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FR Measurments of Line Arrays [message #22672]

Thu, 23 June 2005 09:23

Branwell
Messages: 1
Registered: May 2009

Esquire

Hello,

I am building my first set of line arrays and was wondering if measuring their FR to setup the XO is the same as when one measured point sources ?.

Thanks,

Branwell

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Re: FR Measurments of Line Arrays [message #22677 is a reply to message #22672]

Fri, 24 June 2005 17:46

Earl Geddes
Messages: 220
Registered: May 2009

Master

This is a complex question, but in general the answer is no. You need to know what 'field" you are in. If you measure in the near field and calculate a Xover based on this, then the far field will be incorrect. To get a correct far field you need to measure in the far field. If you only listen in the near field then you could do the crossover for the listening point, but there is no guarantee that it will be correct at other locations. In fact it is just about guaranteed that it won't.

For the best coverage of this topic see my book.

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Re: FR Measurments of Line Arrays [message #22683 is a reply to message #22677]

Mon, 27 June 2005 19:22

Eric J
Messages: 71
Registered: May 2009

Viscount

If you have build this for your living room listening environment, more than likely unless you have an enormous room, you are in the near field. For Prosound, a different matter.

eric j

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Re: FR Measurments of Line Arrays [message #22684 is a reply to message #22683]

Mon, 27 June 2005 20:04

Earl Geddes
Messages: 220
Registered: May 2009

Master

It depends on the height of the array and on the frequency. The near field varies with frequency so yes, it is pretty certain that you are in the near field at higher frequencies, but not at all certain that you are in the near field at low frequencies. Thats what I don't like about arrays. With my speakers I know that I am never in the near field at any frequency.

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Always trade offs [message #22686 is a reply to message #22684]

Tue, 28 June 2005 05:23

Eric J
Messages: 71
Registered: May 2009

Viscount

There are always trade offs. I happen to like the trade offs of array systems over point sources, but nothing is every perfect.

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I don't agree [message #22687 is a reply to message #22686]

Tue, 28 June 2005 06:32

Earl Geddes
Messages: 220
Registered: May 2009

Master

I am not sure what "tradeoffs" you are refering to. In what way would you claim that, in a small room, a line array (I assume you are talking about a line) has an advantage? In large PA systems there is one having to do with the power capability of using multiple cabinets, but in a small room I do not see the advantages that an array offers.

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Troll? [message #22688 is a reply to message #22687]

Tue, 28 June 2005 08:28

Eric J
Messages: 71
Registered: May 2009

Viscount

Excuse me....just a small question.

This is a board specifically for those who want to use line arrays. Why are you trolling the board with your views? Why don't you go to one of the audio boards which has your view?

Why bother wasting your time being a troll here?

Just FYI, assuming that you are not a troll, and really want to know: reasons:

1. Higher sound pressure levels,
2. reduction of distortion as power is dispersed among several drivers,
3. higher power handling attained,
4. much widers sound stage,
5. near constant sound levels throughout the listening room,
6. an image sweet area as opposed to a sweet spot,
6. much much greater dynamic level recreating the live event much more effectively.

And if, as in proaudio, you use electrical crossovers and separate amps the for mid/woofer array, the tweeter array, and the subwoofer, you will hear something really spectacularly like the real performance, and very much different than a single spot speaker.

I suggest that you go to James R. Griffin (PHD)'s white paper on "design guidelines for practical near field arrays".

eric j

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Re: Troll? [message #22689 is a reply to message #22688]

Tue, 28 June 2005 09:25

Wayne Parham
Messages: 18789
Registered: January 2001

Illuminati (33rd Degree)

I don't think that's fair. I respect Jim Griffin a great deal and I also respect Earl Geddes a great deal. You may not agree with Geddes comments, but it isn't like he said "arrays suck." Dr. Geddes simply made the statement that he doesn't see an advantage in small rooms. Maybe he means rooms that are too small for the array. With a little more specificity, you might find you actually agree with him.

In his book, Audio Transducers, Geddes investigates arrays and describes their directivity and acoustic behavior. So it isn't as if he were new to these concepts.

Audio Transducers, by Dr. Earl Geddes

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Most of the discussion centers [message #22690 is a reply to message #22687]

Tue, 28 June 2005 09:29

Eric J
Messages: 71
Registered: May 2009

Viscount

A lot of discussion centers around this white paper by James Griffin, PHD.

Perhps you could read it and then discuss it with Dr. Griffin:

http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

eric J

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Re: Troll? maybe not! [message #22691 is a reply to message #22689]

Tue, 28 June 2005 09:34

Eric J
Messages: 71
Registered: May 2009

Viscount

Wayne,

I'm no expert, but in so many words he did say Line Arrays Suck.

I would hope that he could clarify his statement with something of substance. For him to say that he didn't know of any ways that they worked, when even non audio engineers know lots of ways that they are really superior (and some ways they are not), sounds like a troll.

Perhaps Dr. Geddes and Dr. Griffin could have a substantive discussion that would enrich us all.

Taking pot shots at line arrays on a line array discussion board is called Trolling. A rose is a rose no matter what.

I may in fact agree with him too, if he could only take a little time to enlighten us peons with advanced degrees in other subjects than audio engineering.

Thanks.

eric j.

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