3" driver for CBT array? |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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The next step is to measure the impedance curve to determine if there is a sudden rise in resistance. A rise in resistance at 5 kHz would have the Beyma offer a dip within the 5 kHz range. Based on my earliest measurements the Faital Pro looks about right using a typical swift sine wave sweep. After being whacked with a good amount of power, the response curve is more like this... Best Regards,
Edited by Elliot Thompson - 29 February 2020 at 2:59pm |
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Elliot Thompson
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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That's right! The Qts, fs and VAS work together for the final result. Try matching both drivers at the same dB level at, I would say, 100 Hz and, make a measurement. The driver that remains the flattest from 100 Hz downwards will require less xmax within the flattest frequency range. The drivers will go out of phase at it's fs. So High Passing either driver above the fs should yield an in phase response up to 20 kHz. Best Regards,
Edited by Elliot Thompson - 29 February 2020 at 3:26pm |
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Elliot Thompson
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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made some progress used 11.5mm ply as it's what I had lying about. it's not quite bendy enough so going to leave it bending for a couple of days then screw it to a base and some curved side piece to stiffen it up. the more you curve it the lower the pattern control is maintained. got some more crimp spade connectors on their way to keep all the wiring neat
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3863 |
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Nice!
The traditional way to get wood to bend is to use steam or hot water - maybe you could use some wet towels to apply the heat and steam, and then screw it to a former whilst still warm? Or, use a kerf cut between each driver - as long as your front laminate runs top to bottom grain wise? 9mm deep with a 2mm blade should give you more movement without compromising strength too much. You would still want plenty of reinforcement and glue in the kerfs. But this way should help to keep each driver's "land" flat. |
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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think I can get it to 40deg arc of a 2m circle - should give pattern control down to 120Hz. I'd be afraid to steam this cheap ply in case it delaminated. Fine line between bendy and falling apart. might try some kerfs - might try doing them freehand with a narrow router bit. there's a reasonably thick gasket and there seems to be some flex in the mounting ears so think the drivers will fit okay. |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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That is a perfect project to do during these chaotic times. Have you tried implementing the outcome with EASE Focus? Best Regards,
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Elliot Thompson
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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got it wired up a couple of weeks ago and have been testing it side by side with my regular hi-fi speakers. still open baffle and haven't even put sides on it at yet as still palying around with the curvature. needs a bit of eq but has useful response down to 100Hz. sound is great with no midrange mudiness. plenty loud enough for home use but runs out of excursion on bass-heavy material. might experiment with another driver with lower Fs and more xmax Beyma 4FR40-8 Faital 4FE35-16 Dayton ND91-8
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ceharden
The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11776 |
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You might expect the bass response to improve a bit and excursion to reduce when you turn it into a sealed box. Might get you low enough to cross over comfortably to a sub.
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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I am tempted to try making it sealed back. but I'm quite liking the midrange sound of the open baffle. U-frame might give it a bit more authority down low.
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imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
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Did you ever complete this project?
I'm still sitting on 12 x 4" drivers, with an option on 4 more , and I'm interested in the options
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Keep pushing on, things are gonna get better.
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