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Old 22nd May 2014, 08:19 AM   #1
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Default Omnidirectional Alpair?

Hi all!

I've just got a quick question regarding box design for the A10P or A12P.

I've currently got a pair of Duevel Planets (Planets Entry Speaker) which are two way omnidirectional speakers with a downward-firing bass port and spherical diffusers on top. They aren't the last word in quality I'm sure, but they are fun, look great and have a large sweet spot.

I'm currently putting together a couple of low watt tube amp kits and thought it would be fun to also make a higher efficiency, single driver version of the Planets.

I have no experience in speaker building, so I was wondering whether I should just take the Pencil design, readjust the dimensions to make a square (rather than rectangular) prism shape (but keeping the same internal diameter), move the driver cut-out to the top and move the vent to the bottom, and then add feet and a DIY diffuser at the top?

I also expect that with the radial diffusion, it's likely the treble would be attenuated, so the A10P would likely be a better candidate than the A12P, despite the lower sensitivity.

Or should I commission a custom design from a notable member of this board, with the caveat that I understand that I would have to experiment with the diffuser part on my own.

Thanks for your time in reading this and your thoughts!

Taz.
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Old 22nd May 2014, 08:28 AM   #2
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Originally Posted by Mistertaz View Post
move the driver cut-out to the top.
Taz,

Movin the driver from its specified Zd (offset) will degrade performance, and it won't be a Pensil any longer.

dave
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Old 22nd May 2014, 09:57 AM   #3
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Taz,

Movin the driver from its specified Zd (offset) will degrade performance, and it won't be a Pensil any longer.

dave
Ahhh... Thanks for that info Dave. I think I'll contact someone for more advice.

Thanks!
Taz.
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Old 22nd May 2014, 03:16 PM   #4
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I'm not sure why people are so interested in wide dispersion drivers. I sit in one position, one chair, for listening. I don't get up and move around the room except to change a record (no music on anyway). I use a Herron VTSP-3A preamp which has a remote, so I don't need to move to change source or volume. My seating position and speaker position are optimized for best performance. I rarely have others over to listen.

So there is one listening position, I don't care if the speakers roll off significantly 15 degrees off axis as long as they sound good at the seating position, the sweet spot.

There is some benefit to not using wide dispersion speakers in that there is less side wall interaction in the upper mids and highs with narrow dispersion speakers. I learned this a long time ago with Acoustat Model 4 speakers. Very directional and low dispersion. One sweet spot. Low side wall interaction.
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Old 22nd May 2014, 05:20 PM   #5
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Possibly because other people may be present and wish to enjoy the music also.
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Old 22nd May 2014, 05:39 PM   #6
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Maybe. It seems that the overwhelming requirements for speakers are pinpoint imaging and pounding sort of bass at ~80Hz. Those who require the latter, at least in the sense of a single driver speaker need not be on this particular forum. It also seems that a large percentage of posters are confined to 10'x10' bedrooms or odd corners of a great room that is hugely asymmetric. The great destroyer of imaging is early reflections. forcing the speakers close to the sidewalls destroys imaging. An omnidirectional speaker will splash off of the sidewalls and also the front wall. Worst case for imaging. Dipoles will not, at least in theory, illuminate the side wall, but will reflect off of the front wall.

IMO the best positioning on the speakers is on the long wall where the side walls are no longer early reflections, or at least substantially reduced in power level, or at 45* across a corner were the side wall reflections will be primarily aimed behind the listener.

You want a large sweet spot? Toe the speakers out 10-15* and well away from the side walls.

Bob
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Old 22nd May 2014, 09:27 PM   #7
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Possibly because other people may be present and wish to enjoy the music also.
And that is the point I make. Well more than 99% of the time, I listen alone. And even with the Acoustats and Martin-Logans, very popular speakers, there is one sweet spot. Even with some wide dispersion speakers, there is one sweet spot because being off to one side or the other changes the balance, image and soundstage.

I suggest that when reproducing a well-recorded symphonic work, there is one sweet spot where everything locks in regardless of how wide a speaker's dispersion.
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Old 22nd May 2014, 10:57 PM   #8
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Understood, but it's also largely dependent on what the 'sweet spot' is, since impressions will inevitably vary with individual perception & taste. I would however suggest that since not everybody listens to music alone, driver manufacturers need to factor a reasonable power response / dispersion into the equation. Otherwise, if we took it the other way to the logical extreme, we'd all be either using headphones, or focussed arrays, which are more or less the ultimate in that sense, but weld you into a single location.
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Last edited by Scottmoose; 22nd May 2014 at 10:59 PM.
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Old 23rd May 2014, 06:09 PM   #9
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Focused arrays certainly do that, but I've always found headphones / earbuds do exactly the opposite - i.e. the acoustic soundstage follows whatever position your head is oriented - which is one of the things I find most unnatural about them.

Background chatter on Pink Floyd DSOTM is particularly disorienting in monaural - I already have enough voices in my head, thank you very much.
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Old 23rd May 2014, 06:31 PM   #10
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You hear voices Chris? You could make a fortune holding sťances.

Good point though re the perceived differences between the two. Obviously not one of my brighter moments last night...
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