How do I make a speaker crossover to only hear range of human voice?

[yeto]

Would it be possible to add to the below circuit so that I could not only filter out the highs but also 60 cycle hum? I only want to hear audio in the range of a human's voice.

Speaker Noise Reduction Circuit Add on VE3VDC

Thank you in advance for any help,
yeto

 

[turk 182]

"google" band pass filter circuits

 

[Jonathan Bright]

Hi yeto, The circuit you mentioned is not really optimum for human voice. Also it won't address the 60c/s hum issue.
turk 182 is right.
Generally the voice range is understood to be the band of 300c/s to 3,000c/s so depending on your speaker you can put in high and low pass filters. The easiest is of course first order which means one capacitor and one inductor (coil). But from a cost-effectivness point of view second order would probably be best.
Look up the appropriate values in easy to find cross-over tables. Note that the values change depending on your speaker impedance.

I am guessing that you are new to this area. If so, you might find 10-15 min reading about speaker cross-overs will be productive.
But what you are seeking is quite reasonable and well within the average diyer's skill set.
Hope this is useful.
Cheers, Jonathan

 

[rayma]

Would it be possible to add to the below circuit so that I could not only filter out the highs
but also 60 cycle hum? I only want to hear audio in the range of a human's voice.

This could be done much better with an active circuit before the power amplifier.

 

[Jonathan Bright]

"yes" and "no" rayma. I like active filters but it may not solve the hum issue if that is power amp related.
Cheers Jonathan

 

[sreten]

Hi,

Just add a series capacitor to the circuit to get rid of bass.

rgds, sreten.

 

[JMFahey]

Would it be possible to add to the below circuit so that I could not only filter out the highs but also 60 cycle hum? I only want to hear audio in the range of a human's voice.

Speaker Noise Reduction Circuit Add on VE3VDC

Thank you in advance for any help,
yeto

Let's clear a couple things first, for a better answer.

1) are you a Ham? Is this filter meant to be used with some kind of Ham receiver/SWL/portable Communications?

2) if so, the one shown is very crude, just not to call it useless.
Its poor slope (again an understatement) means it either can not filter noise out, or kills audio intelligibility or both.

As suggested above, you should need a strong voice intelligibility band bandpass filter, which given the 10:1 ratio (3kHz to 300 Hz) is best accomplished by a 300Hz highpass followed by a 3 kHz lowpass; both *at least* 12dB/octave.

In fact doubling that to 24dB octave would be way better.

This can easily and inexpensively accomplished by active filtering, a couple cheap Op Amps and a few extra parts can do, but you need some way to insert it before the power amp.

If your receiver is a closed box and you have no access to its electronics, then some passive filter may be inserted between power amp and speaker, but I guess weight/size/cost/complexity will make it prohibitive.

Besides it, a tunable notch filter or a Parametric Equalizer is often used in Communications situations to tune out annoying heterodyne squeals.

 

[esgigt]

Generally the voice range is understood to be the band of 300c/s to 3,000c/s

Sorry Jonathan, but that's the definition for telephony (limited speech).... The human voice is quite a bit broader than that, especially into the bass area. Some male singers are known for reaching as low as 20 to 30 Hz.... So in general a minimum frequency in the range of 50 Hz will cover most cases.

And the highs? That's a bit harder to describe. The first harmonics usually do not go over 2 or 3 kHz.. rather hard to produce such a tone... So at least 5kHz for the highs I'd guess..


Greetz,
Edwin

 

[Ian Finch]

The OP though, posted a noise reduction scheme for Amateur Radio use and ridding 60Hz hum - Not much work for Basso Profundos there

 

[esgigt]

The OP though, posted a noise reduction scheme for Amateur Radio use and ridding 60Hz hum - Not much work for Basso Profundos there

In which case one can revert to a more PA approach... approx. 100Hz to 3,5kHz... Sounds better than the telephone bandwidth.

 

[davidsrsb]

5kHz at the top end makes female voice more natural. The telephony 3.3kHz value was chosen to allow economical 8ksps sampling and match the bandwidth of old long haul phone lines with loading coils

 

[mt490]

Listen using RTL-SDR and a 10 buck dongle on the PC and run the stream though a vocoder.

 

[gmphadte]

You will hear other sounds that fall in that frequency range. Hope you are not thinking only human voice will be heard.

Gajanan Phadte

 

[yeto]

I searched as suggested and found the following circuit but I don't know what values to use. I searched for a table but all I could find were tables using inductors versus capacitors. I can't get to the electronics so an active circuit is not be an option. This is for a speaker phone. Any little improvement will be helpful. Sometimes when people call they have their phone on speaker phone and they sound like they are "under water". Also, if they are in a noisy environment there is a lot of additional noise. If I could remove any of this additional noise it would be helpful.

http://www.allaboutcircuits.com/textbook/alternating-current/chpt-8/band-pass-filters/#22031.png

Would anyone be able to suggest some values to start with? It has an 8 ohm speaker. For the high filter should I start with the values that were suggested for the ham radio? (resistor = 10 ohms - capacitor = 4.7uf)

Thank you for your help,
yeto

Band-pass Filters : Filters - Electronics Textbook

 

[Mooly]

This little circuit was designed to greatly improve speech intelligibility. Look how steep the response curve is.

http://www.diyaudio.com/forums/soli...mpaired-setup-new-television.html#post2419559

 

[turk 182]

that's a whole different ballgame removing background noise and eliminating modulation and phase effects from a phone conversation is the bane of the medium for designers and something that a passive circuit won't fix.

 

[Zero D]

Sometimes when people call they have their phone on speaker phone and they sound like they are "under water".

I know what you mean Well, just ask them to come off SP, i do Sometimes it's because they, and/or you, are in a weak RF area = relocate if possible and call back afterwards.

The problem is at their end, so i apart from the above, i don't think you will be able to improve it ! No harm in trying though, & if you manage it please post back & let us know