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Multi-Way Conventional loudspeakers with crossovers

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Old 9th August 2007, 01:26 AM   #131
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Quote:
Uh, Danny, perhaps you should read post 53...I pretty much summarized correctly how the energy storage would look.
Ah, no not really. For one, you didn't attempt to answer either of the posted questions.

This one (below) was good. It was rather obvious and I hoped someone would at least catch that part.

Quote:
The red and blue curves have the best energy storage below 1k.
But then you basically said the same thing about the green one too.

Quote:
The green will have energy storage issues below 1k
And you obviously missed that one.

The sharpest thing you said was this:

Quote:
Second, a nearfield measurement, while helpful below 1k, has to be interpreted very carefully above 1k due to the interference nulls that will occur that aren't really there.
This was very correct and this issue is clearly present on two of the curves.

Your buddy Zaph noticed this when he measured our M-130 woofer several years ago and had no idea what it was. He even posted it on the Madison board asking about it. Even after I told him what it was he still posted on his site that the driver had a suck out at 1,900Hz.

Quote:
John used a CSD to show that the drivers are virtually identical after the XO transfer function is applied and this despite having rather different FR's. The whole point was to show the irrelevance of the CSD in this case. I thought he made a good point.
Yea, but he took two drivers that had almost the same energy storage in that range.

What if the metal cone driver would have looked like this one?

Click the image to open in full size.

Even if the crossover were steep enough to get rid of some or most of the break up in the upper end, it would still have quite a bit of stored energy below 3kHz where it would be used. You also wouldn't know from this drivers frequency response that it had excessive stored energy below 5kHz.

Click the image to open in full size.

Quote:
It seems from your post #127 that to an ignorant novice like me,
That would not be the case.

Quote:
1. violent changes in frequency response shows stored energy that one can see in the CSD... When there is a zig-zag, there is stored energy issues one can then expect to see in the CSD.
Sure, sometimes it is really easy to see. The point in posting those easy to discern examples was just to try and get a response from those that were so confident in reading a CSD from a frequency response. No one attempted to answered the simple questions.

Quote:
For example - when the FR is smooth, the CSD drops away quite quckly.
Not necessarily. See the example posting just above in this response.

Keep in mind though that driver with a large amount of mass playing to the same level as one with a lighter weight mass can have just as smooth of a response but more stored energy than the driver with the lighter weight mass. You won't see this in the frequency response either.
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Old 9th August 2007, 02:40 AM   #132
ucla88 is offline ucla88  Tahiti
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Hi Danny,

The green does have energy storage issues below 1k. You don't understand the math and thus, because it's not obvious in the waterfall, it's not there. But it's there in the FR. That's the whole point, which again, you remain ignorant of.

I stand by my analysis of the curves. It in fact, is somewhat more insightful than just blinding looking at the CSD's.


Spend a little more time reading Fourier theory.
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Old 9th August 2007, 03:53 AM   #133
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First there is no accuracy below 1khz and now you see stored energy that doesn't even show up in the CSD.

I think we are done here. I certainly am.
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Old 9th August 2007, 05:32 AM   #134
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I said I wouldn't bring myself into the debate but I can't help myself...

Quote:
For example - when the FR is smooth, the CSD drops away quite quckly.

Not necessarily. See the example posting just above in this response.

Keep in mind though that driver with a large amount of mass playing to the same level as one with a lighter weight mass can have just as smooth of a response but more stored energy than the driver with the lighter weight mass. You won't see this in the frequency response either.
That makes sense. I agree.

I certainly cannot calculate and visualise in my head the CSD from the FR. I can guess, but don't know what it would be like exactly without applying the math for a minimum phase device.

I agree with Danny on that point.

However, I agree with all others, that if a CSD can be mathematically derived from an FR curve, then one should tell you the other. But - you have to be able to run the math to generate. You can't just visualise in your head.I think that is what Danny is pressing for here.... and for that I agree.

One thing I've learned about Zaph's comments like anyone experienced in a field is he specifies the result / conclusion. As a newbie you have to understand their is a reason or logic behind that conclusion. To explain would involve describing all the theory which would take no small amount of time. Zaph often states things that people might take in an inflammatory way. I like the way he specifies a "black or white" view..... (says me sitting on the fence

one thing for sure - both views have enlightened my understanding and learnning in this area. I appreciate the time and explanations Mark, Zaph, Danny, Dave (and others) have contributed.

David.
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Old 9th August 2007, 07:59 AM   #135
kstrain is offline kstrain  Scotland
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Default Minimum phase

It is hard to see without a phase plot (which is unecessary if the system is minimum phase) but is the "Blue curve" in Danny's examples above minimum phase at the zero(s) near1.8kHz?

Looks to me that it might not be.

Ken
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Old 9th August 2007, 10:41 AM   #136
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Default Re: Minimum phase

Quote:
Originally posted by kstrain
It is hard to see without a phase plot (which is unecessary if the system is minimum phase) but is the "Blue curve" in Danny's examples above minimum phase at the zero(s) near1.8kHz?
Result of the narrow deep notch and not necessarily an indication of nonminimum phase behaviour, already explained here:
http://www.diyaudio.com/forums/showt...82#post1273682

Since you brought up, notice the original smoothed FR curves for those didn't show those narrow notches. But they would out of mysterry would show as ringing on the CSD's, and then a claim could have been made that "see nothing relating to FR but the CSD shows the ringing" if the unsmoothed FR plots weren't requested here And seeing (or foreseeing) this, why would anyone answer to a challenge which the question was ambigious to start with: which driver has most energy storage. How do you quantify energy storage of a driver. You can't do it without reference to frequency, because it is not just about time to decay, it is about how many osciallations it takes to decay. Response diminishing after 5 oscillations at 200Hz has same stored energy problem as response diminishing after 5 oscillations at 2Khz, but one takes 25 msecs, the other 2.5msecs.

Quote:
]Originally posted by DannyYou also wouldn't know from this drivers frequency response that it had excessive stored energy below 5kHz.
What determines "excessive" stored energy? That is my point in the above paraghraph in this post. Your point of quantifying energy storage is different from mine, and from probably others here. Why would anyone answer your challenge, when your interpretation of the answer will be different, or suspect of your interpretation? And also I have posted twice on this thread before that that driver's FR is not so smooth below 5Khz, and it is no suprise that CSD will show up like that below 5Khz.
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Old 9th August 2007, 03:09 PM   #137
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Quote:
That is my point in the above paraghraph in this post. Your point of quantifying energy storage is different from mine, and from probably others here. Why would anyone answer your challenge, when your interpretation of the answer will be different, or suspect of your interpretation?
You are correct. I purposefully used a question with a subjective answer. Not to catch or trick anyone. That wasn't the point. Reading the stored energy from the frequency response alone is subjective. In some cases a guess at best. By simply asking "how much" it allows one to use their own measure and not mine.

I am surprised Mark took a shoot at it. I really didn't think anyone would respond. Some of these are guys are just trying to win an argument, are more afraid of being wrong, and wouldn't take a shoot at it even if the differences were really obvious and easy. My example using two 8" woofers were about as different as two woofers could get, and still nothing.

I think this thread has run its coarse. Several mentioned learning something from this thread so maybe some good has come of it all. People can make their own minds as to the usefulness of a CSD. Thanks to all that participated. I do have a lot of respect for many of the contributors even those that were combative with me. Good stuff here from Pete, Feyz, theSuede, Mark, Dave, and others. See ya.
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