Effect of humidity on Speaker response

[Tanmay Mehta]

My speakers were Audyssey calibrated on my Denon X2200W in dry weather and was happy with the results. It rained yesterday, its still quite humid today at 75+%. Now I find my bass response of my Pioneer SW-8mk2 (Andrew Jones sub) has increased substantially - I'm currently being forced to set SW to -9 dB! This is true for all the other speakers (Jamo) Only dynamic EQ is on. I've had this situation in the past too when humidity levels were high. Any ideas on why is this happening?

 

[TLS Guy]

My speakers were Audyssey calibrated on my Denon X2200W in dry weather and was happy with the results. It rained yesterday, its still quite humid today at 75+%. Now I find my bass response of my Pioneer SW-8mk2 (Andrew Jones sub) has increased substantially - I'm currently being forced to set SW to -9 dB! This is true for all the other speakers (Jamo) Only dynamic EQ is on. I've had this situation in the past too when humidity levels were high. Any ideas on why is this happening?

What are your speaker cones made of?

This is a reason I DO NOT use paper cones living on the lake here. The humidity can get very high in the summer.

 

[lsiberian]

What are your speaker cones made of?

This is a reason I DO NOT use paper cones living on the lake here. The humidity can get very high in the summer.

That's an interesting problem to have. I'd be concerned of greater wear on the surround due to the increased weight of the humidity.

 

[Swerd]

My speakers were Audyssey calibrated on my Denon X2200W in dry weather and was happy with the results. It rained yesterday, its still quite humid today at 75+%. Now I find my bass response of my Pioneer SW-8mk2 (Andrew Jones sub) has increased substantially - I'm currently being forced to set SW to -9 dB! This is true for all the other speakers (Jamo) Only dynamic EQ is on. I've had this situation in the past too when humidity levels were high. Any ideas on why is this happening?

I'd be surprised if changes in relative humidity or atmospheric pressure, due to normal variations in weather, could make such a large difference. I could be wrong, but I'd be very surprised. Accidentally moving your subwoofer, or sound meter, just a silly inch or two, could easily have been the reason why.

Write down all the settings that Audyssey determined when the relative humidity was 75%, keep them, and do it again when the weather is drier, when relative humidity is less than 50%. You'll be able to answer your own question.

Remember that most tools that measure relative humidity are not precise. They usually read relative humidity ±5%, as long as you are reading above about 10-15% and less than 90-95%.

 

[Swerd]

… I've had this situation in the past too when humidity levels were high. Any ideas on why is this happening?

In theory, this could happen only if high humidity made air denser. Humidity actually reduces the density of air:

https://en.wikipedia.org/wiki/Density_of_air#Humidity_.28water_vapor.29

"The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molar mass of water (18 g/mol) is less than the molar mass of dry air (around 29 g/mol). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume (see Avogadro's Law). So when water molecules (water vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases."

If your subwoofer's cone material is made of untreated or uncoated paper, as suggested by TLS Guy, it might absorb water vapor and become heavier. Coated paper, plastic, or metal cones should not be affected by humidity.

Otherwise, we don't have a clue why this is happening .

 

[TLS Guy]

In theory, this could happen only if high humidity made air denser. Humidity actually reduces the density of air:

https://en.wikipedia.org/wiki/Density_of_air#Humidity_.28water_vapor.29

"The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molar mass of water (18 g/mol) is less than the molar mass of dry air (around 29 g/mol). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume (see Avogadro's Law). So when water molecules (water vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases."

If your subwoofer's cone material is made of untreated or uncoated paper, as suggested by TLS Guy, it might absorb water vapor and become heavier. Coated paper, plastic, or metal cones should not be affected by humidity.

Otherwise, we don't have a clue why this is happening .

Actually thee is a lot of evidence that shows that humidity changes to have quite a profound and measurable effect on paper loudspeaker cones and even doped ones.

I doubt it has not been noticed that I never use paper cones in my loudspeaker designs, only metal and plastics for woofers. When I was in short pants I could easily hear the difference and Lowther drive units were most affected.

Here is an MIT study.

In the UK this has been known as a bad problem for years, and was a big reason that Raymond Cooke of KEF led the drive away from paper cones. He was especially adverse to paper as a cone material.

 

[rojo]

What are your speaker cones made of?

This is a reason I DO NOT use paper cones living on the lake here. The humidity can get very high in the summer.

This is an interesting idea. Do you think added weight of moisture in the cone will lower the Fs of the driver as well as raising its Qts, causing a hump in the response near the tuning of the box and the driver to exhibit less control / more ringing?

 

[TLS Guy]

This is an interesting idea. Do you think added weight of moisture in the cone will lower the Fs of the driver as well as raising its Qts, causing a hump in the response near the tuning of the box and the driver to exhibit less control / more ringing?

This is nothing new and has been known since the 60s. Humidity does change the weight of the cone and therefore Fs and changes the modulus of the cone.

Ted Jordan was senior design engineer at Goodmans, who had all doped paper cone drivers. This was one of the big factors driving Ted to pioneer aluminum cones. He was not the first though, that credit goes to GE believe it or not. Decca made a very decent speaker round the GE aluminum driver in the fifties.

This was Ted's brilliant solution.

He was so obsessed by fabrics and moisture he did not want a fabric suspension!

I listened to the whole of Bach's B minor mass on these in AV from a 2012 Prom Sunday night. These bookshelf speakers use just one of these 4" drivers per side. No tweeters, no sub, no crossover components. They sounded just gorgeous, beautifully smooth and detailed. Even more surprising the bass is excellent with the full range of the "organ positif" fully reproduced.

These speakers came out in 1959, yet in my view are up there with the very best of bookshelves that size available today. When it comes to loudspeaker drivers we have learned very little in nearly sixty years and in many ways regressed.

 

[Swerd]

This is nothing new and has been known since the 60s. Humidity does change the weight of the cone and therefore Fs and changes the modulus of the cone.

Thanks for pointing that out. It makes a lot more sense than any idea I mentioned above.

 

[TLS Guy]

Thanks for pointing that out. It makes a lot more sense than any idea I mentioned above.

Note that doping the cone changes its mass, by adding weight. However it did not change the huge weight gain and adsorption of water versus undoped significantly. The driver manufacturers would have us believe their "secret" doping solutions are perfect. I doubt this is true as these potions are all glue/varmish if one variety or another.

Now a lot of homes with HVAC do not have a lot of variation. Up here however we have enormous temperature extremes that cause huge seasonal humidity variations, which not living by water exacerbates.

I have taken the view that using paper cones would be a disaster up here.

This issue has been easily audible among audio enthusiasts in tropical regions, even resulting in driver failure.

I think this is one of the reasons why the Jordan Watts Driver was so popular in the more tropical regions of Asia. Those driver are still highly regarded and sought after today in those regions.

 

[Swerd]

Note that doping the cone changes its mass, by adding weight. However it did not change the huge weight gain and adsorption of water versus undoped significantly. The driver manufacturers would have us believe their "secret" doping solutions are perfect. I doubt this is true as these potions are all glue/varmish if one variety or another.

Coating a paper cone can be done with a variety of materials, for a variety of purposes. I've always thought it was to increase the stiffness of paper without adding a lot of weight and not to 'water proof' the paper. Paper can also be modified by adding various fibers to the pulp, such as glass, Kevlar, bamboo, etc. It's always kept secret, so it can be hard to generalize about it.

I quickly read that MIT student's paper, and looked over the figures. It is abundantly clear that there was a big difference between treated and untreated paper 8" diameter woofer cones (figures 7 & 8, pp 28-29) and as they were exposed to high humidity. It wasn't clear if there was a significant difference between treated paper and poly cones.

This resembles those silly debates about whether drivers must go through a break-in process. Someone usually points out that you can easily measure differences between Q and Fs before and after a break-in run of a woofer. But they never establish whether those measured differences translate to a significantly audible difference in sound. Perhaps the same goes for those differences between treated paper and poly cones. Are they significant differences? That engineering student didn't take it that far.

Also on the subject of humid weather, I know Dennis Murphy has a European-made piano (I don't remember the name) that requires a small electric heater mounted underneath it to keep an important wooden structure from changing dimensions too much as humidity increases. The humidity during the summer in the US is that much greater than in northern Europe.

 

[sterling shoote]

In theory, this could happen only if high humidity made air denser. Humidity actually reduces the density of air:

https://en.wikipedia.org/wiki/Density_of_air#Humidity_.28water_vapor.29

"The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molar mass of water (18 g/mol) is less than the molar mass of dry air (around 29 g/mol). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume (see Avogadro's Law). So when water molecules (water vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases."

If your subwoofer's cone material is made of untreated or uncoated paper, as suggested by TLS Guy, it might absorb water vapor and become heavier. Coated paper, plastic, or metal cones should not be affected by humidity.

Otherwise, we don't have a clue why this is happening .

You do know what's happening, the woofer is pushing air. The less density, the easier the push. Humid days are welcome in my listening room.

 

[Tanmay Mehta]

1) I haven't been able to find out the material of the cone for the sub (Andrew Jones Pioneer SW-8 mk2) - at its price point I would not expect anything extraordinary. It is a really good sub though.

2) The Denon X2200W uses Audyssey MultiEQ XT - it does not support viewing the waveform by default. If there is a way to view it I would grateful if someone could point me in the correct direction.

 

[Tanmay Mehta]

Is there any study or data available on what is likely to be most responsible - the changes in the cone, the air itself or the subwoofer box material+it's bracing?

I agree with what Sterling pointed out - humid days are indeed welcome.