I ve seen other ideas at diyaudio with mesh/stuffing/holes etc in enclosure to implement a cardioid. Can ONLY acoustic bass reflex work as effectively? The goal is constant narrow directivity down to 250Hz.
Lets take a 6" midrange, if we put a small rear enclosure and port it sufficiently high (at around 2Khz) with several holes around the edges then does it yield a cardioid? Tuning could be achieved by observing the impedance.
The bass reflex alignment should provide the low pass and the corresponding delay.
Lets take a 6" midrange, if we put a small rear enclosure and port it sufficiently high (at around 2Khz) with several holes around the edges then does it yield a cardioid? Tuning could be achieved by observing the impedance.
The bass reflex alignment should provide the low pass and the corresponding delay.
How are you going to "port it at 2kHz"? I suggest you try doing some trial calculations on the length and diameter of your theoretical ported box with a 2kHz resonance frequency and then post what you come up with...
I do not believe that is possible.
Very creative thinking, however.
I do not believe that is possible.
Very creative thinking, however.
What your describing sounds similar to the various "passive" cardioid box designs. normally they use an aperiodic enclosure, and apparently can work pretty well. My gut tells me that it would be very hard to get the design to work the actual ports (because the output from them is not wideband)
A second 6" driver on the back eq'd to have the same response as the front diver out the back of the box with flipped polarity and a suitable delay will give you a cardioid that will cover the <100-~400Hz range. It works very well but an extra amp and DSP channel is required.
^Yes, the problem with most double driver systems is the limited passband of cardioid pattern, typically only 2 octaves. Side-vented damped cardioids are't much better.
Op idea most likely can not be made to work except at some very narrow passband.
Some theory and studies with protos here
https://www.kirchner-elektronik.de/upload/15522394-DIPOL-CARDIOIDeng.pdf
Op idea most likely can not be made to work except at some very narrow passband.
Some theory and studies with protos here
https://www.kirchner-elektronik.de/upload/15522394-DIPOL-CARDIOIDeng.pdf
I think 'vented with a damped port' is just another way to describe a leaky enclosure. Leaky enclosures can have a cardioid pattern (if well tuned), so yes it can work.
To become cardioid, leakage area must be sufficient and evenly distributed on sides. Basically pretty much same principles as dipole, but some obstruction or phase rotation/delay is needed to block backside radiation 150-10 degrees.
"Keyser" (who's now at Dutch&Dutch) made some nice experiments and measurements some time ago, and so did "kimmosto" even earlier. Finnish loudspeaker companies Gradient and Amphion have used cardiod midranges for ages!
2-way: Waveguide + Cardioid-like
Cardioid bass
"Keyser" (who's now at Dutch&Dutch) made some nice experiments and measurements some time ago, and so did "kimmosto" even earlier. Finnish loudspeaker companies Gradient and Amphion have used cardiod midranges for ages!
2-way: Waveguide + Cardioid-like
Cardioid bass
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Ports of resistance enclosure could be filled vents. For example single column on both side walls. But it should stay as resistance box i.e. resonance which would attenuate cone signal should be totally prevented with port filling.
A small volume, wide and small port should get me there. Are you trying to say that ported box alignment breaks at such a high frequency?
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