So, Jon and I have been curious about how much of our system response is due to the electronics/speakers and how much is due to the room. In the previous post, you can see that there are a number of spikes and nulls in the response. The room correction filter helps out a lot. However, we were wondering if we could put our system in an anechoic chamber and see the same (nearly same) response.

I posted a question on the Digital Room Correction mailing list and a user named Gregory Maxwell said that most of the response was due to the room. I wanted to put this to the test so I took prototype VI out on my deck for a test.

Bottom Line: Greg was right, most of the nulls and spikes in the response seem to be caused by the room.

Here are a couple pictures of my setup and a screen capture of the responses in Audacity.

Setup. I live on a hill above a lake. My deck is about 12 feet off the ground. From its corner, there is an unobstructed view to the lake. The closest possible reflector is more than 50 feet away and even at that, there are numerous bushes and other 'diffusers' to cancel echoes. I brought my lab computer, bench power supply and the amplifier (TAS5504+TAS5142) to the deck. These are the same parts I use in my lab for previous measurements. Unfortunately, my neighborhood is not very quiet. They are building a house down the block from me (hammers, power tools, ..etc). Cars drive by all the time. The landing pattern for the local airport goes over my neighborhood. Finally, the city seems to just generate a dull/low hum all the time. I have left some of the ambient noise on the end of the traces below so you can get an idea of its magnitude
Setup from Below. This is a picture from the yard below my deck. It gives you a good prospective on how free/clear the area is in front of the speaker.
Microphone. I attached the Behringer ECM8000 microphone to the end of a broom handle. I then asked my wife to hold it about 1 meter directly in front of the speaker while I conducted the experiment (sorry, no pictures of her doing this. We were both too busy.). Of course, this is not very precise but I figured it would be good enough to get a gross sense of the response outdoors so I could compare it with the indoors response. She tried her best, but she was not able to hold the microphone perfectly still. So, as she 'wobbled' it back and forth (about a 2 inch movement), I am sure it effected the response. Next time we get a sunny day (no rain), I will take the time to build some fixed mount for the microphone.
Response. The top trace is the logsweep. The second and third traces are typical recordings done in my lab. The fourth trace is a typical trace done outside. As you can see, many of the nulls and spikes are gone. The spike at 3000Hz (about 33.5 seconds) is our midrange to tweeter crossover. Our woofer to midrange crossover is at 200Hz (at 17.5 seconds) and is really not visible. The 300Hz null (at 20 seconds) that has always been present in the recordings I did in my lab is gone. This is strong proof that the 300Hz null is just a natural dead spot in my basement lab. O... notice that the trace is very noisy. Not much I can do about the noise in my neighbourhood.