![]() These tools are not necessary for the hobbyist.InPhase amplifiers are made to rock your world. These tools are great if you're a professional who installs several amplifiers a week. There are many tools on the market that take some of the mathematical work out of tuning your car stereo. Reconnect the subwoofer, testing for proper operation.Turn the amplifier's subsonic filter until the voltage reads your target -3db voltage.Start playing a test tone whose frequency is equal to the subsonic filter setting, 24hz.Turn the amplifier's low pass filter down until the voltage reads your target -3db voltage.Probe the outputs of the amplifier with your digital multimeter, set to AC Volts.Start playing a test tone whose frequency is equal to the desired low pass filter setting, say 80hz.Set the amplifier's subsonic filter to its lowest setting.Set the amplifier's low pass filter to its highest setting.Disconnect the subwoofer leads from the amplifier.Step 4: Set The Filtersįirst thing's first: make sure you've set the amplifier gains properly. Use this measured voltage to determine your -3db target voltage. If you measure 63v, then it's 1000w into four ohms. If you measure 20v, then you know it's 100w into 4ohms. Then make a note of the voltage at the amplifier's output. ![]() Disconnect the subwoofer from the amplifier's outputs and play a 40hz tone track. You'll need to compute the voltage after setting the gain. There are means of setting your gains with distortion detecting tools. ![]() The above assumes you determined 100 watts. To get -3db, we need to compute volts at half the power for the same resistance. Ohms law: Volts = square root of Watts * Resistance After that, we will need to compute the target voltage at -3db. This will make it easy to compute our target voltage.įirst, we have to compute the voltage at 0db. To keep the math simple, we're going to use a 100-watt amplifier into a four-ohm load. This will protect our woofer from unloading at low frequencies. ![]() If we tuned our ported enclosure to 31hz, one octave below that is roughly 16hz. With the subsonic filter, we have a good "rule of thumb": half an octave below port tuning. So we want to set the crossover on the subwoofer to 80hz to start. We'll assume the front speaker installation uses 6.5" drivers, which should play down to 80hz. Since this is a teaching exercise, we'll make some assumptions. We need to make adjustments to the filter to let the midbass speakers shine. There aren't hard and fast rules on low pass filtering for our subwoofer. One could push this lower if the installation has large midbass drivers upfront. Some installations will sound fine with a low pass filter at 100hz. We can't set up "hard and fast" rules with our subwoofer installations. Step 2: Determine Frequenciesĭetermining filtering frequencies is part art and part science. You can make your own tone CD from MP3s or you can order one from Amazon. If you're connecting your amplifier to an older deck with a CD player, you should use a test tone CD. I know they exist on Amazon music and Youtube music, at least. Most of the music services have "tone packs" and "set up tracks" available to play. Modern car audio systems have Bluetooth and it is fine to use your mobile phone as a source in that case. You will need a digital multimeter and a source with tones. This means that, at no cost to you, this website earns a commission if you click through and make a purchase. Pros have used this method for 40 years to produce consistent results.įull disclosure: some of the links below are affiliate links. You'll need a digital multimeter and a tone pack. We're going to explain how to use two basic and inexpensive tools to set your filters like a pro. These filters are likely found on the amplifier. We can do these tasks with some simple filters. You don't want your subwoofer bottoming out from playing too low. You don't want vocals and guitars coming from your subwoofer driver. Do you want the best performance from your subwoofer? You'll need to filter out sounds it was never intended to reproduce.
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