I bought an Ashdown Blue 180-15. I am thinking about getting an add-on cabinet, maybe a 2-10 or a 4-10. Thats the easy part. Knowledge is the trick....and I'm runnin a tad short. In the specs, it states that minimum output ohms for an extension cabinet is 4 ohms. Could someone look at the specs, at http://www.musiciansfriend.com/product/Bass/Amps?sku=485037, and tell me if I should get something like THIS? Its 8 ohms. Thats more than 4 ohms. Is that in line with "a minimum of 4 ohms?" I'm a tad in the dark here. The 180-15 has two 1/4 jacks in the back. One has the cord from the internal speaker plugged into it, the other is for an extension. It says 'external speaker minimum 4 ohms. How many ohms is this amp? Will any cabinet with more than 4 ohms work? 8? 16? What would the difference in the sound be. depending on putting a 4 or an 8 ohm cab? An yone with patience, and a basic knowledge of electric circuitry.......help. Gimme a twenty words or less (just kidding) tutorial on this PLEASE... orrrr, should I get a higher watt amp w/ 4/10's, and use the 180-15 as an external cab?

8 is bigger than 4, so you are good there. Second, amps don't have "ohms" - it is a nonsensical figure in that context. An amp is rated to drive a MINIMUM load, and that is in ohms . .. perhaps that's what you mean here . . . From reading the rather sparse specs at MF, I get that the head can drive 4 ohms minimum - period, not that the external can be as low as 4 ohms. As such, I suspect that the internal speaker is an 8 ohm speaker, and as such, you can use another external 8 ohm speaker, for a total load of 4 ohms, OR disconnect the internal, and use JUST an external 4 ohm cabinet. (A quick look at the online manual confirms this - 4 ohms minimum TOTAL load, including the internal speaker.) However, the manual does not match your description of having two 1/4" jacks - the current units have one 1/4" and one Speakon. Do you also have a speakon? If not, then they just changed one connector, if so, then the manual that is online is incorrect for your amp . . . . - Tim

thanx....so then by minimum, the reference actually means to MATCH? ie, if its a 4 ohm load, then it would support TWO 8 ohm speakers, but not an 8 and a 16? Jeez...I gues I KNOW mt next research bit...Aren't ohms a measurement of resistance, and if so if the amp provides power to speakers with 4 ohms of resistance, it seems backwards...that 4 ohms should be divided into 2 ohms for each speaker. I will have to re-educate myself....oooorrr, I could just continue to feel rather errrr.....ddduuuhhh! (lol) Thanks for this and any future help.

No, no match required. A minumum load of 4 ohms, however you get it . . . one eight and two sixteens, four sixteens, eight 32s, 4 32s and 2 16s, whatever. An 8 and a 16 will give a load of 5.33 ohms, which will be fine. You just can't run an 8 and a 4 - that would give 2.6 ohms, which would overload your amp. Just saw your picture too . . . it pretty clearly states what we have been saying - four ohm minimum load, no reference to an external cab - it's the rating for the entire amp. And yes, the new ones are different, and have a speakon instead of the second 1/4" jack. - Tim

what is a (simple) formula for determinng ohms value? like you said an 8 + 16 would give 5.33 ohms. how do you determine that? Thanks again for the help. OG

Ohms are a measure of resistance. and parallel resistances give a total less than either. Think if it in terms of water hoses, with a bigger hose having a lower resistance (lower ohm figure). If you use a certain size hose, things are fine, but lets say if you let it flow too fast, the pump blows up. If you use either a bigger hose from the faucet, OR two smaller hoses, you can get the same total flow, right? Same with your amp. A 4 ohm cab is the biggest "hose" you can use, and two 8 ohm "hoses" (1/2 the size of the 4) will give the same flow. If you want to do the math, resistances in parallel combine like so: R1*R2/R1+R1=resistance. So, from my prior answer to your question about an 8 and a 16, we get: 8*16/8+16 => 128/24 = 5.33 (If you have more than two, the formula is a bit more complicated, so I won't go into it here . . . ) - Tim