Cal, I dont think those "horns" you have on your ports are doing anything more then acting as flares. The cutoff of those is well above 100hz im sure.
To the orginal thread topic, here's my idea
the conventional horn is front loaded with a rear chamber which provides an airspring and prevents the backwave from interfering with the front. If this rear chamber is removed and the driver is reversed then it would be come a rear loaded horn correct?
Well for a bass reflex loaded horn the front of the driver fires directly into the horn while the rear goes through a bass reflex chamber whose vent fires into the horn. If the vent is tuned to right around the horn cutoff then this should have the maximum efficiency, or at least so it would seem.
To the orginal thread topic, here's my idea
the conventional horn is front loaded with a rear chamber which provides an airspring and prevents the backwave from interfering with the front. If this rear chamber is removed and the driver is reversed then it would be come a rear loaded horn correct?
Well for a bass reflex loaded horn the front of the driver fires directly into the horn while the rear goes through a bass reflex chamber whose vent fires into the horn. If the vent is tuned to right around the horn cutoff then this should have the maximum efficiency, or at least so it would seem.
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In the development of the Tuba 24 subwoofer, Bill Fitzmaurice found that a vent into the compression chamber from the rear chamber would be overwhelmed by the compression in the compression chamber. Therefore, such a setup would not work.
The front port on this 6th-order bandpass subwoofer might be an example of a horn-loaded port. There is a large flare on the front end of this vent only, and the function of that larger flare is to provide mechanical damping to the action of the port, so that it will not continue to resonate as long as a port without the flare would. The flare is not large enough to provide any low-frequency loading, and just changes the way the air moves in the port. It seems to work well, having heard two of these subwoofers at a local venue: http://www.mackie.com/home/showimage.html?u=/products/swa1501/images/SWA1501front_BIG.jpg
The front port on this 6th-order bandpass subwoofer might be an example of a horn-loaded port. There is a large flare on the front end of this vent only, and the function of that larger flare is to provide mechanical damping to the action of the port, so that it will not continue to resonate as long as a port without the flare would. The flare is not large enough to provide any low-frequency loading, and just changes the way the air moves in the port. It seems to work well, having heard two of these subwoofers at a local venue: http://www.mackie.com/home/showimage.html?u=/products/swa1501/images/SWA1501front_BIG.jpg
BAM, where did you read Bill's findings? I would imagine myself that how overwhelmed the port would be would dependant on many, many things (vent size, tuning frequency, horn cutoff, the compression ratio, etc). Anyhow simply saying that the port was overwhelmed by the compression doesnt really say anything at all. What effect did porting into the compression chamber have on frequency response?
If the horn part of the "horn loaded vent" doesnt have a cutoff below the tuning of the vent it isnt horn loaded and it is merely flared. Mackie's sub merely has a flared vent, and it isnt horn loaded by any means.
If the horn part of the "horn loaded vent" doesnt have a cutoff below the tuning of the vent it isnt horn loaded and it is merely flared. Mackie's sub merely has a flared vent, and it isnt horn loaded by any means.
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