Open Baffle Epiphany!
- Thread starter cptnCanada
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Poultrygeist
Lunatic Member
Thanks Wes
TubeHiFiNut
Super Member
@PG - Of your various builds, which do you feel offers the greatest sonic advantages? The single OB with the drivers mounted vertically? The H-frames for the subs with smaller OB's on top for the FR? The folding screen?
This might be a goofy question, BUT since my brain is bored and working overtime, just out of curiosity: I've seen many OB designs that use a panel with fold-back wings.
Would there be any advantage, or more so, disadvantage to adding wings in the front along with the ones in the back? Would it hinder the sound in any way?
I have only seen one builder do this and he didn't get into much detail...Thanks!
Would there be any advantage, or more so, disadvantage to adding wings in the front along with the ones in the back? Would it hinder the sound in any way?
I have only seen one builder do this and he didn't get into much detail...Thanks!
Porkloin
Oscar Heil Groupie
Good thinking. But now I'm a little confused as to whether I'm posting in an OB thread or a single driver forum.
TubeHiFiNut
Super Member
Be happy to discuss using AMT's or any type of tweeters to augment the highs on a 3 or more way OB.
The University 6201's I currently have mounted in a home made JE Labs OB are coaxial drivers, 12" woofer crossed over to a horn tweeter.
I also have plans to have another pair of the JE Labs OB's built, pull the Altec 604's from my Karlson enclosures and use them as OB's. I got a third pair of Eminence Alphas to put back in the Karlsons for use as subs.
Back to the AMT's.....I no longer have a pair of them, another pair of tweeters that I would really like to have back. Never used them with Open Baffles but did with horns and dynamic speaker systems. They are outstanding. As I stated earlier, for this build I want to keep things simple so that I can really dial into the sonic signature of the Tang Band. Running it FR is the best way I know of to do this.
So....for the time being, I am not planning on using any additional high frequency drivers but would be really interested in hearing how you have integrated your AMT's and with what speakers.
here's a top view sketch of what I'm talking about (cross fingers, hope it loads)
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Seppo
Super Member
Infinity RS-II (and IRS and even modern top of the line Genesis ones) have convex curved wings. The brochure for RS-II discusses why the reasoning:
http://www.infinity-classics.de/mod...6/Reference-Standard-II/RS_II_Brochure_02.jpg
Basically the properly curved convex shape reduces forward scattering of the diffracted waves, improving the phase coherence of the wave field propagating forward and to the sides.
If one has wings tilted forward, i.e. concave wings, you would to my understanding increase forward diffraction resulting to additional incoherence in the forward propagating wave form, resulting to blurred sound...
Seppo, thanks for taking the time to answer. It all makes good sense.
Though after looking at the sketch a few times I began to wonder if the front wings wouldn't act as a loaded horn in some odd way. :scratch2:
BTW, one consideration I had for an OB build was similar to the one you posted, enclosed woofers with an OB full range in a tower line array design.
Though after looking at the sketch a few times I began to wonder if the front wings wouldn't act as a loaded horn in some odd way. :scratch2:
BTW, one consideration I had for an OB build was similar to the one you posted, enclosed woofers with an OB full range in a tower line array design.
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TubeHiFiNut
Super Member
From the Lowther America site:
http://www.lowther-america.com/page2/page12/Large%20Open%20Baffle%20Lowther/Large%20Open%20Baffle%20Lowther.html
http://www.lowther-america.com/page2/page12/Large%20Open%20Baffle%20Lowther/assets/LOB.pdf
Sounds like they are on the same page with a curved front baffle?
http://www.lowther-america.com/page2/page12/Large%20Open%20Baffle%20Lowther/Large%20Open%20Baffle%20Lowther.html
http://www.lowther-america.com/page2/page12/Large%20Open%20Baffle%20Lowther/assets/LOB.pdf
Sounds like they are on the same page with a curved front baffle?
Poultrygeist
Lunatic Member
It's hard to say. I really enjoyed the TB and Beta12LTA over H-Frames but then went with the DX3 with dual Alphas on a flat baffle. I need to try the DX3's over H-frames to form a better opinion. Dual H-frames ala MJK may be the best yet if you've got the real-estate.
The folding wings are too massive and difficult to move out into the room when you want to play them and like any other OB they require bass augmentation.
TubeHiFiNut
Super Member
You make a very persuasive case for the dual H-frames and I note that MJK features them on his site prominently.
Does semi enclosing the woofers alter the sound? Kind of like a semi-horn loaded woofer? Or is the effect not noticeable?
One thing for sure, going dual H-Frames would allow me to use the same woofers with all three OB's I plan to have available: TB's, 604's and 6201's. This way I could build additional JE Labs designed OB's for the 604 and TB's as i used for the 6201's and eliminate one variable when comparing the three drivers. Just use the dual H-frames as stands for the JE Labs designed OB's. :scratch2:
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PR Audio
Super Member
Besides SEPPO's explanation, which applies to wings, but not necessarily a folded OB, in OB you need a front baffle of certain size, sometimes the width of the baffle is too much, so folding them (wings) gives you the baffle width needed (front + sides) without the extra footprint. If I'm mistaken, someone else here can elaborate.
TubeHiFiNut
Super Member
Been reading up on Open Baffle design theory trying to see if there is some kind of ratio between driver size and baffle width. Also if there are different baffle width considerations for subs and FR drivers.
PR Audio
Super Member
Not an expert by any chance, as you guys I'm learning as I go along, also read a lot on the subject. I don't think there is a ratio, as each driver has different design parameters (Thiele-Small), using those parameters is that one can determine how the baffle size will affect the sound. Personally, I use The Edge software to see how will the driver react, not only the driver brand/model affects the design, but also the baffle size and location in the baffle. I'm playing right now with position and size of an OB for a 4" Mark Audio CHR70.3 full range driver. There is a 3.2Hz bump at around 12KHz, with adding couple of inches and moving the driver eccentrically to one side I was able to tame that bump to no more than a 2.7Hz rise, I could do it also electrically, but rather do it mechanically. Again, learning and understanding as I go along.
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That Infinity brochure reads more like marketing than engineering. I believe that sound waves moving along a baffle have to be perpendicular to the baffle, the two pictures seem to defy what I have seen and read about wave propogation. The discussion reads nicely but I do not think it is technically correct, be careful drawing any conclusions based on those pictures.
TubeHiFiNut
Super Member
That is my understanding, but only through reading the discussions of those far more knowledgeable than me.
I am also curious about the correlation between baffle width and high frequencies?
BHamm
The pendulum swings.
Baffle width seems to be more critical than height. Can I lengthen the MV Model 3P baffle adding 16 inches between drivers? That would put the Fostex at seated ear height. Would this alter the crossover design function?