Comparing "sealed", hollow, insulation tubes to stuffed insulation tubes

TRADERXFAN · « **Reply #20 on:** 19 Oct 2009, 08:28 pm »

I would like to be able to put in more of the traps, but I can't justify the expense for the experiment. I already have a crapload of 8# mineral wool panels of 2"/4"/6" thickness (and quite a bit of it sits unused in my garage

) And I still need to need to buy loose insulation to drop in these tubes, for the filled test.

Now if the results are very promising, then maybe I will get more and do another round.

Also, I have another design option that I am going to work on.

Good thing there is a break in the cold, so I don't mind working in the garage...

-Tony

bpape · « **Reply #21 on:** 19 Oct 2009, 08:43 pm »

Sounds like a good addition to the experiment. Try wrapping 6" of mineral wool straddling a corner and use that as another data point. Nice of me to make more work for you, huh

Bryan

TRADERXFAN · « **Reply #22 on:** 19 Oct 2009, 08:45 pm »

Yeah, I will put the mineral wool in the mix. But what do you mean by "wrapping" it? Like a covering? I have it in just panel form, in a readybag...

bpape · « **Reply #23 on:** 19 Oct 2009, 08:46 pm »

That's fine. I just figured you had it sitting in raw form uncovered. Just trying to make as little mess in the house as possible.

Bryan

terry j · « **Reply #24 on:** 19 Oct 2009, 10:07 pm »

Quote from: Browntrout on 19 Oct 2009, 03:50 pm

Or..... knock them together, chuck them in the corners and listen to something with strong bass in it then let us know what you think.

you gotta be careful with THIS even! at times.

I remember once (straight up I'll say this experiment was bass eq, NOT trapping, but the lesson was a valuable one) when on a very expensive systems with horrible bass response we 'fixed' it with eq. (for a lot of reasons it was a very slap dash install, so I was VERY surprised at the vast improvement we got)

The owner comes in, pulls out a track and played it and said 'a bit dry' or whatever.

WTF! So we (I) sit in the seat and listen, and yeah, what are the odds, that ONE track out of god knows how many the peaks and dips we know where there in the measurements kinda fit perfectly with that ONE track! (ie, if you had a 'preference' setting you could apply to different tracks, the *room response* was a perfect 'preference' setting for that ONE track)

So I fully echo earlier comments about seeing changes in measurements (not that we listen with measurements only of course, we do use our ears) simply because I found yet another way we can be 'fooled' by our ears!!

The solution is of course listen to a range of music with bass, and I know that was what was meant in the quote I highlighted, just that it was an amusing experience!

BobM · « **Reply #25 on:** 20 Oct 2009, 01:16 pm »

I'm loooking forward to seeing the scientific-like results of your test. I've made some of these pipe insulaiton types of traps, using smaller dimension tubes and hanging them in various locations near corners. I left the outer paper on one side and took it off the other. The paper faces out and acts as a kind of diffraction while the back side absorbs (not anything on the low end because of the small diameter, I'm sure). I did fill the center with regular pink fiberglass insulation and capped the ends with cardboard, mostly for looks.

They seem to work well enough for my diffraction needs but I'm not sure they absorb much of anything at all, though I really haven't given it a true test of any sort.

You can see them hanging in this picture. There's another beefier one hanging behind the GIK panel in the corner. The dark blue cube on the bottom is a bass trap I made into the wall corner that's packed tight with fiberglass insulation beneath some 1" rigid fiberglass panels.

bdiament · « **Reply #26 on:** 20 Oct 2009, 01:27 pm »

Hi Bob,

They would need to have a bit more diameter to function in the bass.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

bdiament · « **Reply #27 on:** 20 Oct 2009, 01:31 pm »

Hi Tony,

One other thought about the test in the small (11 x 10) room:

This won't test the function of the traps at the bottom of their effective range because the fundamental mode for longest dimension is only ~103 Hz.

The test will still be valid for frequencies from here upward of course but know that differences (both audible and measurable) will be larger in a larger room, where the fundamental mode for the longest dimension could be considerably lower, hence "testing" the various devices a bit more severely.

Above all, have fun!

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

bpape · « **Reply #28 on:** 20 Oct 2009, 01:54 pm »

I would respectfully disagree. While that's the longest AXIAL mode in the room, there are others that are considerably lower. Even so, there can still be anomolies which are not modal in nature that the treatments can impact.

Bryan

bdiament · « **Reply #29 on:** 20 Oct 2009, 02:16 pm »

Hi Bryan,

And the modal issues would be lower still in a larger space, hence providing a tougher, more revealing test.

No doubt, the 11 x 10 room will show something. Just not by any means as much, in my view, as a larger space would. After all, to test a bass trap, I want to give it bass. ;-}

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

bpape · « **Reply #30 on:** 20 Oct 2009, 02:51 pm »

The use of the small room, IMO, will be better for this particular test given the limited sample size that will be used. There will be just as much bass at the same frequencies from DIRECT sources in this room as in the other. There will just not modal issues down to 20Hz and below.

The impact of 2 absorbers in a 10x11 room will be of more consequence than in a larger space. Regardless, they will do what they will do and COMPARITIVE differences can still be gleaned from this experiment.

Bryan

Ethan Winer · « **Reply #31 on:** 20 Oct 2009, 03:06 pm »

Quote from: bdiament on 20 Oct 2009, 01:31 pm

(11 x 10) room ... the fundamental mode for longest dimension is only ~103 Hz.

Um, guys, the lowest axial mode in a room 11 feet long is 51.4 Hz as computed here:

Graphical Mode Calculator

and here:

Bob Golds Room Modes

But whether it's 51 or 103 Hz is irrelevant, and Tony's test will still be valid. Two or four bass traps will have far more effect around 100 Hz than an octave below. And this will be clearly seen in the waterfall plot Tony posts.

--Ethan

bdiament · « **Reply #32 on:** 20 Oct 2009, 03:22 pm »

Hi Bryan,

It is the room Tony has to test with, so it will show what it will about the different devices.

I'm not so sure a room with such close dimensions, a considerably more difficult room because of this, will necessarily reveal more about two absorbers since they have a more difficult task to do than they would if the room was similarly shaped to his normal room but just smaller. Actually, in my experience, using only two (or only four) absorbers in any room will only begin to show what they can do. Perhaps that will suffice for this test.

And while it will certainly test the different approaches as far as mid-bass, I would not personally make any judgments regarding their efficacy for anything below this. My point is I think Tony will hear differences but their magnitude will be less than they would be in a test with a sufficient number of absorbers used in the room in which he normally listens.

Just my perspective.
In any event, it will be interesting to hear of Tony's experiences.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

bdiament · « **Reply #33 on:** 20 Oct 2009, 03:25 pm »

Hi Ethan,

Quote from: Ethan Winer on 20 Oct 2009, 03:06 pm

...the lowest axial mode in a room 11 feet long is 51.4 Hz...

For the half wavelength, yes.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

TRADERXFAN · « **Reply #34 on:** 20 Oct 2009, 03:36 pm »

Barry,
I don't think the room size is going to be a problem.

Look at this quote directly from ASC, which quite coincidentally references an 11 foot room...
http://www.asc-hifi.com/articles/iar89.htm

"A little arithmetic shows that most people are not using fat enough Tube Traps to control the bass resonances of their listening room. If your longest room dimension is merely 11 feet (or more), then your room's fundamental bass resonance is 50 hz (or lower), and so you need to use the Super 16 inch. You shouldn't use the next cheaper model, the regular 16 inch, unless your room is less than 11 feet long."
Now I understand the "super" 16 has a built in helmholtz resonator trap.

I think when I do the bare room sweeps it will show modal problems under 100 hz.

-Tony

bdiament · « **Reply #35 on:** 20 Oct 2009, 03:48 pm »

Hi Tony,

Quote from: TRADERXFAN on 20 Oct 2009, 03:36 pm

...I think when I do the bare room sweeps it will show modal problems under 100 hz...

Agreed. I would be surprised if it was otherwise.

Assuming speakers with a relatively flat response (and of course, a mic with a flat response), I don't believe that is where the biggest issues in that particular room will be though.
And of course, speaker and mic placement can radically alter the picture.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

TRADERXFAN · « **Reply #36 on:** 20 Oct 2009, 03:58 pm »

Well the room will be the "cause" of the issues not the source, the Schroeder frequency of the room is going to be very high in this small of a room. So no matter how perfect the source is, I predict there will be very wild swings in response below 150hz.

bdiament · « **Reply #37 on:** 20 Oct 2009, 04:03 pm »

Hi Tony,

As I see it, the room is where the modes will originate. The source will excite them (or not) to varying degrees.

Agreed about "below 150 Hz", though I predict they will extend upward another octave, to ~300 Hz.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

TRADERXFAN · « **Reply #38 on:** 20 Oct 2009, 04:17 pm »

I guess the question of "what range are we testing for?" arises.

If we are testing bass traps, what level should we start with. I had thought I would just be putting the sealed servo sub in the room. But if we want the 500 hz range or something, I need to get a real set of speakers in there, so its going to involve more setup...

-Tony

Ethan Winer · « **Reply #39 on:** 20 Oct 2009, 04:17 pm »

Quote from: bdiament on 20 Oct 2009, 03:25 pm

For the half wavelength, yes.

Right, and that's how the lowest mode is determined. Only half of a wave needs to fit to support resonance.

--Ethan