I only tested once the 4 inch underhung voicecoil of a JBL speaker. In free air it started to smoke quite quickly with only something like 10W or so, in free air and disintegrated eventually after some 10-20min. In operation, in the speaker, depending on consruction, it is cooled by movement of air, and radiation to the heatcapacity of the magnet assembly will sure be of help to average out peaks, but i really could not say by how much and in what timeframe. Fact is, most of the input power gets converted into heat and the heat capacity of the coil itself is quite small. But dont worry, i find it very unlikely that even prolonged high power operation at home will get it up to 200 deg. But even as low as only 25 deg temp increase would increase dcr by 10%, lower efficancy, increasing power demand for same spl, rising temp even more....rise Qes, longer settling time....you get the picture?
BTW; neo magnets permanently lose magnetization as low as 80°C; ferrite is good to 250°C. Either way, 200°C is inadvisable.
https://www.supermagnete.de/eng/faq/What-temperatures-can-magnets-withstand
https://www.supermagnete.de/eng/faq/What-temperatures-can-magnets-withstand
When I worked at Altec Lansing nearly 30 years ago, they had a pro audio product (I wish that I could remember its name) that monitored bass content in the signal and, based upon an estimate of the thermal coefficients of the motor system, adjusted the EQ accordingly.
Technically, the statement that neodymium "magnets permanently lose magnetization as low as 80°C" is correct, but loudspeakers normally use neodymium iron boron alloys with terbium and dysprosium, rare earths necessary for neodymium magnets that require high heat resistance. Formulations with working temperatures of around 240C, comparable to ferrite magnet formulations are typical for transducer use.
The Altec Lansing model 1721A limiter didn't adjust EQ, but could be used to limit signal to below the thermal limits of a driver:
https://greatplainsaudio.com/wp-content/uploads/2017/07/1712A-All.pdf
Many DSP (digital signal processors) now have Dynamic EQ, adjusting the energy in a user defined frequency range based on incoming signal strength relative to a variable threshold, automating the intensity of boosts and cuts depending on the frequencies of the incoming signal.
Dynamic EQ can be used for speaker protection, or even as a variable "loudness contour" to keep relative loudness equal at low volume listening, reducing LF content as SPL increases.
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They knew what they are doing, but considering stuff like that is propably to overcomplicated for some...
Depends on its design, so maybe 1 W @ 10 min sustain or 1 W @ +30 dB @ 0.1 sec/1000 W transient peak (made up numbers) since heat rise is exponential.
One of my faves too! Not as challenging as some pipe organ symphony recordings, but IME with a stereo pair of corner loaded dual 30 W Altec 515B ~14 Hz pipe horns XO'd @ 500 Hz hooked to a 400 W Altec Studio amp and cranked to near live SPLs ('fast' transients pegged my RS meter) 'we' could (long ago now) hear the deep bass line beginning to 'flatten out' almost instantly from VC heating, but thankfully these were made back when they were built to 'take a lickin' and keep on tickin' 😉 (old Timex watch ad) for decades in a large cinema app with little/no maintenance, so have yet to need any re-cone, at least from this kind of abuse, but having set still for nearly 23 yrs now? 🙁 👍
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A safe assumption IME. 😉
Not really since the lower the frequency, the wider its BW and supposedly our brain can/will reconstruct what we don't hear at least to some extent plus we are still 'feeling' it in/on our bodies.
As an experiment, I've been running a 60W incandescent light bulb for the last 10 minutes. According to my infrared thermometer, it comes in right at 95°C. So I think that your estimates are off by a couple orders of magnitude.
@Davey well I already have it in my minidsp so
I appreciate the help though
every time I post a thread here I leave with more questions than when I started
I appreciate the help though
Temp measurements are so easy nowdays, but infrared measurung glass temperatur is a bit unreliable, just a few days ago it was more than
minus 20 deg C outside and i wanted to know if my well is in danger of frezzing up and needs heating. So i let water running into a drincking glass for a long enough time to make sure i measure the correct water temperature. Supricengly, my infrared showed 4 degrees beyond freezing point, lol.
minus 20 deg C outside and i wanted to know if my well is in danger of frezzing up and needs heating. So i let water running into a drincking glass for a long enough time to make sure i measure the correct water temperature. Supricengly, my infrared showed 4 degrees beyond freezing point, lol.
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Given the large amount of posts re. driver 'motor temperature',
I thought I would mention > intended & desired SPL levels are very relevant to the subject.
As you all know, a simple 3dB boost is double the power dissipated.
So, if very high levels are intended, you ought to get the best speaker/box output you can before EQ.
If only moderately high levels are required, then EQ 'your heart out' > Class D now makes that easy 🙂
I thought I would mention > intended & desired SPL levels are very relevant to the subject.
As you all know, a simple 3dB boost is double the power dissipated.
So, if very high levels are intended, you ought to get the best speaker/box output you can before EQ.
If only moderately high levels are required, then EQ 'your heart out' > Class D now makes that easy 🙂
This is true for frequencies above system resonance.
At frequencies below system resonance efficancy dwindles, so i would thinck it is pretty clear that decreasing efficancy calls for even more power to compensate
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@gorgon53 I suggest to you (and everybody) to not quote posts in replies. Just tag the person you're replying to and the context will be understood just fine.
Quoting is unnecessary and just makes the pages much more cumbersome to navigate.
Regarding your post/reply.......it was a straw man argument and I don't respond to those.
Dave.
Quoting is unnecessary and just makes the pages much more cumbersome to navigate.
Regarding your post/reply.......it was a straw man argument and I don't respond to those.
Dave.
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Interesting comment >
I keep forgetting that this thread is not actually about SUBS, but bass!
I remember in live mixing, without shaking you, a true 'kick in the chest' was happening around 50 Hz.
Jesburger, you are fine, big box and the lavoce is, what i could see from the datasheet, a very capable speaker, do not worry.
My intention was to show the impact of temperatur on Qtc so you (and others reading that thread) would understand that (as someone suggested) inserting a 0.15 ohm resistor, or something like that, would not change a yota.
My intention was to show the impact of temperatur on Qtc so you (and others reading that thread) would understand that (as someone suggested) inserting a 0.15 ohm resistor, or something like that, would not change a yota.