Making muy own acoustic panels

[Perth.hifi]

Everyone's thoughts on performance

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[davewantsmoore]

16 minutes ago, Perth.hifi said:

whats everyone's thoughts about the frequency performance of the 75 HD CSR martini panels???? Will it kill too much of the mid range?

 

Depends on how much you use, where they are located, and how your speakers illuminate them.     That matters a LOT more than agonising over what absorber material to use.

 

The real benefit of Martini Absorb.... aside from it being quite effective vs thickness at LF .... is that it has better data provided than others (predictable performance), and it is easy to work with (no lose fibres or itching).

 

[davewantsmoore]

40 minutes ago, Perth.hifi said:

Everyone's thoughts on performance

 

Very open question....

 

If you are looking to target mid-high reflections .... then personally I would not want to use much.   I would keep them in the corners/boundaries of the room.

 

Paradoxically .... If you want to fix bass issues in a domestic sized room .... You need to use quite a LOT of volume.    100mm thick would be the absolute minimum to bother with.   With 200mm+ being better.

 

 

You might find the right fabric to cover them with that will reflect higher frequencies enough for your use case ......  but this is difficult, and will take trial and error (becuase no data will exist for the fabric or material you use) .... and you'll need a way to evaluate the result (ie. measure, or have golden ears).

Edited May 18, 2017 by davewantsmoore

[Perth.hifi]

Maybe I'm over doing it... atm the rear 2 x side panels on each left and right walls are diffusers only.

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[Perth.hifi]

Maybe I'm over doing it... atm the rear 2 x side panels on each left and right walls are diffusers only.

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[davewantsmoore]

What are you trying to achieve?

 

 

If these are 75mm, they won't help with bass.... and you'll probably need to face them with something more than just breathable fabric (to reflect from mid-high)

 

I would recommend you do some testing before you make anything too final.    Listen with the room empty, and then 'full' .... before you cut any sheets, make frames, or cover anything.

[Perth.hifi]

Just trying to improve acoustics . Main reasons are to Reduce reflections, improve 2stereo sound. Reduce alittle bass that rattles ceiling.

Maybe I'm best to try a few with doubke sided tape first....

Will this proposal hurt the room accoust ics?

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[Stevesie]

In my small room I ended up with a couple of panels straddling the corners behind the speakers, 2 on the ceiling and 2 behind me.

 

When I first put the two behind me it was really disconcerting for a few days as the strong reflections from behind me had disappeared. I got used to it but really need to try some thin plastic over it one day to bring back a bit of the top end bounce and see what that is like.

 

I didn't get very scientific with my placement, but it made an enormous improvement nonetheless. One panel fell from the ceiling and has since ended up stacked on top of one of the corner panels at the front of the room - I think it worked better where it was on the ceiling(as it was probably dealing with a first reflection point).

[Perth.hifi]

Who's in Perth, and wants to come over for a listen and give dove recommendations. PM me.

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[almikel]

On 5/18/2017 at 9:13 PM, Perth.hifi said:

Just trying to improve acoustics . Main reasons are to Reduce reflections, improve 2stereo sound. Reduce alittle bass that rattles ceiling.
 

not many rooms have bass under control - IMO start there first

You won't fix rattles with treatment - you need to find and fix the rattles

 

cheers

Mike

[almikel]

On 5/18/2017 at 8:57 PM, Perth.hifi said:

atm the rear 2 x side panels on each left and right walls are diffusers only.
 

Absorption won't provide any diffusion unless configured with reflection in a Binary Amplitude Diffuser (BAD) sort of way.

Flat contiguous sheets of absorption need some sort of reflective mask to generate diffusion.

 

I'm not saying absorption on side walls is a bad thing, just that it doesn't provide diffusion.

 

 

cheers

Mike

 

[almikel]

On 5/18/2017 at 9:13 PM, Perth.hifi said:

Maybe I'm best to try a few with doubke sided tape first....

Will this proposal hurt the room accoustics?

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Double sided tape wouldn't come close to holding up Tontine Acoustisorb 3 - I assume Polymax will be similar...

If you want it working effectively as low as possible you should gap it anyway - it's rigid enough to straddle corners.

 

As I've mentioned above, apply treatment to get bass under control as the priority, which means decent sized traps straddling corners (and you have lots more corners to straddle than the four wall corners).

Worry about 1st reflection points once the bass is under control - and you might find you're adding reflective strips in front of absorption before you've got the bass under control, and your room Sabine count (absorption) is taking too much treble out - hopefully by this time your bass is getting close....provided the absorption is well placed and large enough.

Sidewall placement of absorption directly on the walls won't help manage bass at all, but will increase the Sabine count of the room  - beware of the common mistake of too much absorption with none of it absorbing low frequencies - boomy bass and chopped out treble - the bane of every band practise room I've been in.

 

To properly get the best out of room treatment, it can't be done by ear, and needs a measurement rig (microphone, stand, cable, PC, maybe a sound card depending on the mike).

 

I'm a self confessed bass nut, but in the rooms I've treated and mucked with (mostly my own), once the bass is under control, the overall absorption in the room is quite high, and other treatment options such as diffusion come into play, where energy remains in the room.

Thin (say <100mm) panels directly mounted on walls are a waste of time IMO unless you have a very bright room that's very leaky for bass (eg all 4 walls are glass)

IMO having EQ ability below 100hz is essential, as absorption becomes too big to manage freq <100Hz.

 

cheers

Mike

[Guest m_james]

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

[Perth.hifi]

Yeah... I'm thinking. The same thing. Well sounds like adding panels drains the sound system of treble. So what's the best way to add absorption panels without refucing the highs?

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[Guest Peter the Greek]

1 hour ago, Perth.hifi said:

 So what's the best way to add absorption panels without refucing the highs?

 

So bass is your issue? panels wont do much/anything....look into bass traps, a variety of options, but the best thing to do is to measure the room first and find out what you need to treat for.....or you can try the broadband approaches...I've had mixed success with that but many swear by it

[Perth.hifi]

Main issue, is echo, reflective souds, cleaning up sound.

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[Stevesie]

2 hours ago, Perth.hifi said:

So what's the best way to add absorption panels without refucing the highs?

 

Read back over the thread and you'll find the answer already mentioned :-)

Edited May 20, 2017 by Stevesie

[Guest Peter the Greek]

1 hour ago, Perth.hifi said:

Main issue, is echo, reflective souds, cleaning up sound.

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Panels are fine then. 50mm is fine. 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. Stay away from the first reflections IMO (assuming your speakers are decent)

[davewantsmoore]

19 hours ago, almikel said:

Double sided tape wouldn't come close to holding up Tontine Acoustisorb 3 - I assume Polymax will be similar...

 

Yep.   Tape won't hold it up.

 

My recommendation would be to stand up the absorbers in roughly the positions planned .... and that will give a good general idea if there is too much overall absorbtion in the room.

Edited May 20, 2017 by davewantsmoore

[almikel]

Hi Gi

20 hours ago, Perth.hifi said:

Main issue, is echo, reflective souds, cleaning up sound.

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unless your room is extraordinarily leaky in the bass end, some absorption targeted at lower frequencies should be considered. Cleaning up 100Hz - 250Hz makes a very big difference to the sound.

 

19 hours ago, Peter the Greek said:

 

Panels are fine then. 50mm is fine. 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. Stay away from the first reflections IMO (assuming your speakers are decent)

as PTG mentions - measurements are helpful in this regard - you want to target even reverb times across the frequency bands, which gets harder below 100Hz.

Too much absorption will reduce high freq reverb times too much - which is where covering the absorption with strips of something reflective helps.

I agree with PTG regarding staying away from 1st reflection points, depending on the off-axis response of your speakers (Peter's reference to how decent your speakers are). This doesn't apply to ceiling and floor 1st reflection points - absorption is fine for these (eg thick rug on the floor). 

 

19 hours ago, davewantsmoore said:

My recommendation would be to stand up the absorbers in roughly the positions planned .... and that will give a good general idea if there is too much overall absorbtion in the room.

I agree with this approach, but based on the rooms I've measured, I'd be surprised if there wasn't some control of bass required.

If you put thin panels up (which won't absorb any bass), then decide to add more absorption targeted at bass frequencies (we'll call them bass traps for simplicity), that's a recipe for a dead room.

 

Assuming your room isn't a bass sieve, ie it needs some treatment to manage bass, I would target initial absorption to get the bass under control - once this is achieved, the overall absorption of the room may be sufficient to have managed "echo, reflective sounds, cleaning up sound".

 

This is just my opinion, and every room is different, but most media rooms don't have lots of hard surfaces to reflect high frequencies (tiled floors, lots of glass) - but they mostly still have bass issues.

IMHO get the bass right 1st then look at other treatment.

 

The approach for applying absorption to manage bass frequencies (say 100Hz - 250Hz) is quite different to the approach for applying absorption to manage an overly bright room - but if your room is both (ie it has bass issues and is overly bright), you may find that after managing the bass, the room isn't bright anymore - and this is when adding reflective strips to absorption may be required.

 

Beware that once bass is under control, it becomes addictive, and the typical poor bass response in cinemas and live venues will disappoint - but you will grin like an idiot each time you listen to your system.

 

cheers

Mike

[davewantsmoore]

14 minutes ago, almikel said:

I agree with this approach, but based on the rooms I've measured, I'd be surprised if there wasn't some control of bass required.

 

Absolutely.

 

17 minutes ago, almikel said:

If you put thin panels up (which won't absorb any bass), then decide to add more absorption targeted at bass frequencies (we'll call them bass traps for simplicity), that's a recipe for a dead room.

 

Definitely.    Which is why drag it all into the room haphazardly to check for over absorption....  especially if going for a treatment plan which is not based on a detailed evaluation of the problem/solution.

[davewantsmoore]

23 minutes ago, almikel said:

applying absorption to manage an overly bright room

 

FWIW ... unless the room is very unusual .... all hard surfaces (like tiles or concrete) .....  then I strongly doubt it is a "bright room".   (ie. it's not a room acoustic issue).

 

 

"At loud" volume, would make me suspect clipping.

[Guest]

I think the pair of panels I am building today are Martini 75mm HD, in white.

Coming along fairly well 

Plenty of air driven staples to go

edit and a few internal slats to stiffen up the frame.

Had the pair of bats in the room for a few weeks and they work in my target range for first reflection diffusers well enough to build them into upholstered panels

 

 

Edited May 21, 2017 by Guest

[almikel]

23 hours ago, Perth.hifi said:

Yeah... I'm thinking. The same thing. Well sounds like adding panels drains the sound system of treble. So what's the best way to add absorption panels without refucing the highs?

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20 hours ago, Stevesie said:

 

Read back over the thread and you'll find the answer already mentioned :-)

 

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.

 

But from a pressure perspective, bass collects in corners - a tri-corner has 3 boundaries - all with a pressure maximum.

This is why you target corners for bass trapping - but if using absorption (a velocity device) you need to gap it (eg straddling the corner) so the absorption is placed where velocity is > 0.

For bass control, all corners work the same - wall/wall, wall/floor, wall/ceiling.

 

If you apply absorption that targets bass frequencies first (ie straddling corners), you avoid any 1st reflection points, but still soak up treble from secondary/etc reflections.

It's at this point you would determine if your room is "too dead" and apply reflective surfaces to the existing absorption (the bass will not "see" the reflective surfaces and continue to be absorbed), or apply additional absorption or diffusion as required.

 

As I've mentioned above, any remaining bass issues <100Hz are best dealt with via EQ, unless you want to experiment with tuned "pressure" traps - this is a different topic.

 

cheers

Mike

 

 

[almikel]

hi Matt,

I'm constantly in awe of your motivation to keep building stuff !!...

1 hour ago, 125dBmonster said:

..and they work in my target range for first reflection diffusers ...

...so apologies for being picky, but those panels won't provide diffusion - even with the pegboard involved.

I only raise this as the OP referred to absorption at 1st reflection points to provide diffusion earlier in this thread as per the OP's quote below

 

On 5/18/2017 at 8:57 PM, Perth.hifi said:

Maybe I'm over doing it... atm the rear 2 x side panels on each left and right walls are diffusers only.
 

 

I'm not trying to be a PITA - just attempting to keep the OP on track and not confused between absorption and diffusion.

 

Nice build (as usual) by the way 

 

cheers

Mike