Diffusion best bang for your buck

[Elnido]

I have a difficult room actually its best described as evil.Remarkably I have achieved a good sounding room using a combination of bass traps,absorbers and diffusers.

The room dimensions are close to a cube as bad as it gets acoustically.A large glass sliding door leads onto a balcony-more bad.Two flatscreen tvs more bad.

I purchased 4 vicoustic corner bass traps and 12 cinema round absorbers.Luckily being single I was able to experiment and affix the panels in different locations until a good result was achieved.This was an improvement but the sound overall  was still grainy and bright sounding-hard wooden floor no carpet(forgot about that one). 

I was beginning to feel the evil room had won the sound battle.

As a last resort I purchased 12 vicoustic wavewood panels and began trial and error on those.Ok 4 wavewood panels at first relection point of speakers and 4 on the wall behind the listening sofa.Bingo the single biggest improvement in 40 years of hifi systems.Its like magic the stage is wide and all that harshness is hoovered away.Clarity in general is on another level.I might add the wall behing the speakers is 50% covered in absorbers.Sort of dead end live end.

 

Vicoustic know what they are doing in fact they say the wavewood is 70% absorption and 30% diffusion.I must say diffusion is very powerful and definitely worth the trouble.It doesnt have to be vicoustic this post sounds like an ad for them but other companies and diy diffusers abound. 

 

In summary the system is improved by a conservative 40%.Good cd recordings sound very good indeed.Happy to answer questions. 

[avian]

Which Wavewood's did you get?  Wavewood 60.4?  Wavewood Pro 60.4?  120.4?    What were you using on the wall behind the listening sofa before?  I've been meaning to get into room treatment, and the issues youve solved sound similar to how my room is now after replacing carpet with floating floorboards.

[Elnido]

Just standard 60.4 Wavewood.The wall behind listening position has 2 vicoustic super bass traps mounted in corner the rest of the wall had no treatment.Yep the floating floorboards will react with your ceiling  not good.

[Kanef]

Cubes are notorious.
Would you mind recording some measurements with your iPhone? I’m like to learn more.

 Cheers

Kane

[Kanef]

Reason for asking is that QD is usually the final step in the room treatment process. I’m interested to learn what you’ve done and how. 

[lemarquis]

Very interesting. I am looking into this as we speak. I have a room that is about 5m long  X 4m deep with a twist (study area off to the right adds 2m). Room is well furnished, carpeted etc. 

 

I wouldn't say I have major issues but always looking to improve. A slight bass boom sometimes, with some music. I sent some photos to a consultant who recommended 4 bass traps (due to brick and concrete walls) as the best bang for buck in my situation.

 

How does that sound? Seems you have made a significant improvement with the bass traps alone.

[Elnido]

17 minutes ago, lemarquis said:

Very interesting. I am looking into this as we speak. I have a room that is about 5m long  X 4m deep with a twist (study area off to the right adds 2m). Room is well furnished, carpeted etc. 

 

I wouldn't say I have major issues but always looking to improve. A slight bass boom sometimes, with some music. I sent some photos to a consultant who recommended 4 bass traps (due to brick and concrete walls) as the best bang for buck in my situation.

 

How does that sound? Seems you have made a significant improvement with the bass traps alone.

The vicoustic super bass improve punch and definition also reduce boom to a certain extent they have the added benefit of being a diffuser as well.However they are not able to influence truly deep bass notes.You need huge absorbers for that.Check out the attached image showing frequency range of musical instruments.You may be surprised how many instruments produce sound in the bass range.

[lemarquis]

Cheers. The bass boom I have is really in the upper bass region somewhere. I don't seem to have issues with the very low notes including pipe organ.

 

Good to know there is some diffusion going on there too. The ones I'm looking at are these

 

https://soundacoustics.com.au/product/bass-traps/lf70-corner-bass-trap-bear-series/

Edited July 7, 2020 by lemarquis

[Elnido]

Thats a good price for an absorber.Personally I think most acoustic type panels are a rip off.Let us know if they are good might buy a couple for my third corner.

[lemarquis]

14 minutes ago, Elnido said:

Thats a good price for an absorber.Personally I think most acoustic type panels are a rip off.Let us know if they are good might buy a couple for my third corner.

That's what I thought too. They were recommended a few times around here so I contacted them and received some sensible advice after explaining my situation. I will probably try 4 of these in corners and see how it goes and let you know.

[Kanef]

14 hours ago, lemarquis said:

Very interesting. I am looking into this as we speak. I have a room that is about 5m long  X 4m deep with a twist (study area off to the right adds 2m). Room is well furnished, carpeted etc. 

 

I wouldn't say I have major issues but always looking to improve. A slight bass boom sometimes, with some music. I sent some photos to a consultant who recommended 4 bass traps (due to brick and concrete walls) as the best bang for buck in my situation.

 

How does that sound? Seems you have made a significant improvement with the bass traps alone.

The strong bass boom introduced by your room size can be seen in the modal diagram below.  The fundamental is at 43Hz.  Then successive harmonics beyond. Until the fundamental is dealt with, that energy will create unwanted harmonics that smear the sound stage.


Your listening room has 12 to 15 dB of boost at 43 Hz. The very small amount of absorption provided by the units you’re contemplating will do nothing to improve the situation.  (As an aside the corners are not the correct placement for bass absorbers. They may be aesthetically pleasing but acoustically they’re almost useless in this position.)   

The only method of addressing sub and mid bass successfully is with mass coupled with absorption. The NRC coefficient stated @ 50Hz is 0.2. But what is this a measure of?  And what happens below 50Hz?  
Our Super 80 bass absorbers have an NRC of 0.6 right down to 20 Hz. Nevertheless, in a 48m3 room it will require substantial amounts of absorption, especially if you listen at high volume.  (Orchestral Music recorded properly can have a 100 dB dynamic range).

Correct room treatment requires careful measurement and then proper design. When this is achieved the resulting listening experience, even in a small room, can be remarkable.  

[Guest Peter the Greek]

^Loving the product flog. Just sayin

 

[Steffen]

2 hours ago, Kanef said:

Correct room treatment requires careful measurement and then proper design.

Or a lot of trial and error

 

While measurements are helpful every step of the way, design and predicted performance of acoustic treatment can be hit and miss. That’s because there are so many factors that are either unknown or not easily modelled.

 

I’m almost there (I think) with my room, having speakers, sub, bass traps and absorption in their more or less final positions. Last remaining thing is a set of Arqen LeanFrac diffusers I’m currently building, to address remaining slap echo and ringing in the high-mid to presence range.

[Elnido]

Yes I"m with you almost there.You can measure if you want but I also rely on my ears.As an experiment today I removed 4 diffuser panels from right side first reflection point and listened.Immediately I picked up that telltale brittleness to the high frequencies and a chaotic soundstage-the music became uninteresting.

 

On another point its amazing what you can do with laser cutting machines,think acrylic panels cut by laser and a backing of martini HD absorb.I wonder what the cost would be?Maybe the diy forum has some ideas.

[Steffen]

Martini absorb can be difficult to cut. I’ve settled on strong scissors (for the 50mm material), but I’d be interested to hear how others are cutting it.

[kelossus]

6 minutes ago, Steffen said:

Martini absorb can be difficult to cut. I’ve settled on strong scissors (for the 50mm material), but I’d be interested to hear how others are cutting it.

With a ultra sharp stanley knife you can cut it pretty clean, I get nearly all the way through with one pass. I have also done with an angle grinder which worked well.

[lemarquis]

4 hours ago, Kanef said:

The strong bass boom introduced by your room size can be seen in the modal diagram below.  The fundamental is at 43Hz.  Then successive harmonics beyond. Until the fundamental is dealt with, that energy will create unwanted harmonics that smear the sound stage.

 

To me it's a slight boom, but I always prefer an unsmeared sound stage.

Our Super 80 bass absorbers have an NRC of 0.6 right down to 20 Hz. Nevertheless, in a 48m3 room it will require substantial amounts of absorption, especially if you listen at high volume.  (Orchestral Music recorded properly can have a 100 dB dynamic range).

Where does one find these Super 80's ?

 

[Steffen]

1 hour ago, kelossus said:

With a ultra sharp stanley knife you can cut it pretty clean, I get nearly all the way through with one pass. I have also done with an angle grinder which worked well.

I didn’t get very far with the Stanley knife, but angle grinder sounds like something to try.

[Kanef]

I always rely on my ears also. It’s what is between them that’s unreliable. The road to psycho acoustic nirvana is littered with the bones of those who listen but don’t hear. We all hear what we WANT to hear. Especially when we’ve invested hard earned money. I’m happy to help when ur ready. Everyone comes around. Eventually. 
cheers

[Kanef]

We manufacture the Super 80. 
However I would need to do some measurements on your listening room. No charge. Then we need to discuss the results and make a plan. This will ensure we identify our target. Then we’ll know when we get there. 

[Kanef]

Re cutting XHD.  Hot wire works well. 

[Al.M]

Here’s quite a practical and effective YouTube demonstration, wait for audible end result of treatment vs none, although personally I find filling a room before and after with enough soft furnishing has a good effect so wait until then before resorting to treatment.

 

Edited July 8, 2020 by Al.M

[Kanef]

Yes drapes and furnishings need to be factored in to any room analysis, either by Sabin absorption summing or better, actual room acoustical measurements. However soft furnishings offer only minor absorption.  Any room, especially a small room, requires substantial and well designed passive absorption in order to produce a response that is acceptable. Remember that the objective is for the room to effectively disappear from the listening experience, allowing only the direct sound from the loudspeaker system to prevail. Otherwise why would you spend many thousands of dollars on your system. 
Room resonances, especially low frequency resonances, distort the sound coming from your loudspeakers.  Why would you want that? 
Successful room treatment must start with treatment of the lowest frequency modes in the room. If you try for the mid range first then you’ll never make it because you can’t beat out the high energy bass modes with mid range treatments. The physics doesn’t allow it. And if you install diffusion before dealing with everything else your just going to amplify all those lower distortion modes and you’ll end up in a worse situation than when you started out. 

A note on XHD.

The bass absorption profile of XHD 50 mounted is shown below.  

 

The absorption response is substantially flat across the bass band, however the absorption rate low. This example illustrates one of the problems with the ISO 354 standard that NRC is derived from in lab testing. The standard uses the T20 reverberation time, that is the time taken for sound level to drop by 20dB. So a LARGE sample is placed in a room with known decay times and the resulting NRC values are calculated. 
The main issue with this approach is that T20 decay is not the important sound absorption characteristic that is required in a room. In fact excessive T20 decay is a real issue in a room and can make the room sound ‘dead’.  Everyone will have heard this in rooms that use glass wool as an absorber. Which was a popular low cost approach in the 1960’s and is unfortunately still being used today.

 

Contrast the XHD profile with the absorption profile of our Axial Mode absorption panels which have been designed to deal with the kind of primary mode issues that are so annoying when listening in a small room.

 

I hope this helps you.  
cheers

Kane