The Optimal Audio Cuboid 15 ranks #16 out of 32 total Surface-Mount and Background Music Speakers for sound quality. See all PA & Live Sound rankings for every top pick.
Brand: Optimal Audio
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#16 Optimal Audio Cuboid 15: $1,035 each Passive eBay
Pros: A larger member of Optimal Audio’s Cuboid installation range, with a 15-inch woofer that reaches 45.0Hz at -3dB in vendor measurements, deep for an installation box, and a cabinet matching the smaller Optimal Audio Cuboid 5. Measured bass extension of 30.9Hz (-10dB).
Cons: Directivity is uneven (4.54dB variation) and the on-axis response is uneven (0.84 band deviation), so it scores 1.94 on its own and 3.71 with an ideal subwoofer. It is sold through Allen & Heath and Optimal Audio installers with no US retail listing.
| Bass Extension (-10dB) | about 30.9Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) |
|---|---|
| Bass Extension (-3dB) | 45.0Hz (measured, manufacturer data via spinorama.org) |
| Bluetooth | No |
| DIY Kit | No |
| Drivers | 15” woofer, 2-way |
| Passive | Yes |
| Spinorama Preference Score | 1.94 (spinorama.org) |
| Spinorama Preference Score with Perfect Sub | 3.71 (spinorama.org) |
- Reviews, Comparisons and Sound Samples
Frequency Response
How the Optimal Audio Cuboid 15 measures across the audible range. A flatter listening window (the sound arriving straight at you) is more neutral: peaks sound forward or harsh, dips sound recessed. The estimated in-room response adds what a typical room does, and there a gentle, even tilt down toward the treble is ideal. Both curves are shifted so their 300 Hz to 3 kHz average sits at 0 dB.
Measurement data: spinorama.org, measured by the manufacturer.
EQ for a Neutral Response
Flattens the measured listening window from the Optimal Audio Cuboid 15's own bass extension up to 16 kHz. Set a preamp of -2.8 dB, then add these filters to any parametric equalizer in the signal path: the speaker's app or DSP if it has parametric EQ, a miniDSP, Equalizer APO or Wavelet. Boosts are kept to 3 dB, and EQ cannot fix how evenly the speaker spreads sound off-axis, which is why some speakers gain more than others. Predicted preference score with this EQ: 3.8, up from 1.9 (5.5 with an ideal subwoofer, up from 3.7). Calculated by Speaker Ranking from the spinorama measurements above.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| High shelf | 8,000 Hz | -1.4 dB | 0.70 |
| Peak | 79 Hz | -6.0 dB | 1.44 |
| Peak | 465 Hz | -2.6 dB | 2.70 |
| Peak | 855 Hz | +2.0 dB | 4.00 |
| Peak | 1,298 Hz | -1.6 dB | 4.00 |
| Peak | 2,231 Hz | +3.0 dB | 3.51 |
| Peak | 4,490 Hz | -2.4 dB | 1.90 |
| Peak | 7,547 Hz | -2.1 dB | 3.09 |