radio then goes to the processor (DSR1) and then goes on to the amplifier and speakers. Whenever a crossover or an equalizer is used that signal channel ends up with a delay on it (milliseconds). That delay of the signal results in a phase shift relative to the other channels of the system.   

Example: 12db crossovers like those found on most amplifiers are notorious for inverting a signal (180 degrees). That is the equivalent of wiring your subwoofer backwards! So once you engage that crossover your subwoofer might very well be out of phase with the rest of the system.  

If your radios subwoofer output has a crossover that can’t be turned off you have another potential inversion of phase. If you use any equalization the signal gets shifted again. On each channel. So at the end of everything, phase of various speakers in a big system can be all over the map.  

In the real world we don’t know what the final phase result of a multi channel system is until we listen to the system and manually switch phase back and forth on various channels to see what the results are.  

How Do We Do That?! 

If you have a DSR1 processor it’s easy. The DSR1 has a feature that allows you to flip (invert) or incrementally adjust the phase of any system channel with a simple tap on your smartphone. This is a bit lengthy to explain but in practice a baby can do it. This is because the result is instant and the effect on the sound is usually profound. You don’t even have to really understand what is going on. Just try different combinations until you get the best bass. I highly recommend reading our article on our website “DSR1 Practical Phase and Time Alignment Tricks”. You can find it here: https://www.americanhardbag.com/pages/dsr1-practical-phase-and-time-alignment

 This is just another one of the many advantages of having a DSR1 sound processor in your sound system. You definitely can build a killer system without a DSR1 but If you don’t have one you are missing out.