Temperature Control In Speaker Measurements

[Blumlein 88]

Mil-spec speaker video of torture tests. (Klippel isn't one of the torture tests).
https://military.technomad.com/videos/


https://store.miscospeakers.com/4-inch-voice-communication-speaker-ls445-u
Mil-spec speaker used in CS5 super galaxy transport planes.

 

[andreasmaaan]

I should clarify re: my post above where I fiddled around with the Qms/Rms of a driver, I don't think you can read too much into the outcomes, as changes in the suspension would also have effects on other TS parameters, most notably Vas.

 

[j_j]

My room is currently 78F and 46% relative humidity.

It will not range according to military requirements.

Ever.

By my estimation.

What? Why not cool it down to 10C and see what happens

(yes, I'm kidding)

 

[RayDunzl]

What? Why not cool it down to 10C and see what happens

Because the AC is 16 years old?

Excessive humidity (no numbers to quote) will dull the high frequencies (measurably) that I can't hear a measurable amount (electrostats).

 

[j_j]

Because the AC is 16 years old?

Excessive humidity (no numbers to quote) will dull the high frequencies (measurably) that I can't hear a measurable amount (electrostats).

I was of course joking, but in fact, humidity does have an effect on high frequency transmission, and sometimes a rather substantial one.

http://www.sengpielaudio.com/calculator-air.htm can offer quite a bit of interesting data.

Try 20% vs. 50% at 10khz and 20C. Yes, that's a difference. If you look at higher frequencies that people of our age don't experience much any more, this also has a very interesting read on the arguments about the bandwidth requirements of recording systems in places like auditoriums, too.

 

[KSTR]

Excessive humidity (no numbers to quote) will dull the high frequencies (measurably) that I can't hear a measurable amount (electrostats).

It's not intuitive but lower humidity has higher HF damping.

 

[j_j]

It's not intuitive but lower humidity has higher HF damping.

Until you get to really, really low humidity, of course, like 5% where it goes back up. That's desert-level dry, though.

 

[Thomas savage]

OK, here you go:
View attachment 50764
The room temperature control woofer is the white sweep.
The other sweeps are the "cold" woofer coming up to room temperature (24.1 degrees at the time).
Yellow is 10 degrees C
Purple is 13 degrees C
Red is 17 degrees C
Green is 20 degrees C

As you can see, the resonant peak is lower in impedance and higher in frequency when cold, and increases in impedance and heads closer to the room temp woofer as it warms up.

Essentially as expected. The spider and surround become more pliable as they warm up. I cannot see how similar winter temperatures in a cold garage wouldn't affect low frequency tuning or bass output to some degree.

I've got tons of speakers and a spare fridge downstairs...

Ooo some practical, I like this .

 

[Xulonn]

This thread reminds me of the phrase on a favorite bumper sicker from many years ago:

 

[scott wurcer]

What does that have to do with anything? Speakers are used indoors so the reasonable temp range is what indoor temps would be, not milspec.

Sorry that didn't come across like I meant, just trying to say there are some errors bars on any measurement. Just curious, especially around the RH.

 

[hardisj]

Based on what I've seen and read this seems like a pretty cut and dry topic (no pun intended):

Issue 1 : Extreme temps can alter the suspension of a drive-unit and it stands to reason frequency response would be impacted
Remedy: Run the speaker at a medium-to-high output for some reasonable time (maybe 30 minutes) to loosen the suspension up and "prime" the speaker. May only be necessary if ambient conditions are outside typical listening conditions.

Issue 2: Temp and Humidity can affect the high frequency response *at >> distances*
Remedy: Don't measure hundreds of meters away


Just my $0.02

 

[NTK]

One aspect haven't been mentioned is the effect of temperature on the speed of sound. Speed of sound in air is proportional to the square root of the absolute temperature. At 20°C, an increase or decrease in temperature of 6 °C will increase or decrease the speed of sound by 1%.

A change in the speed of sound will change the wavelength. It will have some effect (likely very minor) on the lobing characteristics of speaker.

 

[DonH56]

Altitude also has an impact. My house sits at 7500', so I think @amirm should bring his camper and repeat all his tests in my garage just to make sure all the bases are covered. We also range from maybe -20 degF to 90+ degF over the course of a year, and humidity tends to be low single-digits to <20% except in rain or snow storms, so seems like the perfect place for a wide range of tests.

Whilst we could encourage all sorts of science experiments, we have to remember his time (and patience) is not infinite. It would be interesting to know roughly what sort of temperature range is likely, say from dead of winter to heat of summer, realizing measurements may not be taken when the shiver or perspiration factor of the tester is too high...

 

[j_j]

Altitude also has an impact. My house sits at 7500',

Do you have O2 tanks for us lowlanders?

More seriously that should alter the effects of ports, box compliance, etc, to a measurable extent.

 

[restorer-john]

Do you have O2 tanks for us lowlanders?

No, but Don has an inbuilt 10% delay in the speed of sound. He can make adjustments to the sound before you can even hear it.

 

[j_j]

One aspect haven't been mentioned is the effect of temperature on the speed of sound.

That was demonstrated very clearly when I did the "FFT tutorial". I did some (acoustic) TDR measurements in a hallway that was at about 45F. They were a touch off. Yep.

 

[DonH56]

Do you have O2 tanks for us lowlanders?

More seriously that should alter the effects of ports, box compliance, etc, to a measurable extent.

It also affects the tuning of my horn, not to mention (and so I shall) the windpower needed to play it!

No, but Don has an inbuilt 10% delay in the speed of sound. He can make adjustments to the sound before you can even hear it.

Now, that I like! Unfortunately I've gotten slower in my old age... But I can say "What? What'd you say?" faster than ever!

 

[j_j]

It also affects the tuning of my horn, not to mention (and so I shall) the windpower needed to play it!

Hmm. (bites tongue) Yes, it should.

Now, that I like! Unfortunately I've gotten slower in my old age... But I can say "What? What'd you say?" faster than ever!

"eh?" with a hand over one ear is very quick.

 

[Dave Zan]

It's not intuitive but lower humidity....

Until...really, really low humidity...

I also found the increase in loses at low humidity counter-intuitive so I researched it a little.
Then I learned about the reversal at very low humidity and was even more surprised.
Anyone have any kind of intuitive explanation for this?
I believed I had a reasonable physics education but I have no idea how this works.

David

 

[j_j]

I also found the increase in loses at low humidity counter-intuitive so I researched it a little.
Then I learned about the reversal at very low humidity and was even more surprised.
Anyone have any kind of intuitive explanation for this?
I believed I had a reasonable physics education but I have no idea how this works.

David

I believe it has to do with collision rate between water molecules (remember, they are bent, not straight molecules, so they have 3 moments). It has, however, been approximately since 1973 that I thought about this in detail.