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open baffle dipole

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Tom Umney View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom Umney Quote  Post ReplyReply Direct Link To This Post Topic: open baffle dipole
    Posted: 28 June 2006 at 11:34am
I've heard of open baffle dipole for home entertainment and pa line arrays and wondered what the principle behind it was?
 
As the open baffle part seems that the drivers ain't in an enclosure anymore and are coupled to the air like a driver in free-air outside its cabinet.Which I would have thought would give a crappy sound. But Maybe theres something alse behind it hence the dipole bit.....
 
Can anyone care to explain to me what is a open baffle dipole? and why its used? and what sound it gives in terms of both good and bad points of view?
 
 
 
 
 
 
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Dave Slater View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave Slater Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2006 at 7:14am
in its simplist form it's a flat board with a driver mounted in its center
 
it only really works properly for mid range duties as it's all down to the size of the baffle as to how low you can go
 
as soon as the rear wave comes in contact with the front it cancels out so the bigger the baffle the longer the wavelenght will be before this happens
 
essentially you're only using the drivers suspension to control the cone
that results in a more natural sound apparently as you lose the boxiness but the downside is you also lose the loading characteristics a box gives you and so overdriving your speaker can become a problem
 
vocals are supposed to awesome through an open baffle setup
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Static Age View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Static Age Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2006 at 12:28pm
this is the first i have ever heard of this. so presuamably could you fit the baffle to some kind of skeletal frame to alow for stacking or does this open baffle system only work in line array?
 
when you say baffle size affects frequency response what size baffle is commonly used??
 
i'm off to google to find out more
 


Edited by Static Age - 29 June 2006 at 12:30pm
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kevinmcdonough View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2006 at 7:38pm
good link actually, very ineresting.


If i ever get some free time its deffo worth messing about with. Maybe just get a few cheep speakers and see how much they can be improved by the open baffle against a sealed or ported box.

k
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Static Age View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Static Age Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2006 at 4:09am

i was also thinking of experimenting too. got a couple of 10" drivers kicking about that i could use.

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Jay Lawless View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jay Lawless Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2006 at 5:27am
Originally posted by Static Age Static Age wrote:

i was also thinking of experimenting too. got a couple of 10" drivers kicking about that i could use.

 
as do i, they are really ment for Guitar open cab settups anyway, but i'll take a wake at it my self.
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Background: Automotive, Live and Home Custom Design. mid/high level based design and feild experience. Bass specialist
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JD01 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2006 at 7:43pm
This works very well for bass in terms of sound. The baffle doesn't need to be giant for this. Take a look at Siggy Linkwitzs design for a dipole subwoofer. If you build this thing with two professional 18" speakers you will get a sensitivity around 97dB 1W/1m and it goes flat to around 25Hz. I guess even with 1W the excursion will already be high, so the maximum SPL will be very limited. In addition to that no walls should be nearer than 1.5m to the sub. The Linkwitz design can be stacked vertically.
 
This design is NOT a 'Electrical power to sound compression zone' converter (like most common designs), but a 'Electrical power to sound rarefaction zone' converter. (In fact I don't know if I explained it correct in english, it's not my first language and scientific talk isn't easy...)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2006 at 4:13am
Open Baffles are odd beasts. For bass in rooms they are a bit of a fad. They excite modes in a different way being so-called velocity (and not pressure) transducers. They also don't benefit much from modal support below the primary mode in a room unlike monopoles and U Baffles. A couple of studies have shown that the reverberation reduction advocated by some is jus tnot there and that the same old addage that fast bass = no bass applies here as well.

That said, I have a freak speaker which employs 2 SN-15MBs on an open baffle and it has the side effect that musicians commented that they could play very close to ther speakers (excepting bass) without hearing much frmo them. They cover 230Hz-700/1k2 (depending in what mood I am in) between two 18" U Baffles.


Edited by Timber_MG - 01 July 2006 at 4:22am
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JD01 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 02 July 2006 at 10:36pm
Velocity, that may be the word I was looking for. Didn't know that was the right one.
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Tony Wilkes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 04 July 2006 at 4:52am
Some of the lowest bass I have ever heard (felt) was with a pair of old Fane 12" Hi-Fi drivers mounted in the centre of two pieces of 4ft square ply. These were in free space on the stage of my school hall.

The amplifier used must have been all of 6 watts/ channel and the turntable and cartridge was a modified Garrard SP25 mk1 with a Decca Deram ceramic.

I still remember the glorious bass to this day. The music was some church organ recital with 32ft bass pipes.


Tony


Edited by wilkee - 04 July 2006 at 4:52am
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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2006 at 9:48am
djk
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Tom Umney View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom Umney Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2006 at 5:41am
Originally posted by _djk_ _djk_ wrote:

http://www.mfk-projects.com/dipole_pa_system.htm
 
Nice looking system there.
 
I especially like how the bass bin is done. I wonder how it sounds and what it compaires to?
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