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Old 19th October 2008, 08:05 PM   #1271
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Right.

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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.
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.

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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?
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.
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Old 19th October 2008, 08:09 PM   #1272
Aengus is offline Aengus  Canada
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Mike said:

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Mr. Teramoto told me that he has heard two drivers with the same T/S data sound very different. I donít know how that could be, but I believe him because he has very good ears.
Nothing there about them being otherwise exactly similar - just that they had the same T/S specs.

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Old 19th October 2008, 08:14 PM   #1273
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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
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Old 19th October 2008, 08:17 PM   #1274
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Quote:
Originally posted by anubisgrau
would be interesting to hear why measuring a feastrex T/S data differs from any other driver on earth?
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.


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Originally posted by mluckow

Right, but shouldn't two drivers with the same T/S data theoretically sound the same as each other (assuming they're played in the same conditions)?
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
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Old 19th October 2008, 09:32 PM   #1275
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Quote:
Originally posted by GM


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

Ah, that's interesting. Maybe it's those subtle variances that Mr. Teramoto was referring to. I doubt I'd be able to hear those variances myself, but maybe they're obvious to an experienced person with very good listening skills . . . .

Mike
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Old 19th October 2008, 10:27 PM   #1276
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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?
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Old 19th October 2008, 10:47 PM   #1277
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since english is not my native language i'm not sure if i understand you correctly, but if i do, that must be great news for someone paying 3-10k$ that 2 drivers will actually sound different from each other and that is normal?!
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Old 19th October 2008, 11:02 PM   #1278
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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
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Old 19th October 2008, 11:21 PM   #1279
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Quote:
Originally posted by GM
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
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
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Old 19th October 2008, 11:28 PM   #1280
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Quote:
Originally posted by anubisgrau
since english is not my native language i'm not sure if i understand you correctly, but if i do, that must be great news for someone paying 3-10k$ that 2 drivers will actually sound different from each other and that is normal?!
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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