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In Reply to: RE: How flat can cornerhorns be? posted by mdg on July 06, 2015 at 09:08:57
Hi
In a normal room there is a room gain slope which can be from +12dB per octave in a sealed concrete bunker to more like +3 to +9 dB per octave in a normal house.
This (with a flat a flat response speaker in half space or outdoors) produces a rising response once one is below the lowest room mode which is often associated with the 1/2 wavelength frequency of the largest room dimension.
In an automobile where this effect is easier to see, one can take a sealed box which rolls off around 50Hz at -12dB/oct and when you place it in the car, you can (with windows rolled up) get flat response down an octave or a lot more below the normal corner due to the room gain or cabin gain slope as they often call it in the auto world.
In a sealed car, the +12dB cabin gain slope cancels out the -12dB slope from the speakers roll LF off, perhaps the closest thing to a free lunch in audio
Hope that helps
Tom Danley
Danley Sound Labs
So, since a sealed back horn (including a lab sub) eventually has a -12dB /oct roll off, one might figure out approximately where your lowest room mode would be and then shoot for a horn that has a response knee around that same point.
Follow Ups:
Hi thnx all for the reply.
I also read, from archived post, that the corner has also
a hornloading effect an the radiator.
Would it be possible to extract the adding resistive and reactance load of a measurements and intergrate this in my model, for the last final flare?
I had a tought about measuring a simple sealed radiator outside (free from reflection) and then measuring it in the room, placing the radiator where the mouth off the horn would normally be.
The difference in resistive and reactance load would be presenting the extra hornloading of the corner. I dont know it this would be represantative.
I want to come as close as possible to the 20hz corner.
gr. Marcel
My listening room has a concrete floor and long wall. The room is also thickly paneled on all 4 walls. The volume setting on my subwoofer tells me that their is a lot off room gain. Very satisfying base is achieved at a very low volume setting in relation to the satellites.
Dave
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