If I run my 50 watt head on 3, can I use a 50 watt speaker?

Discussion in 'Amps and Cabs' started by soldano16, Jan 14, 2008.


  1. soldano16

    soldano16 Member

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    I've heard the golden rule is it's best to have the speakers capable of handling 2X the amp wattage so a sigble 100 watt speaker is best for a 50 watt amp.

    But if you never really drive the amp, can you use a lower wattage speaker? How risky is a 50 watter speaker with a 50 watt amp if you don't have the volume over 3?
     
  2. rockon1

    rockon1 Member

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    It will probably be OK.. Honestly the worst that will happen is you might blow the speaker if you crank it too much so just be careful. I guess I dont sweat things like that too much. It would just give me an excuse to buy another speaker! ;)Bob
     
  3. Fixxxer

    Fixxxer Member

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    2 x's what the amp can push out? WOW, I have not been doing that.
     
  4. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    Download this: http://southbayampworks.com/marshallmanual/jcm800specs.pdf

    Go to page 5 of the PDF (page 6 of the manual) and look at the 1987 specs CLOSELY for output wattage for a dual EL 34 solid state rectified Marshall.

    Then you'll understand why you need 2X the speaker power handling. 3% distortion is around 3-4 on the volume knob, 10% is around 6-7, past that and you're out of volume, just adding a tiny bit more gain/distortion.
     
  5. GCDEF

    GCDEF Supporting Member

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    Your amp may still be putting out its full power with the volume on 3. I wouldn't try it.
     
  6. Sean French

    Sean French Supporting Member

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    Been there,done that.
    You will need a 100 watt or higher speaker.
     
  7. Melodic Dreamer

    Melodic Dreamer Member

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    I've always heard the same rule as well. BUT!!, How do so many people who play a 100watt head play through either a 2x12 with v30's or a 4x12 with v30's? That just adds up to 60 or 120 watts. Thats defintaly not twice or even close to 200 watts.
     
  8. John Phillips

    John Phillips Member

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    There is no right answer. It totally depends on what 50W amp and what 50W speaker.

    Some amp companies claim 50W for amps which don't even reach that (clean), and some call an amp '50W' that can approach 70W clean and over 100W fully distorted.

    Some speaker manufacturers rate their speakers on the actual electrical power they will take, others more on what a cranked amp of the speaker's rated power will produce (which is a lot higher).

    There are some 50W amps that are perfectly safe with some 50W speakers, and other 50W amps will almost certainly blow other 50W speakers.

    Where the amp is set on the controls is almost meaningless too. Some amps - eg early-70s 50W Marshalls, which are also some of those that put out far more than the rated power - reach full clean power before halfway on the volume controls with a loud guitar, so saying that the amp will only be turned up to 3 may mean it's actually producing 50W at that point.

    2:1 handling to output power ratio or more does make it very unlikely that the amp can blow the speaker, but I don't generally find you need as much margin as that normally - but it doesn't hurt.
     
  9. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    Another factor is that while some amps claim to be 50 watts, they don't put out that much due to what state of health they're in. They could put out less or more, based on:

    1) Tube life/type installed
    2) Preamp tubes used/changed
    3) Internal circuitry changes
    4) Output & power tranny changes
    5) Any number of other factors

    I always recommend players get their amps tested for actual output. As my online colleague John Phillips has stated, some 50 watt amps put out 70 watts clean, or well in excess of their rating (as the JCM 800 manual I linked to shows). Old Plexis were another culprit of conservative wattage ratings, and I find some of these older amps can actually dial in their full wattage before 4 on the volume knob setting, then you just add gain.

    To be fair, I can only give you a range to work with, since there are so many amps, volume pot taper changes, plus all of the other possibilities. The thing to do would be to have your tech measure YOUR AMP for it's actual output in all the volume ranges you use.

    For example, my Major Crunch amp (quad 6V6, single ended Class A) puts out 19.8 watts RMS at 2 on the volume knob. The amp keeps getting louder, in a more linear type fashion, all the way up to 11 (yes my knobs go to 11). At 6-7 the Major puts out 33 watts, around 11 it puts out 40 or so. As you can see, most of the clean wattage rating comes in quickly, then there are incremental upgrades in volume (and gain/distortion) as you twist the knob to the left.

    If I use one 30 watt H75 speaker with my Major Crunch, I don't turn it up past 7-8, tops (besides, it's screaming tone like a stack at that volume so who needs more?). I prefer to use two 30 watters with it for the wider beam of speaker volume dispersal, and so I don't run the H75 30 watter at it's absolute limits.

    Now, I've also bought hundreds of Celestions. Typically when I bought a G12H30 quad, date code matched, all from the same cabinet with a guy using a 100 watt 72 Marshall, with an OD pedal in front, there were one or two that were OK, but the rest were blown, damaged, or needing a recone cuz they had been beat to death.

    So, it's up to you how you want to treat your speakers. I've had clients buy speakers from me, knowing they were running them on the ragged edge ON PURPOSE, and just expected to blow them after awhile (6 months, 2 years, whatever the "awhile" timeframe was to them) cuz they liked that tone.

    It's all up to you, your idea of tone, and your wallet.
     
  10. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    A 2:1 power handling rule is what Marshall used in the 60's though. You bought a 100 watt Plexi, you bought two 100 watt cabinets with it (referred to as a stack). Or at least that's how they were sold & recommended.

    The 1/2 stack theory only came into being when they got higher power handling speakers in the late 70's with the introduction of the 50 watt G12H's and G12-65's.
     
  11. soldano16

    soldano16 Member

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    Amazing replies guys - thanks for making such an effort.

    The speaker is for a 1X12 cab that will have a 16 ohm speaker and it will have either my 68 50 watt plexi or 63 non TB AC-30 head into it. I really won't be using this in loud situations at all - no gigs. I have other cabs. This would be for recreational jams where the volumes are low but still with a drummer.

    Id love to go with the new Celestion gold at 50 watts. I think I'll be OK because I know I don't play that loud, not loud enough to blow a 50 watt speaker. I used an all original 69 Vibrolux Reverb for 2 years and the guy I sold it to blew out the original Oxfords within weeks.
     
  12. John Phillips

    John Phillips Member

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    Not quite... the half-stack actually came first - but for the JTM45 and JTM50 ;). By the time they got up to 50W amps they were still using 20W speakers, so that's not 2:1, although it's better than 50% safety margin.

    The full stacks were designed to go with the 100W amps, yes - because initially one cab would definitely not handle the amp - but once they started using G12H-25s (you know that's not a typo, but for anyone else reading, it isn't!) and calling them 'Heavy Duty' Model 1982 cabs, they started putting '100' badges on the front because they were theoretically supposed to be able to handle a 100W amp, although two cabs were still recommended. (I think the catalogs said something about 'improved sound dispersion', but it may have just been code for 'improved power dissipation' :).)

    The problem - even when they went to G12H-30s - is that the amps weren't 100W, they were more like 130W and sometimes 140W even clean, and far in excess of 200W when fully distorted. And I know I think G12H-30s are pretty tough, but four of them won't take that amount of punishment safely.

    It is amazing that Orange used a pair in the 80W combos - but also to be fair, those amps don't quite put out 80W, not true clean power anyway.

    The really odd thing is that you can do all the calculation you like and sometimes it just depends on the player.

    I know of people who have used 100W amps into 80W speakers and not blown them - and not held back on the volume either - and I know a guy who seemed to be able to blow any speaker in any amp - much like SRV was apparently able to do, and maybe not coincidentally they had a similar playing style. This guy blew a 65W McKenzie speaker in a Fender Deluxe Reverb - which cannot put out more than about 45W even fully-distorted with a Tube Screamer into it. It shouldn't have been possible...
     
  13. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    Right you are, I forgot about the early JTM 45's and such. One 80 watt cab would have been the norm for those, but a JTM 45 only put out 33-35 watts clean and around 55-60 dimed, right? That was the norm for a tube rectified JTM, IIRC, but not the solid state rectified models (they put out way more).

    As for the speaker power rating, I had my first amp client buy a G12-65 for his original Scumbag (dual 6V6, single ended Class A amp) amp. 10 watts clean, 20 dimed. The G12-65 used a Celestion recone kit in it. So you'd think "No problem!"...right?

    13 months later, less than 30 days after the recone warranty ran out the G12-65 blew. That's right. It went open circuit, toasted a resistor on a power tube when it died, too.

    The client immediately bought an extension cab and a Dr. Z Airbrake for his amp...and got TWO Pre Rola G12H30's from me to make sure he was good to go.

    So, 60 watts of Pre Rola tone in a little Scumstack has worked for him for the last 3 + years. LOL

    Now that I think about it, maybe the newer speakers don't have the power of the old ones, John. But I've seen/bought so many of those that were blown that I always err on the side of caution...and anti-wallet emptying (and speaker blowing/frying) conduct. :)
     
  14. John Phillips

    John Phillips Member

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    I agree totally really - especially since a blowing speaker is one of the most serious hazards there is to an amp's OT and tubes - I just don't think that you need to be quite as conservative as 2:1 usually... not with Celestions, anyway. They do seem to be far more robust than other makes, in my experience and that of many other players in the UK - that's I think the main reason (rather than tone alone) why they became the 'classic' speaker. Fanes sound great too... but blow far too easily relative to their rated power. I've also seen a lot of dead Eminences, far more than I would expect if the ratings were anything like as conservative.

    But if an amp putting out 20W fully cranked blew a 65W speaker (any make), there was some other factor... maybe just a faulty coil, or the same kind of SRV player :).

    The very first Marshalls used the 15W Alnico G12, and they certainly did have problems with them in the early Bluesbreaker combos - that's apparently why they switched immediately to the ceramic G12M-20 when it became available. No surprise, because although the JTM45 is no more powerful clean than an AC30 (where they seem to survive well enough), it is when distorted. The AC30's cathode bias makes it much more compressed and less hard on the speakers when it's pushed into distortion, and the maximum power is quite a lot lower than in a JTM45. The JTM45's power stage isn't even distorting when the amp clips first - that happens in the PI, or the tone stack driver depending on settings - so there's a lot more potential maximum power.

    In other words, you can't always tell just by power ratings either...
     
  15. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    And that is why guitarists should take their amps to be tested for power wattage output. At least you have a good starting point to test from.
     
  16. John Phillips

    John Phillips Member

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    Agreed, and it's the maximum fully distorted power output which is critical, not the clean power. The speaker can't actually tell, it's all just electrical energy.

    The next problem is: how do you measure power output? Single frequency (and if so what), or a balance of frequencies (with what distribution)? Into a resistive load of the nominal impedance, or into an inductive load that better simulates a real speaker loading? The difference between some of these methods could easily be a factor of two.

    In fact, I use the crudest and least 'scientific' method - guitar into amp into inductive attenuator, and thrash the hell out of it :) - precisely because it is the closest to the real conditions with a normal speaker load, both for making sure the amp is working properly and comparing power outputs. I'm not under any illusions that it's the 'true' power output of the amp, but I always use the same method and equipment so I know that I'm comparing like with like.
     

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