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Cardioid construction with coax and woofers

D!sco

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to be in a more narrow construction rather than a more wide one?
I'm having a little trouble understanding what you're referring to here. Driver width? Like a 5" vs a 6"?
 
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Digital_Thor

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I'm having a little trouble understanding what you're referring to here. Driver width? Like a 5" vs a 6"?
Oh sorry... When I for example tried to build with the Seas DXT. The cabinet width meant a great deal for the dispersion and paring with a midrange. Now that I have gone to Coax. I can only find a lot of measurements for the KEF R11 and only 1 for the KEF R900( and only on-axis). Since the KEF R900 is much wider than the R11, then I simply wondered whether the R11 had some sonic benefit from being more slim.
 

D!sco

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Thanks for explaining. Have you tried the diffraction sim in VCAD? It's not just a matter of "better or worse", it's really down to use case. The tool will be way more useful than just trying to imagine each scenario.
 
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Digital_Thor

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Thanks for explaining. Have you tried the diffraction sim in VCAD? It's not just a matter of "better or worse", it's really down to use case. The tool will be way more useful than just trying to imagine each scenario.
I would love to :D But how do I use that software - steep learning curve?
 
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Digital_Thor

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Is there a VCAD file of one of the KEF speakers, that I can download to load in VCAD, so I can see how it's done, before experimenting on my own idea and drivers?
 

D!sco

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Erin has data you can input and SPL/impedance charts you can trace in VCAD. In VCAD's tools, there's the "Diffraction" tool. Input your baffle geometry and driver size, it will show you what the effect will be on the baffle. You can apply a driver's SPL trace to the diffraction in full space to get a modified SPL output, and you can get a fully simulated polar chart.

Yes, the learning curve is steep and there aren't many good tutorials. I've had to pull out a german to english translation more than once to get the information I need on this software. I would write an in-depth tutorial on how it works if I felt 100% confident. I can flesh out this part, though.

Screen Shot 2023-11-02 at 13.25.27.png

Screen Shot 2023-11-02 at 13.30.01.png

1: Pick your driver size or radiating area, the shape, and the number you want to simulate on-baffle. You can do arrays individually or in groups. I like to do both.
2: Pick your baffle size. You'll be able to adjust each corner as you see fit with coordinates on the view tab. Ideal edges are perfect roundovers, open baffles have more edge effects. No frame.
3: Upload your SPL trace or FRD file and be sure to check all the boxes, including full space and feed speaker.
4: Simulate the baffle.
5: Move the drivers around and adjust listening location appropriately. Corners can be adjusted, as well as the overall baffle size. Note that the parameters filled in 1 and 2 will not change to match what happens in the simulation screen.
6: To apply directivity, export to a new folder which will populate the folder with this baffle design revealing a full polar directivity simulation. This will also be applied to the currently selected driver in the "Drivers" tab of the main window. This is how I get beautiful polar simulations, like this:
Screen Shot 2023-11-02 at 13.53.30.png


The SPL trace is pretty easy to use, just drag and drop a picture, line up the minimums/maximums, pick a color to follow and erase any weird extras. Takes a few tries, but it's by no means an impossibility to figure out by yourself.
 

D!sco

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I’ll say one more thing; I like to keep the mic centered on the driver when simulating individual drivers on-baffle. Then I put in the xyz difference from center-to-center. The software will adjust cancellations and gain in the crossover tab and give you relatively accurate polars. Using all these tools are only for ballparking it, a finished product may exhibit unintended characteristics. It’s better to make all of these measurements yourself with the baffles or full enclosures and the driver you intend to use to get the best possible result.
 
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Digital_Thor

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Just tried to measure both the Seas C18 and then the KEF R midrange.... guess which is which... :cool:

Seas coax.jpg


KEF coax.jpg
 

SomeDude

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According to the file name the first is the Seas ;-)
 
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Digital_Thor

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According to the file name the first ist the Seas ;-)
Yeah... can't cheat you guys ;) Thought of it right after uploading, but thought I'd give it a chance. working on a better filter, to give it another go.... uploading soon :)
 
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Digital_Thor

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I adjusted some more, and in my second attempt, I reached something like this in the listening position....
KEF  coax + bas + sub - lytte.jpg


Room acoustics definitely play a role when suck-out's come in. But at 1 m with a boxy test cabinet and quick filter.... I get this at on-axis, 20 and 60 degrees :
KEF coax + SBNRX.jpg

Filter and EQ are as follows:
Disk EQ.jpg

Mid EQ.jpg

Sounds absolutely fine on top of 2 x SB23NRX and 4 subwoofers. Tried to avoid high Q PEQ's and make it as simple as possible. Next step is to improve the cabinet and add the cardioid, so see if anything changes....
All is done with a Roland Quad Capture, ASIO, calibrated mic from Cross-Spectrum and timing loop-back.
 
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