Definitive: Cold weather = lower output

[Lakota 5,000+ posts]

You all are arguing over something really stupid, seriously.

Not all cars gain SPL in the cold. Some do, some don't. I know that I lose a little score.

Get out in the real world and see how it affects competitors cars. Quit arguing over who has the biggest theory penis.

Simple as that.

 

[brynm 10+ year member]

I've worked with 3 conductor 750mcm teck cable at sub zero temps, it is more difficult to bend, but you can still bend it. You might have trouble with the insulation cracking, if it's not suited for cold temps, on a 12 AWG wire due to the cold but you will still be able to bend it easily at -50. I'm not saying my subs sound exactly the same at that temp but I definitely have no problem hearing frequencies below 200Hz.

 

[Kyle_Keating 10+ year member]

That's just ignorant.. The reduction in resistance doesn't have ANYTHING to do with the lower output - but rather the T/S parameters of the speaker itself changing.
At 0 degrees, Zaph cannot calculate T/S parameters for that speaker at 0 degrees because there is NO impedance peak. Resulting in ZERO bass output below 200 Hz.

I'm really ignorate in real life, I dont understand, whats a T/S parameter? and what an impedance peak?

 

[Kyle_Keating 10+ year member]

See the quote below.


Zaph is very respected among the DIY community and his study shows that at 0 degrees, his woofer in review has almost zero output below 200hz, whereas 110 degrees plays the lows with authority.

you know............ Being the ignorant person i am, you might want to consider that colder voice coils have lower resistance and........

if you lower the Dcr, then you increase the BL^2/Dcr. If you increase that ratio you increase the electrical dampening which then in turn decrease the low end bass response. And then you're woofer makes no bass, at least in a sealed box...

 

[Kyle_Keating 10+ year member]

I took a look......

http://zaphaudio.com/temp.html

So here is a problem....... he put 5.9 ohms for a 110 degrees and 0 degrees... that's not possible unless that voice coil was not aluminum or copper or the speaker was not the temperature of the room.

What is happening is really not *that* interesting, all that is occurring is the glues (for example) in the spiders are freezing up and bonding which in turn raises the Fs which increases the Q.

the SPL should be increase too, but the guy did not remeasure the voice coil so there is an error on that number.

EDIT. the Dcr at 0 should be ~5.4 ohms and the Dcr at 110 should be ~6.4 ohms which will reflect about a 9% BL shift.... not large but not negligible. The real changes are then obviously with the softparts and softpart chemical compliance changing with temperature.

blah..... anyway, who ****ing cares.

 

[John_E_Janowitz 10+ year member]

Wow, 9 pages on this. There are two things going on that affect any driver at various environmental conditions. Compliance will vary with temperatures and humidity and resistance of the coil will change with temperature.

First lets look at Cms. This is the compliance of the driver. The materials chosen for the suspension will determine how much this value can vary. In general, foam surrounds have less variance with temperature than do rubber surrounds. It also depends greatly on the type of rubber. Natural rubbers can often get very stiff at colder temperatures and often have issues with cracking. I had a chart at one point to show the working temperature range of different rubber materials, but can't find it at the moment. This page talks about some gasket materials that apply as well. http://www.sealsfast.com/pages/materials/materials.html

NBR has a brittle point of -22F meaning it will crack and can shatter at any point below that. Also as you are approaching those temperatures it will get increasingly stiff. EPDM is a thermoplastic elastometer which is good to -49F. Santoprene has a working range of -81F to 275F with no cracking or tackiness. This makes it the most reliable of rubbers and it is also going to be the least affected by cold temperatures. It also happens to be the most well damped as well. The combination of damping and temperature range is why we use it for our AV series.

That all said, you need to look at the effects of compliance changing with temperature. As the suspension gets stiffer, Fs goes up, Q goes up, and Vas goes down. The change this gives will depend on the type of enclosure. In a sealed enclosure this means that Qtc goes up and the Fc point goes up. Below Fc you will begin to lose some output due to the stiffer suspension. You can model the effects by cutting Cms in half and seeing what happens in your enclosure. Keep in mind that this won't be exactly a linear loss either. As flexibility is lost in the surround the effects will be higher at larger excursions as more of the surround is required to move. This means the overall loss of output can be more than the model would suggest at higher levels. In the following graph you can see the results on the impedance curve and response when effectively doubling the stiffness of the AV12H suspension in a 1cf sealed enclosure.

In a vented enclosure it is a little different. Due to multiple peaks in the impedance curve you end up with some points of higher output and some of lower output. The following graph shows an AV12X in 2cf tuned to 30hz. The blue curve is with the stiffness of the suspension doubled. You can see that at the points where the impedance curves cross is where you will see a transition from one driver having more output than the other.

Now the other change as mentioned is in the resistance of the wire. As the temperature goes down, so does the DC resistance (Re) of the driver. The motor strength of a driver is typically stated as Bl^2/Re. The B is the amount of flux in the gap measured in Tesla and L is the length of wire in the gap measured in meters. As you change the Re of the driver due to temperature, the B and L will not change. As temperature lowers so does Re and as a result your motor strength goes up. On the other hand as temperature goes up, so does Re and motor strength drops down. This is one of the variables that is difficult to account for and part of the reason many SPL competitors believe you cannot believe what a simulation will claims possible. Not only does the motor strength drop, but as resistance rises, your amplifier now cannot deliver as much power to the driver. This is known as power compression.

Now lets take a look at what would hypothetically happen if the same sealed and vented enclosure comparisons were to happen with something like the NBR or butyl rubber that can get extremely stiff as it approaches it's brittle point. This shows the combined effect of higher motor strength as well as the extreme rise on stiffness of the suspension. The green is the original driver in both applications.

You can see that the lowering of DCR and more motor strength give more efficiency and output up higher, but the extreme stiffening of suspension causes for some serious loss in output at the real useable frequencies. There is a lot to be said for proper selection of materials for a given temperature range.

John

 

[ric flair 10+ year member]

dammit, when it is 5 degrees and your car has been outside for a few hours, you will experience much lower output. It doesn't matter.

 

[roarzorz 10+ year member]

No way I'm going back to read all that jibberish. Yes cold does effect spl. It effects different setups in different ways. I know for a fact that the colder weather will cause setups to peak at a lower frequency. Some people it doesn't effect much but others will see huge loss. Two days ago in 30* weather I was 1db down from my scores today in 49* weather with no other changes at all. I've also been to several comps and seen other guys anywhere from 0.5-1db down from the colder weather. Some spl competitors even use heaters (and in hot climates air conditioners) in their cars to maintain a specific temperature.

 

[Lakota 5,000+ posts]

No way I'm going back to read all that jibberish. Yes cold does effect spl. It effects different setups in different ways. I know for a fact that the colder weather will cause setups to peak at a lower frequency. Some people it doesn't effect much but others will see huge loss. Two days ago in 30* weather I was 1db down from my scores today in 49* weather with no other changes at all. I've also been to several comps and seen other guys anywhere from 0.5-1db down from the colder weather. Some spl competitors even use heaters (and in hot climates air conditioners) in their cars to maintain a specific temperature.

Nice to see someone that has been in the real world.

 

[John_E_Janowitz 10+ year member]

While it is clear just by listening that there is a decrease in output in cold weather, it is good to understand why it happens. Once you know the causes, you can also see ways to minimize the effect. In this case, the only real way is by choosing drivers that use a surround material that is more appropriate to climate changes. In this case santoprene has the best range of operating temperatures, is also most chemically and UV resistant, and the most well damped. It's only real drawback is cost vs other materials like NBR.

John