I see one main problem: speaker impedance. The Magnepans have a 5 ohm nominal impedance. Most receivers, especially the lower-price models as you (and I) have are rated for a minimum of 6 ohms. Put plainly, these speakers will demand too much current from the amplifier and could cause shut downs, if not damage. This is one of the crappy things about Maggies, they
need outboard amplifiers or very stout receivers that can handle low impedances (which are nonexistent in the A/V world). Magnepans are known for their insane power needs. A thousand watts per speaker isn't outrageous for their higher end models (3.6QR and 20.1).
I have never heard the MMGW speakers, so I cannot express an opinion of their sound. However, given your budget, I think that you might be better served by standard dynamic (read: cone) speakers that offer a more managable impedance, greater frequency range, and higher sensitivity. While I am not an Axiom fanboy, you might want to consider their on-wall speakers. These speakers offer a wider dispersion and a more manageable impedance than the Maggies. However, they also come with a higher pricetag. You might also want to check out the offerings from companies like Definitive Technology, as I know they offer some highly-rated on-wall speakers as well.
Other concerns:
- Subwoofer Budget
- Projector Budget
The cost of $220 seems
very low for four 18" subwoofer drivers. This price leads me to believe that you have selected sub-par drivers for the project. In an IB setup you want to select drivers that can handle a lot of power, have high excursion, and have a low resonant frequency. I know of no 18" subwoofer driver that costs $55 that has good power handling, high excursion, low distortion, and a low resonant frequency. If you would like to make a high quality IB setup, I suggest that you opt for higher quality drivers (again, assuming from the price). This might mean that you cannot build the IB setup until a later date. In my experience, it is better to wait and buy something that is high quality the first time rather than spend more money playing the upgrade game. Obviously you will be driven to upgrade at some point, but you will get much more satisfaction from your system if you opt for higher quality components at the start. I understand that you are working with a limited budget (much nicer than mine, still). However, I think that you can achieve higher quality sound given your budget some adjustment of the allocation of monies. That brings me to my next item of critique, the projector budget.
The projector budget seems, to me, a bit out of proportion. If you are a videophile much more than an audio nut then perhaps the investment is justified. For me though, I would divert some funds from the projector towards improving things on the audio end. How much is acceptable is your call, but I think that you can sacrifice very little in the video realm and wind up with audibly better performance on the audio end of things.
Additionally, I think that you might wish to opt for a different subwoofer setup, especially if you are using "satellite" type speakers all around where the response is limited to 60-80Hz. An IB sub is best suited for the bass that is more felt than heard, that from about 30-35Hz on down. Indeed, the main reason that many people would install an IB subwoofer (myself included) would be to extend their system's response into the subsonic range. With a properly implemented IB system, 10Hz is easily attainable. What I'm trying to get at through all of this rambling is that you should be looking at subwoofers that are placed in the room. If you still want the IB sub to get ultra-low response, you can then use the attractive, compact, and low cost subwoofers on the market to fill the gap between your 5 speakers and the IB subwoofer. Ideally this implementation would use stereo subwoofers placed in the front soundstage. If you were to use a ported subwoofer with a relatively high tuning frequency, such as the Hsu STF-1 that is tuned to around 32Hz, you can get away with not using a crossover in the signal chain and simply use some EQ on the IB unit to achieve flat response and proper integration.
There are a multitude of possibilities out there, and they only increase in number as your budget does. I hope this has been at least somewhat helpful in your selection process. This process is never easy. By attacking the situation with a critical mind, ear, and eye, you will be able to build a high-performance, high-value system that should satisfy you for years to come.
