Finally Tried REW, need suggestions regarding dealing with the findings

ebag4 · « **on:** 18 Aug 2011, 08:15 pm »

Gents,
I finally loaded REW and took some room measurements. I have been building and installing treatments over the past couple of years, some worked and others didn't but what I have now is the best I have had in my space. With that said I do have an overabundance of sub 60Hz bass, with Danny's assistance I have taken all of it I can out using the bass amp controls on the V1s. I will probably pick up a roll of insulation and move it around the room to see what that does but I thought I would also ask here to see what others might do to combat the issue. I have attached a couple of REW graphs as well as a room layout. Any recommendations are welcome.

BTW, someone asked so I thought I would post it here. The measurements were taken from the listening seat where the center of the back of my head would be. I listen nearfield, roughly a 6' equalteral triangle. The chair shown actually sits about a foot closer to the speakers than indicated on the sketch.

Best,
Ed

edit* I replaced the previous drawing with a more current drawing regarding seat and speaker locations.

I also have this type of treatment in all 4 corners (big improvement, thanks Dave!)

Bob in St. Louis · « **Reply #1 on:** 18 Aug 2011, 09:15 pm »

Remove the gnome Ed.
Problem solved......

Bob

InfernoSTi · « **Reply #2 on:** 18 Aug 2011, 09:18 pm »

Nice, Ed, way to go! Your setup looks flat as a pancake in most regards!

Would you mind posting a non-smoothed graph from 20-200Hz? That would give a little more resolution to the lower end. You may also want to take a look at your decay times....set that for 20-200Hz and 300ms. I also set the limits on my decay graphs following these steps (don't know if there is a better way but thought this seemed rational): first, I set the limits to 20-200Hz. Second, I set the SPL graph smoothing to 1/1 smoothing. This gives the closest to a flat line. I mark that with the mouse (let's say it's 85db). Third, I set the vertical limits to show 30db less than the 1/1 smoothing line (this would put the example at 85db -30db = 55db as the lower limit. Finally, I reset the upper limit to be higher than the highest peak by 10db (or whatever you like, maybe 30db above the average line would make sense too).

Oh, and someone wise told me that flat is flat but what sounds good to you is what sounds good to you (and the two may be different). A little bass boost is nice if you can manage the decay times!

Take care,
John

InfernoSTi · « **Reply #3 on:** 18 Aug 2011, 09:19 pm »

Quote from: Bob in St. Louis on 18 Aug 2011, 09:15 pm

Remove the gnome Ed.
Problem solved......

Bob

Um, I think he needs to add the belt....

Just say'n....

Bob in St. Louis · « **Reply #4 on:** 18 Aug 2011, 09:24 pm »

Quote from: InfernoSTi on 18 Aug 2011, 09:19 pm

Um, I think he needs to add the belt....

Just say'n....

ebag4 · « **Reply #5 on:** 18 Aug 2011, 09:29 pm »

Thanks guys.

Bob, that is a U of L Cardinal Gnome, he must stay!

John, seeing you work with REW is what finally got me to give it a shot. I have not gotten as far as you have with it so it will take me a bit to figure out how to do the measurments, with exception of the non smoothed graph, I will get that graph tomorrow.

Best,
Ed

ebag4 · « **Reply #6 on:** 18 Aug 2011, 09:29 pm »

Wrong forum guys, no one here knows about the infamous belt!

Best,
Ed

Bob in St. Louis · « **Reply #7 on:** 18 Aug 2011, 09:31 pm »

Sorry for the OT Ed, I couldn't resist.

Carry on gentlemen.

Bob

ebag4 · « **Reply #8 on:** 19 Aug 2011, 04:01 pm »

Quote from: Bob in St. Louis on 18 Aug 2011, 09:31 pm

Sorry for the OT Ed, I couldn't resist.
Carry on gentlemen.

Bob

No worries Bob, it's all in fun...this hobby is supposed to be fun, right?

Best,
Ed

bpape · « **Reply #9 on:** 19 Aug 2011, 04:09 pm »

What thickness is the absorption on the wall behind you?

The hump is very very broad suggesting it's not necessarily a room issue unless you have a lot of smoothing turned on in your graph.

Bryan

ebag4 · « **Reply #10 on:** 19 Aug 2011, 04:12 pm »

Quote from: bpape on 19 Aug 2011, 04:09 pm

What thickness is the absorption on the wall behind you?

The hump is very very broad suggesting it's not necessarily a room issue unless you have a lot of smoothing turned on in your graph.

Bryan

The smoothing is set to 1/6 octave, the absorbtion behind me is only 2" thick 8lb Rockwool. I will post an unsmoothed graph from 20 to 200 Hz here in a bit.

Best,
Ed

ebag4 · « **Reply #11 on:** 19 Aug 2011, 04:43 pm »

Here are the unsmoothed 15-200 Hz graphs, please note; theses are in 5dB increments:

Average of L&R readings:

Individual L&R Measurments

Best,
Ed

ebag4 · « **Reply #12 on:** 19 Aug 2011, 05:03 pm »

Quote from: InfernoSTi on 18 Aug 2011, 09:18 pm

Nice, Ed, way to go! Your setup looks flat as a pancake in most regards!

Would you mind posting a non-smoothed graph from 20-200Hz? That would give a little more resolution to the lower end. You may also want to take a look at your decay times....set that for 20-200Hz and 300ms. I also set the limits on my decay graphs following these steps (don't know if there is a better way but thought this seemed rational): first, I set the limits to 20-200Hz. Second, I set the SPL graph smoothing to 1/1 smoothing. This gives the closest to a flat line. I mark that with the mouse (let's say it's 85db). Third, I set the vertical limits to show 30db less than the 1/1 smoothing line (this would put the example at 85db -30db = 55db as the lower limit. Finally, I reset the upper limit to be higher than the highest peak by 10db (or whatever you like, maybe 30db above the average line would make sense too).

Oh, and someone wise told me that flat is flat but what sounds good to you is what sounds good to you (and the two may be different). A little bass boost is nice if you can manage the decay times!

Take care,
John

Hey John, let me know if this is not what you are looking for:

Left speaker

Right Speaker

Best,
Ed

ebag4 · « **Reply #13 on:** 19 Aug 2011, 05:19 pm »

Same as above but now with limits set. Sorry, the L&R graphs swapped colors between readings.

Left Speaker

Right Speaker

Best,
Ed

ebag4 · « **Reply #14 on:** 19 Aug 2011, 06:00 pm »

Decay plots 15-200 Hz. This REW is a really cool tool, now to learn to use it!
edit, the screen capture function seems to make these easier to read, graphs replaced. edit 2, noted large box between left spkr an wall was impacting the decay graph, remeasured with box removed and replaced graphs

Left Speaker

Right Speaker

Best,
Ed

JohnR · « **Reply #15 on:** 19 Aug 2011, 11:37 pm »

The servo amp has a parametric eq in it, doesn't it? How is it set?

ebag4 · « **Reply #16 on:** 20 Aug 2011, 12:11 am »

Quote from: JohnR on 19 Aug 2011, 11:37 pm

The servo amp has a parametric eq in it, doesn't it? How is it set?

John,
Yes, it has a parametric eq and I am using it.

Let me back up a moment and clarify something I wrote earlier. I stated that I had lowered the low end as much as I could, that is not completely accurate. I could lower the overall bass more however when I do 70-80 Hz develops a ever growing suckout.

The Parametric eq allows you to affect essentially 1 group of adjacent frequencies depending upon the frequency setting and the bandwidth setting. I had two issues, one was the peak centered around 43 Hz, the other was the suckout centered around 70 Hz. I tried correcting both and could positively impact each area individually but could not correct both simultaneously. In the end I preferred to correct the suckout around 70 Hz and let the sub 60 Hz signals ride high. The sound I am getting is excellent and I enjoy the extra bass so I am not too worried about the response as it stands, however I wouldn't mind hearing it flat, in my room it may not be in the cards, if that is true I am happy to live with it as it stands.

Best,
Ed

ebag4 · « **Reply #17 on:** 20 Aug 2011, 05:20 pm »

Here is a thread I posted on the GR Research circle regarding the changes I made to my system based on the REW measurments:

http://www.audiocircle.com/index.php?topic=97739.msg980468;topicseen#new

Best,
Ed

InfernoSTi · « **Reply #18 on:** 20 Aug 2011, 08:39 pm »

Ed,

Looking good (and sounding great, apparently)!

Thank you for posting the decay graphs. It looks like your "flat" line is about 67db (does that sound right?). If so, you may want to set the lower limit at 35db instead of 45db so you can see both the 20db and 30db decay rates. However, you have set this up so it sounds great (per your other post) with Danny's help, so that would just be for informative purposes, not to change anything. It would be interesting to know what your decay rates are based on this quote from Linkwitz:

"How much treatment is needed, or how short the reverberation time should be, depends on the polar radiation characteristics of the loudspeaker. For my open baffle speaker designs a room becomes too dead when its RT60 falls below 500 ms."

The <200ms specs are what we all read about seem to be great for home theater with surround sound. I don't entirely agree below 200Hz but it is an interesting theory. I'm still trying to figure out what I like best but think that lower decay times below 200Hz sound better and higher decay times above 200Hz aren't so bad (at least with my OB system).

John

ebag4 · « **Reply #19 on:** 20 Aug 2011, 08:46 pm »

Thanks John.

I have been down the too dead path, I had a faux wall full of 8lb rockwool, it sucked up all the sound. I ultimately tore it down.

I was going to attempt to absorb the low end by playing with a bale of fiberglass but I am so happy with the sound I have now I think I will leave it as is. I don't really have room for another trap anyway. Additional diffusion may happen at some point but I am in no hurry for it.

Best,
Ed