Indeed. The listening room. They say it's better if you build your house for your hi-fi, rather than vice versa .
However, it can be assumed that you choose the system given your listening rooms properties. It's part of the choosing process and doesn't necessarily affect your budget ratio, but indeed it may rob you from otherwise good speakers, and if you want them, then indeed we need to factor in the room treatment costs. Is that included in the speakers' cost?
However, there are some simple and often cheap rules (*) for choosing or treating the room and placing speakers. One of my friends managed to fix a really bad room pretty well with smartly placed and quite decorative acoustic panels, all DIY so it didn't break the bank.
(*) There are a multitude of links for this, but to summarize some:
Two common examples for optimal (modal) room dimensions: 7m x 5m x 3m (large) and 6m x 4m x 2.6m (medium). The latter is quite common living room size here and the room height of 2.62 presents a thermal+physiologic optimum (ventilation systems are mandatory here). Also, quite often the ceiling is slanted, following the roof.
In my experience, the best sounding structure is a log house. When I took my system into a Honka log house, I was amazed by the difference. Next, sandwich structures. Next, light structures. The worst: concrete cubes.
When it comes to room treatments, I use mainly bookshelves and draperies for "acoustic treatment", plus some panels (wood + wool felt + wool structures).
I place the speakers at the 1:1.6 dividing line (more into the room as usual), if possible on the wide side, and make the listening triangle from there, so that there is room behind the listening point as well. This gives an almost near-field experience with very good sound stage. BTW it's the same what John Dunlavy and Audio Physic advised for setting up their speakers.
Why is this relevant in a headphones forum? Because I think it's worth having a speaker system besides headphones, and as such, will influence investment ratios
1. No headphone, not even the HD800(S) has sound stage anything near to that of properly set up speakers (at least with small chambers, jazz, instrumental, and symphonic). For rock, pop, hiphop etc headphones are just fine.
2. No headphone has anything near the bass energy shaking your body cells that comes from a good speaker system.
3. It is healthier to listen to speakers than to headphones.
There are also good reasons why to have a headphone system besides speakers.
1. Quality/price ratio.
2. Lack of room modes. Headphones are tonally more pure, exactly because room acoustics, even in a near-perfect room.
3. Less disturbing to others, more intimacy. When I have a choice, I use the speakers. But in the office, for late night movies, and for evening listening (children sleeping) headphones are a necessity. That leaves me listening to speakers about 10-20% of the time... and the speakers + bass modules + subwoofer + amps cost way much more than my headphone systems (Stax and dynamic).
Finally, we can be grateful that our biggest problem is to discuss how to spend the money well on audio reproduction... ...
. I feel guilty.
OK, no more off-topic