# subwoofer protection



## Drudge (Sep 1, 2008)

Do subwoofers make rattling flubbering sounds when there protection/overload circuits activate?

I have a Mackie HRS120 12"x12 passive radiator 400 watt subwoofer that makes these sounds on certain scenes in movies that seem to have extreme amounts of bass were it sounds like the cabinet might come apart but it doesn't really sound like it's bottoming.My volume is at -13dB below reference level and I have checked for loose screws

Can protection circuits cause audible side effects?


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## hddummy (Mar 9, 2007)

I believe that a thermal protection circuit will simply turn off the amp, so I suppose you could say that would make an audible difference 

You may be hearing signal clipping. I don't have much experience with passive radiators, but that might be reaching it's excursion limits and causing distortion.


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## Mike P. (Apr 6, 2007)

It shouldn't. The peak limiter guards against clipping and overloading the amplifier. Do you have your subsonic filter engaged?


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## the_rookie (Sep 30, 2008)

First, my question is, is it a 400 watt peak or 400 watt RMS sub?

Second, can you further describe the sound its making?

Because, it may be 10+Db from reference level, but theres alot more to peak SPL than just dB reference and power peaks. People often forget to take into account the sounds that come from movies aren't always pure frequencies, there is impurities in the sound coming through the sub, and can add extra frequencies at the same time.

Also, we forget to take into account Distortion from the sound, its not a pure test tone frequency, theres much more than just one frequency coming from the movie, to the sub. So you may not get your max dB reference level all the time.


ps. if im wrong, can someone please correct me


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## Drudge (Sep 1, 2008)

I do have the subsonic filter engaged and from what I read since it requires huge amounts of output and excursion to reproduce <20Hz frequencies that my single sub can't put out in any felt/heard way anyway so I assume there is no point in wasting headroom and amp power on them.

Even when I didn't have it engaged it produced the same noises.I know that even at less than reference level listening with bass management on a single sub can be overwhelmed by today's soundtracks.It only happens on certain movies with intense LFE.Other than those soundtracks it plays without a problem with nice clean output.

I have had other less capable subs that didn't make as much ruckus like this one does though.Maybe it is the passive radiator but it has a pretty large surround.

Other than those occasions it's a great sub.I thought that maybe some protection circuits were just less polite than others.


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## Drudge (Sep 1, 2008)

It is 400 RMS/500 watt peak according to specs.It is kind of like a womp womp flub crackle rattle sound it hard to describe in words but different sounding than other subs I heard overload.


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## the_rookie (Sep 30, 2008)

Hmmm, i had a similar experience...i think when i was listening to the Halo Theme Mjolnir Mix, it has intense, deep bass during the Drum parts.

And i noticed one time on my Front Towers that it made that kind of description, and it was oscillating.


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## Drudge (Sep 1, 2008)

It does make a oscillatey kind of sound on some parts


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## Drudge (Sep 1, 2008)

There are jackhammer vibrating sounds on occasion as well it all depends on the movie.Some bass scenes like the Star Wars Episode II beginning flyover scene really bring all the those types of sounds out to were to sub sounds like it's going to melt down.On other movies the bass kicks you in the chest and all is fine on others the bass doesn't seem that intense and it makes the flub,flub,womp,rattle.


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## tonyvdb (Sep 5, 2007)

I'm starting to wonder if the amp is broken, I have an other idea as well, it could be the connections between the amp and the driver as well they could have a bad solder or loose connection? Have you tried to remove the driver or amp to gain access inside?


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## Drudge (Sep 1, 2008)

No I Haven't I'm kind of afraid to disassemble it fearing I may strip or break something.It just seems to do it on certain movies and no problem on the majority of the others.


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## tonyvdb (Sep 5, 2007)

It doesn't sound like clipping as thats usually just a quick snap or pop. Is the port clear of everything inside and out?


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## thxgoon (Feb 23, 2007)

I'm thinking your passive radiator is reaching its max exursion and making these sounds. Deep frequencies will activate it the most and that sounds like where you troubles are. I used to have some tower speakers with a passive radiator, and I remember in a certain scene in the matrix the passive radiators would reach their limit making a 'flap whoosh' sound. Watch it while playing one of those scenes to see if that's it. Otherwise call Mackie.


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## Drudge (Sep 1, 2008)

There is no port Tonyvdb it has a 12" passive radiator.

Thxgoon I think you may be right and it just running out of excursion.Could any of this be causing damage to the unit.


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## thxgoon (Feb 23, 2007)

If it happens enough it could weaken and tear the surround on the passive radiator. As long as the powered driver isn't bottoming and the amp isn't clipping then the rest of the unit should be safe.


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## the_rookie (Sep 30, 2008)

I believe Over Excursion can ruin the sub's suspension unit, magnet or the spider.

Cuz the extra forces can hit the magnet behind the speaker, and cause it to crack or slightly damage the magnet.

The suspension unit can be compromised in several locations.

And the spider, which is under the diaphragm, can be torn.


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## Drudge (Sep 1, 2008)

The duration is usually only a couple of seconds at the most demanding peaks.

How do I know if the amp is clipping?The main Mackie monitors have clip/overload indicators that light up(War of the worlds DTS track caused that to happen, only movie so far)but the sub doesn't have a indicator.Is there a sound or indication that the amp is clipping?



Thanks for all the input guys:T


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## thxgoon (Feb 23, 2007)

It's pretty hard to hear the amp clipping on a subwoofer. If you hear any distortion at all then it is too loud. Your sub was engineered by a good company, I doubt they would engineer it to self destruct without you knowing it's coming.

the-rookie - what is you say is true of powered drivers. In Drudge's case the passive radiator has no components other than the surround and the woofer.


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## Drudge (Sep 1, 2008)

Once again thanks for all the help guys I appreciate it


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## tonyvdb (Sep 5, 2007)

Drudge said:


> There is no port Tonyvdb it has a 12" passive radiator.


duh, I should know that :hide:


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