setting ssf/lpf sub amp

BassMunky · December 18, 2011

so my box is tuned to 35 hz do i set my ssf to 30 or 25hz? and set the lpf to 80hz right?

now how do i know it at that exact setting?

can i use this method with the car off or has to be on?

Setting Subsonic Filter (SSF)

Subsonic filter reduces the amplitude of certain frequencies depending on where it's set.

If your using a sealed enclosure, then turn the ssf all the way counter-clockwise.

So your enclosure is ported? Your going to set the ssf to the frequency your box is tuned to.

Let's use 30hz as an example...

disconnect speakers

turn ssf counter-clockwise until it's considered "off"

play 30hz tone at volume 10.

Measure the voltage output

Let y = voltage output * 0.707

turn ssf clockwise until voltage output now matches "y"

Now your ssf is set.

what would my voltage output be that i use?

Setting Low Pass Filter (LPF)

LPF does the exact same thing as the ssf but it's reducing higher frequencies that we don't want our speakers to play.

Depending on the speaker your using and it's frequency response you'll want to set the lfp filter higher or lower then others.

For this article were going to be setting it to 80hz for a subwoofer.

disconnect speakers

turn lpf clockwise until it's considered "max"

play 80hz tone at volume 10.

Measure the voltage output

Let y = voltage output / 0.707>

turn lpf counter-clockwise until voltage output now matches "y"

Now your lpf is set

MIKE-2U · December 20, 2011

Should be a sticky

BassMunky · December 25, 2011

please make a sticky.

I found out how to set it

Subsonic filter is to roll off the low frequencies under the resonant frequency of your subwoofer if you are using a ported design because under the port tuned frequency the woofer excursion is no longer controlled and will bottom out very easily. This does not have happen if you have a sealed box as the woofer excursion is always controlled by the air in the box. For your sub, 30Hz would be about right but other forum members may have other responses. As for th 80 Hz LPF, it depends on how much bass your mids can take. If you have really good mids you can set the LPF 60Hz or so, and then the High Pass Filter for the Mids also at 60Hz. Thats where I set mine. Experiment with yours. The extra bass comming from up front is awesome. I do have very high end mids and 300watts a side however. the "turn counterclockwise until voltage is .707 x max voltage" is setting the -3db point since power is voltage^2, .707 x.707 =0.5 or half power, the -3db point. (.707 = 1/square root of 2) So for the LPF example, the procedure sets the -3dB point at 80 Hz. This would be more accurate than looking at the frequency dial on the knob. you need to have an AC RMS voltmeter. Most DVMs read AC volts RMS.

BassMunky · December 25, 2011

sticky please and i think this a fast easy accurate way.

Great! So to set the lpf at 80hz play a 80hz tone at a moderate listening level. Does not have to be loud. Set the lpf knob fully clockwise to its maximum frequency setting. Meaure the ac voltage at the sub speaker or amp terminals. Record the voltage. Multiply ththis voltage by .707. Write down the result. Then turn the lpf knob counterclockwise untill the dmm reads this voltage.

For the ssf. Do the same except use a 30hz tone and start with the controll at minimum frequency. Record the voltage, multiply by .707 and turn the knob to a higher frequency untill the dmm reads the new level

(I don't know if it is clockwise or ccw)

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