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Multi-Way Conventional loudspeakers with crossovers

Directivity without Waveguides or DSP
Directivity without Waveguides or DSP
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Old 18th June 2017, 10:00 PM   #91
Patrick Bateman is offline Patrick Bateman  United States
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I agree, just trying to get 'in the ballpark' before I build something
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Old 18th June 2017, 10:03 PM   #92
Patrick Bateman is offline Patrick Bateman  United States
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Click the image to open in full size.

Here's what the wavefronts look like if you use a spherical enclosure instead of an enclosure with flat sides (a la Dutch & Dutch) or the football shaped enclosure I posted in post #86

Spherical seems to work a teensy bit better, but it's probably more trouble than it's worth, the difference is subtle

Here's why I think this is:

Spherical enclosures work really well for tweeters. This is because the wavelengths become long enough that they start to 'wrap around' the baffle. For instance, 2000hz is 17cm long; when your tweeter baffle is just 8cm wide, the wavefront is going to wrap around and that's where a sphere comes in handy

In these passive cardioids, the output from the side ports is interfering with the output from the front of the enclosure. So the waves from the front don't get a chance to wrap around.
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Old 18th June 2017, 10:17 PM   #93
Patrick Bateman is offline Patrick Bateman  United States
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Click the image to open in full size.
In the LX mini, the tweeter faces straight forward. Based on the sims here, this seems to produce a strong floor bounce because the beamwidth is about 90 degrees. To eliminate the floor bounce, you'd want to angle it up about 15-45 degrees.

Click the image to open in full size.
This is exactly what Gradient does in their Helsinki speaker

Click the image to open in full size.
I ran some sims to see what would happen if the ENCLOSURE faced forward, but the driver is angled up. This seems to work; it tilts the beam upwards. On the left is an enclosure with an angled baffle, on the right is one with a flat baffle.
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Old 18th June 2017, 10:35 PM   #94
Patrick Bateman is offline Patrick Bateman  United States
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Passive cardioids are inherently inefficient. We're basically throwing away efficiency due to destructive interference, a variation on how a dipole works.

I did some sims that use a waveguide to raise the efficiency, but they didn't work. Basically the cardioid pattern starts to fall apart if the radiation to the front and the rear isn't symmetric. We basically want the output to be symmetrical to the front and to the rear, and we want a delay between the two. As @Windforce85 noted, DSP delay with an array of monopoles is the ideal way to do this.

I want to keep this passive, so another way to raise the efficiency is to use an array. This seems to work; here's a sim that shows two drivers instead of one. The pattern is maintained. An array also gives you the opportunity to steer the beam up or down, to avoid floor bounce.

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Old 18th June 2017, 11:46 PM   #95
mwmkravchenko is offline mwmkravchenko  Canada
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Directivity without Waveguides or DSP
Getting more interesting as I read your comments and simulations.

Might turn something like this into a commercial product.
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Old 19th June 2017, 12:02 AM   #96
Patrick Bateman is offline Patrick Bateman  United States
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Click the image to open in full size.

Click the image to open in full size.

I tried to make an enclosure in 3D but it got too big. So I ran some sims and it looks like you can fold the enclosure, similar to a transmission line. It doesn't perform quite as well, but it's smaller.

I think this is the route I'll go, because I don't have space for an unfolded line.
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Old 19th June 2017, 07:33 AM   #97
David McBean is offline David McBean  Australia
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Quote:
Originally Posted by Patrick Bateman View Post
So I ran some sims and it looks like you can fold the enclosure, similar to a transmission line. It doesn't perform quite as well, but it's smaller.
It never ceases to amaze me, the creative analyses you do using the Hornresp Wavefront Simulator tool :-).
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Old 19th June 2017, 08:34 AM   #98
Windforce85 is offline Windforce85  Poland
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Oh Hi David nice to see you here. That tool is amazing thing it indeed can dissipate spare time so effectively I already know it well! It would be hovever nice to see some improvements if you don't mind it... Thanks for this piece of nice software for DIYers!
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Old 19th June 2017, 05:48 PM   #99
weltersys is offline weltersys  United States
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Originally Posted by mwmkravchenko View Post
Getting more interesting as I read your comments and simulations.

Might turn something like this into a commercial product.
David Gunness of Fulcrum Acoustics has quite a few very impressive single amplifier passive cardioid commercial products available now. Was rather amazed at just how many products he has come up with recently.

Got to hear several of them at InfoComm in Orlando last week, of everything offered by hundreds of vendors, they were most impressive to me.
The rear rejection was quite amazing for the size, bringing pattern control to low frequencies in cabinets that can be handled by one person and have good sensitivity.

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Old 19th June 2017, 06:13 PM   #100
mwmkravchenko is offline mwmkravchenko  Canada
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Quote:
Got to hear several of them at InfoComm in Orlando last week, of everything offered by hundreds of vendors, they were most impressive to me.
The rear rejection was quite amazing for the size, bringing pattern control to low frequencies in cabinets that can be handled by one person and have good sensitivity.
Art looks like you and I might be in for a chin wag!
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