I had an interesting experience over the holidays … we have two fabric covered deep cushion settees located in opposite corners of the socialising end of the big living room, the hifi end is the other end. Anyway room details aside, we moved one settee to accommodate the christmas tree leaving that end corner with just the tree. I fired up the Naim whilst fiddling with the tree & had to turn it down, working around that area was most unpleasant in both body & ears. The opposite corner with the other settee that was the same distance to the speakers was completely comfortable. After the tree was removed & the settee replaced, pleasant tunes were resumed.
So moral of the story, Ercol make exceeding good bass traps - a bit expensive though.
Hi Ardberg,
I think there is a general misconception, that full bookcases has an ability to absorb low frequency. As you have found the pressure wave simply moves around them with no reduction in amplitude. I am sure that they will however soften high frequency reflections, however at an unpredictable frequency range. The beauty of a professional diffuser is the rate and level of reflection has been measured over the whole frequency band to ensure, that it is actually maintaining a predictable outcome. I am myself at the moment playing with QRD diffuser in my room from Bluetone in Poland- beautifully manufactured and very effective. I thought that I knew, where they were expected to go ( front wall), but am in the end using them on the side walls, where the most prominent high frequency reflections are. In this way I am keeping the listening end live yet diffused. As always the implementation of acoustic treatment takes a lot of experimentation, which of course is highly rewarding, when you get to appreciate the improvements achieved, as you go along ATB Peter
Unfortunately, books shelves, CD shelves, curtains, rugs, etc. won’t have any effect on frequencies under ~1kHz (which no effect at all on low frequencies).
For frequencies above ~1,5 kHz, furniture might have some absorbing effect, but nothing fantastic.
Not fantastic but quite noticeable! Our hearing system is extremely sensible to frequencies between 1kHz and 3kHz.
As for sound diffusion, furniture won’t diffuse sound. It simply doesn’t work that way. Diffusion has a very specific meaning.
Low frequencies absorbing material (under 300 Hz) :
- Glass fiber and Rock-wool
Medium to high frequencies absorbing material (above 300-500 Hz) :
- Acoustic foam and, of course, Glass fiber and Rock-wool
Sound diffusion is achieved with panels built with a very specific geometry based on mathematical sequences, as @PeterR mentioned.
I’ll post some reliable information sources next week. Don’t have much time right now. To much work and a lot of training (climbing projects).
A good source of information (and very interesting reading) :
For completeness of information, mathematically designed diffusers are to ensure evenness of effect. Other uneven surfaces will also have a diffusing effect, though likely less and less evenly spread over frequency and direction. E.g. a bookcase packed with varying sizes of book, randomly arranged it terms of height, and not having their spines aligned, and have quite effective, diffusing capability, though combined with some absorption varing by the hardness of the spines, again random over the area. A bookcase full of identical books neatly arraged with flush spines would give far less diffusion, though if the spines are curved it nevertheless could be significant, albeit only in the horizontal plane.
Thomas, I seem to recall to have asked you for some pics of your lovely room , ie listening end? ATB Peter
See above. Was already posted.
I’m prolonging the suspense
It needs some housekeeping at the moment. My young daughter rules the central rug, no way I can move her playground back to her own room
I’ll take some pictures by the end of the week.
In the meantime I’ll let you imagine:
- 9 x : Vicoustic Multifuser Wood 64 White
- 2 x : Vicoustic Multifuser DC2 white
- 26 x : Vicoustic Cinema Round Premium
- 11 x : GIK Monster Bass Traps (custom sized)
- 4 x : Vicoustic Super Bass Extrem
And Streamer Pro acoustic veils (high performance acoustic fabric, designed in Switzerland).
Those veils were my first step into acoustic treatment.
I have serious doubts about this statement.
The room that houses my main system, from which I have hung several photos in the System Pics thread, is a room that has always been difficult to balance the sound, especially in the low frequencies, but due to the lack of them, since the room modes have always tended to prevail the high frequencies, so it has been very difficult to correct the always brilliant sound.
In this room I have tried different systems, with several standmounters (Dali, JBL) and up to 4 different pairs of floorstanders (Q-Acoustics 2050i, Totem Wind, Pulsar Audio Ambient D7 and finally ProAC K6). Well, with the room minimally conditioned with 8 EZ- Acoustics acoustic panels (basically oriented towards the absorption and diffusion of high and medium-high frequencies) and the quite complete furniture and decoration, all the systems have been bright and harsh…, until the K6 were introduced, which with Exposure amplification and without any other room alteration, were unbearably fat and boomy. Finally, with the current amplification, with a fantastic synergy with the speakers, the sound is perfect, organic, neutral and balanced throughout the range, with tight and nuanced basses, crystalline, silky and velvety mids, and extended treble but without any drop of harsh.
Conclusion: room treatment is important, sure, but most importantly, in my experience, it is suitable speakers for the room and, above all, a good balance and fit between all the components of the system, including the room, of course.
Nice record collection!
Unfortunately, in terms of diffusion, in won’t do much.
It’ll absorb some high frequencies (probably above 2kHz).
Here is chapter 5 of the book (fourth edition) I mentioned above.
It might provide some comprehensive info:
http://serra.se/diffusion.pdf
Hope it helps
In terms of actually listening to music, it helped quite a bit actually. But thanks for the reference.
I completely agree with you. Better adapt the speakers to the room than the contrary, if possible. If the speakers are well chosen, the acoustic treatment will be easier. If not, the room will look like as an anechoic chamber and the sound will lack live, because too much damped.
I am more for minimum acoustic treatment personally.
Perhaps I was not enough clear, after having read me. If you choose the non accurate speakers for your room at the beginning, you will have a lot of acoustic treatment to do after, which is , from my point of view, not ideal.
If a room is acoustically a problem, then whilst you might be able to find speakers that sound good in the room, they will never sound as good as good speakers in a good room. As Xanthe illustrated, you can avoid bass resonances … by avoiding bass. You can tame an overly reflective room in the high frequencies by using speakers with subdued treble … but the reflections will still be there as the same proportion of the same frequencies, and early reflectins in particular will muddy the sound,
So really, getting an acoustically good room should be highly desirable for anyone wanting the best sound quality. And if you have a good room you can choose soeakers based on how good they sound, rather than how well they minimise the negative effects of the room.
All that said, some speakers work better in a wide range of rooms than others, I have heard my old IMF TDL50ii speakers in 9 different rooms - and none were anything other than good sounding, albeit some better than others. My more recent but older IMF RSPM speakers I’ve heard in 6 different room, all sounding good apart from initially in a very awkward room, until analysis by REW showed where to place both them and the listening position. BUT I also heard them not in a room, and there is no superlative good enough to describe how good they sounded… That is what room treatment has the potential to approach: removal of the room.
Great post IB, what you are describing is not much different to, when I open my Bifolds behind the speakers fully. This is what I am currently using as my reference point, I’m sure much to the delight of my next door neighbour in the hope, that he likes Matt Baxter. ATB Peter
That’s so very true.
Nice post!
Unfortunately, the room is always a problem
I use the exact same method, specially when I seek clean and detailed bass.
It is a good trick btw : opening doors and windows relieves acoustic pressure and therefore allows better low frequency response.