Speaker sensitivity - help me understand

[tfarny]

Quick question for those of you who know lots about amps - how drastic is the volume difference between speakers of different sensitivities? For instance, the Celestion Greenback is 97db, the Vintage 30 is 100 db (1w @ 1m). Looking at a few of the Eminence 12", they range from "SPL" of 98 to 102db, which they say is an 'average' across, blah blah.
Just comparing within one manufacturer, are these differences significant in terms of output at a given signal strength from an amp?
The reason I'm asking is because I'm thinking I want a less sensitive speaker if I think my next amp will tend to be too loud (Possibly ceriatone 18watt marshall clone, or even a JTM45 clone, in a 1x12 combo). But I'm not sure if sensitivity is really the number to look at, or if this is a difference worth bothering with.

 

[Kublai]

I am not certain that audio power level is the same as rf, but, a 3 dB increase in rf equates to doubling the power. If that is the case with speakers, then the greenback is half as loud as the vintage.

 

[Patrick from Davis]

The efficiency rating is kind of a lot of things lumped into one measurement.  SPL stands for Sound Pressure Level, and dB's are decibels obviously.  It is generally measured at 1 meter powered by one watt.  So the larger the number the more efficient the speaker.  Like pick up resistance measurements, a lot of things are inferred by this number.  The more efficient the speaker is, the better clarity it "Should" have.  This doesn't always work out.  For engineers there are the Theile Small specs, but those are essentially mystifying if you have not worked quite a bit with them.  Other than all of the mumbo jumbo I have listed, yea, the bigger the number the louder the speaker and generally the better the clarity at a given wattage.  Less clarity is a warmer speaker, and so on
Patrick

 

[Superlizard]

Depending on wattage you need, Celestion Alnico Golds (50W) or Blues (15W). 

'nuff said, cuz God Himself designed these speakers.

 

[AndyG]

Here's a link that explains (to some degree) the whole speaker sensitivity issue:

http://www.projectsunlimited.com/audioProducts/MovieClips/TechNotes/Glossary.asp?articalID=29

One thing when comparing products from different manufacturers is to be very careful with specs.  Depending on what's being measured, the same numbers have different meanings.  Personally, I believe the cabinet design will have more to do with how loud you will get than the speakers.  For instance, the classic Marshall 4X12.  If you're standing next to the amp, playing at full volume, you'll probably hear yourself OK, but you'll be killing the people 10 feet away.  That's the way the cabinet was designed to "throw".

My benchmark has always been:  if I like the way it sounds, that's the one I'll buy.

 

[GoDrex]

Depending on wattage you need, Celestion Alnico Golds (50W) or Blues (15W). 

'nuff said, cuz God Himself designed these speakers.

God gets a cut from sales of those too. :laughing7:

One of them costs as much as what I paid for my 2x12 cab.

 

[jimh]

I am not certain that audio power level is the same as rf, but, a 3 dB increase in rf equates to doubling the power. If that is the case with speakers, then the greenback is half as loud as the vintage.

Be a little bit careful here.  In terms of power output then yes 3dB does equate to a doubling in power,

3dB is "noticably louder", but not twice the volume level.  Most people perceive a 'doubling' in volume level (ie twice as loud) at around 10dB increase in Sound Pressure Level. 
Doing some maths means that to acheive an 10dB increase in SPL would mean an equivalent (roughly speaking) 10 fold increase in amplifier power.

or in other words ...... (taken from http://stereos.about.com/od/stereoscience/a/amppower.htm)

Amplifier power, measured in watts, can be a confusing subject and is commonly misunderstood. A common misconception is that wattage has a direct correlation to loudness or volume. Some believe that doubling the power output will result in a maximum volume that is twice as loud. In fact, power has little to do with loudness. Power output is relevant to two main issues:

  1. Speaker efficiency
  2. The ability of the amplifier to handle musical peaks

Speaker efficiency, also known as speaker sensitivity, is a measure of the speaker's output, measured in decibels, with a specified amount of amplifier power. For example, speaker efficiency is often measured with a microphone (connected to a sound level meter) placed one meter from the speaker . One watt of power is delivered to the speaker and the level meter measures the volume in decibels. The output level results in a measure of efficiency. Speakers range in efficiency or sensitivity from about 85dB (very inefficient) up to 105dB (very efficient). As a comparison, a speaker with 85 dB efficiency rating will take twice the amplifier power to reach to same volume as a speaker with 88 dB efficiency. Similarly, a speaker with a 88 dB efficiency rating will require ten times more power than a speaker with a 98 dB efficiency rating to play at the same level. If you're starting with a 100 watt/channel receiver, you would need 1000 watts (!) of power output to double the perceived volume level.

Clear as mud?  :icon_thumright:

 

[tfarny]

So, going from 97db to 100db sensitivity is theoretically, sort of, the sonic equivalent of going from a 20 watt to a 40 watt output tube amp, then? In other words, yes it makes plenty enough difference to matter.
Based on the chart here: http://www.projectsunlimited.com/audioProducts/MovieClips/TechNotes/Glossary.asp?articalID=29 \

 

[Superlizard]

But I'm not sure if sensitivity is really the number to look at, or if this is a difference worth bothering with.

I shoulda added this as I prolly didn't make it obvious enough in my last post - it's not a difference worth bothering with... the tone of the speaker is (and of course the wattage and ohms).  T00b amps are freakin' loud enough to nullify the minute SPL/sensitivity differences 'tween speakers.

 

[Superlizard]

God gets a cut from sales of those too. :laughing7:

One of them costs as much as what I paid for my 2x12 cab.

You ain't kidding.

But Avatar does good on 'em .... got my vintage 1X12 with Gold for ~$450.  If and when I get another speaker cab, I'm doing Avatar again.

 

[jackthehack]

"So, going from 97db to 100db sensitivity is theoretically, sort of, the sonic equivalent of going from a 20 watt to a 40 watt output tube amp, then?"

Yes.

In other words, yes it makes plenty enough difference to matter.

Yes and no; while there is a discernable difference going from a 20 watt to a 40 watt amplifier, theoretically you'd get a 3dB gain in SPL, noticible, but not HUGELY so.