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Will one 12" speaker in an open back cab be louder than a 2 closed back 10" cabs?

jonhope

Member
Messages
77
Hi All,

I have a 99dB ceramic speaker in an open back cabinet

I am thinking of purchasing a pair of 10" closed back cabinets with 96dB rated speakers.

The amp I want to use with them will take the two 10 inchers in parallel (two 16 ohm inputs)

My question is how do I (whats the formula if there is one?) work out what the volume difference will be between the two set ups?

Are we talking an equation using speaker surface area against rated SPL?

Thanks very much

:beer
 

Trebor Renkluaf

I was hit by a parked car, what's your excuse?
Gold Supporting Member
Messages
14,289
Well one 12" speaker is moving 113.1 square inches of air while 2 10" speakers are moving 157.1 square inches. Not sure how this relates to the efficiency. A closed back cabinet will be more directional - when your not standing in front of it, it might seem quiet, but then get in the beam and get blasted. An open back cabinet is going to spread the sound around more - it will sound louder of axis, and wont be as loud when standing right in front of it.
 

GCDEF

Silver Supporting Member
Messages
28,465
Surface area has nothing to do with it. The single more efficient speaker will be louder, but as Trebor mentioned, the sound will be distributed differently.
 

jonhope

Member
Messages
77
Hey guys,

Thanks for the info

So at what point will there be a cross-over - surely a 4 x 10 cab (with 96dB speakers) will be louder than a 1 x 12 (with a 99dB speaker) irrespective of the cabinet construction?

:beer
 

Schroedinger

Member
Messages
2,125
Surface area has nothing to do with it. The single more efficient speaker will be louder, but as Trebor mentioned, the sound will be distributed differently.
Can I respectfully disagree with this point? My understanding is that feeding 2 identical speakers with the same power as you would feed 1 of them results in a 3db increase in volume. Therefore, the total efficiency would be comparable with both of your options. Also, there would be less cone excursion with 2 speakers vs. one speaker, so you would probably be operating the speakers in the range that they are more efficient; when the magnet pole is still entirely within the voice coil. And the surface area does have a profound effect when it comes to bass response; so the 2x10 might be able to play a little deeper, especially if the closed cabinet is tuned.
There is likely to be so much other stuff going on that the results wouldn't be totally predictable. Open back vs. closed back, phase cancellation, frequency response differences, etc. Hard to tell which one would actually SOUND louder. But I'm guessing they'd be pretty close in terms of volume.
 

Mark Robinson

Platinum Supporting Member
Messages
8,947
I will offer this, an open back cabinet with an EVM12L in it, can be played
really loud, and I cannot think of a 2 x 10 cab that would keep up with it. There probably are some though, I've just never heard or seen them. I knew a guy years ago with Tremolux cabinet he had loaded with JBL K110 speakers, which would go pretty loud, but didn't sound very good, too lean, pretty harsh.
 

Trebor Renkluaf

I was hit by a parked car, what's your excuse?
Gold Supporting Member
Messages
14,289
I will offer this, an open back cabinet with an EVM12L in it, can be played
really loud, and I cannot think of a 2 x 10 cab that would keep up with it. There probably are some though, I've just never heard or seen them. I knew a guy years ago with Tremolux cabinet he had loaded with JBL K110 speakers, which would go pretty loud, but didn't sound very good, too lean, pretty harsh.
An EVM is both an efficient speaker and a speaker that can handle A BUNCH of power.
 

GCDEF

Silver Supporting Member
Messages
28,465
Can I respectfully disagree with this point? My understanding is that feeding 2 identical speakers with the same power as you would feed 1 of them results in a 3db increase in volume. Therefore, the total efficiency would be comparable with both of your options. Also, there would be less cone excursion with 2 speakers vs. one speaker, so you would probably be operating the speakers in the range that they are more efficient; when the magnet pole is still entirely within the voice coil. And the surface area does have a profound effect when it comes to bass response; so the 2x10 might be able to play a little deeper, especially if the closed cabinet is tuned.
There is likely to be so much other stuff going on that the results wouldn't be totally predictable. Open back vs. closed back, phase cancellation, frequency response differences, etc. Hard to tell which one would actually SOUND louder. But I'm guessing they'd be pretty close in terms of volume.
You'd get a 3dB increase if you fed two the same power as you fed one, but since the power is divided between the two, you're only feeding each one half the power, so the net output is the same.

He didn't ask about frequency response so I didn't address it. The only number he gave us to work with was efficiency, so that's what I addressed. Anything else would just be assumptions.
 

GCDEF

Silver Supporting Member
Messages
28,465
Hey guys,

Thanks for the info

So at what point will there be a cross-over - surely a 4 x 10 cab (with 96dB speakers) will be louder than a 1 x 12 (with a 99dB speaker) irrespective of the cabinet construction?

:beer
Although it's somewhat counterintuitive, simply adding speakers doesn't add volume, unless your speakers are running at the point where they just can't get any louder. So at some point, assuming the 4 x 10 could handle more power than the single 12, it would be possible to get more volume out of it by feeding it more power.
 

Tone_Terrific

Silver Supporting Member
Messages
35,061
Some info indicates that adding a speaker, in close proximity to another, will net a 3db improvement in efficiency. There are a lot of variables.
Check out the threads featuring Jay Mitchell's posts.
When he is not arguing with someone there is a lot of info available.
Counter-intuitve? Yep! It is hard to judge acoustical effects based on how things look.
How they sound is deceptive, too.:bonk
 

sharpshooter

Senior Member
Messages
4,009
Well,,,, a 3db change in efficiency is quite a bit. Their is a coupling effect when speakers are put in close proximity to each other, which can lead to a perceived increase in loudness. But, much has to do with the freqs, and how well the speakers are matched.
Also, the closed back cab, because of the air trapped inside, acting as a damper, will take more power to reach the same cone excursion, (less efficient). As a "by guess and by gosh", without hard data, it's really kind of a crap-shoot.
 




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