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Alembic Club » Owning an Alembic » Troubleshooting » Archive through November 30, 2011 » SF2 using low pass/high pass filters to protect my speakers? « Previous Next »

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Username: sailorofcheese

Post Number: 14
Registered: 1-2011
Posted on Friday, April 29, 2011 - 2:06 pm:   Edit Post

I'm curious about the use of the filters on the SF2. I have some Acme B2 cabs and would like to take care of. Would this work? --> using the HIGH pass filter to filter out the low end frequencies and the low pass filter filter out the really high frequencies that would be damaging to my speakers

I'm thinking this would make a safe frequency range for me to play in.

is this essentially what a compressor does?
Senior Member
Username: edwin

Post Number: 909
Registered: 5-2002
Posted on Friday, April 29, 2011 - 3:59 pm:   Edit Post

Not exactly. A compressor works in the realm of amplitude (ie. how loud things get) and an equalizer, which includes the SF-2, works in the domain of frequency response. Both can protect the speaker, but where the EQ filters out the potentially damaging frequencies and allows the rest through, it shouldn't affect the amount of level hitting the speakers. If the problem is that you are sending too many ultra lows to the speaker, the SF2 could work as you suggest. If the problem is spikes all over the frequency range, then a compressor (actually, a limiter, which is a subset of compressors, which has a high ratio, meaning that it lets very little signal through over the threshold) would work better. I don't think you have to worry too much about the tweeter, unless you are just sending a ton of power to the cabinet, in which case, again the limiter is your answer.

I have B2 cabinet and the only time I ran into trouble was when I used an envelope filter in conjunction with an octaver.

I hope this wasn't too confusing.
Username: sailorofcheese

Post Number: 15
Registered: 1-2011
Posted on Friday, April 29, 2011 - 5:17 pm:   Edit Post

no, not confusing at all. thankyou! I've been using the SF2 as my EQ and was considering picking up a DBX 160a for a compressor/limiter but was reading up that high pass filters are often used to filter out the frequency spikes lower than 32Hz n was hoping problems would be solved...

thanks for the feedback
Senior Member
Username: bigredbass

Post Number: 1686
Registered: 9-2002
Posted on Friday, April 29, 2011 - 10:22 pm:   Edit Post

I would not worry much about harming an Acme B2.

Andy quotes a frequency response of 41hz to 22khz, +/- 3 db. The fundamental of a low B string is 31 hz, less than half an octave below 41hz. And 22k is a towering high end for a 'bass cabinet'. Unless you're getting a lot of handling noise, the instrument is not generating anything lower than that playing-wise so you should be fine. The only other way to get lower than that would be to be tuned below low B or be using one of those octave-lower harmonizers . . . .

Edwin was right to point out that you could essentially dictate your signal frequency bandwidth with the SuperFilter, but signal strength (which ultimately drives the output of your amp to the Acmes) is best controlled by a limiter or compressor, of which a 160A is a fine mono dbx unit. This is where you can run into trouble: Amps driven into distortion can generate signals which can harm speakers. And here I mean, you're pushing barely enough amp for the job to the wall, and the power end is distorting, not a preamp distortion for effect. Usually though, very loud, clean outputs are not a problem within reason: Obviously, you wouldn't hook up a 2000watt Crest to a 5" speaker. But generally, more clean power than rated speaker-wise is not harmful in smaller doses.

Lots of guys here use Acmes, and they are in general tough little beasts routinely fed by 500 watt (or more) amps. The designer really did his homework and these are functionally way past your typical bass guitar cabinet.

So, if you're using a good preamp/power amp rig or a good head in the 300 to 600 watt range and hear no obvious problems, you're fine. I just wouldn't worry about breaking an Acme if you're doing things right.

J o e y
Username: sailorofcheese

Post Number: 16
Registered: 1-2011
Posted on Monday, May 02, 2011 - 2:53 pm:   Edit Post

thanks for your help, Joey. Just wanted to make sure i was doing things right.

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