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Author Topic: HP filter really needed?  (Read 6103 times)

John L Nobile

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Re: HP filter really needed?
« Reply #10 on: June 29, 2016, 01:34:14 am »

Won't you get more useable power from your amps if you add the hipass? Your box may not produce much below 40 hz but nobody told the amp that. It's still amplifying at least another octave below that.
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Stephen Kirby

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Re: HP filter really needed?
« Reply #11 on: June 29, 2016, 05:41:01 am »

Won't you get more useable power from your amps if you add the hipass? Your box may not produce much below 40 hz but nobody told the amp that. It's still amplifying at least another octave below that.
Especially if you're getting sub-sonic noise from somewhere in the system.
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Ivan Beaver

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Re: HP filter really needed?
« Reply #12 on: June 29, 2016, 06:34:48 am »

Won't you get more useable power from your amps if you add the hipass? Your box may not produce much below 40 hz but nobody told the amp that. It's still amplifying at least another octave below that.
Yes, and it will also clean up the sound in a different way.

Since the lower freq will cause the driver to move more than it should.

The more any loudspeaker moves, the more distortion it will produce.

So by keeping the low freq that cause excessive movement out of the driver-the other freq will be cleaner.
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Ivan Beaver
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Gordon Brinton

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Re: HP filter really needed?
« Reply #13 on: June 29, 2016, 07:26:52 am »

What's this new obsession that some folks have with content below 35Hz? Is it only in EDM? Because, frankly, I don't miss it in my music.

(This is not aimed at the OP, I'm just asking.)
« Last Edit: June 29, 2016, 07:44:15 am by Gordon Brinton »
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Mark Wilkinson

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Re: HP filter really needed?
« Reply #14 on: June 29, 2016, 08:41:37 am »

What's this new obsession that some folks have with content below 35Hz? Is it only in EDM? Because, frankly, I don't miss it in my music.

(This is not aimed at the OP, I'm just asking.)

Hi Gordon, yeah, I don't listen to much below 35hz either.
From what little EDM I have heard, my guess is that below 35hz is more about feel, bodily vibration, than auditory.
Or maybe better said, integrating body vibration with auditory vibration.

Almost ridiculously, I've been a phase=o=holic lately.
My interest in removing a HP filter is not about extending LF, but about optimal phase alignment for highest possible sound quality.
Here's a post from a guy that makes alot of sense to me, and matches what many others are starting to say about linear phase.
http://www.diyaudio.com/forums/multi-way/283068-mini-synergy-horn-experiment-25.html#post4554771

I had been trying to flatten phase all the way down to lowest freq, but it wasn't sounding right, so now I'm trying to match magnitude and phase rolloff.
So, this HP filter question is really just about trying to follow the recommendation in the link regarding system highpass phase.
A HP filter in play makes doing it a bit trickier...

I wholeheartedly agree with linear phase improving transients, increasing vocal clarity, and giving bass impact.
The transient improvement is a little difficult to judge sometimes, as I've found I can be fooled by small amounts of HF/VHF change.
Bass can be tough too, with reflections and all.....
But vocal clarity never seems to lie...my trusted test is how well backing vocals come through.

Hey, if we ever get speakers that go to zero hz, then maybe flat linear phase to zero, with no system highpass.....
..... will fully integrate being bodily rocked and audibly rolled  ;D
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Ivan Beaver

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Re: HP filter really needed?
« Reply #15 on: June 29, 2016, 12:44:14 pm »

What's this new obsession that some folks have with content below 35Hz? Is it only in EDM? Because, frankly, I don't miss it in my music.

(This is not aimed at the OP, I'm just asking.)
There is A LOT of "normal" music that has content below 35Hz.

The low B on a bass guitar is 31Hz.  Lots of orchestral bass drums are tuned very low.  Many pipe organs go well below 35Hz-even down to 8Hz

Contra bass bassoons and clarinets can get to 15Hz

The low note on the piano is 27Hz  Some pianos go down to 16Hz

Several brass instruments can get down well below 35Hz as well

Yes, I agree that these are not "normal rock instruments", but there is A LOT of music that is not rock that has instruments that go very low.

And not being able to reproduce the fundamental is not accurately reproducing their sound.

BTW-lots of synthesized pop music has content below 35Hz-but many people say you don't need it-simply because THEY have never heard it.  But that doesn't mean it does not exist!

When doing a demo last year, I had a guy say about a "pop" song- "So THAT'S what that song is supposed to sound like"-after he heard the real extension.

YES-it DOES matter :)

Here is a link to help

http://www.contrabass.com/pages/frequency.html
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Luca Rossi

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Re: HP filter really needed?
« Reply #16 on: June 29, 2016, 01:57:12 pm »

Won't you get more useable power from your amps if you add the hipass? Your box may not produce much below 40 hz but nobody told the amp that. It's still amplifying at least another octave below that.


This is not quite right, because cutting the lower octave doens't add more useable power. The peak power is always the same, so the clipping voltage is also the same. When you cut out some portion of the spectrum, you only reduce the RMS power of the signal, but amplifier doens't care about it unless its power supply is very undersized for that amp.
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Gordon Brinton

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Re: HP filter really needed?
« Reply #17 on: June 29, 2016, 06:13:13 pm »

...And not being able to reproduce the fundamental is not accurately reproducing their sound.

BTW-lots of synthesized pop music has content below 35Hz-but many people say you don't need it-simply because THEY have never heard it.  But that doesn't mean it does not exist!

When doing a demo last year, I had a guy say about a "pop" song- "So THAT'S what that song is supposed to sound like"-after he heard the real extension.

YES-it DOES matter :)

Perhaps we still get a glimpse of what's there even when it is missing.

https://en.wikipedia.org/wiki/Missing_fundamental
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John Roberts {JR}

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Re: HP filter really needed?
« Reply #18 on: June 29, 2016, 06:24:39 pm »


This is not quite right, because cutting the lower octave doens't add more useable power. The peak power is always the same, so the clipping voltage is also the same. When you cut out some portion of the spectrum, you only reduce the RMS power of the signal, but amplifier doens't care about it unless its power supply is very undersized for that amp.
Average power matters at LF.

Higher frequency signals will be superimposed on top of the LF signals so can saturate or clip the amplifier sooner if they are not removed.

It is good practice to high pass the audio path appropriately for components bandwidth, while there should be some HPF already present in the audio chain.

JR
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Ivan Beaver

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Re: HP filter really needed?
« Reply #19 on: June 29, 2016, 06:58:08 pm »


This is not quite right, because cutting the lower octave doens't add more useable power. The peak power is always the same, so the clipping voltage is also the same. When you cut out some portion of the spectrum, you only reduce the RMS power of the signal, but amplifier doens't care about it unless its power supply is very undersized for that amp.
ACTUALLY--------

By decreasing the bandwidth of a signal WILL reduce the power that it is putting out.

This is real easy to see for yourself.

Put in a noise source into an amp (no speaker hooked up) that is full bandwidth.

Hook a voltmeter to the output.

Now reduce a LP filter or raise a HP filter while looking at the voltmeter.

You will see the voltage lower as the bandwidth gets narrower.

This is because there are not as many freq adding together-causing the voltage applied to the load to be higher.
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Ivan Beaver
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