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Help understanding Ohms

Discussion in 'Amps and Cabs [BG]' started by LAKLAND011, Apr 23, 2001.

  1. My Ashdown combo amp has two outputs. Both of them are 4 Ohms. One goes to the internal speaker and the other is for an extension speaker. Does the extension have to be 4 Ohms? If it wasn't how would it impact my amplifier? How would it affect the output wattage (I beleive the Ashdown has two 300W outputs - can anyone here confirm this)? It is a ABM C115-300.

    Thanks for any help anyone can offer


  2. I went and checked the ashdown site. It says your amp has a minimum impedance rating of 4 ohms, not that both jacks are good for 4 ohms. The jacks are in parallel. So you can either plug in (1) 4 ohm speaker into 1 jack, or you can plug in (2) 8 ohm speakers, one into each jack. So you need to make sure your internal speaker is 8 ohms in order to add in another 8 ohm cabinet. If your internal speaker is 4 ohms, you can add nothing. I'd guess it is 8 ohms, so that you can add another 8 ohm cab.

    Your amp has a single 300 Watt power amp. The outputs are both taken off this one power amp. It puts out 306Watts into a 4 ohm load. So that means it puts out about 150Watts into an 8 ohm load.

    Look at the back of your internal speaker or check your manual to get its impedance to see if you can add another cab. The brochure doesn't say what it is. I'll go back and see if I can find a manual.

  3. Couldn't find it. Their single 15 cab is 8 ohms though. So your combo probably is too. They don't want to put the impedance of the internal speaker on the brochure, because that means you can't get 300 Watts out of the amp in the stock configuration. You have to add on a 2nd 8 ohm cab to get the full 300 Watts out. So you have most likely been playing with only 150 Watts of power. If/when you add another 8 ohm cab, you will double your wattage as well. So if you add another Ashdown 1-15 cab just like your combo, you'll double your speaker area, and you'll still be sending the same power to your internal speaker, and you'll be sending an additional amount of power you couldn't get before to the other speaker, so you will in effect get a +6 dB increase in sound. Which will not be twice as loud as before due to our hearing being exponential, but will definitely be louder. :D You'll also have more headroom. Contact the manufacturer to verify all this.

  4. Thank you Chris. You've been a huge help. Mark Gooday from Ashdown just sent me an e-mail confirming the same. I appreciate you taking the time to help me understand.



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