[ACHiPo]

My trap material arrived: 3 cases of 703 and 1 case of 705.  I have 2 cases standing vertically in the front corners, one lying horizontally as a coffee table, and one in the back corner.  I've taken some measurements since they arrived and I placed them, but I don't see any big difference in bass response. 

It seems like they would act as bass traps even while still in the cardboard boxes, no?  The lack of change that I can measure or hear has me doubting my strategy.  Any suggestions/comments would be appreciated.

[Glenn Kuras]

It seems like they would act as bass traps even while still in the cardboard boxes, no?

Basically yes but keep in mind that 705 is good up to around 6" or so while the 703 you can get a bit deeper. I would recommend you take them out of the boxes, make them 6" deep and straddle corners. That is going to give you the largest bang for the dollar. Keep you eye on the waterfall graph. That is where most of the change should come in.

[ACHiPo]

Keep you eye on the waterfall graph. That is where most of the change should come in.

Glenn,
Thanks.  I plan on getting them out of the box, but straddling corners is not in the cards, rather soffit traps along the front wall/floor interface in the lower cabinets, and a tall, thin absorber at the first reflection points.  And a bass trap in the ceiling above the electronics in the closet.  It's a compromise.  I was just surprised not to see/hear more difference, as the first treatments had a pretty big effect.

I need to figure out a better method of getting a waterfall as the port on my iPad is getting flaky.

Evan

[Glenn Kuras]

Soffit style is GREAT!! I think the 703 though might be a bit to dense. I would use something along these lines.
http://www.gikacoustics.com/product/knauf-rigid-fiberglass-1-6-lb/

[ACHiPo]

Update:  After giving up on measurements for a while given the confusing results I was getting with the calibrated condenser mic, Scarlett 2i2 USB preamp, and REW, I finally spent the time to sort out the issues and got it working.




At least I'm getting somewhere.  Now that I've got believable measurements I'm going to pull all of the easily removable acoustic treatments out this weekend to get a baseline and quantify the effects.

[Glenn Kuras]

Your frequency response is not looking all that bad. You also want to view the waterfall to view decay times.

[ACHiPo]

Glenn,
I've looked at waterfalls and they're worse (longer) decays than I saw on StudioSix, but the cursory look didn't seem all that bad (down ~30 dB within ~300 ms below 300 Hz). 

Now that I know I can get real measurements that correspond to what I hear, I need to figure out a measurement plan so I can start analyzing in earnest.

Thanks,
Evan

[ACHiPo]

A rather productive if confusing morning.  I took about 40 waterfall measurements with REW, most with all but the semi-permanent acoustic treatments removed.

Here is the baseline measurement for the listening position. 

Listening position, no treatments


Listening position, MT and soffit traps installed--they don't seem to do much...




Listening position with 2 monster traps and 4" DIY 703 + mass-loaded vinyl trap stacked vertically behind listening position.  Now we're getting somewhere, but it took 18" of high density fiberglass plus mass loaded vinyl, and the effect is only local.

[ACHiPo]

In case you're wondering what it looks like to have enough trapping to tame the modes behind the listening position...



Definitely not an attractive option, and I don't even need to worry about WAF.  I'm hoping putting a 2' x 4' x 14" trap in the ceiling of the closet with have an equal or greater effect.  I also will be adding a 4' x 20" x 10" trap in the front bottom right corner to match the one in the front bottom left corner.

The tall DIY panel I built to straddle the right rear corner, and I'm surprised at how little effect it has on the room when in that location.

[mresseguie]

Could the wood paneling on the walls be causing some of your sound quality issues? Could they be too reflective and not absorbent enough?

Have you tried placing some potted plants in the room to see if they aid with diffraction? (Perhaps I'm reaching for straws here...)

[ACHiPo]

Could the wood paneling on the walls be causing some of your sound quality issues? Could they be too reflective and not absorbent enough?

Have you tried placing some potted plants in the room to see if they aid with diffraction? (Perhaps I'm reaching for straws here...)

I'm sure the paneling adds and takes away, but it's staying as I like the feel.  Actually the room sounds darned good--the best set up I've ever had-- I'm just experimenting to try to understand acoustics better and see if I can't really make the room sing. 

I finished the 20" x 48" x 10" trap on the right lower corner and a mondo 24" x 48" x 10" trap with 4 sheets of 703 and topped with 1 sheet of 705FRG (reflective side out).  I'll try to get some more measurements in the next few days and post progress.

Once I either get the bass under control or run out of fiberglass I'll start moving speakers around and look at tuning the upper registers, imaging, etc.

Thanks to everyone for their input.  Keep it coming!

Thanks,
AC

[Glenn Kuras]

Actually the room sounds darned good--the best set up I've ever had--

I bet it does!!! Great job

[ACHiPo]

Got a chance to take a few measurements last night with the two additional traps in place and things look to be getting better.  Each measurement is the average of two full-frequency sweeps.  Note that there is no smoothing on these, so the frequency response graph in particular is pretty ugly.  I'd appreciate recommendations on the best way to look at both the waterfall and frequency response curves. 

The waterfall definitely seems to be improving with the two additional traps, and looks about as good as the case with 16" of traps behind the listening position.  There's still a pretty big null at 47 Hz.



The frequency response graph is interesting.  Again I'm primarily looking at <300 Hz at this point, but there's a huge null at 890 Hz.  I don't hear this null, and I think I would if it was really there and as big as it shows up.  Could it be an artifact, or do I really have that big of a suck out?  Interesting differences between L (blue) and R (Gold) speaker responses, which made me want to investigate BRM's suggestion to move the speakers a bit.

[ACHiPo]

Moving the speakers definitely had an effect.  More optimization is necessary, but I can definitely modulate the 47 Hz null with speaker placement.  Moving the speakers closer to the listening position and narrower didn't do mucn...


...but keeping them about 3" narrower on either side (6" total) and moving them back 10" (9'1" from the listening position as measured with a laser) from the original position had a pretty big effect.



The frequency response also looks smoother, at least in the bass.  I still see the huge null at 890 Hz, but I'm making progress.



Now with a few subs to flesh out the lower registers I should have pretty smooth bass.

[ACHiPo]

I did one more test this morning.  Using the sine wave signal generator, I swept the frequency slowly from 800 Hz to 1000 Hz.  While I can hear some variation in level in that range, the signal does not disappear as I'd expect if there was really a 40 Hz null at 890 Hz, so at this point I'm writing that off to a measurement artifact.

[Glenn Kuras]

I did one more test this morning.  Using the sine wave signal generator, I swept the frequency slowly from 800 Hz to 1000 Hz.  While I can hear some variation in level in that range, the signal does not disappear as I'd expect if there was really a 40 Hz null at 890 Hz, so at this point I'm writing that off to a measurement artifact.

Just from looking at the graphs I really thick you are right about the artfact.

[ACHiPo]

Just from looking at the graphs I really thick you are right about the artfact.

Thanks Glenn.  I've been listening rather than measuring and it sounds pretty darned good.  Going to get the electronics moved in a few weeks, then hopefully finalize my acoustic treatments and call it good.