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Room treatment - particularly side-wall reflection. Experiences?

gustavm

pfm Member
Hi

Has anyone experimented successfully with room treatment, particularly in reducing "first reflection"?

Tackling this seems to be a first recommendation from many of the companies selling absorber panels - i.e. placing the panels on the side walls between speaker and listener, and possibly also on the ceiling in order to reduce the amplitude of the first reflected sound reaching the user.

Another view (see link) is that this is a bad thing to do, and this Hifi News link suggests that it can make matters worse. (Since absorbers work primarily at frequencies above a few hundred Hz, they don't remove the reflection but merely change its spectral response. The argument is that a reflection with a significantly different spectral composition causes greater subjective disturbance.)

https://www.hifinews.com/content/room-treatments


Anyone any wisdom or experiences to share?
 
I have floor-to-ceiling bass tube traps in all 4 corners of my room as well as fairly chunky absorbers adjacent to the walls at first reflection points. My primary aim was to tame bass rather than to suppress first reflections. From the calculators I have accessed I believe they provide meaningful attenuation from about 40Hz.

They seem to work very well - e.g. measured with REW and the spectogram shows rapid decay time for frequencies below 200Hz. Also a clap test in the room reveals the room is well controlled.

I would say be aware of any absorbers that are thin / flimsy as they will not work well other than to remove the higher frequencies. Here is a nice calculator if you are interested, you can use it to model the impact of a panel - front cover, absorbent material, rear cover and airgaps to wall. There are various tables published of common materials and flow resistivity. For instance my side absorbers are built up as (outside to inside) hessian cover > polyester batting 0.5" > fibreglass 8" > paper backing > air gap 8" to wall.

I found this is one of those areas where the experts disagree. From what I understand, for a domestic / non-professional environment the people who say it is not required focus on:
  • is a home environment not a studio so will have lots of furnishings e.g. sofas, rugs, curtains etc. So adding more absorbtion might be counter-productive and lead to over-absorbtion
  • someone placing absorbers of unknown specification in untested positions may lead to an unpredictable or undesirable outcome
  • to achieve studio-level of control you need to give up something like 25-50% of your room to treatments / absorbers, most domestic settings will not be ready for that
 
DIY. I followed am old recipe by Jon Risch. His site is long gone but can be found using the way back machine. Also some posts remain on tweakers asylum.

Essentially a hollow wire tube with 8" of fibreglass wrapped arround it, capped at both ends, then wrapped in polyester batting and finally Hessian. I can't recall the finished diameter, approx 18" I would guess, so not small.

Small financial outlay but lots of time and effort. I tend to enjoy this, turns a passive hobby into a more active one.
 
I may have misunderstood that post, but you refer to diffraction, which is the bending of sound waves around an obstacle. This is a new one to me, how would it work as side panels? Also the link claims the devices are diffusers. From my understanding regular spacing of tubes like they show in the picture would only diffuse a very narrow range of frequencies, if at all. And diffusers are not meant to absorb, only reflect.

I agree that sitting close to a back wall is to be avoided. Also I have read that diffusers cannot be effective if too close to the listener, e.g. 2m or greater gap is required.
 
I had a small room with lots of echo. Used corner bass traps and side panels, panels on the back wall, and also a ceiling panel at first reflection points (GIK).
Made a big difference. The echo basically disappeared. Even voices sound better in the room.
The bass traps made the biggest difference, but the first reflection points also helped.
I think several of the companies that sell panels will give you honest advice about what might work. My experience with GIK was that they didn't try to upsell me. Gave me 3 options of increasing cost, the cheapest option was the most basic and important.
 
I had a very noticeable & unpleasant “flutter echo” in my compact music room. GIK panels at the 1st & 2nd reflection points, as well as some high up at the wall/ ceiling junction cured this completely & definitely snapped the image/ focus into view. It was not a subtle improvement at all.
My thoughts are
Primarily place your gear, speakers & sofa as well as possible, then
Use acoustic panels, mainly bass traps & absorption &/or diffusion ( the difference between the two, & where to put them is another conversation) at the reflection points, & lastly
Try DSP, Dirac etc if you still need more adjustment.
 
I’ve used panels for treating first reflection points several times. They’ve always worked well. I’ve now got rid of them as I put shelving where they were. If anything it sounds better now but the new shelves will be diffracting sound rather than absorbing it. Acoustic treatment looks rubbish, in my view, and now the music room looks less like a studio, other family members sometimes even come in here with me. Bonus!
 
Not a room treatment as such, but...

My music room is a flat roof extension on the back of the house. It recently developed a couple of small damp patches so we've had the roof replaced and, while doing this, they replaced the insulation with some 4" thick blocks.

It has made a very noticeable difference to the acoustics of the room, especially to the bass - it's now far more detailed and spacious in the soundstage. Cost a small fortune mind you :(

You could actually hear the difference in the empty room - far less echo and resonance just standing in the centre of the floor.
 
I have a fully treated music room and can honestly say treating it was one of the best things i have ever done.

I did it with advice from GIK plus my own trial and error , ended up with....

all four corners with 8 stacked Tri Traps
front wall with 5 Monster range limited bass traps
rear wall with 5 Monster range limited bass traps and Alpha front plates
side walls combination of 2 full range and 4 range limited Monster bass traps
ceiling 6 242 panels

and it sounds anything but dead :).

Treating a room correctly involves having the correct type of panels , in the correct number and in the correct position. Obviously room use may dictate what you can do. By design my room was a dedicated music room so visuals not a limiting factor.
 
Room orientation also matters. I've found placing loudspeakers on the longer wall, equidistance between them and their respective side walls, and firing down the shorter dimension of the room helps.
 
I've never tried any professional or manufactured Acoustic treatment products in a room or measured frequency response I just use domestic furnishings and 'tune' by ear.
Generally starting with the system set up including LP storage (always sounds a bit bright) I then add voiles, drapes, sofas, armchairs, beanbags, footstools, cushions, rugs, tapestries and bookshelves , I try to keep things fairly symmetrical.
I'd like to hear the effect of some pro acoustic products but I'm cynical and sceptical as to whether the acoustic results would outweigh the aesthetic and the financial outlay.
 
... I'm cynical and sceptical as to whether the acoustic results would outweigh the aesthetic and the financial outlay.
This is a balance that every individual has to decide, same would apply to most things in this hobby. "Will the 10k amp improve over the 1k amp to a point it makes financial sense?" "Those speakers don't fit in with our designer decor".

Each to their own depending on their own priority and situation. But this should not be confused with are the acoustic results worthwhile - if done right, they are definitely worth it, I can vouch for that having come from a system in the lounge scenario to a dedicated audio / home theatre space. I would say the result is for me greater than any component upgrade. If you exclude the cost of building the dedicated space, then the cost of the treatments was maybe £200, plus my labour.

As for aestehtics of my treatments - actually mine are not pretty in the lounge decor sense - but in this dedicated space this is not really a major consideration for me. Functional over aestehtics.

In terms of a trial in your own space, one option I have seen mentioned is to buy some rolls of fibreglass insulation and stack them into your corners still sealed. I have not tried this, but it seems this is one way to replicate some of what a basstrap can achieve. Nothing lost in trying I would say, you can either use the rolls in your loft or return them to B&Q after you are done with the experiment. See here - do a search for "bales" on this page. Bear in mind these are not really basstraps but absorbers, and not great ones at that, but it might give an indication of the effect.
 
@rag987 I couldn't agree more.:)
I use Isover Akustic TP1, wrapped them in 2 large bags and put them in the corners. The effect is huge and it sounds way better than before.
 
But this should not be confused with are the acoustic results worthwhile - if done right, they are definitely worth it, I can vouch for that having come from a system in the lounge scenario to a dedicated audio / home theatre space. I would say the result is for me greater than any component upgrade.
My upgraditis stopped when I moved into my (then) new home with a purpose-built music room. In my previous house, where I went through umpteen source and amp upgrades, plus designed and built 10-pairs of DIY loudspeakers over a period of a dozen years, I was still never truly happy with the hifi. I now tinker at the edges just to experience a different flavour of hifi; not to better what I have.
 
Echoes my scenario. Did you use any acoustic treatments in the new space?
Not overtly. The wall behind the loudspeakers is acoustically insulated, and the room dimensioned to an optimal Louden ratio of 2.15:1:1.5.
 


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