The correct way to check the frequency response.

Hi I am new to this. I am trying to setup my HT with multi way speakers and sub. So I figure I should do a SPL chart to make sure the frequency response is on par.

I used an app on my phone Galaxy S4 and capture a chart. The app is audioTool

Is that the correct way to go about it or is there another better way?



Sappy

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To Err is human. No wonder tube amp sounds better.
 

eriksquires

Member
2013-05-10 4:11 pm
Hi Sappy!

If you want to get accurate subwoofer and satellite readings consider the $12 iMM-6 calibrated microphone. It's at least very good for setting up relative volume's for your sub and satellite speakers. That's usually how I calibrate my Oppo BluRay player's settings. I route the output to a 7.1 channel preamplifier. Your phone's microphone is unlikely to have a good enough range to calibrate your sub properly.

That microphone also works well with desktop apps with the right software, which often means Room EQ Wizard.

I'm no expert with AudioTools, and I've not used the frequency generator, but if possible, use the impulse instead of steady state/noise for accurate measurements. The iMM-6 lets you use your normal phone stereo outputs at the same time as the microphone. It will be interesting to see what you find. :)

Personally I use OmniMic for anything more than just SPL matching, but then I build speakers so I found the expense really easy to swallow for the features + microphone that came with it.

Lastly, almost all subwoofers need EQ to integrate well. The dips and peaks in response in most rooms are huge and overwhelm everything else. Flatten out your sub and you can get much more and deeper bass. Lots has been written on the subject. Personally I use the output from OmniMic to feed a miniDSP unit, in addition to a pair of GIK Acoustics Soffit traps but you can do the same with Room EQ Wizard. The bass traps are enabling technology which makes DSP / EQ worthwhile. These are all features that most modern receivers come with however.

Regardless of how you do EQ, bass traps are essential for the best sound.

Best,


Erik
 
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eriksquires

Member
2013-05-10 4:11 pm
Hi Bchiu,

Basically, if you get low enough in frequency rooms ring like a big bell at modal frequencies. That is, instead of a very even, flat response like you might have outdoors or in an echo-less chamber, certain very narrow frequencies will have severe peaks, the equivalent of 20x the power output at those peaks than at other frequencies. You also get nulls, severe dips that cut the effective power by 20x or more, and these peaks and valleys are very dependent on seating position.

Bass traps de-energize those modal nodes. They reduce the effects of the peaks and the valleys and enable a DSP/room correction/EQ setup to finish the job. I have done demonstrations in my home with 2-way speakers, and you can totally hear the mud in the bass leave and the speakers appear to add an octave to the bass response when the bass traps come back into the room. The effect is just as good with the subwoofer. The best way to add lots of bass is to control the room first. Then you'll be amazed how good and deep a 6-7" woofer will go, and how much better and louder you can play your sub.

Bass in addition to moderating the peaks and nulls bass traps also reduce the effects of seating positions and speaker placement.

The best order is to get basss traps first and then use room correction/DSP/EQ. In the absence of anything else room correction is still better than nothing however.

MiniDSP si not a closed loop at all. :) You are thinking very advanced stuff like what Meyers does in concert halls. They actually can adjust EQ curves from the music as people start filling up the halls. Very very cool stuff, and total overkill in a home.

With a home system you measure multiple locations, get an average, and then create compensating EQ curves. What IS real time about miniDSP is that you can upload your changes dynamically from your PC.

Best,


Erik
 
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