HSU VTF-15H + Velodyne CHT-15 Subwoofers + HSU MBM-12 Integration - Group Delay & Phase Verification

[andrewtungnguyen]

System: In signature
Playback: –25 dB FLAC via WiiM Pro Plus (manual PEQ)
Mode: Stereo Pure Direct, LFE + Main (full-range mains)
Mic: Zoom H4n Pro stereo at MLP, ~6" below tweeter height
Smoothing: 1/12 octave
Calibration: Manual delay/gain alignment using miniDSP 2x4 HD
EQ applied via WiiM Pro Plus PEQ and miniDSP filters
No high-pass on mains

Note: Measurement shown is left channel only. Mic was centered at MLP. Stereo behavior confirmed separately via dual-channel recording.

Group Delay
GD remains under 125 ms across the active range
18 Hz peak corresponds to sub tuning
No group smear, port ring, or modal decay stacking observed

SPL + Phase
Acoustic crossover emerges around ~110 Hz via summation
Phase slope is continuous, no wrap, inversion, or combing
Sub, MBM, and mains blend time-aligned

Stereo verification (Zoom H4n Pro):
Crest factor >17 dB
Phase-stable response confirmed down to ~1.75 Hz
No modulation blur under dynamic playback

Future upgrade: dual MBM stack (converted PSW10) (sealed + ported-mod) with external amp and coax split planned to remaining miniDSP output.

 

[andrewtungnguyen]

All manual calibration, no Dirac, no Trinnov. Just MiniDSP and ears. Group delay flattened. Phase coherent. Sub timing locked. Crest symmetry: 0.984. Delay offset: 0.00 ms. Took a while, but worth it. Still tweaking, but here's where it's at.

 

[andrewtungnguyen]

FLAC was talk by Khalid so you can see the system is not adding additional midbass that was not intended by the original mix / song. Just pure clean phase aligned punch from mbm-12 no midbass bloating.