Gain Setting Procedure
Set the radio fader, bass, and treble to center positions.
Turn off the speed controlled volume feature on the radio. This is simply a feature that you have to give up in order to fulfill your ultimate thirst for sound. Sorry dude.
Dry set your crossovers to a conservative and known safe setting, and set all your amplifier gains to 50%. Be sure that your crossover settings are set and functioning by listening to each speaker individually at low volume levels. Once you are confident that you are not sending subwoofer signals to your tweeters you can proceed to turn your radio's volume level up until one of two things happen.
- The speakers show signs of reaching their physical limitations. This is relatively safe as long as you don't push the speakers for an extended period of time.
- You reach 75% radio volume. In most cases (but not all. It depends on your particular radio flash) you never want to run your radio's volume past 75% even if you can not hear distortion or even test for it with specialised equipment.
Now you need to either turn your gains up or down.
- If you can not reach 75% volume with your radio before the speakers reach their limits then the gains need to come down.
- If your radio volume reaches 75% volume and the speakers are not playing to their potential, then the gains need to go up.
Now turn the radio volume all of the way down. Listen for hissing coming from the speakers. If the hissing is excessive the gains need to be turned down. The goal is to reach a happy balance between how loud the system can play at 75% radio volume and how much hiss (noise floor) you get with the radio at low or zero volume.
Tip: you are better off having the gain set too high rather than too low. Gains that are too high produce a hiss at zero volume. Gains that are set too low fry speakers and amplifiers! Pick your poison. There is plenty of happy middle ground. Small changes in gain can make big changes in the level of noise floor.
That's pretty much it. Reality dictates that most bikes will have some amount of hiss at zero volume. This is because we generally over gain Harley audio systems in an effort to reach ultimate volume levels. Having said that, the noise floor at zero volume should not be alarmingly loud. If this is the case, then something has been missed. Read on to the next section that covers troubleshooting. What is important here is that we leave some room in the volume range on the radio so that we are far away from distortion. We know that the factory radio is particularly susceptible to high frequency distortion and we also know that small changes in charging system voltage leads to large changes in amplifier performance and ultimately amplifier distortion. The smart move is to give the entire gain structure of your audio system some room for these fluctuations in order to avoid damage to speakers and amplifiers.
- If you are using a DSR1 sound processor, be sure that the trim levels for all channels are at max (default value). Only use the trim levels to attenuate speakers slightly as needed once the gains are all properly set. For example: it is common to attenuate horn tweeters using the trim levels on the DSR1.
- An excessive noise floor can be caused by not grounding all amplifiers directly to the battery negative terminal. Never ground to any part of a Harley chassis. Also always get both power and ground for a DSR1 directly from an amplifier power terminals or run 14 gauge power cables directly to the battery (fused).
- An excessive noise floor can be caused by tweeters being over gained. All tweeters and especially horn loaded tweeters are much much more efficient than the mid woofers that they are paired with. You may ultimately decide to run your tweeters at a higher level than the rest of the speakers on your bike in order to overcome wind noise, but this will exacerbate noise floor issues. A horn tweeter for example that is wired in parallel with a mid woofer on the same channel will always play at an excessively higher volume level than the woofer. This might even be the volume that you want the tweeter to play at. Resistors can be used in line with the tweeter to lower the volume level. If though you run your tweeters in parallel with your mid drivers, a higher noise floor should be expected. Find that happy balance.