For the experts out there ..

 

Bronze Member
Username: Vin

Post Number: 11
Registered: Jun-04
Two interesting questions that you guys may be able to help me out with:

1) If I am running an 8-ohm speaker off a 4-ohm 50W(RMS) output channel of an amp, then what RMS power will the speaker actually put out ? How does the impedance load imbalance affect the sound provided by the speaker ? Is this perfectly safe for the speaker and amp ? Would the sound from the speaker be better or worse (or neither) if the speaker were driven by an equivalent 8-ohm 50W(RMS) amp output ? The reason I'm asking is that I'm planning to use a car amp indoors, and hook up 8-ohm bookshelf speakers to it .. for my home theatre system.

2) Using a 2-channel 4-ohm amp, what happens if I connect the positives and negatives of the 2 output channels to form a single output channel for a speaker (and provide exactly the same sound signal to the amp for input for each channel) ? What effect does this have on current & power & impedence .. etc .. for the speaker and the amp ?

Thank You
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 3744
Registered: Dec-03
that's a crapload more than two questions.

"If I am running an 8-ohm speaker off a 4-ohm 50W(RMS) output channel of an amp, then what RMS power will the speaker actually put out?"

25 watts at full output

"How does the impedance affect the sound provided by the speaker?"

higher impedance means less power means lower SPL.
it also means more headroom for the amp, lower distortion, better damping and S/N ratio, and quite a few other things.

"Is this perfectly safe for the speaker and amp?"

as long as the amp is stable at 8 ohms, yes.

"Would the sound from the speaker be better or worse (or neither) if the speaker were driven by an equivalent 8-ohm 50W(RMS) amp output?"

usually, ideal output from an amp is at 4 ohms, but it depends on the amp. (car audio, mind you)
read this article for specifics:
http://p079.ezboard.com/fcaraudiotalkfrm27.showMessage?topicID=47.topic
you may find other articles in that forum's FAQ area very informative on amplifiers as well. There are quite a few. I wrote them to save time.

"The reason I'm asking is that I'm planning to use a car amp indoors, and hook up 8-ohm bookshelf speakers to it .. for my home theatre system."

not a great idea, due to the need for a proper regulated power supply capable of supplying enough current to do the job. These power supplies cost about $1,800 US. Running car audio in a house is never a great idea. Just buy a home amp made for the job instead of ghetto rigging some half-assed solution.

"Using a 2-channel 4-ohm amp, what happens if I connect the positives and negatives of the 2 output channels to form a single output channel for a speaker?"

you'll start a very nice little house fire.
what you want to do is bridge the amp, and the amp has to support bridged mode.
more info here:
http://www.bcae1.com/bridging.htm

 

Bronze Member
Username: Vin

Post Number: 12
Registered: Jun-04
Thanks for your time and assistance, GlassWolf. I've read through the articles which you pointed me to .. very helpful indeed.

Regards
« Previous Thread Next Thread »



Main Forums

Today's Posts

Forum Help

Follow Us