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post #31 of 34 Old 03-22-2013, 02:00 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

If you happen to have an anechoic chamber handy you can measure your speakers in it. If not you can use a back yard that allows you to take a measurement at least 30 feet from any buildings or walls. That's also anechoic. Chambers are used where going outdoors is impractical. Danley Sound Labs does their measuring in their parking lot.
What don't you understand?

It's not an-echoic because of reflections from the ground.

Notice the floors in these shots from B&W: http://blog.bowers-wilkins.com/sound-lab/tools-of-the-trade-the-anechoic-chamber.

I'm surprised you don't know something this basic Bill.

Mind you: Real rooms always seem to have floors: so it's not a bad measurement, but it's not the same as an an-echoic chamber
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post #32 of 34 Old 03-22-2013, 03:16 PM
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When one measures outdoors if it's a sub one measures ground plane, which gives a half-space result. If it's a full range speaker one measures ground plane to get the half-space result up to the baffle step frequency. Then one puts the cab on its back, aimed upward, with the mic suspended above the speaker. This will give a half-space result above the baffle step. The two results are then spliced at the baffle step frequency for a complete half-space anechoic result. Alternately one can dig a pit into which the speaker is placed, facing up, with the area between the speaker and the surrounding ground covered to create a flush mounting of the speaker with the ground, so that a single measurement may be taken. Some speaker companies use this method, but it's a lot more work than a consumer would want to go through.

This explanation is for the benefit of those actually interested in learning something, not those who's only interest lies in incessantly arguing about that which they only vaguely comprehend.

You know...trolls. rolleyes.gif

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
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post #33 of 34 Old 03-22-2013, 04:32 PM
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Actually I put up then edited away a suggestion of burying the speaker face up in the ground as I know McIntosh used to do for two reasons.

1) It's not done in your parking lot example.
2) It's not salient; so bringing up a tangent rather then staying on topic would be done by... I'd guess a troll.

Burying in the ground is going to decrease the apparent volume of the tweeter as it loses the reflection of the ground (this is as opposed to a real room).
It will also raise the volume of the woofer as opposed to an anechoic chamber (you remember: we were talking about those before you attempted to redirect my perfectly accurate point (complete with pictures) by implying I was a troll).

Anechoics don't measure the half-space result. Buried in the ground does. In a room is like neither. They are three different measurements.

The objects which will reflect (the ground in outdoors testing and "nothing" in an anechoic chamber) are different; so no amount of opinion that they are the same will change the basic physics you are so blithely ignoring.

I guess some people are more interested in appearing right than learning and becoming right. rolleyes.gif
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post #34 of 34 Old 06-25-2013, 03:45 PM
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i can recommend the klipsch rf 7, try to find them used, but still, although they are rated with hi sensitivty, they need POWER! to make them sing, i recommend at least 250 rms per channel, 350 max.
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