Acourate measurements and low IACC numbers

[JeroenD]

Hello,

 

I am using Acourate but not with much success.

When I create a log sweep I have the feeling the IACC values are rather low.

I have values like:

IACC10 = 49.2%

IACC20 = 35%

IACC80 = 31%

Also, after creating the filters, they stay low and almost don’t approve.

Also, I don’t hear much improvement using created filters.

So, I think something goes wrong or I am doing something wrong.

Or are these normal numbers for a dipole speaker system?

Any advice or hints?

 

I use a laptop in combination with Steinberg UR12 and Dayton Audio EMM-6 microphone. I use the Yamaha Steinberg USB ASIO driver.

I have a dedicated music room from 5m wide, 7,3m long and 2,5m high (in a basement).

The room is acoustically optimized with 24 big diffusers (180 cm tall) at the front and side wall behind the speakers, and diffusers behind the sofa at the back wall. Ceiling has damping and also side wall and back wall a little. Sofa is about 1,4m from the backwall.

Speakers are Magnepan MG 20.1 (modified), active crossover, Krell KSA-300S for the low panels and Audio Research VS115 for mid and ribbon. Pre-amp is Audio Research LS26 (upgraded) and DAC Holo audio May KTE. Streamer is a laptop for now (via USB), busy to build my own computer-based streamer with high quality components. Using ROON for playback.

[sledwards]

24 big diffusers? How did you arrive at such a large array of diffusion for that room size? Are they easily removed? Maybe just leave behind the speakers on front wall and take a measurement and post your before and after results? 

[ecwl]

Just noticed this from OP. I think the best person to ask is Uli, the author of Acourate in his Acourate User Group. There are simply too many possibilities for the low IAC but it probably is a measurement error? I don’t understand the comment about creating a log sweep. Are you using Strindberg UR12 as the output device to your preamp too? Or are you creating a log sweep file which you then play through your Holo DAC? Because the latter method would cause clock sync issues and lead to inaccurate measurements because your USB clock with the Holo may not be synced to the USB clock of the UR12. 

[Keith_W]

Hi JeroenD. I hope you have solved your issue by now. Basically, the IACC compares the output of the left speaker to the right. If the output that reaches the microphone is 100% the same between both channels, you get an IACC of 100%. Off the top of my head, here are a few reasons why your IACC might be off: 

- microphone not centred. 

- there is a problem with your speakers or electronics (make sure you check this first!), e.g. I had an output valve on my amp that was on the way out which I did not realize until I comprehensively checked. 

- speakers placed asymmetrically in the room

- strange room shape / one side has walls and the other has glass or bookcases, or open, etc.

- there is a problem with your correction filter

- you moved the microphone between taking measurements for the correction filter and taking the IACC measurement (if you repeat the measurement a few times with the microphone centered at various positions front to back, you will find the IACC will vary). 

 

There are probably a few more. But don't get too hung up about it, if it sounds right then ignore it.