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Sensitivity rating

 

Juggalo Jeff
Unregistered guest
What does this actually mean. Is a sub with a higher sensitivity db rating better or does it depend on ones preferences
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2259
Registered: May-04
It just means that a given sub will be louder with 1W of power. The general rule is that with double the power, a 3 db increase will occur, so theoretically a sub that's more efficient will be louder for a given amount of power. BUT there are many exceptions. Some subs take more power, ending up with more SPL, some companies efficiency ratings are total BS, they fudge the ratings by either weighting the true efficiency or change the rules (such as 2.83V instead of 1 watt, not listing distance measured from, resulting in more SPL b/c it's closer, etc.). It's one of the specs you have to take with a grain of salt. Enclosures, etc. make a difference as well, but aren't noted in efficiency ratings.
 

Juggalo Jeff
Unregistered guest
thanx
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2262
Registered: May-04
If you want an accurate way of finding sub efficiency, go here http://www.adireaudio.com/TextPages/TechReportsPageFrameText.htm
and download the SPL calculation file.
 

Silver Member
Username: Fishy

Tamarac, FL USA

Post Number: 523
Registered: Sep-04
Yeah aren't those things "infinite baffle" free air ratings anyways? or simply free air.

-Fishy
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2263
Registered: May-04
Yep. Any speaker that isn't designed for free air (such as heavy coned, loose suspension type small sealed box subs) will usually put out more SPL when tested beside an infinite baffle designed subwoofer or speaker because it has less control, while one designed for IB will have more cone control. Put that small sealed designed woofer in it's intended box and things will change.
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 4565
Registered: Dec-03
Speaker sensitivity

Speaker sensitivity is a specification provided by all manufacturers of high-quality speakers. The sensitivity rating has no relation to sound quality, as some of the very best speakers have low ratings. Sensitivity ratings simply tell you how much sound a speaker will produce for a given power input.

Sensitivity ratings are given in decibels per watt at one meter, or db/Wm. So, with an input of one watt (usually white noise), a speaker with a sensitivity of 90 db/Wm will produce 90 decibels of sound at a distance of one meter. A sensitivity of 90 is considered average, with ratings of 87 and below considered low sensitivity and above 93 considered high sensitivity. To increase the volume by 3 db, you must double the power. So, using the example above, to make 93 db you would need two watts, and to make 96 decibels, four watts.

Most of the time your system is cruising along producing only a few watts. You need extra power for loud bass passages, crescendos in classical music, and other highly dynamic passages. Your speakers may need more than 10 times the average power to re-create these dynamic passages accurately, and if you are playing loudly to begin with, you may need an awful lot of power if you have speakers with a low sensitivity rating.

So, when you are buying an amplifier, consider your speakers, your vehicle size and how loudly you want to play. If you have sensitive speakers, you probably will not need as much power -- even 20 clean watts would probably be enough. If your speakers are only moderately sensitive, your vehicle is large or exceptionally noisy at highway speeds and you want to play loudly, you will need more power in order to faithfully reproduce dynamic passages.

"Sensitivity" which is expressed in dB, should not be confused with "efficiency" that is expressed as a percentage of power out relative to power in. Efficiency data for loudspeakers suffers from many problems such as failure to consider variations in frequency response.

Speaker efficiency is the ability of the speaker to do work or use power. The more efficient the speaker; the less power is required for the speaker to produce sound. Voice coil design, type and size of the magnets, speaker cone design and material, speaker size, etc. all play a critical role in determining speaker efficiency. However, speaker size is a good general method for guessing efficiency.

Typical speaker efficiency (for physicists) is about 5%. Meaning that for 100% power input, you get about 5% acoustical work back.

Keep in mind that when considering subwoofers, or any speaker that will get more than ~100 watts RMS of power, these measurements are affected by other factors that make this specification less than useful when choosing between speakers.
 

Juggalo Jeff
Unregistered guest
well put glass thanks
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 4597
Registered: Dec-03
thanks.
I wrote that last year for a car audio forum FAQ.
thought it might help
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