Re: Someone explain mixing speakers in cabinets
I know you have to make the total load equal the amount of ohms your amp is puting out
Ohms is a measurement of impedance (resistance), not output. Yes, ideally, the output should match the impedance setting of the amp if it is a tube amp. On a SS amp, the impedance needs to be more than the minimum rated impedance of the amp.
As far as the speakers in the cabinet, they should all be the same impedance (ohms), the power will be split equally to all the speakers then, irregardless of power rating or sensitivity. So, 100W into 4 speakers of equal impedance will be 25W per speaker.
Sensitivity is a measure of efficiency, the number is the dB reading at 1' (or is it 1meter?) with a 1W (IIRC) signal into the speaker. In the end what you need to know is, the higher the number, the louder the speaker will be. So, i you mix some really inefficient speakers in your cabinet with some very efficient ones, you will hear more from the efficient speakers. Doesn't mean you can't close mic the inefficient ones though. Don't sweat the little stuff though, 5 - 10 dB difference in the efficiency ratings won't really be noticeable. Lots of cabs mix G12T-75s with V30s and the V30s are rated at higher sensitivity than the G12Ts. The frequency response of the speaker will also affect the perceived loudness of the speaker to the player/listener also.
As far as power ratings, people get bent out of shape on this alot too. You probably want the lowest rated speaker to be able to minimally handle its share of the load (remember 100W into 4 equal impedance speakers is 25W per speaker). But, unless you run your amp on 10, it's not putting out it's full power, but also remember that a 100W tube amp is probably peaking at around 160W or so if it is on 10. That said, lots of great recordings have been made running a cranked Superlead into a 4-12 cabinet with 4 25W Greenbacks. Yes, technically the speakers should have blown, and one may have occasionally, but they are usually tougher than people give them credit for. But for those of us that don't have a cache of speakers laying around, it's probably better safe than sorry. For example, you can get an Eminence Legend GB12 which is a 50W (or better, don't remember exactly) Greenback clone, so you can get close to the GB sound with more headroom.
*EDIT*Jeremy was apparently typing at the same time I was. I forgot add, when you are wiring speakers, you need to know the difference between series and parallel and how they affect impedance. Most 4-12s are wired in a series/parallel arrangement, so if you use 4 16 ohm speakers you get a total impedance of 16 ohms because of the way they are hooked up. There are some websites out there that explain this well with a little searching.
Hope this helps,
Roger
mg:
