How much difference does speaker efficiency make?

[Mind Riot]

As it relates to guitar speakers, I mean.

 

I know that it doesn't really stand to reason that if one speaker is 3 db more efficient than another then the more efficient speaker will only be 3 dbs louder than the other one at any wattage. I know that 3 db is not a huge difference in volume. I've heard people talk about how more efficient speakers are very noticably louder.

 

So can someone explain more of how it works? Is the difference in efficiency, measured in dbs, multiplied somehow with more wattage? As in, 3 db difference with 1 watt or power will translate to 6 db of difference with 10 watts? Or what?

 

I'm curious about this, I just bought a used 4x12 cab that's on it's way, and it's loaded with Eminence M12's. They have what seems to be a very high efficiency rating, 102 db. So I'm wondering just how all this works, and how much practical difference there really is.

 

Thanks in advance for any information.

[Cougar Hunter]

a sensitive enough speaker could blow the roof off of a house with one watt of power.

[hal9000]

Speaker sensitivity is usually rated by placing a sound pressure instrument one (1) meter away from the speaker with one (1) watt of input power. So, the higher the power, the higher the output sound pressure level.

For example:
A Celestion Vintage 30 is rated for 100 dB 1 w/1 m. (
If you put 10 watts into the V30 and measure it in the same place (1 meter), it should produce 100 dB + 10*LOG(10) = 100 dB SPL + 10 dB = 110 dB SPL @ 1 m.

Speaker efficiency is actually pretty low and on the order of 1-5% of the electrical power is converted to acoustic power.

[SuperStrat]

Huge... you can make a 30 watt amp appear to be louder than a 100 watter with speaker selection.

[Rich]

I know that Blues are the loudest damned speaker I have ever heard to date.

[blackba]

Actually 3dB is a huge difference in sound. The minimum change most people can hear is 1dB. Doubling the Sound pressure level is an increase or 10dB.

Anyway speaker efficiency is a big factor. Its the most important in PA applications though. The cheaper PA speakers have efficienies of around 90dB, where as the nicer speakers have efficienies of around 100dB or 2 times louder.

[dparr]

Eminence measures there speakers from the outside of the cabinets grill.
Some manufactures measure from the cone to get a better reading.

[GCDEF]

As it relates to wattage, doubling the power = 3dB.

Put another way, a 100 watt amp with a 97dB speaker will be the same volume as a 50 watt amp with a 100dB speaker. (There are other factors involved, but all else being equal, that would be the case).

[hal9000]

Originally posted by dparr Eminence measures there speakers from the outside of the cabinets grill. Some manufactures measure from the cone to get a better reading.

I'm not following you here. If the specification is to measure a speaker with 1 W of input power @ 1 meter away from the cone (probably the outside edge?) then all the measurements should be comparable. Otherwise the spec is poorly written.

[dparr]

Some measure from the cone.
Some measure from the outside of the speaker.
Eminence measures from the outside of the grill.
A little more distance than the others.

[tlbonehead]

Originally posted by Mind Riot As it relates to guitar speakers, I mean. I know that it doesn't really stand to reason that if one speaker is 3 db more efficient than another then the more efficient speaker will only be 3 dbs louder than the other one at any wattage. I know that 3 db is not a huge difference in volume. I've heard people talk about how more efficient speakers are very noticably louder. So can someone explain more of how it works? Is the difference in efficiency, measured in dbs, multiplied somehow with more wattage? As in, 3 db difference with 1 watt or power will translate to 6 db of difference with 10 watts? Or what? I'm curious about this, I just bought a used 4x12 cab that's on it's way, and it's loaded with Eminence M12's. They have what seems to be a very high efficiency rating, 102 db. So I'm wondering just how all this works, and how much practical difference there really is. Thanks in advance for any information.

How can you not see that as a major difference. Say you have a good basic club sound system. And you were pushing 6K watts through the mains with a speaker efficiency rating of 100db/wat. Now if you wanted to achieve the same clean capability and had chosen speakers with a 97db rating,you would need 12K watts of power on hand. And maybe more speakers as well.

[Osmosis]

Originally posted by dparr Some measure from the cone. Some measure from the outside of the speaker. Eminence measures from the outside of the grill. A little more distance than the others.

UNless the grille extends one meter past the cone, then somebody's spec isn't valid...

efficiency spec = 1W @ 1 meter

[Mind Riot]

Originally posted by tlbonehead How can you not see that as a major difference. Say you have a good basic club sound system. And you were pushing 6K watts through the mains with a speaker efficiency rating of 100db/wat. Now if you wanted to achieve the same clean capability and had chosen speakers with a 97db rating,you would need 12K watts of power on hand. And maybe more speakers as well.

 

 

I understand that efficiency makes a big difference. What I want to know is if there is an equation or method used to determine how efficiency specs between otherwise equal speakers affect output at various wattage levels.

 

As in, a 3 db difference at 1w/1m is 3 dbs.

 

So, a 3 db difference in efficiency at 50w/1m is...?

[tlbonehead]

Originally posted by Mind Riot I understand that efficiency makes a big difference. What I want to know is if there is an equation or method used to determine how efficiency specs between otherwise equal speakers affect output at various wattage levels. As in, a 3 db difference at 1w/1m is 3 dbs. So, a 3 db difference in efficiency at 50w/1m is...?

3db = 3db.

[Mind Riot]

Originally posted by tlbonehead 3db = 3db.

Never mind, I found it after some googling (and actually I just noticed hal9000 already posted it, thanks man!):

Om = (10 x log Pm) +S1, where

Om = maximum output
Pm = maximum input power
S1 = sensitivity measured at one Watt/one meter



Okay, I see now. I used this equation with a variety of output wattages, and it seems that whatever advantage in decibels you get from better efficiency stays constant regardless of the watts fed to it. So in other words, 3 db louder at 1w/1m, 3 db louder at 100 watts/1m. That's all I was wondering, just whether speaker efficiency made more of a difference with more power or not, but it doesn't.

Maybe everybody else already knew this, but I did some searches on here for 'efficiency' and 'sensitivity' and this particular aspect of it wasn't explicitly discussed in the threads I found so I thought I'd ask.

Thanks for everybody's contributions to the thread.

[tlbonehead]

Originally posted by Mind Riot Never mind, I found it after some googling (and actually I just noticed hal9000 already posted it, thanks man!): Om = (10 x log Pm) +S1, where Om = maximum output Pm = maximum input power S1 = sensitivity measured at one Watt/one meter Okay, I see now. I used this equation with a variety of output wattages, and it seems that whatever advantage in decibels you get from better efficiency stays constant regardless of the watts fed to it. So in other words, 3 db louder at 1w/1m, 3 db louder at 100 watts/1m. That's all I was wondering, just whether speaker efficiency made more of a difference with more power or not, but it doesn't. Maybe everybody else already knew this, but I did some searches on here for 'efficiency' and 'sensitivity' and this particular aspect of it wasn't explicitly discussed in the threads I found so I thought I'd ask. Thanks for everybody's contributions to the thread.

Ahhh,I see what you were getting at.

[potaetoes]

Originally posted by Mind Riot Never mind, I found it after some googling (and actually I just noticed hal9000 already posted it, thanks man!): Om = (10 x log Pm) +S1, where Om = maximum output Pm = maximum input power S1 = sensitivity measured at one Watt/one meter Okay, I see now. I used this equation with a variety of output wattages, and it seems that whatever advantage in decibels you get from better efficiency stays constant regardless of the watts fed to it. So in other words, 3 db louder at 1w/1m, 3 db louder at 100 watts/1m. That's all I was wondering, just whether speaker efficiency made more of a difference with more power or not, but it doesn't. Maybe everybody else already knew this, but I did some searches on here for 'efficiency' and 'sensitivity' and this particular aspect of it wasn't explicitly discussed in the threads I found so I thought I'd ask. Thanks for everybody's contributions to the thread.

no, sensitivity/efficiency does not remain constant at all power levels.

every speaker behaves differently throughout its range of operation. guitar speakers especially change behavior, because few of them are designed to stay totally "clean" like hi-fi and PA speakers are, and because guitar cabs are almost never designed according to theile-small parameters. comb filtering at the cone, thermal compression, cabinet interaction, and plenty of other factors can significantly alter a speaker's response at high power levels.

efficiency ratings are also made with a test signal, that doesn't resemble anything you'd ever play on a guitar. the frequency response curve and how well your amp/guitar match with it, will have a significant impact on the effective loudness of the speaker.

a 100w 97db/m speaker that stays really clean, could actually be quite a bit louder at full power than a 100w 100db/m speaker that is designed to break up more.