Amplifier matching

[jckk335]

Hi looking for some help, I had a 500w 4ohm amplifier connected to 2 250w 4ohm speakers. However this amplifier has died and gotten rid of.

 

I do have a 200w 8ohm amplifier as a spare, so after looking around for information on what would the outcome be in terms of power, impedance, whether or the speakers or the amp will not work properly.

[MarkPAman]

Hi looking for some help, I had a 500w 4ohm amplifier connected to 2 250w 4ohm speakers. However this amplifier has died and gotten rid of.

 

When you connect 2 speakers together (in parallel) the impedance goes down. In this case you've "made" a 500W 2Ω speaker. The amp's 4Ω figure is the minimum it can drive, so you're asking it to work too hard - with predictable results.

 

I do have a 200w 8ohm amplifier as a spare, so after looking around for information on what would the outcome be in terms of power, impedance, whether or the speakers or the amp will not work properly.

 

That's not going to last at all!

 

You could arrange to connect the speakers in series* which would give you an 8Ω load, but with only 100W each to drive them, they'll not go loud.

 

*This would probably require some rewiring inside the speaker - I'd not recommend it.

[jckk335]

Cheers for your reply. The reason the 500w amp was gotten rid was one of the binding posts snapped and when it was replaced one of the cables on the bridge board, the solder failed and would not reattach to the board, resulting in an electrical fault.

[Jivemaster]

"500w 4ohm amplifier connected to 2 250w 4ohm speakers."

-If you mean two speakers, one to each channel, that's probably an OK system. Why did the amp die?

 

Have you read the spec for the 200w amp? If it's rated at 200 into 8ohms it may or may NOT be suitable for 4 ohm operation, at a slightly increased power and increased risk of thermal failure.

[jckk335]

The reason the 500w amp was gotten rid was one of the binding posts snapped and when it was replaced one of the cables on the bridge board, the solder failed and would not reattach to the board, resulting in an electrical fault.

 

As for the 200w amp it has been a while since I have looked at the manual so properly have to do that

 

Just had a good luck and the 200w amp says 60watts rms at 4ohm

50watts rms at 8ohm

[TonyMitchell]

Keeping it simple, if you have a pair of 4Ω speakers rated at 250W and are selecting an amplifier to drive them, one loudspeaker per channel, with sufficient headroom, you should look for an amplifier that delivers between 375-500W RMS per channel at 4Ω. You are more likely to damage the loudspeakers with an under-powered amplifier pushed too hard, than with an over-powered amplifier. 1.5-2.0 x the RMS is a good match. Edited November 12, 2019 by TonyMitchell

[jckk335]

Cheers that what I thought and was getting baffled to find the right and wrong way of amplifier matching. So I am quite pleased to not go ahead and just connect the amp and speakers as it would cost far too much to fix if they blew.