I had a thread going a few years back regarding a pair of Faital 6FE100 and the parameters I measured versus the specification sheet. Long story short, they never broke-in further than what I last posted in the thread. I'll be raising similar issues here.
I now have a new pair of Fane Studio 5FRK. Using REW, I measured Fs and the Q-parameters out of the box; Fs came up high and the Q`s close enough. I then played 20Hz-50Hz sine waves at 1.4V for 48h to loosen-up the spider. Upon measuring, Fs had gone down a bit, while still higher than spec sheet and the Q-parameters had gone down a bit too.
I then built a box to measure compliance, as I believe I can achieve more precise results this way, not having a sub-gram scale. I have also previously had issues attaching the mass to the cone, which introduced resonances, errors and confusion on my part. 🙂 I have included the cubic box volume, driver cutout volume and measured the cone volume with sugar poured over cling-film. While this will depress the cone slightly, the 82cc I measured would result in a maximum error of ~3% if entirely ignored, over the ~2500cc total volume, so the actual error is likely well below 1%. I also used a sheet of thin craft foam to make a gasket for mounting and sealing. Fs was shifted-up significantly - I don't have the curve with me now, but it was well above 100Hz, possibly in the 120Hz-range if I had to guess.
From the specification sheet:
My measured parameters:
Fs is still higher than the spec sheet. I don't know if I can expect this to go down much more. Directly affected by Cms, which I will mention below.
The Q-parameters are close enough for me. It actually seems rare to have them be lower than published.
Cms, as a 'core' parameter is more telling of other deviations. Here it is pretty much half of what the spec sheet says. It also has the obvious effect of halving Vas. Can I expect Cms to go up with more spider exercise? I`d say not much more if going by my Faital 6FE100 experience. My low-level measurement signal should also produce just about the highest value on the Cms(x) curve too.
What bugs me more is Bl and Mms. Should these not be more closely controlled values? I don't think I messed up (significantly) in my measurement technique as to produce the large deviations seen above. For the compliance calculation REW asks for the voice-coil DCR, which I measured at 7.7 ohm. - my DMM displaying 0.0 ohm when touching the probes. What is going on with these two then? In what way could I have messed-up enough to get these results? If not me, what reasonable explanation is there?
While I do plan on a build with these drivers, the above questioning isn't so much in the context of design as general driver electro-mechanical behaviour and break-in. Ultimately, all I have to do is use the drivers, measure again and in the end, I have what I have and will have to work with this, which I'm entirely OK with. T/S parameters are far from the only consideration.
I now have a new pair of Fane Studio 5FRK. Using REW, I measured Fs and the Q-parameters out of the box; Fs came up high and the Q`s close enough. I then played 20Hz-50Hz sine waves at 1.4V for 48h to loosen-up the spider. Upon measuring, Fs had gone down a bit, while still higher than spec sheet and the Q-parameters had gone down a bit too.
I then built a box to measure compliance, as I believe I can achieve more precise results this way, not having a sub-gram scale. I have also previously had issues attaching the mass to the cone, which introduced resonances, errors and confusion on my part. 🙂 I have included the cubic box volume, driver cutout volume and measured the cone volume with sugar poured over cling-film. While this will depress the cone slightly, the 82cc I measured would result in a maximum error of ~3% if entirely ignored, over the ~2500cc total volume, so the actual error is likely well below 1%. I also used a sheet of thin craft foam to make a gasket for mounting and sealing. Fs was shifted-up significantly - I don't have the curve with me now, but it was well above 100Hz, possibly in the 120Hz-range if I had to guess.
From the specification sheet:
My measured parameters:
Fs is still higher than the spec sheet. I don't know if I can expect this to go down much more. Directly affected by Cms, which I will mention below.
The Q-parameters are close enough for me. It actually seems rare to have them be lower than published.
Cms, as a 'core' parameter is more telling of other deviations. Here it is pretty much half of what the spec sheet says. It also has the obvious effect of halving Vas. Can I expect Cms to go up with more spider exercise? I`d say not much more if going by my Faital 6FE100 experience. My low-level measurement signal should also produce just about the highest value on the Cms(x) curve too.
What bugs me more is Bl and Mms. Should these not be more closely controlled values? I don't think I messed up (significantly) in my measurement technique as to produce the large deviations seen above. For the compliance calculation REW asks for the voice-coil DCR, which I measured at 7.7 ohm. - my DMM displaying 0.0 ohm when touching the probes. What is going on with these two then? In what way could I have messed-up enough to get these results? If not me, what reasonable explanation is there?
While I do plan on a build with these drivers, the above questioning isn't so much in the context of design as general driver electro-mechanical behaviour and break-in. Ultimately, all I have to do is use the drivers, measure again and in the end, I have what I have and will have to work with this, which I'm entirely OK with. T/S parameters are far from the only consideration.
A: Published specs are advertising. Good enough for purchase decision, not for design.
B: Yes, drivers do need break-in. Some very little, some quite a lot.
C: Manufacturing tolerances. 10% would be considered good.
D: Calibration. Yours and theirs.
E; Environment. Air density, temperature.
F: VAS measurement technique. I do both sealed box and delta mass. Both can have large variances. When the match, I know I have done it correctly. Wrong mass is a common mistake.
What else do you need to know?
B: Yes, drivers do need break-in. Some very little, some quite a lot.
C: Manufacturing tolerances. 10% would be considered good.
D: Calibration. Yours and theirs.
E; Environment. Air density, temperature.
F: VAS measurement technique. I do both sealed box and delta mass. Both can have large variances. When the match, I know I have done it correctly. Wrong mass is a common mistake.
What else do you need to know?
A-B-C: I concur.
D: Manufacturer's calibration should be assumed to be best. I'd expect mine to be "good enough" in REW and my jig.
E: 250m above sea level and typical domestic environment: ~21°C and low-middling humidity ~30-40%, 101.1kPa, just to say I don't live in a desert, jungle or on top of a mountain.
F: I've had "wrong mass" happen before, caught the error and seemingly corrected it - does it seem to you I did sealed box well enough? I could find a way to have some Blu-Tak weighed precisely for me and try added mass.
What else: Bl and Mms (Mmd) are the sticking points for me. I've gotten wrong Mms with incorrect added mass method before, so am wary of any mistakes I could have done with sealed box.
D: Manufacturer's calibration should be assumed to be best. I'd expect mine to be "good enough" in REW and my jig.
E: 250m above sea level and typical domestic environment: ~21°C and low-middling humidity ~30-40%, 101.1kPa, just to say I don't live in a desert, jungle or on top of a mountain.
F: I've had "wrong mass" happen before, caught the error and seemingly corrected it - does it seem to you I did sealed box well enough? I could find a way to have some Blu-Tak weighed precisely for me and try added mass.
What else: Bl and Mms (Mmd) are the sticking points for me. I've gotten wrong Mms with incorrect added mass method before, so am wary of any mistakes I could have done with sealed box.
I do my test with WooferTester. The earlier version of DATs. Nickels are 5 grams,
I do both sealed and mass. When the are close, I have confidence they are correct.
Usually, not that far from factory numbers. Of course, I prefer low Q sealed boxes and I tune them by Qtc, so I only need to be as close as horseshoes and handgernades. Do NOT assume factory numbers are correct. You can usually trust the likes of SEAS, ScanSpeak , SB and the like, but the rest may be more marketing. Just be aware.
I do both sealed and mass. When the are close, I have confidence they are correct.
Usually, not that far from factory numbers. Of course, I prefer low Q sealed boxes and I tune them by Qtc, so I only need to be as close as horseshoes and handgernades. Do NOT assume factory numbers are correct. You can usually trust the likes of SEAS, ScanSpeak , SB and the like, but the rest may be more marketing. Just be aware.
How do you attach your nickels and is it light enough to ignore the extra mass?
As a home hobbyist I haven't sampled nearly enough drivers to know who's more or less reliable in this regard. The closest I've measured are Fostex FF85WK, though I've had discrepancies from other Fostex units. The Faital 6FE100 from my linked thread differed greatly, in fact invalidating my original design idea. Old Philips AD9710 I picked up in crappy homemade enclosures measured very close to what other hobbyists publlished on line, including Troels.
As it stands, the Fane Studio 5FRK is still usable for what I had in mind, but I kept my options open to a certain extent, so all is mostly good.
As a home hobbyist I haven't sampled nearly enough drivers to know who's more or less reliable in this regard. The closest I've measured are Fostex FF85WK, though I've had discrepancies from other Fostex units. The Faital 6FE100 from my linked thread differed greatly, in fact invalidating my original design idea. Old Philips AD9710 I picked up in crappy homemade enclosures measured very close to what other hobbyists publlished on line, including Troels.
As it stands, the Fane Studio 5FRK is still usable for what I had in mind, but I kept my options open to a certain extent, so all is mostly good.
You may find that, after a lot of "breaking-in", the fs ends up actually lower than specified - after all, compliance is much lower than spec, but moving mass is considerably higher, and that won't be subject to change...
Mms itself won't change indeed, unless I find I've measured compliance incorrectly. 🙂 I think I can have some Blu-Tak weighed at least to a tenth of a gram at a jeweller's, so I'll see what the added mass method yields.
So I swung by a jewellery store and they weighed a small amount of Blu-Tak for me, at 9.1g. I re-measured free-air and with added mass.
Previous data set, sealed box method:
Added mass method:
The added-mass measurement is closer to the spec sheet. Is there a reason I should be more confident with one or parameter set over the other? Getting closer to Mms and Bl - specs I can only derive while the manufacturer can directly measure - has me leaning towards the added mass parameter set.
What could explain the difference? Easy answer is I errred, but I'd like to know where if it is the case. Like I said earlier, I haven't bought, measured and used countless drivers such that'd I developed a 'feel' for such things.
I did not mention it yet, but I only posted the data for one of two drivers, the second follows closely enough in spec and behaviour.
Previous data set, sealed box method:
Added mass method:
The added-mass measurement is closer to the spec sheet. Is there a reason I should be more confident with one or parameter set over the other? Getting closer to Mms and Bl - specs I can only derive while the manufacturer can directly measure - has me leaning towards the added mass parameter set.
What could explain the difference? Easy answer is I errred, but I'd like to know where if it is the case. Like I said earlier, I haven't bought, measured and used countless drivers such that'd I developed a 'feel' for such things.
I did not mention it yet, but I only posted the data for one of two drivers, the second follows closely enough in spec and behaviour.
I guess I'd re-try your initial measurement (test-box style) and vary some of the starting info you told it (test vol? Sd?) and see if that pushed your results in the right direction. Your box might leak? I've tested speakers that are inherently leaky - either through the dustcap or through a thin foam surround.
I have used a DATS WT3 for a long time, I use added-mass. For a scale I've got an AWS ACPro-200, it's got 200g capacity and 0.01g resolution. As I google it currently, they seem to go for $15-20. Perhaps something like this is in your future...
I have used a DATS WT3 for a long time, I use added-mass. For a scale I've got an AWS ACPro-200, it's got 200g capacity and 0.01g resolution. As I google it currently, they seem to go for $15-20. Perhaps something like this is in your future...
The Studio 5FRK has a woven Kevlar cone. I can see light through the weaving, I don't know if it is sealed with something translucent or nothing at all.
Yeah, a little precision scale could be nice. Certainlly more convenient than building boxes to accommodate different size drivers.
Yeah, a little precision scale could be nice. Certainlly more convenient than building boxes to accommodate different size drivers.
If you can fit your mouth / lips to seal against the cone, try to blow through it. Don't let anyone see you though... that sort of thing can be embarrassing to explain... 😉
I have typically found that the factory measures of any of the drvers i have used is a better base than any of the measured data i have (1000s of drivers).
Keep in mind that T/S are not scalars althou those are the “numbers” we used. At some specific point the curves are collaped to scalars. The T/S measuring tools we use do not typically collapse in the same place so numbers are different.
Except in cases where i have no data, i only use measurements (they have to be all from the same session) to match drivers.
dave
Keep in mind that T/S are not scalars althou those are the “numbers” we used. At some specific point the curves are collaped to scalars. The T/S measuring tools we use do not typically collapse in the same place so numbers are different.
Except in cases where i have no data, i only use measurements (they have to be all from the same session) to match drivers.
dave
I don't know the optimum mass to add, but in the past I've used a ring of solder, plumbing solder for a big woofer, held at the perimeter of the dust cap with Bluetac. I prefer the sealed method and always had very good agreement with factory numbers from the better makers. Low cost import stuff, not so much.
I have used factory data in a few builds, successfully, where nothing prompted me to go back and measure. IOW it sounded OK and the response measured fine in the T/S dominated region.
I think adding mass in the vicinity of Mms should lower Fs enough in most cases.
The instructions for WooferTester or DATS tell you how much mass to add. I would assume Limp, Arta, whatever would have guidelines in their instructions. There is a range of Fs delta that works. I think D'Apolitto mentioned this in Measuring Loudspeakers. Of course, his is the old "fun" way we used to do it. Signal generator, voltmeters. graph paper. My box is in the shop so I can't pull it up to quote the specs.
There are similar guidelines for the size of the box. I had a large box with a removeable baffle and then added chunks of 4 x 4 to reduce the volume by a known amount. Pitched all of that when I moved. A test box has to be VERY rigid and it is preferable not to have any parallel walls. There has actually been some trade papers on this recently. A bad box can cause glitches in the impedance curve.
If you happen to have a small scale, as some have for various herbal consumables, you can measure out modeling clay or blue-tac. I use nickels.
There are similar guidelines for the size of the box. I had a large box with a removeable baffle and then added chunks of 4 x 4 to reduce the volume by a known amount. Pitched all of that when I moved. A test box has to be VERY rigid and it is preferable not to have any parallel walls. There has actually been some trade papers on this recently. A bad box can cause glitches in the impedance curve.
If you happen to have a small scale, as some have for various herbal consumables, you can measure out modeling clay or blue-tac. I use nickels.
WooferTester2 from Smith+Larson is probably the best T.S measure tool for diyers. It actomates the same process as when i did it manually.
The WT3 from PE (name changed to DATS), based on what the author says, guesses the T/S from the impedance curve. This is not as accurate.
dave
The WT3 from PE (name changed to DATS), based on what the author says, guesses the T/S from the impedance curve. This is not as accurate.
dave