Why EMMA Retests Your System at +6dB (The OSB Quirk Explained)

This is one of the least understood parts of the Sound Quality sheet, and it catches out systems that sound great at a polite listening level and fall apart the moment someone turns it up. Here's exactly how it works and why it's there.

What actually happens

Overall Spectral Balance is scored twice on the same track: once at normal volume, and once at roughly 6dB louder — judges are told to step the volume up by at least two or three clicks from the head unit, adjusting for how that unit's steps are sized. Both passes are scored 0–30. See our full EMMA Sound Quality scorecard breakdown for where this sits in the overall sheet.

The scoring logic

• If the balance holds up better at the higher volume, judges can add 1 to 3 points.
• If it falls apart — gets harsh, boomy, loses control — judges can deduct 1 to 3 points.
• If there's a bigger swing than that in either direction, judges are told to check in with the head judge rather than just score it themselves.

Why this exists

A lot of tunes are dialled in by ear at one comfortable listening level and never properly checked anywhere else. That can mask real problems: a port that starts to chuff at higher output, a crossover point that sounds fine quiet but gets harsh loud, or a system that's simply being driven past what the components can cleanly handle. The +6dB retest exists specifically to catch systems that were tuned to sound good at one volume and nowhere else.

What to actually do about it before competition day

• Don't just tune at your favourite listening level. Check your reference tracks at a noticeably higher volume too, and listen for the same things a judge would: does the balance hold, or does one band start to dominate and mask the rest?
• Pay particular attention to whether bass stays controlled rather than boomy, and whether the top end stays smooth rather than turning harsh or tinny — see our Audio Wheel vocabulary page if you're struggling to pin down exactly what's changing as the volume climbs.
• If your system genuinely can't hold together at a louder level, that's a build or component limitation worth knowing about before the day, not discovering it mid-score.

A system that only sounds good at one volume was tuned for one volume. The +6dB retest is EMMA's way of checking whether what you built actually holds up, not just what you fine-tuned by ear on a quiet Sunday afternoon.

This connects directly to Listening Pleasure too — judges are trained that the two scores shouldn't be far apart under normal circumstances, which the Sound Quality scorecard page covers in more detail.