AVS Forum banner

1 - 11 of 11 Posts

·
Registered
Construction debris
Joined
·
1,059 Posts
Discussion Starter #1
I see that DSP seems to be the standard way to create a high pass protection circuit for subs, while I don't see people using passives. Yes a MiniDSP lets you do more than just a simple low pass, but if my design only requires a first order high pass then just a coil shouldn't an air coil do the trick?

My thought is to go off actual DC resistance, calculate the mH air coil necessary to do the job, then buy one off the shelf that's close enough. I shouldn't need to wind my own, I like DIY but not quite to that extent.

The other the route to a first order HP is a capacitor, but finding something like a 3 mF cap means looking at things like motor start capacitors, which just seems oh so wrong.

So now that you've seen the insanity rattling around my head, tell me where the flaws in my plan is. Yes, I'm well aware that calculating a crossover on paper only is the path to madness, but this is just a protection circuit.
 

·
Registered
Joined
·
406 Posts
A few questions. Is this a sealed or ported sub? What frequency are you looking at.

Changing box volume will be easier than electrical means to manage Xmax clipping issues.
 

·
Registered
Joined
·
406 Posts
Easiest solution is plug the port. Changes the gain on the real low-end however the air behind the driver will acta as a loading damper and limit Xmax concerns.

thee best way besides an active crossover is to limit the output so it doesn't going into clipping. That is the area of where drivers get destroyed.

You might be able to pickup a used car active crossover on ebay for cheap that could also assist.
 

·
Registered
Joined
·
150 Posts
Good call, active is the way to go for crossover filters for subs.
Honestly the passive components needed for a highpass that low would probably cost as much or more then the MiniDSP anyway. Plus the large coil would eat a bunch of power, and also the problem of finding components large enough.
 

·
Registered
Joined
·
2,151 Posts
In addition the woofers impedance profile in a ported box wreaks havoc on passive filters at subwoofer frequencies. Not only would the calculated frequency of the filter likely be way off but the filter shape itself would end up looking like a roller coaster.

Example:
3047359
 

·
Registered
Joined
·
8,781 Posts
The FMODs are rubbish, single order only. You need 2nd order. Model it for proof.
PLLXO is about $2.
 

·
Registered
Joined
·
107 Posts
weird, they are advertised as 2nd order. not everyone has the skills to source parts for pllxo.. has anyone sort of laid that out?
 

·
Registered
Joined
·
5,850 Posts
Years ago I modified an active highpass design to make it adjustable by two Hertz increments. It would go inline at the input side of the amp. It would be adjusted by swapping jumper positions. I even ordered all the parts except for the PC board, which being custom, was too expensive for a one-off project, and so after discovering the 20 Hz workaround thread, I just got an amp with DSP in it instead.

Capture Highpass DWG.PNG
 
1 - 11 of 11 Posts
Top