JL Audio 10TW3 D4

Overall summary

In this sample and under these test conditions, the 1 volt baseline distortion sweep shows aggressive rising distortion into the lowest octave, with THD at 20 Hz going beyond the 10 percent limit of the plotted window and tapering down quickly by the mid-30 Hz region. In this frequency range, both H2 and H3 distortion is prevalent. Between about 40 and 80 Hz THD settles into the low single digits and remains somewhat stable in shape. No strong narrow spikes are obvious in the 20 to 120 Hz band at this drive level outside of the extreme rise in distortion below 35 Hz.

At the near limit sweep of 22 volts, distortion is high across the board and increases as a broad rise toward the bottom rather than as isolated spikes. THD at 20 Hz climbs to about 16 percent, with H3 distortion dominant below ≈25 Hz and H2 distortion dominant from roughly 30 Hz and up. There is a more noticeable hump in distortion through the 30 to 80 Hz band that is around 12 percent THD . A higher frequency distortion peak appears in the upper midbass region that sits above where most subwoofers are commonly crossed, so it is less relevant in typical use.

Large signal data show a BL 70 percent one way limit of 15.52 mm, a CMS 50 percent limit beyond the ±16.07 mm protection window, and a 17 percent Le variance reached at only 6.75 mm one way. BL and CMS both show inward asymmetry, while Le(x) is labeled poor with a strong position dependence and moderate current dependence. These traits line up with the distortion pattern: inward BL and CMS asymmetry correlate with the even order H2 distortion rise across the main band, and the relatively early Le limit is consistent with H3 distortion being most apparent at the very bottom, and can even contribute to the high distortion levels across the board.

For sealed use, the manufacturer’s 0.5 ft³ recommendation computes on this sample to a Qtc of 0.883, while about 1.49 ft³ is required to reach 0.707 Qtc using the Klippel LSI reported large signal cold parameters. In practical terms that means a compact sealed enclosure will play slightly higher in Qtc, while the larger enclosure trades some of that for deeper extension. Because the inductance limit occurs first on this sample, thermal and excursion headroom in very small enclosures are not the only constraints.

Overall, in this test with this sample, this driver produces high distortion, has some pretty extreme asymmetries, and has high inductance and inductance variance. It does not seem to be a good option if accurate reproduction in a sound quality system is your goal.

Manufacturer's suggested use case

The manufacturer positions the TW3 series as thin line subwoofers built for tight space applications. They feature a cast alloy frame with only 3.25 inches mounting depth on the 10 inch model, and is intended for sealed or ported enclosures between compact and moderate volumes. Published specifications include 400 watt continuous power handling, 15.2 mm one way xmax, 82.10 dB sensitivity at 1 W/1 m, and a recommended sealed enclosure of 0.80 ft³ for this 10TW3 D4.

Our suggested use case

Based on this sample and these measurements, the TW3 10D4 is best suited for the larger end of average sized sealed enclosures where depth is limited. The recommended 0.5 ft³ sealed enclosure produces about 0.883 Qtc on this sample, which is reasonable for most automotive installations. A larger enclosure such as 1.49 ft³ reaches approximately 0.707 Qtc and gives deeper extension. Because the inductance based 17 percent variance limit (6.75 mm one way) occurs well before BL or CMS limits, multiple drivers are the straightforward path to improving clean headroom if low distortion is a priority. The driver can be used in large sealed spaces, but expectations for low distortion at high output below the mid 30 Hz region should be tempered.

Testing and linearity limits vs. what is advertised

What it took to reach our high-level sweep limit, and how that compares to the published specs.

High-level sweep rule: Set just under the BL 70 percent point from LSI

High-level sweep limit for this sample: 22 volts

Approximate electrical power at that limit at 20Hz: ~200 watts. Real power varies with frequency and impedance. volts

Rated power (published): 400 watts

Power used to hit the standardized limits in free air, relative to their xmax rating free air: ~50 percent. Hits 15.5 mm 70% BL xmax in free air with 200 watts of power. Real power varies with frequency and impedance.

Claimed Xmax vs. measured at BL 70%: 15.52 mm, ≈102.1 percent of the manufacturers claim of 15.2 mm

Xmax @ 50% CMS: > 16.07 mm, > 105.7 percent of the manufacturers claim of 15.2 mm within the evaluation window

Xmax @ 17% Le: 6.75 mm, ≈44.4 percent of the manufacturers claim of 15.2 mm

Manufacturer suggested sealed enclosure size (and its resulting QTC): Manufacturer suggested 0.5 ft³ nets a QTC of 0.883

Required sealed enclosure for 0.707 QTC: 1.49 ft³ nets a 0.707 QTC

Xmax @ 50% CMS: > 16.07 mm, > 105.7 percent of the manufacturers claim of 15.2 mm within the evaluation window

Overall performance snapshot

This is our subjective interpretation of the objective data. How we derive these scores can be found on the home page of the testing section.

Distortion & frequency response - TRF measurements

Method recap: Method recap: Nearfield mic positioned at 1/10 the cone diameter plus 2 inches, on‑axis. Response measured to 1 kHz and THD to 500 Hz. 1/6‑oct smoothing. Two drive levels: 1 V baseline and a high level set at 22 V per the under‑BL‑70 rule. In this sample, at that drive level the unit reached about 15 mm at 20 Hz in free air. Distortion reported both as percent and by harmonic.

At 1 volt - baseline

Distortion rises into the lowest octave, with THD at 20 Hz passing the top limit of the visible 10 percent window. H2 and H3 distortion are both prevalent below 35 Hz. Above about 40 Hz, distortion sits at a relatively normal level without any extreme narrow spikes.

At high level voltage (22 volts)

Distortion increases as a broad plateau, averaging around 10 percent in the usable range. THD at 20 Hz reaches about 16 percent, H3 distortion dominates below ≈25 Hz, and H2 distortion dominates from ≈30 Hz and up. The 30 to 80 Hz region shows much higher distortion than baseline, but the general shape remains relatively consistent. No persistent narrow spikes appear in the 20 to 120 Hz band at this level. Distortion is just high in general across the entire frequency range.

Delta - 1 volt distortion vs. high level distortion

Compared with the 1 volt run, the 22 volt sweep shows a much higher broadband distortion level from 20 to 120 Hz, with the largest relative increase from roughly 30 Hz through the low midbass. The sweep was set just under the BL 70 percent limit and remained below CMS 50 percent. The increased even order distortion aligns with inward BL and CMS asymmetry, while the early Le limit is consistent with stronger H3 distortion below ≈25 Hz. No level invariant spikes appear between the two sweeps.

What this means in practice

In this sample and under these test conditions, distortion is high at typical use levels: the 1 volt baseline already shows THD near and even above 10 percent at lower frequencies with a few percent through much of 30 to 120 Hz, and the 22 volt sweep pushes THD into the mid teens at 20 Hz with several percent across most of the subwoofer band. H3 distortion dominates below ≈25 Hz while H2 distortion dominates from roughly 30 to 120 Hz, so both even and odd order distortion stay significant as level rises. The large increase in distortion from 1 volt to 22 volts is consistent with the early 17 percent Le limit at 6.75 mm one way, meaning inductance behavior rather than BL or CMS is what sets the practical clean stroke ceiling for end users on this sample. Long story short, this sample in this test is not reproducing the input signal very accurately and is not a good choice for applications where sound quality is a priority.

Motor & suspension linearity - LSI measurements

Method recap: Klippel LSI large-signal identification for this unit, cold and used for enclosure computations. Standard thresholds in this project are BL 70 percent, CMS 50 percent, and a 17 percent inductance variance criterion. Commentary below ties the large-signal behavior to the acoustic results.

Bl(x)

Bl(x) shows how much motor force a speaker produces as the voice coil moves, B is magnetic field strength and L is the wire length in that field. A high, wide, symmetrical BL curve means linear control and low distortion, a steep or uneven drop means earlier output limits and rising distortion, which is why BL(x) is often the most telling single Klippel LSI indicator of real performance.

Bl(x) window and shape

BL 70 percent is 15.52 mm one way. The BL curve shows a reasonably broad shelf with an off-center peak, sustaining motor force over most of the stroke. The shape is not as flat nor symmetrical as it should be.

Bl(x) symmetry

The BL symmetry point is ≈ −1.63 mm at full excursion, but is approximately 4mm off center at low excursion and is showing a moderate inward bias. This is consistent with the increased H2 distortion observed across the entire bandwidth.

Cms(x)

Cms(x) is suspension compliance versus displacement, the inverse of stiffness. When the curve is broad and symmetrical, motion is linear and distortion stays low. Early roll off or offset indicates progressive stiffening or mis-centering, which adds mechanical distortion and caps clean excursion.

Cms(x) window and shape

CMS 50 percent is not reached within the ±16.07 mm window, which is favorable for suspension headroom. The suspension maintains usable compliance across the tested range.

Cms(x) symmetry

Suspension asymmetry is somewhat extreme, and is approximately 2.5mm off center at full excursion, but as far off center as 9mm at low excursion. This also aligns with even order distortion levels present in the TRF data.

Inductance - Le(x) and Le(i)

Le(x) and Le(i) measure how a subwoofer’s voice coil inductance changes with position and current. These curves show how stable the motor’s magnetic field is under real movement and drive conditions. When inductance varies heavily, it causes distortion, uneven response, and a loss of upper-band clarity, which is why Le(x) and Le(i) are critical for evaluating how clean and consistent a motor’s behavior really is.

Level and shape

Le at rest is 2.24 mH. The 17 percent Le variance threshold occurs at 6.75 mm one way excursion, earlier than BL or CMS, making inductance the earliest practical clean limit. Le(x) variation is moderate to strong and aligns with the H3 distortion behavior at the bottom.

Current dependence

Le(i) shows moderate current dependence.

Qts(x)

Qts(x) is the driver’s total damping versus excursion, combining electrical and mechanical losses. Stable, symmetrical Qts(x) means consistent control, while large variation or asymmetry signals uneven damping that can shift response, raise distortion, and cause compression.

Qts stability

Qts at center is 0.57 cold, rising with both stroke and temperature. QTS across stroke is very asymmetrical due to the asymmetries listed above. Control decreases outward, aligning with the rise in distortion at higher excursion.

LSI takeaway

On this sample the earliest limit is inductance, with the 17 percent Le variance limit reached at 6.75 mm one way excursion, so Le sets the practical clean stroke ceiling. Both BL and CMS show large low-excursion asymmetries, which align with the strong H2 distortion across the band. The BL curve is off centered with a non-flat peak, and CMS is heavily shifted, especially at small stroke, so even-order distortion is expected to stay high as level rises. Inductance varies strongly with position and shows early departure from linearity, which matches the dominant H3 distortion below about 25 Hz. Qts rises with stroke and is also very asymmetric, indicating weakening control at higher drive, which helps explain the broad distortion growth at real-world playback levels.

Enclosure alignment calculations

Manufacturer sealed enclosured recommendations and the resulting QTC: 0.5 ft³ sealed nets a Qtc of 0.883 on this sample.

Sealed volume required for 0.707 QTC on this sample: 1.49 ft³.

Applicable for infinite baffle? Not exactly; with Qts ≈0.57 and 1.49 ft³ required for 0.707 Qtc, the driver is clearly optimized for average sized sealed use.

T/S parameters