You're welcome - and thanks for the kind words!
Ported speakers do tend to sound best when they are out, away from walls. This has more to do with room acoustics than it does with the actual speakers themselves though. Axiom themselves say that the M80 and VP180 speakers REQUIRE only 2 inches of space behind them - that is to avoid actual noise from the air rushing out of the ports. But most people will find that a good 2-3 feet is preferable.
Now, before that cause you to worry, here's what's going on (in a very rough and unscientific sense
). Lower frequencies audibly interact with the room. The longer wavelengths reflect off of the walls and interfere with the direct soundwaves that are coming out of the speaker as well as the other reflected soundwaves. Sometimes, two peaks meet up and create a big spike, sometimes one peak and one null will meet and sort of "balance" eachother out. And sometimes, two nulls will meet and create a big "suckout" at that particular frequency. The end result is that - at your listening seat - you get these big dips and peaks in the frequency response. The speaker itself might be putting out a nice, flat frequency response, but due to the reflected soundwaves off of the walls, the direct sound of the speaker and the reflected sound off of the walls combine to create a frequency response that is all bumpy and jagged.
Soundwaves get weaker and weaker over distance, so conversely, when you have speakers closer to a wall, you get stronger reflections.
So the worry with ported speakers is that - first off - they tend to play lower frequencies more strongly than similarly sized sealed speakers; and secondly, soundwaves come out of that port - so with ports on the back, you have some sound coming directly out the back and immediately refelcting off of the wall that's behind the speaker.
So, long story short, speakers that have rear ports and can play quite low - like the M80 and VP180 - they tend to sound better the further you move them away from the walls. That way, you get weaker reflections and fewer and less extreme interactions between the direct sound and the reflected sound.
Here's the good news though - all that really matters are the strength of those reflections. So if there is some other way of cutting down the reflected sound, using a ported speaker isn't really any different than a sealed speaker. So what you can do is to simply put absorptive material on the walls behind and to the side of the speaker. What you want is something that will absorb those lower and mid-bass frequencies so that they do not bounce off of the walls and cause interference. ie. a bass trap!
So this is taking us into some new, but very important territory - acoustic treatments. Many, many people sort of put off treating their room. They look to the speakers, the amps, the players, maybe even the cables in order to try and glean improvements. Let me tell you, the single greatest thing you can EVER do for audio quality is to acoustically treat your room! Audio reproduction is a system. And, as wtih any system, the hope is to create something that is more than just the sum of its parts. The room is a CRITICAL part of that system. Take the exact same speakers, amps and player from one room to another and they are not going to sound the same!
Anywho, if you are going to be placing speakers such as the M80 and VP180 fairly close to any walls, there is nothing "dangerous" or "wrong" with that. You simply need to be aware that you will be getting stronger reflections and act accordingly
I'm a big, big fan of GIK Acoustics - gikacoustics.com . They make simple, effective, good-looking acoustic treatments at extremely affordable prices. Literally, you would barely save any money if you were to buy the materials and make your own acoustic panels! GIK's products really do cost about as little as possible - I honestly sometimes wonder how they manage to make any profit at all!
What I would recommend is that you have one of their 244 bass trap panels directly behind each of your front speakers. It's most important to have the panel covering the wall at ear height, so even though there may be a port at the bottom of the speaker, do not worry about that - have the bass trap panel up 2-3 feet off the ground - this looks the most aesthetically pleasing as well
Other than that, the "standard" placement of acoustic treatments would still apply. The idea with home theater sound is to have very direct, clear sound from the front, but diffuse sound at the back. The sound from the front is meant to "wash over" you and then "disappear" behind you. So the way you would normally deploy acoustic treatments is as such:
1) Place bass traps in all the vertical corners of your room. You can go floor to ceiling, but the most important locations to bass trap are the wall-wall-ceiling corners...worry less about treatments down low.
2) Put absorptive panels and/or bass trap panels on your front wall (the "TV wall") behind your front speakers. This prevents the strong reflections that muddy the sound coming from the front.
3) *Very important - place absorptive panels on the side walls and ceiling at the first reflection points. The first reflection points can be easily found by sitting in your primary seat and having a second person hold a handheld mirror along the side wall. Wherever you can see the speaker in the mirror is a reflection point. The first reflection point is the area on the side wall and ceiling where you can see the speaker in the mirror that is closest to the speaker (again, stronger reflections at shorter distances).
4) Place absorption directly behind your seating location. This stops the sound that is coming from the front speakers from bouncing off of the wall behind you. Remember, the sound is meant to "wash over you" and then "disappear". Sound reflecting off of the wall behind you is the #1 cause of dialogue being hard to understand. I saw that in your diagram, you couch is very close to the back wall. If possible, try to bring that couch forward so that there is more space behind your head. Even just 1 or 2 feet can really help! And with such close placement of the couch to the back wall, it is especially important to put some absorption directly behind you. I think you will be surprised at how big a difference it makes in your ability to clearly hear dialogue.
5) Treat the rest of the back half of your room (side walls, ceiling, back wall) with diffusors. Diffusors "scatter" sound. So instead of direct reflections or the sound disappearing into absorption, you still get all of the sound energy, but in a more random, scattered and diffuse way. Your surround speakers are meant to create ambience and a sense of envelopment. They can best accomplish this if the rear half of the room aids in scattering and "spreading out" that sound.
That's it! That's all there is to room treatments (well, not ALL, but those are the basics that will serve almost any listener very well
).
What's fantastic about GIK is that they not only offer very effective, very affordable products, but they also offer some really decor-friendly options if your significant other isn't a fan of solid colors on the walls. GIK offers their ArtPanels, which can literally take the place of paintings or posters on your wall while giving you SO much acoustic benefit. GIK also has very nice-looking pillars and small tables that act as bass traps. If you don't want a Tri-Trap or 244 panel straddling the corners of your room, try putting a Pillar Bass Trap in each corner with a nice plant or vase or other decoration on top. Instant bass trap PLUS great decoration!
