kmaier said:
Hello Feastrexians, this is Paul Harvey. Stand by for news!
I just got some measurement data from Hal Teramoto that he asked me to look over . . . I'm not all that fluent in the T/S lingo myself but I saw one thing that looked fishy and asked him to check up on that. In any case it looks like some data should be forthcoming soon.
However, there are also going to be some significant disclaimers issued along with them, such as the fact that they represent the parameters of the drivers at a particular point in their lives and under particular conditions -- because the parameters do shift during the run-in cycle. And not only that, I suspect that if I could pick Keith Larson's brains thoroughly enough, the way of taking the measurements might change as a result of his advice and that would yield different results . . . although probably not drastically different. And of course with the field coils the voltage setting is a huge variable as far as T/S parameters go. Anyway, we can cross those bridges when we come to them, which should be soon . . .
-- Chris
cdwitmer said:
hmmm, probably a bad idea then
sounds like the reason my dad has 3 garages, which he claims are "purpose built" (do I ever wish I were kidding). he got tired of having his space invaded, and once he got the property to expand, he sort of had a midlife crisis and overdid it a bit just to "make a point". then again, the guy has probably every hand-tool known to man, and most of the power tools to go with it
I have a few ideas up my sleeve for justifying the creation of a compact Feastrex-based stereo system here at home, but I need to bide my time and play my cards carefully. After 20+ years, my wife has me all too well figured out . . .
-- Chris
I definitely wish you luck in that. Keep us updated on the compact system
-Jared
I was Mr. Teramoto’s interpreter at RMAF this year (as well as last year), and again this year we met with Keith Larson (of Smith & Larson Audio, the company that makes Woofer Tester Pro) to get a lesson in how to measure T/S data on Feastrex drivers. Unfortunately, we weren’t able to get started until late in the evening, after all the show attendees had left our room, and then we didn’t have much time to work before we all had to leave. That was unfortunate.
At any rate, the impression I left with is that this is a large, complex task for people that aren’t experienced with it. In other words, there’s a huge learning curve for beginners. Woofer Tester Pro is a very advanced, highly technical product with a tremendous amount of technical functionality, and there are also many factors that affect the results one gets, including temperature, humidity, air pressure, weight on the cone, the level of voltage supplied from the PSU (in the case of field coil drivers), age of the driver (i.e., the extent to which it’s burned in), and a number of other factors that I can’t remember now. Those of you who have experience measuring T/S data undoubtedly know the details of all this much better than I do, I’m sure.
Also, there are a lot of factors that can affect or invalidate the data from the testing. For example, the weight we placed on the cone vibrated, making the data of that test run invalid. Also, the driver itself can vibrate around on the table top. A couple other test runs were also invalidated by other things that went wrong. In addition, we were measuring a brand-new NF5ex driver, so it was far from being burned in. (Some T/S data would be very different for a burned-in driver.) As a result of all these factors, we didn’t get any useful data from this exercise.
Anyway, the point is that it’s pretty complicated and time-consuming for inexperienced/non-technical people to learn. If it was easy, then undoubtedly we’d already have plenty of T/S data by now from the number of people who have made efforts to get the data thus far.
I know, none of this is a valid excuse for not having data—I’m just mentioning this as background for those of you who might be interested in knowing why this is taking forever and a day. Most other driver manufacturers provide T/S data, so it’s obviously just a matter of allocating the resources to get it. It’s very good that Chris has conveyed the urgency of this to the people at Feastrex and that they’ve responded positively. Hopefully, the data will be forthcoming soon. (Of course, there already is data for the D5nf, and maybe for one other driver model as well, but it will be good to get data for all the drivers.)
But one more interesting point is this. Mr. Teramoto told me that he has heard two drivers with the same T/S data sound very different. I don’t know how that could be, but I believe him because he has very good ears. At any rate, T/S data for these drivers should at least work in a general sense to help steer cabinet designs in the right direction.
Mike
P.S. Mr. Teramoto sent me a file with some T/S data in it (for the D9nf, D5nf, and NF5ex drivers), and I posted it here with this message before I read Chris's email above, so it appears that I may have posted it prematurely (before Chris had a chance to review it for strange data). So, I just removed it. However, I noticed that it had already been downloaded two times before then. So, if you downloaded it, please bear in mind that it may or may not be good data. Please watch for a post from Chris about that. Sorry for the inconvenience!
At any rate, the impression I left with is that this is a large, complex task for people that aren’t experienced with it. In other words, there’s a huge learning curve for beginners. Woofer Tester Pro is a very advanced, highly technical product with a tremendous amount of technical functionality, and there are also many factors that affect the results one gets, including temperature, humidity, air pressure, weight on the cone, the level of voltage supplied from the PSU (in the case of field coil drivers), age of the driver (i.e., the extent to which it’s burned in), and a number of other factors that I can’t remember now. Those of you who have experience measuring T/S data undoubtedly know the details of all this much better than I do, I’m sure.
Also, there are a lot of factors that can affect or invalidate the data from the testing. For example, the weight we placed on the cone vibrated, making the data of that test run invalid. Also, the driver itself can vibrate around on the table top. A couple other test runs were also invalidated by other things that went wrong. In addition, we were measuring a brand-new NF5ex driver, so it was far from being burned in. (Some T/S data would be very different for a burned-in driver.) As a result of all these factors, we didn’t get any useful data from this exercise.
Anyway, the point is that it’s pretty complicated and time-consuming for inexperienced/non-technical people to learn. If it was easy, then undoubtedly we’d already have plenty of T/S data by now from the number of people who have made efforts to get the data thus far.
I know, none of this is a valid excuse for not having data—I’m just mentioning this as background for those of you who might be interested in knowing why this is taking forever and a day. Most other driver manufacturers provide T/S data, so it’s obviously just a matter of allocating the resources to get it. It’s very good that Chris has conveyed the urgency of this to the people at Feastrex and that they’ve responded positively. Hopefully, the data will be forthcoming soon. (Of course, there already is data for the D5nf, and maybe for one other driver model as well, but it will be good to get data for all the drivers.)
But one more interesting point is this. Mr. Teramoto told me that he has heard two drivers with the same T/S data sound very different. I don’t know how that could be, but I believe him because he has very good ears. At any rate, T/S data for these drivers should at least work in a general sense to help steer cabinet designs in the right direction.
Mike
P.S. Mr. Teramoto sent me a file with some T/S data in it (for the D9nf, D5nf, and NF5ex drivers), and I posted it here with this message before I read Chris's email above, so it appears that I may have posted it prematurely (before Chris had a chance to review it for strange data). So, I just removed it. However, I noticed that it had already been downloaded two times before then. So, if you downloaded it, please bear in mind that it may or may not be good data. Please watch for a post from Chris about that. Sorry for the inconvenience!
I don't think you need to worry - I tried to download it and got "invalid attachment". Although that may of course have been because you were in the process of removing it, and I wasn't one of the two.
While I'm typing this, I will say that, while providing T/S params is a good idea, I'm surprised at the storm this has raised re Feastrex drivers in particular. Surprised because it seems a truism on some other threads that the T/S data provided by some other manufacturers is utterly unreliable and false, and this is treated, if not as a joke, then simply as business as usual. I'd have thought better to provide no data than to provide misleading information.
Just my $0.02 (Canadian).
Regards.
Aengus
No, I don't see a reason for this to happen. Maybe if the drivers are identical models, with the same materials used for the cone/magnet/voicecoil. Otherwise, T/S data doesn't account for harmonic distorsions, non;linearities in the gap, and other measureable factors that have an impact to the sound.
The drivers are indeed the same models, and made of the same materials. Of course, it's impossible that two drivers could be *exactly* identical since there are always small differences in manufacturing tolerances and such, but they're as close to being identical as possible, I'd think.
So, if they're the same models, made of the same materials, and have the same T/S data, shouldn't they sound the same? (Sorry, I'm not asking this rhetorically--I really don't know the answer. I'm curious about this.)
At any rate, they do indeed sound very different in the real world. So, I'm sure there must be some logical explanation for this.
Given this, if cabinets are designed based on T/S data, and if you have two "identical" drivers that have the same T/S data but sound different, then wouldn't they still sound different in cabinets that are designed based on that T/S data?
Sorry if this is a stupid question. Please don't flame me; I don't have a background in audio technology. I'm just curious about this . . . .
Thanks,
Mike
So, if they're the same models, made of the same materials, and have the same T/S data, shouldn't they sound the same? (Sorry, I'm not asking this rhetorically--I really don't know the answer. I'm curious about this.)
At any rate, they do indeed sound very different in the real world. So, I'm sure there must be some logical explanation for this.
Given this, if cabinets are designed based on T/S data, and if you have two "identical" drivers that have the same T/S data but sound different, then wouldn't they still sound different in cabinets that are designed based on that T/S data?
Sorry if this is a stupid question. Please don't flame me; I don't have a background in audio technology. I'm just curious about this . . . .
Thanks,
Mike
Right.
I find this very difficult to believe. That's not a flame BTW Mike, only an observation I'm throwing out. Drivers of the same model should provide very similar performance, as is their duty. If they don't, then this is a matter of concern (!) and suggests that either something is out of spec., or the assessment methodology is flawed. Subtle differences, due to reasonable sample deviation, certainly. The kind of night & day differences being described here would require major deviations in construction. Measuring each driver in a consistant fashion is useful to help with QC -Lowther do it, for example, although they don't publish their results.
For the sake of argument I shall suspend my disbelief, and assume that two pairs of completely identical drivers do indeed sound completely different. Therefore yes, common sense dictates that they will continue to sound completely different irrespective of what you do with them WRT the enclosure. You could try each pair in a cabinet created utilising the T/S parameters which were derived from measurements. They will continue to sound completely different. You could then try each pair in a cabinet created using some other form of methodology. And they'll still continue to sound completely different.
Not a whole lot you can do about that. But, as I suggested, I don't buy it. Something's wrong somewhere.
BTW -remember, T/S parameters are only a series of mathematical constructs derived from measuring a driver. They don't tell you what it sounds like -that's not what they're for.
I find this very difficult to believe. That's not a flame BTW Mike, only an observation I'm throwing out. Drivers of the same model should provide very similar performance, as is their duty. If they don't, then this is a matter of concern (!) and suggests that either something is out of spec., or the assessment methodology is flawed. Subtle differences, due to reasonable sample deviation, certainly. The kind of night & day differences being described here would require major deviations in construction. Measuring each driver in a consistant fashion is useful to help with QC -Lowther do it, for example, although they don't publish their results.
For the sake of argument I shall suspend my disbelief, and assume that two pairs of completely identical drivers do indeed sound completely different. Therefore yes, common sense dictates that they will continue to sound completely different irrespective of what you do with them WRT the enclosure. You could try each pair in a cabinet created utilising the T/S parameters which were derived from measurements. They will continue to sound completely different. You could then try each pair in a cabinet created using some other form of methodology. And they'll still continue to sound completely different.
Not a whole lot you can do about that. But, as I suggested, I don't buy it. Something's wrong somewhere.
BTW -remember, T/S parameters are only a series of mathematical constructs derived from measuring a driver. They don't tell you what it sounds like -that's not what they're for.
I think Mike must have misunderstood what Mr. Teramoto was saying . . . he surely couldn't have been saying that two Feastrex drivers of the exact same model are going to sound different from each other in an "apples vs. apples" comparison. That would be ridiculous indeed.
On the other hand, if we are talking about field coil versus permanent magnet drivers, or two field coil drivers with different kinds of motors, it might be possible to have them appear in a particular set of tests to have similar parameters, and yet to have noticeably different sounds in actual use. That's because the tested parameters are providing "snapshots" of the how the drivers behave under a specific set of signal input conditions, but it does not follow from that that the behavior of the respective motors will continue to be consistently similar under actual usage conditions.
Among permanent magnet drivers, Feastrex only uses Alnico, but there are plenty of manufacturers that have used Alnico, ferrite and rare earth magnets in different versions of the same basic driver, and by design have given them pretty similar T/S parameters, yet I doubt anyone would argue that those different variants all sound exactly the same.
But two drivers of the same model with the same parameters sounding noticeably different when used under identical conditions? That would be a sure sign that it's time to go into retirement as a driver manufacturer.
-- Chris
On the other hand, if we are talking about field coil versus permanent magnet drivers, or two field coil drivers with different kinds of motors, it might be possible to have them appear in a particular set of tests to have similar parameters, and yet to have noticeably different sounds in actual use. That's because the tested parameters are providing "snapshots" of the how the drivers behave under a specific set of signal input conditions, but it does not follow from that that the behavior of the respective motors will continue to be consistently similar under actual usage conditions.
Among permanent magnet drivers, Feastrex only uses Alnico, but there are plenty of manufacturers that have used Alnico, ferrite and rare earth magnets in different versions of the same basic driver, and by design have given them pretty similar T/S parameters, yet I doubt anyone would argue that those different variants all sound exactly the same.
But two drivers of the same model with the same parameters sounding noticeably different when used under identical conditions? That would be a sure sign that it's time to go into retirement as a driver manufacturer.
-- Chris
anubisgrau said:
If it has an impedance peak at Fs (it does), they can be accurately measured same as any point source driver. The problem seems to be in the language barrier combined with the steep learning curve of the 'pro' version of the woofer tester.
mluckow said:
Not normally since T/S only defines the specs for loading the driver's BW below its mass corner, i.e. 2*Fs/Qts. From this we see that normally even the most powerful motored LF/mid-bass drivers will be in their ~flat (mass controlled) pass-band by the time it's reproducing frequencies in our acute hearing BW, so all the T/S specs are telling us is that for identical spec'd drivers their mass, compliance and relative motor strength are identical, which contrary to popular belief tells us virtually nothing about the driver's HF response where we can discern subtle variances in individual drivers.
GM
No violin manufacturer on the planet is going to be able to produce two violins that sound exactly alike, and in many cases there will be signifcant differences between two violins of the same model, even if they are made by the same individual or team of builders using wood that came from identical trees. Now there is probably a bit of that in Feastrex drivers as well, since handmade paper and leather surrounds are being used. However, Mr. Teramoto has told me -- and I am prepared to believe, given the dedication of top-ranked Japanese artisans -- that Feastrex's paper maker is able to maintain consistency within 5% for his paper. Add to that the fact that paper and leather are purchased in lots that last Feastrex for a while, and I think variances in the biggest variables ought to be fairly well minimized. (And then Mr. Teramoto will adhere to the same procedures for building each of his drivers, unless he is purposefully trying to change something.) I suppose that there might be slight discrepancies in the way two drivers run in, so sure, there could well be some differences creeping in . . . but I think the key operative word here, as GM said, would be subtle . . . and since T/S parameters are primarily of concern with regard to the driver behavior in the low frequency region, whatever Mr. Teramoto might have said to Mike in this context might be irrelevant anyway . . .
-- Chris
P.S. To the extent than any of the above-referenced subtle discrepancies might be problematic, the "solution" would be to go to entirely man-made materials . . . any takers for a plastic violin?
-- Chris
P.S. To the extent than any of the above-referenced subtle discrepancies might be problematic, the "solution" would be to go to entirely man-made materials . . . any takers for a plastic violin?
Hopefully, at this price level each shipment is 'voiced' for minimal tonal variances, though complete matching isn't realistic. Even 'cookie cutter' high volume manufacturers that design them with minimal component tolerances can still be +/- 5% last time I had access to such information due to the fact that a certain amount of human error creeps in during assembly.
Anyway, consider the early handcrafted cars of Ferrari, Bugatti, et al...... if you looked at them from directly the front or rear it wasn't uncommon for them to not quite match from side to side, so I can't expect hand built drivers to be sonically perfect either.
GM
Anyway, consider the early handcrafted cars of Ferrari, Bugatti, et al...... if you looked at them from directly the front or rear it wasn't uncommon for them to not quite match from side to side, so I can't expect hand built drivers to be sonically perfect either.
GM
GM said:
They are definitely matched in pairs . . . in fact Mr. Teramoto does not want to recone just one driver in the event reconing is needed for some reason . . . he'll want to work on that pair of drivers as a pair, even if there is nothing wrong with the one.
Comparison to Ferrari is scary . . . my next door neighbor works on expensive sports cars for a living and that manufacturer's cars seem to spend as much time in the shop as they spend stuck in heavy Tokyo traffic . . .
-- Chris
anubisgrau said:
It is not "normal," and as far as I can tell, or have been able to learn from existing users, it is not even "abnormal." It simply "isn't." But, as I said above, if anyone is worried that a pair of drivers handmade from natural materials might have some variations between the two drivers, the solution is to stay away from Feastrex and go out get a pair of drivers that can be mass-produced from all man-made materials. I'm sure that under such circumstances near-miraculous levels of consistency can be achieved from one driver to the next.
-- Chris
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