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Author Topic: LR-24 360░ phase shift?  (Read 6456 times)

Daniel Mock

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LR-24 360░ phase shift?
« on: March 27, 2015, 08:02:50 pm »

So I figured that if I measure the horn paths I could easily calculate delay for system time alignment, but I just read an article saying I need to account for the 360degree phase shift cause by LR-24.
How do I do this?

My system is 4-way:
SUB: BW HP 30hz, LR-24 LP 127hz, 50"hornLength
LOW: LR-24 HP 127hz, LR-24 LP 440hz, 30" hornLength
MID:LR-24 HP 440hz, LR-24 LP 5.5khz 10" hornLength
HI: LR-24 HP 5.5khz, off, 8" hornLength

What polarity setting and delay do I need
to properly time align system when using LR-24?
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John Roberts {JR}

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Re: LR-24 360░ phase shift?
« Reply #1 on: March 27, 2015, 08:32:15 pm »

What does the article say to do?  ;D

Phase shift and time delay are different things.

A 4 pole Linkwitz-Riley exhibits 180' of phase lead, in one output and 180' of phase lag in the other. !80'+180'=360'=0'

The L-R alignment are both -6dB at tuning so they combine, in phase to 0dB, or unity.

Any delay you add should be to compensate for path length transit time differences, not the crossover.

JR
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Daniel Mock

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Re: LR-24 360░ phase shift?
« Reply #2 on: March 28, 2015, 04:28:32 am »

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Ivan Beaver

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Re: LR-24 360░ phase shift?
« Reply #3 on: March 28, 2015, 11:47:57 am »

So I figured that if I measure the horn paths I could easily calculate delay for system time alignment, but I just read an article saying I need to account for the 360degree phase shift cause by LR-24.
How do I do this?

My system is 4-way:
SUB: BW HP 30hz, LR-24 LP 127hz, 50"hornLength
LOW: LR-24 HP 127hz, LR-24 LP 440hz, 30" hornLength
MID:LR-24 HP 440hz, LR-24 LP 5.5khz 10" hornLength
HI: LR-24 HP 5.5khz, off, 8" hornLength

What polarity setting and delay do I need
to properly time align system when using LR-24?
It is not that simple.

As you change freq-the "delay" (phase shift) of the filter also changes.

This is easily seen on a measurement.

And when you are figuring your "horn length", what is this based on? The actual length of the horn? or a distance to some point in space.

  If the horns do not occupy the same physical space (and that is NOT simply being in the same cabinet) then the distance to a person listening will be different for each horn.

And once you move the position of the person listening-the distance from each horn will change.

You have to figure out "what position is most important" and go from there-and just accept the fact that all the other listening positions will be "off".  No way around it.

The problem is that phase/delay is not something that is an "easy question".

You also need to account for the phase response of each particular driver.

That is why it is SOOOOOO much easier to simply measure and see the phase response than to attempt to "calculate it"-especially when there are "unknowns" in the equation.

You can adjust the delay time in real time-see the results-see the interactions above and below crossover freq and so forth.
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Ivan Beaver
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John Roberts {JR}

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Re: LR-24 360░ phase shift?
« Reply #4 on: March 28, 2015, 12:19:01 pm »

Here is the article
http://www.livesoundint.com/archives/2003/july/align/align.php

I just looked at that article and did not see any mention about a L-R crossover alignment.

John did list his email.  ;D ;D ;D (I knew him when he worked at Peavey on Media Matrix)

As Ivan stated there is nothing easy about this...

JR
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Timo Beckman

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Re: LR-24 360░ phase shift?
« Reply #5 on: March 29, 2015, 10:38:25 am »

So I figured that if I measure the horn paths I could easily calculate delay for system time alignment, but I just read an article saying I need to account for the 360degree phase shift cause by LR-24.

Measuring the distance between drivers doesn't do the trick. If you apply a low pass filter  on a driver the timing changes. I did a couple of screen recordings where you can see what happens at processor level when a low-pass filter is applied.

https://timobeckmangeluid.wordpress.com/2015/02/28/butterworth-high-and-low-pass-filters-up-to-8th-order-and-back-again/

From about 3min in to the screen recording the fun starts with the low-pass filters and at 5min into the recording i set Smaart to
delay tracking to show what happens.
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Daniel Mock

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Re: LR-24 360░ phase shift?
« Reply #6 on: April 03, 2015, 03:17:37 am »

My goal is for full coverage area to be "pretty good". Perfecting a sweet spot only makes other areas worse which isn't good when you're trying to cover a large audience.
I guess you could say I'm seeking the full possible summation from horns/drivers out of the cabs overall.
Most of the time I do this by measuring horn paths to get an estimation of delay then twiddle with the delay unit it sounds the loudest.  But honestly have no idea of what I'm doing is correct at all, especially now considering LR24 phase shift.
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Daniel Mock

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Re: LR-24 360░ phase shift?
« Reply #7 on: April 03, 2015, 03:19:45 am »

Are FIR filters void of this phase shift issues?
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Luke Geis

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Re: LR-24 360░ phase shift?
« Reply #8 on: May 09, 2015, 07:24:33 pm »

It's linear. So the phase shift is the same at all frequencies. Quick and dirty article. http://www.dspguru.com/dsp/faqs/fir/properties
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Lyle Williams

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Re: LR-24 360░ phase shift?
« Reply #9 on: May 10, 2015, 04:13:52 pm »

But FIR boxes still suffer from the bigger issue that all the drivers aren't in the same place and that the patterns they throw change with frequency.

FIR is a fix to the fourth biggest problem in the room.
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Luke Geis

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Re: LR-24 360░ phase shift?
« Reply #10 on: May 10, 2015, 08:16:18 pm »

True. One day the will make an electrostatic horn loaded speaker that can get to 140db!
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David Sturzenbecher

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Re: LR-24 360░ phase shift?
« Reply #11 on: May 10, 2015, 08:40:40 pm »

True. One day the will make an electrostatic horn loaded speaker that can get to 140db!

Don't put a horn anywhere near my electrostats.
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Ivan Beaver

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Re: LR-24 360░ phase shift?
« Reply #12 on: May 10, 2015, 09:14:11 pm »

True. One day the will make an electrostatic horn loaded speaker that can get to 140db!
I know you were just "making a joke", but "putting a horn" on it is something that is misunderstood by many people.

A horn is actually a bandpass type device.  It has limits on the top end (due to the size of the entry into the horn), and the low end (due to the length, expansion rate, mouth size etc).

In reality you need different expansion rates for different parts of the freq spectrum.  Hence the reason a simple horn on a full range single loudspeaker does not work as well as it should.

The higher freq need a faster expansion rate than lower freq.  Mids are in the middle ;)

It is the "proper useage" of horns that make them actually work.

Size matters (both large AND small)-in all kinds of ways with horns.

In order to get get gain up high-the entrance into the horn has to be small-hence the reason you don't get much gain up high from a 2" compression driver.  A 1" into a horn will actually have more horn gain in the top octave or so.  And since it already has a greater output (due to higher sensitivity and lower mass) it can actually produce MORE SPL than a 2" driver-at the higher freq.  Down lower in freq it is a different story.

Everything is about tradeoffs-so it is important to understand what is going on-so the proper tradeoffs can be made and determine what is most important for a particular situation/usage.
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Ivan Beaver
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Luke Geis

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Re: LR-24 360░ phase shift?
« Reply #13 on: May 11, 2015, 12:02:25 am »

I was of course kidding.

Hey maybe  plasma speakers will be practical one day!
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Ivan Beaver

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Re: LR-24 360░ phase shift?
« Reply #14 on: May 11, 2015, 07:24:23 pm »

I was of course kidding.

Hey maybe  plasma speakers will be practical one day!
I always wanted to build a plasma speaker.

I wanted to build one with my son before he graduated HS-but never got  around to it.

On of the big problems with plasma (beside ozone depletion) is they have a limiter output capability.

But I STILL think it would be cool to have one.

Maybe some day when I get a few (yeah right) hours of time----------  I guess that would be about 3 days after I am dead.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

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Luke Geis

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Re: LR-24 360░ phase shift?
« Reply #15 on: May 11, 2015, 10:01:35 pm »

I have been researching low mass and massless speakers more lately. The concept intrigues me. Ultrasonics and hyperdirectional designs should be explored more.
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Tim McCulloch

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Re: LR-24 360░ phase shift?
« Reply #16 on: May 12, 2015, 08:11:42 pm »

Don't put a horn anywhere near my electrostats.

Can we get them to do double duty as smoke eaters?
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Tim McCulloch

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Re: LR-24 360░ phase shift?
« Reply #17 on: May 12, 2015, 08:13:26 pm »

I was of course kidding.

Hey maybe  plasma speakers will be practical one day!

Nomex« and Kevlar« laminate speaker enclosures.  The "horn" version could be a flame thrower....
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"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

ProSoundWeb Community

Re: LR-24 360░ phase shift?
┬ź Reply #17 on: May 12, 2015, 08:13:26 pm ┬╗


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