watts, speakers size and loudness... (1 Viewer)

[JohnnyRaz]

can someone give me some sort of explaination of all of this malarkey;

i know the watts/loudness relationship isnt linear, and in particular tube amps=louder than solid state amps.

but where does speaker size come into it; is a 10watt amp driving a 12 inch speaker effectively as loud as a 20watt amp driving same speaker, but with less clean volume??

 

[PaoloJM]

can someone give me some sort of explaination of all of this malarkey;

i know the watts/loudness relationship isnt linear, and in particular tube amps=louder than solid state amps.

but where does speaker size come into it; is a 10watt amp driving a 12 inch speaker effectively as loud as a 20watt amp driving same speaker, but with less clean volume??

Tube/valve watts are not louder than SS watts. The problem here arrises from the fact that there is no strict definition of watts in a valve amp. One manufacturer may call their amp 30Watts (@ 1% THD), the next manufacturer could call their, otherwise identical amp, 50Watts (@ 10% THD). THD = Total Harmonic Distortion btw. Neither manufacturer is wrong or incorrect. They are simply measuring power at different levels of signal distortion. The marketing guys will tend to opt for what will sell the amp better, and unfortunaley bigger is better. SS technology does not allow for such loose definitions.

On speakers:
Roughly speaking larger diameter speakers are more capable of pushing out bass frequencies than smaller ones.
The other critical factor in speakers is their sensitivty rating. Your 50 Watt Marshall will sound louder through 2 V30s (100dB) than through 2 Greenbacks (96/7dB). Both are 12" Celestions, and both options would be capable of handling the 50 Watts. One will be louder than the other though, all other things being equal. This is due to construction of the specific speaker eg the cone material, spider contruction etc.etc.etc.
You will find the sensitivity rating printed on any speaker data sheet.

 

[JohnnyRaz]

thanks

so its a case that tube amps tend to be under rated power wise??

still dont understand the effective difference between two similar speakers being driven by amps of different wattage, does the higher wattage amp give you more volume, or just more clean volume?

or am i and idiot and youve answered this already!

 

[PaoloJM]

thanks

so its a case that tube amps tend to be under rated power wise??

still dont understand the effective difference between two similar speakers being driven by amps of different wattage, does the higher wattage amp give you more volume, or just more clean volume?

or am i and idiot and youve answered this already!

Strictly speaking tube/valve amps are generally over-rated.
SS power sound absolutley aweful when driven into clipping/overdrive. Their power ratings are given at low THD, usually around .1% I think, and it's not possible to drive them beyond this.
Historically valve amps have been allowed to quote higher power ratings because they sound pleasant when driven into clipping, even for HiFi. We all know that they sound f*kin great when pushed even harder and most valve guitar amps are designed to let you do this. This means your 50 Watt Marshall is capable of delivering up to 75 maybe 80 Watts and sound f**kin great but strictly speaking it can only deliver maybe 30 Watts at the .1% THD that SS amps are rated at.
Remeber we are discussing the power amp here, the preamp or effects is not relevent to power ratings.

Back to speakers: A power rating of an amp is just that; it's a measure of the amps ability to deliver power.
The speakers role is to turn that power into audible sound which is meausred in dB. The dB rating is a measure of the sound level a speaker is capable of creating at a distance of one meter when given an amp signal of one watt.
In my example above the V30 can create 100dB of audible volume if you gave it one watt from your amp, the greenback could only give 97dB with the same one watt.

Think of an energy saver bulb. The energy saver is more efficient that an incandecent bulb. An energy saver produce the same light intesity as a 100 Watt incandecent bulb using only 16 watts (I think that's it, but I may be slightly out on the actual numbers).

Hopefully you see that it's very hard to answer your question directly. A 50 Watt JCM 800 will not be as loud as a 100 Watt JCM 800 when played through the exact same cab. But you can't compare different valve amp brands or even ranges from the same brand in this way, nor can you compare valve amps with SS directly.

I've spent a long time studying and thinking about these things (as you can tell) and I've have come back to one conclusion: Plug the amp in, if it's loud enough to keep up the drummer it's f*ckin' loud enough and I don't give a f*ck what wattage the amp is as long as it sounds good 'cos I know the wattage means nothing really anyway.

 

[Space]

Just to add: more speakers generally means more volume and double the wattage only equals a few more dBs of volume.

 

[JohnnyRaz]

plug the amp in, if it's loud enough to keep up the drummer it's f*ckin' loud enough and I don't give a f*ck what wattage the amp is as long as it sounds good 'cos I know the wattage means nothing really anyway.

sound advice indeed! thanks...

you should have your own thread; ask paolo!!

 

[sparse]

more speakers generally means more volume

is this correct? I thought it was just spread over more speakers so 2 speakers work harder than 4 because they're both receiving the same amount of power!?

Also a side question, does a 4ohm matched head and cab sound different to a 8 or 16ohm matched head and cab!?

 

[Red_Dog]

Watt?

 

[Space]

is this correct? I thought it was just spread over more speakers so 2 speakers work harder than 4 because they're both receiving the same amount of power!?

Also a side question, does a 4ohm matched head and cab sound different to a 8 or 16ohm matched head and cab!?

It's correct for percieved volume, more air being moved and all that. Put a 4x12 beside two 4x12s and compare them with the same volume on the head.

Pretty sure it makes no difference on what the matched resistance is as long as it's matched.

 

[PaoloJM]

Watt?

Hey hey, someone had to!!

Moose/Sparse, you're both right. More speakers is not actually technically louder, a SPL meter will give the same reading, but it will feel louder/fuller as a wider surface area is pushing the air. An angled 4 X 12 will seem louder too, as the angled speakers are pointing directly at you when you're standing in front of it.

There should be no difference if tone from the amp when using the 4, 8 or 16 ohm connection assuming the cab is matched accordingly. However a 4 ohm 4 X 12s' speakers are usually wired in parallel and will have a slighly lower resonant frequency the a 16 ohm 4 X 12 which is wired is series parallel. I've tried it and it's not a big difference, nothing you wouldn't dial out with EQ.

I think you can waste a lot of valuable geetaring time by worrying over these things, best just to dial in a good tone and get cracking!!

 

[Space]

Yeah should have said perceived volume in the first post. It's great how the guitars and amps board is getting all nerdy recently.

 

[PaoloJM]

Yeah should have said perceived volume in the first post. It's great how the guitars and amps board is getting all nerdy recently.

That's probably my fault. It's ok, I'll shut up now I promise.

 

[Space]

Nah I love it. Been refreshing my electronics knowledge a lot recently, studied it about 10 years ago and suprisingly it's still in there somewhere. Applying it to guitar stuff now which is the fun part.