DiyMobileAudio.com Car Stereo Forum banner
1 - 20 of 155 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter · #1 ·
Hi all,

Just looking at which highpass filter (subsonic) I should use for my setup. Is Butterworth (2nd order) the best filter if you look at the amount of group delay added?
I understand that depending on the frequency it does not matter, so it depends on where you put the filter (hz).

Thanks in advance
 

·
Registered
Joined
·
19,632 Posts
the best for group delay is no filter at all. if this is for a subwoofer, dont use one unless your using a ported box
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #3 ·
the best for group delay is no filter at all. if this is for a subwoofer, dont use one unless your using a ported box
Re-reading my post above I should have given more details.

This is for a ported box, 2 JL drivers tuned to 35Hz or so (depending on how big a slot port I can fit in the box).

So yeah I need a HPF, and I have a DSP to do it with (not going to use the analog one on the subwoofer amp). I'm getting pretty OK results in WinISD and Bassbox Pro, I just thought I'd ask for some opinions to see if I'm missing anything.

Thank you
 

·
Registered
Joined
·
19,632 Posts
regardless, theres going to be group delay. i wouldnt worry about what filter type is best to minimize it. i would be more concerned about making sure the subs are safe
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #10 ·
The group delay is already sky high with a ported box so....
It's all relative.

Compared to a sealed box - yes, it is obviously higher. But is it noticeable? That depends on the implementation.

It's entirely possible to build a ported enclosure that sounds as tight as a sealed box - but it will not simulate as low of a group delay.
 

·
Registered
Joined
·
2,371 Posts
The audibility of group delay remains highly debatable especially in low frequencies. Don't worry about it.
The group delay is already sky high with a ported box so....
Agreed.

The least amount of group delay will come from a 1st order butterworth unless you want to use a FIR filter. But seriously, don't worry about it.
 

·
Registered
Joined
·
5,003 Posts
Hi all,

Just looking at which highpass filter (subsonic) I should use for my setup. Is Butterworth (2nd order) the best filter if you look at the amount of group delay added?
I understand that depending on the frequency it does not matter, so it depends on where you put the filter (hz).

Thanks in advance

Adding a Hpf on a sub more than likely will cause a pretty bad timing issues ,
It mostly depends on how it's aligned to the midbass , some delay can help line things back up , but the issue than becomes the LPF , the HPF will cause timing issues for a very large part of the passband , so much so it would be noticeable all the way up to the LpF side of things.

In honesty I would stay away from using a subsonic (hpf) on a sub. I would actually run from the idea as fast as I could and never look back.

Instead, I would use very small amounts of PEQ targeted at specific frequencies with a controlled Q to combat excursion issues (if any)

A small dip in a he responce down that low that would very effectively solve a power distribution issue because of a port unloading or transfer function or whatever your thing is, a small dip caused by small eq applied would be far less detrimental on time and general IR. That low is definitely right in the IR that so much is attributable to.

If it can be avoided all together it is choice and don't use any filter that would cause harm to the impulse.

But it is measureable , some peq or even a hpf could actually help the impulse.....again it depends on a lot of variables and would need to be measured.

That low in frequency a 1st order filter would behave a lot like a 2nd order or 3rd order filter because of how low it is.....what I'm saying is that low an oactave is less than 10hz away in some cases ......so a 1st order filter could exhibit a shape that is similar to a 4th order filter at its 10x power.

So a 1st order filter that low does matter and should be something to worry about. It could seriously screw things up as far as timing. Especially if a port is behind it. Figure a port has at least 20ms GD with a narrow Q and some sort HPf would surly cause some sort of ripples in the time domain. But again can't stress how much a couple measurements will tell you what is going on.
Let's not talk about the phase response of a microphone under 100hz right now , any program like REW should be able to at least be able to see what's going on down that low with even tho the resolution isn't superb at 10hz , should still get an idea on what or what not to implement.

A lot to think about , for what reason do you want a HPf? Bottoming the sub out?
 

·
Registered
Joined
·
5,097 Posts
Adding a Hpf on a sub more than likely will cause a pretty bad timing issues ,
It mostly depends on how it's aligned to the midbass , some delay can help line things back up , but the issue than becomes the LPF , the HPF will cause timing issues for a very large part of the passband , so much so it would be noticeable all the way up to the LpF side of things.

In honesty I would stay away from using a subsonic (hpf) on a sub. I would actually run from the idea as fast as I could and never look back.

Instead, I would use very small amounts of PEQ targeted at specific frequencies with a controlled Q to combat excursion issues (if any)

A small dip in a he responce down that low that would very effectively solve a power distribution issue because of a port unloading or transfer function or whatever your thing is, a small dip caused by small eq applied would be far less detrimental on time and general IR. That low is definitely right in the IR that so much is attributable to.

If it can be avoided all together it is choice and don't use any filter that would cause harm to the impulse.

But it is measureable , some peq or even a hpf could actually help the impulse.....again it depends on a lot of variables and would need to be measured.
How on earth does a HPF affect the timing of the driver?:rolleyes:
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #16 ·
Yes - the HPF is to protect the driver in this case, nothing else.

I'm going to have to measure the response of the box in the cabin, apply the PEQ & DSP filters etc to get the curve that I want. Only after that, figure out what I need to use to protect the sub. That might be a better approach.
 

·
Registered
Joined
·
5,003 Posts
regardless, theres going to be group delay. i wouldnt worry about what filter type is best to minimize it. i would be more concerned about making sure the subs are safe
There's a lot to be said with this comment ,

Why does he say this?
And what is the heart of this statement?


I would suggest he's saying it's a train wreck of timing issues down that low and the sub not blowing is the more important issue.....and he's right!

If the sub is bottom out or suffers from too much power for that enclosure and lack of loading (transfer function) than what difference does it make and that is a very legitimate argument.


If the sub can't play that low and is suffering that strongly suggests more serious issues in the enclosure and transfer function than I would be worried about than the timing of sub harmonics. Skier is right, he just didn't explain it thoroughly.

The sub really needs to be able to perform on its own with little to no eq at full power. Getting that right is far more important step before trying to adress timing errors. Of the port is unloading prematurely because of various reasons or the sub is just simply overpowered for its enclosure or ratings , that needs to be addressed first.

All install related issues need to be solved and addressed before considering phase at subsonics , if it's not it would have serious problems that are just not realistic to try to solve with the use of a filter in its normal passband. Let alone in the subsonic ........


If it's bottoms out , and your trying to save the sub, skizr is right. Do whatever keeps the sub safe and don't worry about the rest. At that point it's such a mess everywhere else it's not reasonable to try to fix

Get the sub the right box that can play at full power on its own than phase issues can be worked on. The subsonic gives so much "energy" to the entire sub passband , it needs to be able to play on its own so that energy can be distributed correctly....... minimum phase is the energy responce in other words and if there's problems with the enclosure you would end up turning everything down so low of a level before it's all "corrected" that the output would be unacceptable. It's only as good as its weakest link to a large degree
 

·
Registered
Joined
·
5,097 Posts

·
Registered
Joined
·
5,003 Posts
Group delay is very different from the timing of the direct sound from a speaker. You said the HPF affects timing i.e. direct sound, that is wrong.
Timing i.e direct sound????? Huh
Bro your confusing

i.e. Means "anotherwords" or "example"

I said nothing about direct sound , didn't even use the phrase :confused:

If your saying timing is direct sound that is wrong
 

·
Registered
Joined
·
2,977 Posts
1 - 20 of 155 Posts
Top