[Big Red Machine]

Thanks murphy, you prompted me to run a sweep or two.  I have a little clipping going on and need to resolve.  In the meantime, I have these.  What do you think?  I feel like the waterfall is too thick front to back which means too much reverberation?  And I never know what the heck the RT60 tells me.  I plotted the sweep at 1/6.  What is more "honest" ratio to use?

[Big Red Machine]

1/24th version

[JohnR]

The waterfall would probably be more informative if plotted with a log scale I'm wondering what's going on at 6k +/-, both the T30 and waterfall show a long delay time there. Is it in the Decay plot too? It doesn't seem right.

[murphy11]

The waterfall would probably be more informative if plotted with a log scale I'm wondering what's going on at 6k +/-, both the T30 and waterfall show a long delay time there. Is it in the Decay plot too? It doesn't seem right.

First BRM, thx for posting your plots. Really helps me as someone new to measuring compare my plots to other rooms/systems. Are your plots showing a mono REW signal being played through both speakers? Not sure what we are looking at and the proper way to capture plots for analysis.

JohnR, is your feedback about 6K based on the peak at 6K shown in the waterfall and the vertical spike in RT60?  Does a vertical spike in RT60 mean ringing\bad decay and in general would a person want to see a flat RT60 or a plot like downward stairs?  I'm not sure how to imterpret RT60 and waterfall - do they show basically the same thing in different format? Hopefully this is not off topic.

[Big Red Machine]

I have the waterfall at 800 ms trying to see where it drops off.  You can see a long decay on these revised views of the same data within the 800ms window about the duration of the decay plot which is on a smaller scale.  I have a preponderance of diffusion in the room, so that might be the culprit.  I have Near Diffusers from Real Traps at the first reflection points and more Gik diffusers on the side walls as well.

[Hipper]

For comparison here's my SPL (1/24 smoothing), waterfall and spectrogram for my right speaker:










The spectrogram clearly shows that at 30-50Hz and at 80Hz the noise is heard before the REW signal is made - the signal is made around zero seconds yet there is noise before that in the minus milliseconds. This noise continues so it is not easy to know how the REW signal decays in this region. This is external noise from traffic. You can also see this on the waterfall plot. I made a measurement on Christmas Day and I didn't get this response.

It's odd that your spectrogram has noise all the way through the frequencies before the REW signal. I don't know what that means unless you have some background noise going on. You can find out by measuring with your microphone without playing the REW signal.

My waterfall plot has a range of 37dB above the noise floor. Yours seems to have about 28dB (a rough average of the lowest dBs (60dB) taken from a rough average of the highest dBs 88dB)). I was told that waterfall plots are not much use above around 500Hz.

For the 1/24 SPL reading you could use the 'control' button on REW to adjust the scale, say to between 75 and 90dB and 20Hz to 20,000Hz. It won't look so smooth but will be more informative. Yours seems to have a range of around 11dB which seems pretty good in comparison with mine of about 17dB excluding the traffic noise.

[Big Red Machine]

I have a tone of noise, both ambient and electrical going on.  Furnace, space heater, refrigerator, and some lousy cables I should swap out for this test.

I crudely covered up the diffusors on the side walls with 2 inch thick 703. You can see how the decay in the upper registers, where 2 inches is going to be effective, eliminates the ringing after 1500 hz. I don't particularly like the resultant sweep with the 703 but I will give it a listen to see how I like it.

For those wanting to believe in bass trapping, you can see that I essentially have none, and that is true, and the waterfall shows that. Also, you can see how simple 2 inch 703 material can eliminate upper frequency long delay times.

[Big Red Machine]

I found the biggest electrical noisemaker was the laptop power supply. Unplugging that makes it mucho better.

[Big Red Machine]

Here are independent right and left measurements overlayed.

[Hipper]

I would say that the waterfall plot in post 6 illustrates the need for bass traps. Some of the 'ringing' of the lower frequencies may be noise but could also be your room and its effect on the bass sounds.

If bass keeps ringing it muddies the whole sound. When I got bass trapping right I actually heard more bass because I was hearing what was in the music and not what my room allowed me to hear. It also opens up the rest of the music. It really is a very pleasing improvement which you don't appreciate until you hear it.

If you need proof first, I can think of two ways. First is to listen to material you are familiar with in your room, and then a well treated room. Most of the difference you will hear will be the room, not the gear. Alternatively, you could use certain tracks that have known bass responses. Jim Smith in his book Get Better Sound describes in some detail how he uses tracks from 'Tears of Stone' be The Chieftains to 'voice' systems and I found that quite useful.

I urge you to consider some form of bass trapping if you want to get the best out of your set up. As the experts will tell you, no room defies the laws of physics, not even yours!

[Glenn Kuras]

Note how the waterfall drops off fast but then picks up and and keeps on doing. That is not the room. I think it is how you have the program set up, IMHO.  Check your setting and how you are set up.

[Big Red Machine]

Note how the waterfall drops off fast but then picks up and and keeps on doing. That is not the room. I think it is how you have the program set up, IMHO.  Check your setting and how you are set up.

Yeah, I have noise issues with the mic and setup.  I can't seem to get the mic and speaker volume relationship right.