ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2 3 ... 6   Go Down

Author Topic: HP filter really needed?  (Read 5839 times)

Mark Wilkinson

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 381
HP filter really needed?
« on: June 27, 2016, 08:43:18 pm »

Here's snip of a pair of Orbit Shifters indoors. 
Close mic'ed, raw response except for a +4db boost at 47hz.
My question is:  given the fairly steep natural rolloff below about 35hz, is a HP filter really necessary?
I've always used one, a BW4 @25...but not really sure why other than 'supposed to'....
Thx,  Mark

Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7767
  • Atlanta GA
Re: HP filter really needed?
« Reply #1 on: June 27, 2016, 09:31:24 pm »

In my opinion EVERY LOUDSPEAKER should use a HP filter-no matter what the response is.

The reason is that freq below when it can "easily work", the driver will tend to "flop around".

This can easily cause physical damage to the driver-even if the power is less than the ratings.

Even if the signal does not contain those freq, there are all sorts of "things" that can cause freq lower than intended to get to the driver.

Loose connections, people hot plugging something etc.

It is far better to be safe-rather than sorry.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Paul G. OBrien

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 660
Re: HP filter really needed?
« Reply #2 on: June 27, 2016, 09:46:56 pm »

Below port tuning or horn loading the driver is no longer damped by the enclosure meaning it operates as if it was out of the box hanging in free air and could be driven to it's mechanical limits with relatively little power, so if you want to keep your drivers functional you would be well advised to always have a low cut/high pass filter engaged.
Logged

Mark Wilkinson

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 381
Re: HP filter really needed?
« Reply #3 on: June 28, 2016, 09:40:18 am »

Thx guys,

I get what you're saying and have always told myself the same considerations.
Please do know I'm only asking about this particular horn loaded sub, and for when it is properly powered/ limited.....

Looking at the trace comparisons below, blue is raw, and purple is with a BW24 HP @30hz and a LR48 LP @ 100hz.
Sure HP rolls off faster, but it doesn't seem to add that much protection, .....
.....and the protection comes at the expense of either a bunch more phase rotation or latency, whichever poison is chosen..(latency in this example, note the unchanged phase traces)

I'm interested in dropping the HP because the most credible literature I can find on phase audibility, says best sound comes from linear phase throughout except for system high-pass, which equates to sub high pass. 
Supposedly, getting phase to follow sub magnitude roll-off is ideal.  IOW if magnitude rolls off at 24 db/oct, phase should rotate at same 4 pole rate per octave.

Want to find out for myself...and at crankin volume  ;D



Logged

David Allred

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 932
Re: HP filter really needed?
« Reply #4 on: June 28, 2016, 10:17:20 am »

Just because it can't produce 5hz, doesn't mean it ain't trying.
Logged

John Halliburton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 590
  • White pointy beard, knows zip...about chicken.
Re: HP filter really needed?
« Reply #5 on: June 28, 2016, 11:25:46 am »

All good reasons.  The Orbit Shifter(and any other sealed back/rear enclosure design) will offer some resistance to out of bandwidth response, but it is still a wise thing to have a good high pass filter in the circuit. 

One other benefit is that it should help lower nonlinear distortion should the driver be in the situation of reproducing that  20hz organ pedal note along with the content within it's design capacity.

Best regards,

John
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 16863
  • Wichita, Kansas USA
Re: HP filter really needed?
« Reply #6 on: June 28, 2016, 12:02:59 pm »

Here's snip of a pair of Orbit Shifters indoors. 
Close mic'ed, raw response except for a +4db boost at 47hz.
My question is:  given the fairly steep natural rolloff below about 35hz, is a HP filter really necessary?
I've always used one, a BW4 @25...but not really sure why other than 'supposed to'....
Thx,  Mark

Yes. Use the Filter, young Skywalker.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7767
  • Atlanta GA
Re: HP filter really needed?
« Reply #7 on: June 28, 2016, 12:26:28 pm »

Thx guys,

I get what you're saying and have always told myself the same considerations.
Please do know I'm only asking about this particular horn loaded sub, and for when it is properly powered/ limited.....

Looking at the trace comparisons below, blue is raw, and purple is with a BW24 HP @30hz and a LR48 LP @ 100hz.
Sure HP rolls off faster, but it doesn't seem to add that much protection, .....
.....and the protection comes at the expense of either a bunch more phase rotation or latency, whichever poison is chosen..(latency in this example, note the unchanged phase traces)

I'm interested in dropping the HP because the most credible literature I can find on phase audibility, says best sound comes from linear phase throughout except for system high-pass, which equates to sub high pass. 
Supposedly, getting phase to follow sub magnitude roll-off is ideal.  IOW if magnitude rolls off at 24 db/oct, phase should rotate at same 4 pole rate per octave.

Want to find out for myself...and at crankin volume  ;D
The real answer is "it depends".

I do agree that the best sonic performace will be without a HP filter.

HOWEVER-if you want to push the system hard, the additional protection of the HP filter far outweighs any sonic advantage-ESPECIALLY when the driver STOPS WORKING because it has "beat itself to death".

I am sure that "all of the people in the audience" will "understand" that earlier they were enjoying a better sonic performance, and now there is no bass.

People who have been drinking are very understanding in that regard ;) ;) ;) ;)

I am sure that the club owner will not mind if people stop drinking and leave because there is no bass anymore.

After all, it sounded so good earlier, it more than makes up for the lack of bass now.

YES, I am being sarcastic, but also being very real.

Sometimes it is more important to keep the system working, than to get a "little bit more" out of it and then have it fail.

I remember back in the early 80s, working with a Metal band.

Everything was going great, but the band wanted a little bit more out of the system.  They said they would pay for any blown speakers.

That may be all well and good, but at midnight on a Saturday-what am I going to do to get new drivers in the cabinets to play till 2am?

If I pushed the system and it stopped, they would QUICKLY forget all about the "we will pay for new speakers" and get mad at me for killing the system.

Then they and myself would not be hired back in the club because the system died.

None of the audience was complaining-just a couple of guys in the band.

It was simply not worth the risk.

Just something to consider.

I still say "ALWAYS use a properly set high pass filter".  The possibility of damage is simply not worth it.  Unless you are doing low to mid level listening.

Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

David Allred

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 932
Re: HP filter really needed?
« Reply #8 on: June 28, 2016, 12:53:58 pm »






Everything was going great, but the band wanted a little bit more out of the system.  They said they would pay for any blown speakers.





Even if they survive the night, the damage may be done and not show itself for days, weeks, or months.  Get cash payment up front as a non-refundable deposit.
Logged

Mark Wilkinson

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 381
Re: HP filter really needed?
« Reply #9 on: June 28, 2016, 05:34:48 pm »

Hey thanks all....I feel the experience/wisdom...HP in  ;)
Logged
Pages: [1] 2 3 ... 6   Go Up
 


Page created in 0.094 seconds with 20 queries.