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Room mode versus SBIR [measurements provided]
Old 27th August 2013
  #61
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Glenn Kuras's Avatar
Quote:
Originally Posted by Bobecca View Post
So, do you mean that you are representing a product with a success
You need to grow up and stop being a troll.


Sorry BigKD to see your thread being over run.

I am like Jens, out of here.
Old 27th August 2013
  #62
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Rod Gervais's Avatar
 

Quote:
Originally Posted by Bobecca View Post
So, do you mean that you are representing a product with a success
He happens to have a very successful company....... so the answer to that question would be an (obvious) "yes"............

You (on the other hand) know little about anything other than what you did in your room......... and (based on your posts) very little about anything acoustic in even that regard............. someone else led the way - and you enjoy the end result....... that (however) does not make you expert in all things acoustic....... which is why you prattle on with the inane little things you constantly state that make little to no sense to anyone who has even a basic understanding of acoustics.

You do not do this for a living, and are either too foolish - or simply too ignorant - to understand that there are many paths that can lead to success..... the means you took are certainly not the only means to make it from "A" to "B".......... it really is a pity you have no capacity to understand that..........

Rod
Old 28th August 2013
  #63
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Guys guys....

I go away for a day and look what happens lol!

I hope those interested in helping me solve my LF issues will keep on posting. Thanks for the help so far! I think there is a lot to be learned here. Well, at least I am learning a lot.

Sorry my measurements are a bit rough around the edges. As I said, I am still learning about all of this stuff. Hopefully they are decent enough to see what is going on on. I'll do the soundcard calibration after this post.

It looks like my uberchunk traps cleaned up a lot of ringing down to around 100hz or so. Do we all agree on this? I thought since they are so thick that they would go lower than that, but asi es la vida.
Old 28th August 2013
  #64
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Quote:
Originally Posted by HermanV View Post
I just want to point out that threads like these should be sticky-ed. Everyone participating brought up some very good points.

All I am going to say is that you should look into designing a rear wall membrane absorber. I would also look into the assembly issues with both walls being built out of different materials. Concrete boundaries are notorious for bass issues.
Are you saying I should try to change the building materials...cause that ain't gonna happen. This is a concrete basement and will always be a concrete basement.

Quote:
Originally Posted by Jens Eklund View Post
Yes; a reality check:

Unless his room is only about 1,75 meters long, the null at about 98 Hz is not related to the first axial mode. Absorption (any type of devise, as long as it´s effective at the target frequency) on a surface related to the interfering energy, and/or repositioning of the source/receiver will sort the null assuming it´s due to SBIR or a node (and not due to a lack of modal support in that frequency range). Treating only the first order axial mode with a high Q devise will only deal with problems related to that frequency range and problems related to the surface where it’s positioned. Since I know you (and your twin Bobecca...), and that you probably won’t accept these facts (this time either …); I´m leaving the thread now. Those who want to know more can read the “How to treat nulls” –thread. It´s enlightening in many ways.


EDIT:

And just to add to the confusion:

So how do I figure out what the interfering energy is?
Old 28th August 2013
  #65
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jhbrandt's Avatar
Quote:
Originally Posted by BigKD View Post
Guys guys....

I go away for a day and look what happens lol!

I hope those interested in helping me solve my LF issues will keep on posting. Thanks for the help so far! I think there is a lot to be learned here. Well, at least I am learning a lot.

Sorry my measurements are a bit rough around the edges. As I said, I am still learning about all of this stuff. Hopefully they are decent enough to see what is going on on. I'll do the soundcard calibration after this post.

It looks like my uberchunk traps cleaned up a lot of ringing down to around 100hz or so. Do we all agree on this? I thought since they are so thick that they would go lower than that, but asi es la vida.


No problem! I'll be here.. (I love that 'ignore' button - I don't see trolls)

Anyway, Yes, You are moving along nicely. But since you have two walls that are concrete and another 2 that are gypsum board - you will have some asymmetry under 100Hz. Membrane traps are in order.

You can build VPRs or:
My limp membrane type traps.. Sheet Steel glued to a rubber substrate suspended limp over a 4 3/4" cavity - sealed. Do not touch the membrane with absorption material. you can add 2" of rock wool or 703 in FRONT of the membrane as well, so that they can be place where you need them in the room without worry about reflection points. NOTE: my membrane design requires that the limp mass be free like a passive woofer cone... 3/4" air-space is reserved on BOTH sides of the membrane. This unit will function over a broad range centered around 50 Hz & down to nearly 20 Hz. (further details I cannot give out on a public forum)

Cheers,
John
Old 28th August 2013
  #66
Lives for gear
Quote:
Originally Posted by jhbrandt View Post


No problem! I'll be here.. (I love that 'ignore' button - I don't see trolls)

Anyway, Yes, You are moving along nicely. But since you have two walls that are concrete and another 2 that are gypsum board - you will have some asymmetry under 100Hz. Membrane traps are in order.

You can build VPRs or:
My limp membrane type traps.. Sheet Steel glued to a rubber substrate suspended limp over a 4 3/4" cavity - sealed. Do not touch the membrane with absorption material. you can add 2" of rock wool or 703 in FRONT of the membrane as well, so that they can be place where you need them in the room without worry about reflection points. NOTE: my membrane design requires that the limp mass be free like a passive woofer cone... 3/4" air-space is reserved on BOTH sides of the membrane. This unit will function over a broad range centered around 50 Hz & down to nearly 20 Hz. (further details I cannot give out on a public forum)

Cheers,
John
That's an invitation for a PM if I have ever seen one. I've read a lot of the threads here on VPRs, but I saw very little in the way of actually constructing them. Might have been looking at the wrong threads?

Your design sounds relatively simple to execute. Could I place a skyline diffusor over the top of it? Or does it only allow for a porous material such as 703 or rockwool?
Old 28th August 2013
  #67
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Mctwins's Avatar
 

Hallo!

I am refering to standing waves/room modes as sound pressure in air because this sound pressure is effecting our eardrums. That's why I am looking at freq response to see if the changes is happening when treament is being applied in the room.

When talking about standing waves it is important to specify what type of standing waves it is.

More readings here....

Room modes standing waves reflecting hard parallel walls acoustic resonance and vibrations modes nodes anti-nodes particle displacement sound pressure strings - sengpielaudio Sengpiel Berlin

and...

Standing waves acoustic resonance and vibrations on ideal strings - Standing waves are stationary waves room modes sound pressure level between hard parallel walls node antinode stationary room acoustic frequency - sengpielaudio Sengpiel Berlin
Old 28th August 2013
  #68
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Rod Gervais's Avatar
 

Your ignorance of the subject matter, and inability to understand the written word is only exceeded by your willingness to expose your ignorance to others......

The 2 links you provide are not examining 2 different phenomena - they are simply examining aspects of the same phenomena........

It is not us who need to understand - it is you....... perhaps if you were to take a college course on the subject (and pass it in the process) you would (finally) understand.. perhaps........

Rod
Old 28th August 2013
  #69
Lives for gear
Ok back to your regularly scheduled programming.

I made a measurement that may be of interest. I put the mic behind the speakers nearly touching the front wall. Of course the high frequencies are rolled off, but the bass response appears to be +/- 5db! I dunno if anything can be gleaned from this result, but I figured I would post it to see if it is of significance.

For some reason my REW software refuses to capture images of my results, so I attached the entire REW file
Attached Files
File Type: zip 8-28-13 behind speakers.zip (1.87 MB, 18 views)
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