wattage vs sub senstivity

[Beatin' 10+ year member]

Is this following statement correct?

An amp giving 500wrms to a sub with a sensitivity rating of 90db will have the same loudness as an amp giving 1000wrms to a sub with a sensitivity rating of 87db.

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[JimJ 5,000+ posts]

No.

1) Sensitivity ratings need to be taken with a huge grain of salt. What impedance are they using? Is it specified at 1W/1m, or 2.83V at whatever distance they want? Make sure you're comparing values on the same scale.

2) Power compression. Once you put enough power into a speaker, at some point you'll no longer have a linear increase in SPL.

3) Probably won't matter with only a 3dB difference in sensitivity, but if you're looking at a large difference (85 to 95, for example), the enclosure requirements will likely be different as a lot of different tradeoffs were made in the design.

 

[brandon_s0854 10+ year member]

Good answer Jim.

 

[Beatin' 10+ year member]

No.
1) Sensitivity ratings need to be taken with a huge grain of salt. What impedance are they using? Is it specified at 1W/1m, or 2.83V at whatever distance they want? Make sure you're comparing values on the same scale.

2) Power compression. Once you put enough power into a speaker, at some point you'll no longer have a linear increase in SPL.

3) Probably won't matter with only a 3dB difference in sensitivity, but if you're looking at a large difference (85 to 95, for example), the enclosure requirements will likely be different as a lot of different tradeoffs were made in the design.

Let's say the sensitivity is based on CEA-2006 standards and, all else being equal, still the statement isn't true at all? So it's best to focus on other factors rather than subwoofer sensitivity?

I've always thought sensitivity ratings were a big deal, as the higher they are, the less power you need for high SPL. Right?

 

[Flipx99 5,000+ posts]

Let's say the sensitivity is based on CEA-2006 standards and' date=' all else being equal, still the statement isn't true at all? So it's best to focus on other factors rather than subwoofer sensitivity?
I've always thought sensitivity ratings were a big deal, as the higher they are, the less power you need for high SPL. Right?[/quote']

I wouldn't look at sensitivity when comparing car audio subwoofers.

 

[JimJ 5,000+ posts]

Let's say the sensitivity is based on CEA-2006 standards and' date=' all else being equal, still the statement isn't true at all? So it's best to focus on other factors rather than subwoofer sensitivity?
I've always thought sensitivity ratings were a big deal, as the higher they are, the less power you need for high SPL. Right?[/quote']

CEA-2006 is an amplifier rating standard. Manufacturers can play whatever kind of snake oil games they want to on speakers. But even assuming the ratings are equal, you aren't going to beat power compression. Get the magnets hot enough, and you simply can't sustain a linear relationship between how much power you throw at the speaker and how much SPL is the result...

Subwoofer design is a balance of many factors. While very-high sensitivity subs can be really good for SPL (original Strokers being the prime example, as they were derived from PA speakers), they often require tradeoffs that customers are unwilling to make. Like refrigerator-sized enclosures.

I wouldn't look at sensitivity when comparing car audio subwoofers.

The end result is this...

 

[Full Tilt 10+ year member]

CEA-2006 is an amplifier rating standard.

Which doesn't count for sh*t anyway.

 

[Chriszle 10+ year member]

Subwoofer sensitivity is often shown from frequencies that your subwoofer will never ever play. They are pretty much useless.

 

[zako 10+ year member]

Subwoofer and speaker sensitivities are often totally oversold. One thing you should be aware of is that you can rate the subwoofer using 1watt/1meter SPL standard or 2.8V/1meter. These are not the same.

2.8V corresponds to 2watts if the subwoofer has nominal 4ohm impedance, and 4watts if the subwoofer has 2ohm impedance. So, if the manufacturer gives you SPL for a 4ohm DVC subwoofer are measured at 2.8V/1meter method, then you should realize that the rating is done at 4watts. This rating should be roughly 6dBs higher than the rating done with 1watt/meter measurement.

Now, let's say that you are compared apples to apple. Two subwoofers with equal final impedance, and you have 1watt/1meter SPL rating. Let's say the first one is 82dB and the second is 85dB. Does this mean that you need to run twice as much power to the first subwoofer to make it play as loud as the second? Maybe.. perhaps..likely. But that's not the whole story because 1watt/1meter is a small signal rating. It's said that in theory power should be doubled to increase the SPL by 3dB, but the speaker may not respond linearly to doubling power at high wattage levels.

By the way, so how do you obtain 1watt/1meter SPL sensitivity if the manufacturer does not give it to do? Enter T/S parameters into subwoofer parameters dialog in WinISD alpha. It will calculate the SPL sensitivity for you. It's pretty good, it's usually within something like 1/10ths of the number supplied by the manufacturer (when they do).