noooooob Posted August 1, 2014 Share Posted August 1, 2014 (edited) I have read a bunch of different sources, do's and do nots etc about cab and head matching, but I cannot find any consistent info. So please, someone give me the lowdown; what wattage should I have on my cab and head at 4 ohm's? For example, to run a 6 x 10 800 watt cab, what wattage does my amp need to output at 4 ohms? Likewise, if I have a 450 watt amp, what wattage should a 4ohm cab be rated at? I know this is tackled a lot but I have seen so much conflicting information! Thanks! Edited August 1, 2014 by noooooob Quote Link to comment Share on other sites More sharing options...
HowieBass Posted August 1, 2014 Share Posted August 1, 2014 Amp heads are rated at different power output levels according to the speaker load presented to it, you can have the same head delivering different output levels to cabs rated at say 16 ohm, or 8 ohm or 4 ohm but the golden rule is never have cabs attached which present LESS than the minimum load in ohms and make sure the cab can take the power delivered. The amp head should have the rating marked on the back and it'll say what the minimum load is. So say a head is rated at 500 watts at 4 ohms, then it'll probably deliver 300 watts at 8 ohms and about 180 watts at 16 ohms - the manual should make it clear. You can have a single 4 ohm cab connected to it and get the full 500 watts output (so the cab must be able to take 500 watts), or a single 8 ohm cab (rated at 300 watts) and get 300 watts output or two 8 ohm cabs (each capable of taking say 300 watts) in parallel which act as a 4 ohm load and get the full 500 watts output (or indeed four 16 ohm cabs, each capable of taking say 130 watts each in parallel which together act as a 4 ohm load and get the full 500 watts out). You can always run a higher rated cab with a lower powered amp head (so cab rated at 500 watts with a head that only delivers 300 watts to that cab is fine) but you should not run a lower power rated cab than the head will output in watts for that cab impedance (so don't run a 500 watt head into a 300 watt 4 ohm cab if the head outputs 500 watts at 4 ohms). Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 1, 2014 Share Posted August 1, 2014 (edited) Is the conflicting advice you have seen been regarding valve amps? They need to be matched to cabs of the correct ohmage and power handling that Howie described about solid state amps, a head rated at 8 ohms needs an 8 ohm load for example where a solid state amp could be rated at 8 ohms yet run a 16 ohm cab all day just with a reduced output. Some amps are switchable as are some cabs so you must make sure they are compatible and on the correct settings if you have say a pair of 16 ohm 4x10 cabs for massive gigs then use just one cab at your next gig the head will need to be switched from 8 ohms to 16 ohms. Valve amps are not my specialist area as im too lazy to carry them but I think I am correct in my description ? Edited August 1, 2014 by stingrayPete1977 Quote Link to comment Share on other sites More sharing options...
noooooob Posted August 1, 2014 Author Share Posted August 1, 2014 [quote name='HowieBass' timestamp='1406925213' post='2516029'] Amp heads are rated at different power output levels according to the speaker load presented to it, you can have the same head delivering different output levels to cabs rated at say 16 ohm, or 8 ohm or 4 ohm but the golden rule is never have cabs attached which present LESS than the minimum load in ohms and make sure the cab can take the power delivered. The amp head should have the rating marked on the back and it'll say what the minimum load is. So say a head is rated at 500 watts at 4 ohms, then it'll probably deliver 300 watts at 8 ohms and about 180 watts at 16 ohms - the manual should make it clear. You can have a single 4 ohm cab connected to it and get the full 500 watts output (so the cab must be able to take 500 watts), or a single 8 ohm cab (rated at 300 watts) and get 300 watts output or two 8 ohm cabs (each capable of taking say 300 watts) in parallel which act as a 4 ohm load and get the full 500 watts output (or indeed four 16 ohm cabs, each capable of taking say 130 watts each in parallel which together act as a 4 ohm load and get the full 500 watts out). You can always run a higher rated cab with a lower powered amp head (so cab rated at 500 watts with a head that only delivers 300 watts to that cab is fine) but you should not run a lower power rated cab than the head will output in watts for that cab impedance (so don't run a 500 watt head into a 300 watt 4 ohm cab if the head outputs 500 watts at 4 ohms). [/quote] See but I have also been told that a peavey amp running 450 watts at 4ohms is fine to connect to a peavey 350 watt 4 x 10 at 4 ohms Quote Link to comment Share on other sites More sharing options...
noooooob Posted August 1, 2014 Author Share Posted August 1, 2014 [quote name='stingrayPete1977' timestamp='1406926023' post='2516042'] Is the conflicting advice you have seen been regarding valve amps? They need to be matched to cabs of the correct ohmage and power handling that Howie described about solid state amps. Some amps are switchable as are some cabs so you must make sure they are compatible. Valve amps are not my specialist area as im too lazy to carry them but I think I am correct in my description ? [/quote] Nope, im purely talking about solid state. Some sources say I should get a 500 watt amp at 4ohms for a 4ohm 800 watt cab, others say that you need more power than the cab, so get a 1000 watt amp Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 1, 2014 Share Posted August 1, 2014 All the experts will say is use your ears not your eyes! I run a 4 ohm 600watt 2x12 off a 300watt, 600 watt or 900 watt head with no problems, likewise ive ran my 1x12 off my 900watt head without problems. Farting and distorting are the tell tale signs which is why the experts say mixing cabs is not best practice unless you know they work together, a good 4x10 might mask the sound of a 1x15 being ruined, you wont know until the next time you run the 15 on its own and wonder why it has built in overdrive!lol Quote Link to comment Share on other sites More sharing options...
HowieBass Posted August 1, 2014 Share Posted August 1, 2014 (edited) You're always better matching the head and cab for power rating. You clearly can't achieve what the cab is rated at if the amp delivers less than the cab can take and though you can have a higher powered amp driving a lower powered cab, that's only ok if you don't intend to ever turn the amp up to maximum volume. Some amp heads are rather optimistically rated anyway. Some manufacturers quote peak music power so the head seems more powerful than somebody else's amp where they quote RMS output levels instead and for some reason valve amps are reputedly louder than solid state amps even when they appear to deliver the same output power (though again it's down to what's being measured and I believe valve amps act a bit like a compressor when driven at full pelt so you get a natural limiting/eveness of volume). Edited August 1, 2014 by HowieBass Quote Link to comment Share on other sites More sharing options...
xgsjx Posted August 1, 2014 Share Posted August 1, 2014 Don't get yourself so concerned with watts. Watts on a cab is how much heat it dissipates. Find an amp & cab that you like & just use your ears. If the cab farts, add another cab or get a more efficient cab. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted August 1, 2014 Share Posted August 1, 2014 I've been lead to believe that the FAQ on the Barefaced Cabs website holds a lot of truth and good advice regarding this topic http://barefacedbass.com/technical-information/mythbusters1.htm Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 1, 2014 Share Posted August 1, 2014 Ha I just read ALL of that faq only to see the bit at the bottom saying what I put at the start of post #6 Quote Link to comment Share on other sites More sharing options...
noooooob Posted August 1, 2014 Author Share Posted August 1, 2014 [quote name='HowieBass' timestamp='1406927103' post='2516058'] I've been lead to believe that the FAQ on the Barefaced Cabs website holds a lot of truth and good advice regarding this topic http://barefacedbass.com/technical-information/mythbusters1.htm [/quote] This is great, makes you wonder why some people strongly believe that you should have a more powerful amp than cab, or vice versa. Wish I'd seen this before I embarked on my google quest for knowledge! Quote Link to comment Share on other sites More sharing options...
bumnote Posted August 1, 2014 Share Posted August 1, 2014 [quote name='noooooob' timestamp='1406928205' post='2516076'] This is great, makes you wonder why some people strongly believe that you should have a more powerful amp than cab, or vice versa. Wish I'd seen this before I embarked on my google quest for knowledge! [/quote] Because many people on the internet will give you their opinion without necessarily knowing the facts Quote Link to comment Share on other sites More sharing options...
HowieBass Posted August 1, 2014 Share Posted August 1, 2014 I'd say you stand a better chance of everything working in harmony if you get the cab and amp ratings at least roughly equal; there's less to go wrong IMHO. Quote Link to comment Share on other sites More sharing options...
noooooob Posted August 1, 2014 Author Share Posted August 1, 2014 Thanks for the help guys, im a lot clearer on the whole subject! Quote Link to comment Share on other sites More sharing options...
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