15RGPFK Installation Instructions
Diamond MO75T Horn Alignment
The 15RGPFK speaker grills come with the horns already installed. If you find that the horn needs to be rotated slightly so that the Diamond Audio logo is square with the rest of the bike, simply loosen (but do not remove) the four Phillips screws and adjust the alignment of the horn. Then retighten.
MO75T Horn Rotation
Notice how the tweeters speaker leads are pointed up? If yours are not already arranged with the speaker leads pointing up, don't twist or bend them up. Instead you should remove the four small Allen screws from the back of the horn, remove the backplate/voice coil, and rotate it 180 degrees. Then replace the Allen bolts. Be careful to not pry the backplate off at an angle. That can bend the voice coil inside the tweeter. Instead you should just rotate. If the backplate is stuck it is because of the serial number sticker. Use a razor blade to slice it between the backplate and the magnet. You may need to take the four Philips screws out of the front of the horn and remove it from the black plastic retaining mount entirely in order to gain access to the sticker on the side of the tweeter magnet.
MO75T Horn Wiring
Quick disconnect speaker leads have already been soldered onto the horns for you. Use the included mating connectors and speaker leads to connect to the passive MO75T crossovers. The speaker leads are left long so you may want to trim them down to a length that works well for your particular installation. Find your crossover mounting location before doing so. A good location is behind each small gauge in the fairing (either side of the radio). Route the horn speaker wires in such a way that they do not interfere with the movement of the mid woofer.
Gaskets and Retaining Clips
Remove the rubber gasket and two plastic retaining clips from your factory grills and relocate them onto the new grills. Note: be very careful when removing the plastic clips from the factory grills. Pry both bottom edges of each clip outward at the same time to release the clip without breaking it. In the event you do accidentally break a clip, these clips are very common in automotive interiors and can be found at most any automotive parts store in the clips and fasteners section.
All horn tweeters are much louder than mid range woofers. This is normal and desirable for a Harley sound system. This is one of the tricks we use to get the insane output levels we want. When things are done right it can be stupid loud and also sound great. However you need to be aware of this when tuning your system. It is normal to bring the high frequencies (treble) way down in order to compensate for the dramatic difference in volume levels between horns and all other speakers.
If you are driving the horns from the their own amplifier channels you can simply make the appropriate gain adjustments on the tweeter horn channels of your amplifier. If however you are driving the mid woofers on the same channels as the horn tweeters (very common) the best way to do this is by using an equalizer like the kind all digital sound processors use. All common horn tweeters have a sharp spike around 6khz to 8khz. So start by pulling the EQ levels in this range down.
Advanced Tweeter Tuning Tip (for Pro's)
If you are using a DSP with a parametric EQ (an EQ with a "Q" adjustment) you can select the 6.3khz band and lower the Q adjustment to 1.4 and bring it down about 6db. Lowering the Q value will widen the effect of that EQ band and consequently also bring down other frequencies above and below the 6.3khz center point. Other EQ bands will also need adjustment but you will find that the 6.3khz band will now have the most profound effect on the tweeters sound.
Mid Woofer Tuning Tips
Assuming that you will be using either a set of Diamond Audio MSPRO65 or some other similar pro audio type midrange you will want to crossover (high pass) your speakers at 150hz. You can do this either at the amplifier or at the DSP. Advanced users will want to use the DSP. If using the crossover built into your DSP, you should also high pass the speakers using your amplifiers built in crossover but set that crossover at 100hz so that it doesn't interfere with the DSP crossover. If the amplifier and DSP crossover are too close to each other there can be unexpected effects.
Advanced Mid Woofer Tuning Tip (for pro's)
There are several points of EQ adjustment that you will likely want to make to the frequency range of the mid woofer, but the most important one will be the frequency range where the mid woofer stops working and the tweeter starts working. Mid woofers naturally roll off in efficiency around 2khz and many horn tweeters don't start getting loud until 5khz. This potentially leaves a null between the two speakers. Different bikes and various setups will be more or less effected by this. So experiment with some understanding of what's going on.
Here's what you do about it. Select the 2khz band and lower the Q to 1 (or even .05) and play with gain and cut. You will find that this will dramatically change the upper frequency characteristics of the fairing woofers for better or worst. What's happening here is that you are changing the loudness up or down of the entire upper frequency response of the woofer with a single EQ band. It makes quick work of changing the response of the woofers. The change will be very apparent. It shouldn't take you too long to figure out what is right and sounds good.
Whenever tuning a system with horns it is normal to end up with some hiss (noise floor) at zero or near zero volume. This is because the horns are so efficient that they amplify the small noise floor that exists in all audio systems. You can however minimize this hiss by taking the time to correctly adjust your amplifier gains. Ultimately if you do encounter a level of hiss that you don't find acceptable you will need to make a choice. Do you want to over gain your system for insane volume levels or do you want to back the gains off a little and reduce any hiss that may be present.
When things are done right the noise floor should never be alarmingly loud, but don't expect absolute silence with the engine off and the volume down if you want a system that screams at 100 MPH.