Originally Posted by gibsonm21
I am a car audio nut who is looking to make the transition to HT. I want to build a 7.1 surround sound system for my living room and plan on building from the ground up. I plan on testing out several speakers ...
1.... common chamber shared among all mid and high freq drivers...
2. ...Denon 4311 ...provide 120 rms/channel? ...600sqft. Is that power adequate for a room this size...
I am not looking for an IMAX/RPX experience,
Your plan to build from the ground up is good, but what do you have in mind for speaker testing? Are you serious about cloning the Focals you show, or is the goal equivalent sonic performance?
Here's the scoop. You can design a world class speaker yourself. But I guarantee your first speaker won't be world class, and it's up to your skill and learning ability when (and if) you get to the point where you can design at the world class level. Your first $200-500 expenditures will be for test equipment, and you'll need to find and understand the several measurement threads before you start driver selection. Then you can start on the speaker design books, so you can understand the speaker design threads...
Or you can use available data to choose drivers, and look for a "proven design" using those or comparable drivers. Here's the master list.
If you choose a proven design, there are two things to look for in the design family.
- is there an on-wall/in-wall design?
Any speaker placed near flat surfaces, like under a TV screen, will sound boomy if not designed for that location.
- is there a center channel design?
Center channels have unique program content (i.e. dialog) and so benefit from voicing for dialog intelligibility.
The ideal option if you want to hear a lot of different drivers and speaker designs is to attend a DIY event. There are a bunch around the US.
As to your questions,
1 has been addressed quite well.
2 is personal taste.
Adding 8' ceilings, you have 4800 cu ft. to fill - big room. Easy to have 4 meter speaker distances, but you'll also have 7 speakers. Distance costs 6dB every time it doubles, so you're -12dB at 4m. But, a second speaker doubles cone area (+3dB) and doubles amp power (+3dB), and you double speakers 3x so you're +18dB with 8 speakers. Note all this assumes direct sound field only; the reverbrent field will be a major contributor, so we can safely say: "Loudness at your listening position will be approximately equal to the sensitivity of the speaker x power applied."
A 140W amp adds ~21.5dB above 1W, If you want to achieve 105dB SPL at your listening position, you'll need speaker sensitivity greater than 105-21.5=83.5dB@1m, 1W. Practically, aim for 85-90dB sensitivity and you'll find reference levels are within reach. You will be adding subwoofers, right?
I will note that none of this is cabinet design theory, which I see stretching from how to build a dead box to unique cabinet designs (eg. dipole, band pass) intended to achieve specific objectives. Slanted baffles, angled baffles as you show, all have deisgn goals. In many cases, the major goal being to "look good" as it's well known that pretty speakers sound better.
Thus, the caveat that fancy cabinet design theory may influence your opinion of the sound, even if it has no sonic effect whatsoever. Beauty speakers sound better... but only if you can see them.