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Old 1st August 2007, 02:14 PM   #91
PB2 is offline PB2  United States
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Default Re: Re: Re: Re: Re: There's little agreement as to which is best

Quote:
Originally posted by dlr


Don't presume that every word written at a board is for your edification alone. Lack of precision and thoroughness tends to leave things such that misinterpretation results. That may be the case here to some degree and I think that I may see why we're going around in circles.

....
Dave
[/QUOTE]


You quote me, make a direct reply, suggest that I need to be edified (LOL) and lack precision and think you alone hold the rigorous proofs and facts. Then claim that you're statements are not directed at me. If that is the case then don't quote me and don't try to spin what you say. Say what you mean and mean what you say. I find your comments offensive and I'm going to stop reading you at this point, it is a waste of time. You go rambling off topic, also claim that the example you choose to discuss is not the subject of this thread. My point is not about specific examples anyway, it is about the theory that you demand is rigorously true as you apply it, when it is not. You are the one who needs to read and learn thanks, rather than suggesting it to me. I joined the AES over 30 years ago, yeah I read the article thanks, and have spoken directly to Witold.

Several here spout a linear systems theorem, pound their fist and say this is the rigorous truth, when in fact if they opened their eyes they might notice that it is only an approximation. I've said it enough times, several here seem to think they are the only ones with the facts and offer offensive comments to those who offer a more accurate view.

Pete B.
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Old 1st August 2007, 02:45 PM   #92
dlr is offline dlr  United States
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Default Re: Re: Re: Re: Re: Re: There's little agreement as to which is best

Quote:
Originally posted by PB2
You quote me, make a direct reply, suggest that I need to be edified (LOL) and lack precision and think you alone hold the rigorous proofs and facts. Then claim that you're statements are not directed at me. If that is the case then don't quote me and don't try to spin what you say. Say what you mean and mean what you say. I find your comments offensive and I'm going to stop reading you at this point, it is a waste of time. You go rambling off topic, also claim that the example you choose to discuss is not the subject of this thread. My point is not about specific examples anyway, it is about the theory that you demand is rigorously true as you apply it, when it is not. You are the one who needs to read and learn thanks, rather than suggesting it to me. I joined the AES over 30 years ago, yeah I read the article thanks, and have spoken directly to Witold.

Several here spout a linear systems theorem, pound their fist and say this is the rigorous truth, when in fact if they opened their eyes they might notice that it is only an approximation. I've said it enough times, several here seem to think they are the only ones with the facts and offer offensive comments to those who offer a more accurate view.

Pete B. [/B]
I was not intending to be offensive and since you took it as such, for that I apologize. At times my writing is not as clear as I would like it to be. I do still have disagreements with your take on some aspects as I explained them, but we will have to agree to disagree on those. My intent on writing as I did was to say that there are others reading as well and at times it is helpful to "speak to the group" even though it's in a direct reply to a single person.

I do think that I made statements in earlier posts that explained my position such as the one on the nonlinear aspect being a separate issue from my focus of discussion in the thread.

To quote myself that was in response to Danny, not you:

Quote:
Motor non-linear distortion, as I pointed out earlier, is certainly a consideration in a driver, but that's a totally separate issue WRT linear distortion.
As for the topic, I have focused on a more narrow aspect, primarily the CSD and the FR in general. If you would re-read my first post on page 1, you'll see what drew me into it in the first place. It was not based on the first posters questions, it was as I just said:

Quote:
I separated the two because the original thread veered off into parts with one being on the absolutes of a CSD vs. FR. Even within that sub-thread, so-to-speak, I pointed out specifically the issue of the nonlinear distortion impact, but did not care to go down that path as the discussion was focused on the linear distortions.
I'm not trying to spin. This is what I said and I tried to explain why.

Dave
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Old 1st August 2007, 03:22 PM   #93
PB2 is offline PB2  United States
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Quote:
Originally posted by ucla88
Hi Pete,

I know we seem to be talking past each other. If so, then my comments are for others.

But you're having trouble clearly distinguishing between linear and nonlinear distortion.

Linear distortion is just amplitude distortion and can be corrected.

Nonlinear distortion is an entirely different phenomena and is dominated by the motor and excursion. Nonlinear distortion cannot be equalized, or at least not easily. (servo feedback, etc. There are ways of eq'ing or mitigating NL distortion)

However, directly connecting the amplitude of cone breakup and nonlinear distortion is incorrect.

Cone breakup may be responsible for some nonlinearities and in fact this can be measured. But it is not the dominant factor in nonlinear distortion.

If you're talking about nonlinear phenomena, you cannot make the assumption that "soft breakup" of a paper dome over a wide frequency range has less nonlinear distortion than "hard breakup" associated with a metal cone. You are mixing the amplitude distortion (read, linear distortion) with any nonlinear phenomena.

There has been no experimental data on nonlinear distortion and cone breakup presented anywhere in this thread. I've actually been trying to use some close thirds measurements to see if I can find any experimental correlation of breakup and nonlinear distortion. This would not show in a CSD. More on that someday, when I have time. Still, it seems that the low end/excursion dominates.

It is an error to assume more severe linear distortion implies more severe nonlinear distortion.

Many metal cones have clearly better nonlinear distortion than their paper counterparts. Look at the Seas datasheets for the metal and non metal seas drivers. It is quite clear that the metal cones have better nonlinear numbers, regardless of their fr/csd.

edit-didn't see Feyz' post. He said the same more succinctly...

If your comments are for others then *please* direct them to someone else, I find your comments offensive. You think that I cannot distinguish between linear and non-linear, hmmm no one else here seems to think that in my long thread on amplifiers, or my contributions to other threads, so where do you get off making this claim? The fact is rather, that you seem to think you can divide them, oh let's look at the linear case now, now flip a switch and look at the non-linear. That is not the nature of real systems, looking at the linear case is an approximation. Now I'll stop reading you thanks, go ahead and try to get the last word in, you can have it.

Just let me add that it seems that we are reading different data for the SEAS drivers, I don't see any support of your claims above.
The L18 alone does not support your claim that the cone breakup does not add it's own distortion. It may be at HF, but the fact is that it is there. A few here seem to have trouble understanding how breakup can produce harmonics. Do you think a bell rings as a sine wave, no it has harmonics and so do many cones with break up modes. This is easily seen through careful inspection of the L18 FR and distortion data, and there are many other examples that I've been looking at for over 20 years. Now, I have no interest in an unproductive debate about this, it is my view, since you make discussion difficult I'm going to say take it or leave it. I did not bring it up earlier because it was not required to make my point.

Now I really hope to drop this, I just don't have the time for a back and forth.

Why don't we agree to disagree.

Pete B.
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Old 1st August 2007, 03:23 PM   #94
PB2 is offline PB2  United States
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Default Re: Re: Re: Re: Re: Re: Re: There's little agreement as to which is best

Quote:
Originally posted by dlr


I was not intending to be offensive and since you took it as such, for that I apologize. At times my writing is not as clear as I would like it to be. I do still have disagreements with your take on some aspects as I explained them, but we will have to agree to disagree on those. My intent on writing as I did was to say that there are others reading as well and at times it is helpful to "speak to the group" even though it's in a direct reply to a single person.

I do think that I made statements in earlier posts that explained my position such as the one on the nonlinear aspect being a separate issue from my focus of discussion in the thread.

To quote myself that was in response to Danny, not you:



As for the topic, I have focused on a more narrow aspect, primarily the CSD and the FR in general. If you would re-read my first post on page 1, you'll see what drew me into it in the first place. It was not based on the first posters questions, it was as I just said:



I'm not trying to spin. This is what I said and I tried to explain why.

Dave

Yes Dave, We can agree to disagree, this is fine thanks!
Pete B.
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Old 1st August 2007, 03:44 PM   #95
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Quote:
I was not intending to be offensive and since you took it as such, for that I apologize. At times my writing is not as clear as I would like it to be.
Hey Dave, my writing is not always clear as to what I intend either, and you jumped all over me for it too. Sorry dude, I will try to be more clear, but you have to ease up on the decisiveness.

I will catch up more on this thread later. I have business to tend to .
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Old 1st August 2007, 08:02 PM   #96
rjb is offline rjb  New Zealand
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Now that the various (Designer) participants have beaten each other to death, can I make the following points for the average DIY'er

1) Any published Frequency Response curve alone is inadequate to make a choice of driver- the resolution is not good enough, and certainly not adequate to indicate all problem areas.

2) the CSD helps considerably to fill in the missing data, and by showing information in a way that is easy to recognise, so are useful even if some areas are suspect, or duplicate info in the FR..

3)) Impulse testing adds even more information, and we ignorant peasants need all the help we can get

4) ALL published data is suspect, and at best should be considered as useful for comparision purposes when taken by the same person under the same conditions, a point Zaph makes often on his site.

5) All designs are trade-offs, and your choice will probably not be mine

So to all those that pubish information, the more information you provide, (particularly on conditions of testing, the better.
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Old 1st August 2007, 08:06 PM   #97
ucla88 is offline ucla88  Tahiti
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Hi Pete,

I think we can agree to disagree. I made my comments above because I don't think I'm going to change you or Danny's mind. However, a lot more folks read and participate. I throw my view out, not only to beat a dead horse, but so the lurkers can read both viewpoints and make up their own mind.

I've interpreted the data and math one way, you another. And that's ok. Everyone else can read the posts, the references, and seek a deeper understanding on their own.

mark
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Old 4th August 2007, 02:00 PM   #98
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Well, I think you guys have had plenty of time to answer those two simple questions:

Quote:
1) In each graph what area has the greatest amount of stored energy?

2) Of the three graphs which woofer has the greatest amount of stored energy and where?
It looks like the only accurate prediction was mine:

Quote:
Here is mine: The guys that pushed the hardest to claim that they can tell you what will be in the CSD by looking at the frequency response won't respond.
What's the matter fellows? No one wanted to step up to the plate. Zaph? No attempts?

First it was... We can't tell anything from the graphs because of the third octave smoothing. So then I post the curves with no smoothing, and still nothing.

Here, I'll give you guys an easy one.

Two 8" woofers. Measured at 1 meter. Both mounted in the same box (9" wide and 14" tall). No smoothing applied.

Click the image to open in full size.

Click the image to open in full size.

Obviously one has more stored energy than the other.

One simple question this time.

1) Does the frequency response tell you how much stored energy is present?
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Old 4th August 2007, 03:02 PM   #99
dlr is offline dlr  United States
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Default Unreliable measurements

Danny, this is nothing but attempts at "gotcha". First you post tainted measurements, more than once, now you post measurements that are questionable again. The first set started at almost 0ms going to about 4ms. Now these start at 2.88ms and go to 7.85ms. There's no consistency and no way to believe that these are proper. It's a waste of time debating you. This is characteristic of your tactics. They are not meant to enlighten.

You will not respond to direct question and comments, at times you just start all over again as you have here. You used this tactic previously. I know that I have no confidence in your posted measurements at this point. That's probably one reason why Mark and zaph stop. As I will now as well with this final post.

You find useful data in a CSD. The set of measurements that you posted do not include enough time data to make them useful were I to care about the CSD. They have zero impact on my design decisions because I can see everything I need to see in the FR, as I said. Supplement that with good distortion measurements, such as those that zaph and Mark provide and there's no need for any CSD of any kind.

The CSD has no bearing as much because the CSD of a raw driver is almost immaterial to the final result. Optimizers work on the FR. The designer chooses an the bandpass Fc's to mitigate known distortion issues and FR anomolies. The CSD with a well-designed XO will be nothing like the raw one. I will be making that point evident when I put up my page on the 2-way I'm playing with now. I hope to get something initial this weekend, but if not it will go up soon. It will belie much of what you originally were claiming. And as I said, to satisfy those who just must see them, I'll even be providing CSDs. But those CSDs will probably surprise those who put faith in CSDs as providing some sort of exceptional insight into the driver. They don't if you know what you're doing. That's not meant to offend, it's just how I feel.

This is my last post here. I have too many other things to do to waste more time, which is unfortunately what this now is. Claim whatever victory you want and congratulations.

Dave
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Old 4th August 2007, 03:27 PM   #100
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Quote:
Danny, this is nothing but attempts at "gotcha".
If it shows that you can't back up what you've claimed than for you I guess it is.

Quote:
First you post tainted measurements
Not true again. Measurements posted were just as I intended.

Quote:
now you post measurements that are questionable again.
Not true again. Consistent with industry standards.

Quote:
The first set started at almost 0ms going to about 4ms.
If you'd have put two and two together when I said they were near field measurements then the gated time window would have made sense to you.

Quote:
Now these start at 2.88ms and go to 7.85ms.
Yep, the gated time window started just before the arrival of the impulse response and ended right before any first reflections from the room. You got a clean 5ms time window to view. Is that not enough for you? It will be for this example.

Quote:
The CSD has no bearing as much because the CSD of a raw driver is almost immaterial to the final result.
My measured data will show that not to be true as well.

Quote:
The CSD with a well-designed XO will be nothing like the raw one.
In some areas, I agree, but not so in other circumstances.

Good luck with all of that Dave. I look forward to hearing it at the next big audio show.
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