Bass/treble

[juan123]

Hello! I have a stereo which in which i plugged in some small speakers (3"), i'd like to know what kind of capacitor i should get to remove all bass, since it could damage the speakers. I'd like frequencies like 16khz, and up to 400hz to be heard, but anything lower than that, no. Any suggestions? Thanks!!

 

[audioguru]

Hi Juan,
A single capacitor certainly won't remove all bass, and won't prevent damage. It provides only a gradual reduction of low frequencies and nearly full power at the speaker's resonant frequency. Speaker systems frequently use two capacitors and an inductor to make an 18dB/octave crossover circuit which cuts-off the bass with a slope much sharper than just a single capacitor:

 

[Nigel Goodwin]

Have a look at https://colomar.com/Shavano/construction.html, there's a nice section on passive cross-overs. As already suggested, you don't 'remove' the lower frequencies, you only make them weaker.

A LOT depends on what your speakers are?, if they are 'full range' ones you don't need to filter them, but if they are tweeters it's essential (although you can't use just tweeters).

 

[audioguru]

A LOT depends on what your speakers are?, if they are 'full range' ones you don't need to filter them

Juan's speakers are only 3". My clock radio uses a 3" speaker. It would be toast if it got the full bass output of an amplifier. It would also be toast if it got the full output of an amplifier at any frequency. :cry:

1) Where did the speakers come from? Their power rating?
2) How powerful is the amplifier?
3) How much bass boost is used?

I designed the bass boost of my 1W amplifier in my modified clock radio so that it sounds flat down to 100Hz at a low volume control setting. It has a bass power boost of 32 times (20dB)! As the volume control is turned up, the boost decreases so the amplifier never clips. At the max volume control setting the amplifier's response at 100Hz is flat without any bass boost.
It sounds great because 100Hz is boosted to just below clipping at any volume control setting. It also sounds great because the amplifier's output coupling capacitor is big enough for the amplifier to properly damp the speaker's fairly high resonant frequency.

:lol: I can picture the design engineer of a cheap TV blaming the hollow, resonant sound of his TV design on the speaker. He knows that the speaker is small and can't produce bass, so he reduces the value of the amp's output coupling capacitor to reduce very low bass. GOODBYE DAMPING! The cheap little speaker will resonate all over the place! Bongo drums with any voice! Don't most cheap TVs sound like that?
He should use a big output coupling capacitor for good damping and use a highpass filter ahead of the amp. :lol: