More speakers = Louder?

[fr0sty]

How about instead of debating the theory, which is interesting, someone do a "Pepsi challenge"?

 

Get an amp and several cabs, don't let the listeners know what speaker configuration they are hearing, then ask them which they perceive to be louder. Even if it is against the laws of of physics, nature and/or god for a 4x12 to be louder than a 2x12 of the same speakers through the same amp, the listener's perception is important in this case.

 

This evidence should not be used in a court of law, where it is widely known that human perception is dubious.

[GCDEF]

 

Originally posted by guitarzan You sir, are dead wrong. The power is divided but as everyone should know, half power of 100 watts makes little difference in volume. Breaking down the power between speakers will effectively move more air, as long as there is enough power to cover the needs of each additional speaker. However, placing a mic in front of your 1x12 for gigs beats carrying around a 4x12 or two. I doubt too many pros would NOT allow the sound guy control over the mix. The mix should be more important than guitar volume, unless you are just raising hell in your bedroom. Peace out.

 

 

Why do people with no clue post as if they know what they're talking about? I don't get it.

 

Please define the "needs of each individual speaker". Just how much power does a speaker "need"? Where does the extra energy that you're getting out of the system come from if you're not putting any extra energy in?

[tommythelurker]

You know, I posted a link a while back that is pretty much a definitive answer on this but apparently no one took the time to read it or it was over all your heads

 

All else being equal, two speakers will be 3 dB louder at any point where the waveforms from both are in phase. But other factors will cause the phase to shift anywhere from being in phase and adding up to being 180 deg out of phase and cancelling out. If you take the AVERAGE of this effect, the net result is THE VOLUME IS THE SAME. That's the bottom line. That's physics.

[Al Poulin]

Originally posted by etienne Thanks for confirming this..

 

 

 

A well designed 12'' can move more air than a piece of {censored} 18'' - so size alone does not mean it will move more air.

[tommythelurker]

 

Originally posted by Roccaforte Amps I guess we can all get rid of our 2 12" and 4 12" cabs now since you've proved that a single 10" speaker will produce the same volume and do the same job as 4 of them.

 

No one said they do the same job, in fact many people have pointed out other reasons why adding speakers may be beneficial. But the original question is about how the number of speakers alone affects the volume, and all else being equal it doesn't. If you start adding in other variables, of course things can change. As I see it, this is really the source of most of the dissagreement here, people are making different assumptions.

[GCDEF]

Originally posted by Roccaforte Amps Originally posted by GCDEF So, be scared all you want. I guess we can all get rid of our 2 12" and 4 12" cabs now since you've proved that a single 10" speaker will produce the same volume and do the same job as 4 of them. (Goodbye bass response.) Doug Ps, One of Weber's books (Hip hop reference) even tells a story why Fender went from a single 15" speaker in the tweed bassman up to 4 ten inch speakers.Go ahead and read it, then say him and fender are nuts too.   I never said they'll do the same job. Obviously a 4 x 12 will handle more power than a 1 x 12. Not many 1 x 12s will handle the amps you build. Nobody's said they'll have the same frequency response either. All that has been said is that unless a speaker is reaching the point where it's not capable of getting any louder, adding another won't add volume.

[Dr Wanker]

Originally posted by Armitage Wow you guys are scary.... If you go from one 2x12 cab to two 2x12 cabs your first thought may be... "more speakers will be louder"... then you'll think about it a bit more, then think "hey, it's the same amount of power, just spread around more, so it'll be the same" then if you really think about it... "because speakers aren't a linear device... actually efficiency goes down with more power, it actually IS a BIT louder and spread out more to boot." BTW, Volume is based on how much air is moving... it doesn't matter if it's a big diameter speaker or a speaker that moves in and out farther, it's how much air is being moved. So a big speaker that moves in and out the farthest (at a given power) is the loudest.

 

Well put.

[GCDEF]

 

Originally posted by Roccaforte Amps But wait, isn't a better frequency response going to be louder? So, you see how 4 10's will produce a better bass response over a single 10, maybe I'm wrong here, but I know I can hear it as louder.

 

 

But that's not the point of this discussion. 12's will usually have a better bass response, but that's irrelevant. They may be louder in the lower frequencies and not as loud in the highs. Notice I said MAY be. It'll depend on the speaker too.

 

This discussion is whether simply adding a speaker will increase volume with no other changes. You have 1 12 " speaker being fed 1 watt of sound. It produces 100dB. If you add another speaker and make no other changes, does it stay 100dB or increase to 103? The answer is, it stays the same.

 

Each speaker is now getting half a watt. We know that when you decrease power by 1/2 you lose 3dB. So instead of one speaker putting out 100dB, you have two putting out 97. The net result is still 100dB. This is really basic audio engineering stuff.

[tommythelurker]

I think what Doug is pointing out is that if you put two speakers close together, the lower frequencies will be in phase so the bass will be a bit louder (up to +3dB). I think this is what other people have been refering to as coupling. Average that out over the entire spectrum and the net increase on SPL is somewhat less than 3dB, but there is something.

 

Could be argued that this is adding another variable, but when we add speakers in a guitar rig this is typically how we do it so he may have a point.

[agedhorse]

Air moved is the cone area x piston displacement. Displacement (in the linear reigon) is proportioinal to power.

 

So, for the same power divided into 2 identical speakers will reduce in (2 x area) x (1/2 x displacement) = identical air moved as 2 x 1/2 = 1.

 

There is one benefit I mentioned, to increasing the number of speakers given the same total power (provided the tradeoffs in comb filtering are acceptable). That is the effect of active baffle extension due to adjacent speakers acting to alter the loading on each other which appears to the speakers as though they are mounted on a larget baffle. This "coupling" may extend the low frequency response by a few Hz at the expense of the comb filterinmg and possible losses above this point due to cancellations of multiple sources.

 

Another benefit that Boseengineer and I mentioned is using multiple drivers as a line array, intentionally altering the polar response in order to decrease dispersioin in one plane in order to reinforce (and increase) in the other plane. This can be further modified by active electronics (fractional delays) driving speakers farther out along the array to perform beam forming and steering. It will increase the sensitivity greatly, but the net radiated efficiency does not increase significantly.

[ambient]

could someone please explain the concept of 'coupleing' for the lamens browsing this thred.

[Jack Luminous]

 

Originally posted by guitarzan You sir, are dead wrong. The power is divided but as everyone should know, half power of 100 watts makes little difference in volume. Breaking down the power between speakers will effectively move more air, as long as there is enough power to cover the needs of each additional speaker.

 

 

Nope, because excursion (or piston displacement, see Agedhorse post above) of each speaker will be less so no more air will be moved.

 

 

Originally posted by tommythelurker All else being equal, two speakers will be 3 dB louder at any point where the waveforms from both are in phase.

 

 

Nope, for the same reason above. Excursion of each speaker will be less since the same power is distributed to more speakers. Each speaker will move less. So there will be no increase in dB.

[vize84]

I read this interesting thread and I want to add what I know.

There's a physics law that says that when you double the sound source (for example you use 2 identical amplifier each one connected to its speaker) you've got an increase of 6 dB SPL.

When you use a single amplifier, its power is divided between the number of speakers so every time you double the number of speaker the SPL of each speaker is lowered by 3 dB, but you've got to add the 6 dB since you also double the sound source.

So at the end you've should have an increase of 3 dB (-3 dB + 6 dB) every time you double the number of speaker.

[lndianScout]

lots of good info here

 

http://www.santafevisions.com/csf/html/lectures/003_sound_II.htm

[GCDEF]

 

I read this interesting thread and I want to add what I know. There's a physics law that says that when you double the sound source (for example you use 2 identical amplifier each one connected to its speaker) you've got an increase of 6 dB SPL .

 

 

Doubling power = 3dB, not 6.

[tlbonehead]

Originally posted by GCDEF Doug, that's just plain wrong. You're NOT moving more air with 4 speakers than with 2. The excursion of each speaker is reduced and so is the air that's moved. And 15" speakers don't necessarily produce more volume than 10"s. That's just a nutty thing for a reputable amp manufacturer to say. Scary even. So, be scared all you want. I guess we can all get rid of our 2 12" and 4 12" cabs now since you've proved that a single 10" speaker will produce the same volume and do the same job as 4 of them. (Goodbye bass response.) Doug Ps, One of Weber's books (Hip hop reference) even tells a story why Fender went from a single 15" speaker in the tweed bassman up to 4 ten inch speakers.Go ahead and read it, then say him and fender are nuts too.

Well, you still have to do the math. Its all about moving air for bass response. So you'd have to figure out the cone area of the different speakers x the actual movement of the cone. A 10" driver with a superlong Xmax can move as much air as a larger cone that has a shorter cone/VC travel.

[tlbonehead]

 

could someone please explain the concept of 'coupleing' for the lamens browsing this thred.

 

More than one cone acting together with the air to create one larger sound field. It is usually more pronounced in the lower frequencies.

[tlbonehead]

Doubling power = 3dB, not 6.

When I saw the title of this post, I somehow knew I'd find you and TL in here trying to talk sense!

[duncan]

I never play with less than 6 x 12. Once you've A/B'd with a smaller setup, there's no turning back.

 

truth.

 

although now i play through 2 100 watt heads, each into their own 4x12, respectively.

[GCDEF]

When I saw the title of this post, I somehow knew I'd find you and TL in here trying to talk sense!

 

Doesn't seem to do any good though. It's an old thread. Hopefully it will die again.

[Mood Bender]

for the same power...

 

with more speaker's, each speaker will be handling less power... thus each speaker will output less volume

 

but...

 

with the additional speakers the coupling to air is much greater, thus more volume overall.

[vize84]

 

Doubling power = 3dB, not 6.

 

 

Doubling sources of sound is different than doubling the power. When you double the sources you double the sound pressure, when you double the power you get an increase of only 1.414 in sound pressure

 

What says Mood Bender is right

[echodeluxe]

in response to the original question:

 

ALWAYS

[vize84]

Another interesting fact I noticed are the technical details of MARKBASS cabinets.

The sensitivity for the version with more speaker is always higher than models with less speaker.

Example: 102HF (2 spk) : 101 dB, 104HF (4 spk) : 103 dB, 106HF (6 spk) : 104 dB.

It seems that doubling the numer of speaker give more or less a 2 dB increase (in theory shoud be: -3+6=3 dB but heare come problems related to cabinet physics and structure that can "delete" some sound waves and so the gain is a little lower)

[Rodimus Prime]

adding speakers to the same amp is not physically louder in terms of db rating, it just fills more air.

I was touring around with a worship team and the leader of the group was very db sensitive and we brought a meter to every show and aimed to keep shows from 92-95 db's. At the time i used a fender deville 4x10 and an avatar 2x12 on stage and he asked if the speaker cab added to the stage db level. We used the meter to see if the extra 2x12 was physically louder and it was not at all. It was exactly the same with as it was without.