JL Audio ZR800-CW 8″ Midbass


Up for test is JL Audio’s ZR800-CW 8″ Midbass.  Specs can be found here.

IMG_2243 IMG_2245 IMG_2250 IMG_2248 IMG_2247

 

Small Signal Parameters

Results as measured via Dayton’s DATs measurement tool.  Which is a very little handy tool to have.  😉

  • f(s)= 56.52 Hz
  • R(e)= 5.35 Ohms
  • Z(max)= 54.75 Ohms
  • Q(ms)= 11.113
  • Q(es)= 1.205
  • Q(ts)= 1.087
  • V(as)= 14.310 liters (0.505 cubic feet)
  • L(e)= 0.90 mH
  • n(0)= 0.20 %
  • SPL= 85.21 1W/1m
  • M(ms)= 31.46 grams
  • C(ms)= 0.25 mm/N
  • BL= 7.05

zr800 impedance

 

Frequency Response

Frequency Response and the following Harmonic Distortion measurements were taken using Dayton’s OmniMic measurement system.

The frequency response measurements below are on-axis (0 degrees) and off-axis (15, 30, 60 degrees), measured at 2.83v/1m.

zr800 fr 0 15 30 60

 

Harmonic Distortion

The following HD graphs are done in the nearfield, emulating the following SPL levels at 1 meter: 90dB, 96dB, and 102dB in order.

zr800 hd 90 zr800 hd 96 zr800 hd 102

 

 

Thoughts

Frequency Response:  Average sensitivity in it’s primary range is approximately 86dB @ 2.83v/1m.  On the low end, the Qts indicates a high value of 1.087 and a Vas of approximately 0.50 cubic feet, which means this driver is likely built for an infinite baffle type install.  According to JL’s literature, that’s indeed the case: “The ZR800-CW is a supremely powerful, dedicated mid-bass driver designed for infinite-baffle or door-mounted custom installations.”  This driver exhibits fairly linear response up until about 500hz where some issues occur.  Looking at the impedance graph you can see a resonance show up in the 600-700hz region.  This shows up in the FR with the strong dip just around 700hz.  From 700-1200hz there’s odd behavior, and above 1200hz the response gets better.

Harmonic Distortion:  I’ve provided HD measurements at (3) different SPL levels: 90, 96, and 102dB.  The reason I do this is to see the general trend of how distortion increases with output.  But since this is a midbass and likely will be pushed hard, I’ll evaluate the 102dB level distortion.  The 3% THD mark is hit at just under 40hz.  From 60-300hz, where these are most likely to be used, the distortion level is approximately 0.60%.  At 500hz the THD reaches 1% and rides that range until it begins to fall at ~1200hz.

Bottom line: As a dedicated midbass in a 3-way type system (or a 2-way using a ‘wideband’ driver) this is an excellent choice.  From the data, it is seen you can reach pretty hefty levels with very little distortion (less than 1% THD) crossing this driver between 50/60hz to about 300/400hz.  This coincides with the FR data as well.  I wouldn’t recommend crossing this higher than 500hz, though because the response gets pretty rough above this point and it would be hard to implement a crossover here.  Regarding the low end output, keep in mind cabin gain comes in to play in most cars at about the 60-70hz region and increases the SPL below this point by ~12dB/octave.  Which means some people may be able to run these without a dedicated subwoofer and be plenty happy … obviously this is very much user dependent, but I will say I’ve done it a few times myself and have had good success using a 50hz/LR2 crossover but I miss my subs too much to not use them.  😉

PS:  If you would like to help me keep up funds for testing, there’s a little ‘contribute’ button that goes through Paypal all the way at the bottom of every page.  Any little bit helps.

SB Acoustics 17NRXC35-4


Up for test is SB Acoustics’ 17NRXC35-4 6″ Woofer.

16dad960 cd3fb7dc

 Small Signal Testing:

The following results were obtained via Smith & Larson’s Woofer Tester 2.

SB-A17NRXC35-4Impedance

Large Signal LSI Klippel Testing:

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 4.4 mm Displacement limit due to force factor variation
X C @ C min=75% 1.9 mm Displacement limit due to compliance variation
X L @ Z max=10 % >4.5 mm Displacement limit due to inductance variation
X d @ d2=10% 26.2 mm Displacement limit due to IM distortion (Doppler)

img_BlX-2 img_CmsX-2 img_KmsSymmetryRange img_LX-2

ScanSpeak Revelator 26W/8867T


Up for test, is the ScanSpeak Revelator 26W/8867T Aluminum Cone 10″ Woofer.

IMG_8818 IMG_8819

Small Signal Analysis

Electrical Parameters
Re 6.08 Ohm electrical voice coil resistance at DC
Le 0.296 mH frequency independent part of voice coil inductance
L2 0.299 mH para-inductance of voice coil
R2 2.88 Ohm electrical resistance due to eddy current losses
Cmes 533 µF electrical capacitance representing moving mass
Lces 55.99 mH electrical inductance representing driver compliance
Res 91.54 Ohm resistance due to mechanical losses
fs 29.1 Hz driver resonance frequency
——————
fm 23.6 Hz resonance frequency of driver with additional mass
Mechanical Parameters
(using add. mass)
Mms 52.776 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 46.307 g mechanical mass of voice coil and diaphragm without air load
Rms 1.081 kg/s mechanical resistance of  total-driver losses
Cms 0.566 mm/N mechanical compliance of driver suspension
Kms 1.77 N/mm mechanical stiffness of driver suspension
Bl 9.949 N/A force factor (Bl product)
Loss factors
Qtp 0.556 total Q-factor considering all losses
Qms 8.934 mechanical Q-factor of driver in free air considering Rms only
Qes 0.593 electrical Q-factor of driver in free air considering Re only
Qts 0.556 total Q-factor considering Re and Rms only
Other Parameters
Vas 81.9789 l equivalent air volume of suspension
n0 0.328 % reference efficiency (2 pi-radiation using Re)
Lm 87.36 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 88.56 dB nominal sensitivity (SPL at 1m for 1W @ Zn)

ScanSpeak Revelator 26W8867T impedance

Large Signal Analysis

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 9.8 mm Displacement limit due to force factor variation
X C @ C min=75% 11.7 mm Displacement limit due to compliance variation
X L @ Z max=10 % >12.8 mm Displacement limit due to inductance variation
X d @ d2=10% 42.1 mm Displacement limit due to IM distortion (Doppler)

Force factor Bl (X) Bl Symmetry Range Mechanical compliance Cms (X) Stiffness of suspension Kms (X) Kms Symmetry Range Electrical inductance L(X, I=0) Inductance over current L(X=0, I) Total loss factor Qts (X) Resonance frequency fs (X) Mechanical loss factor Qms (X) Electrical loss factor Qes (X)

Scanspeak 22W/8534G00 Discovery 8″ Woofer


Below are the test results from the Scanspeak 22W/8534G00 Discovery 8″ Woofer.

I purchased two drivers and tested both in the small signal suite.  I only tested one driver for large signal results.

 

IMG_8774 IMG_8775

 

 

Small Signal Results:

Driver 1 Driver 2
Electrical Parameters
Re 5.94 5.95 Ohm electrical voice coil resistance at DC
Le 0.33 0.322 mH frequency independent part of voice coil inductance
L2 0.631 0.71 mH para-inductance of voice coil
R2 2.39 2.52 Ohm electrical resistance due to eddy current losses
Cmes 400 380 µF electrical capacitance representing moving mass
Lces 54.65 46.74 mH electrical inductance representing driver compliance
Res 37 32.27 Ohm resistance due to mechanical losses
fs 34 37.8 Hz driver resonance frequency
——————
fm 27.9 31.1 Hz resonance frequency of driver with additional mass
Mechanical Parameters
(using add. mass)
Mms 27.015 26.544 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 22.944 22.473 g mechanical mass of voice coil and diaphragm without air load
Rms 1.823 2.166 kg/s mechanical resistance of  total-driver losses
Cms 0.81 0.669 mm/N mechanical compliance of driver suspension
Kms 1.23 1.5 N/mm mechanical stiffness of driver suspension
Bl 8.213 8.36 N/A force factor (Bl product)
Loss factors
Qtp 0.439 0.454 total Q-factor considering all losses
Qms 3.167 2.909 mechanical Q-factor of driver in free air considering Rms only
Qes 0.509 0.537 electrical Q-factor of driver in free air considering Re only
Qts 0.438 0.453 total Q-factor considering Re and Rms only
Other Parameters
Vas 63.3215 52.2728 l equivalent air volume of suspension
n0 0.471 0.505 % reference efficiency (2 pi-radiation using Re)
Lm 88.93 89.23 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 90.22 90.52 dB nominal sensitivity (SPL at 1m for 1W @ Zn)

Discovery 22w_8534g00 imp

 

Large Signal Results:

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 4.4 mm Displacement limit due to force factor variation
X C @ C min=75% 4.7 mm Displacement limit due to compliance variation
X L @ Z max=10 % >6.0 mm Displacement limit due to inductance variation
X d @ d2=10% 29 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak -17.67 % Stiffness asymmetry Ak(Xpeak)
Xsym 0.8 mm Symmetry point of Bl(x) at maximal excursion

Discovery 22w_8534g00 bl Discovery 22w_8534g00 bl symmetry Discovery 22w_8534g00 cms Discovery 22w_8534g00 kms Discovery 22w_8534g00 kms symmetry Discovery 22w_8534g00 lx Discovery 22w_8534g00 li

ScanSpeak Revelator 22W/8857T-00 8″ Woofer, Aluminum Cone


Up for test is the ScanSpeak 22w Aluminum Cone, 8″ woofer.

I purchased two drivers and tested both in the small signal suite.  I only tested one driver for large signal results.

 

IMG_8765

IMG_8770 IMG_8772

 

Small Signal Testing:

Driver 1 Driver 2 Units
Electrical Parameters
Re 6.34 6.21 Ohm electrical voice coil resistance at DC
Le 0.264 0.251 mH frequency independent part of voice coil inductance
L2 0.546 0.46 mH para-inductance of voice coil
R2 1.56 1.57 Ohm electrical resistance due to eddy current losses
Cmes 442 450 µF electrical capacitance representing moving mass
Lces 53.61 54.35 mH electrical inductance representing driver compliance
Res 97.95 80.22 Ohm resistance due to mechanical losses
fs 32.7 32.2 Hz driver resonance frequency
——————
fm 23.2 28.3 Hz resonance frequency of driver with additional mass
Mechanical Parameters
(using add. mass)
Mms 34.936 30.36 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 31.249 26.673 g mechanical mass of voice coil and diaphragm without air load
Rms 0.806 0.842 kg/s mechanical resistance of  total-driver losses
Cms 0.679 0.805 mm/N mechanical compliance of driver suspension
Kms 1.47 1.24 N/mm mechanical stiffness of driver suspension
Bl 8.886 8.218 N/A force factor (Bl product)
Loss factors
Qtp 0.541 0.524 total Q-factor considering all losses
Qms 8.898 7.296 mechanical Q-factor of driver in free air considering Rms only
Qes 0.576 0.564 electrical Q-factor of driver in free air considering Re only
Qts 0.541 0.524 total Q-factor considering Re and Rms only
Other Parameters
Vas 46.5122 55.1206 l equivalent air volume of suspension
n0 0.271 0.313 % reference efficiency (2 pi-radiation using Re)
Lm 86.53 87.16 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 87.54 88.26 dB nominal sensitivity (SPL at 1m for 1W @ Zn)

22W_8857T impedance

 

Large Signal Testing:

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 9.1 mm Displacement limit due to force factor variation
X C @ C min=75% 10.4 mm Displacement limit due to compliance variation
X L @ Z max=10 % >11.8 mm Displacement limit due to inductance variation
X d @ d2=10% 38 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak 9.75 % Stiffness asymmetry Ak(Xpeak)
Xsym -0.09 mm Symmetry point of Bl(x) at maximal excursion

22W_8857T bl 22W_8857T bl symmetry 22W_8857T cms

22W_8857T kms

22W_8857T kms symmetry  22W_8857T lx 22W_8857T li

SB Acoustics SB23NACS45-8 8″ Woofer


Up for test is SB Acoustics’ SB23NACS45-8, 8″ Woofer.

After looking at Revel’s new(ish) Performa3 Lineup, I realized that they are, at least in part, using SB acoustics drivers.  The Revel F208 uses (2) 8 inch woofers, which bear a striking resemblance to the SB’s under review here.Though, most certainly tweaked to fit their needs.  6moons.com did a review on the Revel F206 which contains pictures of the SB labeled drivers, pulled from their cabinets. In these pictures you can see the driver model number, containing the same naming scheme SB has for their drivers.  For example: 6moons’  picture of the tweeter in the f206 (here) carries the model number “SB26ADC-C000-4-RVL”.  You’ll notice SB’s site has a tweeter model #SB26ADC-C000-4.

Further, if you view the pictures of the raw woofer drivers, you’ll notice a lot of similarities such as the inverse-ribbed cone, and basket design.  While it seems apparent Revel used SB as an ally in the production of this speaker, odds are high Revel didn’t just use these SB drivers ‘off the shelf’.  One obvious difference is the black cone used in the Revel lineup rather than the aluminum colored cone presented here.  That said, the connection me curious about the ‘raw’ driver performance.  I went to SB’s site and located the 8″ driver.  I contacted Madisound to inquire about the product and was informed it wasn’t on their site just yet as they had recently taken shipment of them.  So, I placed an order for a set and got some testing done recently.

 

First, some photos:

IMG_8495 IMG_8501 IMG_8497 IMG_8498 IMG_8502

Testing the small signal parameters:

I tested both drivers back to back to compare their consistency.  Below are the values obtained for each.

Sample 1 Sample 2 Units Description
Re 5.47 5.48 Ohm electrical voice coil resistance at DC
Le 0.364 0.358 mH frequency independent part of voice coil inductance
L2 0.401 0.379 mH para-inductance of voice coil
R2 2.18 2.17 Ohm electrical resistance due to eddy current losses
Cmes 455 465 µF electrical capacitance representing moving mass
Lces 61.9 64.17 mH electrical inductance representing driver compliance
Res 50.6 48.9 Ohm resistance due to mechanical losses
fs 30 29.1 Hz driver resonance frequency
Mms 30.81 31.177 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 27.223 27.589 g mechanical mass of voice coil and diaphragm without air load
Rms 1.338 1.371 kg/s mechanical resistance of  total-driver losses
Cms 0.914 0.957 mm/N mechanical compliance of driver suspension
Kms 1.09 1.05 N/mm mechanical stiffness of driver suspension
Bl 8.23 8.189 N/A force factor (Bl product)
Qtp 0.423 0.42 total Q-factor considering all losses
Qms 4.338 4.162 mechanical Q-factor of driver in free air considering Rms only
Qes 0.469 0.466 electrical Q-factor of driver in free air considering Re only
Qts 0.423 0.419 total Q-factor considering Re and Rms only
Vas 60.3473 63.1788 l equivalent air volume of suspension
n0 0.334 0.322 % reference efficiency (2 pi-radiation using Re)
Lm 87.44 87.28 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 89.09 88.93 dB nominal sensitivity (SPL at 1m for 1W @ Zn)
Madd 9.75 9.75 g additional mass
Sd 216 216 cm² diaphragm area

IMPEDANCE COMPARE

Overall, the comparison between the two units is pretty much on par.

 

 

Large Signal LSI Klippel Testing:

I didn’t have the time to test both samples so the following is all “Sample 1” driver.

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 5.6 mm Displacement limit due to force factor variation
X C @ C min=75% 3.7 mm Displacement limit due to compliance variation
X L @ Z max=10 % >6.2 mm Displacement limit due to inductance variation
X d @ d2=10% 38 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak 25.39 % Stiffness asymmetry Ak(Xpeak)
Xsym -0.61 mm Symmetry point of Bl(x) at maximal excursion

SB Acoustics SB23NACS45-8 bl SB Acoustics SB23NACS45-8 bl sym SB Acoustics SB23NACS45-8 cms SB Acoustics SB23NACS45-8 kms SB Acoustics SB23NACS45-8 kms sym SB Acoustics SB23NACS45-8 lx SB Acoustics SB23NACS45-8 LI

Aura Sound NS6-255-8A


Aura Sound NS6-255-8A 6.5″ Midwoofer

IMG_8375 IMG_8379 IMG_8377

Small Signal Parameters:

Electrical Parameters
Re 5.69 Ohm electrical voice coil resistance at DC
Le 0.458 mH frequency independent part of voice coil inductance
L2 0.845 mH para-inductance of voice coil
R2 4.4 Ohm electrical resistance due to eddy current losses
Cmes 319 µF electrical capacitance representing moving mass
Lces 18.56 mH electrical inductance representing driver compliance
Res 83.75 Ohm resistance due to mechanical losses
fs 65.4 Hz driver resonance frequency
——————
fm 41.9 Hz resonance frequency of driver with additional mass
Mechanical Parameters
(using add. mass)
Mms 8.984 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 7.477 g mechanical mass of voice coil and diaphragm without air load
Rms 0.336 kg/s mechanical resistance of  total-driver losses
Cms 0.659 mm/N mechanical compliance of driver suspension
Kms 1.52 N/mm mechanical stiffness of driver suspension
Bl 5.307 N/A force factor (Bl product)
Loss factors
Qtp 0.702 total Q-factor considering all losses
Qms 10.98 mechanical Q-factor of driver in free air considering Rms only
Qes 0.746 electrical Q-factor of driver in free air considering Re only
Qts 0.698 total Q-factor considering Re and Rms only
Other Parameters
Vas 13.6902 l equivalent air volume of suspension
n0 0.494 % reference efficiency (2 pi-radiation using Re)
Lm 89.13 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 89.37 dB nominal sensitivity (SPL at 1m for 1W @ Zn)
Sd 121.15 cm² diaphragm area

 

NS6 Impedance Klippel

 

Large Signal Parameters:

 

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 2.5 mm Displacement limit due to force factor variation
X C @ C min=75% >7.3 mm Displacement limit due to compliance variation
X L @ Z max=10 % 5.2 mm Displacement limit due to inductance variation
X d @ d2=10% 18.3 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak 5.03 % Stiffness asymmetry Ak(Xpeak)
Xsym 0.63 mm Symmetry point of Bl(x) at maximal excursion

 

NS6 BL NS6 BL SYMMETRY NS6 KMS NS6 KMS SYMMETRY NS6 L(X) NS6 LX(I)

 

 

Frequency Response:

The below is FR measured at 2.83v/1m, 0, 15, 30, 45, and 60 degrees with the accompanying polar.  You can see I stitched NF and FF at approximately 400hz, as this is where they lined up best for all axes.  These are smoothed to 1/12 octave.

  • 0 Degrees (on-axis) = Green
  • Black = 15 Degrees
  • Dark Red = 30 Degrees
  • Red = 45 Degrees
  • Orange = 60 Degrees

NS6 FR

NS6 Polar

Non-Linear Distortion:

Harmonic Distortion, measured at approximately 5 inches from the cone, SPL emulating 90dB @ 1m.

  • Blue = THD
  • Red = 2nd Order
  • Pink = 3rd Order
  • Green = 4th Order
  • Teal = 5th Order

NS6 HD at 90db_1m

HD with a single tone in the spectrum view (I did this to verify the high odd order distortion seen above): NS6 HD at 1khz

IMD at 90dB/1m.  F1=55hz, F2=440hz (-6dB from F1).

NS6 IMD (1)

IMD at 96dB/1m.  F1=55hz, F2=440hz (-6dB from F1).

NS6 IMD (2)

Seas W18NX-001

*Photo courtesy of Madisound Speaker Store.

Up for test is a Seas W18NX-001.  This is another driver that will be party of Jerry Niebur’s Midwoofer Subjective Shootout next month.

As always, please see my Test Setup and Methods page regarding test criterion.

Let’s get to the data and analysis…

 

Theile-Small Parameters & Impedance

Electrical Parameters
Re 5.79 Ohm electrical voice coil resistance at DC
Krm 0.1518 Ohm WRIGHT inductance model
Erm 0.31 WRIGHT inductance model
Kxm 0.0087 Ohm WRIGHT inductance model
Exm 0.64 WRIGHT inductance model
Cmes 247 µF electrical capacitance representing moving mass
Lces 55.06 mH electrical inductance representing driver compliance
Res 56.6 Ohm resistance due to mechanical losses
fs 43.2 Hz driver resonance frequency
——————
f ct 55.3 Hz driver resonance frequency in enclosure
Mechanical Parameters
(using test encl.)
Mms 15.657 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 13.634 g mechanical mass of voice coil and diaphragm without air load
Rms 1.121 kg/s mechanical resistance of  total-driver losses
Cms 0.868 mm/N mechanical compliance of driver suspension
Kms 1.15 N/mm mechanical stiffness of driver suspension
Bl 7.966 N/A force factor (Bl product)
Loss factors
Qtp 0.399 total Q-factor considering all losses
Qms 3.789 mechanical Q-factor of driver in free air considering Rms only
Qes 0.388 electrical Q-factor of driver in free air considering Re only
Qts 0.352 total Q-factor considering Re and Rms only
Other Parameters
Vas 26.6853 l equivalent air volume of suspension
n0 0.533 % reference efficiency (2 pi-radiation using Re)
Lm 89.46 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom Zn missing dB nominal sensitivity (SPL at 1m for 1W @ Zn)
rmse Z 4.53 % root-mean-square fitting error of driver impedance Z(f)
Sd 147.41 cm² diaphragm area 

 

Klippel Large Signal Analysis

Fairly broad  Bl curve which shows a constant motor force with xmin/xmax (in/out).  Coil out offset at rest which trends toward the center of the magnetic gap at xmech with only a 0.30 inset.

 

Coil out offset which increases from 0.8mm at rest to 1.6mm at xmech.  As you’ll see below, this is what limits the linear excursion (10% THD) for this driver and as a result, Bl related excursion is not able to resolve.

 

The coil in offset makes it hard to tell from this plot, but it’s possible a shorting ring was used in this driver.

 

From this chart, it is easy to see that inductance isn’t a contributing factor in distortion for the low frequency evaluation of the motor.  Both Bl and Kms are contributing fairly evenly.

 

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% >6.0 mm Displacement limit due to force factor variation
X C @ C min=75% 3 mm Displacement limit due to compliance variation
X L @ Z max=10 % >6.0 mm Displacement limit due to inductance variation
X d @ d2=10% 28.4 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak 82.83 % Stiffness asymmetry Ak(Xpeak)
Xsym -0.31 mm Symmetry point of Bl(x) at maximal excursion

 

As you can see from above, suspension was the limiting factor for linear excursion, limiting this driver to 3mm.  Not really what I would consider stellar by any means.

 

Frequency Response and Harmonic Distortion at 2.83v/1m

Good up until about 3khz in all measured axes.  A potential mode at 4khz (as indicated by the same peak in response in all axes).  Overall low distortion at this measurement distance/level to about 4khz where the THD breaks 1% (PHD level of -40dB).

3rd order distortion appears to be an issue at the 1-2khz range at this level.  But, as you see below, when pushed harder, 2nd order takes over and 3rd order remains relatively low.

High Output Harmonic Distortion

Very low 3rd order distortion from 100hz up to about 1khz where it increases slightly.  Very slightly.

2nd order distortion is the main culprit of distortion here and shows signs of concern centered about 900hz and 4khz.  On the low end, 2nd order still dominates, however, 3rd order starts rapidly increasing above 80hz.  At about 68hz, THD is above 3% and 3rd itself is above 3% at 60hz.

IMD Voice Sweep

Overall distortion results show an increase in distortion above 3khz.  So, like with FR, I wouldn’t necessarily recommend using this driver above that.  No matter, as polar response matching wouldn’t yield good results above this frequency anyway.

At its worst, this driver gives up about 0.70dB to compression at 4khz where the mode appears to be.  Overall there’s about 0.30dB lost to compression in the main passband up to about 3khz.

 

 

IMD (Bass Sweep)

Third harmonic takes over below 60hz.

At 90hz, compression results in a loss about 0.40dB.

JBL 660GTi Midwoofer Testing

This testing is for only the midwoofer from JBL’s 660GTi Component Set.  This is said to be JBL’s flagship component speaker and the way it’s presented to the consumer, complete with steel briefcase and intricate packaging, certainly make it seem that way.  My friend owns this set and let me borrow it all to test the mid to see just how well this particular driver in the set performs on its own.  At some point, I’d like to test the tweeter in the waveguide, but for now I’ll just test the midwoofer.

As a side note, this driver will be used in a co-hobbyist’s upcoming Subjective Evaluation Test and we both wanted to be able to see if there is a way to correlate subjective opinions vs objective measurements.

Please see this link for information on how the test was performed.  This saves me some much needed time.  😉

 

Thiele-Small Parameters and Impedance

Electrical Parameters
Re 3.04 Ohm electrical voice coil resistance at DC
Le 0.135 mH frequency independent part of voice coil inductance
L2 0.68 mH para-inductance of voice coil
R2 3.42 Ohm electrical resistance due to eddy current losses
Cmes 379 µF electrical capacitance representing moving mass
Lces 16.97 mH electrical inductance representing driver compliance
Res 72.14 Ohm resistance due to mechanical losses
fs 62.7 Hz driver resonance frequency
——————
f ct 70 Hz driver resonance frequency in enclosure
Mechanical Parameters
(using test encl.)
Mms 10.36 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 8.86 g mechanical mass of voice coil and diaphragm without air load
Rms 0.379 kg/s mechanical resistance of  total-driver losses
Cms 0.621 mm/N mechanical compliance of driver suspension
Kms 1.61 N/mm mechanical stiffness of driver suspension
Bl 5.227 N/A force factor (Bl product)
Loss factors
Qtp 0.439 total Q-factor considering all losses
Qms 10.784 mechanical Q-factor of driver in free air considering Rms only
Qes 0.455 electrical Q-factor of driver in free air considering Re only
Qts 0.437 total Q-factor considering Re and Rms only
Other Parameters
Vas 12.8174 l equivalent air volume of suspension
n0 0.669 % reference efficiency (2 pi-radiation using Re)
Lm 90.45 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom Zn missing dB nominal sensitivity (SPL at 1m for 1W @ Zn)
Sd 120.76 cm² diaphragm area

 

 

 

Large Signal Analysis

This analysis module from Klippel is the cream of the crop.  It provides significant insight in to the inner workings of the driver under test in a way that some manufacturers can not attain.  What you’ll see below is this driver has a very long linear stroke providing a measured mechanical Xmax of approximately 11.3mm (one-way) with a corresponding linear Xmax (xmax value defined by the 10% distortion limit) at 7.4mm (one-way).  From my previous testing, this is 3rd only to the Exodus Anarchy (with a measured 7.7mm) and the Scan Speak 18wu (9.1mm).  Note the mounting depth of the JBL driver is roughly 20mm less than the Exodus and 24mm less than the Scan.  Nearly 3/4″ and 1″, respectively, less.

Table Summary

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 7.4 mm Displacement limit due to force factor variation
X C @ C min=75% 8.9 mm Displacement limit due to compliance variation
X L @ Z max=10 % >10.3 mm Displacement limit due to inductance variation
X d @ d2=10% 18.7 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak -10.42 % Stiffness asymmetry Ak(Xpeak)
Xsym 0.19 mm Symmetry point of Bl(x) at maximal excursion

 

As seen above, the suspension has coil out offset at rest of about 0.4mm and a coil in offset at mechanical xmax of 0.52mm.

The force factor shows an outward offset at rest of nearly 2mm with no assymetry at full excursion at 11.2mm.

 

The above graphs show inductance is a very small contributing factor to the overall distortion contribution where force factor (Bl) is the highest factor, and suspension is 2nd highest.

What this all means is that this driver’s motor and suspension are well implemented designs and keep the driver’s stroke very linear in regards to distortion characteristics which gives it a very high Xmax value, especially given it’s smaller size compared to the two highest rated Xmax drivers I mentioned above.

 

Frequency Response and Harmonic Distortion at 2.83v/1m

Good usable range in all axes up to about 3khz where the rolloff at 60 degrees begins to become more severe.  At 30 degrees off axis, the response is good to about 4khz.  On-axis response is good to about this same spot where there is a bump in response, which likely helps the off-axis response at 30 degrees.

Overall, HD isn’t bad.  Comprised mainly of 2nd order distortion.

High Output Harmonic Distortion

At higher output levels you can see that 3rd order distortion becomes practically a non-issue.  The separation in odd order harmonics from even (and namely the 2nd order component) is superb with nearly a constant 20dB delta between 3rd and 2nd order above 200hz and 10dB difference at 80hz.

The areas to potentially be concerned with would be the areas with the higher peaks in distortion.  Namely 1khz and 4khz.  However, my personal threshold being 3% THD, these are still below that.  Below 60hz, the driver exceeds that 3% THD mark and 3rd order begins to increase to a point where it more closely matches 2nd order.

From the fundamental response, you can see the driver plateaus before rolling off on the low end at about 72hz.

As mentioned above, this driver non-linear distortion profile is nearly all 2nd order distortion.  Given the tradeoff, this is a good one and will be less offensive (if audible at all) to the listener than 3rd order and subsequent odd order distortion.

Intermodulated Distortion (Voice Sweep)

As with HD testing above, these two results show a higher 2nd order distortion profile than 3rd order distortion, which contributes almost exclusively to the THD results.

You can see the difference in distortion levels as the input voltage is increased as well.

IMD results indicates a rising distortion profile above 2khz in 2nd order, while 3rd order distortion remains nearly constant (keep in mind the scale).

Compression is simply a means to display how much output is lost at higher volumes compared to the initial measurement.  In this case, at about 1khz the largest amount of output is lost.  However, this is only 0.5dB loss from 1v input to 6v input.

Intermodulated Distortion (Bass Sweep)

This is where you can see 3rd order distortion becoming an issue.  However, it’s maximum is 1.8% at about 33hz.  This is well beyond where anyone would likely be running this driver.

Note the larger delta in the stepped voltage measurements between 4.33v and 6.0v compared to the other intervals in this measurement.

Second order distortion is still the top dog here.

Using 50hz as a reference point, there is less than 0.20dB loss due to compression.

Conclusion

The bottom line is this driver is extremely impressive.  The 3rd largest linear Xmax I’ve measured with excellent mechanical throw overall.  Excellent distortion curves with an extremely low 3rd order distortion component.  When used from 80hz to 2khz, this is probably one of the top tier drivers I’ve measured to date.  It can be used beyond that passband but individual user needs will dictate experience.  It definitely has the gusto to take some loud listening levels and contain its composure.