Audio PA & analog switching

[Bernard]

I have an audio PA which rated at 4ohms 22W in bridge tied load or
2ohms in stereo mode. What will possibly happen to the audio PA when I
connects a 3.2ohms speaker parallel with 16ohms speaker in bridge
configuration?

Which in my own understand that the resultant impedance is 2.7ohms can
eventually burn the pa. Am i right?

I am also looking for an analog cmos switch which I able to
enable/disable the 16ohms speaker. The switch must able withstand max
1A and 14V peak value and Ron must be ultra low <1ohms. Has anybody
come across this component? Please tell me.

Thank you in advance.

 

[Stefan Heinzmann]

Bernard wrote:

I have an audio PA which rated at 4ohms 22W in bridge tied load or
2ohms in stereo mode. What will possibly happen to the audio PA when I
connects a 3.2ohms speaker parallel with 16ohms speaker in bridge
configuration?

Which in my own understand that the resultant impedance is 2.7ohms can
eventually burn the pa. Am i right?

Possibilities are higher distortion (this might endanger the tweeters)
and increased power dissipation in the amplifier. If the amplifier is
designed badly it may blow up. But then it probably isn't a great pity ;-)

With an arrangement like this you can't set the volume on the two
speakers separately. Because they're different, they may produce very
different sound levels when driven with the same signal. Whether that
matters or not depends on your situation, but I imagine it could be very
inconvenient.

I am also looking for an analog cmos switch which I able to
enable/disable the 16ohms speaker. The switch must able withstand max
1A and 14V peak value and Ron must be ultra low <1ohms. Has anybody
come across this component? Please tell me.

A CMOS switch is not a particularly good idea for this task. Why can't
it be a good old electromechanical relay?

--
Cheers
Stefan

 

[Jan Panteltje]

On a sunny day (3 Jun 2004 03:20:06 -0700) it happened hcyber79@yahoo.com
(Bernard) wrote in <f6006266.0406030220.41133759@posting.google.com>:

I have an audio PA which rated at 4ohms 22W in bridge tied load or
2ohms in stereo mode. What will possibly happen to the audio PA when I
connects a 3.2ohms speaker parallel with 16ohms speaker in bridge
configuration?

Which in my own understand that the resultant impedance is 2.7ohms can
eventually burn the pa. Am i right?
If the PA has some overload protection, you will get only distorted sound.

Else it will go kaput.

I am also looking for an analog cmos switch which I able to
enable/disable the 16ohms speaker. The switch must able withstand max
1A and 14V peak value and Ron must be ultra low <1ohms. Has anybody
come across this component? Please tell me.
No, and likely it does not exists.

Use a relay!

Or, for the same price, a second amp (chip).
JP

Thank you in advance.

 

[Watson A.Name \"Watt Sun]

Bernard wrote:

I have an audio PA which rated at 4ohms 22W in bridge tied load or
2ohms in stereo mode. What will possibly happen to the audio PA when I
connects a 3.2ohms speaker parallel with 16ohms speaker in bridge
configuration?

Which in my own understand that the resultant impedance is 2.7ohms can
eventually burn the pa. Am i right?

Maybe.

I am also looking for an analog cmos switch which I able to
enable/disable the 16ohms speaker. The switch must able withstand max
1A and 14V peak value and Ron must be ultra low <1ohms. Has anybody
come across this component? Please tell me.

Yeah, it's called a Relay.

> Thank you in advance.

 

[Guy Macon]

Bernard wrote:

I have an audio PA which rated at 4ohms 22W in bridge tied load or
2ohms in stereo mode. What will possibly happen to the audio PA when I
connects a 3.2ohms speaker parallel with 16ohms speaker in bridge
configuration?

Which in my own understand that the resultant impedance is 2.7ohms can
eventually burn the pa. Am i right?

It might survive. Maybe the designer wrote 4 Ohms minimum in the
spec when it can actually handle 2.6 Ohms. Or maybe not.

I can say this with confidence; the 3.2 Ohm speaker will be blaring
and the 16 Ohm speaker will put out very low volume, and this will
remain true no matter what amplifier you use.

Add a 16W or larger 4 Ohm resistor in series with the 3.2 Ohm speaker
and the volume levels will be reasonably close to each other and your
amp will be within it's rated limits.

--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
have an "impossible" engineering project that only someone like
Doc Brown can solve? My resume is at http://www.guymacon.com/