I have opened this new thread to describe the acoustic transformation of my primary listening room.
Room influences and issues of colouration have been discussed at length else where.
The intent is not a blog but to oultline some of the issues I have in my room and the practical measures that I have decided to implement and the reasons behind the treatment..
Everyone’s room is different and in no way is the information discussed here to be taken as a solution for a generic listening room.
There are hundreds of references in the www and consultants eager to discuss your specific needs.
Background.
What started this off was an email response from an associate when I was enquiring about building a parametric equaliser. And my question was would it help with room modes below 300 hz as I can hear some clouding of the midrange on certain types of program material. It varies with listening position
The response was:
Theprimary purpose of the equaliser is to linearize the frequency characteristic of the loudspeaker. Optionally and less advisably, it may also be used to correct room response. However, where the room effect is particularly pronounced, there is not much the equaliser can do to fix the problem. In such cases, a proper acoustic treatment of the room (with respect to standing waves and reverberation time) will be required to improve the overall listening experience. For instance, if we wish to adequately suppress the standing waves effect of the listening room, we may have to use acoustic elements (such as diffusers, provided that the reverberation time is OK). The main problem with this approach is that it requires significant room adjustments, which may be rather costly, have low WAF and still not guarantee a perfect result.
So I sent some diagrams and some photos and we looked at the basic issues of the room and how to deal with them. The inside of the Tardis is particularly boring although it is dimensionality transcendental . So sorry no pictures.
A quick analysis reveals that the distribution of your room modes is such that it should not impact the sound of your system audibly/significantly in the centrally placed listening-chair position. For illustrative purposes, I have modelled your room as a 4-metre by 4-metre square room with parallel walls. Picture 1 shows the axial mode at 86Hz. The blue lines in the picture represent standing wave minimum’s whereas the red lines are standing wave maximums. The crosses are critical (worst) listening positions.
At 86Hz, the critical listening position is the centre of the room. At a frequency of about 175 Hz, you have a standing wave minimum intersecting with a maximum at the spot where your middle chair is positioned, which should not pose any listening difficulties. However, the neighbouring two seating/listening positions (i.e. the chair on the left and the one on the right) are compromised because they happen to be at the intersection of two standing wave minimum’s. Likewise, at circa 258Hz things look pretty good at the middle-chair position as there are no standing wave collisions there. Again, it is the other two chairs which are in sub-optimal listening positions because they are relatively close to the standing wave maximums.The above are only case studies for the three most important axial modes and they should be taken with a pinch of salt because other room modes may also have an impact to a certain degree. Having said that, I do believe that in your case room modes may be corrected by the right placement of the speakers against the rear wall. Thus, if you pull them away from the rear wall by 20 or 30 centimetres, you may be able to reduce standing waves at critical frequencies.
As I see it, a far more serious issue here is the room's reverberation time at midrange frequencies (the most critical band to our ear), which is too long due to lots of bare spots on the walls and a number of glass surfaces. On top of that, I suspect you may also have a problem with the so-called "early (or first) reflections" bouncing off the side walls, glass windows/coffee table, TV screen and the rear wall (paintings), which must be avoided as they can obscure the sound quite a bit, imaging and clarity in particular.
I've been told that acoustic engineers make appalling interior decorators but here's what I'd do with your place just in case you ever feel like living on the edge :
Put a 1.5-metre by 1.5-metre diffuser behind the TV set.Mount another diffuser onto the rear wall above the bookshelf, covering the entire width of the rear wall.
Diffusers are used to reduce early reflections and reverberation time (to a certain extent).
The ideal position for the paintings is to the left and/or to the right of the front diffuser (i.e. the one behind the TV set).
Put some absorbers onto the left side wall above the bookshelf. They should be 1.5 metres in width and 1 metre in height.
Hang some drapes (heavy curtains) to cover the windows and the balcony door.If required, put bass traps in the front two corners of the room.
I believe these room adjustments would make a significant difference to the quality of the sound you hear, particularly when it comes to the midrange band which is currently greatly troubled by reverberation, reflections and all kinds of resonances.
If you decide to have a go at this, there are some good web sites about how to build your own absorbers and diffusers plus a few tips of my own that I'd be happy to share with you.
Well that was a lot more than I expected.