Effects of Altitude on Speaker Frequency Response

[sal]

I'm pretty sure it is settled science that barometric pressure has a direct effect on sound. Might a speaker that measures well in New Orleans not do so well in say Denver, specifically in the bass department?

What, if any, are the industry standards for measuring frequency response in speakers in regards to altitude?

 

[puppet]

I'd think that the individual responses would be relative to the environment. While "NO" would measure differently than "D" when compared to each other ... either response characteristics, by themselves, would be essentially the same.

 

[sal]

I'd think that the individual responses would be relative to the environment. While "NO" would measure differently than "D" when compared to each other ... either response characteristics, by themselves, would be essentially the same.

Are you sure? That implies that the relationship between pressure and frequency is linear. Is that actually the case?

 

[blueone]

https://www.stereophile.com/asweseeit/590awsi/index.html

 

[sal]

https://www.stereophile.com/asweseeit/590awsi/index.html

Good read, TY. So it sounds like it depends on driver type and that there is 'something' to this, albeit very small. Not enough to throw a system out of balance

 

[blueone]

Good read, TY. So it sounds like it depends on driver type and that there is 'something' to this, albeit very small. Not enough to throw a system out of balance

That's my experience with the Salon2s, moving them from a house at 1000 feet of elevation to one at about 6200 feet. The rooms are different, of course, and the two houses have different construction, but I haven't noticed a character change, if I may use that term, in the Salon2's sound.

 

[puppet]

Pressure density would have an effect on the speed of sound. I don't see pressure variations effecting frequency cancellation or attenuation ... which would be necessary to achieve a different, relative, frequency response in Iowa vs Pikes Peak.

Doesn't that article reflect "local" phenomenon? Individual response characteristics shouldn't change between location A vs B.

 

[sal]

Well, I have to say that though I accept the science for what it is, it still seems counter-intuitive to me.
It seems to me that a 12" woofer is moving a lot more air than a 1" tweeter. As such, the woofer's mechanical efficiency (and at some point frequency response), is more greatly affected by air density.

 

[NTK]

Well, I have to say that though I accept the science for what it is, it still seems counter-intuitive to me.
It seems to me that a 12" woofer is moving a lot more air than a 1" tweeter. As such, the woofer's mechanical efficiency (and at some point frequency response), is more greatly affected by air density.

Sound pressure level is a measure of the power (energy per unit time) transferred into air (as pressure waves) by the motion of the speaker diaphragm. Energy (or work) is force times displacement, and if we count energy per unit amount of time (i.e. 1 second), we get power.

Comparing a woofer moving at say 20 Hz to a tweeter moving at 2 kHz, the tweeter cycles back and forth 100 times more than the woofer. So the travel of the diaphragm doesn't tell the entire story. It must also be multiplied by the frequency (number of repetitions).

Moreover, force is mass times acceleration. Thus, the higher the frequency, the higher the acceleration and therefore the higher the force (derivative of sin ωt = ω cos ωt).

Combining both effects, the amount of power transferred into the air, when diaphragm travel and diaphragm area are kept constant, increases with the square of frequency. This is why we can have small tweeters with less diaphragm travel producing the same SPL at high frequencies as large woofers at low frequencies, as both transfer the same amount of energy into the air.