Quick quiestion on External Cabnets

[TRex]

If I was to run my Jet city JCA2212 into either a 2x12 or another 1x12 as a extention to the 1x12 in the combo, how much louder would it be?

I hear stories of guys running 5 watters into 4x12 cabs and getting giggible levels, where a 50watt amp would normally be used.

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[Chickenwings]

Re: Quick quiestion on External Cabnets

It wont be much louder because you are sharing the wattage between two speakers- and its twice as much to carry to a gig.
If you really want to make it louder, get a more efficient speaker. This is the secret behind the early boogie amps and how people used to say that a 1x12 combo could be louder than a 4x12.
Something with a big beefy magnet and an efficient voice coil like an eminence wizard, or a swamp thing depending on the kind of flavours you like. You will definitely get you a large extra serving of volume, punch and detail.
Maybe even celestion vintage 30, or an EV too. See what you can find for the right price and with the tones you like.
If you decide to do some research, what you are looking for on the speaker spec. sheet is MAx db (decibels), or max spl@1w (sound pressue levels). A difference of 3db is an appreciable difference to the ear, whereas a 6db increase sounds roughly twice as loud. (ie a 103db speaker will seem twice as loud as a 97db speaker like a greenback).
Different companies will obviously have slight variances in how they test, so eminence ratings might not line up exactly with celestion, but seeing as you already have an eminence speaker, it will be pretty easy. Another pretty damn idiot proof test is simply to look at the size of the magnet. If it has a much bigger chunkier looking magnet than the speaker you have, you can be pretty sure the speaker will be a lot louder.
This is a thread about your amp:
https://forum.seymourduncan.com/showthread.php?240561-Jet-city-Eminence-speakers
and a video:

fwiw, the eminence wizard is appreciably louder than the vintage 30 which the speaker in the video is modelled on.

 

[SlyFoxx]

Re: Quick quiestion on External Cabnets

Given an extension cab of like sensitivity you'd get about 3 more dB....not much. But you would generate a wider sweet spot as the horizontal dispersion increases with more speakers.

I've gigged small venues with 5 watts and two V30's..but that was for my distortion channel. I'd use 30 watts for my clean. (Mesa Lonestar Special)

 

[TRex]

Re: Quick quiestion on External Cabnets

It wont be much louder because you are sharing the wattage between two speakers- and its twice as much to carry to a gig.
If you really want to make it louder, get a more efficient speaker. This is the secret behind the early boogie amps and how people used to say that a 1x12 combo could be louder than a 4x12.
Something with a big beefy magnet and an efficient voice coil like an eminence wizard, or a swamp thing depending on the kind of flavours you like. You will definitely get you a large extra serving of volume, punch and detail.
Maybe even celestion vintage 30, or an EV too. See what you can find for the right price and with the tones you like.
If you decide to do some research, what you are looking for on the speaker spec. sheet is MAx db (decibels), or max spl@1w (sound pressue levels). A difference of 3db is an appreciable difference to the ear, whereas a 6db increase sounds roughly twice as loud. (ie a 103db speaker will seem twice as loud as a 97db speaker like a greenback).
Different companies will obviously have slight variances in how they test, so eminence ratings might not line up exactly with celestion, but seeing as you already have an eminence speaker, it will be pretty easy. Another pretty damn idiot proof test is simply to look at the size of the magnet. If it has a much bigger chunkier looking magnet than the speaker you have, you can be pretty sure the speaker will be a lot louder.
This is a thread about your amp:
https://forum.seymourduncan.com/showthread.php?240561-Jet-city-Eminence-speakers
and a video:

fwiw, the eminence wizard is appreciably louder than the vintage 30 which the speaker in the video is modelled on.

Ok so I would get more by getting a speaker of a larger dB rating.

I will probably want it in an external cab, and I can run it with or without my internal speaker to my needs, but keep my stock for home use and small gigs as it is loud enough for that.

Given an extension cab of like sensitivity you'd get about 3 more dB....not much. But you would generate a wider sweet spot as the horizontal dispersion increases with more speakers.

I've gigged small venues with 5 watts and two V30's..but that was for my distortion channel. I'd use 30 watts for my clean. (Mesa Lonestar Special)

@both: To my knowledge, the decibel scale is one that the original power is multiplied by 10^(x/10), where x is the number of decibels in the change. This makes 3db a near perfect doubling difference. So do speakers not deliver that in reality?

The wider spread should help for sure on larger stages.

 

[SlyFoxx]

Re: Quick quiestion on External Cabnets

10dB louder is considered roughly twice as loud. 3dB louder is a noticeable difference but not a large one. The confusion stems from the fact that when you double the power you get about 3dB more volume. To get 10dB more volume from a given rig you need 10 times the power. In short, double the power doesn't equal double the volume/SPL. Number of speakers and their operating environment such inside or outside and proximity of reflective surfaces can alter things as well.

 

[TRex]

Re: Quick quiestion on External Cabnets

Ok, sorry I found my error.

My formula refers to intensity, not loudness.

So 10db=roughly 2x volume

 

[DrNewcenstein]

Re: Quick quiestion on External Cabnets

Case in point: my Carvin VE212 cabinet was noticeably louder than my singer's TubeWorks 4x12, both of us using identical heads, with identical settings. We swapped rigs and he was then louder through mine than I was through his. The 2x12 was rated for 300w, 4 Ohms. Not sure what his 4x12 was rated for. I'm assuming 300w at 8 or 16 Ohms.

 

[IM4Tone]

Re: Quick quiestion on External Cabnets

Given an extension cab of like sensitivity you'd get about 3 more dB....not much. But you would generate a wider sweet spot as the horizontal dispersion increases with more speakers........

This is not correct. Given an extension cab of like sensitivity will yield no more dB whatsoever. It will give a different perception due to the dispersion. And BTW, 3 dB is noticeable.

This commonly stated fallacy stems from the fact that if you take (for example) a 50 watt amp played into a given single speaker, a second identical speaker powered by an additional 50 watt amp will yield an additional 3 dB. That same single 50 watt amp driving both (2) of the identical speakers results in each of those speakers 'seeing' 25 watts, and the dB output of the pair being the same as if driving only one.

 

[TRex]

Re: Quick quiestion on External Cabnets

Wait, so no real difference will be made? Just a perceived difference?

I guess I'll have to get a louder speaker for a larger gigs then?

 

[zzmoore]

Re: Quick quiestion on External Cabnets

Wait, so no real difference will be made? Just a perceived difference?

I guess I'll have to get a louder speaker for a larger gigs then?

That is a tricky way to look at things.
While you need more power or more efficiency to get more Volume.....additional speakers Can Make a Big Difference.
You MAY have enough Power/Volume already..... but imagine being able to have another Pair Of Speakers on the other side of the stage for example. Not only will you be pushing more air, but you will be pushing it in a much larger area, and in space that was previously unavailable to your amp. An extension cabinet can be a Big Help.
You need to identify what it is that you really need to accomplish.
good luck

 

[IM4Tone]

Re: Quick quiestion on External Cabnets

Wait, so no real difference will be made? Just a perceived difference? ..........

.............It will give a different perception due to the dispersion............

zzmoore's comments are true, for sure!

 

[TRex]

Re: Quick quiestion on External Cabnets

That is a tricky way to look at things.
While you need more power or more efficiency to get more Volume.....additional speakers Can Make a Big Difference.
You MAY have enough Power/Volume already..... but imagine being able to have another Pair Of Speakers on the other side of the stage for example. Not only will you be pushing more air, but you will be pushing it in a much larger area, and in space that was previously unavailable to your amp. An extension cabinet can be a Big Help.
You need to identify what it is that you really need to accomplish.
good luck

Ok, so more speakers will increase the area at which I am heard, without increasing the total volume?

Sorry, I'm not well versed in the physics of sound.

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[IM4Tone]

Re: Quick quiestion on External Cabnets

Ok, so more speakers will increase the area at which I am heard, without increasing the total volume?

Sorry, I'm not well versed in the physics of sound.

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It will do that.

 

[SlyFoxx]

Re: Quick quiestion on External Cabnets

Just to put this to the test (and to rest) I just drug out my 4x12 cab (a 20 year old Carvin with 4 identical British Series speakers) and my Marshall. Set the rig to run as a 2x12 into 4 ohms as per the cabs specs. Set the Marshall to a decent amount of grind as the natural compression smooths out the volume. Set the dB meter aimed dead center at the cab about 3 feet back in the 90dB range. Adjusted the amp volume so as to read 92dB on the meter with the guitar full up as hard as I could strike it. Then I added the other two speakers into the equation going from the 4 ohm hole to the 8 ohm hole to match the new impedance. Guess what? 4 more dB. Yes, more speakers makes for a more efficient use of your amp's watts.

 

[IM4Tone]

Re: Quick quiestion on External Cabnets

The difficulty with a 'test' as you've made is that the amp's wattage output can/will vary with different impedance loads. If you had a way to measure the exact wattage output of the amp, the 'test' would be more valid.

Laws of physics are just that....laws/facts. Wattage (a measurement of electrical energy) is converted to dB (a measurement of SPL or sound energy) by the speaker(s). If the speakers are all identical sensitivities, they can't individually nor collectively create more energy in the conversion of wattage to dB.

I applaud your effort to attempt to scientifically test this premise, but something other than 4 vs 2 speakers varied in your test to cause a different reading. There are many possible contributors......total impedance load on the amp (additionally affected by different windings on the output transfer when the amp's impedance switch is changed), different frequencies (sensitivity does vary with freq.), pick attack, and the actual sound meter itself. My sound meter can vary 2 to 4 dB with no changes of the amp's knobs into the same cab, even when I think I've played the same notes with the same attack.

Don't buy into the internet chatter (this includes what I have to say since I'm an unknown, credibility-wise).....review your physics, or consult a bona fide expert in physics.

 

[Liko]

Re: Quick quiestion on External Cabnets

If I was to run my Jet city JCA2212 into either a 2x12 or another 1x12 as a extention to the 1x12 in the combo, how much louder would it be?

I hear stories of guys running 5 watters into 4x12 cabs and getting giggible levels, where a 50watt amp would normally be used.

Sent from my SAMSUNG-SM-G920A using Tapatalk

Lot of variables involved. Technically, by adding a 1x12, you're cutting the power each speaker receives in half, but doubling the total surface area of the speaker cones pushing air. Considering just these two things, it's a wash.

However, all things are not equal. One other major thing that changes is the total impedance of your speaker system. By adding a second cabinet in parallel, you reduce the impedance of the speaker circuit, therefore given the same voltage produced by the amplifier, more current (and thus more power) flows to the speakers. If both speakers are the same impedance (say 16 ohms), adding the second one cuts impedance in half (1/Rt = 1/R1 + 1/R2, so 1/16 + 1/16 = 1/8), so ideally given the same voltage, double the current flows, and watts equals volts times amps so we get double the power. In reality it's not quite double, but it's close enough to say that you can expect about a 3dB increase in volume by adding a second cabinet of equal speaker surface area and impedance to your existing rig.

So really, what you're doing by taking a 5W 1x12 guitar combo and running it through an additional 1x12 is turning it into a 10W head (or, if the amp was rated 5W at 8 ohms and you had been running it at 16ohms, you're turning a 2.5W head into 5W).

Another huge variable is speaker sensitivity. This is a measure of how efficiently the speaker will transform the power you give it into acoustic sound waves. The number you get is the sound pressure level you'd experience standing one meter away from the speaker while it is being given a signal of 1WRMS power at the speaker's resonant peak frequency. Double the wattage, you get a 3dB increase in SPL all other things being equal. Double the distance, you get a 6dB decrease. This means that a 97dB-sensitivity speaker sounds half as loud as a 107dB-sensitivity speaker. If the speaker cabinet you add is more sensitive than the one in the first cabinet, volume will increase by more than 3dB because the speaker is more efficiently transforming the power it gets into sound.

Lastly, sensitivity isn't constant. As guitarists, we're familiar with the concept of "peaking" or "clipping". Typically we think of this being a property of the transistors (tubes or solid-state) in the amplifier, where given a stronger input the output does not increase by a proportional amount, because the transistor simply cannot provide it. However, a similar thing happens with speakers; as the power increases, the forces within the speaker chassis designed to keep the voice coil from shooting the cone out into the audience begin hindering the cone's movement and so the marginal increase in volume doesn't match the marginal increase in power. This is more of an issue when running speakers much closer to their peak power rating than you'd ever get with a 5W amp and a garden-variety Eminence or Celestion, but even at lower power levels, if double the power doesn't equal double the volume, then spreading that power across more cones will get you more volume than trying to push it all through one cone.

 

[IM4Tone]

Re: Quick quiestion on External Cabnets

Lot of variables involved. Technically, by adding a 1x12, you're cutting the power each speaker receives in half, but doubling the total surface area of the speaker cones pushing air. Considering just these two things, it's a wash.

However, all things are not equal. One other major thing that changes is the total impedance of your speaker system. By adding a second cabinet in parallel, you reduce the impedance of the speaker circuit, therefore given the same voltage produced by the amplifier, more current (and thus more power) flows to the speakers. If both speakers are the same impedance (say 16 ohms), adding the second one cuts impedance in half (1/Rt = 1/R1 + 1/R2, so 1/16 + 1/16 = 1/8), so ideally given the same voltage, double the current flows, and watts equals volts times amps so we get double the power. In reality it's not quite double, but it's close enough to say that you can expect about a 3dB increase in volume by adding a second cabinet of equal speaker surface area and impedance to your existing rig.

So really, what you're doing by taking a 5W 1x12 guitar combo and running it through an additional 1x12 is turning it into a 10W head (or, if the amp was rated 5W at 8 ohms and you had been running it at 16ohms, you're turning a 2.5W head into 5W).

Another huge variable is speaker sensitivity. This is a measure of how efficiently the speaker will transform the power you give it into acoustic sound waves. The number you get is the sound pressure level you'd experience standing one meter away from the speaker while it is being given a signal of 1WRMS power at the speaker's resonant peak frequency. Double the wattage, you get a 3dB increase in SPL all other things being equal. Double the distance, you get a 6dB decrease. This means that a 97dB-sensitivity speaker sounds half as loud as a 107dB-sensitivity speaker. If the speaker cabinet you add is more sensitive than the one in the first cabinet, volume will increase by more than 3dB because the speaker is more efficiently transforming the power it gets into sound.

Lastly, sensitivity isn't constant. As guitarists, we're familiar with the concept of "peaking" or "clipping". Typically we think of this being a property of the transistors (tubes or solid-state) in the amplifier, where given a stronger input the output does not increase by a proportional amount, because the transistor simply cannot provide it. However, a similar thing happens with speakers; as the power increases, the forces within the speaker chassis designed to keep the voice coil from shooting the cone out into the audience begin hindering the cone's movement and so the marginal increase in volume doesn't match the marginal increase in power. This is more of an issue when running speakers much closer to their peak power rating than you'd ever get with a 5W amp and a garden-variety Eminence or Celestion, but even at lower power levels, if double the power doesn't equal double the volume, then spreading that power across more cones will get you more volume than trying to push it all through one cone.

You have some facts mixed in with some fallacies. Without critiquing the entire post, let me just highlight one: You have described what occurs in a solid state amp NOT in a tube amp.

 

[SlyFoxx]

Re: Quick quiestion on External Cabnets

I dunno. Got the same result a moment ago with recorded drum samples via the fx return. A tick above 90 dB from each hit with two speakers. 94dB with four.

With a little research I've found it's the phenomena of "mutual coupling". In a nutshell speakers grouped closely together and reproducing the same signal reinforce each other up to around 500 hz (that's about B on the seventh fret of the high E string) to the tune of up to 6 dB.

 

[Liko]

Re: Quick quiestion on External Cabnets

You have some facts mixed in with some fallacies. Without critiquing the entire post, let me just highlight one: You have described what occurs in a solid state amp NOT in a tube amp.

I'm unclear. You're saying that in a tube amp, Ohm's law doesn't hold, so a speaker system with half the impedance gets the same current and therefore the same power? That makes no sense. I agree that tubes don't act ideally (not nearly as close to the ideal transistor behavior as solid-state anyway), but unless the tubes are providing a self-limiting effect that keeps the impedance of the speaker circuit roughly constant, or the amp design only works at a single nominal impedance so adding cabs requires changing the impedance of the ones you have, more cabs equals less impedance equals more speaker circuit power.

 

[dystrust]

Re: Quick quiestion on External Cabnets

I'm unclear. You're saying that in a tube amp, Ohm's law doesn't hold, so a speaker system with half the impedance gets the same current and therefore the same power? That makes no sense. I agree that tubes don't act ideally (not nearly as close to the ideal transistor behavior as solid-state anyway), but unless the tubes are providing a self-limiting effect that keeps the impedance of the speaker circuit roughly constant, or the amp design only works at a single nominal impedance so adding cabs requires changing the impedance of the ones you have, more cabs equals less impedance equals more speaker circuit power.

I was under the impression that a tube amp's output transformer performs essentially that function.