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Old 21st January 2012, 11:17 AM   #11
OllBoll is online now OllBoll  Sweden
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Quote:
Originally Posted by AllenB View Post
Sreten, the first option has the drivers out of phase (as well as physically reversed).

Peter, good point about the efficiency but they are connected isobarically. What would you think about using some pvc between them but retaining the box as a baffle?

OllBoll, there are numerous reasons I might be reluctant to cross too high. Anyway, your box is interesting because you could round the sides to reduce diffraction, eg: cut some pvc pipe in half which will fit front to back corners of each side of the box.
The square box in the drawing is of course symbolic, in practice I had planned to do a more rounded box of course

Though a pipe around the drivers might be even better for them internally.

Though the more I think about this the more I lean on not overcomplicating the project and instead using a single M15CH002 as the midrange, I won't have to handle the 6nd430 breakup either which simplifies my crossover

But about spacing, if the box sit ontop if a single OB woofer and then have the correct dime delay then wouldn't the spacing issue become a non-issue? Isn't the box approximable as a larger flat baffle with a single driver but with a time delay on said driver?

Would be fun to try but as I said a single M15CH002 might be the easiest. Wouldn't be that much cheaper though since I live in europe so can get 6nd430 fairly cheap, two is only 56 dollars more than a single M15CH002.

Last edited by OllBoll; 21st January 2012 at 11:19 AM.
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Old 21st January 2012, 11:35 AM   #12
AllenB is offline AllenB  Australia
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The driver spacing, but also radiation through the basket have their limits. All part of the compromises you have to make before you build. I do think the larger rounding sounds promising. If I were going to go that way, I'd stuff the box and forget about trying to couple the drivers. I'd take the efficiency loss. Just my opinion.
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Old 21st January 2012, 06:52 PM   #13
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Originally Posted by OllBoll View Post
since I live in europe so can get 6nd430 fairly cheap, two is only 56 dollars more than a single M15CH002.
But in fact one is enough for OB, have a look at my 'Blindstone': Ultimate OB Gallery .

I cross active with DCX2496 at 277 Hz (from AE IB15) and at 2.07 kHz (to Neo3W) for the 6ND430.

/Erling
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Old 22nd January 2012, 03:30 AM   #14
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There's really no sonic advantage to the in box dipole as there's still enclosure artifacts working on the response and internal reflections passing back through the cones. Also as mentioned earlier, you're not going to get full dipole cancellation as the front and rear drivers cancellations will be limited to a narrower pass band. Get rid of the box idea. The 6nd40 shouldn't require too much coaxing to get to 200hz on an open baffle.

I know some guys experimented with the no baffle suspended driver arrangement. I can't imagine a non biased listener wouldn't be opposed to all of the diffraction at the edge of the driver frames.....ouch!
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Old 22nd January 2012, 06:02 AM   #15
OllBoll is online now OllBoll  Sweden
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Originally Posted by mayhem13 View Post
There's really no sonic advantage to the in box dipole as there's still enclosure artifacts working on the response and internal reflections passing back through the cones. Also as mentioned earlier, you're not going to get full dipole cancellation as the front and rear drivers cancellations will be limited to a narrower pass band. Get rid of the box idea. The 6nd40 shouldn't require too much coaxing to get to 200hz on an open baffle.

I know some guys experimented with the no baffle suspended driver arrangement. I can't imagine a non biased listener wouldn't be opposed to all of the diffraction at the edge of the driver frames.....ouch!
The purpose of the box wouldn't be to cross lower, but rather to avoid the not as nice rear dispersion of the driver since the magnet is so large. And in doing so it would also make front and rear dispersion perfectly symmetrical.

What I wondered was mostly about those internal reflections, are they merely theoretical or would they in practice cause measurable and hearable distortion?
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Old 22nd January 2012, 10:53 AM   #16
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And in doing so it would also make front and rear dispersion perfectly symmetrical.
That is an odd idea don't you think? Unless you are able to audition your speakers front and rear simultaneously
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Old 22nd January 2012, 01:11 PM   #17
Rudolf is offline Rudolf  Germany
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Originally Posted by mayhem13 View Post
I know some guys experimented with the no baffle suspended driver arrangement. I can't imagine a non biased listener wouldn't be opposed to all of the diffraction at the edge of the driver frames.....ouch!
There is a relationship between frequency, bafflewidth and diffraction. Each driver in such an arrangement is Xovered, before diffraction becomes an issue.

Quote:
Originally Posted by OllBoll View Post
What I wondered was mostly about those internal reflections, are they merely theoretical or would they in practice cause measurable and hearable distortion?
In your dipole box there is no massive pressure change like in a closed box, not even a notable pressure at all. This makes a world of a difference - for the better.

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Old 22nd January 2012, 02:03 PM   #18
OllBoll is online now OllBoll  Sweden
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Originally Posted by pieter t View Post
That is an odd idea don't you think? Unless you are able to audition your speakers front and rear simultaneously
But isn't that exactly what you do with all the reflections from the room? I also want to build the speakers to be as omnidirectional as possible. I don't want to have a sweet spot for listening or even a direction but instead I just want to spread music in the room so I can enjoy it wherever I am.

My current speakers are omnis which is my reference, the natural sound of reflections is not to be underestimated

Symmetrical front and rear response would simplify crossover also. Then I only have to fiddle with response on one side, I can also ignore that off-axis response of the drivers drop earlier on the rear than the front and can therefore cross higher.
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Old 22nd January 2012, 02:21 PM   #19
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Originally Posted by OllBoll View Post
But isn't that exactly what you do with all the reflections from the room? I also want to build the speakers to be as omnidirectional as possible. I don't want to have a sweet spot for listening or even a direction but instead I just want to spread music in the room so I can enjoy it wherever I am.
You always fiddle with reflections in a listening room no matter wether the speakers are monopole, dipole, bipole or truly omnidirectional.
When you prefer omnidirectional sound maybe bipole is better for you, but I think dipole speakers have better focus.
Dipole radiation patterns become more cardioid with rising frequency, and the combination of direct and reflected sound with dipoles (assuming proper location) results in a very fine diffuse sound field, which, to my ears at least, gives an illusion approaching sound of a live concert.

Last edited by pieter t; 22nd January 2012 at 02:25 PM.
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Old 22nd January 2012, 02:49 PM   #20
OllBoll is online now OllBoll  Sweden
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Originally Posted by pieter t View Post
You always fiddle with reflections in a listening room no matter wether the speakers are monopole, dipole, bipole or truly omnidirectional.
When you prefer omnidirectional sound maybe bipole is better for you, but I think dipole speakers have better focus.
Dipole radiation patterns become more cardioid with rising frequency, and the combination of direct and reflected sound with dipoles (assuming proper location) results in a very fine diffuse sound field, which, to my ears at least, gives an illusion approaching sound of a live concert.
The speakers only become cardioid with rising frequency if you build them that way, I wish to build a pair with the same off-axis response and dipole pattern and on all frequencies

Shame though that smaller tweeters aren't made that have perfect off-axis response all the way up to 15-20 khz To compensate the current plan is to have a ring of four cone tweeters on each side of the baffle, kinda like my current speaker but doubled to become dipole.
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