Bfish,
Thanks for all the good info.

I narrowed the problem down to an interaction between HOLMimpulse and my sound card, an Echo Indigo I/O. Only when a soundcard calibration is used does the caca at 2 msec appear on the IR plot. I don?t know why though?there was no problem when I tried REW (room eq wizard) using a soundcard cal.

Originally I was so focused on the FR plots that I neglected IR ones. I really wish I had magnified and examined the IRs much earlier, before making a multitude of measurements. Now I?ll have to re-measure everything. I tried erasing the soundcard calibrations from my data files, as well as un-checking the calibration box in HOLM, but had no luck. Once the soundcard file is enabled, it seems to become an integral part of the measurements.

Next on the agenda is running some tests using RMAA (thanks again, bfish).

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today--

HOLM, measurement of the speaker -- caca at 2 msec still there.


HOLM, measurement of something different (JBL) -- caca at 2 msec still there.


Abandoned HOLM


Installed REW (room eq wizard) & made soundcard calibration.


REW, measurement of the speaker -- caca at 2msec not there
http://img185.imageshack.us/img185/5976/rewb.png


HOLM, restarted, cleared everything, & reset default settings


HOLM, measurement of the speaker, without soundcard calibration -- caca at 2 msec not there
http://img155.imageshack.us/img155/1361/holmwo.png


HOLM, made soundcard calibration
http://img710.imageshack.us/img710/3449/loop.png


HOLM, re-measurement of the speaker with soundcard cal -- caca at 2 msec back again.
http://img294.imageshack.us/img294/1223/holmwith.png

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Echo Indigo I/O soundcard: CardBus-format soundcard for PCs and Macs with two-channel analog inputs and outputs on stereo 1/8" connectors, 128x-oversampling A/D and D/A converters, 24-bit data resolution maintained throughout signal path, onboard 24-bit Motorola DSP for mixing and monitoring, and headphone amp with volume control. Sample rates supported: 32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz. Supports full-duplex two-channel in, two-channel out operation. CardBus slot required. Analog input: Frequency response: 10Hz-20kHz, ?0.5dB. Dynamic range: >109dB (A-weighted). THD+noise, 1kHz sinewave at -3dBFS: <0.0014% (A-weighted). Crosstalk, 1kHz sinewave at -3dBFS: <0.0005% (A-weighted). Nominal input level: -10dBV (316mV). Maximum input level: +7.2dBu (1.775V). Input impedance: 10k ohms. Analog output: Frequency response: 10Hz-20kHz, ?0.5dB. Dynamic range: >109dB (A-weighted). THD+noise, 1kHz sinewave at -3dBFS: <0.0013% (A-weighted). Nominal output level: -10dBV (316mV). Maximum output level: +6.3dBu (1.6V).