Accuracy of measurements...

[Exocer]

I own the newer RS analog SPL meter and am getting excellent measurements with my Sealed Avalanche 15 sub. I wonder if they're too good to be true? Im dying to get a calibrated mic asap though... Here are some measurements.

Nearfield.

Listening position



What are some ways I can test for accuracy? The spl meter seems to have found the Tuning frequency of my Natalie P's to be 28hz (in-room) instead of my goal to tune them to 32hz...pretty close. My Velodyne DPS 10 looked like this before EQ


and after


Seems like the thing is working...but I cant believe the Avalanche is that flat in-room with no sort of EQ behind it.

[brucek]

What are some ways I can test for accuracy?

Well, when Sonnie and I were creating the calibration files for the three RS meters, measured against the ECM8000 that Sonnie had professionally calibrated, we overlayed our final responses using the cal files we had developed.

We felt that if we measured the same signal with the three different RS meters (using our newly generated cal files) against the ECM8000 and the responses were fairly close, then we'd be OK.

Here is a set of response graphs of the three types of RS meters using the cal files posted here at the Shack against the ECM 8000. We actually had two digitals at the time.


Here's the 10Hz to 150Hz graph....



Here we look a little closer from 10hz to 60Hz to check accuracy.




Here we separate the different graphs to get a closer look.... You see the ECM8000, an old analog, a new analog and two new digitsl using the new cal files......



They're close enough for me. Is that close enough for you?

brucek

[Sonnie]

Robert... that is remarkable response on your Avalanche 15.... awesome indeed with no eq at all.

I wouldn't think the meter would be more than a db or two different, but then again you could have gotten one with a bad capsule inside... only way to know for absolutely sure is to measure it against another SPL meter or a calibrated mic.

[Exocer]

Bruce, they're definitely close enough for me. I wonder about my particular SPL meter, not your calibration files...You guys have done a remarkable job

Sonnie, I guess that'd be the only way to know for sure huh?
I guess i'll be confident with the measurements i've got so far. At least they're not totally unbelievable like 120db at 10hz from a single sealed 15" sub.

[Sonnie]

You seem to do a lot of speaker projects that need measurement... I'd recommend the Behringer ECM8000, especially for full range. Go ahead and get it calibrated. Leonard has just sent his off to another fellow to compare calibration with our recommended guy... so you might wanna wait til he gets his back and lets see how close mine is first. If his is drastically different, I may end up getting my re-calibrated. Here we go again??? Maybe not!

[Exocer]

I'm hoping the measurements are close enough for satisfaction. Is there a thread about this? I am very interested in keeping track of this experiment

[Ilkka]

Without some heavy EQ/LLT, the near field response you show can't be accurate. It should start sloping much higher with around 12 dB/oct. slope. I recommend getting a calibrated mic (or at least non-calibrated ECM8000) and measure again.

Hi all, l'm wondering if would be able to steer me in the right direction here.......l have a newer analog rs meter and am wondering what allowances l will have to make with it just using it manaully c weighted for my sub.......any information would be appreciated........cheers ken

[brucek]

l have a newer analog rs meter and am wondering what allowances l will have to make with it just using it manaully c weighted for my sub

See here and download the Excel workbook for your specific meter and the compensation values are built into the file.

Or, you can download the XXXX.cal file from that page (which is just a text file) and use the values of meter compensation.

brucek

brucek wrote:

See here and download the Excel workbook for your specific meter and the compensation values are built into the file.

Or, you can download the XXXX.cal file from that page (which is just a text file) and use the values of meter compensation.

brucek

Thaks for that brucek
this means that my ib is down around 25db @10hz ( nearfield )...that sound about right??...cheers ken