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Author Topic: Choosing the best sub for me  (Read 21283 times)

Scott Carneval

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Re: Choosing the best sub for me
« Reply #100 on: June 23, 2015, 01:58:52 pm »

I don't believe anyone is trying to mislead me, but I have read up on how crossover networks work, and I don't see that anyone has taken a stab at directly answering my question. 
  If you have a lonely 10" transducer on a highpass filter,  what causes it to reproduce the frequencies near the corner ahead of the higher frequencies?

They aren't reproduced 'ahead in time'.  That's simply not possible.  Phase isn't time and time isn't phase.  Phase varies over time and therefore if you adjust time, you CAN adjust phase.  The frequencies aren't produced ahead in time, but they DO originate at a different degree of phase.  So the goal is to time-align each passband so that the x-over frequencies are in phase. 
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Scott Carneval

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Re: Choosing the best sub for me
« Reply #101 on: June 23, 2015, 02:04:00 pm »

I don't believe anyone is trying to mislead me, but I have read up on how crossover networks work, and I don't see that anyone has taken a stab at directly answering my question. 
  If you have a lonely 10" transducer on a highpass filter,  what causes it to reproduce the frequencies near the corner ahead of the higher frequencies?

No, one is trying to mislead you, but this is a very complicated subject and not one that is easy to wrap your head around for the first time.  It helps a lot to have a graphical representation of what's going on. I would suggest searching youtube I'm sure someone has put together a good video on it. 

It wasn't until I attended a 3-day SMAART class that I began to understand what was going on. 
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Jacob Shaw

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Re: Choosing the best sub for me
« Reply #102 on: June 23, 2015, 03:14:26 pm »

"But it does originate at a different degree of phase". That's it!  It clicks now!  Big ups Scott, you nailed it.
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Jacob Shaw

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Re: Choosing the best sub for me
« Reply #103 on: June 23, 2015, 03:17:11 pm »

So does a LR 4 filter really correct this problem as long as the drivers are spacially aligned?
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Scott Carneval

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Re: Choosing the best sub for me
« Reply #104 on: June 23, 2015, 03:34:42 pm »


So does a LR 4 filter really correct this problem as long as the drivers are spacially aligned?

Are you suggesting a 4db per octave crossover?  I don't think that's steep enough to be useful. If it really bothers you, you can look into FIR or Finite Impulse Response filters. But they have drawbacks too as they add overall latency to the entire system.

I think you're concerning yourself too much with fixing something that really can't be fixed. Like everything else in audio, it's a compromise. For most situations the best compromise is using a little bit of delay to phase align each passband through the crossover region.


Sent from my iPhone using Tapatalk
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Mac Kerr

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Re: Choosing the best sub for me
« Reply #105 on: June 23, 2015, 04:00:38 pm »

Are you suggesting a 4db per octave crossover?

No, a LR 4 is a 4 pole is a 24dB/oct Linkwitz Riley filter. It has 360║ of phase rotation.

Mac
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Scott Carneval

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Re: Choosing the best sub for me
« Reply #106 on: June 23, 2015, 04:05:13 pm »

No, a LR 4 is a 4 pole is a 24dB/oct Linkwitz Riley filter. It has 360║ of phase rotation.

Mac

Gotcha.  I've just always called that a LR-24.
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Ivan Beaver

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Re: Choosing the best sub for me
« Reply #107 on: June 23, 2015, 08:42:15 pm »

"But it does originate at a different degree of phase". That's it!  It clicks now!  Big ups Scott, you nailed it.
Think of it like this.

Lets say you draw a number of different freq sine waves on a graph.

And you start them all at 0 time and 0 amplitude.

Now choose a point anywhere else along the graph.  The frequencies will have all sorts of phase relationships.

There is almost no possibility that they will all be in phase-unless they are all multiples of each others.

Phase is not so much "absolute" but rather relative to something else.
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Jacob Shaw

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Re: Choosing the best sub for me
« Reply #108 on: June 24, 2015, 03:36:07 pm »

Yes Scott, the 360 degrees of phase rotation is what I am referring to.  Mr.linkwitz and mr. Riley developed their filter by putting butterworth filters in sequence in an attempt to address the problems of phase shift and amplitude bump simultaneously, and supposedly it works at certain intervals.  So you should be able to spacially align the drivers and use this type of filter and the drivers will sum just fine as long as they are vertically arranged and in close proximity.
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Mac Kerr

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Re: Choosing the best sub for me
« Reply #109 on: June 24, 2015, 03:49:06 pm »

Yes Scott, the 360 degrees of phase rotation is what I am referring to.  Mr.linkwitz and mr. Riley developed their filter by putting butterworth filters in sequence in an attempt to address the problems of phase shift and amplitude bump simultaneously, and supposedly it works at certain intervals.  So you should be able to spacially align the drivers and use this type of filter and the drivers will sum just fine as long as they are vertically arranged and in close proximity.

The filters will sum correctly at some frequency, but will still be 360║ out of phase. The acoustic summation also depends on the actual response of the speakers, which being different types of speakers will not be the same.

Mac
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Re: Choosing the best sub for me
┬ź Reply #109 on: June 24, 2015, 03:49:06 pm ┬╗


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