Thursday, February 17, 2011

OK, just the basic EQ's now

OK, until I can figure out what I'm doing better, I'm a bit worried about using high Q peaks to fix dips as I was apparently doing with some success on Tuesday.

So I'm back to making this optional EQ #1 in Tact:

Cut at primary resonances:   -3dB 42 Hz  (this is very conservative adjustment, could use lots more)
Small boosts to midbass" +2.2dB at 125 and 140 hz
NEW: small cut to high end, -0.7dB at 13.7kHz

Sounds quite nice this way.  The new small cut to the high end seems to remove high end glare on Shadowfax "Nuclear Village" album.  No EQ sounds fine until you try the EQ, then you don't want to go back.  If high end cut is increased to 3dB, however, it sounds too dull on top.

Meanwhile, I was thinking why automated Tact didn't work.  Tact seems to show Acoustats peaking in room at 18kHz.  Other measurements with SPL meters and sinewaves suggests the Acoustats peak at 13.8kHz and fall off above that normally.  I retested that using ST 1100A distortion analyzer as my sine generator and Galaxy 140 SPL meter and GR 1933 SPL meter.

GR is very hard to interpret because being random incidence.  The Galaxy shows about -3dB at 15kHz and -6dB at 16kHz, definitely does not look like 18kHz peak.

However, unfortunately, Galaxy is only Class II rated to 8kHz.  The rolloff I am seeing could very well be rolloff in the meter itself.

Or it could be, as I've suspected, that the Tact microphone isn't calibrated correctly.  If the calibration, for example, shows -12dB at 18kHz, but the mike is actually flat, it would add a high frequency peak at 18kHz in the measured response.  On Tact user's group, complain about mike calibration is legendary, a standard recommendation is to scrap the manufacturer's calibration and simply substitute a generic calibration for the mike.

It's also very hard to measure with high frequency sine waves.  Tiny changes in position or angle can make 6dB or greater difference.  At each measurement, you need to move the mike around a bit to find a solid reading.  It would be nice to have warble generator.  However, the best of all would probably be RplusD from Acoustisoft (formerly known for ETF).  Can get whole package including calibrated mike.  I think I will do that this month.

No comments:

Post a Comment