Real sensitivity ratings

[wlb]

I am looking for a woofer with a real sensitivity leval of 94 to 95 dbs. I was looking at the Daton 10" dvc that says it is 93db but when I looked at the FR graph it looks like it barley makes it to 90db for only about a half octive span. The 12" says 94db and gets to 92dbs for only a few hundred hzs. Whats the deal with these ratings? Are these accurate mesurments or just wishful thinking? I may have to go to a pro speaker to find a true 95db spl rating. I only need it to from 100 to 400hz at that leval.

[Wolf]

They are "nominal" sensitivity ratings, and yes- you probably will have to use a pro-driver for those levels, unless you bi-amp to compensate.
Later,
Wolf

[Max_Andrews]

Since woofers are generally measured on an infinite baffle, they can appear to be around 96dB but after a baffle step loss depending on the cabinet and placement, the lower frequencies below 500hz may only be between 90dB and 93dB. So even a 97dB pro woofer, if placed in a medium sized box and placed away from walls, may only be around 92dB after the loss from baffle step. The only way you are going to get 95dB from a single woofer is a pro woofer placed on an infinite baffle, or placed very close to a wall. A better bet would be to wire two pro woofers in parallel, to have a theoretical sensitivity of around 100dB but an actual sensitivity of about 96dB. Of course the downside is you need a box that's twice as big, but if only used between 100hz-400hz use a small sealed box and it will be fine.

[billfitzmaurice]

> I may have to go to a
> pro speaker to find a true 95db spl rating.

You probably will. More to the point, unless you are an expert in cabinet modeling you will have to find a design that's been measured to be sure of what you'll end up with.

[wlb]

> You probably will. More to the point, unless
> you are an expert in cabinet modeling you
> will have to find a design that's been
> measured to be sure of what you'll end up
> with.
Thats what I figured. I was wondring how the sensitivity ratings were dirived. They don't seem very realistic. Thanks for the info.

[billfitzmaurice]

> Thats what I figured. I was wondring how the
> sensitivity ratings were dirived. They don't
> seem very realistic. Thanks for the info.

Sensitivity is measured with the driver on a standard baffle in an anechoic chamber, so the result is true half-space infinite baffle. That generally bears little resemblance to an actual cabinet much below 200 Hz at best. In the final analysis raw driver specs aren't what determines the end result, it's what the speaker designer does with it.

[deromax]

A few questions!

The sensitivity that is calculated in a simulation app would corresponds to what kind of measurement, infinite baffle or a regular box?

Anechoic or in-room?

The calculated value correspond to what? The average of the pass-band? The point that is 3 dB above F3?

Why can't manufacturers post the calculated value instead of some kind of made up value?

They advertise 91 dB, the calculation gives 89 dB and the real world actual measurement ends up like 87 dB!!

I find all this somewhat confusing!