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Multi-Way Conventional loudspeakers with crossovers

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Old 14th April 2010, 01:56 PM   #1401
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Old 14th April 2010, 02:16 PM   #1402
gedlee is offline gedlee  United States
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I'm not about to write a thousand words and even a picture takes more time than I have at the moment. I leave for China tommorow and am quite busy.
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Old 14th April 2010, 02:27 PM   #1403
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Summing up the time it took you to write all those "I don't have the time" posts easily exceeds the time required for taking a picture ot labeling your diagrams or ...
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Old 14th April 2010, 09:44 PM   #1404
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Thanks Dr. Geddes for the explanation.

Good luck in China,

Dan
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Old 22nd April 2010, 04:12 PM   #1405
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So here's the polar graph of my current design starting at 11.25 degrees off center, in 11.25 degree steps out to 90 degrees:

Click the image to open in full size.

Modeling the low end gets bass to 100Hz.

Now here's what the room does to that response:

Click the image to open in full size.

The mic is placed at 5 spots across the couch. So this is the average room response at the listening position(s). The bass boost on the receiver is turned up a bit or else that 200-300 Hz floor bounce suck out makes it sound too light. Both ends of the couch have a pretty smooth response, and the middle has the most bumps. Anyone care to comment on what going on with all the variation?

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Old 22nd April 2010, 04:53 PM   #1406
Pano is offline Pano  United States
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Originally Posted by dantheman View Post
Anyone care to comment on what going on with all the variation?
Sure Dan. Since this is near and dear to my hear at the moment, I'll jump in. May get a ton of flack for it, but here goes:

Measuring in-room response with an omni-directional mic is just wrong.
I can see the omi's usefulness in free field or anechoic conditions, but not in room.

Why?

Because your ear is not omni-directional. It's closer to a supercardioid pattern, as best I can determine. I've spent a lot of time searching for polar response patterns of the human ear, and they are darn hard to find. (Need to go to the library). But the few I have seen look like a supercariod mic pointed about 55 off axis.

If this is the case, then an omi mic is going to be picking up a lot of room reflections that your ear will not. Or at least picking them up a lot louder from the rear and front than your ears do. We do have 2 ears (most of us) but we can at least get started right with the proper mic pattern. One that is closer to what the ear picks up. And not a mic that picks up an equal amount of reflected energy from all around the room. Ears don't work like that.

So very recently I've taken to measuring and EQing with a cardioid mic pointed about 52 off axis.. I have a cardioid and and a hyper-cardioid, but no super, so I'm making do. Still, for me the results have been much better.

Using an omni at the listening position and getting the FR flat or even with a bit of top end roll-off just never sounded right to me. Using the cardiod pointed off-axis had been much, much closer to how I would tune the system by ear.

This is a new approach for me, so still fine tuning it. But I think it has some bearing on your "at the couch" response curves. If you're using an omni mic, it's picking up a lot of stuff that your ear does not.
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Old 22nd April 2010, 05:09 PM   #1407
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Pano, can you post some graphs of the difference in the same position?

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Dan
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Old 22nd April 2010, 05:26 PM   #1408
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Old 22nd April 2010, 06:29 PM   #1409
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Originally Posted by panomaniac View Post
Because your ear is not omni-directional.
Luckily, most of us have two ears......

When I listen to a mono source and turn my hear around, the frequency balance dont change all that much - our two ears together are virtually omni.
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Old 22nd April 2010, 07:05 PM   #1410
el`Ol is offline el`Ol  Germany
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My rooms are extremely reverberant with almost as little HF absorption as possible - there is always some in any real room. The area behind the speakers is heavily absorptive, but nowhere else. The ceiling has a difuser and the floor has a patch of absorbtion right at the first reflection point, but otherwise the floor is wood. Two walls are stone (irregular so as to difuse). Then using 90 degree CD sources and pointing them such that the first side wall reflection is avoided, yields a situation where the direct sound has a maximum possible reflection free time before the onset of reverberation, and then the reverberation is quite pronounced and almost exclusively from the sides and rear, which is well known to improve spaciousness. This situation yields excellent imaging and very good spacial aspects - these two things usually being mutually exclusive.

Wide directivity speakers and non-CD speakers in a room like this do not sound very good and as such no one else makes rooms like this. Its quite uncommon.
Thanks for that post, Dr. Geddes. I had started thinking that you see your CD-waveguides as a thing of their own or just as an intellectual challenge. Time to withdraw my threadjacking accusation.
Do the axes of the speakers hit the side walls or the rear wall? And what is the difference with/without the ceiling diffusor sonically? Have you tested the Messiah from the BIS?
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