On 19/11/2024 at 8:51 PM, Peter_F said:

that wall should have QRD diffusers NOT absorption panels

Why @Peter_F

 

Edited November 20, 20241 yr by JkSpinner
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On 19/11/2024 at 4:42 PM, almikel said:

I love the concept of limp mass bass traps using mass loaded vinyl (MLV)!

 

Hi Mike

Yes the traps work well, much better than a hard double plastered wall.

On 19/11/2024 at 4:42 PM, almikel said:

Double membrane! - love your work!

The double membrane ended up rather large (largest one I've made) and heavy for a single element in the bass treatment regime, it's the one in the photo provided, with the integrated CD rack.

It was stripped off the wall one time to take out some of the restrained layering of acoustic acrylic. This freed the membranes and accompanying twin air chambers in an attempt to tune it.  It was drum tight full of insulation to begin with.

On 19/11/2024 at 4:42 PM, almikel said:

My lightly constructed room leaks the low bass out - but if I needed "proper" bass traps, I would build limp mass traps.

Indeed

Being the Builder of that particular area from bare frame gave me the opportunity to listen to the evolution of the space from, leaky light construction. The odd call from the local boys in Blue meant the quite elevated floor overlooking neighbours needed sound proofing. Nothing dramatic, 2 times in 20 years, never the less someone was not happy.

 

Sound proofing using deep layering of fibre glass batting in ceiling (filled to the eves) , foamboard double plaster layering and 25mm thick external solid timber cladding, boxes behind power points. double glazed unit windows, created something unexpected. Shocking bass reverb and a literally untenable area for housing my HiFi creations.

 

The area ended up not unlike a  newly minted double brick room, however 20Hz and below  penetrate and leaked out. Through outside and inside measurements. leaks below 20 Hz were deemed the only advantage to the new area so, worked from there to improve the situation as the frequencies rose.

3 months of full time work ensued.  90 days or so of build and evaluate and still haven't quite finished. Thankfully I'm back in that house for a few weeks and I don't intend to be idle.

Calling on past experience and the availability of the MLV, cheap, locally forced my hand literally into giving the low profile MLV trapping a go (again).

They have to be very large in surface area exposed into the room in this case in excess of 12m2 , they have to be built onto and form part of the room structure to be effective, that and maintain the semi air tight chamber of air behind over decades. 

 

Outcomes are good, with the lounge now a comfortable area of reference to audio, beautiful, modern and efficient.

 

I wish now the ceiling had been done in CSR Perforated plaster however the visual of the 40mm thick 5 large panel installation is quite ok. Soon to go to 7 panels,,,,,

I find the absorption/MLV paneling now integrated and tweaked,  a very valuable part of this space, highly effective and would not really change much of the approach for the next job. 

Thanks for your interest over the years, of me plodding along in the dark mainly to this Tech.

 

To anyone watching on, measurement, measurement, clap tests and more testing is the order of things in this discipline  of hand made and engineered, professional room treatments, a very good handle on what you want AND an intimate knowledge of what acoustics are,  as well  a personal preference and where to stop,

 

Matt

 

 

On 19/11/2024 at 8:51 PM, Peter_F said:

IMO that wall should have QRD diffusers NOT absorption panels.

 

On 20/11/2024 at 7:01 AM, JkSpinner said:

Why @Peter_F

 

If your speakers have a smooth "off-axis" response, Toole/Olive/Geddes etc recommend you shouldn't muck with the spectral content (frequency response) of lateral 1st reflections, because you want the 1st reflection to sound the "same" as the direct sound from the speaker.

 

Absorption is guaranteed to muck with the spectral content, by absorbing more top end than bottom end.

 

So long as you're far enough away from a QRD, they won't muck with the spectral content, just diffuse the sound.

Cox and D'Antonio recommend sitting >3 wavelengths of the lowest frequency diffused for a QRD.

Closer than that and you may hear artefacts of the QRD doing its diffusion thing.

 

Mike

11 hours ago, almikel said:

lateral 1st reflections

It’s not the first or the second reflection.  It’s the third and fourth reflection, due to being right beside the listening position and at 45deg, hence why I chose to absorb it.  I have installed ikea room dividers with Hybrid diffusion at the first reflection point on both sides, mainly to provide some symmetry, these are shown in the photos.  QRD type diffusers would probably be best here I would imagine.  I chose the Hybrid panels as a bit of an experiment, as I could move them around the room, and use them as either absorbers or diffusers, although only one dimensional diffusion.  I have stayed away from QRD diffusers for several reasons, the cost, most are not cheap, the weight, many are heavy, I do not have side walls to hang them on, I needed a portable solution that I could slide into place when needed, and adding absorbers to the ceiling is not on the radar, so I did not want to add any additional reflections to the ceiling, that could ultimately reflect back to the listening position.

i may still add something for the second reflection point, perhaps the foam type QRD diffusers that could also hang on the ikea room dividers may work.  

On 22/11/2024 at 6:34 AM, JkSpinner said:

It’s not the first or the second reflection.  It’s the third and fourth reflection, due to being right beside the listening position and at 45deg, hence why I chose to absorb it.

fair enough - personally I wouldn't worry about absorbing 3rd and 4th reflections, especially in the top end, unless your room has way too much treble reflecting around.

Looking at the photos of your room with carpet and a big absorbing couch and curtains you can adjust I don't think you need absorption on that wall. 

 

I just went back to review the content of your other thread to see where that got to...

 

I just have to say - well done!

I'm sure your room sounds fantastic! - sit back and enjoy the music!!

 

Voltaire said, "perfect is the enemy of good"...

...keep tweaking if you want...but you've exceeded "good" - so make sure enjoying the music is the priority not perfection!

 

cheers,

Mike

1 hour ago, almikel said:

absorbing 3rd and 4th reflections

Thanks Mike, I am pretty happy with the end result.  The brick wall is a bit strange, it’s not really 3rd and 4th reflection.  Because it is at 45deg right beside the couch, it is a second set of 1st and 2nd reflections, direct reflections from each speaker.  And as the couch is so close, I thought it best to absorb.  The panels came in a set of four, I could only fit three on the back wall, so I think worth it.

i still think I need to do something with my entrance, the entrance being joined or part of the media room, but as I have created a 1st reflection point on the right side, by using the Hybrid panel on the ikea room divider in the open wall, I think this may alleviate the entrance issue a little.  Anyways, that is for later.  I need to set my subwooofer up better, then spend some enjoying (which I already do)