The Relationship between Solid State Wattage and Perceived Volume

jaymenon

To my knowledge (at least with tube amps) one needs to multiply the wattage by 10 in order to effect a doubling of the perceived volume.

And therefore:
A 100 watt amp is twice as loud as a 10 watt amp
A 10 watt amp is twice as loud as a 1 watt amp
(even a 1w amp has 25% of the volume of a 100W amp)

With a solid state bass amp: 
300W RMS @ 8ohm
500W RMS @ 4ohm

So when you connect a second 8Ω cab in parallel - does that make it significantly louder?

Funkfingers

These rules of thumb take no account of loudspeaker efficiency and cabinet design. 

What definitely does change is that additional loudspeakers shift additional air. 

fretmeister

More air and better spread - especially if you stack upwards rather than sideways.

Non-directional freqs also seem to increase in comparison to the highs too. When I add another identical cab and then lower the volume a touch to be the same as it was I seem to need to trim some low end off to stop the boom.

jaymenon

Funkfingers said:

These rules of thumb take no account of loudspeaker efficiency and cabinet design. 

What definitely does change is that additional loudspeakers shift additional air. 

Actually they do, since the loudspeaker and cabinet remain constant. Only the amplifier changes...

jaymenon

fretmeister said:

More air and better spread - especially if you stack upwards rather than sideways.

Non-directional freqs also seem to increase in comparison to the highs too. When I add another identical cab and then lower the volume a touch to be the same as it was I seem to need to trim some low end off to stop the boom.

That's very interesting.  'Lower the volume a touch to be same as it was'

From that I infer that when you add the second cab, the volume doesn't increase spectacularly / significantly (i.e. you don't find yourself reducing the volume control to 50% or 60% of what it was before).

This is after adding another cab which
1. Halves the speaker impedance
2. Increases power from 300W to 500W

But the sound is 'bigger' nonetheless (a little louder, more spread, a little more low end)

Thanks fretmeister - that's very useful to know.

ICBM

jaymenon said:

So when you connect a second 8Ω cab in parallel - does that make it significantly louder?

Yes.



I should clarify probably .

Yes, in my experience it significantly increases the volume because it not only gives about a 2dB increase from the extra power, there's about a 2dB increase in speaker efficiency from using twice as many (assuming of the same type), and most importantly of all it just shifts more air... which may not be obvious when you're standing right in front of the amp, but it fills the room far more.

The dB figures don't tell the whole story. Yes, it's true that a 3dB increase (the same as doubling the amp power) is not all that dramatic in isolation, but it is in a band mix. And a difference of 10dB is enormous - the 'doubling perceived loudness' is again in isolation - it can make pretty much the difference between an instrument being inaudible and everything else being inaudible.

jaymenon

I remember connecting an extra pair of PA speakers to a solid state stereo power amp (reducing impedance from 8 ohms down to 4 ohms) and being struck by how little the volume actually increased...

Musicwolf

Hi Jay

Probably a question best posed to Hugh over at 'the other place' but, for what it's worth;

All other factors being equal, single cab etc then doubling the power = +3dB, 10 times power = +10dB.  It's broadly recognised that somewhere between +6dB and +10db will be perceived as a doubling in loudness (I think +10dB is the more accepted number).

When working with powered PA cabs the assumption is that two equal cabs are +3db louder than a single cab (in line with the numbers above), so little additional volume, however the spread is much greater.

stubmandrel

It depends a lot on the cab. If it's the same as the existing cab then as worked out above it will increase volume by about 4dB, but it may also improve the perception of the low end, and also help you hear yourself as more mids will be coming out nearer ear level.

If it's a different cab, then things may well be different. For a start the extra cab may be more or less efficient than the existing one. A low efficiency cab may make very little difference, a higher effciency one may make it a lot louder.

I added a 15" cab to my TE 4x10 combo, this is more to do with extending the frequency range down than looking for more volume (in which case a second 4x10 would have been more effective).

prowla

What's a Watt?

I don't know if anybody can quantify the relationship between amplifier power rating and volume to the listener.

There's the saying that valve Watts are louder than tranny Watts.

We've also got RMS/music power/peak whatever.

And the frequency response of a cab must surely come into play.

Perhaps an amp which favours one cab may not be so great through another.

Are the Orange Isobarik cabs louder than normal ones?

Are two amps through two cabs louder than one amp through those same two cabs?

Speaker size.

Lots more questions than answers for me...

ICBM

prowla said:

What's a Watt?

I don't know if anybody can quantify the relationship between amplifier power rating and volume to the listener.

There's the saying that valve Watts are louder than tranny Watts.

We've also got RMS/music power/peak whatever.

And the frequency response of a cab must surely come into play.

Perhaps an amp which favours one cab may not be so great through another.

Are the Orange Isobarik cabs louder than normal ones?

Are two amps through two cabs louder than one amp through those same two cabs?

Speaker size.

Lots more questions than answers for me...

That is all important, but in my opinion if an amp is claimed to be rated at 'x' watts, then it should be capable of producing that amount of power, continuously, indefinitely, with a 1KHz or other specified frequency sinewave signal at a specified (very low, usually 1% or less) THD into a dummy load of the rated impedance. Anything else is just bullshit by numbers, really.

It is certainly true that a lot of other factors affect the perceived volume that it can produce, but unless you start with that basically level playing field then you might as well just make it all up.

Measured like that, there is actually no difference between the amount of power put out by different technologies if they are specified to be the same. Understanding why that doesn't translate into the same real-world volume is the next step, and then you can start to work out roughly what the differences will be.

PaulWarning

A manufacturer's stated output watts have to be taken with a pinch of salt, for instance Trace Elliot amps are accepted to be louder than most others, my 200 watt Trace Elliot is noticeable louder than an Ashdown 500 ABM EVO III for example.
The only true test is to try them while playing in a band situation.

ICBM

PaulWarning said:

A manufacturer's stated output watts have to be taken with a pinch of salt, for instance Trace Elliot amps are accepted to be louder than most others, my 200 watt Trace Elliot is noticeable louder than an Ashdown 500 ABM EVO III for example.
The only true test is to try them while playing in a band situation.

I found exactly that too. The older Traces have huge transformers and power supply caps by comparison with the Ashdowns so they can deliver much higher power transients, which is where the perception of volume mostly comes from. The even older ones that weigh as much as a car even more so - caps the size of coffee mugs, and huge transformers to match. The MkV AH250 I had was monumentally loud, much more so than the Series 6 AH200 that I replaced it with when I got fed up of carrying it - but they really were 250W and 200W if measured.

Actually if you think about it there may almost be a direct correlation between weight and volume...

Funkfingers

“Soild state”? Shitty, huh?