bass cut

[danielsmusic]

i need to cut bass completely from a sound signal
is this right?
it doesnt seem to work very well.

 

[Dr.EM]

I think the problem with this is that the rolloff curve might not be sharp enough. You'll want to find a 24db octave one for this. That said, i've never seen the schematic for one, so if anyone finds a good one, that would be great. There is a possibility that a low pass filter will act as a high pass if the filtering element is swapped, ie capacitor changed to inductor.

 

[danielsmusic]

is there anyway how i could cut of the peak i dont know much about music signals

 

[audioguru]

First you need an audio amplifier.
Your transistor is off most of the time and positive peaks of the input signal turn it on like a rectifier, not an amplifier.
Also, C1 charges when the transistor's input conducts, so that the next half-cycle needs even more voltage to make the transistor conduct.

Why not use an LM386 audio amplifier IC?
It will amplify and drive a speaker without much distortion and you will be able to hear the effect of bass-cut circuits. :lol:

 

[danielsmusic]

i know the effects of bass cuts i dont want to wait 3 days for a chip to come, otherwise i would of got a few of op amps. i just need to cut the base from a speaker.
what do i need to do?
the other thing is i dont want to use a chip because im puting alot of watts through it
thanks for the reply.

 

[zevon8]

Like stated above, what you want is a 24 dB cut filter, commonly known as a 4th order filter. There are many designs available on the net, one of the most popular is the 4th-order Linkwitz-Riley design.

Try a search for the terms 4th-order Linkwitz-Riley. You can do this actively or passively, first being somewhat easier, the second you get to wind coils or hope to get a close standard one.

Here are 2 links to start you off:

**broken link removed**

**broken link removed** ( this is for Butterworth filters, not quite as nice as a Linkwitz-Riley, but depending on your goal, probably just fine.

OK, my bad, didn't read your last post completely. If this filter is to be used on a high wattage speaker line, then you get to go the passive method. ( second link ) Start winding coils, big ones.

 

[danielsmusic]

that didnt help ether.
i mite try using push pull transistors when the current is low it does nothing when it goes high it cuts off.

 

[audioguru]

i might try using push pull transistors. When the sound is low it does nothing and when it goes loud it cuts off.

Correct. All audio amps use push-pull transistors, but they are biased correctly so that they work properly.
Your amp circuit doesn't have any bias for its transistor as I explained before.

How can you put "a lot of watts" into a 4 ohm speaker if you are using a supply of only 9V?
If the amplifier was perfect with no loss (impossible) then the signal across the speaker would be 9V p-p, which is 3.18V RMS, which is only 2.5W. Since amplifiers have loss (they heat up) then you would be lucky to get 2W which certainly isn't "a lot of watts".
Ordinary factory car amps use the car's 13.8V battery to power 2 amps for each speaker. The amps are bridged which effectively doubles the voltage across the speaker resulting in 4 times more power. About 14W is provided to each speaker. Of course those amps have push-pull transistors that are biased correctly. :lol:

 

[_3iMaJ]

Thats not a very good circuit. But I'd like to hear more about the application. Assuming you didn't need any sort of amplification, go down to your local audio store and buy some bass blockers, that should be enough. Just make sure they're rated for the type of power you're using.

Assuming of course you don't need amplification.

 

[mstechca]

i need to cut bass completely from a sound signal
is this right?
it doesnt seem to work very well.

You have made a simple common collector amplifier. I think that your circuit could damage something because you have the emitter connected to the speaker and then to -ve. I assume that this speaker is not an electret which means once the emitter is enabled, a SHORT CIRCUIT will occur at the output.

Couple the output as well. Connect a resistor between emitter and ground, then connect the speaker from ground to emitter through a capacitor.

Lowering capacitor values will most likely remove some of the base sound, but it will cut-off the rest of the low sounds. Try something like 1uF and then work up until you are satisfied.

EDIT: It is almost configured as a common collector amplifier. Connect a resistor of about 200K between base and +ve.

 

[audioguru]

It is almost configured as a common collector amplifier. Connect a resistor of about 200K between base and +ve.

If the emitter-follower is biased at half-supply voltage, 1A will flow through the 4 ohm speaker.
A power transistor such as a TIP31 has a minimum current gain of 25 at 1A. Therefore the base current is 40mA but your 200k resistor can supply only 21.5uA, about 2000 times too small. :roll:

 

[Dr.EM]

Hmm, wouldn't it be easiest for him to buy an ordinary passive speaker crossover, then connect his speaker to the tweeter, or if it has it, midrange output? It's only 12db, but it should work ok.

 

[danielsmusic]

i have changed a few things around, is this right.
when i connect the curcuit up without the capacitor and resistor
it works (with bass) and when i hook it up it works just the same.

 

[Nigel Goodwin]

i have changed a few things around, is this right.
when i connect the curcuit up without the capacitor and resistor
it works (with bass) and when i hook it up it works just the same.

Sorry, but your 'circuit' is complete rubbish!.

You also haven't provided enough information to get any accurate answers, for a start we need to know if it's line level or speaker level. You should also be aware that you can't "completely cut the bass", only reduce it.

What EXACTLY are you wanting to do?.

 

[danielsmusic]

updated my last post

 

[Nigel Goodwin]

updated my last post

Sorry, it's still total rubbish!.

Please let us know EXACTLY what you are trying to do?.

 

[danielsmusic]

my speaker is in-line i need to cut bass as much as i can as it is not a bass speaker.
the speaker is right next to the curcuit.

 

[Nigel Goodwin]

my speaker is in-line i need to cut bass as much as i can as it is not a bass speaker.
the speaker is right next to the curcuit.

You still haven't given ANY details!.

Are you trying to feed a speaker from a speaker level output (power amplifier) - if so, all you need is a passive crossover, in fact just the high frequency part of a two way crossover.

 

[danielsmusic]

no im trying to cut as much bass as posible from the line not trying to amplify it

 

[Nigel Goodwin]

no im trying to cut as much bass as posible from the line not trying to amplify it

A passive crossover doesn't amplify ANYTHING (it's passive), a two way one sends the low frequencies to the bass unit, and the mid range and high frequencies to the tweeter (depending on the crossover frequency).

By using just the tweeter half between an amplifier and a speaker, the speaker will not receive much bass - far too little to have any effect.

However, I'm still guessing what you want? - you STILL haven't told us.

I'll try again - TELL US EXACTLY WHAT YOU WANT TO DO! - not how you think you need to do it!, but WHAT YOU WANT TO DO (AND WHY)!.