Questions about how it works? https://loudspeakerlab.io/faq
Questions about accuracy? https://loudspeakerlab.io/case-studies/mechano23-klippel-vituixcad-loudspeakerlab
Honestly, never thought I’d have the opportunity. I’m coming from a 36FS120 and thought “how big of a difference could it be?” Well, brother, I’m a believer now. This thing looks more like my PVM than it does the FS120
Mechano23 is an unusually good DIY validation case. XMechanik published an excellent open-source speaker design and shared the driver measurements and VituixCAD project files in the original Mechano23 AudioScienceReview thread. Amir later measured the finished speaker on the Klippel NFS and shared images and measurement data in the Mechano23 AudioScienceReview review thread. That gives us a rare chance to compare the full chain: raw driver measurements, design software predictions (VituixCAD, LoudspeakerLab), and real-world loudspeaker performance.
The goal of this post is to explore how close modeled designs get to real-world results and how the completeness of the measurement dataset affects accuracy. Also, how does LoudspeakerLab compare to the current DIY reference workflow in VituixCAD? Finally, how much do we give up if we design from manufacturer spec-sheet data instead of in-cabinet measurements?
Error cells are median / p95 / max dB over 100 Hz-16 kHz. SPL curves are level-aligned over 300 Hz-1 kHz before acoustic shape comparisons; DI is not level-aligned.
| Source | Input data | Angular coverage used by LL |
|---|---|---|
| VituixCAD | Shared Mechano23 VituixCAD project exports from in-cabinet driver measurements | As exported by VituixCAD |
| LoudspeakerLab | Same in-cabinet driver measurement family, public LL design | H 10..180 plus signed V -170..180 for both drivers |
| LoudspeakerLab (spec sheet) | Manufacturer FR/ZMA and sparse manufacturer horizontal polars | H30/H60 only; LL estimates the missing vertical and rear surface |
This shows the delta (p95 error) between the Klippel data from Amir and the values from VituixCAD, LoudspeakerLab, and LoudspeakerLab using spec-sheet data. Lower is better on all scores except Preference Rating. p95 error is in dB over 100 Hz-16 kHz after level-aligning SPL curves over 300 Hz-1 kHz. Directivity Index is not level-aligned.
| Source | On-Axis | Listening Window | Early Reflections | Sound Power | Predicted In-Room | Directivity Index | Preference Rating (no LF) |
|---|---|---|---|---|---|---|---|
| VituixCAD | 2.04 | 2.07 | 2.14 | 2.22 | 2.12 | 1.38 | 8.148 |
| LoudspeakerLab | 1.39 | 1.34 | 1.15 | 1.13 | 1.05 | 1.74 | 8.081 |
| LoudspeakerLab (spec sheet) | 3.18 | 2.34 | 1.56 | 2.64 | 1.62 | 4.00 | 7.122 |
Klippel's VXC-style score from the extracted reference curves is 7.920. The shared VituixCAD materials report 8.139, which is close to the recomputed value from these curves.
| Source | Minimum impedance | Impedance p95 vs Klippel | Crossover transfer p95 vs VituixCAD |
|---|---|---|---|
| VituixCAD | 4.13 ohm @ 219 Hz | 1.56 ohm | reference |
| LoudspeakerLab | 4.13 ohm @ 217 Hz | 1.48 ohm | W 0.07 dB / T 0.01 dB |
| LoudspeakerLab (spec sheet) | 1.42 ohm @ 40 Hz | 3.08 ohm | W 1.48 dB / T 0.35 dB |
The in-cabinet models are close enough to the Klippel curves to be useful design tools rather than rough sketches. VituixCAD lands at 2.04 dB p95 on-axis error and 2.07 dB Listening Window p95 error after level alignment. LoudspeakerLab gives lower error at 1.39 dB and 1.34 dB on the same metrics.
The practical takeaway is that robust in-cabinet measurements remain the high-confidence path. They already contain the real baffle, mounting, diffraction, grille-less driver integration, sample variation, and low-frequency loading behavior. The software still has to sum drivers, apply offsets, apply crossover transfer functions, and calculate CTA curves, but it is no longer being asked to invent the loudspeaker from generic driver curves.
One key difference between LoudspeakerLab and similar speaker modeling tools is its ability to "unload" and "re-load" the box and baffle from measurements if those measurements were taken in a cabinet versus on a large measurement baffle. This cabinet/baffle unload-reload path exists for the core purpose of measurement re-use. An in-cabinet driver measurement is not just the driver; it also contains the measurement box, baffle, mounting, and low-frequency loading. VituixCAD's classic workflow works when those measurements are already from the final cabinet. LL's unload/re-load process makes the same driver profile reusable in other designs by estimating measured in cabinet A -> remove cabinet A/baffle A -> apply cabinet B/baffle B. The higher agreement here is best read as a useful by-product of that architecture, incorporating accurate box and baffle models based on T/S parameters to help estimate anechoic speaker behavior.
On the directly measured response curves, LoudspeakerLab is lower-error on On-Axis, Listening Window, and Early Reflections, at least for Mechano23. VituixCAD is lower-error on Directivity Index (1.38 dB p95 for VituixCAD versus 1.74 dB for LoudspeakerLab). That is the main place where LL trails in the headline graphic.
I studied this to try to better understand why, since they use the same source measurements and crossover, and the strongest clue is the cabinet/baffle ablation. When I used the same LL in-cabinet FRDs directly and bypassed LL's measurement-cabinet/baffle unload and target-cabinet/baffle reload step, the main errors become VituixCAD-like: On-Axis 2.05 dB, Listening Window 2.06 dB, and Early Reflections 2.10 dB. With the normal LL process, those are roughly 30-40% lower: 1.39, 1.34, and 1.15 dB. That suggests the unload/reload process is likely a real contributor to LL's stronger front-curve agreement in this Mechano23 case.
The electrical transfer overlay is the strongest sanity check: LoudspeakerLab's in-cabinet crossover transfer differs from VituixCAD by only about 0.07 dB p95 on the woofer and 0.01 dB p95 on the tweeter, essentially the same. So it is acoustic modeling, not electrical modeling, that produces this lower error.
The spec-sheet model gives a view into the widely accessible speaker design use case. Making in-cabinet spherical measurements requires a lot of expertise, expense, and effort. You have to buy the drivers, build the cabinet, and then actually take the 72 measurements correctly. Alternatively, you could use manufacturer FR/ZMA files or scraped spec-sheet data to get sparse manufacturer horizontal polars, then ask LL to predict the cabinet/baffle transformation, vertical behavior, rear radiation, acoustic offsets, and system integration. This is not as accurate as the in-cabinet spherical measuring process, but the quantification of the gap is interesting. On-Axis p95 error is 3.18 dB, Listening Window is 2.34 dB, and Directivity Index is 4.00 dB: higher, but not unusable to create a high-quality speaker design.
The electrical side points in the same direction. The spec-sheet model's impedance mismatch is much larger than the in-cabinet models, especially in the low-frequency region where box alignment and driver parameters dominate. That is a reminder that manufacturer ZMA/T/S data can be perfectly legitimate for its fixture and still be a poor stand-in for the exact driver/box/crossover combination being built.
That does not make the spec-sheet workflow worthless. It can get a plausible design into the right neighborhood, especially for early crossover exploration and enclosure sizing when no measurements exist. This can be helpful in making driver purchase decisions and later making spherical measurements, or accepting the lower-accuracy spec-sheet design as final. But this comparison argues against treating it as interchangeable with in-cabinet data. Manufacturer curves are measured on standardized baffles and fixtures, often on different driver samples, with different boundary conditions than the finished speaker. LL can model the transformation, but it cannot recover information that was never present in the input data.
The Klippel-derived VXC-equation score is 7.920. VituixCAD computes to 8.148, LL in-cabinet to 8.081, and the spec-sheet LL model to 7.122. Those numbers move because the score is sensitive to smoothness, directivity, and bass extension. A model can be close on on-axis response and still diverge in score if Sound Power, DI, or low-frequency extension shifts.
For DIY design work, the score is best treated as a useful summary statistic, not a substitute for looking at the curves. The score is especially vulnerable when Sound Power and DI are based on reconstructed or sparse angular data. That is exactly the region where this study finds the largest remaining LL/VXC/Klippel disagreement.
If you have good in-cabinet driver measurements, both VituixCAD and LoudspeakerLab can produce a model that is meaningfully close to a real Klippel-measured speaker. If you only have manufacturer data, both tools can also still be useful, but will be limited by the input data. This study says to keep expectations realistic: the spec-sheet path is good for narrowing design space, not for proving final performance. The healthiest conclusion is boring in the best way: better input measurements beat cleverer modeling. The encouraging part is that when the input data is comparable, the output is broadly comparable too.
And here are my Mechano23s. I use them nearfield on my desk every day. They really are excellent.
