I've got these questions sent to support, but this might be faster...

I'm considering using an M-200 to power a subwoofer (4 ohm VMPS Larger). Anyone know where the -3db points are on tne frequency response for these amps? Anyone know of any problems driving them down to 10Hz?

Anyone know if it's possible to take two of these and strap them in parallel?

People have mentioned transformer hum. I plan to give this thing a dedicated 20A line, which ought to be more than it will ever eat; but the same subpanel is supporting several other high current amps, and a 2400W dimmer. If they are prone to hum I need to know that - I get real grumpy if I can hear hum. (I'm selling off an Earthquake Supernova sub because the blasted transformer isn't silent.)

How's reliability under load? One thing I use a subwoofer for is acoustic tests - blasting a room with 110db at 30, 50 and 70Hz for many minutes at a time. Any issues?

How long is the warranty?

Thanks!

The power output specs cover 20Hz to 20,000Hz, but that doesn't tell us anything about how much lower or higher it is capable of going. I'm not sure about the parallel configuration. Presumably you are splitting the input signal to both amps, then connecting both to a single driver. I'd definitely want Outlaw to sign off on that before doing it, as it is not the way they are intended to be used.

Are you really putting a single amp with a max rated power consumption of 600W all by itself on a 20A circuit? A 15A circuit offers three times as much power as an M200 could use at peak output. As for hum, all I can tell you is that the two M200's in my system have never exhibited any hum.

There have been a few other folks who have used M200's to drive subs, so there may be some older threads (or some other forum members) that could offer some thoughts on frequency response and load handling.

Warranty is five years, and it is transferrable if you sell it during that time.

Does it cover picky minor complaints from fanatics?

Read your room story - woah! Suddenly, last year's kitchen renovation seems almost painless. Wow. When it's all done, I'd be interested to see some pictures of "The Room." I suspect that Outlaw can track down some more detailed specs on the M200 for you.

Not sure about actual numbers but I have a test CD that runs tones down to 15 Hz and the M200's will vibrate things at that frequency (Its actually kind of fun to trip people out with this, they don't understand why the can feel it but not hear anything). As far as hum is concerned, I have 10 of the M200's on two seperate circuits and they are totally quiet. Initially they would hum (which drove me crazy) but I was able to trace the problem back to my satellite dish not being grounded to the same spot as the rest of the electrical system. Move the ground and no more hum, ever.

Apparently I'm the first guy to ask for frequency response data. They are trying to dig some up. They *must* have specified some minimum requirements when they asked for designs, right...?

There are pictures of the room, very much unfinished, at zip of pics - finished will have to wait a few more weeks. (mutter)

This article may help some.

http://www.hometheaterhifi.com/volume_10_2/outlaw-audio-200-amplifier-4-2003.html

Hm. That does help. That's info that Outlaw Support didn't have...

Ouch. Down 1db at 20Hz, 2db at 14Hz. That's a little steep...

ScottM, please update your story soon. It was fun reading:-)

I would think you could modify the M200 with a different input cap to lower the rolloff of the low end. I know it might end your warranty, but that risk might not be that big of deal when you look at what you have into the whole deal so far.

Just a thought.

Fun? FUN?! I'm bleeding here, dude!


I would think you could modify the M200 with a different input cap to lower the rolloff of the low end. I know it might end your warranty, but that risk might not be that big of deal when you look at what you have into the whole deal so far.

Hm. I don't know how to calculate rolloff, but just "bigger cap" might work. Or will that phase-distort? I don't suppose Outlaw publishes schematics?

Note to Outlaw if they're watching: follow Aragon's example and let your amps go down to 5Hz flat, as that's quite useful in HT. Or Bryston's example and go down to 0.5Hz, on the grounds that you can never, ever be too flat. Or just put in a switch labelled "DC limiter" that folk with well-behaved preamps can flip off...

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 .