Reference volume is defines as "the volume of air that, when compressed to 1 cubic meter, exerts the same force as the as the compliance (Cms) of the suspension in a particular speaker."
My question is, if the value for this changes with temperature, humidity, altitude, and the phase of the moon, why bother measuring it? 99% of the time, the operating conditions for the speaker will not be those measured in the lab. I live in Salt Lake City, which rests at about 3000' in the air--I'll never experience lab conditions, unless a freak high-pressure zone rolls through! I haven't yet heard of people complaining that their speaker sounds harsher at 80 degrees than at 76, so is there any point to the precision given to this parameter?
The next question, then, is: what happens if you run your party in a pressure chamber cranked up to, I dunno, 10 atmospheres? Does your efficiency go up? Does the frequency response change? Are horns as worthwhile? Is it even feasible to run a party in a big compression chamber? Or is there too much risk of giving people the bends?
My question is, if the value for this changes with temperature, humidity, altitude, and the phase of the moon, why bother measuring it? 99% of the time, the operating conditions for the speaker will not be those measured in the lab. I live in Salt Lake City, which rests at about 3000' in the air--I'll never experience lab conditions, unless a freak high-pressure zone rolls through! I haven't yet heard of people complaining that their speaker sounds harsher at 80 degrees than at 76, so is there any point to the precision given to this parameter?
The next question, then, is: what happens if you run your party in a pressure chamber cranked up to, I dunno, 10 atmospheres? Does your efficiency go up? Does the frequency response change? Are horns as worthwhile? Is it even feasible to run a party in a big compression chamber? Or is there too much risk of giving people the bends?
Nappylady said:
The ratio of reference volume, (Vas), to box volume, (Vb) determines how Fs is affected when the speaker is placed into a box. For instance, a speaker with a Qts of .38 will have an F3 equal to Fs in a properly tuned bass reflex enclosure. It will have an optimum value of 1.4 Fs when placed in an enclosure that is half it's Vas.
The air pressure one mile up is 87% that of sea level. If Salt Lake City is about half a mile up, then we would expect the pressure to be about 93% of sea level. When it comes to speakers, varying the box size by 10% rarely produces important changes. So you are well within the Comfort Zone.
Finally, there is no good reason to measure Vas to thousandths of a cubic foot or liter. It's just that Vas can either be measured directly, or computed if other parameters are known. The three places after the decimal point specs are the calculated specs. It would indeed make more sense not to publish such a precise spec, especially since few speakers match the other parameters with any precision.
Dunno. Throw your next party on Jupiter and let us know how it turns out. 😉
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