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Discussion Starter #1 (Edited)
Driver:
Vifa NE180W-4
Vifa NE180W-04 6-1/2" Full Range Woofer 264-1096

Manufacturer Spec Sheet:
http://www.tymphany.com/files/NE180W-04 Rev2_0.pdf


This one tested MUCH better than it's big brother. Some serious linear throw on this guy even with an offset of 2.5mm (clearly visible).


FR/HD On & Off Axis testing done at 1m to get standard 2.83v/1m SPL value.

Further FR/HD testing done at 1/2m to get 102dB HD values.

Window is 9.5ms, getting response down to about 180hz.

IMD Voice Sweep Testing done at given (in chart results).


Note: In this case, I provided a zoomed in result of the FR at 0deg @ 2.83v/1m.


On to the results...
 

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Discussion Starter #2 (Edited)
LPM (T/S):

Re 3.45 Ohm electrical voice coil resistance at DC
Le 0.090 mH frequency independent part of voice coil inductance
L2 0.629 mH para-inductance of voice coil
R2 2.33 Ohm electrical resistance due to eddy current losses
Cmes 413 μF electrical capacitance representing moving mass
Lces 33.78 mH electrical inductance representing driver compliance
Res 63.10 Ohm resistance due to mechanical losses
fs 42.6 Hz driver resonance frequency
------------------
f ct 60.0 Hz driver resonance frequency in enclosure
Mechanical
Parameters
(using test encl.)
Mms 5.929 g
mechanical mass of driver diaphragm assembly
including air load and voice coil
Mmd (Sd) 5.043 g
mechanical mass of voice coil and diaphragm without
air load
Rms 0.228 kg/s mechanical resistance of total-driver losses
Cms 2.353 mm/N mechanical compliance of driver suspension
Kms 0.43 N/mm mechanical stiffness of driver suspension
Bl 3.789 N/A force factor (Bl product)
Loss factors
Qtp 0.363 total Q-factor considering all losses
Qms 6.976
mechanical Q-factor of driver in free air considering
Rms only
Qes 0.381
electrical Q-factor of driver in free air considering Re
only
Qts 0.362 total Q-factor considering Re and Rms only

LSI:

  • X Bl @ Blmin=82%: 6.4 mm
  • X C @ Cmin=75%:5.6 mm













 

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Indeed this looks much better. Looking back over the NE testing I've seen the popular sizes , 7 and 12 are much better optimized than the rarely produced remaining sizes, at least rare from HT and car audio point of view. Maybe the 2" are not scarce in commercial uses. It may very well be the case that optimization or production standards whatever the case are costly to implement so more effort is invested in the bread and butter of the lineup.

This one has the goods to reach a 8mm xmax if well optimized. Otherwise it's still a fantastic driver from what I can tell. Another area of interest to me was cooling since the neos need a cooler climate and this one seems to have no problem keeping it's cool. The 7 and 12 versions look like a great deal for the money. Satori watch out!
 

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Third order IMD is off the charts at high output. Clearly it doesn't like that 20hz bass note.
 

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Discussion Starter #11 (Edited)
Analysis time...


T/S Parameters (highlights; see PDF for full table):

Re = 3.45 ohm
Fs = 42.6 hz
Le = 0.090mH
Bl = 3.789 N/A
Qts = 0.362

I found no resonance ripples in the impedance sweep.

Xmax and LSI:
In the LSI test, both Bl and Suspension have an offset; 1.8mm and 2.8mm, respectively. As you might have guessed, had someone held a gun to your head, the offset of suspension results in suspension being the limiting factor of xmax at 5.6mm where Bl is limited at 6.4mm. Had the driver been centered, you figure both the offsets reduced by half, and you would have had the xmax limited by Cms at 7mm.

One thing I'd like to comment on is how Bl is relatively low compared to other woofers of this size. However, it has some very nice linear throw. I often see people look at Bl as a predictor of performance and, IMO, this is a prime example why you shouldn't place all your eggs in that basket.

The Le(x) has very low overall coil in vs coil out delta; 0.06mH total between the range of xmax in/out. That's very low. I see assymetry here but the mfg info says they use a copper cop to minimize reduction, so while the assymetry hints at the non-use of a shorting ring, the cap does indeed reduce inductance to a minimal value.

Make sure to use the LPM data along with the above xmax values to model this driver for low end response.


Frequency Response:
Measured SPL with 2.83v input at 1m is approximately 86dB +/-1dB in the bandpass of 200-4khz. Above this pass band, there is a spike of 3.5dB at 4.5khz. Likely a breakup mode as it shows up somewhat in the off axis measurements as well.
There's a clear divergence in on/off axis response above about 1600hz; zoomed in the divergence occurs closer to 1400hz which correlates with the driver size reliably.
30 degrees off axis, this driver looks pretty dang good. Further than that, however, and the response past 2khz is not great. So, choose wisely. All in all, this would make a good mid-range driver coupled with a low crossed tweeter if used off-axis. On-axis (ie: the kicks or your house), you can get a bit more usable bandwidth in regards to FR.



Distortion:

Note:
As I've said in previous posts, the room modes contribute to high levels of distortion below my gating frequency (approx 150-200hz, depending on treatment used). Below this, my room takes over and colors the distortion results, so I had to gate out the low end response. However, T/S parameters and xmax measured by LSI are dominant here anyway: use these to model the low end limitations in a program such as WinISD.


Harmonic Distortion of this driver looks good. At the 1/2m mark, with a 102dB level (96dB at 1m), this driver exhibits THD under 2% down to 150hz.
While you do see a rising 2nd order HD response as you go higher in frequency, it's still trivial IMO. The 3rd order HD is like nothing I've personally seen before. It's nearly ruler flat at 0.25%. Klippel says that assymetry creates 3rd order distortion. Since this driver tested nearly perfectly symmetrically in LSI, I believe that's why we see such good 3rd order distortion.

Multitone Distortion:
This testing was done with 8v input at 1/2m. This equates to roughly 104.7dB at this distance. Or, 98.7dB at 1m. So, looking above the 150/200hz mark, the distortion stays just above -30dB up until 1khz where it drops to just below -30dB up to about 3khz. Above 3khz, the distortion quickly increases in magnitude and is reaching nearly -20dB.
Keep in mind, these values are given as (-); which is then a reference to the fundamental (0dB).

Intermodulated Distortion is new to me (us?) in my measurement suite. Klippel was kind enough to lend us this module to do further analysis so I took advantage of it. If you want to read more about it, please visit their website:
klippel.de

On their site you'll find a lot of discussion about IMD testing. Namely, to me, is the way that it brings to light issues standard HD testing does not, such as inductance. In short, inductance rears its head on the higher end of the spectrum and is more readily visible in IMD testing of 2nd order components. Drivers without shorting rings are stated to have a rising 2nd order distortion between (7-20)*fs. (Please view this chart for further information).
Chart Linked said:
Le(x) symptoms:
moderate HD in sound pressure and current for 1.5fs < f < 4fs
high IMD in sound pressure and current (f1 < fs, f2 > 7fs)
Above, in the LSI discussion, I mentioned that this driver uses copper caps to limit inductance (as per their mfg data set). This particular IMD Voice Sweep test used a fix bass tone at 20hz (fs*0.5) with a swept voice tone between approximately 160-5khz. I chose this range to emulate where most people will be using the driver in hopes that the distortion issues would be more useful to you.

From about 200-3khz 2nd order distortion is pretty low overall; staying under 20% which doesn't seem too high relative to the more problematic areas of other drivers under test. However, above this, IMD increases sharply to >60% with all the stepped voltages.

For 3rd order results, the % IMD is about 15% ]higher overall for the entire test pass band than it is for the 2nd order IMD %'s. Notably reaching 55% at 400hz (odd) with 8v input. I wonder if this has anything to do with the offset shown in LSI. Just another thing I'll have to try to dig up (or you can help me find).

As with the Dyn test, note the 2nd order component vs that of the 3rd order component, which is much more linear relative to the 2nd order component.

The fun stuff, to me, is our ability to now see how increased power (input voltage) affects the distortion values. For example, let's look at IMD 2nd order:


Note that as you increase the voltage you get increased distortion. Duh, right? Well, it's certainly nice to see it all overlayed rather than simply only having one graph at a given SPL. Now see how, with increasing frequency, you have a larger delta between distortion vs input voltage? For example, at 800hz you have about nearly no increase in distortion from 3.33v to 8.00v. Then, at 3khz you have a delta of about 5%. And at 5khz you have nearly 20% increase.


Moving down a bit, while still under the IMD results, look at the HD results graphs (the ones with stepped voltage). Look how they resemble the FR/HD test results with some variance (due to amount of points taken in test) but also look at how they change as the input voltage is increased like the IMD example discussed above. This gives you insight in to the driver design and potential trouble areas. Cool stuff!

Compression:
The compression data is given to you to understand just how power compression affects the output of a speaker and to show that it's not something to be taken lightly. The data is given in input voltage, but to make it a bit simpler, let's talk in terms of power (since power is a function of voltage/resistance). We know that doubling of power increases SPL by 3dB. Ideally, this means that as you double your power to the speaker it always increases by 3dB. However, due to thermal issues (heating of the coil) and nonlinearities (which is what the LSI focuses on) this just doesn't happen in high power situations. So, instead, as you increase the power your output doesn't increase in this linear fashion and, instead, your output may only increase a 1dB at very high power (totally hypothetical number; just go with me). This is exactly what compression is. So, how do we determine what is "high power" enough to cause compression? Well, that's where we use the new stuff that klippel has given us.

The way the data in this particular instance is provided, as I understand it, is simply a measurement of how much compression you receive at a given frequency. Everything you see is compared against the baseline (first voltage; in this case 1v). If all the lines are exactly the same, then the system increased in a logarithmic fashion as it should at a given input voltage. When the lines start to separate is where you lose output by compression. With this particular driver, rather than increasing in some logarithmic fashion, you lose about 5-6dB at the 8v input from the baseline 1v input from about 300hz to 5khz.
So, as you turn up the volume knob, you get less differential output at high volumes than you would at lower volumes in a pretty substantial way, IMO.
Severe cases of this is typically seen at low and high ends of the frequency spectrum and with higher input voltages. However, as you'll see, this driver seems to suffer less from compression on the lower end of the data presented than in the midrange.

You'll note that I have not provided low end data (< 200hz) for this particular driver. That was because with IMD, I'm not able to test below the gating frequency reliably as mentioned in the note above. However, the compression test is not affected by the room modes so I'll make it a point to go back and provide full bandwidth compression data and at higher input voltage so you can see the severity of power compression.

I encourage you to read up on this here:
Compression of fundamental components
I've tried to give my "in a nutshell" impression.


Summary:
As a midwoofer, this driver looks very good.
FR tolerance of +/-1dB isn't really that bad, IMO. Ideally it would great if it were less but low passed at about 2khz, I really like this driver. Besides, as ILD drives our ability to hear intensity differences, I have to assume that it's dominant with a single source as well (not just stereo level differences). ILD takes precedent above about 2khz (based on ear geometry) and some research has proven our ability to hear differences above this value is at best 0.5dB with a median of 2.3dB*. Given that, I'm not at all concerned about +/-1dB below this 2khz.
*http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579258/

The offsets cause the xmax to suffer by about 1.4mm; ultimately limiting the linear throw to about 5.6mm by Bl. The inductance overall is low and doesn't seem to be a problem until above about 3khz where it takes off like a rocket (assumedly linked by IMD 2nd order increase). Which, really, is fine because you probably won't be using it past this anyway in any case due to increased directivity in home use and/or car audio use where on-axis is typically not achievable all coupled with the surround mode at 4.5khz.

In terms of non-linear results, I think it's pretty darn good. Overall HD is down really low -below 2% down to 200hz - at 96dB @ 1m. As discussed, there's a clear rise in IMD above 3khz. The one thing that concerns me is the increased level of 3rd order IMD. I have this gut feeling that if the driver's suspension were centered, this level would be brought down. However, I'm not able to find anything relating offsets to any forms of distortion; namely 3rd order, so I'll just have to mark this and try to investigate some more.

All in all, not too shabby. :)



-------------------------------


That's it for me... at least for now. I hope that helps you all to understand the data a little more and helps you to draw your own conclusions about tests done in the future. I plan to provide this kind of analysis for all future tests but I ask you to provide your own as well. As a community we learn together. I'm still working to understand the data fully.

To anyone in the industry who's looking, if you want to provide advice or insight in to my test and/or driver design please feel free. This is all about learning and progressing.

- Erin
 

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Thank you for all that Erin, that is awesome. I enjoyed reeading your description and analysis.

Makes me want to get these again.
 

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Discussion Starter #13
Thanks. Like I said, I'm still learning, but hopefully the analysis will kick off further discussion and/or help others get up to speed on what I've been working toward.


What I'd REALLY like to do is get my hands on two drivers that are exactly the same. One has a shorting ring. The other does not. Then test them back to back to see what the differences are.

I also still want to play with the Simulation module where I can simulate a centered coil to see the effects.
http://www.klippel.de/uploads/media/AN21-Bl_shift.pdf
 

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This driver pair (this exact driver...) was purchased as a test speaker for trial in my dash locations. It was eliminated as a good candidate for that specific job, but I very much loved its warm, woody sound. It sounds exactly nothing like a poly or aluminum cone driver, but it doesn't sound 'warm with distortion'. Subjectively I would say that the midrange of this driver is extremely pleasant. For my installation the radiation pattern (directivity) and my ear's preference to cross this driver in the 2-2.5K range eliminated it as a good candidate for my needs, but I could easily see this driver put to extremely good use as a dedicated midrange in a 3-way home speaker. Paired with a Vifa XT tweeter and either the 10 or 12" NE driver as a dedicated woofer, these would make a wonderfully lush, detailed setup. Similarly with a close-placed tweeter in a door or kick panel this driver would really shine. I was sad that it didn't better fit my needs as I really loved the way it sounds!
 

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Look on page 36 for symptoms under the heading IMD:
http://www.klippel.de/uploads/media/Loudspeaker_Nonlinearities%E2%80%93Causes_Parameters_Symptoms_06.pdf

It appears the suspension has no impact on it.

Not sure what causes that third order IMD in this speaker but that will be the leading distortion type by far. The next biggest distortion type is MTD. HD is so low by comparison I'm not sure it even matters.

Why is everybody testing HD when these two are so high? Zaph says HD is indicative of IMD performance and maybe other nonlinear distortion types. Would you really extrapolate 30% distortion from .5% HD?

I would have expected a 7" driver like this to totally kill the 4" Dyn. in every way. Maybe there is a downside to using a really big cone or maybe using that 20hz bass tone really makes this speaker loose it's cool up top. I wonder if it would have lower distortion of all types with the fixed tone at 93hz.
End rant.
 

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Discussion Starter #16
Should have said Bl. Sorry. Actually, I addressed that same topic in my summary in the Dyn Test 2 thread.
But, see, we are learning!


I agree, seeing IMD certainly makes you wonder just how useful HD results are. I believe Geddes has all but said THD is meaningless; I don't know if he lumps all distortion types together so I wonder if he has the same thoughts on IMD results.
I, too, am curious just how the different bass tones might change the parameters. With the Dyn, 0.5*Fs was so far below any nominal passband (say, 24dB @ 200hz, you're down ~72dB at 43hz, I didn't feel it was worthwhile to fix the bass tone there as much as it would be at Fs. But, the recommendation from Klippel is 0.5*Fs so that's what I'll do from now on. No need to continue to rant about it. ;)
 

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Why are your's (and what winISD calculated) and Zaph's sensitivity numbers so different?
The reason his sensitivity is off is the mmd/mms is impossibly low, falsely giving higher sensitivity than it would otherwise. 5.9 gram mms is impossible even a very light 6.5" cone body weighs 5 grams alone and then you would need to add for spider voice coil and dust cap plus adhesives. Vifa lists it as 19.8 and 1w/1m of 88dB

You need to manually plug in the mmd for the T/s parameters to be truly useful and correct. You cannot depend on Klippel or LMS/ LEAP to get that right so you either have to depend on the Manufacturers data or cut one apart and measure.

Eric
 
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