I know I won't change Danny's mind, but a few comments to everyone reading this thread are in order.
Again, windowing an impulse is a very unnatural event. There is significant error introduced by the windowing process. Due to the way the impulse is chopped up, subtle changes are just as likely due to the way the impulse is windowed as anything else.
For example. None of the CSD's offer much relevant information below 1k. Most of what you see is heavily distorted by the windowing. Making audibility judgements based on measurement like this are questionable.
Most of the CSD's behavior above 1k can be more or less predicted by the FR. Now Danny has made some subtle points about resonances that "don't show up in the FR curve." Well, if they don't show up in the FR curve, and the FR and impulse are one and the same, perhaps we should wonder if the effect is artifactual.
I have spent a lot of time looking at CSDs, SL style tonebursts, and as detailed FR curves as I can on my site. I think you'll find a careful analysis will show the majority of what you need to know about stored energy will be found in a detailed FR curve. You're better off going outside and making a 12 ms FR measurement than post processing your 3ms in room measurement and thinking you can pick out the stored energy in any detail.
Also, be aware that what "looks bad" on an FR curve or CSD is not exactly what sounds audibly offensive. Google O'Toole's whitepapers at harman and read about resonance audibility-how they measure it and study it's audibility.
Anyway, forget about what Danny and I have to say and look at the links/research it yourself.
Again, windowing an impulse is a very unnatural event. There is significant error introduced by the windowing process. Due to the way the impulse is chopped up, subtle changes are just as likely due to the way the impulse is windowed as anything else.
For example. None of the CSD's offer much relevant information below 1k. Most of what you see is heavily distorted by the windowing. Making audibility judgements based on measurement like this are questionable.
Most of the CSD's behavior above 1k can be more or less predicted by the FR. Now Danny has made some subtle points about resonances that "don't show up in the FR curve." Well, if they don't show up in the FR curve, and the FR and impulse are one and the same, perhaps we should wonder if the effect is artifactual.
I have spent a lot of time looking at CSDs, SL style tonebursts, and as detailed FR curves as I can on my site. I think you'll find a careful analysis will show the majority of what you need to know about stored energy will be found in a detailed FR curve. You're better off going outside and making a 12 ms FR measurement than post processing your 3ms in room measurement and thinking you can pick out the stored energy in any detail.
Also, be aware that what "looks bad" on an FR curve or CSD is not exactly what sounds audibly offensive. Google O'Toole's whitepapers at harman and read about resonance audibility-how they measure it and study it's audibility.
Anyway, forget about what Danny and I have to say and look at the links/research it yourself.
AT LAST!!!!!!!
The content of the debate was indicative.
Yes, but you were trying to use just such measurements and that measurement range in part to argue your position. This correctly says that your previous argument in this frequency range was based on questionable measurement accuracy and precision. This is what I would call misleading.
This is a strawman argument. I made no such reference. You're arguing for the sake of arguing with this.
Yes! But it's more than that. The impulse resposne can be reproduced from the frequency response. Just do an inverse FFT.
The CSD is only of value to those who do not see the information in the FR. As John said, the CSD is nothing more than the FR in another form. I have no need of the CSD as I can see what I need to see in the FR.
Danny said:
The content of the debate was indicative.
Yes, but you were trying to use just such measurements and that measurement range in part to argue your position. This correctly says that your previous argument in this frequency range was based on questionable measurement accuracy and precision. This is what I would call misleading.
This is a strawman argument. I made no such reference. You're arguing for the sake of arguing with this.
Yes! But it's more than that. The impulse resposne can be reproduced from the frequency response. Just do an inverse FFT.
The CSD is only of value to those who do not see the information in the FR. As John said, the CSD is nothing more than the FR in another form. I have no need of the CSD as I can see what I need to see in the FR.
Unnutural event?
Now that is funny.I have measured drivers in and out of my anechoic chamber and can get identical results in this regard. It is necessary to gate or limit a time window to get meaningful information when looking at a spectral decay. Why look at a 60ms time window if the impulse response only last for 2 to 3ms?
The only way you can alter or chop up the impulse response where as to alter the data is to not catch all of it. If the impulse is 2ms long then chopping it at 1.8ms would alter it. Looking at a 4ms time window will not.
Not true. And why try to predict it when you can look at it? That makes no sense.
Just look at the examples I posted from Zaph's measurements. There are differences in the amount of stored energy from one driver to the next where both drivers show a flat response with no breakup at all.
Ah, now I have made a point and it is subtle.
So if a made a subtle point about resonances that you do not see in the frequency response measurement then how do you know they are there only by looking at the frequency response? Are you kidding? Good grief!
Oh gee! The frequency response curve only displays maximum amplitude per frequency range. It does not display a time element. Are you sure you understand this? The entire impulse response without reflections from anything might only be 2 to 3ms long with a 1 watt input. How much more dead air space do you need beyond the initial impulse response?
Dave, you are just playing semantics and missing the point.
Not true. See next response.
Yea, in a form that includes a time element that the frequency response does not include.
Good luck to you Dave. I am sure you don't even need to listen to it either. You'll know what it sounds like.
And from looking at these two frequency responses how do you know that from 3kHz and down one has a lot of stored energy and the other doesn't?
I know you have seen a lot of them and you probably won't need to see these, but for the sake of everyone else here are the CSD's again.
Well, I at least, am very inexperienced in this whole area of 'reading FR graphs', and I must say that I've learnt a lot about them in this thread, and have learnt a lot about 'reading' csd graphs as well.
I most certainly do NOT want to get into (what seems to be developing as) the unfortunate debate that is going on, but now after reading this thread (and the links within it) I am grateful for what I have learned and would like to say that at my very limited level of experience of looking at FR's that I can see a LOT of worth in seeing the results displayed in csd format.
So, they have value at least for us dummies in the field.
I must be honest though and say that the series of graphs displayed by Danny of csd's vs fr's seemed pretty convincing to me that we can, at times, glean 'extra' information form viewing the data in a different way.
Perhaps it's a little like architectural drawings, the info a builder gets from viewing the data in 'plan' can be more valuable to him than the information he gets from 'elevation', and at times vice-versa.
To complete the imperfect analogy, both plan and elevation (and of course end elevation, isometric view etc etc) are all aspects of the same measurement if you will, and all are used simply because over time they have been found to be useful!
Nonetheless, this has been a very educational thread for me, thanks. I hope it does not deteriorate because I want my education to continue.
I most certainly do NOT want to get into (what seems to be developing as) the unfortunate debate that is going on, but now after reading this thread (and the links within it) I am grateful for what I have learned and would like to say that at my very limited level of experience of looking at FR's that I can see a LOT of worth in seeing the results displayed in csd format.
So, they have value at least for us dummies in the field.
I must be honest though and say that the series of graphs displayed by Danny of csd's vs fr's seemed pretty convincing to me that we can, at times, glean 'extra' information form viewing the data in a different way.
Perhaps it's a little like architectural drawings, the info a builder gets from viewing the data in 'plan' can be more valuable to him than the information he gets from 'elevation', and at times vice-versa.
To complete the imperfect analogy, both plan and elevation (and of course end elevation, isometric view etc etc) are all aspects of the same measurement if you will, and all are used simply because over time they have been found to be useful!
Nonetheless, this has been a very educational thread for me, thanks. I hope it does not deteriorate because I want my education to continue.
You missed a bit
It's as I said. Below 1K with an FR that is limited to 300Hz, there is no way to say with any assurance exactly what the true response is below 1K. The CSD's shown are not those of the FR's shown, since the FR is shown down to 10, but the CSDs are limited to 300Hz. The FR is probably a splice, so it's a good indicator, but not reliable for any absolute analysis. The FR above the splice point and I suspect that it is, given the low end extension, is still only as precise as the sampling length will allow. This is likely still only precise (or nearly so, not necessarily absolutely) for integer multiples of the low limit, possibly 300Hz.
Likewise, the CSD is limited in that it's resolution is 300Hz. Anything between the FR points of 300, 600, 900, etc. are representative approximations. Any resonances that might actually exist between any of those points will be missed. Those particular CSDs are not fully reliable below about 1KHz because of this. Change the window type and you'll see a change in the FR and the "resonances". Some might actually "disappear". I would have thought that you'd know all of this.
I'll let Mark respond to the points that you make to his, with one exception. If you think that an impulse taken outdoors and in such a way as to lengthen a clean impulse without reflections is still only good for 2-3 msec, you do have a bit more to learn about impulse testing. I'm surprised at your comment. Remember, it's the length of the impulse used (the windowing) that determines both the low end extension and the FR resolution from that impulse. You did know this, didn't you?
Dave
It's as I said. Below 1K with an FR that is limited to 300Hz, there is no way to say with any assurance exactly what the true response is below 1K. The CSD's shown are not those of the FR's shown, since the FR is shown down to 10, but the CSDs are limited to 300Hz. The FR is probably a splice, so it's a good indicator, but not reliable for any absolute analysis. The FR above the splice point and I suspect that it is, given the low end extension, is still only as precise as the sampling length will allow. This is likely still only precise (or nearly so, not necessarily absolutely) for integer multiples of the low limit, possibly 300Hz.
Likewise, the CSD is limited in that it's resolution is 300Hz. Anything between the FR points of 300, 600, 900, etc. are representative approximations. Any resonances that might actually exist between any of those points will be missed. Those particular CSDs are not fully reliable below about 1KHz because of this. Change the window type and you'll see a change in the FR and the "resonances". Some might actually "disappear". I would have thought that you'd know all of this.
I'll let Mark respond to the points that you make to his, with one exception. If you think that an impulse taken outdoors and in such a way as to lengthen a clean impulse without reflections is still only good for 2-3 msec, you do have a bit more to learn about impulse testing. I'm surprised at your comment. Remember, it's the length of the impulse used (the windowing) that determines both the low end extension and the FR resolution from that impulse. You did know this, didn't you?
Dave
Re: You missed a bit
What? I'm going to respond.?
I doubt I will change Danny's mind. dlr's points are well taken. What good is 2-3ms at looking at the midrange. The period of a 500Hz signal is 2ms. How much decay will there be in one or 1.5 cycles...
Anyway, as I mentioned before, those of you that want a better understanding, check out the references.
dlr said:
What? I'm going to respond.?
I doubt I will change Danny's mind. dlr's points are well taken. What good is 2-3ms at looking at the midrange. The period of a 500Hz signal is 2ms. How much decay will there be in one or 1.5 cycles...
Anyway, as I mentioned before, those of you that want a better understanding, check out the references.
Certainly I do. It is my job. I have had to take many a far field measurement including those made in my anechoic chamber. The further you can be away without reflections the lower you can accurately measure. I was referring to the use of such measurements for a CSD. Seeing as how the range below 300Hz is of little to no value and the accuracy will still be limited even as you approach that. And then why try to get a clean 12ms time window to measure a CSD when the software won't show it anyway. These are ranges more dominated by room gain and room responses than anything else.
Also while accuracy is limited below 1kHz in a spectral decay is does give some approximation as to any problems. As one comes up from 400 to 600 to 800 and 1000Hz the SCD gets closer and closer to good reliable figures.
Funny! What's even funnier are those that can interpret it having not even seen it. They can just look at the frequency response and will know all about the CSD.
Zaph said:
Let me ask you Zaph, since you mention issues with some of your measurements below 800 Hz for example, would you say that your distortion measurements are reliable? Especially for the L18?
Several here are making valid points viewing these drivers as linear time invariant systems, however when one asks to compare the L18 and the P18 we have to look at the distortion performance also. Zaph you make the valid point that if notch filters are used to match the frequency response then the linear characteristics are the same. Let me point out that I think it is rare when all the resonance modes are notched, and so the FR is often more of an approximation to the target.
Let's move on to the non-linear comparision, interesting that the L18 has peaks in F3 between 2 and 3kHZ, in F5 between 1 and 2 kHZ, and more peaks between 6 and 10 kHz. Here we enter the world of non-linear analysis and where notching cannot possibly fix these distortion issues. One should also keep in mind that while these are harmonic distortion tests, they are indicative of a non-linearity, and that non-linearity will also produce intermodulation distortion.
It is important, from my view to step back and ask why a driver has various peaks and dips in the amplitude response, since if it is a perfect piston with a simple small chamber, as in a tweeter, it should follow a simple 2nd order filter function. Cone breakup, pole vent and rear chamber resonances, and reflections are most of the reasons for deviations in the FR, and often especially with cone breakup peaks are also seen in the distortion plots. The CSD tends to magnify FR issues, makes them easy to spot and also find points where there might be distortion issues. Seems the trend is that distortion is usually low, or at least well behaved when the CSD is clean. The clean CSD of the D26NC55, T25CF001, and the K1 is a quick identifier of some of the top performers. I think the CSD is helpful from this perspective.
Some might prefer the P18 from the perspective of THD performance.
Pete B.
This is the point I struggle to get my head around.... I presume this is true when looking at the CSD above the xo point (assuming we are talking about a lowpass here). However, below the xo point even if the FR curves are identical due to the implementation of identical 4th order acoustic slopes, it doesn't change the stored energy behaviour below the XO point? Unless we are saying the xo itself will act as an energy "release" (damper - excuse my struggle to find the right terms).
In other words, I need to really bend my head to understand how 2 different drivers with identical dB output at a specific frequency can end up with identical CSD information...
David.
Although I'm sorry to see where this thread seems to be heading, I have to thank Danny for resurrecting it. I've been struggling to understand how to interpret an impulse response chart, and the links posted by ucla88 were very informative.
To those who did not read the links, I found this statement particularly useful.
(credit)
Dan
To those who did not read the links, I found this statement particularly useful.
(credit)
Dan
owdi said:
Ahh, interesting! That would be caused by overlapping time windows. It increases the frequency resolution by sacrificing some of the time resolution. Alternatively, it's also possible to get sharper time resolutions at the cost of reduced FR resolution.
All in all, it makes sense that CSD plots are typically blurry, and I remember commenting in one of the other threads (it may have been the "objectives of a loudspeaker in a small room" one) that this is also the reason why human hearing cannot simultaneously be extremely accurate in both the time and frequency domains. With a typical 'tuning' threshold in the vicinity of 3Hz, this suggests that our timing accuracy must, by definition, be relatively poor.
There is good reason for longer time windows
The range below 300Hz can be useful though we're not considering it here. What's more useful and can ONLY be acquired is increasing the resolution above 300Hz. To say that a clean 12ms time window for a CSD "when the software won't show it anyway" is misinformed and highlights the issue. The resolution of the CSD is as limited by the window as is the FR. That is, if you only use 2-3msec of time to generate the CSD, you've got a very poor CSD with which to work. If the lowest frequency extracted is 300Hz, you still have little to see in the CSD for ALL frequencies between the integer multiples of that lowest frequency, 300Hz in this case. Again, 300, 600, 900, etc. Everything between these points, an area on which you commented directly, is suspect. It cannot be considered to be an accurate representation of those areas.
Now use a clean 12msec window and you'll get a much finer resolution and much more accurate representation. Now you have a resolution of about 83Hz, four times the number of reliable sample points in the frequency domain. To say the 12msec doesn't provide more useful information than 3msec is misleading at best.
A CSD is no less nor no more accurate than it is when the window used for the FR is the same, the typical scheme for showing both FR and CSD. I'm surprised again at some of your statements. A 12msec window will do wonders for a CSD just as much as it will for a FR curve.
Please, Danny, not let's not discuss who's laughing at who, not all may be in agreement. These could be informative debates if kept on a respectful level. I'll assume that you just didn't stop to think of the implication of some of your comments such as those that dismiss the benefits of a 12msec vs. 3msec window.
One thing I do know, any CSD made with a 3msec window is not going to have much accurate information below about 1KHz, whether it's the FR or the CSD. Making a judgement of a driver in that area based on such is more informative of the person making that judgement than it is of the driver.
Dave
Danny said:
The range below 300Hz can be useful though we're not considering it here. What's more useful and can ONLY be acquired is increasing the resolution above 300Hz. To say that a clean 12ms time window for a CSD "when the software won't show it anyway" is misinformed and highlights the issue. The resolution of the CSD is as limited by the window as is the FR. That is, if you only use 2-3msec of time to generate the CSD, you've got a very poor CSD with which to work. If the lowest frequency extracted is 300Hz, you still have little to see in the CSD for ALL frequencies between the integer multiples of that lowest frequency, 300Hz in this case. Again, 300, 600, 900, etc. Everything between these points, an area on which you commented directly, is suspect. It cannot be considered to be an accurate representation of those areas.
Now use a clean 12msec window and you'll get a much finer resolution and much more accurate representation. Now you have a resolution of about 83Hz, four times the number of reliable sample points in the frequency domain. To say the 12msec doesn't provide more useful information than 3msec is misleading at best.
A CSD is no less nor no more accurate than it is when the window used for the FR is the same, the typical scheme for showing both FR and CSD. I'm surprised again at some of your statements. A 12msec window will do wonders for a CSD just as much as it will for a FR curve.
Funny! What's even funnier are those that can interpret it having not even seen it. They can just look at the frequency response and will know all about the CSD.
Please, Danny, not let's not discuss who's laughing at who, not all may be in agreement. These could be informative debates if kept on a respectful level. I'll assume that you just didn't stop to think of the implication of some of your comments such as those that dismiss the benefits of a 12msec vs. 3msec window.
One thing I do know, any CSD made with a 3msec window is not going to have much accurate information below about 1KHz, whether it's the FR or the CSD. Making a judgement of a driver in that area based on such is more informative of the person making that judgement than it is of the driver.
Dave
Dave Bullet you win a Gold star. You are correct.
Here is what is funny. You said this...
But on your own site you post CSD's of everything.
http://www.speakerdesign.net/raw/rawdescr.html
So Dave, why would I want to look at a CSD with a longer time window? The longer time window allows for greater accuracy in a lower frequency range that the software crops out anyway.
One of your own measurements...
It crops below 200 for the initial response and up to 1kHz by 4ms.
Zaph's CSD's have already been posted here and show about the same thing.
Here is a CSD from the latest Clio system.
An externally hosted image should be here but it was not working when we last tested it.
It shows about the same thing as well.
You are right Dave. I agree. Accuracy is limited in the lower ranges. If the response at 300Hz is +/- 1/2 a db and 600Hz is +/- 1/4 od a db and 900Hz is +/- 1/8 of a db then clearly it lacks accuracy. However it does not hide an obvious difference with significant magnitude. This is easily seen in Zaph's measurements as differences in the 1kH range (and even lower) easily vary from driver to driver.
BTW, we see quite a bit of variance in the 1kHz to 2kHz range too from one CSD to another. These differences do not show up in a frequency response measurement.
Oh really? You'd rather look at a CSD with a 12ms time window? You don't on your own site. I use a 4ms time window to analyze a CSD just like you do.
But just for the sake of humoring you, here is the CSD of the same woofer, made from the same impulse response. One time window will be 3ms and the other 12ms.
And you said...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Oh, I am wondering all right. I am wondering what you are thinking.
All of my measurements are made with a 60ms range. I can slice up any segment of it for closer examination.
Unless looking at ranges below 1kHz, if you still have stored energy that takes longer than 3ms to dissipate from a standard 1 watt input then you have problems.
I look at a range of 25db and typically 4ms. If a driver has stored energy that last longer than that it isn't worth using.
Post #36
quote:
However, below the xo point even if the FR curves are identical due to the implementation of identical 4th order acoustic slopes, it doesn't change the stored energy behaviour below the XO point?
Dave Bullet you win a Gold star. You are correct.
Drivers are minimum phase. If their FR is identical their stored energy is identical too.
Period.
quote:
However, below the xo point even if the FR curves are identical due to the implementation of identical 4th order acoustic slopes, it doesn't change the stored energy behaviour below the XO point?
Dave Bullet you win a Gold star. You are correct.
Drivers are minimum phase. If their FR is identical their stored energy is identical too.
Period.
You don't recognize a number of things
Most of your points are irrelevant.
Two reasons. First, as zaph said, some folks want to see them. Second, and more importantly, early on I was under the impression that they were more useful than they are. I don't post them of all drivers anymore. I continued as much because I already had been doing that. I don't find them useful for the most part. Were I to start over, I probably would not post them. They are useful for the uninitiated, however.
Please tell me that you're kidding? Why would you NOT want to have measurements with more frequency resolution? Remember, we're talking time WINDOW as in the window of the impulse response in the time domain.
Have you read the page at my site the describes the measurements conditions? I hope it's just ignorance of the conditions on your part as to why mine cut off where they do.
And you find this surprising?
Do you not know why they look similar?
Oh, but they must show up in the FR if the FR and the CSD are derived from the same measurement. If you are comparing two different drivers that have the same (and they'd have to be identical) FR, then the difference is as much due to limitations in the measurement systems and/or the room conditions most likely. That's part of the problem, I can show you two CSDs from the SAME impulse response that vary signficantly. There is no perfect CSD just as there is no perfect FR. The use has to understand and know the limitations of the measuring system.
Absolutely!!!! How could you not???? Just as I can show measurements from up to 24K, I measure for the maximum window possibility, then display the useful range. The CSD is no different in this respect.
That should be apparent to someone with experience who understands the measurement system and conditions, all of which I document at my site. But it shouldn't take reading that page to recognize directly that the time window at my site is adequate due to the fact that I have to set the window stop marker so that I only get 4ms of time. I have to window out the reflections. You should have recognized that immediately.
I like what I see in the 12ms CSD. Much better frequency resolution. From 1KHz down you can now see deviations in the FR that are resonances (don't need the CSD to know that, that's always what that is). The resonance ridge in the CSD is just confirmation of what's in the FR.
I'm thinking that I really like measurements with as long a window as I can get for the best frequency resolution and low end extension. I don't know why you would not. In addition, I'm thinking that a 12ms window for the FFT can be used, then the user could, if they chose, select the display axes to adjust for different persectives. You know, like looking at only 4ms of the 12msec window, since that will show the same range as a 4ms window, but with far better frequency resolution and much better low end extension. But you don't, apparently. Your display is not argument against a 12ms window, only that the user needs to take every advantage that the software provides.
Then what's the issue?
I might agree with that in general, but not always. That's also a personal choice. The problems are going to be evident in the FR non-linearity. However, as zaph pointed out and you contradicted in error, any corrections that can be made using the crossover will mitigate the linear distortion in the area of correction. The transfer response is the transfer response, period. The non-linear distortion amplification is another issue. That's another whole discussion, however.
Dave
Most of your points are irrelevant.
Two reasons. First, as zaph said, some folks want to see them. Second, and more importantly, early on I was under the impression that they were more useful than they are. I don't post them of all drivers anymore. I continued as much because I already had been doing that. I don't find them useful for the most part. Were I to start over, I probably would not post them. They are useful for the uninitiated, however.
Please tell me that you're kidding? Why would you NOT want to have measurements with more frequency resolution? Remember, we're talking time WINDOW as in the window of the impulse response in the time domain.
One of your own measurements...
It crops below 200 for the initial response and up to 1kHz by 4ms.
Have you read the page at my site the describes the measurements conditions? I hope it's just ignorance of the conditions on your part as to why mine cut off where they do.
And you find this surprising?
Do you not know why they look similar?
Oh, but they must show up in the FR if the FR and the CSD are derived from the same measurement. If you are comparing two different drivers that have the same (and they'd have to be identical) FR, then the difference is as much due to limitations in the measurement systems and/or the room conditions most likely. That's part of the problem, I can show you two CSDs from the SAME impulse response that vary signficantly. There is no perfect CSD just as there is no perfect FR. The use has to understand and know the limitations of the measuring system.
Absolutely!!!! How could you not???? Just as I can show measurements from up to 24K, I measure for the maximum window possibility, then display the useful range. The CSD is no different in this respect.
That should be apparent to someone with experience who understands the measurement system and conditions, all of which I document at my site. But it shouldn't take reading that page to recognize directly that the time window at my site is adequate due to the fact that I have to set the window stop marker so that I only get 4ms of time. I have to window out the reflections. You should have recognized that immediately.
I like what I see in the 12ms CSD. Much better frequency resolution. From 1KHz down you can now see deviations in the FR that are resonances (don't need the CSD to know that, that's always what that is). The resonance ridge in the CSD is just confirmation of what's in the FR.
I'm thinking that I really like measurements with as long a window as I can get for the best frequency resolution and low end extension. I don't know why you would not. In addition, I'm thinking that a 12ms window for the FFT can be used, then the user could, if they chose, select the display axes to adjust for different persectives. You know, like looking at only 4ms of the 12msec window, since that will show the same range as a 4ms window, but with far better frequency resolution and much better low end extension. But you don't, apparently. Your display is not argument against a 12ms window, only that the user needs to take every advantage that the software provides.
Then what's the issue?
I might agree with that in general, but not always. That's also a personal choice. The problems are going to be evident in the FR non-linearity. However, as zaph pointed out and you contradicted in error, any corrections that can be made using the crossover will mitigate the linear distortion in the area of correction. The transfer response is the transfer response, period. The non-linear distortion amplification is another issue. That's another whole discussion, however.
Dave
on and on...
Not at all. See examples of CSD measurements that Zaph posted. All you have to do is change the moving mass and you change the amount of stored energy due to inertia.
Dave, I do use as long of a time window as possible without reflections, but I am talking about a CSD. More on this below.
No, I found it very predictable and consistent.
Certainly I did, and it confirmed my point.
But Dave, if there is a resonance at 6kHz and it dies in a couple of ms then looking at it on a 12ms scale crunches it into a small segment making it difficult to see. See the example of the one I posted in 3ms and 12ms windows.
I nice assumption on your part Dave, but those small deviations below 1kHz are likely reflections. This measurement was taken indoors in a large room.
Yea, me too. But we have been talking about reading useful information from a CSD. Do we have a difference in preference now as to how we most like to view the data? Earlier it was useless data. Now you have a preference?
Apparently you misunderstood from my previous post. I shoot a 60ms impulse response with each measurement. If I am looking at frequency response then I try to catch as long of a time window as I can without reflections. If looking at a spectral decay I might be more inclined to zoom into a shorter time window to spread a short range out over the full length of a graph to better view it and analyze it. 4ms is often good.
In error? Not so.
A crossover will "mitigate" (minimize) resonance outside its band? Minimize it, sure. Eliminate it, not so. Often I see break up in a woofers response pushed down 20 to 25db. If played at a 90db level then the break-up is only pushed down to the 65 or 70db range, not eliminated, and still audible.
The crossover also does nothing to control stored energy outside the crossover range, like in a range below the crossover point to a tweeter.
Not at all. See examples of CSD measurements that Zaph posted. All you have to do is change the moving mass and you change the amount of stored energy due to inertia.
Dave, I do use as long of a time window as possible without reflections, but I am talking about a CSD. More on this below.
No, I found it very predictable and consistent.
Certainly I did, and it confirmed my point.
But Dave, if there is a resonance at 6kHz and it dies in a couple of ms then looking at it on a 12ms scale crunches it into a small segment making it difficult to see. See the example of the one I posted in 3ms and 12ms windows.
I nice assumption on your part Dave, but those small deviations below 1kHz are likely reflections. This measurement was taken indoors in a large room.
Yea, me too. But we have been talking about reading useful information from a CSD. Do we have a difference in preference now as to how we most like to view the data? Earlier it was useless data. Now you have a preference?
Apparently you misunderstood from my previous post. I shoot a 60ms impulse response with each measurement. If I am looking at frequency response then I try to catch as long of a time window as I can without reflections. If looking at a spectral decay I might be more inclined to zoom into a shorter time window to spread a short range out over the full length of a graph to better view it and analyze it. 4ms is often good.
In error? Not so.
A crossover will "mitigate" (minimize) resonance outside its band? Minimize it, sure. Eliminate it, not so. Often I see break up in a woofers response pushed down 20 to 25db. If played at a 90db level then the break-up is only pushed down to the 65 or 70db range, not eliminated, and still audible.
The crossover also does nothing to control stored energy outside the crossover range, like in a range below the crossover point to a tweeter.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.