Comparing superchunks w/different densities
Old 7th February 2011
  #31
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Quote:
Originally Posted by bwo View Post
And then with the two different superchunks (45 kg/m3 and 65 kg/m3) placed in the corners.
Did you work as hard as possible to maintain exactly the same locations for the absorbers and the microphone? Was there a background noise source on for the denser material test? The ongoing sound around 40 Hz in the denser material test would suggest that.

Andre
Old 7th February 2011
  #32
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Microphone and superchunks were in the same place. It's pretty silent here, but may come some sound from the TV downstairs.

Anyway. Did new measurements. Looks ok to me.
Attached Thumbnails
Comparing superchunks w/different densities-left-45-kg-2.jpg   Comparing superchunks w/different densities-left-65-kg-2.jpg   Comparing superchunks w/different densities-right-45-kg-2.jpg   Comparing superchunks w/different densities-right-65-kg-2.jpg  
Attached Files
File Type: wav Left 45 kg.wav (384.0 KB, 5 views) File Type: wav Left 65 kg.wav (384.0 KB, 5 views) File Type: wav Right 45 kg.wav (384.0 KB, 3 views) File Type: wav Right 65 kg.wav (384.0 KB, 3 views)
Old 7th February 2011
  #33
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Quote:
Originally Posted by bwo View Post
The funny thing is that I've actually had some professional help with treatment.
Ouch. Sorry, did not want to offend anybody ...

BTW are you using REW? In that case you could eventually set up your sweep to be longer and only in the desired frequency range, then the resolution in the low intensities could be better.
Old 8th February 2011
  #34
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Quote:
Originally Posted by Hannes_F View Post
Ouch. Sorry, did not want to offend anybody ...

BTW are you using REW? In that case you could eventually set up your sweep to be longer and only in the desired frequency range, then the resolution in the low intensities could be better.
Yes, I'm using REW. I used 512k and two sweeps. I thought about using the longest one.....

Are you sure I will get a more accurate sweep, measuring only the spesific range? I think it was Lupo who told me that if I was going to do that, it would be better to diconnect the midrange and treble connection to the speakers and also something about doing another loop with the soundcard. Just a bit more work then I would like to do.

But, can we say anything from the measurements I've posted?
Attached Thumbnails
Comparing superchunks w/different densities-measurement.jpg  
Old 8th February 2011
  #35
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Quote:
Originally Posted by bwo View Post
Yes, I'm using REW. I used 512k and two sweeps. I thought about using the longest one.....

Are you sure I will get a more accurate sweep, measuring only the spesific range? I think it was Lupo who told me that if I was going to do that, it would be better to diconnect the midrange and treble connection to the speakers and also something about doing another loop with the soundcard. Just a bit more work then I would like to do.

But, can we say anything from the measurements I've posted?
Al long as you use long enough sweeps (5-15 sec should be adequate) and perhaps some averaging (6 to 24 sweeps perhaps) if you have a lot of background noise, you should be fine.
Old 9th February 2011
  #36
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So, can we conclude that the superchunks with different densities here perform pretty much the same?

And is it time to move on to pressure based traps?
Old 9th February 2011
  #37
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Hei Bjørn!

Didn't see much difference in those measurements. A negative results can be as good as, if not better, than a positive one. Thanks for the time and effort!

Quote:
Originally Posted by bwo View Post
Are you sure I will get a more accurate sweep, measuring only the spesific range? I think it was Lupo who told me that if I was going to do that, it would be better to diconnect the midrange and treble connection to the speakers and also something about doing another loop with the soundcard. Just a bit more work then I would like to do.
That was a different subject (with regards to the disconnection, looping etc).

The partial sweeps have problems in the start/stop zones. The signal will be contaminated where it starts and stops for the same reason that the speakers says "plop" when abruptly starting/stopping a sound wave. 0 Hz to half the sample rate will ensure a clean test signal is delivered to the room.
Old 9th February 2011
  #38
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Quote:
Originally Posted by bwo View Post
And is it time to move on to pressure based traps?
!!! Yes!!! Way overdue.. :D
Old 9th February 2011
  #39
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Quote:
Originally Posted by bwo View Post
So, can we conclude that the superchunks with different densities here perform pretty much the same?

And is it time to move on to pressure based traps?
I would (I wouldn’t have used the porous only absorbers for bass in the first place but that’s me ). Please note that placement and area are other important factors. Velocity based absorbers will also work if very thick, in the right place and lots of area covered but personally I´m not a big fan of this method for various reasons.
Old 9th February 2011
  #40
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Quote:
Originally Posted by Jens Eklund View Post
I would (I wouldn’t have used the porous only absorbers for bass in the first place but that’s me ). Please note that placement and area are other important factors. Velocity based absorbers will also work if very thick, in the right place and lots of area covered but personally I´m not a big fan of this method for various reasons.
Perhaps I wouldn't had either if someone had told me.
But porous material is the general recommendation. And it definetly works to improve the sound and it's cheap, but it doesn't seem to affect the response much below 150 Hz. At least not in my room and I have used a lot.
Old 9th February 2011
  #41
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Quote:
Originally Posted by bwo View Post
Perhaps I wouldn't had either if someone had told me.
But porous material is the general recommendation. And it definetly works to improve the sound and it's cheap, but it doesn't seem to affect the response much below 150 Hz. At least not in my room and I have used a lot.
To absorb significantly below 150Hz, need to use low density pink fluffy 10Kg/m3 (1pcf ?) to build thick panels 16" at least (play with Porous Absorber Calculator: pink fluffy sir flow resistivity is 5000 rayl/m, OC 703 is 15500)
Old 9th February 2011
  #42
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Except for lowest mode (40hz), which none of 64 or 45 chunks helped to tame, decay/waterfalls were ok(controlled) before the superchunks placement.Then, saying that the treatment isn´t working below 150 hz is not truth, because the "before",or "no treatment", is, in fact, a room with (picture shows) at least 2 thick bags with 30 kg rockwool plus 6 panels spread in the walls (looks like 4"). Then I´d say the porous absorber worked well in the room. Frequency response could certainly be improved a bit(or a lot) with mix and speakers position.

Ciro
Old 10th February 2011
  #43
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One or Two speakers

Quote:
Hm, ive heard many people on this forum suggest to use Mono drives for the low end. So im a little confused here...
This caught my eye, as did Jens intriguing reply.

Quote:
If you want to know the response of a listening environment, then both separate and together is best (since the combined response of room modes and SBIR is not as easy as just add together, it’s the sum of a lot of vectors with different phase). If you are trying to understand the behavior of modes in a room, then one driver is the way to go.
I reckon any short answer is destined for failure but I will give this a shot.

Based on ISO and other test methods the best way to investigate modal behaviour is to place an omni speaker (most are at LF) in the corner on the floor. Two or even four are preferred. This ensures that the largest number of modes are most evenly stimulated.

Our real life situation entails two actual speaker positions, considerably constrained e.g. tweeter at ear height, not in the middle of the room.
The speakers can be placed close to the front boundary for added LF pseudo soffit, or at particular distances from it for various reasons, e.g. to create SBIR action to compensate for something else. Similarly the side boundary.
Speakers may be placed in nulls of a particular mode to diminish it's action.
Typically in the nulls of the x2 side mode.

And so on. I reckon all cylinders have to be fully firing to deal with this one.
However, to reduce all of this, I am afraid I have to disagree and agree with Jens...

Two speakers in and around their final locations will give the best measurement of reality. One at a time helps with optimising the positions.

And just in case... one at time for Full Range, HF, or ETC.

DD
Old 10th February 2011
  #44
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Quote:
Originally Posted by DanDan View Post
Based on ISO and other test methods the best way to investigate modal behaviour is to place an omni speaker (most are at LF) in the corner on the floor. Two or even four are preferred. This ensures that the largest number of modes are most evenly stimulated.
If you use more than one simultaneously, it’s a bit tricky to know what’s going on if you’re on a mode hunt.
Old 11th February 2011
  #45
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Nuance

Quote:
If you use more than one simultaneously, it’s a bit tricky to know what’s going on if you’re on a mode hunt.
Depends. Surely a tri corner (floor) gets the majority of modes going.
Two tricorners, more so, statistically more. That's as far as I have seen the 'industrial' testing go, but I can only assume that four is even better.
Maybe 38% locations should be considered?

But that's for 'pure' modal research. Speakers in actual possible positions may not stimulate some modes much, thus 'reality'.

Anyway I am only playing with this, we both (wisely I believe) say one, then the other, then both. On the fly, measurements can be taken quickly and the interactions if significant do show up.

I reckon the frequent question as to 'one or two speaker drive?' is due to this complexity. There is no simple answer. Do you want to view the full modal behaviour or the actual modal behaviour using actual speaker and listen positions? Pure or realistic. And so on. Thus the confusion, but it is a strange sort of fun too isn't it?

If I had to give one simple answer to all of these conundra, it would be-

One.

DD
Old 11th February 2011
  #46
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Quote:
Originally Posted by DanDan View Post
Depends. Surely a tri corner (floor) gets the majority of modes going.
Two tricorners, more so, statistically more. That's as far as I have seen the 'industrial' testing go, but I can only assume that four is even better.
Maybe 38% locations should be considered?

But that's for 'pure' modal research. Speakers in actual possible positions may not stimulate some modes much, thus 'reality'.

Anyway I am only playing with this, we both (wisely I believe) say one, then the other, then both. On the fly, measurements can be taken quickly and the interactions if significant do show up.

I reckon the frequent question as to 'one or two speaker drive?' is due to this complexity. There is no simple answer. Do you want to view the full modal behaviour or the actual modal behaviour using actual speaker and listen positions? Pure or realistic. And so on. Thus the confusion, but it is a strange sort of fun too isn't it?

If I had to give one simple answer to all of these conundra, it would be-

One.

DD
Why would you want to make measurements with speakers in more than one corner simultaneously playing when identifying modes?

I think it’s really simple; if you want to identify modes, use one speaker at the time in one or more corners (depending on the symmetry of the room). If you want to know the response it the sweet spot, measure them separate and together. If the bass in music material is paned dead center (usually is more or less), the together measurement is valid, if paned hard left/right, then the individual measurements are valid. If paned in-between, well … then you don’t know exactly but do you really bother?
Old 11th February 2011
  #47
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+1 Jens, concise and simply stated.
Old 11th February 2011
  #48
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Labs

Quote:
Why would you want to make measurements with speakers in more than one corner simultaneously playing when identifying modes?
You wouldn't. If the purpose is to identify and focus on individual modes, then single speakers can be placed strategically to stimulate particular modes most strongly. The single speaker can even be placed in nulls of other modes to highlight the 'wanted' one. When doing comparative tests of absorption we need the exact opposite of this. All modes equally driven. This is not really an opinion particular to myself. It is common practice in Lab testing, and in testing in the world of Building Acoustics.
In parallel there is research to show that more modes are more evenly driven by multiple subs. 2 better than 1, 4 better than 2.
I suppose in a symmetrical room with all boundaries similar, maybe one corner is enough. However, for an asymmetrical room (most perhaps) I guess two would be better, placed in the corners which illustrate the difference. The OP room is L shaped.

No big really, the main point I wanted to highlight here is the floor corner placement. The stronger more even stimulation of most modes makes testing more likely to succeed. Topic.

Ethan has stated that LF panning thing too. That was true in the days of vinyl but is long gone. Instruments such as Electric guitar (80Hz), pianos, electronic keyboards (down to 30's), and even percussion such as Djembe or Bodhran, often have strong low LF content.
All of these are typically widely panned.
DD

Last edited by DanDan; 11th February 2011 at 12:51 PM.. Reason: Clarity
Old 11th February 2011
  #49
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Quote:
Originally Posted by Jens Eklund View Post
Why would you want to make measurements with speakers in more than one corner simultaneously playing when identifying modes?
Quote:
Originally Posted by DanDan View Post
This is not really an opinion particular to myself. It is common practice in Lab testing, and in testing in the world of Building Acoustics.
In parallel there is research to show that more modes are more evenly driven by multiple subs. 2 better than 1, 4 better than 2.
Lab testing? I’m talking about the process of identifying modes in a room.


Quote:
Originally Posted by DanDan View Post
Ethan has stated that LF panning thing too. I am afraid I have to point out that instruments such as Electric guitar, pianos, electronic keyboards, and even percussion, often have strong low LF content and are widely panned.

DD
Yes, but how am I contradicting your opinion on this?

Quote:
Originally Posted by Jens Eklund View Post

If the bass in music material is paned dead center (usually is more or less), the together measurement is valid, if paned hard left/right, then the individual measurements are valid. If paned in-between, well … then you don’t know exactly but do you really bother?
Old 11th February 2011
  #50
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Claro

Jens, we appear to be typing simultaneously.
The thread is about comparative testing of SSC's. I am talking about normal and enhanced testing techniques focussed on delivering a result of the test.
I believe such techniques may well show up subtle differences whereas leaving the speakers where they normally are will not. Just trying to help the OP.

Quote:
Quote:
Originally Posted by DanDan
Ethan has stated that LF panning thing too. I am afraid I have to point out that instruments such as Electric guitar, pianos, electronic keyboards, and even percussion, often have strong low LF content and are widely panned.

DD
Yes, but how am I contradicting your opinion on this?
Here is where our opinions on LF panning differ-
Quote:
If the bass in music material is paned dead center (usually is more or less)
DD
Old 11th February 2011
  #51
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Quote:
Originally Posted by DanDan View Post
Here is where our opinions on LF panning differ-
Maybe in the 60's but in modern music? Please note that I'm not saying that the bass region is always paned dead center, but the bass guitar and kick, in modern music at least, usually is (again; usually).
Old 11th February 2011
  #52
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Quote:
Originally Posted by DanDan View Post
I am talking about normal and enhanced testing techniques focussed on delivering a result of the test.
And I was talking about how to identify modes. Only one source at the time then.
Old 11th February 2011
  #53
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Fraid not

I would agree with often but not usually ;-)
The vinyl requirement for mono bass is gone and some of us take advantage of the 'new' freedom. Two drumkits happens, but much more likely is a combination of real and programmed electronic kits or deep percussion. Bottom end of keys is often a hard pan.
Anyhoo this is digression. My main point remains. If people want to test the performance of traps, the topic of this thread, the fuller modal drive from a floor corner speaker is of benefit. This is a big enough improvement, and I personally would probably leave it at that, i.e. just use one.
I am now beginning to question the use of two. Which corners? Diagonally opposite or two at the same side of the room? Hmmm.
Back to One
DD

Last edited by DanDan; 11th February 2011 at 01:26 PM.. Reason: Topic
Old 11th February 2011
  #54
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FWIW in orchestral music the basses vary according to the seating but often they are about 50 % to the right, behind the celli.
Old 11th February 2011
  #55
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Quote:
Originally Posted by Hannes_F View Post
FWIW in orchestral music the basses vary according to the seating but often they are about 50 % to the right, behind the celli.
YA and I can hear it on many classical recordings "vinyl". However for electronic music on "Vinyl" it is better to center the bass as you can get a hotter level.

:D

but anyways back on topic.....
Old 11th February 2011
  #56
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Those of you who have experience with pressure based absorebers, what do you use for the tricorners? Using something that's narrow banded seems to be caveat.

I came over something interesting in that regard. Far-Audio uses a combination.


Quote:
This panel is made to trap the bass frequencies. The bass trap must introduce significant absorption down to 30 Hz. The size must be ¼ wave length.

The most effective one is the corner bass trap. It is of prime importance to place bass trap in the corners because the distribution of the own modes in a standard room are always concentrated in the corners.

Panel combinations.

Helmholtz and absorbent:
The combination of an Helmholtz or perforated panels with an absorbent on the front covered with a nice fabric.
Resonant and absorbent:
This combination unsure a maximum absorption from the lowest frequencies up to the highest one.
Seems like the best of two worlds to me.
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