Technical information help

[theabunai 3]

I was wondering to expand my knowledge and thought others here would benefit from my ever growing thirst for knowledge... i thought i would ask to help myself avoid these problems and also help educate those that aren't aware of these issues and how to avoid and/or discover the following problems..

Anyways.... as it pertains to sub woofers (particularly Fi built ones since i own some)

1. What is mechanical failure?

2. What are signs of mechanical failure (sight, sound, smell)?

3. What are the most common reasons for a sub to experience mechanical failure ?

4. What is thermal issues/problems in regards to sub woofers

5. What are signs of Thermal problems/issues (sight, sound, smell)?

6. What is the most common reason for a sub to experience Thermal issues/problems ?

I Know some reasons but thought i would posts since there are far more educated people here than I..

thank you

Edited July 4, 2007 by theabunai

[Jybfan04 1]

I was wondering to expand my knowledge and thought others here would benefit from my ever growing thirst for knowledge... i thought i would ask to help myself avoid these problems and also help educate those that aren't aware of these issues and how to avoid and/or discover the following problems..

Anyways.... as it pertains to sub woofers (particularly Fi built ones since i own some)

1. What is mechanical failure?

2. What are signs of mechanical failure (sight, sound, smell)?

3. What are the most common reasons for a sub to experience mechanical failure ?

4. What is thermal issues/problems in regards to sub woofers

5. What are signs of Thermal problems/issues (sight, sound, smell)?

6. What is the most common reason for a sub to experience Thermal issues/problems ?

I Know some reasons but thought i would posts since there are far more educated people here than I..

thank you

Im going to give you what I have come to understand these answers to be.

1. What is mechanical failure? Popping sounds, over excursion possibly , its a few more but these are the few I think are right.

2. What are signs of mechanical failure (sight, sound, smell)? I am not sure if a coil burning up is a part of mechanical failure or thermal failure I know its one of the two and hopefully someone will chime in to correct me if I said anything wrong.

3. What are the most common reasons for a sub to experience mechanical failure ? Being overpowered is the number one reason I would guess because when a sub is being overpowered its causing the sub to reach its xmax at a faster rate which in turn could lead the sub to have other problems which is why when people burp there subs on extreme amounts of power its for a few seconds because any longer will cause the sub to reach not only mechanical failure but thermal failure as well.

4. What is thermal issues/problems in regards to sub woofers ? Sub can no longer handle any more clean power it has reached its thermal peak in regards to the heat that is going around the coils which can cause it to cease to function.

5. What are signs of Thermal problems/issues (sight, sound, smell)? Coil fatigue or simply the coil jus has been burned up.

6. What is the most common reason for a sub to experience Thermal issues/problems ?

I don't know what the most common reason is because im still learning and somebody correct me if im wrong but imma go out on a limb and guess clipping is the number one reason a sub meets its demise from thermal issues due to the extreme heat that is generated from a clipping signal.

[DevilDriver 28]

I was wondering to expand my knowledge and thought others here would benefit from my ever growing thirst for knowledge... i thought i would ask to help myself avoid these problems and also help educate those that aren't aware of these issues and how to avoid and/or discover the following problems..

Anyways.... as it pertains to sub woofers (particularly Fi built ones since i own some)

1. What is mechanical failure?

2. What are signs of mechanical failure (sight, sound, smell)?

3. What are the most common reasons for a sub to experience mechanical failure ?

4. What is thermal issues/problems in regards to sub woofers

5. What are signs of Thermal problems/issues (sight, sound, smell)?

6. What is the most common reason for a sub to experience Thermal issues/problems ?

I Know some reasons but thought i would posts since there are far more educated people here than I..

thank you

I'll try to take a crack at these and hopefully they give you what you're looking for...

1. Mechanical failure is when you have damaged moving parts that will prevent the driver from functioning properly.

2. 9 times out of 10, you can hear it coming first. It sounds quite literally like the driver is over-extending itself, either by the former/voice coil banging on the backplate or a slightly drier sound of it over-extending in the forward direction and really pulling the suspension. It's kind of hard to explain, but I think once you've heard it, you'll recognize it immediately. You can also sometimes hear the cone hitting the spider landing or the tinsel leads slapping against the cone and/or spider. Any of these that cause permanent damage would be examples of mechanical damage, in my opinion.

However, some things can happen a little bit, cause some permanent damage, but still be very usable. For example, you can slap through the top spider on a BTL and experience very little audible change in performance. But if you smack the former into the back plate a few times, you're probably in trouble.

3. The only way to cause mechanical damage is to over-excurt the speaker, and the only way to do this is to apply too much power. The caveat here is that "too much power" is relative to both the frequencies being played and the enclosure being used.

Generally speaking, lower frequencies will excite more excursion from the driver than higher frequencies. Similarly, a larger enclosure will induce more excursion than a smaller one. Playing about an octave below Fb (the tuning frequency of your ported enclosure) will also cause the driver to unload and excursion to increase drastically.

4. Thermal damage would be when you have damaged the voice coil, former, or even the tinsel leads due to the amount of current flowing through and around any of these.

5. This *should* be easy to detect, so long as you have not jumped in full bore. If you're playing at a relatively sane level, you should smell something burning (and it is really an awful smell: very noticeable). If you are hard of smelling, you will be able to tell just by looking. Any of the parts in question will be significantly darker, if not black.

6. Similar to mechanical damage, thermal damage can only occur due to overpowering the driver. This is a very complex idea in and of itself. Your average consumer sees one thing: RMS ratings. Naturally, they believe that using an amplifier with an RMS rating below the driver's is underpowering, and using an amplifier with an RMS rating above the driver's overpowering. The truth is, it is much more complicated than that. First, consider the gain stage.

Second, a driver is capable of handling much more than RMS in certain conditions. Extended play with low crest factor material (ie. fully clipped signals w/ 0dB crest factor, sine waves with a 3dB crest factor, or poorly recorded music with crest factors ranging from 3dB-10dB) is a good recipe for thermal damage, but music with a very high crest factor and very transient music (ie. a few bass notes here, a few there) can be handled by the driver at power ratings well above RMS without any significant damage. I think it is worth noting that low voltage supply to your amplifier when driving the speaker at a very low impedance will almost certainly compound this issue.

Third, power compression indicates that adding more power is not necessarily a good thing; nearly every driver out there is more than satisfactory with well below RMS power and will run into preliminary power compression before reaching it's RMS rating.

Hopefully that makes some sense. Please reply if something seems unclear.

[Jybfan04 1]

I was close...

[DevilDriver 28]

I was close...

We said pretty much the same thing, just that I expanded a bit. It took me too long to get my post completed and you snuck in under the radar.

[theabunai 3]

However, some things can happen a little bit, cause some permanent damage, but still be very usable. For example, you can slap through the top spider on a BTL and experience very little audible change in performance. But if you smack the former into the back plate a few times, you're probably in trouble.

poorly recorded music with crest factors ranging from 3dB-10dB) is a good recipe for thermal damage, but music with a very high crest factor and very transient music (ie. a few bass notes here, a few there) can be handled by the driver at power ratings well above RMS without any significant damage.

These are some new things i just learned from the posts... thank you....

If there are any more info please feel free to add.....

I also know first hand with the help of Fi crew that another factor in mechanical failure is enclosure design...

a sealed enclosure not air tight...

Ported enclosure incorrectly tuned....