Rabs Posted March 22, 2012 Share Posted March 22, 2012 So, guitars, I know quite alot about. Amps not so much, ive tried many in the shops and know what like the sound of and thats about as far as ive ever really gone with technicalaties of amps.. Ive had a small combo Marshall MG 15FX for many many years, its only a 15 watt but I dont gig any more so is good enough for me to use at home and sounds every much as bit of a Marshall as it should.. But last year I got the MG 15HFX which is like a mini stack amp. Now because ive always had a combo, I dont undertsand how the wattage works on heads and cabs and how they add up. I understand that its a 15 watt head but how does the wattage of the head effect the volume? As well as the 15 watt head it comes with two 10" stack speakers so you can use one or both.. But I never got any more information apart from that. Looks like this And in this video at NAMM they are showing the mini heads that are 1w but obviously with huge cabs.. so I just dont get how it works? So watt (sorry :)) I want to ask is how loud is my amp in total wattage with the speakers? Ive looked on the Marshall site and it doesnt say (pretty useless site really) http://marshallamps.com:3339/product.asp?productCode=MG15HFX&pageType=SPECS And what I have seen by trying to search google on a forum is that someone said its 100w with both speakers.. But that doesnt really sound right to me and it only cost £250 new so that doesnt really reflect the price. Ive always assumed that the 10" speakers were gonna be 15w each and if that is the case what is the overall wattage with a 15w head (wow this does my head in lol) :P So does anyone know? (and sorry for the long post but wanted to explain properly (or try anyway :P) (oh and yes ive looked on the back of the speakers and theres nothing.. they are covered but I was hoping to find the answer without having to undo them) Link to comment Share on other sites More sharing options...
Guest farnsbarns Posted March 22, 2012 Share Posted March 22, 2012 Guitar amps are rated in watts RMS. (root mean squared) which is a bit like saying "the output of the amplifier with an average level input, is 15 watts. HiFi equipment is usually rated in watts PMPO (peak music power output) which is a bit like saying "the output can reach 15 watts during the absolute extremes of the input. Eg, during a snare hit etc". Because guitar amps are rated RMS, at extremes of input you can get a lot more output than rated so you need speakers that'll take it. Your cabs are probably rated at 50 watts each so some nitwit is saying his amplifier is 100 watts. I joined that forum for one thread, one was enough, I'd steer clear if I were you. When talking about amplifier watts we are talking about a measurable power output. However, when talking about speaker watts we aren't, we're talking about the levels at which a speaker will survive. My cab has 300watts of speakers but the head is 60watts RMS, probably peaking at no more than 85/90, 100 at a push. Hope that helps. Link to comment Share on other sites More sharing options...
charlie brown Posted March 22, 2012 Share Posted March 22, 2012 See if this helps...??? http://www.guitarnuts.com/amps/myths.php CB Link to comment Share on other sites More sharing options...
Rabs Posted March 22, 2012 Author Share Posted March 22, 2012 See if this helps...??? http://www.guitarnuts.com/amps/myths.php CB Cheers CB, it certainly helped me understand a bit more about the wattage and volume link.. But id still like to know just for matter of fact about my amp. I guess I will just have to take the backs off if I want to find out :) I got it though actually because I could never justify the many hundreds on a huge stack amp and didnt need one.. But when I saw that mini stack in the shop I just had to get it cos it looks so cool to have a stack and have always dreamed of one since I used a JCM 800 back in the band days (thats what I used in the rehersal studio).. Maybe one day I will get to gig it :) and as for some of those facts about amps.. I once played quite a famous venue called the Royal Standard which is (or was) a pub owned by Suzie Quatro and had been a place many famous bands started out at. Anyway, back then all I had was a tiny crate practice amp 15w and I can tell you from personal experience that it was nowhere near loud enough and that was miked up and at full volume everywhere.. I had to beg one of the other bands to borrow theirs lol... I actually blew that amps speaker several times trying to get more out of it than I should have lol.. Link to comment Share on other sites More sharing options...
Rabs Posted March 22, 2012 Author Share Posted March 22, 2012 See if this helps...??? http://www.guitarnuts.com/amps/myths.php CB I was just thinking about this further.. If theres no difference between a 1w and 15w head and not much difference between a 15w or 100w speaker why do they make different ones? are the sound differences that varied? Is it just for missinformed people who think more is better? All a bit strange really. I guess it does go to show that you should buy, only on what it sounds like and if it has the features you want... Link to comment Share on other sites More sharing options...
charlie brown Posted March 22, 2012 Share Posted March 22, 2012 Well, most of us, that have played "out," have...at some point, experienced not having enough volume, for the venue, or circumstance. Blowing speakers, is one result, but often that is more to do with mis-matched speakers to the amp head's capability. One 25 watt speaker, being powered by an overdriven 50-100 watt tube amp, for example. My old Marshall Major (200 watt head) had to have both 100 watt cabinets hooked up, to run at it's "sweet spot," otherwise just the one 100 watt cabinet (4X25 watt speakers) would be at risk. I did use it, with only one cabinet, at times...but it was nowhere near "Cranked!" Use at the very least, comparable wattage, speaker to amp head output. One simple/safe "rule" is, if you use say a 15 watt head, use a 30 watt speaker/cabinet. I.E. speakers, with twice the wattage handling power, to what the head puts out. My Blues Jr.(15 watt) has a 30 watt Celestion "Vintage 30" in it. It's sings, when "cranked!" Also...make sure the ohms match, from head to speakers! Many modern amps/heads, have either differing ohm output jacks, or switching. So be sure to match that, with appropriate ohm speakers. Some, newer ones even "self adjust." http://www.notreble.com/buzz/2010/05/27/speaker-impedance-how-to-properly-match-your-amp-head-with-cabinets/ CB Link to comment Share on other sites More sharing options...
krock Posted March 22, 2012 Share Posted March 22, 2012 Also...make sure the ohms match, from head to speakers! Many modern amps/heads, have either differing ohm output jacks, or switching. So be sure to match that, with appropriate ohm speakers. Some, newer ones even "self adjust." http://www.notreble....-with-cabinets/ CB And linking with this always make sure there is a load when the head is turned on (no sexual reference intended ). Ive had mates that have buggered their amps by not doing this Link to comment Share on other sites More sharing options...
Rabs Posted March 22, 2012 Author Share Posted March 22, 2012 And linking with this always make sure there is a load when the head is turned on (no sexual reference intended ). Ive had mates that have buggered their amps by not doing this When you say Load do you mean make sure somethings plugged into it? Link to comment Share on other sites More sharing options...
charlie brown Posted March 22, 2012 Share Posted March 22, 2012 When you say Load do you mean make sure somethings plugged into it? Yeah...Just make sure the proper speaker (wattage and ohms) is PLUGGED IN, PRIOR to turning on the amp. CB Link to comment Share on other sites More sharing options...
marvar Posted March 22, 2012 Share Posted March 22, 2012 I was just thinking about this further.. If theres no difference between a 1w and 15w head and not much difference between a 15w or 100w speaker why do they make different ones? are the sound differences that varied? Is it just for missinformed people who think more is better? All a bit strange really. I guess it does go to show that you should buy, only on what it sounds like and if it has the features you want... I can understand your confusion- a watt is just a way to measure amount of work, in this case, power amp output. The reason for more wattage is mainly about headroom and 'feel' in an amp- more wattage, more headroom before the onset of power tube distortion. Lot's of folks get confused with speaker wattage, which really has nothing to do with how many watts your amp puts out- Solid state is a whole different ball game, you need to keep the 2 (SS/Tube) separate when thinking about power amps. But, A watt, is a watt, is a watt- Link to comment Share on other sites More sharing options...
kaleb Posted March 23, 2012 Share Posted March 23, 2012 My bass player used to have a Fender 400 PS back in the 70s (73-77 ish). Very rare amp. It had a master volume. I heard Albert King used one for a while, even though it was designed for bass (DO BASS PLAYERS REALLY LOVE BASSMANS?). 400 watt head. But it was rated as putting out 1200 watts RMS. Came with 2 2x15 bottoms. Marshall 2203 100w heads (in the JMP and JCM 800 incarnations made from 75-81 in the former and 81-90 in the latter) actually put out about 177 watts at normal levels. Speaker wattage should match up be higher in wattage compared to the amplifier powering it. Like a 100 watt Marshall with 4 Greenbacks (25 watts) sounds great, as the lower speaker wattage makes for a very pleasing tone, but they have a tendency to fart, modulate, do this square wave thing in the background, and BLOW UP! That Marshall with 4 Electro-Voice EVM-12Ls (200w) will not have those problems, but will be way to uncivilized and it will be harder to push. I generally prefer the 65 watt speakers. Link to comment Share on other sites More sharing options...
stein Posted March 23, 2012 Share Posted March 23, 2012 I think you get the amp wattage thing. If you don't, it has been explained above quite well. As for the SPEAKERS, I think that is where you are stumped. The stated wattage of a speaker is more of a generality than an actual rating, which represents what the manufacturer says it should handle. But beyond that, there really isn't a lot to go on. For volume, the SENSITIVITY is a big one. That is the measurement of how much volume it will put out for the amount of power put into it. A speaker with a high sensitivity rating will be louder than one with a low rating, given the same amount of watts. It is a little misleading, in that an 87db rating is not 10% less than a 97db rating. I think something like 89 is twice as loud as 87. There is 2 kinds of power handling for a speaker. One is how much power it can actually absorb and turn into volume, and the other is how much it can take before it blows up. For any speaker, it has mechanical and electrical limits for how much watts it can handle and turn into volume. When it approaches the limit, it becomes less and less efficient as you turn up, and eventually won't get any louder. It feeds back resistance on the power amp and actually causes it to distort faster, because the power amp is pushing harder against a wall. We LIKE that. The problem with that, is that would be ideal if the speaker had infinite strength, but this ain't ever the case. if it is given to much current it can't convert, it gets hot. All speakers dissipate heat, but give it too much it can't dissipate and you melt the wires, or melt the glue, or deform the parts. Manufacturers usually use THIS as the ideal for what they state for "power handling". Generally speaking, for all 3 of these things, the larger, beefier "higher wattage" speakers will have the highest ratings for all of these things. Link to comment Share on other sites More sharing options...
kaleb Posted March 23, 2012 Share Posted March 23, 2012 As far as my tonal preferences go, I like higher (as in 50+) wattage amps mostly for the headroom and "big-ness". And 4x12s. My favorite kind of amps are good Marshalls (Jubilees, Vintage Modern, single channel JCM 800s, and the MV JMP heads, and of course the non-master models). My favorite kind of speaker is either an Electro-Voice EVM-12L 200w, Celestion G-12 70s (like the ones used in the late 70s cabs), and the Celestion G-12 65s, as well as WGS speakers, Tone Tubby hemp cone speakers, and the Scumback speakers. Link to comment Share on other sites More sharing options...
RaysEpiphone Posted March 23, 2012 Share Posted March 23, 2012 Manufacture's will rate there gear with a few different thing's in mind. As some one already said RMS or root means square is a rating that you have to look at some other speck's of the amplifier. I believe you look at the THD or total harmonic distortion, so lets say you have a 100 watt amp that is rated for THD. What ever the THD is, say it's .002%, that means when the amp is running at that THD (.002%) you'll get 100 watt's. Then you have other manufacturers that will rate there stuff at typical or maximum, maximum or peak power is where you start damaging the amp so that 100 watt amp I was just talking about may very well be several times greater in rating at maximum out-put. Typical could be anything really I don't know. I've seen JBL speaker's with "program" and "instrument" rating's on the paper work I got with them, program meaning fully produced, mixed and mastered play-back track's (store bought CD) while instrument being just that, a raw bass, guitar, drum kit etc... Also, I've been told that you should run a 100 watt Marshall head with 2 cabinet's, although I reckon you could change the ohm's switch on the back of the head to limit out-put from the amp. I think the 1960 cabinet is rated at a lower wattage than the late 1960's (and on) cabinet are so maybe the higher wattage cabinet would fair better with a 100 watt head. Link to comment Share on other sites More sharing options...
marvar Posted March 23, 2012 Share Posted March 23, 2012 Also, I've been told that you should run a 100 watt Marshall head with 2 cabinet's, although I reckon you could change the ohm's switch on the back of the head to limit out-put from the amp. I think the 1960 cabinet is rated at a lower wattage than the late 1960's (and on) cabinet are so maybe the higher wattage cabinet would fair better with a 100 watt head. BTW= changing the ohms switch has NO effect on output wattage, and will not limit output from the amp- (but, changing the ohm load on a solid state amp will usually affect wattage) as said before a watt is a watt is a watt, your amp is still 100 watt marshall. 1 watt @8 ohms is still 1 watt, 1 watt@ 4 ohms is still 1 watt. Link to comment Share on other sites More sharing options...
Rabs Posted March 23, 2012 Author Share Posted March 23, 2012 Thanks for the answers guys.. Now I know why I only know so little about amps lol.. I only know so much about electricity, ohms and watts and stuff so all this gets a bit confusing.. I think i will just not worry about it and stick to playing guitar :P Link to comment Share on other sites More sharing options...
martinh Posted March 23, 2012 Share Posted March 23, 2012 This is the "clift notes" version as I was taught it many years ago. [1] Power vs volume Amplifier power is measured on a linear scale, e.g., 100W is twice the power of 50W. However, the ear perceives sound on a logarithmic scale. 100W does not sound twice as loud as 50W through the same speaker. For the ear to perceive a sound as being twice as loud, it requires ten times the power e.g., 10W is twice as loud as 1W, 100W is twice as loud as 10W. [2] Speaker efficiency There is also no direct relationship between amplifier power and perceived volume. It depends on how efficient the loudspeaker is. Loudspeaker efficiency is measure in terms of sound level output (in decibels (dB)) versus input power. A typical speaker efficiency rating will say something like "produces 95dBm at one meter when driven with 1 watt." Loudspeaker efficiencies can vary by more than 3db, and 3db represents a doubling of the input power. Therefore, an efficient speaker will produce the same volume from a 50W amp that a less efficient speaker will produce from a 100W amp. [3] Speaker impedance (resistance) Tube and transistor amps behave differently if you change the impedance of the speakers. The lower the impedance presented to a transistor amp, the more power it produces. Many transistor amps will state output in terms of impedance, e.g., 100W at 16 ohms, 200w at 8 ohms, 350W at 4 ohms etc. Tube amps behave differently . they produce maximum power when the speaker impedance is matched to the tubes by an output transformer . The transformer on a Marshall usually has "taps" for 4, 8, and 16 Ohm speakers. The amp works properly only when the tap is properly set for the speaker being used. So: A 100W tube amp produces 100w under any of these circumstances: Transformer set to 16 ohms, 16 ohm speakers Transformer set to 8 ohms, 8 ohm speakers Transformer set to 4 ohms, 4 ohm speakers Any other setting, say Transformer set to 4 ohms, 16 ohm speakers, will produce less power, and is not too good for the output tubes. Link to comment Share on other sites More sharing options...
Versatile Posted March 23, 2012 Share Posted March 23, 2012 Thanks for this thread...an area of interest and confusion for many... BTW that mini stack looks good enough to eat I've noticed these coming on the market in recent years...how the manufacturers exploit every niche possible I've only recently gone the head/cab route with a Laney 50w, having always had combos before Luckily there was a specific cab recommended for the head, so I went with that Also I have since explored the 'extension cab' possibilities with a combo A Laney VC 30 2x12 combo plus a 2x12 ext looks good, sounds good and is well portable As mentioned, adjusting the ohms as appropriate is very important.... V Link to comment Share on other sites More sharing options...
Thundergod Posted March 23, 2012 Share Posted March 23, 2012 Guitar amps are rated in watts RMS. (root mean squared) which is a bit like saying "the output of the amplifier with an average level input, is 15 watts. HiFi equipment is usually rated in watts PMPO (peak music power output) which is a bit like saying "the output can reach 15 watts during the absolute extremes of the input. Eg, during a snare hit etc". Because guitar amps are rated RMS, at extremes of input you can get a lot more output than rated so you need speakers that'll take it. Your cabs are probably rated at 50 watts each so some nitwit is saying his amplifier is 100 watts. I joined that forum for one thread, one was enough, I'd steer clear if I were you. When talking about amplifier watts we are talking about a measurable power output. However, when talking about speaker watts we aren't, we're talking about the levels at which a speaker will survive. My cab has 300watts of speakers but the head is 60watts RMS, probably peaking at no more than 85/90, 100 at a push. Hope that helps. All this. Plus, more speakers move a little more air (well, actually they move air differently than just 1) so they will sound to you like the amp is louder but it's just how more speakers make it so you enjoy more of some frequencies than with just one. Link to comment Share on other sites More sharing options...
Twiz Posted March 23, 2012 Share Posted March 23, 2012 Thanks for this thread. I don't know much about this stuff. Good info. Link to comment Share on other sites More sharing options...
Californiaman Posted March 23, 2012 Share Posted March 23, 2012 Oh yeah. Thundergod is right. More speakers push more air and theirfor sound louder no matter what the wattage. Of course this post needs approval from a moderator before any of you will get to see it. Link to comment Share on other sites More sharing options...
RaysEpiphone Posted March 24, 2012 Share Posted March 24, 2012 BTW= changing the ohms switch has NO effect on output wattage, and will not limit output from the amp- (but, changing the ohm load on a solid state amp will usually affect wattage) as said before a watt is a watt is a watt, your amp is still 100 watt marshall. 1 watt @8 ohms is still 1 watt, 1 watt@ 4 ohms is still 1 watt. Ummm, yeah but if your cabinet is rated for 8 ohm's and the amp is set for 4 ohm's your not going to get full out-put from the amp, right? We had a power amp for our PA that would run at 2, 4 or 8 ohm's, rating was 750 watts per channel at 2 ohm's and around 200 watt's per channel with an 8 ohm load. We connected three 8 ohm speaker's to each channel and it was loud as heck! I'm talking rattle the whole house loud! but with just one of those connected it was no where near as loud, in fact you couldn't hear over the stage noise when we played when the amp was running at 8 ohm's. It was a solid state amp and a Marshall is a full tube rig, that will make a difference? Just asking. Link to comment Share on other sites More sharing options...
marvar Posted March 24, 2012 Share Posted March 24, 2012 Ummm, yeah but if your cabinet is rated for 8 ohm's and the amp is set for 4 ohm's your not going to get full out-put from the amp, right? We had a power amp for our PA that would run at 2, 4 or 8 ohm's, rating was 750 watts per channel at 2 ohm's and around 200 watt's per channel with an 8 ohm load. We connected three 8 ohm speaker's to each channel and it was loud as heck! I'm talking rattle the whole house loud! but with just one of those connected it was no where near as loud, in fact you couldn't hear over the stage noise when we played when the amp was running at 8 ohm's. It was a solid state amp and a Marshall is a full tube rig, that will make a difference? Just asking. Your PA power amp is Solid State- go back and read the posts- your Marshall is still making 100 watts, no mater what ohm setting. The perceived loudness may be different, but, you are just causing unnecessary wear and tear, and heat on your output transformer, which SS amps don't have. Link to comment Share on other sites More sharing options...
Rabs Posted March 24, 2012 Author Share Posted March 24, 2012 Thinking about this further actually I think also the acoustics of a room totally makes all the defference to how loud you will sound.. ive played in pubs where mostly the acoustics are terrible and you really have to pump it out. But I got that vid of me (posted on another topic about natural reverb) playing in an old church.. and my small 15w practice amp fils that whole room easily and it was only on like 5 on the master volume which shows if you have the right acoustics you dont need much power at all :) (even when I turn the gain channel on its only on about 4) here you can see the proper size of the building Link to comment Share on other sites More sharing options...
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