Notice: This guide applies to any 8” or 10” bag woofer system.

Please take the time to read and fully understand this article if you want to get the most out of your Harley system. When done correctly, adding bag woofers to a Harley system can make the system much more spectacular and powerful sounding. 

Important Differences

A bike is not a car. In a Harley application the bag woofers are there to reinforce what the other smaller speakers on the bike are already doing. Bag woofers and subwoofers on a Harley are not stand alone subwoofer systems. The bag woofers whether they are subs, mids, or full range, are there to make the other smaller speakers sound much more powerful. Unlike a car audio subwoofer where the sub plays in it's own range that is not shared with the other speakers. On a bike the bag woofers share the same or part of the same frequency range and do not have a stand alone dedicated range. There for, overdriving the bag woofers with too much gain or boosting the bass range with an EQ will not get you the same effect as a car and will quickly lead to overheating and destroying the woofers. 

The speakers on a bike system have a much higher demand on them than car speakers do. This is because cars are very reflective. The sound bounces off of the hard surfaces in the car right back at you. On a bike, once the sound leaves the speaker, it is gone. There is no reflection and consequently the speakers must work much harder to produce the same amount of sound. And none of that takes into account all of the street and engine noise that a Harley system has to overcome to be heard.

It Is Very Important

It is critical to understand that the bag woofers need to be adjusted and aligned with all of the other speakers on the bike if you want to get maximum performance. They will not perform properly on their own. They are not intended to. 

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 (or any bag woofers) 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 here.

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 performance. But when things are done right, the bike is amazingly more authoritative sounding and can play much louder.   

Crossover Settings↓
Bagger subwoofers must be high passed (not low passed) at 45hz. 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 45hz.


This will cut all music below 45hz. That is a critical step in getting high volume bass out of your bike. Below 45hz there is no bass that you will be able to hear on a bike. Not high passing the subwoofers at 45hz 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!

Note: The exception to this rule is if you are using an amplifier with a built in DSP like the Helix and Musway amplifiers. The crossovers in those amplifiers are more than capable for this application. 

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 on a bike system.
  3. Frequency (45hz)

Why we don’t low pass the subwoofers.
Any good subwoofer or woofer for a Harley application will have an unusually smooth frequency response between 45 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 bagger subwoofers. Allowing the speaker to play well into the mid-bass and lower midrange frequencies adds a lot of energy to that range of sound. Additionally the mid-bass 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. Any frequency response corrections that we want to address for the subwoofers above 100hz should be done with the EQ.

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. Some radios do not let you turn off the subwoofer low pass crossover. The subwoofer output of these radios should not be used. Use the rear channel output instead. 

Amplifier Settings↓
It is a myth that more power always gets you more output. It is also a myth that you need to meet or exceed the speakers printed power rating. A certain amount of power is required to get the speaker moving at maximum mechanical potential. After that point more power will only generate more heat and damage the speaker. The ideal amount of amplifier power is far below the power rating of the speaker. The power rating of the speaker is the maximum amount of power that the speaker can handle before melting down. RMS power is the melting point if run for long periods of time. Max power is the melting point in a very short amount of time.  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↓
All bag woofers and subwoofers American Hard Bag sells 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 all woofers American Hard Bag sells is not critical to the performance of the woofer. This is because the woofers we use have 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 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. 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.