hey guys i have been doing a research and stuff i have found some low pass filters but nothing that would fit my needs. my needs are that the low pass filter cut off frequency would be at about 200hz and it would be adjustable with a decent quality setup i have is.
sound from pc/phone to an amp to speakers
it would be the best that it would go before an amp all i need is 2 knobs(pots) one for bass volume and one for cut off frequency adjust or it could be fixed 200
please if somebody have or know pcb layout with components please post it here
sound from pc/phone to an amp to speakers
it would be the best that it would go before an amp all i need is 2 knobs(pots) one for bass volume and one for cut off frequency adjust or it could be fixed 200
please if somebody have or know pcb layout with components please post it here
Maybe a lilttle help
9justinas9,
I don't know if I will be able to get back to this thread, but maybe I can help.
It sounds like your terminology may need to be more precise. If you want to hear audio (like intelligible speech) from this amplifier, you might want a 200Hz _high-pass_ filter. The effect of this filter would be to remove bass (like low-frequency noise below the frequency range needed to understand voice). Is that what you need to do? The rest of this paragraph assumes that you want a high-pass filter. You probably want at least a second-order filter. The higher the filter order, the steeper the slope of the frequency response as it transitions from the pass band (above 200 Hz) to the stop band (below 200 Hz.) For analog filters, adjusting the corner frequency of a second-order filter requires that two components be adjusted simultaneously (three for a third-order, and so on).
Perhaps you can implement the filter you want in the digital domain? Like software or an app for your phone?
If you use a 200Hz _low-pass_ filter then what you will get out is only the low-frequency part of the program. The program material below 200 Hz will not be understandable speech by itself. If the subsequent amplifier and speaker are intended to reproduce just the low frequencies, then the associated speaker would be called a woofer or subwoofer, and another system (one that uses a high-pass filter) would be responsible for the higher frequencies. Together, the two systems would cover the audio range. Ideally, the design of the low-pass filter and the high-pass filter would be done together, and ideally taking into account the capabilities of all the speakers used. If you do this, the volume control of the amplifier for the low frequency system's amplifier would act like a bass control, but not a very good one.
I don't know if I can get back to this thread, but I hope this information helps you formulate your problem.
Tom
9justinas9,
I don't know if I will be able to get back to this thread, but maybe I can help.
It sounds like your terminology may need to be more precise. If you want to hear audio (like intelligible speech) from this amplifier, you might want a 200Hz _high-pass_ filter. The effect of this filter would be to remove bass (like low-frequency noise below the frequency range needed to understand voice). Is that what you need to do? The rest of this paragraph assumes that you want a high-pass filter. You probably want at least a second-order filter. The higher the filter order, the steeper the slope of the frequency response as it transitions from the pass band (above 200 Hz) to the stop band (below 200 Hz.) For analog filters, adjusting the corner frequency of a second-order filter requires that two components be adjusted simultaneously (three for a third-order, and so on).
Perhaps you can implement the filter you want in the digital domain? Like software or an app for your phone?
If you use a 200Hz _low-pass_ filter then what you will get out is only the low-frequency part of the program. The program material below 200 Hz will not be understandable speech by itself. If the subsequent amplifier and speaker are intended to reproduce just the low frequencies, then the associated speaker would be called a woofer or subwoofer, and another system (one that uses a high-pass filter) would be responsible for the higher frequencies. Together, the two systems would cover the audio range. Ideally, the design of the low-pass filter and the high-pass filter would be done together, and ideally taking into account the capabilities of all the speakers used. If you do this, the volume control of the amplifier for the low frequency system's amplifier would act like a bass control, but not a very good one.
I don't know if I can get back to this thread, but I hope this information helps you formulate your problem.
Tom
look up Sallen and Key (S&K) filter.
This one opamp filter is 2pole with a slope of 12dB/octave (=40dB/decade)
You could also use an MFB filter (Multiple FeedBack). It too is a 2pole filter but has an extra degree of freedom in that gain is independent of Q
In both types you can change either the frequency setting resistors, or change the frequency setting capacitors.
If you want continuous variability then use a VR (pot wired as a variable resistor) as your control. Switchable using a multi-pole dip switch is probably better, particularly if you want 3pole, or more, of slope.
This one opamp filter is 2pole with a slope of 12dB/octave (=40dB/decade)
You could also use an MFB filter (Multiple FeedBack). It too is a 2pole filter but has an extra degree of freedom in that gain is independent of Q
In both types you can change either the frequency setting resistors, or change the frequency setting capacitors.
If you want continuous variability then use a VR (pot wired as a variable resistor) as your control. Switchable using a multi-pole dip switch is probably better, particularly if you want 3pole, or more, of slope.
I need something like 4pole low pass filter for two 40w 8ohm woofers connected in paralel idk if its good idea but I can't find an appropriate amp for my setup but basicly I will use 2x20w for anything above 200hz with tda 1554q and for subs I will use lm3886t with a low pass filter coz there is times when I don't like sub and there is times when I can't live with out it
I'm not sure about the poles but I have heard that more poles equal more quality so I'm not sure what I want talking about the poles but even in this forum I could not find a decent low pass filter. With things I specified. I would like to adjust the cut off frequency but as AndrewT suggested VR (variable pot) would be enough so basicly I need one pot witch would adjust volume of bass with out messing with the main audio so if has to be done with filter of some sort. But now that i cone to think of it I need high pass filter too with variable cut off frequency. I will get back to this forum as soon as I'm not on my phone
i dont have that much to spend my budged would be 10$ at most and i want a DIY project for various reasons
hi Justin,
I've just built an adjustable low pass filter. Then I did some research on this forum and got lots of help building a fixed low pass filter. I would keep it simple, seeing as you know what speakers will be driving your high pass signal (main speakers) then you have the luxury of just making a fixed filter. The sub woofer circuit have a simple gain control so you can adjust the volume.
Even simpler, if you can work out the approximate roll off of your main speakers then you don't need to use a high pass filter on them, just build a low pass that is the opposite of the natural roll off from the main speakers.
I've just built an adjustable low pass filter. Then I did some research on this forum and got lots of help building a fixed low pass filter. I would keep it simple, seeing as you know what speakers will be driving your high pass signal (main speakers) then you have the luxury of just making a fixed filter. The sub woofer circuit have a simple gain control so you can adjust the volume.
Even simpler, if you can work out the approximate roll off of your main speakers then you don't need to use a high pass filter on them, just build a low pass that is the opposite of the natural roll off from the main speakers.
If you don't add an electrical high pass filter before the satellites, then they will see a full bandwidth signal. Yes, the bass response rolls off. BUT ! the cone excursion due to receiving full strength bass signals will stress the satellite bass/mid driver.
In my view you need to protect the satelite from excessive excursion and this can only be done by adopting a small sealed cabinet, or adding an electrical high pass. Or both.
In my view you need to protect the satelite from excessive excursion and this can only be done by adopting a small sealed cabinet, or adding an electrical high pass. Or both.
The standard method.
Low signal at known frequency from a generator.
Feed through a 1k resistor to the 8ohms speaker.
Plot the Speaker impedance as frequency is varied.
Find the resonant frequency, where speaker impedance is highest and voltage across the 1k is at minimum.
You can also determine Qbox.
Low signal at known frequency from a generator.
Feed through a 1k resistor to the 8ohms speaker.
Plot the Speaker impedance as frequency is varied.
Find the resonant frequency, where speaker impedance is highest and voltage across the 1k is at minimum.
You can also determine Qbox.
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