How to match Amps to Cabs?

Guitarist

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Not sure if this is the right place for this question but I'll ask anyway.

Amps have ratings like wattages, ohms and impedance. Is there a way to tell whether a certain amp for example rated at 50 Watts and 8 Ohms can be played through a certain Cabinet?

How do I make sure an Amp and a Cab will work together with one or the other blowing up?

Thanks in Advance.
 
--->Amps have ratings like wattages, ohms and impedance. Is there a way to tell whether a certain amp for example rated at 50 Watts and 8 Ohms can be played through a certain Cabinet?

every amplifier or speaker will make sound (even if it pops lol) regardless of what wattages is running. obviously the amp with dangerously high power will blow the coils in the lower rated speakers.

general rule of thumb in professional audio scene. speaker xxx watts RMS rated, you should power it at 1.5 times of the xxx watts. note that it must be the true RMS rating. however due to the fact that many components nowadays are made in china, you may never know if the rated numbers are real.

true experience --> we walk into a huge stage, huge line arrays... very familiar blue logo ... but when i call the factory they have no idea they have made line arrays part of their product line with that description. move on ... check the amps wires etc ... power up and play back ... O M G ... sounds like Cxxp ... took 2 freaking days to figure out the speaker calibrations from below scratch point ... that is wat i call a real challenge lol.

--->How do I make sure an Amp and a Cab will work together with one or the >other blowing up?

step 1 = impedance matching.

amp says it can work at 4-8 ohms, speakers = 4 to 8ohms ---> looks fine --> 1 to 1 matching.

amps says only 8ohm, speaker says itself is = 4 ohms. mismatch, it still works but at your own risk of amp blowing. (takes alot to blow a amp, you have to crank it real hard. even for mismatches, it is not destructive to an item if you do not try to exceed certain thermal thresholds electronically, this is hard to tell, it is not the same as the volume knob threshold say eg 10%. every manufacturer and model have a diff character on this)

amps says only 8ohm, you have 2 speaker of 16ohms. parrallel wire this and you get 8ohms. so it works. (find parrallel wiring in wikipedia for those who not sure, it is not SERIES). similarly 4ohm capable amp to 2x 8ohm parrallel wired speaker cabs.

power matching as per explained on top paragraph. for parallel wired speaker loads, double 100w cabs in parrallel = 200w.

>Thanks in Advance.[/QUOTE]
you r welcome ...

side note --> the above notes are somewhat laymans way of explaining the general methodology of matching apples to oranges.
 
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Too much impedance??

^^ Thanks Accesscoms for the great response ^^. You are right, it is an apples to oranges comparison but you've explained it well.

Now, is it possible to have too much impedance on an Amp? For example if the Amp is rated 4 Ohms and you connect it to a 16 Ohms set of speakers, would it make the combination sound weak or soft?
 
^^ Thanks Accesscoms for the great response ^^. You are right, it is an apples to oranges comparison but you've explained it well.

Now, is it possible to have too much impedance on an Amp? For example if the Amp is rated 4 Ohms and you connect it to a 16 Ohms set of speakers, would it make the combination sound weak or soft?

when you encounter this, the below is what usually will happen :

amp --> 4ohm rated for 200w
pump into speaker 8ohm --> in theory u get 100w
pump into speaker 16ohm --> in theory u get 50w

BUT ... if you are talking newer range of high tech amps (which i am experimenting with a manufacturer now), the wattage does not scale with impedance matching. this amps (at this point i am refering to the IC chips etc) i so far i know of is being used in consumer goods such as car amps (pioneer), "hi-fi siao" amps, etc.

o yes i forgot to mention ... yes to some unique amp design ... it is possible to have too much impedance, some amps die die must be 8ohm. some amps due to this will go hay wire and start to self oscillate etc .... u ever hear ghost radio in cheapo sound system before? hehehe ... can be quite scary if u practice guitar in middle of night ... lol :)
 
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