1 speaker vs 2 speakers

[Glass Snuff]

ZeroCool, listen to Steve - he gets it. And do remember the original statement was "10 times the power for twice the volume".

That was quite a list of links you posted... did you notice that in the first was the stement, "It follows that the determination of the volume (loudness) which is double as loud should not be dogmatically defined." ?

[ZeroCool]

ZeroCool, listen to Steve - he gets it.

Of course I'm listening to Steve, he got it right from the start, he said:

So, a doubling of the sound pressure means that both SPL and SWL increase by 6dB.
A doubling of acoustic power means that both SPL and SWL increase by 3dB.

Which is what I said earlier if you scroll up, showing that those rules couldn't possibly hold true if both Sound Power (or Acoustic Power) and Sound Pressure were the same thing, as you proposed. Take it from him, not me.

[Glass Snuff]

Actually, you said:

Doubling the Sound Pressure yields a 6db increase (your violin example)

My violin example would be an increase of sound power equal to +6dB.


To the OP, the simple equation reads like this: If the bartender can't hear people order drinks, you'll not be asked back. So, if you have a drummer who must play loud to 'get his sound', fire him. If you decide to keep Mr. Gorilla Arms, then you'll be happier with a 2x12.

[ZeroCool]

Doubling the Sound Pressure yields a 6db increase (your violin example)

My violin example would be an increase of sound power equal to +6dB..

We are both correct because a 4:1 acoustical power ratio is 6db, corresponding to a 2:1 SPL ratio (remember, you only doubled the SPL by having 4 violinist, you didn't quadruple it, like one would intuitively think)

I admit your violin example was a very good example from the start, I just think it's important to remember, like Steve said, that the DEFINITIONS of Pressure and Power are NOT the same; it's just that before, it sounded to me like you meant to say that Pressure and Power are the same in definition and in what they specifically represent, but maybe that's not what you meant and I misconstrued what you said and if so I apologize.

All in all, as far as the 1x12 vs 2x12 is concerned, more than just worrying about the loudness of a 2x12 cab vs a 1x12, I would place more concern in the way Interference will play a role in the tone and directivity, since I seriously doubt the loudness difference between the two would be the difference between night and day.

[pdf64]

'All in all, as far as the 1x12 vs 2x12 is concerned, more than just worrying about the loudness of a 2x12 cab vs a 1x12, I would place more concern in the way Interference will play a role in the tone and directivity, since I seriously doubt the loudness difference between the two would be the difference between night and day.'

In the real world, all else being equal, my experience is that a 2x12 is appreciably louder than a 1x12.
It actually sounds like more than the theoretical 3dB gain that doubling up the number of drivers provides.
It's up to the OP to decide whether that's desirable.
To go back to an earlier point, the link that GibsonLover put in post #12 has a misleading analysis of the situation IMO (due fixing the voltage driving the speaker array, rather than fixing the power).
This is because tube amps (given a suitable output transformer), can provide the same power to the various speaker arrangements.
Even with amps that produce their rated power at only 1 load impedance, then different speaker impedances are available, so the power output to the speaker/array can be maintained with various array arrangements.
Therefore the 3dB gain of the 2x12 over the 1x12 can be true, irrespective of whether the 2x12 is a series or parallel arrangement.

[mooreamps]

What I can't justify yet is, why would I need 2x12 instead of 1x12 (I used 12" there as generally I find that as standard size). What extra kick a second speaker will give when it comes to basement practice with band or a regular gig? In your opinion guys, will there be any difference amongst 2, going by the usage I mentioned above?

Thank you all in advance.
Best Regards.

OK, how about this....... The big difference when you are gigging ; you place one speaker stage left, and another speaker on stage right. Try it with only a 5 watt amp, and see how much volume it makes.....


-g

[ZeroCool]

In the real world, all else being equal, my experience is that a 2x12 is appreciably louder than a 1x12.It actually sounds like more than the theoretical 3dB gain that doubling up the number of drivers provides.

True, but from my experience, friends of mine that have gone from a 1x12 to a 2x12 or 4x12 have, after the switch, kept their volume knobs at either the same position as before or at less than what it was before, and it's important to mention that this position was nowhere near the max volume. In other words, they could've 'kept up' with the new speaker configuration if they just turned the volume up with their 1x12. In other words, everytime I had a friend switch, especially from a 1x12 to a 4x12, the main factor they always raved about was not the gain in OVERALL loudness, but the new tone-related attributes, like they'll say "I love the way the bass sounds now, it's awesome." But, I'm just speaking of my experiences, everyone has different experiences. I also have to admit that these experiences I'm talking about were always with amps 30W and above; that may be an important factor for why my friends did not have their volume knobs too high, in essence giving them enough headroom to still turn their volume up considerably, so maybe my experiences might not hold true for owners of lower wattage amps (like those SE Class A you see all the time) who may be riding their volume knobs close to max.

This is just my experience, I'm not going to hold that it should be true for everyone, but once the switch is made I would encourage the OP to do an A/B comparison and see if they could've kept up with the gain in apparent loudness of the 2x12 by turning the volume up higher with the 1x12 (assuming there's no considerable loss of headroom), and after that, to examine carefully the reasons of why they might like the 2x12 more, that being, if it has to do more with tone-related attributes than with merely overall loudness.

[Glass Snuff]

Quasi on topic, I found myself thinking about this:

If you have, say, a 30 watt amp, and you play though a 1x12 and a 4x12, set to the same SPL with a meter (1 metre on axis, etc), which will be louder?


Out in the room, in the middle of the crowd or at the back, the 4x12 will be louder. More focus, coupling of the bass, less square of the distance, etc. However, on stage, the 1x12 will sound louder. It will require greater excursion to match the level, and this will induce greater distortion. To our ears, it will sound like it's working harder... sort of making a guitar face.

[raiken]

perhaps one of the most simple concepts for power transformers inside a guitar amp, but it eludes so many. Think of it this way ; for a given input, the 8 ohm tap produces "twice" the output voltage as the 4 ohm tap....


It's just that simple ......


-g

Apparently, it has eluded you, too.

The 8 ohm tap does not produce "twice" the output voltage of the 4 ohm tap, it produces sqrt(2), or 1.4 times the output voltage of the 4 ohm tap. the 16 ohm tap produces twice the output voltage of the 4 ohm tap.

Randall Aiken

[mooreamps]

No, perhaps I was not clear ; measured as when terminated to a loud speaker, not open, and not terminated to a resistor ; as measured on a true rms meter. But "for u", I'll look at that again.

-g

[raiken]

No, perhaps I was not clear ; measured as when terminated to a loud speaker, not open, and not terminated to a resistor ; as measured on a true rms meter. But "for u", I'll look at that again.

-g

It will be the same measured as terminated to anything, as long as it is the correct impedance for the tap. It also doesn't matter whether you measure RMS, peak, or peak-to-peak, the relationship holds, as it is a function of how transformers work.

Randall Aiken

[teemuk]

Someone once said wisely about the speaker cluster theory: If it worked, we could rock stadiums with 1W amplifiers and enough of speakers.

I still haven't witnessed that happening.

Each time you add a speaker to the cluster it will rob it's own share of total power the amplifer produces to drive the speakers and consequently make the other speakers in the cluster behave less efficiently.

---

As for doubling up the perceived loudness: General consensus is that it requires a 10 dB or tenfold increase in output power or sound pressure level. 6 dB increase indeed doubles up the sound pressure but that, however, is not the same thing as doubling up loudness we humans perceive.

[Steve Conner]

Someone once said wisely about the speaker cluster theory: If it worked, we could rock stadiums with 1W amplifiers and enough of speakers.

I still haven't witnessed that happening.

Each time you add a speaker to the cluster it will rob it's own share of total power the amplifer produces to drive the speakers and consequently make the other speakers in the cluster behave less efficiently.

Well, we discussed that. If you're using a tube amp, it's assumed that you adjust the impedance switch to suit the new load, so it delivers the same total power as it did before. Under these conditions the SPL increase is 3dB because of the directivity gain.

A solid-state amp delivers more power as the load gets heavier, so it's more or less delivering constant power per speaker as you add more, and the gain of doubling the speakers is nearer 6dB than 3. Until the amp can't take any more and blows up.

These figures are per doubling of speakers. So going from 1 speaker to 2 gets you 3dB. To get the next 3dB you have to go to 4 speakers, then 8, 16, 32 and so on. You can see that you'll need a lot of speakers to rock the stadium with 1W.

It reminds me of the proverb about the guy who asked the King for one grain of rice on the first square of the chessboard, two on the second, four on the third and so on, and he never did get his (2^64)-1 grains of rice, because there isn't that much rice in the world.

And, you can't do it anyway, because you have to fill the stadium with sound so the whole crowd can hear. Directivity gain can't help you because you need to spread the sound around.

[pdf64]

Something that I'm struggling with, is, why there's the same potential 3dB SPL increase when the noise source is doubled up (ie 2 champs) as when the speakers are doubled with just the same power input (ie 1 champ with 2 speakers connected).
Ok we have to imagine that these Champs have got a 4ohm tap available on their OT.
Assuming 5 watts power, surely 2 speakers with 5 watts inputs each (2 champs) have to be able to generate a higher SPL than the same 2 speakers with only 2.5 watts each (1 champ with 2 speakers)?
But acoustics theory has it that 2 singers/fiddles/champs are 3dB louder than 1.
As per the thrust of teemuk's post, why bother with the other champ amp, when just adding a speaker would get us the same SPL?

[Steve Conner]

Well, you're struggling with the concept because it's wrong.

If you're playing with a wall of combo amps, the SPL goes up 6dB per doubling, not 3.

That's 3dB per doubling of speakers, because of directivity/coupling gain, and 3dB per doubling of electrical input power, because each combo has its own power amp inside.

You only get the directivity gain if the two signals are correlated, so you can get constructive interference between them. Two different guitarists, each playing through his own Champ, are just 3dB louder than either guy on his own, not 6. And same with two singers or fiddles.

And say one amp had a Vintage 30 and the other a Greenback (well assuming those came in 8" ) then even if they were fed with the same guitar, the difference in speaker frequency responses might well be enough to uncorrelate the signals.