Some plots of my room - crude first-timer stuff!

Big Red Machine · « **on:** 26 Oct 2011, 12:47 am »

I want to see the left, right, and combined sweeps all at once but I cannot get anything beyond the first set of data to import.

Clues?

Big Red Machine · « **Reply #1 on:** 26 Oct 2011, 01:01 am »

Doh! Got it.

DO you guys apply any Smoothing Octaves to your data?

JohnR · « **Reply #2 on:** 26 Oct 2011, 01:06 am »

It depends on what you are wanting to do. Generally, for full range in-room response, 1/3 or 1/6 octave smoothing. For bass frequencies, no smoothing.

poseidonsvoice · « **Reply #3 on:** 26 Oct 2011, 01:11 am »

BRM,
I do not smooth below 250 hz (the Schroeder frequency in most rooms). I smooth 1/6th octave above that. However, others disagree. Some will smooth the whole enchilada 1/3rd octave which makes the curves look glorious and is great for marketing. Others argue that our ears most closely approximate a 1/3rd octave smoothed FR curve. However, there is evidence that 1/6th octave smoothing above 200 -250hz is what the ear 'hears.' Below 250Hz however, I want to see the response completely raw so I can correct for deficiencies by moving the subs, adjusting the phase, crossover points, etc...

Of course this is all just one aspect of measuring. You should also be looking at waterfall plots up to 300msec in the time domain. There is lots of great info to read, especially at Hifizine (Paul Spencer's latest article) and most recently Nyal Mellor & Jeff Hedback have a recent pdf whose link is on the Audio Industry discussion circle with an introductory info/guide on some goals for 2 channel reproduction (i.e. by no means is it exhaustive - you'll need to read a lot more papers/books for that!) .

Best,
Anand.

Big Red Machine · « **Reply #4 on:** 26 Oct 2011, 01:13 am »

Okay. Here is a rude and crude run with the RS meter, no smoothing. This is the Measured tab where I can see all 3 plotted. Big suck-out at 70 and the other abnormalities seem to balance each other out when you run both channels at once. Weird.

I only measured out to about 2000 give or take so far.

Blue is both, red is left, green is right.

Big Red Machine · « **Reply #5 on:** 26 Oct 2011, 01:14 am »

I have zero clue how to get a waterfall to graph itself let alone understand it.

jtwrace · « **Reply #6 on:** 26 Oct 2011, 01:16 am »

Also make your "Y" scaling to 5dB incrememts. Have fun!

Big Red Machine · « **Reply #7 on:** 26 Oct 2011, 01:20 am »

Quote from: jtwrace on 26 Oct 2011, 01:16 am

Also make your "Y" scaling to 5dB incrememts. Have fun!

But then it looks like crap!!

JohnR · « **Reply #8 on:** 26 Oct 2011, 01:22 am »

I find it helpful to set the scale to a total of 40 dB. 100 dB looks good but it's not very easy to read.

To get a waterfall, go to the main screen and select the measurement you want to get a waterfall of. Click on Waterfall along the top, then Generate near the lower left. See http://www.hifizine.com/2011/06/bass-integration-guide-part-1/ for recommended settings.

Big Red Machine · « **Reply #9 on:** 26 Oct 2011, 01:30 am »

I can't generate one. I believe it is because I am importing the data using txt files and not electronically?

JohnR · « **Reply #10 on:** 26 Oct 2011, 01:49 am »

Oh, perhaps so. I think I ran into that once before.

HAL · « **Reply #11 on:** 26 Oct 2011, 02:15 am »

Pete,
Do you have an 8' ceiling in the room? If so, that might be causing the 70Hz dip.

Big Red Machine · « **Reply #12 on:** 26 Oct 2011, 10:00 am »

Quote from: HAL on 26 Oct 2011, 02:15 am

Pete,
Do you have an 8' ceiling in the room? If so, that might be causing the 70Hz dip.

Essentially. I have to calculate the expected room modes based on 13.5 wide, ~8 high, and either 20 long or 17ish long (alcove)

ratso · « **Reply #13 on:** 26 Oct 2011, 01:14 pm »

Quote from: Big Red Machine on 26 Oct 2011, 01:14 am

I have zero clue how to get a waterfall to graph itself let alone understand it.

hope someone picks up on this. i have found some bits and pieces online, but have yet to find a really good primer on how to interpret waterfall graphs. if anyone ever had the time and enjoys doing this sort of thing a "how to read graphs" thread would be really helpful.

poseidonsvoice · « **Reply #14 on:** 26 Oct 2011, 01:31 pm »

Quote from: ratso on 26 Oct 2011, 01:14 pm

hope someone picks up on this. i have found some bits and pieces online, but have yet to find a really good primer on how to interpret waterfall graphs. if anyone ever had the time and enjoys doing this sort of thing a "how to read graphs" thread would be really helpful.

Have you already looked here?

Anand.

ratso · « **Reply #15 on:** 26 Oct 2011, 01:53 pm »

thanx anand, i have seen that one and i think it is about the best tutorial i have found.

Big Red Machine · « **Reply #16 on:** 4 Nov 2011, 01:01 am »

I bought a Boehrenger UCA202 soundcard and I think I have it set up correctly.

Some sweeps of the left and right channels independently done and averaged and a waterfall of the two overlayed.

Assuming they are reasonably accurate, what the heck do I do now?

Big Red Machine · « **Reply #17 on:** 6 Nov 2011, 05:37 pm »

I bought a Behringer XENYX 802 Mixer 8-Input 2-Bus and Dayton Audio EMM-6 Electret Measurement Microphone and have more accuracy now.

The Home Theater Shack folks recommended I overlay a low freq run at 1/48 smoothing on the full range at 1/3 smoothing.

Big Red Machine · « **Reply #18 on:** 6 Nov 2011, 05:41 pm »

Regalma · « **Reply #19 on:** 8 Nov 2011, 12:31 am »

Jim Smith in his book Get Better Sound states without equivocation not to locate the equipment between the speakers. I moved mine and can't really say it made a difference. But it takes so long to change a setup to that extent that it is hard to say how much of a difference it makes. He also said to remove any table between the listener and the system. I moved my coffee table and what difference that made.