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Open baffle without limits
Open baffle without limits
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Old 17th April 2018, 07:45 AM   #1
ruairi is offline ruairi
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Default Open baffle without limits

Hi all,

I'm an audio pro in the early stages of learning about open baffle designs and will soon be trying some experiments. I know that open baffle speakers present some unique opportunities and challenges but I wanted to ask a question.

In a world without limits what would a possible "perfect" open baffle system look like? I'm talking a world where space is not an issue, the room can acoustically treated to optimize the performance, any drivers are available, any baffle size etc etc.

I'm imagining a 3 or 4 way system with ATC mids, fully active, DSP crossover, as much amp power as is needed. There's also no limit to driver count… how about 4 x 15" drivers for the bottom few octaves? You get where I'm going with this.

Thanks!
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Old 17th April 2018, 08:03 AM   #2
AllenB is offline AllenB  Australia
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If you cut a hole in a wall and put the driver in it, where the back faces outside the room, the result would be almost the same as putting it in a large closed box.
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Old 17th April 2018, 08:07 AM   #3
ruairi is offline ruairi
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Thanks Allen, I work in an extraordinary mastering room that uses large flush mounted ATCs. It's as close to perfect as one could ask for but I'm keen to explore the in room polar pattern effects of open baffle systems.

Linkwitz says we want the full audio range to be omnidirectional in an untreated room (MF and HF on rear as well as front). I'm curious what would happen with a large open baffle system in a room that has effective broadband treatment at each end with the baffle placed roughly halfway in the room ("nulls" facing the untreated or lightly treated side walls).
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Old 17th April 2018, 08:38 AM   #4
scottjoplin is offline scottjoplin  Wales
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Hi, can you link to where Linkwitz says that about omnis please, so that I'm clear about the context?
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Old 17th April 2018, 08:41 AM   #5
ruairi is offline ruairi
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From here - Conclusions

"If dipole behavior covers the full frequency range, then the room response becomes perceptually masked by the direct sound"

"The radiation from the rear of the cone must not be absorbed, but the distance to the nearest reflecting/diffusing surface should be at least 3' (1 m)."
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Old 17th April 2018, 09:12 AM   #6
scottjoplin is offline scottjoplin  Wales
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Ok thanks, I'm familiar with that page, "MF and HF on the rear as well as front" confused me. By effective broadband treatment I presume you mean absorption?
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Old 17th April 2018, 09:20 AM   #7
ruairi is offline ruairi
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Yes, sorry, a clumsy paraphrasing of his words (it had been a while since I read it).

And yes I mean effective absorption right down into the LF. I suppose I'm wondering if one can get some of the "non box" sound of open baffle without the more reverberant or live characteristics of the typical dipole in living room setup.

The last bass trap I constructed was just shy of 800 cubic feet and it was incredibly effective. We had the space (almost 1000 sq ft room) and the budget for a low tech solution and it was an absolute joy. I can imagine a room with a similar trap at each end and a large open baffle system near the middle.

What would that full range OB system look like? What would the baffle shape be if anything was possible? What would the driver compliment be for power handling and LF extension if anything was possible?
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Old 17th April 2018, 09:35 AM   #8
scottjoplin is offline scottjoplin  Wales
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The null to the side in practice isn't really much of one, you are still going to have side wall reflections. Usually a baffle as small as possible is used for, IIRC, two main reasons, for the best dipole radiation and not to block the front wall reflection (normally we want that). What you are describing sounds like it's approaching an IB as AllenB suggested. So, if there is no reflection to block and no real dipole radiation to accommodate, I'd suggest a large baffle, the larger it is the less cone area would be required.
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Old 17th April 2018, 09:38 AM   #9
ruairi is offline ruairi
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Thanks Scott, appreciate the input. This isn't a build plan right now but I do have Eminence Alpha 15A on the way, some ATC style mids and tweeters on hand as well as some very nice DSP crossovers and power amps. Basically I'm set up and short only a baffle, time and experience :-)
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Old 17th April 2018, 10:08 AM   #10
Upfront is offline Upfront  Australia
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Sounds like it's time to grab yourself a couple of sheets of ply and a saw mate!
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