speaker connection 8 ohm

Thread Starter

giovanni.dista

Joined Apr 14, 2021
45
Hello everyone, I would like to connect an 8 ohm impedance speaker to my audio circuit, the signal is centered on 2.5 volt and has a nice dynamics, so I would say that I don't need amplification. I'm interested in the voice signal, how should I connect the speaker? the output is that of a third order passive filter. In the picture
 

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MrChips

Joined Oct 2, 2009
23,516
You cannot use that circuit to connect to an 8Ω speaker.
The speaker looks like a dead short across C6 because of the mismatch of the impedances.

You would need a buffer amplifier between R13 and the speaker. The amplifier should have a very low output impedance, lower than that of the speaker.

In general, the impedance of the driver driving a load must be lower than the impedance of the load.
 

crutschow

Joined Mar 14, 2008
27,190
If the low frequency filter output voltage is 2.5V with no load, the impedance of that filter will give only about 3mV of signal or about 1.1µW of power to the speaker when connected.

You need to learn Ohm's law.
 

Thread Starter

giovanni.dista

Joined Apr 14, 2021
45
thanks for your answers !!! what if I wanted to use a preamplified speaker instead? should i make some changes?
To audioguru:
i need vocal band only ( 300 Hz , 3400 Hz)
 

Audioguru again

Joined Oct 21, 2019
3,173
To audioguru:
i need vocal band only ( 300 Hz , 3400 Hz)
300Hz to 3.4kHz are vowels spoken by a female. Speech has a lot more sounds than only vowels.
Speech is from about 80Hz for adult males to 14kHz for consonants like ss, th, sh, t, p, k and other important sounds in speech.
Your 300Hz to 3.4kHz is for an old telephone when the most common phrase spoken is "What? What did you say?".

AM radio stations today boost frequencies from 1kHz to 5khz to sound less muffled. They are not allowed to produce 10kHz (radio frequencies spacing) so they begin cutting 5kHz.

You do not show a bandpass filter. It has no effect on rumbling, earthquake and other very low sound frequencies.
 

BobaMosfet

Joined Jul 1, 2009
1,768
Hello everyone, I would like to connect an 8 ohm impedance speaker to my audio circuit, the signal is centered on 2.5 volt and has a nice dynamics, so I would say that I don't need amplification. I'm interested in the voice signal, how should I connect the speaker? the output is that of a third order passive filter. In the picture
@giovanni.dista By your question, and your schematic, you are using the word impedance, but you don't understand it. In short impedance is the resistance to the flow of current by field effect (reactive). 8 Ohms is very, very little resistance, so (as another person stated), that looks practically like a short to a power-supply. The reason is simple- the speaker is an inductor- a coil around a magnet- that is why the speaker is heavy. As such, it requires a lot of current to make that coil jump and bounce instantly.
 
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