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Old 20th November 2012, 04:28 PM   #11
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Hi OllBoll. Interesting points that I was wondering about. The tweeter will transition from omni to direction at some point, I'm guessing around 4khz. How much will this matter?

Multiple tweeter? Hmm. Wont I get nulls where they interfere?

I already own the SB29RDCN and a few other domes, small 2 and 3" full rangers, compression drivers, etc. Just need to know how to make it happen. The wavelengths above 2khz get so small I'm having a hard time knowing what to do, theoritically.
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Old 20th November 2012, 04:36 PM   #12
tinitus is online now tinitus  Europe
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I would suggest something like this
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Old 20th November 2012, 04:43 PM   #13
bwaslo is offline bwaslo  United States
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If you do a full horizontal omni, plan on positioning it well away from any walls. I did some a few years back, bad coloration if very near a wall, but pretty neutral if out in the open. Sweet spot wasn't as wide as I had hoped, but speakers disappeared nicely.
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Old 20th November 2012, 04:45 PM   #14
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by tuxedocivic View Post
Hi OllBoll. Interesting points that I was wondering about. The tweeter will transition from omni to direction at some point, I'm guessing around 4khz. How much will this matter?

Multiple tweeter? Hmm. Wont I get nulls where they interfere?

I already own the SB29RDCN and a few other domes, small 2 and 3" full rangers, compression drivers, etc. Just need to know how to make it happen. The wavelengths above 2khz get so small I'm having a hard time knowing what to do, theoritically.
While I haven't tried to build a half-omni half-forward firing like the pluto but rather only vanilla speker and full omni even Linkwitz himself thought that multiple tweeters were an improvement in the Orion since he permanently added the backwards firing one.

But like I said, I'm not sure exactly of how much difference it does. Obviously the Pluto is already different from a normal speaker if one trusts the impressions people have of it so it might be marginal.

Personally I just like the idea though that I can be anywhere in the room and the only difference I get is volume difference from left/right, but still get perfect response.

And about nulls and such, well yeah but so do you in real life. Your amazing brain doesn't care though so while a measurement microphone can pick them up your ears can't. Think about a choir for example, that's a lot of peaks and nulls from the interferace of all the voices but still it sounds kinda nice if you have a twice as big choir =)
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Old 20th November 2012, 05:01 PM   #15
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I would suggest something like this
How do you get rear radiation from that?
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Old 20th November 2012, 05:22 PM   #16
tinitus is online now tinitus  Europe
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lowest bass is naturally 'non directive, and as such as good as omni
below 100hz or something
but what excact xo point will work ok, Im not sure precisely

further up its 'half omni', with controlled 180 degr dispersion
and then some more added, thats the omni artificial 'room effect'
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Old 21st November 2012, 08:52 AM   #17
graaf is offline graaf  Poland
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Quote:
Originally Posted by tuxedocivic View Post
Thinking along the lines of Pluto, only adding the woofer downfiring.
but isn't this Pluto thing just boring?
why not trying sth really new? not thinking along any lines

I would follow tinitus' suggestions

for my part I say make it as short as possible, use coincident driver, bass or subbass in a separate enclosure, if crossed not too low You would not even need an enclosure for the main driver, simple baffle would suffice or even a bare driver - ask tinitus if do not believe me

do not angle anything forward but be prepared do equalize passively or actively for the treble loss (the most of treble energy would come through ceiling reflection)

You still can angle it forward with the use of spikes or else, if necessary

good luck!
best!
graaf

Last edited by graaf; 21st November 2012 at 08:56 AM.
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Old 21st November 2012, 11:07 AM   #18
6.283 is offline 6.283  Germany
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Originally Posted by tuxedocivic View Post
bandsei, is that 6.283 audio your site? The Demokrit-T catches my eye. That's somewhat along the lines of what I was thinking about. But 4 way (an extra 2 radiators handling below 300hz or so). Thanks for the link.
That would be me.

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Active XO around 300hz
Cross around the Schroeder Frequency of your room (180Hz...250Hz ?) and let the sub handle only the modal region. Then above use an acoustically small speaker with as little diffraction as possible. The SB29RDCN is probably to big for this application.
The xover to the tweeter is best placed at the border of the ITD (1800 Hz) listening range or above.
Full omni is kinda of cool but a small and controlled directivity above the ITD range makes a better stereo image.


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be careful with tubes
wide and short would be best
Or longer than about half the wavelength radiated by the driver with some stuffing.

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I would suggest something like this
This is not acousdtically small, which I and many others have found to be very important.
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Old 21st November 2012, 11:20 AM   #19
tinitus is online now tinitus  Europe
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This is not acoustically small, which I and many others have found to be very important.
sure it is
being low is acoustically small
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Old 21st November 2012, 03:13 PM   #20
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Originally Posted by graaf View Post
but isn't this Pluto thing just boring?
why not trying sth really new? not thinking along any lines
Except I'm not really looking to be innovative here, rather use some fundamental rules of thumb and proven ideas, combine that with my resources (drivers and materials), to see what omni is all about.

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The xover to the tweeter is best placed at the border of the ITD (1800 Hz) listening range or above.
How about a 2" upfiring (instead of the 4" I mentioned) with a forward facing dome in a waveguide crossed around 1800hz or even lower? I also have a pair of Dayton ND28 which are extremely compact when you remove the faceplate. Probably 32mm diameter. Could either of these arrangements work better?
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