ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Dear members,
at which temperature does it become critical for speakers, i.e. one has to expect increased wear or damages, e.g., to the rubber or foam? Stated differently, which area is entirely uncritical?
Greetings,
Kai
That's an interesting question Kai.
Hopefully, Geoff Martin may have some input on this one - though he will concentrate on sound rather than component durability.
There must be a min and max limit for the different materials be it foam or rubber before they deteriorate more quickly or fail altogether. UV will also be another factor as will salinity and humidity, especially if near the ocean.
I have speakers in a sun room which experience a lot of sunshine, minimum temp of -5°C to a max of 50°C which haven't failed yet. They are Beolab 6000's, CX100's, Pentas and S50's.
They must be designed with tolerances in mind but the 'uncritical' temp will just be normal ambient temperature range - but that varies depending on where you are in the World!
I'll watch the answers from materials scientists with interest
Dave.
Manbearpig: at which temperature does it become critical for speakers, i.e. one has to expect increased wear or damages, e.g., to the rubber or foam? Stated differently, which area is entirely uncritical?
Hi Kai,
There is no one answer to your question. It really depends on the characteristics of the particular component you're talking about. If you're talking about a loudspeaker driver, then the first thing to worry about is the voice coil. Typically, this can reach something like 160-180 deg C (the actual number depends on the specific brand and model of driver) without needing to worry about it. The problem is that you can't measure it directly, since a voice coil sensor would make the voice coil stop working.Normally, we measure the temperature of the magnet and calculate the voice coil temperature using a thermal model of the system in real time using the amount of heat the magnet and assembly can "pull" out of the voice coil, and the amount of power we're pushing into it.
Other areas where thermal limits are an issue are the components on the amplifier and power supply boards.
See this posting and this posting for more info on how we deal with this in our products. Note that, in the second of those, you can see the actual (calculated) temperatures of the voice coils in a BeoLab 5 when we're pushing it pretty hard...
To answer the rest of your question, the mechanical suspension parts (i.e. the surround (whether rubber or foam or something else) and spider) will not be the cause of a thermal limit of a loudspeaker driver. They will contribute to the excursion limits. If you have put enough power into a driver to melt the dust cap, diaphragm, surround, spider or surround (see this posting for a drawing explaining these parts) then your voice coil has already melted.
Cheers
-geoff
Thanks very much for the insightful responses. When initially asking I was more thinking about the outside temperature in a room rather than temperature developing from pushing speakers or in general Hi-Fi components. Since I live right under the roof and it's getting pretty hot right now, I was a little worried that some of my B&O stuff might not like the high temperatures. I do not expose any of my equipment to direct UV radiation, but temperature can go up well above 30 degree Celsius with a max of about 40 degree Celsius. I think to remember that in the manual of the old Beocenter 1 it was said that 41 degree Celsius was the upper limit. However, I'm a little worried that the rubber used in the speakers might melt or otherwise change already earlier.
Manbearpig: Thanks very much for the insightful responses. When initially asking I was more thinking about the outside temperature in a room rather than temperature developing from pushing speakers or in general Hi-Fi components. Since I live right under the roof and it's getting pretty hot right now, I was a little worried that some of my B&O stuff might not like the high temperatures. I do not expose any of my equipment to direct UV radiation, but temperature can go up well above 30 degree Celsius with a max of about 40 degree Celsius. I think to remember that in the manual of the old Beocenter 1 it was said that 41 degree Celsius was the upper limit. However, I'm a little worried that the rubber used in the speakers might melt or otherwise change already earlier.
Hi again Kai,
Ah! I misunderstood your question. Consider that it would not be usual for the air temperature inside an active loudspeaker to reach something on the order of 70 or 80 deg C. So, 40 deg on the outside is cool by comparison - and your surround is exposed on both the inside and the outside.
So, until you move your loudspeakers into a sauna, you don't need to worry. :-)
Hi Geoff,
It was very easy to misunderstand and not being a native speaker I was quite uncertain how to put the question appropriately already in the first place. However, since both aspects are of interest it is even better this way. Thanks a lot, Geoff. And - as so many others have already pointed out before - your contributions to this great site are highly appreciated. I've got quite a bit of B&O gear and it is by far my favorite consumer electronics brand.
I don't think most home environments, outside of perhaps Death Valley, get hot enough to damage most drivers, but the real torture chamber is the automobile. In a sunny clime interior temperatures of a closed up auto can get to 140 deg and higher pretty easily and quickly. Add to that it's a long term temperature soak, for hours, and that is the most challenging environment for "consumer" products I think.
Fortunately the materials must be well thought out, I've not seen a heat damaged (as in glue/adhesive failure) in a car speaker for a long time now, and that was on cheaper import stuff from the Far East. I've never personally seen heat damaged home speakers. I have seen them that have been damaged by heat from overdriving them, burned voice coils and such, and definitely damage from overdriving past the excursion limits, but no ambient temp damaged ones.
Jeff
I'm afraid I'm recovering from the BeoVirus.
The "good" automotive audio manufacturers take this into consideration, of course. That's one of the reasons why you don't find loudspeaker drivers from domestic loudspeakers in automotive systems. Another reason is, as someone once told me back when I worked in B&O's automotive division: if you put a "normal" woofer in the door of a car, and you're in a side-impact collision, it would not be surprising for the magnet to rip away from the basket of the driver, shoot across the car, and cut your legs off...