Audio Dynamics 2510

Overall summary

In this sample and under these test conditions, the Audio Dynamics 2510 shows a fairly clean 1 V baseline distortion measurement through most of the desired subwoofer passband. The 1 V distortion curve is mostly predictable, with THD highest in the low 20 Hz to low 30 Hz region, peaking around ≈3.5 percent. Above that, distortion drops quickly and stays under ≈1 percent through most of the 40 to 120 Hz range. H2 distortion is the dominant harmonic through most of 20 to 120 Hz, while H3 distortion is present at the very bottom but falls off quickly above the very low frequency range.

At 11.5 V, the distortion behavior changes significantly. THD rises sharply at the lowest frequencies, reaching about 30 percent in the low 20 Hz range, then drops in the 40 to 50 Hz region. From about 60 to 120 Hz, the curve becomes a broad H2 distortion led rise around the 7 percent range instead of a narrow spike. H3 distortion along with H2 becomes extremely elevated at the lowest frequencies, but through most of the 50 to 120 Hz range, H2 distortion is the main contributor.

The LSI data shows why this is a mixed result. BL 70 percent occurs at 10.72 mm one way, which supports the manufacturer’s 10 mm xmax claim by the project’s BL standard. CMS 50 percent occurs even farther out at 11.57 mm one way, but the suspension behavior is highly asymmetric, with measured stiffness asymmetry of 50.8 percent. The primary excursion limitation is inductance, with the 17 percent Le criterion occurring much earlier at only 4.10 mm one way.

For sealed use, the manufacturer’s 0.50 ft³ sealed enclosure calculates to a 0.876 Qtc on this sample, while 1.10 ft³ is required for 0.707 Qtc. The small sealed box is usable if a higher-Q result is acceptable, while the larger enclosure gives the ideal Q target. Infinite baffle is not recommended because of the low linear excursion, and the driver loses the sealed air spring that helps control low-frequency excursion, and the Le-based clean stroke excursion limit occurs much earlier than the BL and CMS limits.

Manufacturer's suggested use case

Audio Dynamics positions the 2510 D4 as a shallow 10 inch subwoofer in the 2000 Series, with a 300 to 600 watt optimal power range, 2.5 inch copper voice coil, 160 oz motor, PC spider, double high-current tinsel leads, and ±10 mm xmax. The manufacturer describes the 2500 series 10 as using a balance of damping and motor force to achieve high efficiency and versatility. It is listed as designed for vented enclosures, with 0.60 to 1.25 ft³ net vented volume shown, but the page also provides a 0.50 to 0.60 ft³ sealed volume range. Published sensitivity is 81.06 dB, and mounting depth is listed as 3.862 inches.

Our suggested use case

Based on the data provided here, this sample makes the most sense in sealed enclosures where low-frequency excursion is mechanically supported by the airspace. The manufacturer’s 0.50 ft³ sealed enclosure produces a higher-Q 0.876 Qtc on this sample, while 1.10 ft³ is required for 0.707 Qtc. The practical use case is compact shallow 10 inch sealed subwoofer duty where the user understands that the BL and CMS excursion behavior support the published 10 mm claim, but the Le-based clean stroke ceiling arrives much earlier. Infinite baffle is not recommended.

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: 11.5 volts volts

Approximate electrical power at that limit at 20Hz: ~75 watts. Real power varies with frequency and impedance. volts

Rated power (published): 600 watts

Power used to hit the standardized limits in free air, relative to their xmax rating free air: ~14.4 percent of the rated power was used to hit 70% BL xmax. Hits 10.7 mm in free air with approximately 85 watts of power. Real power varies with frequency and impedance.

Claimed Xmax vs. measured at BL 70%: 10.72 mm one way, 107.2 percent of the manufacturer’s 10 mm claim.

Xmax @ 50% Cms: 11.57 mm one way, 115.7 percent of the manufacturer’s 10 mm claim.

Xmax @ 17% Le: 4.10 mm one way, only 41.0 percent of the manufacturer’s 10 mm claim.

Manufacturer suggested sealed enclosure size (and its resulting QTC): Claimed 0.50 ft³ nets a Qtc of 0.876 on this sample.

Required sealed enclosure for 0.707 QTC: 1.10 ft³ nets a 0.707 Qtc.

Xmax @ 50% Cms: 11.57 mm one way, 115.7 percent of the manufacturer’s 10 mm claim.

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 1/10th 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 11.5 V per the under BL 70 rule derived from LSI for this unit. This sample in this test at this voltage level hit 10 mm at 20 Hz in free air, below the accepted standard of 70 percent of BL. Distortion reported both as percent and by harmonic.

At 1 volt - baseline

The 1 V distortion curve is relatively smooth, with its main rise between 20 and the low 30 Hz range. THD peaks around ≈3.5 percent near the upper 20 Hz to low 30 Hz region, then falls below ≈1 percent by around 50 Hz. From roughly 50 to 120 Hz, the curve stays low with only a small bump around 60 Hz. H2 distortion is the dominant harmonic through most of 20 to 120 Hz. H3 distortion is most visible at the very bottom of the sweep, but it is not the main contributor through the mid-bass range.

At high level voltage (11.5 volts volts)

At 11.5 V, the distortion curve rises sharply at the lowest frequencies, reaching roughly ≈29 percent THD in the low 20 Hz range. H2 distortion and H3 distortion are both elevated at the bottom, with H2 distortion slightly stronger. The curve drops quickly through the 30 to 50 Hz range, then transitions into a broad H2 distortion led rise from about 60 to 120 Hz. In that range, THD sits around the mid-single-digit range rather than forming a narrow spike. H3 distortion stays much lower than H2 distortion through most of the 50 to 120 Hz region, so the upper-bass distortion character is mostly even-order. The response trace keeps the same general shape as the 1 V sweep, so the main change is harmonic distortion magnitude rather than a broad response shift in the subwoofer range. A narrow spike appears around the upper 300 Hz range, but that is outside the primary 20 to 120 Hz subwoofer passband.

Delta - 1 volt distortion vs. high level distortion

The main change from 1 V to 11.5 V is that the low-frequency distortion rises much harder than the rest of the passband. The 1 V curve is smooth and relatively low above the low bass range, while the high-level curve develops a broad H2 distortion led rise through the mid-bass. Harmonic balance also changes at the bottom of the sweep, where H3 distortion becomes much more visible at high level. The broad H2 distortion growth is consistent with the measured BL and CMS asymmetry, especially the substantial CMS asymmetry. The early Le limit is important for the linearity result, but the 50 to 120 Hz high-level distortion rise is not primarily H3 distortion. This subwoofer provides a good example of why Le(x) behavior matters. If you look at where H3 distortion begins to rise on the 11.5 V measurement, it occurs around 50 Hz, which perfectly corresponds to the point where excursion exceeds the 4.10 mm one-way 17 percent Le limit on that sweep. Variations in Le(x) are associated with increased odd-order distortion, and the correlation here is consistent with that behavior.

What this means in practice

Distortion rises noticeably as output increases, especially below about 40 Hz. The 1 V baseline is fairly clean through most of the passband, but the high-level sweep shows a sharp increase in low-frequency distortion and a broader H2 distortion rise through much of the 40 to 120 Hz range. While H2 distortion is generally less objectionable than higher-order harmonics, the data suggests that inductance nonlinearity causing increased H3 distortion, and substantial suspension asymmetry begin influencing performance before the driver reaches its mechanical excursion limits. In real-world use, the driver can achieve its advertised 10 mm xmax and produce solid output, but users pushing for maximum low-frequency output will notice loss of low frequency accuracy and definition before full excursion is reached.

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 occurs at 10.72 mm one way. The BL curve is rounded rather than a flat plateau, with usable width around the manufacturer’s published xmax claim. Force factor tapers more gradually through part of the coil-in direction and falls more noticeably as the driver moves farther coil-out. The BL window itself is not the earliest limit on this sample.

Bl(x) symmetry

The LSI note calls out slight BL asymmetry. The table reports the BL symmetry point at -0.67 mm at xprot, the highest excursion hit during the test set by a protection limit, with BL asymmetry of 11.71 percent. This is enough to contribute some H2 distortion, but it is not the largest asymmetry source in this sample. The CMS behavior is the more significant mechanical asymmetry.

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 excursion limit occurs at 11.57 mm one way, so the suspension does not cap the published 10 mm excursion claim before the BL standard is reached. The compliance curve is strongly offset, with much higher compliance toward the coil-out side and lower compliance through the coil-in side. That means the raw window is wide enough, but the shape is not centered.

Cms(x) symmetry

The LSI note calls out substantial CMS asymmetry, and the table reports line up with that comment with a stiffness asymmetry of 50.78 percent at xprot. The symmetry plot shows the suspension offset staying several millimeters away from center over much of the stroke range. This is consistent with the strong H2 distortion component seen in the high-level TRF data. In this sample, the suspension asymmetry is a larger issue than the BL asymmetry.

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 1.03 mH cold. Le(x) changes strongly with position, rising on the coil-in side and falling on the coil-out side. The 17 percent Le variance criterion occurs very early, at only 4.10 mm one way, making inductance the practical clean xmax ceiling by accepted standards. Based on the inductance behavior, there is no obvious indication of inductance management measures in this sample.

Current dependence

Le(i) shows a moderate upward tilt with current, but the current-related change is smaller than the position-related Le(x) swing.

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 is 0.46 cold near center and 0.51 warm near center. The Qts(x) curve rises as excursion increases in both directions, with a stronger rise toward coil-out. This means damping changes substantially as the driver moves away from rest. The curve is not symmetrical, so the damping behavior changes depending on direction of travel, though the asymmetry is much less pronounced than the suspension curves would make you expect.

LSI takeaway

The earliest standardized limit is the Le 17 percent criterion at 4.10 mm one way. BL supports the published 10 mm xmax claim by the project’s BL 70 percent standard, though the curve is rounded and slightly asymmetric. CMS extends slightly beyond the published xmax claim, but the suspension is substantially asymmetric and is consistent with the strong H2 distortion component at high level. Le(x) varies strongly with position, while Le(i) changes more moderately with current. Qts rises noticeably with stroke, especially toward coil-out, so damping is not consistent near the ends of travel.

Enclosure alignment calculations

Manufacturer sealed enclosured recommendations and the resulting QTC: 0.50 ft³ nets a Qtc of 0.876 on this sample.

Sealed volume required for 0.707 QTC on this sample: 1.10 ft³ nets a 0.707 Qtc on this sample.

Applicable for infinite baffle? Not recommended. Low excursion and high distortion is a bad combo for infinite baffle.

T/S parameters