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Noise Filter on Speaker

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c5trc101

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Hi, Im in need of a noise filter for a speaker, like the founded in icom or kenwood speaker for example, i have looked that bhi has a good speaker system whit this system, but for us in Venezuela, is not affordable to obtain greens, and the most of us, try to make ours cables, interfaces and filters.

Can someone help me to make one to use whit a homemade box and 8Ω speaker ? Tnx in advance and excuse my english ;-)
 

MikeMl

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What are you trying to filter out of the sound that the speaker produces without a filter installed? Is this for ham radio?
 

MikeMl

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c5trc101

New Member
Hi mike,yes, i have looked this commercials speakers, but like i said, for the common people here, are very difficult to obtain currency, and the exchange are very high, for that reason, im looking for resource to make a homemade noise filter for a speaker like these that you show me in the link. how much elaborated? well im not an engineer, but im try to put my best effort
 

MikeMl

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Can you obtain a set of powered computer speakers normally used with a desktop PC.? Hereabouts, these are very cheap at local thrift shops and yard sales; I have seen them sell from as little as $3.

If you can obtain a set of those, they are ideal for hacking. They usually have a stereo amplifier powered with an external wall-wart plug-in power supply, usually 9 to 12Vdc. These are usually good fidelity for music, and as such can be considered as too wide in frequency response for voice-only or CW communication. However, it is simple to add some simple op-amp high-pass and low-pass filter stages at the input of the speaker amp(s) to tailor the frequency response better suited to voice.

You could even install some sound processing software on a PC, temporarily run the audio from your receiver through the sound-card, experiment with filtering it while listening to typical QSOs, and then when you find a set of filters you like, convert them to a set of analog filters to be used with the computer speakers I mentioned above.

Before we had PCs, I have done something like this using a Hi-Fi stereo amplifer equipped with a multi-band Graphic Equalizer. I could set the equalizer bands to get the filtering of the audio that improved intelligibility.
 
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c5trc101

New Member
Hi, yes i have a pair of these pc speaker, (1 genius and 1 silver-point 2.1), have used one time trying to equalize the sound of the radio (kenwood ts400sat) via pc using its eq, and one time using tone control of the speaker, but its not the same result when its used the filters on kenwood or icom speaker, for this reason i m looking for a circuit to make, in fact i have done a board whit a tda2030a, thinking on use whit these type of filter, the only that wait me its the form of calculate de band pass, honestly i havent understand some of publication founded in the web
 

MikeMl

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Most Helpful Member
Do you have specs and/or a schematic of what Kenwood or Icom puts in their external speakers? We might be able to reverse-engineer it. We need to know what you want to build before we start building...

If the equalizer built-in to the sound-card on your PC is not enough, there is some free-download audio processor software that might let you try more aggressive filters than the simplistic ones in the sound-card equalizer. Maybe someone reading this can suggest one?

I have some analog op-amp filter design software that can come up with low-pass, high-pass, band-pass, and band-reject filters of up to several orders, but I can't guess what would turn your high-fi speaker into one optimized for voice communications.
 

c5trc101

New Member
Hi Mike, sorry for delay, no i havent specs whats speakers have inside, i have only listened once and the filters works, but nothing like bhi of course.

I think there will be a lot of software that do these work via pc, but i want to try built it

The problem not is my skills in built the circuit, its to understand how to calculate the filters, like you have said me, high, low, bandpass; i have reading some articles, but not are very clear the formulas.

im know that i havent the same skills or studies like an engineer or a person that studied electronics, but i wish to try to do my own filters
 

MikeMl

Well-Known Member
Most Helpful Member
The reason I suggested using the software was to try different filters until you discover what type of filtering improves the intelligibility of the voice from the ham rig, and then build opamp filters only after you know what you want to build...

I have analog filter designs, but I dont have specs...
 
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MikeMl

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