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Protective HPF for sealed subs?

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Didn't see anything on this.  Came up in discussion on audioholics where someone is suggesting that is something to do to prevent over excursion particularly in combination with eq/boost.   Anyone use a protective high pass filter for their sealed subs?   @Ricci do you use such when testing? 

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Most of the time you probably don't need one, whereas most vented and open-back horn type subs do need one. When designing a sealed system, it's always a good idea to look at excursion vs. the max power (based on amp choice) vs. frequency, which can be viewed in most design programs.  Keep in mind that if you think you need a high pass filter, you probably just need to choose a smaller amp (or set a voltage limiter in the amp) or make the box smaller to move the cut-off frequency higher.  There are surely exceptions here, especially if you're working with high motor force / low Qtc alignments where excursion can continue to increase for quite a ways as you go below the resonance.

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Thanks, that's been my general thinking as well.   While it does make sense to choose to use one if circumstances dictate, this recommendation was for any diy sealed sub and was wondering how many do it or for what reasons they did it for a specific build.   Sure isn't much available on the subject even with a general search, either so it doesn't seem to be a popular thought....

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I don't add one on my sealed HT sub, then again, I made a mistake once with the amp maxed out and now I have a voice coil ring dent on my metal dish cone :(

Still works fine tho!

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You may want one to remove content in the  low region the sub doesn't have useful output in to increase usable output in the region it does.  EG. if your sub is -3dB @ 30Hz and you play back the TELAC 1812 recording with 11Hz fundamental cannon fire you would be better off not just going to maximum excursion on the 11Hz and instead reproducing the harmonics*.  Only applies if your hitting excursion limits though, if the sub stays in the linear region I don't see an advantage to HPF.

*As the harmonics will be distorted by the sub been pushed out of the linear region

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On 9/21/2020 at 8:48 AM, SME said:

When designing a sealed system, it's always a good idea to look at excursion vs. the max power (based on amp choice) vs. frequency, which can be viewed in most design programs.

That's what I tell people as well. Make the sealed sub as big as you can, until you can reach Xmax at Pmax. Usually the cab will be smaller than what it takes to do so, so it doesn't make sense bothering with a HPF, unless you wanna reduce the load on the sub, like when you HPF it at 15Hz because your sealed 12" sub won't have meaningful output below that anyways.

 

14 hours ago, Kyle said:

I don't add one on my sealed HT sub, then again, I made a mistake once with the amp maxed out and now I have a voice coil ring dent on my metal dish cone :(

Still works fine tho!

  Was it a 5400?

 

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I don't use a HPF with sealed subs either in testing or my systems. I'm careful during testing to not push the level too high and in my systems I try not to have enough amp on tap to bottom the drivers with the box size used. 

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