[SOLVED] Audio Speakers connection scheme

[amirke]

Hi,

I have 2 basic questions regarding to speakers connection to an amplifier:
1) Can I connect a 25W amplifier to a 4W speaker ? (actually, I did. I want to know what are the consequences and maybe a thumb rule)
2) Can I connect 2 speakers in parallel to 1 amplifier ? (same case, each speaker is 4W and the amplifier is 25W)

Thanks all

 

[FvM]

1. The speaker can be damaged if you fully turn up the amplifier. If you are keeping a moderate volume, this is unlikely to happen.

2. We have to ask for amplifier and speaker impedances. The total speaker impedance must not be less than the minimal amplifier load impedance (usually 4 ohms, sometimes 8 ohms). Speaker series connection would be safe for the amplifier, but may reduce the sound quality if both speakers are different type.

 

[amirke]

2. We have to ask for amplifier and speaker impedances.

Speaker impedance is 4E.
if we connect it in parallel then it means that the overall impedance of the speakers is 2E ?
and if the amplifier impedance is 6E, what can it damage ?

What is the proper way to connect multi speakers ? 1 amplifier for all speakers or each speaker with its own amplifier (i am not talking about stereo. same output for all speakers)

Thanks

 

[kam1787]

Speaker impedance is 4E.
if we connect it in parallel then it means that the overall impedance of the speakers is 2E ?
and if the amplifier impedance is 6E, what can it damage ?

it could damage your amplifier

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What is the proper way to connect multi speakers ? 1 amplifier for all speakers

such that the impedance of speaker network falls into the acceptable range of the amplifier, given, of course that the load is shared equally by the speakers.

 

[Audioguru]

An amplifier DOES NOT have an output impedance of 6 ohms. Instead its minimum load rating is 6 ohms.
The amplifier output impedance is extremely low, 0.04 ohms or less so it can damp the resonances of a speaker. Lookup "damping factor" in Google.
Then if the speaker impedance for this amplifier is less than 6 ohms, the peak current rating is exceeded when the output power is high and the amplifier might blow up.

 

[amirke]

Then if the speaker impedance for this amplifier is less than 6 ohms, the peak current rating is exceeded when the output power is high and the amplifier might blow up.

Well, the filter in the output of the amplifier determines what value of load it should face with, correct ?
If I designed the filter (LC, as the manufacturer recommended) to a 4E load, then no danger that the amplifier might "blow up" ?

PS, no Damp Factor value on my amplifier datasheet (tda7492P)
https://www.st.com/web/en/resource/technical/document/datasheet/CD00211320.pdf

thanks

 

[Audioguru]

Well, the filter in the output of the amplifier determines what value of load it should face with, correct?

The opposite. The value of the parts of the 27kHz filter are determined by the speaker impedance.

If I designed the filter (LC, as the manufacturer recommended) to a 4E load, then no danger that the amplifier might "blow up"?

Its graphs show that is begins to clip at an output of about 12W into 8 ohms with a 20V supply or into 6 ohms with an 18V supply.
There are no spec's or graphs for a 4 ohm speaker.

PS, no Damp Factor value on my amplifier datasheet (tda7492P)

It is a switching amplifier without spec's for its damping factor.

 

[amirke]

There are no spec's or graphs for a 4 ohm speaker.

Yes, but yo can see in page 21 an example for connecting it to a 4E speaker.

What does it means "that is begins to clip at an output of about 12W into 8 ohms with a 20V supply or into 6 ohms with an 18V supply" ?
That if I will produce from the amplifier signal above 12W with a 8E speaker then the sound will be clipped ? damaged ?

About damping factor - with D class amplifier (switching) - it is not relevant ?
why

 

[Audioguru]

Clipping at the output of an amplifier is when the signal voltage goes as high or as low as it can but the signal wants to go more. It causes distortion because the output signal is beginning to look like and sound like a square wave. It is shown on the distortion graph when the distortion suddenly begins rising steeply when the input level is increased a little. The amplifier has some of its power output ratings when the distortion caused by clipping is at a horrible-sounding 10% distortion.
It begins clipping at half the rated power like this:

If an amplifier has a low damping factor then a modern speaker sounds awful like a bongo drum. Some guitar players like that kind of distortion.

 

[amirke]

I don't understand 2 thing:
1) When the amplifier might "blow up" ? when the filter value is incorrect ?
2) No Damping Factor value on datasheet.

 

[Audioguru]

I don't understand 2 things:
1) When the amplifier might "blow up" ? when the filter value is incorrect ?

No. The amplifier might blow up when the output level is high and its speaker impedance is too low causing its output current to be too high (Ohm's Law).
The filter prevents the 310kHz and its harmonics from radiating into the air and causing radio and TV interference (EMI listed in its datasheet).
The values of the parts of the filter are affected by the speaker impedance.

2) No Damping Factor value on datasheet.

The datasheet for a modern amplifier should list its damping factor.

 

[amirke]

Thanks Audioguru for helping me.

Cheers