13
Adding Subwoofers and Electronic Crossovers
The best way to combine a subwoofer with your Boston Rally Series
speaker system is with an electronic crossover. Level matching (making
the subwoofer play at the same level as the coaxial system) and precise
frequency division are much easier to get right with an electronic
crossover. Additionally, electronic crossovers have no insertion loss, and
they isolate the coaxial speakers from the subwoofer’s back EMF.
Subwoofer Crossover Frequency Recommendations
It is hard to predict the ideal crossover frequency to use between sub-
woofers and the Boston Rally Series RX47, RX57, RX57DIN, RX67,
RX67DIN, RX87 or RX97 coaxial speakers. Factors such as the interior
dimensions of the car, the type of subwoofers and the installation
method all play a role in determining the required crossover frequency.
We recommend using an electronic crossover flexible enough to easily
change crossover frequencies. Ideally, the subwoofer crossover fre-
quency and level should be independent from the high-pass section(s).
Only through experimentation can the optimum crossover fre-
quency be determined. However, you can use the following guide as a
starting point. Start with a crossover frequency of 100Hz for the RX47,
90Hz for the RX57/RX57DIN, 80Hz for the RX67/RX67DINor RX87 and
70Hz for the RX97.
Experiment with the crossover frequency to achieve a natural,
balanced sound. Keep in mind that an electrical gap in crossover
frequencies is often necessary to achieve a flat acoustical response.
Depending on the installation location, it may become necessary to
invert the phase of the coaxial speakers relative to the subwoofers.
Even though they may be electrically correct, they may be acoustically
incorrect.