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Full range cardioid
Full range cardioid
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Old 26th April 2015, 12:42 PM   #41
Jag768 is offline Jag768  Netherlands
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Thank you and yes, funny that you mention them. They happen to be friends of mine and they brought me the idea of building a cardioid speaker

Applied the first layer of primer and one layer of woodstain.
Attached Images
File Type: jpg Center_sub_casco.jpg (140.4 KB, 1085 views)
File Type: jpg Center_sub_primer.jpg (122.1 KB, 1065 views)
File Type: jpg Fronts_beits.jpg (129.9 KB, 1056 views)
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Old 20th May 2015, 05:46 PM   #42
Jag768 is offline Jag768  Netherlands
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First measurements are in on cardioid behaviour of top cabinets. First tried without filling of the u frame behind the woofer, resulting in dipole radiation below the 1/4 wave resonance of the u frame en tending towards omnidirectional at the 1/4 wave resonance. Than added one layer of rockwool at a time. Optimal result was 4 layers of high density Rockwool of 50mm thick (so 20cm in total). Still some influence of the 1/4 wave resonance is visible but now polar is tending towards cardioid with 10dB+ LF cancellation at 180degrees. Results are quite similar to the prototype cabinets, now only with minor differences between the left and right (top) cabinet, which were probably related to leaky prototype enclosure. Im still going to try to add one more layer of rockwool to see if it further reduces the influence of the 1/4 and 1/2 wave resonance of the uframe.
Attached Images
File Type: jpg Tops.jpg (196.7 KB, 1033 views)
File Type: jpg Tops2.jpg (261.2 KB, 1020 views)
File Type: jpg Top3.jpg (367.8 KB, 366 views)
File Type: png No_damping.png (132.5 KB, 329 views)
File Type: png Rockwool_20cm.png (55.0 KB, 223 views)
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Old 23rd May 2015, 01:45 PM   #43
LineArray is offline LineArray  Germany
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Hello Jag768,

just a practical question,

when using the Hypex PSC 2.400 in the mono subwoofer and listening to stereo,

where do you get the stereo summing signal from, to feed into your subwoofer ?

Kind Regards
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Last edited by LineArray; 23rd May 2015 at 01:53 PM.
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Old 29th May 2015, 10:35 PM   #44
Nissep is offline Nissep  Sweden
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Here is a crazy idea.

Why not build a electronic bass trap for total cancelation of bass behind the speaker?
A monopole with a mic close to the cone as input. With the right polarity the cone should try to cancel all sound that reach the mic.
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Old 30th May 2015, 11:47 AM   #45
speaker dave is offline speaker dave  United States
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Quote:
Originally Posted by Nissep View Post
Here is a crazy idea.

Why not build a electronic bass trap for total cancelation of bass behind the speaker?
A monopole with a mic close to the cone as input. With the right polarity the cone should try to cancel all sound that reach the mic.
Not crazy and certainly doable, although a mic isn't needed. 2 elements with the right delay will create a cardioid. Jag is simply creating the same thing with acoustical delay through his cabinet.

Jag, very good results so far. Is the pattern maintained below 100Hz?

David
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Old 1st July 2015, 09:03 PM   #46
Jag768 is offline Jag768  Netherlands
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Quote:
Originally Posted by LineArray View Post
Hello Jag768,

just a practical question,

when using the Hypex PSC 2.400 in the mono subwoofer and listening to stereo,

where do you get the stereo summing signal from, to feed into your subwoofer ?

Kind Regards
actually i use two psc 2.400s for 4 subs in total. So i run them stereo. Of course you could also sum the signal and feed them to both psc 2.400s, but probably it wont matter much in practice since bass is mostly monaureal anyway

Quote:
Jag, very good results so far. Is the pattern maintained below 100Hz?

David
The garden i have used for measurements allow for a ~10ms gate, so i dont have reliable data for <100Hz. However, looking at the polar data is appears that the cardioid behaviour is lost <100Hz. The range <100Hz is covered by four subs placed throughout the room.

Some more pics are attached showing the final build, measurement setup, the filter simulation and on axis response. And horizontal directivity data shown in overlay in 10 degree steps, sonogram and polar.
Attached Images
File Type: jpg Woofers.jpg (120.2 KB, 285 views)
File Type: jpg Woofers2.jpg (111.6 KB, 237 views)
File Type: jpg Final.jpg (102.3 KB, 294 views)
File Type: jpg Meten4.jpg (236.1 KB, 337 views)
File Type: png Directivity_sonogram.png (90.7 KB, 328 views)
File Type: png Directivity_overlays.png (48.0 KB, 220 views)
File Type: png Filter simulatie.png (20.9 KB, 192 views)
File Type: png Filter ontwerp on axis response.png (9.6 KB, 164 views)
File Type: png Final polar - DI pattern low.png (45.1 KB, 136 views)
File Type: png Final polar - DI pattern mid.png (42.8 KB, 132 views)
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Old 2nd July 2015, 05:34 AM   #47
Barleywater is offline Barleywater  United States
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Yes; a very impressive project.

Getting good amplitude matching is a key. Getting phase response of monopole and dipole elements and center to center distance to behave above dipole's natural peak is very difficult.

I've made a cardioid reference of limited SPL do to driver size; but demonstrate integration required to get 100Hz to about 1kHz:

Click the image to open in full size.

Above are indoor measured at about 2 feet. Display is 110ms left and right windows with speaker about 5ft from walls and tweeter at listening height.

Your hand off to horn is excellent!
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Old 2nd July 2015, 09:58 AM   #48
Juhazi is offline Juhazi  Finland
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Quote:
Originally Posted by Jag768 View Post
Some more pics are attached showing the final build, measurement setup, the filter simulation and on axis response. And horizontal directivity data shown in overlay in 10 degree steps, sonogram and polar.
Congrats, tour de force! Very similar to Kimmo's KS-1807, even the Hypex plate amp!
Click the image to open in full size.
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Old 2nd July 2015, 01:59 PM   #49
gainphile is offline gainphile  Australia
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Most impressive especially what you achieve in the midrange!

Any further details about the construction (e.g. why you do not use side vents)? These seems much better.
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Old 11th July 2015, 10:21 PM   #50
Jag768 is offline Jag768  Netherlands
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Quote:
Originally Posted by Juhazi View Post
Congrats, tour de force! Very similar to Kimmo's KS-1807, even the Hypex plate amp!
Click the image to open in full size.
Thank you. Looking quite similar indeed.

Quote:
Originally Posted by gainphile View Post
Most impressive especially what you achieve in the midrange!

Any further details about the construction (e.g. why you do not use side vents)? These seems much better.
Yes, side vents is something i would still like to try some day. I actually started with side vents, only situated more to the back. Couldnt get it to work. Bu my initial test enclosure was too difficult. In a later stage i added extra openings right after the baffle or halfway the u frame, neither worked very well. I might try to build a new test enclosure some day for testing side vents, a lot of people seem to have achieved good results with those!
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