impedance

[kyleo]

Hi,
I am wanting to buy 2x 250w speakers (power RMS). the impedance on each speaker is 8 ohms. I will need an amplifier to power these but when i look at the specification of the amp i was going to buy, it says this... Power RMS (4 ohm) 2x250w.

would these speakers still work with this amp?

many thanks

 

[avaserfi]

That means the amplifier will go down to four ohms and most likely has 125w at 8 ohms which should push the speakers. Names and models will help in telling you 100%.

 

[MDS]

If the amp is capable of pushing 4 Ohm speakers it should have no problem with 8 Ohm speakers; it's the opposite case that can present a problem.

 

[kyleo]

Thanks for that. so realistically If I got that amp It would be as much use getting 2 125W speakers

 

[j_garcia]

The wattage rating on the speakers is all but useless when choosing them. That is generally the max rating and does not mean that is how much power you need to drive them.

 

[fmw]

Common practice is to rate amplifier power into an 8 ohm load. Rating it into a 4 ohm load simply overstates the real amplifier power by a factor of 2X. Your amp should have a clipping level at around 1/2 that power figure into 8 ohms.

 

[edmcanuck]

Thanks for that. so realistically If I got that amp It would be as much use getting 2 125W speakers

If you ever use more than 15 watts of continuous power into any speakers of average sensitivity, then make sure you set aside some money for bail after you're arrested for disturbing the peace.

 

[PENG]

If that amp is rated for 2X250W into 4 ohms it will most likely be rated for 2X150 to 2X160W into 8 ohms. Of course if the manufacturer wanted to make it look like it is capable of "doubling down" then it could have rated it for 2X125W into 8 ohms, as others have suggested.

 

[kyleo]

Think I no how it works now. If it was a 2x 250w at 4 ohm amp then it would be round about 2x125w at 8 ohm. it could also be 2x 500w at 2 ohm. thanks for the help every1

 

[kyleo]

1 more thing... when you conect speakers up (bridged). does this mean it is as a series circuit. Do you do this through just one of the channels or is there a seperate channel for this.
thanks

 

[markw]

A few simple words/cautions on bridging.

1) You don't "bridge" speakers, you "bridge" amps.

2) Not all amps lend themselves well to bridginhg. Unless an amp is designed for "bridging", don't. RTFM for this.

3) When you conect a speaker to a bridged amp, it "sees" the speaker load as one half of it's rated value. i.e. it "sees" an eight ohm speaker as four ohms, a four ohm speaker as two ohms, etc...

You may want to read a little more on some of this stuff at the "AV University" off this site's home page before getting your hands dirty. You seem to be picking up buzz words without knowing their meaning or application.

 

[PENG]

1 more thing... when you conect speakers up (bridged). does this mean it is as a series circuit. Do you do this through just one of the channels or is there a seperate channel for this.
thanks

In theory if you connect two identical 4 ohm rated speakers in series the amp will see an equivalent impedance of 8 ohms. In that case you would need 4 identical speakers, two ("bridged" in series) per channel.

I am not saying it is a good thing to do, but if you do, that's how the impedance would work in terms of electrical theory. As markw said, people typically bridge amps, not speakers.