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Author Topic: How accurate is...  (Read 1259 times)

Ivan Beaver

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Re: How accurate is...
« Reply #10 on: August 10, 2014, 01:51:21 pm »

Ah ok, that makes sense.

I thought that max power was showing how much power the speaker can handle at a given frequency without exceeding xmax.

So, when looking at max excursion, the line being drawn is the drivers excursions at those frequencies?

The objective is to try and keep that line from passing the drivers xmax?

Is the excursion graph equal in its increments or is it calculated some other way?

I ask because even the driver that comes with the box is over 8mm xmax in its operating frequency.
The excursion of a loudspeaker will vary quite a bit depending on the freq-even if the same VOLTAGE is applied.

Of course the impedance varies with freq-so even with the same voltage applied-then the power will vary with freq.

XMAX can actually mean different things.  X lim or X dam is the point at which failure will occur.

The XMAX is considered to the maximum excursion at which some point the manufacturer considers to be "non linear".  But the driver can move more than that if pushed harder-but still not be damaged.  But the sound quality will suffer.
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Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Paul G. OBrien

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Re: How accurate is...
« Reply #11 on: August 11, 2014, 10:41:53 am »

The excursion of a loudspeaker will vary quite a bit depending on the freq-even if the same VOLTAGE is applied.

And that is a key point, amplifiers are constant voltage devices so the frequency that produces xmax in the driver first represents the voltage limit for all frequencies, because it would take some very special feedback processing to protect the driver at higher drive voltages. So in other words, when you look at the max power graph in WinISD the lowest point on that graph should be considered the maximum average drive level you can safely push to the speaker.
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Art Welter

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Re: How accurate is...
« Reply #12 on: August 11, 2014, 03:57:39 pm »

1)So, when looking at max excursion, the line being drawn is the drivers excursions at those frequencies?
2)The objective is to try and keep that line from passing the drivers xmax?
3)Is the excursion graph equal in its increments or is it calculated some other way?
Aaron,

Looking at the models of the same driver in different size enclosures with different Fb (tuning frequency) will help you to understand the differences:

http://www.eminence.com/pdf/Definimax_4018LF_cab.pdf

You will notice the large boxes go lower with less power, but will also hit Xmax at lower power. Also note the large impedance rises each side of Fb, where cone displacement is at minima. Last year I mentioned to you that the excursion can easily be seen (and measured) by eye with a white dot on the cone. I failed to answer your question of what to use for the dot, but a silver Sharpie pen, "Liquid Paper", "Wite-Out", or any of a variety of paint pens or paint using a small brush all work well.

When you actually measure, you will notice that due to the rising impedance and suspension stiffness, most "PA" type drivers do not actually have as much increase in excursion below Fb as predicted, though distortion below Fb still will skyrocket.

1) "Max Excursion" would be Xlim, or Xmech, often as much as double Xmax, which is linear excursion. Above Xmax, simulations are fairly useless, since they assume a linear excursion far past reality.
2) In general there is no reason to simulate excursion above Xmax, as it won't represent what actually happens with excursion.
3) Excursion graph increments are notated either in mm or fractions of an inch in equal increments.

Art
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Aaron Weidner

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Re: How accurate is...
« Reply #13 on: August 13, 2014, 10:27:26 am »

Aaron,

Looking at the models of the same driver in different size enclosures with different Fb (tuning frequency) will help you to understand the differences:

http://www.eminence.com/pdf/Definimax_4018LF_cab.pdf

You will notice the large boxes go lower with less power, but will also hit Xmax at lower power. Also note the large impedance rises each side of Fb, where cone displacement is at minima. Last year I mentioned to you that the excursion can easily be seen (and measured) by eye with a white dot on the cone. I failed to answer your question of what to use for the dot, but a silver Sharpie pen, "Liquid Paper", "Wite-Out", or any of a variety of paint pens or paint using a small brush all work well.

When you actually measure, you will notice that due to the rising impedance and suspension stiffness, most "PA" type drivers do not actually have as much increase in excursion below Fb as predicted, though distortion below Fb still will skyrocket.

1) "Max Excursion" would be Xlim, or Xmech, often as much as double Xmax, which is linear excursion. Above Xmax, simulations are fairly useless, since they assume a linear excursion far past reality.
2) In general there is no reason to simulate excursion above Xmax, as it won't represent what actually happens with excursion.
3) Excursion graph increments are notated either in mm or fractions of an inch in equal increments.

Art

Thank you for the information guys.

Art, i just now remembered you saying that.

Ill have to give it a try some time this week just to see what it says.

Thank you all for the help, it is much clearer now. Sorry for my absence, i decided to take paul's advice and did some forum surfing.

I have decided to build 2 othorns over 2 dual 18 inch designs.

My thoughts are:

2 dual 18 inch cabs will take up more space in the trailer.

The othorns are more efficient due to their design and will be comparable in performance.

The othorns will offer less distortion.

the othorns will get me more sound for the power applied over a bass reflex dual 18.

Cost to build is going to be close to the same.

Either way i build, it will blow my current subwoofers out of the water.

If i need to be corrected please feel free. Of course any and all information is helpful.

Has anybody here had experience with the othorn?

I also thought of this last night. I see online that people commonly say "delay horn loaded subs".

If the subs are on line or in line with the mains, shouldn't it be the mains that are delayed due to the length of the horn?

Thanks :-)
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Ivan Beaver

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Re: How accurate is...
« Reply #14 on: August 13, 2014, 01:01:04 pm »


I also thought of this last night. I see online that people commonly say "delay horn loaded subs".

If the subs are on line or in line with the mains, shouldn't it be the mains that are delayed due to the length of the horn?

Thanks :-)
You are correct.  Except often the delay is more than the physical path length of the horn-it should also address it should also address the phase shift (delay) associated with the low pass filter on the subs.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Aaron Weidner

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Re: How accurate is...
« Reply #15 on: August 13, 2014, 03:15:45 pm »

You are correct.  Except often the delay is more than the physical path length of the horn-it should also address it should also address the phase shift (delay) associated with the low pass filter on the subs.

Oh my.. didn't know about that. I normally cross over around 80hz, would there be a way of hearing that somethings wrong? Lack of bass, low mid ect... Its a mobile rig and i usually only get at most an hour to set everything up. Is there a way to rough it in? Would something that technical would require actual classes and gear to fix?
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Ivan Beaver

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Re: How accurate is...
« Reply #16 on: August 13, 2014, 05:11:51 pm »

Oh my.. didn't know about that. I normally cross over around 80hz, would there be a way of hearing that somethings wrong? Lack of bass, low mid ect... Its a mobile rig and i usually only get at most an hour to set everything up. Is there a way to rough it in? Would something that technical would require actual classes and gear to fix?
The typical answer is "it depends" and in this case it depends on the particular loudspeakers in use (subs and tops).

The only way to properly see what is going on with the phase is with a modern measurement system that will show phase.  An RTA will not.

Other than that it is a guess-which could be right at one freq and wrong at others.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Aaron Weidner

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Re: How accurate is...
« Reply #17 on: August 13, 2014, 06:37:54 pm »

The typical answer is "it depends" and in this case it depends on the particular loudspeakers in use (subs and tops).

The only way to properly see what is going on with the phase is with a modern measurement system that will show phase.  An RTA will not.

Other than that it is a guess-which could be right at one freq and wrong at others.

What are some modern measurement systems?

I would more than likely never be able to afford one, but it would be nice to know.

Does it boil down to, theres not much i can do about it and set it with my best guess?

Would getting it close or at least setting the delay for the horn be better than not doing anything at all?

almost makes me want to go back to a bass reflex subwoofer, or does it not matter what type of subwoofer is used?
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Art Welter

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Re: How accurate is...
« Reply #18 on: August 13, 2014, 07:12:43 pm »

1)Oh my.. didn't know about that.
2)I normally cross over around 80hz, would there be a way of hearing that somethings wrong?  3)Is there a way to rough it in? Does it boil down to, theres not much i can do about it and set it with my best guess?
4)Would something that technical would require actual classes and gear to fix?
5)What are some modern measurement systems?
6)Would getting it close or at least setting the delay for the horn be better than not doing anything at all?
7)Almost makes me want to go back to a bass reflex subwoofer, or does it not matter what type of subwoofer is used?
1) You would have, had you remembered my response to your question two days ago  ::).
2) Improper time/phase alignment results in a lack of coherency in the crossover region, normally a lack in "punch".
3)Check out #6 here:
 http://forums.prosoundweb.com/index.php/topic,84305.0.html
4) If you could retain the information, classes would help.
5) Smaart, Systune, Tef and many others. All the response curves you have seen me post use Smaart.
6) Yes, getting in the ballpark is better than being stuck in traffic  ;).
7) Every system benefits from alignment, but BR don't require as much top delay as a long TH or FLH.

Once you set the alignment, as long as the top speakers are stacked above the subs, the alignment won't change, though proximity to boundaries (walls, floor, ceiling) may require EQ changes which can be done "to taste".

Art
« Last Edit: August 13, 2014, 07:17:58 pm by Art Welter »
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Ivan Beaver

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Re: How accurate is...
« Reply #19 on: August 13, 2014, 07:18:08 pm »

What are some modern measurement systems?

I would more than likely never be able to afford one, but it would be nice to know.

Does it boil down to, theres not much i can do about it and set it with my best guess?

Would getting it close or at least setting the delay for the horn be better than not doing anything at all?

almost makes me want to go back to a bass reflex subwoofer, or does it not matter what type of subwoofer is used?
Even bass reflex cabinets generally need the full range cabinets to be delayed.  It is just the time that is different.

Horn subs tend to have less distortion-so there is not as much interference above the crossover point with the full range cabinets.

Some "Modern measurement systems" include (but not limited to)  Smaart-Systune-Easra-TEF and more.

There are several aspects to cost.  Obviously is the program.  You will also need an interface to get the signals in and out of the computer-a measurement mic.

But the most important aspect is the KNOWLEDGE/SKILL to use it.

Knowing what you can and can't fix and what is causing it is the biggest thing that most people stumble on.  Classes are offered (again at a cost) that help.

But just attending a class will not make you an expert (non of us are).  In fact most people have more questions when they come than when they went in.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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