[greatmana2000]

When a vehicle is parked in the sun I have seen that the speaker cones become a bit soft due to the heat and the cone flexes . Has anyone else seen the same ? Would speakers with plastic cones be best avoided ?

[DerAlte]

The cones in plastic-cone speakers flex to some extent even in cold weather. Good ones normally have metal-deposition on the surface to achieve some stiffness. In any case, even with cheap speakers the cone won't collapse until the ambient temperature is >70degC, at which temperature even the driver is likely to collapse!

One need not avoid plastic cones on account of cone flexing under hot weather conditions. There are some very good speakers which use metallized plastic cones - the 'plastic' incidentally is not plain old PVC, it is a better grade engineering plastic.

[greenhorn]

by that argument even paper speakers should be avoided, since exposure to moisture would damage them . forget the cone. I'm more worried about the suspension of the coil and the coil itself becoming warped. would they be negatively affected? have heard a lot of car speakers develop 'rubbing' noises over time

[navin]

Originally Posted by greenhorn

by that argument even paper speakers should be avoided, since exposure to moisture would damage them . forget the cone. I'm more worried about the suspension of the coil and the coil itself becoming warped. would they be negatively affected? have heard a lot of car speakers develop 'rubbing' noises over time

Paper cones are often "doped" with a material that makes them stiffer and a bit more weather resistant.

Another issue is that the glue that binds the coil to the terminals sometimes gives way.

Rubbing noises are often due to dust getting into the gap between the coil and the magnet. Some dust is bound to have high ferric content and this dust gets attracted by the magnet and then fills the gap between the magnet and voice coil.

These are the hazzards of car audio speakers and over the years manufcturers have made car audio speakers more reliable but it is difficult to change the enviroment itself.

[greatmana2000]

Originally Posted by DerAlte

The cones in plastic-cone speakers flex to some extent even in cold weather. Good ones normally have metal-deposition on the surface to achieve some stiffness. In any case, even with cheap speakers the cone won't collapse until the ambient temperature is >70degC, at which temperature even the driver is likely to collapse!

One need not avoid plastic cones on account of cone flexing under hot weather conditions. There are some very good speakers which use metallized plastic cones - the 'plastic' incidentally is not plain old PVC, it is a better grade engineering plastic.

I am talking about a car parked in the sun where the temperatures go beyond the 70 deg C . The cone , suspension has every bit of reason to go "soft " . Right now , I do not know the cone material used but do you have any info on the plastic material used ?

[greatmana2000]

Originally Posted by greenhorn

by that argument even paper speakers should be avoided, since exposure to moisture would damage them . forget the cone. I'm more worried about the suspension of the coil and the coil itself becoming warped. would they be negatively affected? have heard a lot of car speakers develop 'rubbing' noises over time

The "rubbing " noise tends to emanate from the positive and the negative signals being "fed" into the loudspeaker . Sometimes it is true that the + and the - attract towards each other .

[DerAlte]

Originally Posted by greatmana2000

I am talking about a car parked in the sun where the temperatures go beyond the 70 deg C . ...

Sir, I think you should take an infrared thermal profiler inside the car to see which areas are at 70degC!!! It is only the areas exposed to direct sunlight that reach high temperatures (anything on top of dash, steering wheel etc.). The speakers almost *never* get to see the light of the day in most mounting positions. Generally, in areas not receiving direct sunlight, the air/surface temperature exceeds ambient by max 5-10degC. Temperature around a speaker in the door is likely to be ~50degC in a closed car when outside temp is 45degC. 'Terribly uncomfortably hot' for a human does not necessarily translate to a hazardous environment for a speaker.

IMPP (polypropylene), imides, HOP (Highly Oriented Polyolefins), Laminar Polyester and Mylar are some of the 'plastic' materials used for cones. Even PVC does not melt till 100degC (depending on type, PVC melting point varies 10-260degC).

The usual suspects (of degradation in high ambient over a period of couple of years) are surround (if urethane) and the adhesives.

Originally Posted by greatmana2000

The "rubbing " noise tends to emanate from the positive and the negative signals being "fed" into the loudspeaker . Sometimes it is true that the + and the - attract towards each other .

Err... What are you talking about here?

[greenhorn]

Originally Posted by greatmana2000

The "rubbing " noise tends to emanate from the positive and the negative signals being "fed" into the loudspeaker . Sometimes it is true that the + and the - attract towards each other .

Sorry I don't understand. Is this some sort of a troll thread ?

[greatmana2000]

[quote=DerAlte;2746120]Sir, I think you should take an infrared thermal profiler inside the car to see which areas are at 70degC!!! It is only the areas exposed to direct sunlight that reach high temperatures (anything on top of dash, steering wheel etc.). The speakers almost *never* get to see the light of the day in most mounting positions. Generally, in areas not receiving direct sunlight, the air/surface temperature exceeds ambient by max 5-10degC. Temperature around a speaker in the door is likely to be ~50degC in a closed car when outside temp is 45degC. 'Terribly uncomfortably hot' for a human does not necessarily translate to a hazardous environment for a speaker.

IMPP (polypropylene), imides, HOP (Highly Oriented Polyolefins), Laminar Polyester and Mylar are some of the 'plastic' materials used for cones. Even PVC does not melt till 100degC (depending on type, PVC melting point varies 10-260degC).


The usual suspects (of degradation in high ambient over a period of couple of years) are surround (if urethane) and the adhesives.

I was talking with respect to dashboard mounted speakers .. I was also not talking about "melting " point . I was talking about temperatures at which the plastic tends to soften and lose its shape . In the case of a speaker it would be the "flex " that i am talking about .

[greatmana2000]

Originally Posted by greenhorn

Sorry I don't understand. Is this some sort of a troll threadAttachment 915667 ?

Oh! i was kidding .. You can hear the rubbing noise only when the speaker is playing ..

[DerAlte]

Originally Posted by greatmana2000

... I was talking with respect to dashboard mounted speakers ...

They are "in" the dashboard, protected by a grill, not "on" the dashboard. Unlikely to heat up as it is shaded by the grill.

Originally Posted by greatmana2000

... I was also not talking about "melting " point . I was talking about temperatures at which the plastic tends to soften and lose its shape ...

And the temp at which a material becomes soft and loses shape is not melting point?

Originally Posted by greatmana2000

Oh! i was kidding ...

You certainly are.

Originally Posted by greenhorn

... Is this some sort of a troll thread?

How perceptive, greenie!

[adityamunshi]

I had ground zero 6x9 coaxials mounted on the rear parcel tray and the area was constantly exposed to sunlight when parked at my house. Within a year and a half, both speaker cones became very brittle and pieces started falling off.

[greatmana2000]

Originally Posted by DerAlte

They are "in" the dashboard, protected by a grill, not "on" the dashboard. Unlikely to heat up as it is shaded by the grill.

And the temp at which a material becomes soft and loses shape is not melting point?

I thought melting point was where a solid "melts" or changes the state of solidity . I am talking about the plastic material becoming "softer " due to heat . I think you have some serious issues understanding ,because in the other threads also , you kind of tend to talk about something not relevant or something which has no relationship to what the discussion is all about . I was just trying to see if anyone has experienced the softening or as the previous poster posted about ground -zero speakers which became brittle .

Even with the grill covered the "air " around the grill would certainly be hotter and may be the hot enough to soften . I have seen the dashboard themselves "flex " or become "soft " due to sunlight .

[DerAlte]

Originally Posted by greatmana2000

I thought melting point was where a solid "melts" or changes the state of solidity . I am talking about the plastic material becoming "softer " due to heat . I think you have some serious issues understanding , ...

Whether I understand an issue or not, is besides the point - you seem to be getting personal in frustration. Please calm down.

On the other hand, you seem to be missing something that is taught in elementary physics in school - state change from solid to liquid around the melting point of a material. And yet you persist and go on and on without least understanding that 'softening' is the starting point of melting - like ice cream warming up.

Materials do not go from solid to liquid from one moment to the other, especially 'plastic' materials which are a mix of different chemicals. They first soften up, then reach flow consistency in a some minutes if the temperature stays at or higher than melting point. Please do read up on breakdown of crystalline structures and molecular matrices ('softening') around melting point.

I haven't seen plastic cones of even cheap speakers mounted in the dash board location in Wagon R or Indica, soften or go bad in 45-47degC temperature that one faces in Delhi, Haryana, Rajasthan etc. Most people who don't want to take a chance usually put a cloth cover on the dash, anything from towels to synthetic tiger skin patterned fur material! OTOH, many people have experienced gradual degredation (and ultimately failure) of surround material and adhesives at lower temperatures even in door mounting - but that is due to gradual loss of the plasticizer chemicals.

[navin]

Originally Posted by greatmana2000

Even PVC does not melt till 100degC (depending on type, PVC melting point varies 10-260degC).

Originally Posted by adityamunshi

I had ground zero 6x9 coaxials mounted on the rear parcel tray and the area was constantly exposed to sunlight when parked at my house. Within a year and a half, both speaker cones became very brittle and pieces started falling off.

Originally Posted by greatmana2000

second , softening is not the melting point . A plastic can soften at x degree , but to melt it might require even x+50 or may be even x+100 degree .

First lets look at the facts.

The ONLY parts of a speaker that is exposed to direct sunlight (on the dash or rear deck) is the grill, cone, surround and a bit of the basket.

Modern speakers often have plastic baskets and grills (when the speakers are built to a price point). These are usually ABS.

Most "plastic" cones are variations of polypropene

Most car speakers have rubber surrounds (foam does not last even half as long). These are usually butyl rubber. In cheap speakers these are often foam and the foam surrounds dont last more than 2-3 years.

Other than the foam surrounds, the part that is most suspetible is the rubber (butyl) surround and the glue that holds the rubber surround to the basket and cone.

In the 35 odd years I have played with speakers I have never seen the plastic cone of a speaker get damaged just due to cabin heat. The worst case was a local Bolton make 8" woofer I had in the 80s that I had accidently kept over night in the car and only realised this in the afternoon on the 2nd day. Even in this speaker the cone was not damaged.

India is not the only country with harsh climate. States like Arizona and Florida in the US can get as hot and humid as India.

Both ABS and PP can withstand tempretures higher than 70 degrees without any degradation. ABS I think can go to 100 deg and PP to over 150deg. Google the details if you need to know more.

In the old days (70s and 80s) the type of plastic they used for car grills probably was poor. I remember seeing some dash speaker grills and air-conditioner vents which were made of a plastic which curled and buckled at salvage yards. In the 70s some car manufacturers (at least these 3 - GM, AMC, Chrysler) used a sorts of plastisied leather for the dash cover (we used to call it pluther) . This covering would deteriorate and peel and even bend but over 10 years or more in the southern states.

In short UV light is more liable to damage your speaker or any plastic parts in the car than heat.