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Discussion Starter #1 (Edited)
The past 5 subs that I've built have been powered with plate amps that have a built in subsonic filter. My next build, starting next week, will be a pair of Mach 5 Audio IXL 18.4.s with each having a 12 cubic foot box tuned to 16.5 hz. For power I'm considering either an EP2500 or a pair of Elemental Designs 550 watt plate amps. Both the EP2500 and the ED 550 plate amps do not have a subsonic filter. I found an add on subsonic filter from Creative Sound Solutions called the Reckhorn B-1.
http://creativesound.ca/details.php?model=B-1
More information on it can be found here.
http://www.reckhorn.com/index.php?ln=en&prod=b1
For 80 dollars it appears to be a cost effective solution. I am curious if anyone has tried this unit.
 

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Im no expert, but since you are building a LLT tuned already subsonic, why would you wanna filter it?

One of the purposes of an LLT is to reach subsonic. Seems a little counter productive if you ask me.

Also you need to remember that there is a steep roll off int he drivers response once you go below the tuned freq as the driver and the port fight for output.

If you are looking to get the boost function, i would suggest the BFD as an EQ and do what ever you're heart desires from there. same price and much more configurable.
 

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Discussion Starter #3
Thanks for the reply. I'm not after the boost function. My concern is protecting the driver below the tuning frequency. My box size and tuning frequency is close to what's recommended by the manufacturer. I was under the impression that LLT's were tuned alot lower, like 12hz. After reading about pro amps with no subsonic filter blowing up subs, my thinking is some protection would be worth while. Any comments would be appreciated.
 

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Elite Shackster
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The past 5 subs that I've built have been powered with plate amps that have a built in subsonic filter. My next build, starting next week, will be a pair of Mach 5 Audio IXL 18.4.s with each having a 12 cubic foot box tuned to 16.5 hz. For power I'm considering either an EP2500 or a pair of Elemental Designs 550 watt plate amps. Both the EP2500 and the ED 550 plate amps do not have a subsonic filter. I found an add on subsonic filter from Creative Sound Solutions called the Reckhorn B-1.
http://creativesound.ca/details.php?model=B-1
More information on it can be found here.
http://www.reckhorn.com/index.php?ln=en&prod=b1
For 80 dollars it appears to be a cost effective solution. I am curious if anyone has tried this unit.
Why not try them without one first? It's not like they would instantly blow up if you slightly bottom them. Although I'm 99.9 % certain that you won't ever bottom those subs with normal program material. Especially with that "little" amp power.
 

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I was under the impression that LLT's were tuned alot lower, like 12hz. After reading about pro amps with no subsonic filter blowing up subs, my thinking is some protection would be worth while. Any comments would be appreciated.
You're correct about the LLT, but even when you tune a sub to the manufacturer spec that may be higher than an LLT, there can be considerable high pass filtering from your electronics that tends to protect the driver below tuning. Many of us here have used REW software to test our entire sub chain that can include the processor, line drivers, BFD equalizers and power amps that all combine to provide a somewhat 'free' high pass filter.

Doesn't hurt to test the system out before adding un-needed filters.....

brucek
 

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Discussion Starter #6
Why not try them without one first? It's not like they would instantly blow up if you slightly bottom them. Although I'm 99.9 % certain that you won't ever bottom those subs with normal program material. Especially with that "little" amp power.
That is a good point. I can slowly increase the levels of the subs to where I prefer and see how they react. Should I need the Reckhorn B-1 I can add it later. I am curious as to how the subs will handle program material like War Of THe Worlds at the levels that I listen to. As for my "little" amp, I don't need a "monster" amp because I already have twin Atlas 15's in 10 cubic feet ported enclosures. Between the 4 subs I should be happy with the output.:T
 

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Discussion Starter #7
You're correct about the LLT, but even when you tune a sub to the manufacturer spec that may be higher than an LLT, there can be considerable high pass filtering from your electronics that tends to protect the driver below tuning. Many of us here have used REW software to test our entire sub chain that can include the processor, line drivers, BFD equalizers and power amps that all combine to provide a somewhat 'free' high pass filter.

Doesn't hurt to test the system out before adding un-needed filters.....

brucek
I agree. I'm in the process of learning about the REW software and will be using it to see where I'm at. Hopefully I will discover a somewhat 'free' high pass filter. If not, then I have the option of the Reckhorn.
 

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You shouldent beable to damage those drivers with that amount of power no matter how low it goes. you're amp will surly clip before that happens.

For example i have a FI Q 15" driver that i have in a LLT tuned to like 13hz or so, and have put ~1000 real watts to it at 10Hz and it takes it like a champ. never bottomed out the sub.

Also if you have a subsonic filter on you are cutting into you're ported freq pretty badly more or less negating the use of the port (in terms of flatter low response).
 

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Hmm, maybe I made a mistake in cone excursion when I modelled the sub. I don't have access to the modelling program at the moment as I'm away at work until next Tuesday. I'll definetly look into it when I get home. Thanks for your reply.
You shouldn't put too much weight on those simulations. They are based on small signal models, and don't for example account for suspension non-linearities (compliance goes down as the excursion goes higher). Or any other non-linearities actually...
 

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Discussion Starter #11
True. But I have found that the simulations can give a general idea of what to expect. At least it's a starting point. REW is excellent in showing the difference between simulated and actual response. Too bad there isn't some kind of test to show the difference between simulated and actual cone excursion.
 

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I was also wondering what I should do about this... I think its a very valid question..
I have narrowed my descision to build to 2 - 320 liter boxes with a TC-2K each and looking at powering them with 1800wpc each... How do I protect these drivers from damage with no highpass filter...
What are the other various methods for a highpass filter...?
 

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How do I protect these drivers from damage with no highpass filter
That's what we have been discussing. The electronics can protect the drivers if your tune is low. What is your target tune?

brucek
 

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oops! I did it again.... I meant 270 liters

My target tune is whatever 15" TC-2K's model out to the best in that (270 liter - 9.5 cu. ft.) box size, 14.5 to 16.5 hz.... I still have to iron out the wrinkles, but thats roughly the size boxes Im looking at... Im not all that great with the WinISD yet... but Im trying...

Will end up being a 6" port, just not sure on the length yet...
Going for a Downfiring enclosure...
 

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Interesting comment by Ilkka on compliance decreasing with excursion. :hail:

The rubber band effect! :ponder:

Which gave me yet another crazy idea for driver protection. :coocoo:

Stretch rubber bands across the face of the cone between the driver fixing screws. :dumbcrazy:

Add a bit of felt to the dustcap to quieten possible impact noise... et voila!

You have a burst-proof sub. :rofl:

Don't try this at home children. :R
 

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:coocoo:

seriously though....a high pass filter is about as simple of a circuit as it gets. You could always try and build one yourself. It would cost like 5 dollars for signal level filter components. Speaker level would be a different story. You could even make the cut-off frequency adjustable with a potentiometer.
 
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