A lot of ripple to my measurements...why?

[Dirk]

Short sine sweep, 1/24th oct, gated or not, I end up with ripples like these in my measurements. In the case of the mid (TC9), it definitely occurred at even octaves. Why do they occur? My fault?

(looking specifically from 1khz and up; I understand below that is garbage)

[dcibel]

Re: A lot of ripple to my measurements...why?

That looks like textbook reflections. Can you post a screenshot that shows the impulse and gate ?

[Dirk]

Re: A lot of ripple to my measurements...why?

Could very well be. I'm going to measure again, with a closer mic and a different amp just in case. This was the left channel of my AVR. Pretty sure all DSP was disabled, but I'll try my 1st gen AudioSource Amp Three. I'll be sure to capture the impulse this time. Gate was around 5ms.

Also, if they are reflections (which is possible, the tweeter has a very big and wonky face plate and I left it surface-mounted), they should move as I measure off-axis, right?

[Dirk]

Re: A lot of ripple to my measurements...why?

CASE CLOSED

dB, ya nailed it. Close mic measurements were ruler flat, even at 1/96th octave. Also, when measuring at 1m, I could move the reflections by moving the mic off-axis.

[dcibel]

Re: A lot of ripple to my measurements...why?

Glad I could help.

For far field measurements you don't necessarily need to be at 1m. 3 to 5 times the driver diameter is sufficient, the closer the mic is the less reflections will make it into your measurement. Just be sure to observe the impulse and set your gate accordingly.

The "mic height" spreadsheet available here can help you calculate floor bounce based on mic and speaker location:

http://audio.claub.net/software.html