[BobC]

OK, so I downloaded Audio Tools RTA from Studio Six Digital to my iPhone.  I also purchased a Dayton Audio iMM-6 microphone.

I ran only my Martin Logan Ascent i's in stereo.  I have a Velodyne sub, but it was turned off.  My room is approximately 20'9" long x 13'9" wide x 8'8" high.  The rear wall is a bit irregular with a large opening into an adjacent room.  I have no room treatments.

Here's a pic...




Sitting in my sweet spot I ran the RTA using 1/3 octave pink noise.  Here is the graph.



OK, so to my untrained eyes this looks pretty flat through the mids and upper mids, but rolled off at about 200 hz down and 5k hz up.

OK, so now what?  I guess I was expecting some sort of peak that needed to be absorbed.  What kind of treatments should I be thinking of?

Any advice is appreciated. 

I may try to run it again but this time try to adjust the y axis dB scale to give a better look.

[BobC]

Here's another shot but with the 3 dB grid lines and adjusted Y axis.




I can turn on my sub to bring up the low end to a point.  Not sure what to do about the highs rolling off.

I notice a +/- 4 to 5 DB between 250 up to 5 before it starts to drop.

So what do you think?  I was going to try diy  absorption panels in corners and 1st reflection points.  Then re measure to see the differences.

Thoughts?

[a.wayne]

Was there a mic file or app you had to load for the mic ..?


Move the mic across Your listening position plane  , Fl, L, C,R,FR  for example, you want an avg  if you want to adjust , the high frequency roll off is not that abnormal for RTA's  mic position and proximty are very critical for frequencies  above 10K and turn on your subs, so we can see the full system , obvious where ML get their thin sound from ....


Regards

[BobC]

Nope just stuck the mic into my iPhone and used the audio tools RTA.  Simply held the mic at my listening position.  I did not walk around the room.  I'm not sure if the app allows me to average multiple readings.

[Carl V]

I guess the first question is "how does it sound to you?"

1/3 octave RTA is a step in the right direction.
it is however going to cover up many of the irregularities
we all have to some extent. Better software or techniques
will inform better. Again it's really up to the individual to
decide if that elephant in the room is objectionable.

And  Full Freq spectrum curve may help you along your way.

[a.wayne]

Nope just stuck the mic into my iPhone and used the audio tools RTA.  Simply held the mic at my listening position.  I did not walk around the room.  I'm not sure if the app allows me to average multiple readings.

Best to avg across, you can compare curves, chk if an app is necessary for that mic....?

[BobC]

Best to avg across, you can compare curves, chk if an app is necessary for that mic....?

Thx I'll look into it.

[BobC]

I guess the first question is "how does it sound to you?"

1/3 octave RTA is a step in the right direction.
it is however going to cover up many of the irregularities
we all have to some extent. Better software or techniques
will inform better. Again it's really up to the individual to
decide if that elephant in the room is objectionable.

And  Full Freq spectrum curve may help you along your way.

Yeah, I don't want to spend big $$$ on software.  The app was only $10, so I understand it has limitations.  Really my system sounds pretty darn good to me, but I am a believer that all rooms will benefit from some treatment....so I'm planning to make some DIY absorption panels and see if I can hear or read a difference.  Really hoping the RTA will show me some sort of improvement which correlates with my perceived sonic improvement....then I can use it to play with panel location, etc.

I'm interested to know (from those with experience here) if my graph "looks pretty good" or has some apparent opportunities....and what treatment suggestions people may have to smooth things out.  My initial plan is to fab and install panels in corners and 1st reflection points.  Probably another set of panels right behind the panels as well....but this is pretty close to the corner anyway.

[Hipper]

I don't think that graph looks that good. You seem to have lost a lot of bass from 250Hz downwards and a lot of treble from 6kHz upwards. However that could be a limitation of the software, the microphone or your microphone positioning, or not using your sub. I suggest you redo the measurements when using the sub as this is about trying to find what you are hearing at your chair.

I see two ways forward for you to improve your confidence in your measurements. Firstly you could use test tones and your ears to work out what you are missing. I see you are aged 42 so you will have lost some of your higher frequency hearing, perhaps down to 16 or 14kHz (I'm 61 and can't hear above 10kHz). Sit in your chair, play a 1kHz test tone to a comfortable listening level, then with that same level play the other test tones and grade them louder or softer then the 1kHz tone. It's not very accurate of course but it should show up the problems that your RTA measurements have if they exist. For a free test tone download from 10-300Hz in 1Hz increments go here:

http://realtraps.com/test-cd.htm

I suggest you just use 10Hz increments to start with. It's possible there are free full range test tone downloads available, or you can buy them from the likes of Stereophile or Chesky.

The second is to use a free software called REW - Room EQ Wizard:

http://www.roomeqwizard.com/

However you will probably need to buy other bits and pieces and it is complicated to use. It will though give you much more accurate measurements allowing you, if you wish, to wisely invest in room acoustic material or/and adjust speaker and listening position for better results. REW will not only give you a frequency response but a waterfall plot, which tells you about how long the sound takes to subside, and other pretty sophisticated plots. The investment in time to learn it will pay dividends in the long run.

If you find the measurements are not to your liking you can do a few things, but don't get too hung up on them. Your ears must be the final arbiter of whether it sounds good, not measurements. Measurements are just a tool to help.

You can invest in room acoustic treatment. There's plenty of advice around, on the Real Trap site above, and on the GIK site:

http://www.gikacoustics.com/

GIK have a Circle on here. I have used their advisory service and their products which I recommend. Bass traps are the number one consideration.

You can spend time trying different speaker and listening positions. One source of advise:

http://www.barrydiamentaudio.com/monitoring.htm

I tried 'The Thirds' but am now using 'The Fifths', more or less. To get an idea of what positioning could, play something then walking towards and away from the speakers, listening particularly to bass.

You can also use an equaliser.

I've done all three. Using REW I tried to find the best positioning, then added room treatment, and finally used REW to get measurements for my equaliser to make finer adjustments. Finally I used my ears and test tones to make my final inputs. I aimed for a flat frequency response but it doesn't measure exactly that because my ears and brain do not behave like a microphone.

[BobC]

Thank you, Hipper.

[Tyson]

OK, so I downloaded Audio Tools RTA from Studio Six Digital to my iPhone.  I also purchased a Dayton Audio iMM-6 microphone.

I ran only my Martin Logan Ascent i's in stereo.  I have a Velodyne sub, but it was turned off.  My room is approximately 20'9" long x 13'9" wide x 8'8" high.  The rear wall is a bit irregular with a large opening into an adjacent room.  I have no room treatments.

Here's a pic...




Sitting in my sweet spot I ran the RTA using 1/3 octave pink noise.  Here is the graph.



OK, so to my untrained eyes this looks pretty flat through the mids and upper mids, but rolled off at about 200 hz down and 5k hz up.

OK, so now what?  I guess I was expecting some sort of peak that needed to be absorbed.  What kind of treatments should I be thinking of?

Any advice is appreciated. 

I may try to run it again but this time try to adjust the y axis dB scale to give a better look.

I have the same app - it is grossly inaccurate.  You are much better off getting the USB Mic from Parts Express and using that - otherwise you'll end up making the wrong corrections.  It'll be the best $75 you'll ever spend - http://www.parts-express.com/dayton-audio-umm-6-usb-measurement-microphone--390-808

[JRace]

Can you change from dBA weighted to
dBC weighted?

Also if possible just look at 200Hz down,

And did you load the calibration file for your mic?

[BobC]

Calibration file?  Um, no.  Guess that would be a good place to start.  I'll look into that.  Thanks!

[Glenn Kuras]

Yeah, I don't want to spend big $$$ on software.  The app was only $10, so I understand it has limitations.  Really my system sounds pretty darn good to me, but I am a believer that all rooms will benefit from some treatment....so I'm planning to make some DIY absorption panels and see if I can hear or read a difference.  Really hoping the RTA will show me some sort of improvement which correlates with my perceived sonic improvement....then I can use it to play with panel location, etc.

I'm interested to know (from those with experience here) if my graph "looks pretty good" or has some apparent opportunities....and what treatment suggestions people may have to smooth things out.  My initial plan is to fab and install panels in corners and 1st reflection points.  Probably another set of panels right behind the panels as well....but this is pretty close to the corner anyway.

1/3rd really is not going to tell you much and really you want to look at the decay times. That is where the punch/tight low end comes in. You can use REW which is free and give you all the info you need and MORE! See the following.
http://www.gikacoustics.com/room-eq-wizard-tutorial/

[BobC]

OK, so I took the advice offered.....and returned the iPhone mic.  I bought a Dayton Audio UMM-6 USB mic and ran it into REW.

Following mic calibration (I didn't calibrate the sound card because my LT doesn't have a line in) I ran the test signal.  Here are the graphs.




Perhaps someone can explain the black line below the SPL curve?  Also, I don't understand the degree axis to the right.

In general things look pretty choppy.

Also, here is the waterfall.



Please educate me.  It looks like most frequencies above 100 hz decay in < 240ms.  Is this good?

I'd appreciate any treatment suggestions as I plan my room.  I'm thinking DIY absorption panels at the usual spots,  but I can build diffusion as well.

Thanks, Bob

 

[Hipper]

Firstly could you print images of just the 20-500Hz range. You can do this by using the 'Limits' icon top right. For the frequency response, please use 'no smoothing'. Do this on the 'Controls' icon.

The black line may be your mic calibration. You can unclick it at the bottom of the page. You may be on the 'SPL & Phase' page. If you look at the tabs on top of the graph click on 'SPL' tab.

The degrees you see are for the phase. You don't get them on the SPL graph.

Another interesting image is the 'Spectogram'. Where the 'SPL' tab is go along to the right and click the double arrow, then 'Spectogram'. This can help determine if any sound was heard before the REW signal was played, which means it's from traffic or other noise.

[BobC]

As suggested....








The furnace was running in an adjacent room, but of course there are registers in my theater.  I guess that may be the "red" blob of noise at around 90hz?

[BobC]

with smoothing removed...

[Hipper]

You've shown me yours so I'll show you mine!



This is from my right speaker and it is to the same scale as yours to form a good comparison. Apart from an adjustment at around 40Hz this is how I listen today.

Your frequency response isn't that bad really. The narrow deep dips are very difficult to sort out and may not effect the sound much anyway. The problems may be the peaks at 40Hz and particularly the broad hump at 83Hz. Moving speakers/ listening position around will change the response but may make it worse or better. Worth trying though.

Overall, including your full range 1/12 smoothing image, it looks to me pretty good.



This is my spectrogram from the same measurement. On mine you can see traffic noise from 30-80Hz - it's making noise before the measurement signal is made. I don't hear this noise which is an illustration of how microphones and our ears do not behave the same. For this reason I could not trust the microphone measurements below 50Hz. Apart from the traffic noise I think mine looks good because the decay times of all frequencies appear to be very similar. Your decay times are less even. That could be because I have quite a bit of room treatment.

The furnace may be all the noise below 20Hz and also the noise that continues after the signal has gone. The red is the loudness of the sound and is the peak at 83Hz.

On your waterfall plot the decay times of 240ms is pretty reasonable. I believe 200ms is said to be good for music rooms. On my one you can see the traffic noise

[BobC]

So here is what I'm thinking of building.  DIY 2'x4'x4" OC 703 panels behind the speakers and at 1st and 2nd reflection points.  Some sort of DIY bass tubes in the front corners.  I've got a cabinet with glass doors and a treadmill in the back corners.  I cant really put base tubes back there, but could hang a few panels at the treadmill as it gets "boomy" back there while running.

What do you all think?  Should I consider angled panels in the front corners instead of tubes?  Should I consider panels hung from the ceiling at 1st reflection point?  What about diffusion?

Of course, I still need to convince my wife on all of this!