Tim's Limp Mass Bass Absorbers

[Mctwins]

Originally Posted by Mctwins

Thanks for sharing.

More questions now then before.

Who is JohnPM?
What is Topt? Difference between standard ISO?
Uncertainties below 100 Hz? Explain further.
WHY is it not measured below 90 Hz in the graphs? The lines falls straight down.

I will look into REW..........

DanDan.........

Any answers to the questions??

[Sebg]

MCT, I will start off:

JohnPM is the author of the super useful freeware software, Room EQ Wizard (REW). Topt is explained in the manual.

[NLP]

I have also measurements done with ARTA if someone wants...

[Mctwins]

Originally Posted by NLP

I have also measurements done with ARTA if someone wants...

Yes, please do, but only if it is measured in sweep or periodic at 256k.

[NLP]

Sweep 256k, 96kHz
PN 256k, 96kHz
MLS 262144, 96kHz

[Bilou]

Is there any reason why the Primacoustic traps aren't sealed at the back ? Is the 'perfectly closed box' an absolute requirement or just an improvement ?

[kasmira]

I think the perfectly sealed box is only a requirement for these to be tuned. If they are used as a general absorber I can see why they wouldnt be sealed. In effect, the non sealed ones are velocity based, not pressure based as a sealed box would be. Is this correct?

Sent from my Nexus S 4G using Gearslutz App

[Tim Farrant]

Yes, need to be airtight. The air inside requires stiffness.

[Mctwins]

Originally Posted by NLP

Sweep 256k, 96kHz
PN 256k, 96kHz
MLS 262144, 96kHz

Thanks for the measurements.

I find it very strange that you don't have any reflections in the Impulse Response. How did you do the measurements and where was the speaker and the mic located?

The PN, both before and after looks also strange, high noise floor when looking at Energy Decay.

Here is the Energy Decay from PN "Limp Mass Membrane Added".



Something isin't right here. You have to redo your measurement and have better S/N ratio. Sorry, but this measurement can't be reliable.

Why dosen't it goes to 5000ms when looking at Energy Decay when you have measured it in 256k?
Mine does so, just wondering.

[Bilou]

So how to explain the performances of Primacoustic non-sealed traps ?

I'll try to make a couple of boxes and measure with and without backing (and share the results, of course).

[NLP]

Microphone on a stand cca. 1,3m high in the centre of the room.
Loudspeaker on a stand near membrane (so near the corner) and almost on same position when room was totally empty.
Center between tweeter/midrange on axis with microphone.
Sweep have much better S/N ratio.
Keep researching, try to compare with REW results.
You have enough results/data to see before/after.
All settings were set so as I wrote.
Do you think that I can (or will allow) take to pieces finished control room...

[Mctwins]

Originally Posted by NLP

Microphone on a stand cca. 1,3m high in the centre of the room.
Loudspeaker on a stand near membrane (so near the corner) and almost on same position when room was totally empty.
Center between tweeter/midrange on axis with microphone.
Sweep have much better S/N ratio.
Keep researching, try to compare with REW results.
You have enough results/data to see before/after.
All settings were set so as I wrote.
Do you think that I can (or will allow) take to pieces finished control room...

If you had the mic in the centre of the room there schould be some sign of reflection in the Impulse Response graph. Why isin't there any reflection??
In the Energy Decay graph it schould have a Diff: 10dB but you have in your graph Diff: 1,181dB. It is to low.

I don't have confidence in this measurements.

[Rod Gervais]

Originally Posted by Mctwins

I don't have confidence in this measurements.

You say this as though you think anyone here might care what you do or don't have confidence in.........

You still haven't figured out that no one here has confidence in anything you say?

Rod

[NLP]

Like I said:
"Keep researching, try to compare with REW results.
You have enough results/data to see before/after."

Membrane working if you like it or not

If you are not expert in that area just drop advanced analysis.
Yes I think also there is something suspicous with some ARTA data readings.

[Rod Gervais]

Originally Posted by NLP

If you are not expert in that area just drop advanced analysis.

Whatever point (in the universe) it would be, that you would find the exact opposite of an expert in the field of acoustics, will be where you would find him residing.........

Rod

[Mctwins]

Originally Posted by Rod Gervais

Whatever point (in the universe) it would be, that you would find the exact opposite of an expert in the field of acoustics, will be where you would find him residing.........

Rod

You are off topic now, I don't want to start a bickering fight with you.

[Rod Gervais]

The original comment you made was off topic - that would be the one we both responded to -

Making speculative statements as if they were fact (in a subject matter you know nothing of) is (in fact) off topic.....

Why don't you stick to speaking in an area you actually have some expertise in - there must be something......

Rod

[Mctwins]

Originally Posted by DanDan

There are reflections.
The time span on your graph is over 2 Seconds.
ETC or IR graphs normally focus on the first 20mS or so.
Again I can see no point or relevance in such questions.
From the content of these questions it is clear that there is simply no competence with ARTA or Measurement or Acoustics.
This thread should be about the Topic in the OP.
Not a series of blundering irrelevant questions.

DD

What graph?, it is not my graph! Oh yeah, it is much relevance.

EDIT; now I see the picture.

There is NO reflection if you see Impulse Response, c'mon guys, you all now this. NLP can post the picture for you.

[ben_allison]

So simply: is one of these better than a 2'x4'x6" dense foam (Roxul Safe n Sound) bass trap, straddling a corner?

[ciro]

Originally Posted by boggy

You're welcome!

Ok, here is link to thread where we discussed it at Pro Recording Workshop
Wavelet type test tone designed for personal listening acoustical analysis
(links for test files are included too)

Thank you for the test/files, Boggy!

Ciro

[Jens Eklund]

Originally Posted by Mctwins

Thanks for the measurements.

I find it very strange that you don't have any reflections in the Impulse Response. How did you do the measurements and where was the speaker and the mic located?

The PN, both before and after looks also strange, high noise floor when looking at Energy Decay.

Here is the Energy Decay from PN "Limp Mass Membrane Added".



Something isin't right here. You have to redo your measurement and have better S/N ratio. Sorry, but this measurement can't be reliable.

Why dosen't it goes to 5000ms when looking at Energy Decay when you have measured it in 256k?
Mine does so, just wondering.

It is painstakingly clear that a certain twin has limited experience of measurements and ARTA ...

The length (time) of the IR depends on the sample rate (96 kHz in this case). When checking the ETC, you normally zoom in on the first 60-100 ms or so and with a dB scale of about 30-40 dB. The S/N ratio of measurements using noise instead of log sweeps as stimuli, will generally have a higher noise floor.

If find it peculiar that you again and again try to make it sound like you know what you're talking about when you clearly do not.

[Rod Gervais]

Originally Posted by Jens Eklund

It is painstakingly clear that a certain twin has limited experience of measurements and ARTA ...

The length (time) of the IR depends on the sample rate (96 kHz in this case). When checking the ETC, you normally zoom in on the first 60-100 ms or so and with a dB scale of about 30-40 dB. The S/N ratio of measurements using noise instead of log sweeps as stimuli, will generally have a higher noise floor.

If find it peculiar that you again and again try to make it sound like you know what you're talking about when you clearly do not.

Jens,

LOL - It's useless - in a short while he will make believe none of this ever took place and then will suddenly begin acting as though he knew this all along - exactly the same as he did when he was talking about treating rooms with SBIR - and then (when asked what the acronym stood for) came back and said - "Of course I know what SBIR is" - and gave a classic description he must have found somewhere after using a search engine.......

He's a pip.......

Rod

[kasmira]

Originally Posted by ben_allison

So simply: is one of these better than a 2'x4'x6" dense foam (Roxul Safe n Sound) bass trap, straddling a corner?

It can be, certainly.

Safe n Sound is not foam, nor is it dense. It is very light wall insulation.

[Mctwins]

Originally Posted by Jens Eklund

It is painstakingly clear that a certain twin has limited experience of measurements and ARTA ...

The length (time) of the IR depends on the sample rate (96 kHz in this case). When checking the ETC, you normally zoom in on the first 60-100 ms or so and with a dB scale of about 30-40 dB. The S/N ratio of measurements using noise instead of log sweeps as stimuli, will generally have a higher noise floor.

If find it peculiar that you again and again try to make it sound like you know what you're talking about when you clearly do not.

Jens, get real here. It was a simple question to NLP, just for clarification.

Empty room; Periodic shows a T60 of 10 sec and a poor S/N, while sweep has a T60 of 1 sec with a better S/N ratio.

Both the periodic and Sweep have no reflections and down -20 dB in a concrete empty bunker. Jens, please zoom it in if you don't believe me.

I would not trust these measurment and sorry for saying this. Maybe there is a Limp mass absorber out there that works but I do have hard time to see this yet. Maybe it has to with the NLP strange measurements and lack of others as well.

DanDan has glorified these measurements as to make a point that the Limp mass works wonders. But I think he has to look over the measurments again.

There has to be more serious measurements first and then we can discuss if these limps is something to have.

[Jens Eklund]

Originally Posted by Rod Gervais

Jens,

LOL - It's useless - in a short while he will make believe none of this ever took place and then will suddenly begin acting as though he knew this all along - exactly the same as he did when he was talking about treating rooms with SBIR - and then (when asked what the acronym stood for) came back and said - "Of course I know what SBIR is" - and gave a classic description he must have found somewhere after using a search engine.......

He's a pip.......

Rod

Yup ...

[Jens Eklund]

No reflections ?


Poor S/N ratio?




MT: Have you ever thought about that the level of reflections will be very low in relation to the direct sound if the receiver is relatively close to the source ...

And how about the length of the IR depending on sample rate, did you know about this already? How are you going to make look like you already knew about this also ...

[Mctwins]

Originally Posted by Jens Eklund

Attachment 301849
No reflections ?

Attachment 301850
Poor S/N ratio?




MT: Have you ever thought about that the level of reflections will be very low in relation to the direct sound if the receiver is relatively close to the source ...

And how about the length of the IR depending on sample rate, did you know about this already? How are you going to make look like you already knew about this also ...

Jens, I said that periodic has a poor S/N and you are showing sweep. I said that sweep has a better S/N. If you show the sweep then you have to show at the same time the periodic.

Receiver is relatively close to the source...You have to get your facts straight before even start to write such a comment

If you believe that there is no strong refelections in that bunker then....
By looking at the IR then it seems that it is measured in a well damped and treated room.

T60, EDT dosen't add up between periodic and sweep. The green line in Energy decay should follow the decay of the curve. You know the one.

Ask NLP for further info.

[Jens Eklund]

Originally Posted by Mctwins

Jens, I said that periodic has a poor S/N and you are showing sweep. I said that sweep has a better S/N. If you show the sweep then you have to show at the same time the periodic.

Receiver is relatively close to the source...You have to get your facts straight before even start to write such a comment

If you believe that there is no strong refelections in that bunker then....
By looking at the IR then it seems that it is measured in a well damped and treated room.

T60, EDT dosen't add up between periodic and sweep. The green line in Energy decay should follow the decay of the curve. You know the one.

Ask NLP for further info.

Who taught you that sweeps offers better S/N performance than noise? Why use the IR with poor S/N ratio at all when we have a better IR (using sweeps)?

And you really need to learn about RTxx, EDT ect, and why you cannot use these calculations in SAS (Small Room Acoustics). Check this thread:

Is dead sounding control room a bad thing?

You clearly demonstrate that you don’t understand how all this works by your statements above.

[Mctwins]

Originally Posted by Jens Eklund

Who taught you that sweeps offers better S/N performance than noise? Why use the IR with poor S/N ratio at all when we have a better IR (using sweeps)?

And you really need to learn about RTxx, EDT ect, and why you cannot use these calculations in SAS (Small Room Acoustics). Check this thread:

Is dead sounding control room a bad thing?

You clearly demonstrate that you don’t understand how all this works by your statements above.

Please, ask the appropriate questions to NLP and get some real answers/facts. Recheck NLP files and redo your analysis.

I do understand enough about RTxx, EDT and so on. BTW I never said RTxx.

You can stick to your own belief if it can be used in small rooms or not, I really don't care.

[NLP]

I do not have nothing new to say McTwins.