99 replies to this topic

[Bassaholic]

Can everyone do me a big favor and ignore the sensitivity spec! Or at least make an attempt to understand it....

Bobby_Digital said:

why do you always need to move lots of air?
a higher power handling sub such as a RE/DD etc will mostly have a lower sensitivity cause of the heavy suspention it needs to keep it's control at large xmax. ($$ was used to make the suspention so good)  

put both on 200wrms the boston would probly be louder due to the lighter suspention (therfor higher sensitivity...  but you knew that )

Louder at what frequency? In what enclosure?

If you are talking about the sensitivity spec being higher in some subwoofers due to looser suspension, then you are mostly wrong.

If you are suggesting that subwoofers with a higher sensitivity spec are louder than those with a lower spec at all frequencies, then you are also mostly wrong.

If you had two subwoofers, with a very similar frequency response in a very similar sized enclosure then the volume will also be very similar. (assuming the same amount of power and that both subwoofers are atill operating in their linear range) If one can handle more power (in a relatively linear manner), then it will play louder than the other when given this extra power. Whether you actually need this extra volume, depends on the application and the values are relative...

Back to the original topic though, why verbal wankery?

Because it feels good!

[Bassaholic]

Blackrazor said:

That looks like a nice pole piece, where is the rest of the subwoofer?

[fuddbutter]

Bassaholic said:

Can everyone do me a big favor and ignore the sensitivity spec! Or at least make an attempt to understand it....

Bobby_Digital said:

why do you always need to move lots of air?
a higher power handling sub such as a RE/DD etc will mostly have a lower sensitivity cause of the heavy suspention it needs to keep it's control at large xmax. ($$ was used to make the suspention so good)  

put both on 200wrms the boston would probly be louder due to the lighter suspention (therfor higher sensitivity...  but you knew that )

Louder at what frequency? In what enclosure?

If you are talking about the sensitivity spec being higher in some subwoofers due to looser suspension, then you are mostly wrong.

If you are suggesting that subwoofers with a higher sensitivity spec are louder than those with a lower spec at all frequencies, then you are also mostly wrong.

If you had two subwoofers, with a very similar frequency response in a very similar sized enclosure then the volume will also be very similar. (assuming the same amount of power and that both subwoofers are atill operating in their linear range) If one can handle more power (in a relatively linear manner), then it will play louder than the other when given this extra power. Whether you actually need this extra volume, depends on the application and the values are relative...

Back to the original topic though, why verbal wankery?

Because it feels good!

ok ok.... im still learning here (it's only been 8 - 10 years)

so if a sub has stiffer suspention etc wouldent it need more power to move the cone to it's full excursion?
where as a sub with less resistance get there more easy of less power.
therefor the one that is pushing more air be louder.

or am i just losing the plot here? explain it to me....

[Blackrazor]

The other thing to remember is sensitivity ratings are at 1w, they dont always protray an accurate pic of what happens at 50w, or 200w, or 1600w, its not that simple... also sensitivity is (normally) measured in an anechoic environment in infinite baffle, which means it doesnt tell you how it will behave in a sealed box, or ported box, or horn loaded, or whatever

The fact that 85% of drivers on the market have some pretty BS sensitivity ratings doesnt help either

Check this out if you want to properly calculate your drivers sensitivity : http://www.adireaudio.com/Files/TechPapers...alculations.pdf

[HISPL]

Bassaholic said:

Blackrazor said:

That looks like a nice pole piece, where is the rest of the subwoofer?

Sitting on my workbench.

[Bassaholic]

The sensitivity spec is dominated by:

Cone area
Moving mass vs motor strength

(also remember that BL is relative to the Re, so more motor strength would be more BL for a given amount of Re)

Stiffer suspension will shift the parameters - as the stiffness increases, the VAS will go down and the Fs and Qes will increase. The stiffer suspension becomes a factor at around resonance.

[Bassaholic]

HISPL said:

Sitting on my workbench.  

I'm jealous!

[toman]

Blackrazor said:

The other thing to remember is sensitivity ratings are at 1w, they dont always protray an accurate pic of what happens at 50w, or 200w, or 1600w, its not that simple... also sensitivity is (normally) measured in an anechoic environment in infinite baffle, which means it doesnt tell you how it will behave in a sealed box, or ported box, or horn loaded, or whatever

The fact that 85% of drivers on the market have some pretty BS sensitivity ratings doesnt help either

Check this out if you want to properly calculate your drivers sensitivity : http://www.adireaudio.com/Files/TechPapers...alculations.pdf

umm I just ran this on the IDMAX 12" D2 and got 108.2669DB compaired to IDMAX's 93.2 quoted DB explain a lot?

[Blackrazor]

You did your calculations wrong

The Fs, Vas and Qes of the IDMAX 12D2, from ID's own data sheets are 27.4Hz, 95L, and 0.445 respectively.

That gives the driver an n0 (reference conversion efficiency) of approximately 0.00423, or about 0.423%, which in turn gives it an accurate 1 watt input at 1 metre measuring distance SPL sensitivity, of 88.27dB.

I've made it into an Excel spreasheet calculator and attached it if you'd like to check the maths... It's not 93.2dB let alone 108dB...

Trust me, if it was REALLY 108dB, then there wouldnt be one SPL competitor on the face of the earth using any other sub BTW, i'm not bagging ID at all, they do incredible gear, this is just to show that quite often companies tend to overrate their 1w/1m SPL a tad so, if its important you know it exactly, you need to verify it by the above process

Excel Spreadsheet Calc (just fill in the Fs, Vas and Qes of any driver you want to see the real 1w/1m SPL of) : http://www.audio-apex.com/files/sensitivity-calc.xls

[toman]

Blackrazor said:

You did your calculations wrong

The Fs, Vas and Qes of the IDMAX 12D2, from ID's own data sheets are 27.4Hz, 95L, and 0.445 respectively.

That gives the driver an n0 (reference conversion efficiency) of approximately 0.00423, or about 0.423%, which in turn gives it an accurate 1 watt input at 1 metre measuring distance SPL sensitivity, of 88.27dB.

I've made it into an Excel spreasheet calculator and attached it if you'd like to check the maths... It's not 93.2dB let alone 108dB...

Trust me, if it was REALLY 108dB, then there wouldnt be one SPL competitor on the face of the earth using any other sub BTW, i'm not bagging ID at all, they do incredible gear, this is just to show that quite often companies tend to overrate their 1w/1m SPL a tad so, if its important you know it exactly, you need to verify it by the above process

Excel Spreadsheet Calc (just fill in the Fs, Vas and Qes of any driver you want to see the real 1w/1m SPL of) : http://www.audio-apex.com/files/sensitivity-calc.xls

haha yeah I got to the 0.423% part right must have muffed it from there (****ty graphics calculator skills lol which is bad because i have a maths exam tomorrow )