Making muy own acoustic panels

[rocky500]

3 minutes ago, Perth.hifi said:

Nice. So can anyone download this software free of charge? Also, would the Mic that comes with your preamp be sufficient?

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"Room EQ Wizard" is free to download.

I have seen mics popup on SNA but one of the easiest to use is the MiniDSP UMIK-1.

It is USB and I just got an USB extension cable to make it a bit longer plus I ordered the Calibrated version for a bit more.

Edited May 25, 2017 by rocky500

[Perth.hifi]

"Room EQ Wizard" is free to download.
I have seen mics popup on SNA but one of the easiest to use is the MiniDSP UMIK-1.
It is USB and I just got an USB extension cable to make it a bit longer plus I ordered the Calibrated version for a bit more.

Sweet. Anyone in Perth selling our have one to lend? Please.

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[rocky500]

2 minutes ago, Perth.hifi said:

 

 

Sweet. Anyone in Perth selling our have one to lend? Please.

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I could lend you my one with a lappy already setup.

[almikel]

23 hours ago, Perth.hifi said:

Does any side make a difference?

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Very marginally, the dense side out will reflect more very high frequencies.

Bass frequencies won't be affected at all (were you hoping they would be?)

A quick sim of these panels on a wall (no gap)

In a Home Theater room with carpet and other soft furnishings, panels like these won't help improve bass and only remove top end -  this is not desirable.

 

[Perth.hifi]

Very marginally, the dense side out will reflect more very high frequencies.
Bass frequencies won't be affected at all (were you hoping they would be?)
A quick sim of these panels on a wall (no gap)

In a Home Theater room with carpet and other soft furnishings, panels like these won't help improve bass and only remove top end -  this is not desirable.
 

Wow. Is that REW? These batts ate the 75mm HD.

Aim has been improve room accoustics....all frequencies... both to control low end and tame high end.

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[Perth.hifi]

Just loaded it up. Lots of settings..

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[almikel]

 

 

 

36 minutes ago, Perth.hifi said:

Nice. So can anyone download this software free of charge? Also, would the Mic that comes with your preamp be sufficient?

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REW is free, as is ARTA, Holm Impulse, etc - but I happen to be most familiar with REW.

36 minutes ago, Perth.hifi said:

Also, would the Mic that comes with your preamp be sufficient?
 

That depends on the mike - if it connects via USB it should be fine - if via XLR (standard mike connection) it may require phantom power and a sound card with phantom power will be required to connect to a laptop running REW

 

6 minutes ago, Perth.hifi said:

Wow. Is that REW? These batts ate the 75mm HD.

No that's not REW, but another free tool available here:

http://www.acousticmodelling.com/porous.php

 

5 minutes ago, Perth.hifi said:

Just loaded it up. Lots of settings..
 

If you're referring to REW - not too many - but plenty of online help available to get going.

If you can use your existing microphone then you're set...

 

cheers

Mike

[almikel]

32 minutes ago, Perth.hifi said:

Aim has been improve room accoustics....all frequencies... both to control low end and tame high end.
 

 

 

On 5/21/2017 at 9:52 PM, Perth.hifi said:

For us novices, sometimes it not clear... we all learn in different ways buddie...
 

 

Obviously I wasn't clear enough - if you want to control the low end - start with treatment targeted at low frequencies - thin panels won't help, and only chop out high end.

 

For some reason quotes across multiple pages isn't working for me tonight.

 

Review your whole thread - I've said the same thing a few times now - focus your treatment on getting the bass right 1st, then deal with other issues.

 

Keep your insulation for traps targeted for lower frequencies - minimum 100mm deep (200mm better). layering works fine.

Once bass is under control, then look at other treatment...

 

Mike

 

 

 

[almikel]

On 5/20/2017 at 5:59 PM, m_james said:

Sounds like too much of  pain in the arse to bother with.

You've probably never heard a well sorted room, because you wouldn't say that if you had.

Appropriately applied acoustic treatment is the best "bang for buck" upgrade possible for great "in room" sound.

I'd prefer a "reasonable" stereo in a well sorted room over a mega buck stereo in a poor room every time.

 

There's no point in spending big $ on gear if your room isn't good.

But get the room sorted and you so appreciate all that money you spent on gear.

 

Mike

 

[marten]

On 21/05/2017 at 7:10 PM, almikel said:

 

 

High frequencies travel like a light beam from a torch - with the speaker as the torch - any absorption in the path will absorb high frequencies.

Below the "transition zone" of the room (typically around 200-300Hz in most domestic rooms), the room behaves like the inside of a bicycle pump - pressure rising and falling - and you have room modes based on the room dimensions that define where the peaks and dips are.

 

Below the transition zone, physics tells us that the air pressure is at a maximum and air velocity is minimum at boundaries (walls). Velocity of air particles is highest and air pressure lowest at 1/4 wavelength away from a boundary (there's an inverse relationship between velocity and pressure).

 

Absorption works as a velocity device - to work it needs to be placed in areas of high air velocity.

Velocity at a boundary is theoretically zero.

This is why gapping of absorption (away from the boundary) is recommended.

 

 

I'm a bit late coming to this thread; just in the process of catching up and I came across the above quote from Mike a few days ago.  It really explained very neatly a couple of things I was wondering about, so THANKS to Mike for throwing in some relevant fundamental facts.

 

Having made a couple of mid size panels and making a couple of bigger ones, I'm really starting to think about initial placement.  The max velocity at 1/4 wavelength mentioned above got me to get my calculator out. 

 

Now I was hoping to target the  range 60 to 150Hz, but placing a panel 1/4 wavelength away from a corner at, say, 60Hz, means 1.4m into the room (not good).  Even at 100Hz it's 0.8m into the room, which is a bit more obtrusive than many people would accept.

 

So, what does this mean - that to absorb bass under 100Hz we can NOT optimally place our absorbing panels where the air is at max velocity (impractical) ?

[rocky500]

I followed the link to the accousticmodeling.com and changing the air gap, it did little if anything for how they work. I could be using it wrong too.

It seems the thickness is the important factor. 

 

Would anyone know if placing a barrier in front of my installation how thick I could go to stop the high frequencies been adsorbed but still work on midrange and below?

My other bass traps are a rectangle sealed wooden frame with installation inside. could I use a thin sheet of mdf or something similar?

Edited May 31, 2017 by rocky500

[marten]

I think a sheet of MDF will have too much effect on non-HF frequencies as well.

 

To target HF only, I like PeterTheGreek's suggestion:  " Failing measurements, best thing to do is put them up without covering in fabric and see how you like it. Too dead? cover some of it with plastic (preferably in strips) until you get it right. "

 

HF will be reflected by using a sheet of plastic stretched over the panel (or a non-permeable fabric).  PTG's idea is that you can titrate the amount of reflection by adding strips of such material, so it's not all-or-nothing.  That way you get to learn quite a bit about how to listen critically for HF effects, so it's a nice educational experience.

 

[almikel]

2 hours ago, marten said:

 

Now I was hoping to target the  range 60 to 150Hz, but placing a panel 1/4 wavelength away from a corner at, say, 60Hz, means 1.4m into the room (not good).  Even at 100Hz it's 0.8m into the room, which is a bit more obtrusive than many people would accept.

 

So, what does this mean - that to absorb bass under 100Hz we can NOT optimally place our absorbing panels where the air is at max velocity (impractical) ?

Hi Marten,

yes when you run the numbers, absorption/velocity traps get very big to be effective below 100Hz or so.

You're correct regarding placement - it's impractical to place absorption at max velocity (1/4 wavelength) (unless you start building bass traps into furniture ), but IMHO any gapping is better than no gapping if using products like XHD which free stand nicely.

 

Keep in mind that non-rigid rooms are not that likely to have significant issues at 60Hz.

Those with more rigid rooms may need to look at pressure devices (membrane traps, limp mass etc) to treat specific issues <100Hz.

 

cheers

Mike 

[almikel]

2 hours ago, rocky500 said:

I followed the link to the accousticmodeling.com and changing the air gap, it did little if anything for how they work. I could be using it wrong too.

It seems the thickness is the important factor. 

Hi Rocky

Here's 100mm XHD on the wall (blue), and with a 200mm gap (green)  - I went from memory on the flow resistivity, but it's around there somewhere.

 

 

 

Mike

 

[davewantsmoore]

Yeah it's 8000/12000 for HD/XHD

 

 

5 hours ago, marten said:

Now I was hoping to target the  range 60 to 150Hz, but placing a panel 1/4 wavelength away from a corner at, say, 60Hz, means 1.4m into the room (not good).  Even at 100Hz it's 0.8m into the room, which is a bit more obtrusive than many people would accept.

 

So, what does this mean - that to absorb bass under 100Hz we can NOT optimally place our absorbing panels where the air is at max velocity (impractical) ?

 

If you place it directly on the wall (or somewhere else not idea) .... it won't do nothing.

 

.... but what it does tell you is that to affect the sort of frequencies you're looking at, the absorber needs to quite thick.     100mm thickness would the minimum that is even going to have a tiny effect at those frequencies.

 

People will put up thinner absorbers ... and they will hear a difference .... but it's not having much effect at 100Hz.

 

 

[rocky500]

Bought 4 light wood panels 1.2m x 140mm x 12mm from Bunnings tonight. (LINK) Will try and put the test "bass trap" together tomorrow.

I was going to use 2x 50mm batts or I could squeeze in 3 and compress them 10cm.

Is it better to not compress the XHD installation or nothing to worry about?

Looks like it will compress pretty easy.

 

I cut one of the XHD sheets twice, so left with 3 sections. They are now 1200mm x 800mm. Then I was going  to make the surrounds to suit. Put them in the corners maybe 1 on top of the other.

 

Or if anyone has any suggestions to something better?

 

 

Edited June 2, 2017 by rocky500

[Perth.hifi]

I know there had been a few posts about fabric. But could we refresh, best three options from fabric stores please.

Cotton?


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[Happy]

I know there had been a few posts about fabric. But could we refresh, best three options from fabric stores please.

Cotton?


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Hessian.


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[Perth.hifi]

Will Hessian allow some reflection, as I don't too much high end absoption

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[Happy]

Will Hessian allow some reflection, as I don't too much high end absoption

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Probably no it's quite transparent acoustically. But why would you want panels if you want HF flying around? If you wanna tackle bass only consider aggressive bass traps or DRC.


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[Perth.hifi]

Probably no it's quite transparent acoustically. But why would you want panels if you want HF flying around? If you wanna tackle bass only consider aggressive bass traps or DRC.


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I am tacking both low end, but want to tame alittle top end as well... my speakers focal 826v focals are very top end ish

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[Happy]

I am tacking both low end, but want to tame alittle top end as well... my speakers focal 826v focals are very top end ish

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Ah cool well taming them won't really make the sound dead. If it does, you try something else. Try something acoustically transparent first otherwise what's the point of all the hard work


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[Perth.hifi]

There's many that are see the, but not really breathable

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[frankn]

I used Linen cotton (from memory) from Spotlight. A couple of pictures to show you - close up so you can see the "transparency/weave". Mount them off the wall to improve effective range. The frames are filled with polyester acoustic batts as per the raw batt at the rear of the room. 

The moveable foam/Perspex ones are hybrid absorbers & diffusers. 

 

[Perth.hifi]

Polyester?
Linen Cotton?
Cotton?

With the breath test. Should I be blowing hard to feel my breath. Or easy breath against the fabric?

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