Help Requested

[srossi]

I would like some help analyzing measurements of my audio system. I have enclosed the measurements at the LP for:

- Front SW only (Polk PSW 125)
- Rear SW only (Polk PSW 125)
- Front left main (Kitty Kat Revelator)
- Front Left main (Kitty Kat Revelator)

Sony STR-DG1000 Home theater receiver:
SW - yes
Front - Small
XO - 70Hz

Sub locations have been optimized (with in physical limitation).
Any help is appreciated

Thanks

 

[jtalden]

What specifically do you want help with?
What equipment are you using?

My thoughts regarding this setup:

• The noise floor is about 55 dB below the measurement level so It appears the test SPL was actually higher than the 60 dB shown on the chart. This suggests the microphone level calibration process was not done. This is not a problem as we are normally only interested in relative level differences for typical system setup analysis. Just be sure to test at SPL levels that seem to correspond to moderately loud listening levels. REW 'help' covers microphone SPL calibration process.
• The notes indicate a 70 Hz XO and small speaker settings, but the mains are relatively flat down to 35 Hz; the same as lower extension of the SWs. This suggests that the mains are actually set to large or there is another reason they are not rolling off at the intended 70 Hz XO. Some prefer to overlap the bass range like this if the mains are capable to provide the SPL and low distortion for the job. It's otherwise considered better to set the mains to small.
• The current timing between the 2 SWs could be improved.
• The timing of the SWs to the mains handoff could be improved.
• EQ for the bass range would be beneficial to smooth the bass response.

 

[John Mulcahy]

Why such large left hand IR window settings?

 

[srossi]

jtalden and Jm - thanks for you responses.

I do have a minidsp 2x4

- The measurements were not level calibrated. I do have a question about this however. The mic cal file I am using does have a microphone sensitivity figure that is not used. I have enclosed the cal file - there may be a file format problem.
- I doubled checked and the AVR front speakers are set to small with XO 70Hz
- any timing suggestions would be appreciated
- The large left handed IR window was an oversight. I changed it to 10 msec - no real change amplitude spectrum.

 

[jtalden]

- The measurements were not level calibrated. I do have a question about this however. The mic cal file I am using does have a microphone sensitivity figure that is not used. I have enclosed the cal file - there may be a file format problem.

It looked to me that you were using a XLR mic with a Focusrite interface. If so, we cannot use an imbedded mic sensitivity in the calibration file. An external SPL meter is used to set the REW SPL meter reading. The Focusrite input gain level is also manually adjusted to provide the desired headroom. See REW help instructions for an XLR type mic. There is no problem skipping this process so long as the actual test level is not too low or too loud. Any test level between 70 and 85 dB works okay for system setup.

- I doubled checked and the AVR front speakers are set to small with XO 70Hz

Okay. This is sometimes the case with main speakers that have strong low end SPL. The 12 dB/octave filter is not enough to rolloff the mains. The easy option is to allow this overlap so long as you are not concerned that the mains will distort or be damaged at your listening levels.

- any timing suggestions would be appreciated

I will work on Step 1 to suggest a favorable delay setting between the 2 SWs. The MiniDSP can be used to set a favorable delay for the closer SW.

Will an automated setup then be run in the AVR for speaker distance settings and EQ, or do you have a different plan?

 

[jtalden]

A delay increase of 2.5 ms for the rear SW in the DSP provides favorable SPL and phase tracking.