Bleeding blood or bleeding money? It sounded like a little (lot?) of both. I just get a kick out of how you tell your story. I would have thought you could have got those 37000 holes in that tube if you really wanted to:-)

I have never looked in a M200 since I don't have one, but I would think it would not take much to follow the trace from the input. My guess is it is the first component that the input connects to.

As that one link above to hometheaterhifi stated at the roll off is where you have the phase shift, so if you move the cutoff point down, the frequency where you have phase shift would also be moved down.

The impedance of a cap at a frequency f is Xc = 1/(2*pi*f*c). At the 3dB down point the impendance of the cap is equal to the input impedance of the amp itself. The M200 has a stated input impedance of >10K ohms. So at 5Hz that would give a cap of about 3uF, my guess is there might be a 2.2uF cap on the input. Switching the cap to a 4.7uF should cut the 3dB down point in half.

I could be all wrong here too. I am guessing without seeing a schematic or looking in a unit. If there is a cap, and you know for sure that your preamp has no (zero, nothing, nada) DC offset, then in theory you should be able to replace the "cap" with a wire. But don't hold me to that:-)

And anyone out there that is a bigger EE than me, you do not need to go off on me.

That you won't want to miss Part 5, in which events take something of a turn for the worse.

http://users.net1plus.com/scottm/room.htm

Ouch. That's highly irritating.

I took particular note of your HVAC problems while reading part 5. Like you, home theater is a hobby/obsession of mine, but my day job is mechanical engineering - specifically the design of large commercial HVAC systems. Maybe I can help you scheme up some solutions that will at least be difficult for your contractor to dismiss.

You've got a 700 SF room, which in a commercial space would probably get a minimum of 550 or 600 CFM (cubic feet per minute) of air - which would equate to a 12" supply duct. That's commercial work, though, and we have a lot more to deal with than you find in residential work, so that's too much for any residential installation. Your 10" duct should be able to handle up to around 375 CFM, which seems reasonable for a residential application. You could probably even cut back a bit more since there is so little exterior wall to contend with (judging by the unusually high window, I'm guessing that the one exterior wall is more than half buried). Your lighting is on dimmers, and dimmers make good space heaters, so if they are going to be in the space they will introduce heat that isn't currently present. Likewise, your solid state amps will put off some heat when in use. How much heat is a matter of some debate - I've researched amplifier heat gain in the past, and found that nobody really knows much about it. Obviously, if the equipment rack and dimmers are remotely located (tucked into an adjacent room), then they aren't going to contribute and you'll have very little load to worry with. If either the amps or the dimmers will be in the room, I'd stay with the 10" duct just to be sure - dropping to an 8" will cut your airflow capacity nearly in half.

One thing that I have had to do countless times is try to squeeze ductwork into a ceiling that has been designed to have a specific aesthetic impact without taking into account my ductwork. That's something that residential HVAC contractors rarely have to deal with (like your wiring, some of the stuff I've had to come up with over the years would be classified as "weird" or worse). It can be something of an art. From your notes, it sounds like the contractor plans to leave his intake (or the "return") where it is and shift the exhaust (or "supply") away from it - not a bad idea at all in a space that big, as it would be pretty likely to short-circuit if they are too close together. Your suggestion of hopping into the joist space to get to the soffit is an excellent one - not only will it allow you to retain the ceiling design, but the extra bit of duct and extra fittings will help attenuate some of the fan noise. Once you get to the soffit, however, I would recommend a grille in the bottom of the soffit. Air will always find the path of least resistance, and I suspect that the fiberglass and fabric will offer a great deal of resistance. A residential AC unit's fan is probably not up to that challenge. One grille in a room that big is far from ideal air distribution, but as you say we are dealing with a residential space with a modest load - it should be sufficient for your needs.

If you are really concerned that the supply is oversized or just want to be able to cut down the airflow later to reduce grille noise, you might want to consider trying to get your contractor to give you a balancing damper in the duct as close to where it enters the ceiling as possible (thus making it as far from the supply grille as possible, which allows the ductwork to attenuate any turbulence noise generated by the damper). We occasionally have to put balancing dampers above inaccessible ceilings such as yours, and there is a fairly simple product made by a company called Young Regulator that helps avoid the need for an unsightly access door. They have a product line called the Bowden cable controls ( here is a PDF file on the product). Basically, they stick a damper in the duct, and in place of the handle on the side of the duct they take a cable - similar to the cable on a kid's bicycle speedometer - and run it to a knob on the wall or a small key-operated disc in the ceiling. This way you can adjust the damper position without having to touch the duct. Page 8 in the PDF shows the ceiling control as it would look in your case. It's not something I would consider necessary in a residential installation, but it is an option that might be worth considering...

This ended up being longer than I'd anticipated (and luckily I saved it just before my cable modem took a break last night). It may have created more questions than it answered, but if you want to continue the discussion outside this thread, just PM me .