Wattage question

[pastorofmuppets]

Ok, now if I'm correct wattage has nothing to do with volume really, just kind of a way for newbies to find a estimate at what the volume of their amp really is. Now my question is, if wattage doesn't mean volume and decibals does, then is there a way to tell exactly how loud an amp is without saying "loud, really loud, very loud, or quiet" or without turning it up all the way and putting your ear against the grill?
I was thinking about buying a decibal meter and cranking every amp I can find with different wattage's to see what 100 watts is and 60 watts ...
I know it's not really a big deal but I would just really like to know so I don't have to look at watts and think that's loud, I can just know exactly how loud.
Thanks

 

[ramalam]

There is a definite correlation of watts to loudness. It just isn't proportional on a 1 to 1 basis. You need 10 X the amount of watts to get double the loudness. Watts are still a very good indicator of loudness but speaker efficiency differences can also make a 50 watt amp with an efficient speaker sound louder than a 100 watt amp with an inefficient speaker. Put an efficient speaker like an old JBL D120 in a Boogie Studio .22, for instance and prepare to blow the doors of many a 50 or 75 watt amp. Still and all, the best practical guide is your own ears.

 

[pastorofmuppets]

So say a 100 watt Marshall SLP with four Vintage 30's and the 50 watt version (the 1987 thing) with the same setup, the 100 watt should be twice as loud right? I also want to know if the head is tube 100 watts (not sure if tube matters), will it blow speakers if they are under 100 watts each if you crank the amp as loud as it can go? I'm pretty new to the technical side of this stuff so thanks for your patience.

 

[AustinK]

100 watts is not twice as loud as 50. It is just a little louder.

 

[ramalam]

So say a 100 watt Marshall SLP with four Vintage 30's and the 50 watt version (the 1987 thing) with the same setup, the 100 watt should be twice as loud right? I also want to know if the head is tube 100 watts (not sure if tube matters), will it blow speakers if they are under 100 watts each if you crank the amp as loud as it can go? I'm pretty new to the technical side of this stuff so thanks for your patience.

I am not really familiar with those amps specifically, but long story shore, if all things are equal, a 50 watt amp is more than 80% as loud as a 100 watt amp.

The rule of thumb for sizing speakers is to use ones with a total that is about twice the watt rating of the amp's. This is because watts are generally rated in "clean" output, where when fully cranked and "dirty" it can sometimes approach double that. BTW, at least in my experience, amps rarely sound their best when fully cranked. Somewhere between about 50 and 80% seems best for most amps. Beyond that they are not usually much louder and they tend to get very mushy sounding and no longer have much string definition.

 

[phyrexia]

Speaker efficiency is why a 100w Mark I Combo can outshine a 100w Marshall on a 4x12.

 

[boola]

Yeah, the 100W does not sound a lot louder than the 50W. It just has more headroom before the power valves really start breaking up.

Another thing is that 100W doesnt' = 100W in a different amp. My Marshall 2203 is the loudest 100W you've ever come across, it makes my house shake on 2 - which is nice : ) but to get the power amp distorting you need to go to 4 which is weapon of mass destruction volume! No modern marshall or any other amp I've heard comes close in terms of voume - its all about the transformers.

My mark iv is also pretty loud for 85w. It's loud on tweed and class A ~ 15W! Speaker efficiency, class A, class A/B all play a part. The only way to measure it is to try them out - same as always!

You do need much higher rated speaker for a valve amp. 100W speaker will not be able to handle a cranked 100W amp on the lead channel.

 

[ramalam]

I agree with you about the 2203's. That is why I like the 81-83, 50 watt, 2204's so much and it is still loud but more usable.

 

[ramalam]

Speaker efficiency is why a 100w Mark I Combo can outshine a 100w Marshall on a 4x12.

That is unless the Marshall has a quad of EVM or JBL D120s in it. But yah, I was a neighbor and friend of a practice studio owner in S.F. in the mid 80's. I could use the studio and its equipment free as much as I wanted. He had two early JCM 800, 100 watt full stacks that I used many times. It was fun to "outloud" them with my MKIIC+ 60/100 with its EVM.

 

[MrMarkIII]

You need 10 X the amount of watts to get double the loudness.

Read the post above again.
You need 500 watts to be twice as loud as 50 watts. You need TEN Recto heads to be twice as loud as ONE Recto head, all other conditions being equal.
If you want to measure amp A against amp B using a dB meter, you'd best use the same speaker in the same room at the same temperature with the meter the same distance from the speaker in both tests.
Otherwise it's apples and oranges.

 

[phyrexia]

Speaker efficiency is why a 100w Mark I Combo can outshine a 100w Marshall on a 4x12.

That is unless the Marshall has a quad of EVM or JBL D120s in it. But yah, I was a neighbor and friend of a practice studio owner in S.F. in the mid 80's. I could use the studio and its equipment free as much as I wanted. He had two early JCM 800, 100 watt full stacks that I used many times. It was fun to "outloud" them with my MKIIC+ 60/100 with its EVM.

Well, yeah. I would be quite scared of one of those 4x12s. Somebody could demolish buildings with such a beast.

Are D120s similar in sound to 12Ls or are you just using them as an example of a high efficiency 12"?

The purchasing manager at work has(had?) a Mark I combo and he has told me stories of overpowering halfstacks back in the day. Makes me grin like a monkey.

 

[ramalam]

No, JBL D120's don't sound like EVM's they are even more articulate and brighter. They were originally designed to be theater and stereo system speakers. Later "F" models has doped surrounds and wider voice coil gaps. They are too bright for me and I have snipped out the aluminum dust cap on mine and replaced them with paper dust caps to get a really nice and much warmer sound with rolled off highs. They are a very well built, high quality speaker but stock ones lend themselves more to country and jazz in my opinion, though Dicky Betts if famous for using them with his Marshall 50 watt Plexi in Marshall 4 X 12" cabs that are partially open. That is why he is easily as loud as most 100 watt Marshall rigs. JBL D120s are hard to beat if you can pick as cleanly as Paisley though. Unfortunately, they can only handle about 60 watts and original cone kits kits haven't been available for years. Good examples of original (not reconed) orange D120-Fs have sold for $400.00. I only used them as an example of a high efficiency speaker: 103 dB/Meter.

 

[pastorofmuppets]

Thanks for all the help guys.