Is my subsonic filter not working?

[loudfivepoint0 10+ year member]

I've been testing my amp with 20, 25, and 30hz tones. While the tones are playing i turn the subsonic filter on/off and notice a huge difference in the output but the tone IS still coming out. Does this mean my subsonic filter isnt working properly or does a subsonic filter not COMPLETELY block the frequencies from getting out? I'm curious because i have a box that will be ported to 37hz and am contemplating on if i should get another amp with an adjustable subsonic filter. My amp is a RF 1001bd (its the model that puts out 1000wrms@2ohms). Help?

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[Acidburn 5,000+ posts]

filters don't just cut off the tone, they roll off, at different slopes that is, a 6 dB/octave slope is much shallower than a 48 dB/octave slope so if you have a fairly shallow slope then the filter is doing its job

as you go down in frequency it should be getting quiter and quiter because of the slope

 

[squeak9798 5,000+ posts]

Subsonic filters and crossovers don't just kill the frequencies below or above the SSF/crossover point (a subsonic filter is nothing more than a highpass crossover with really low crossover points).

What SSF and crossovers do is attenuate the frequencies above/below the crossover point at a given slope (the slope should be stated somewhere in the owner's manual).

For example, if your SSF has a slope of 24db/octave, then it attenuates the frequencies below the selected frequency at 24 decibels per octave. If it has a 12db/octave slope, then it attenuates the frequencies below the selected frequency at 12 decibels per octave.

EDIT: **** boys, we all three posted at the same time.....good work //content.invisioncic.com/y282845/emoticons/handclap.gif.0c301076f534e244f0460706894f19e0.gif

//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Acidburn 5,000+ posts]

HA! i win! i beat both of you

 

[squeak9798 5,000+ posts]

But mine was the longest //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[Acidburn 5,000+ posts]

But mine was the longest //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

hahahahahaha but i got done first which in this case actaully is a good thing

 

[btnhfan 5,000+ posts]

but with that amp (i have the same one) there is a switch for ssf on or off. would it be better to get a seperate ssf? there is no way to adjust it. its simply on or off.

 

[squeak9798 5,000+ posts]

but with that amp (i have the same one) there is a switch for ssf on or off. would it be better to get a seperate ssf? there is no way to adjust it. its simply on or off.

It depends on what frequency the SSF is set at. Again, should say in the owners manual. RF isn't stupid, I'm sure they picked a logical frequency.

Would it be better to have an adjustable; possibly, depends on what frequency you need it to be set at, which makes it more install dependent than anything.

But more than likely the pre-set frequency will probably be fine in most situations.

 

[Acidburn 5,000+ posts]

in a separate cross-over, you might be able to adjust frequency AND slope

 

[loudfivepoint0 10+ year member]

I checked the owner's manual and it has nothing but a chart for the subsonic filter. I THINK the subsonic filter is pre-set at 20hz. There is a curving line with numbers along the left vertical axis from -12 to +3 then along the bottom is frequencies BEGINNING with 20 hz all the way to 2khz. The line begins at 0 along the vertical axis which is also 20hz. So i believe its set to 20hz. Would that be dangerous to run if your box was tuned to 37hz?

 

[Acidburn 5,000+ posts]

where does the line start to roll off?

 

[ANeonRider 10+ year member]

The SSF is set to whatever frequency the line flattens out at.