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Old 15th June 2012, 03:52 PM   #1
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Default Open Baffle / Horn Hybrid

I've been lurking on on the forum for about 12 months and thought it was about time I posted something. I've become a bit obsessed with the idea of a full range open baffle ever since first reading about dipole speakers. I liked the idea of full ranger partly because of what people said about them but secondly because I didn't have the expertise to get into crossover design... I promptly bought a some full range drivers and began experimenting. I quickly became hooked on the openness of the sound and have since become pretty much obsessed the idea of designing a practically sized full range open baffle speaker that produces enough bass.

After numerous (Failed) protypes and quiet a bit of reading I've finally arrived at a design concept which I''m hopeful about and I'm interested to know what the minds greater than mine think of the concept.

The idea is to use 2 drivers... one in an open baffle back to back with one placed in a horn. The horn would have the driver firing inwards and would be wired out of phase. The idea is that the back driver would effectivley cancellout the back waves from the open baffle adn great a kind of 'dead zone' behind the baffle. hopefully this would reduce baffle step issues as well has ensure there are no back reflections to the front driver.

As the back driver fires into a quarter wavelength horn it would also extend the bass to something closer to full-range.

Anyway, I've greated some a crude 'sketchup'; to illustrate the idea... I still need to work out the specifics of the horn path but it should be enough to give an idea of my thinking...I'm just wondering if anyone had any thoughts' or had perhaps seen anything like this done before.

Click the image to open in full size.

Click the image to open in full size.

Any Thoughts?
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Old 15th June 2012, 04:37 PM   #2
chrisb is offline chrisb  Canada
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You might have trouble attaining much SPL/bandwidth from the OB driver without some degree of filtering - but not necessarily as complicated as a full blown XO / EQ/BSC etc.


that said, just build the darn things
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Old 15th June 2012, 04:54 PM   #3
boris81 is offline boris81  United States
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It looks interesting but I'm not sure anything is gained over a regular Transmission Line design.
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Old 15th June 2012, 05:33 PM   #4
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My hope is that it will retain some of the qualities of an open baffle as well as the benefits of TL. being a bit of a noob it could be that I'm mistaken about the benefits of OB and having not heard anyone elses TL I can't really make proper a proper comparison. Thanks for the feedback.
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Old 15th June 2012, 08:59 PM   #5
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I like it.

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Old 15th June 2012, 10:30 PM   #6
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would this not just work like a leaky isobaric setup, only not as well?
surely you're still going to get colouration etc from the 2nd driver in the T/L enclosure, so negates the point in using open baffle? and because the 2 opposing drivers aren't sealed up, they're not really going to perfectly cancel each other out, so you'll get odd noise from there too?
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Old 16th June 2012, 01:50 AM   #7
Bigun is offline Bigun  Canada
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very inventive !

Here's my thoughts - from a non-expert mind.

The OB with a single driver didn't have enough bass. You believe the biggest issue is the cancellation of the front wave by the wave emitted from the back of the driver. So, it's clear that the back wave from the driver has a big impact on the sound. And so the quality of the sound depends on the properties of the back wave.

So unless you cancel the back wave accurately, the 'error' will contaminate the sound even if you improve the bass. I assume that the 2nd driver will not behave like the front driver because it is loaded with a TL. This means its output will be different from the front driver so it can't accurately cancel the back wave of the front driver. The TL has a terminus, any sound emitted from it will also wrap around to the front. It will be time-shifted by it's travel down the TL and it's bandwidth with also be limited. This will also contaminate the sound.

But it might work just great - only way to find out is to try it out !

fyi - I recently came across a design that has drivers on the front and on the back and a TL between them. The two sets of drivers shared the TL. http://www.troelsgravesen.dk/JA8008_DTQWT.htm
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Last edited by Bigun; 16th June 2012 at 01:54 AM.
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Old 16th June 2012, 06:25 AM   #8
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Thanks for the feedback guys... All food for thought.

To try and maximise the 'cancelling' properties of the second driver i'd make sure the physical layout of the middle space was symetrical. As bigun says you'd still get the colloration from the back driver. In my head i'm thinking that the sound you would hear within that back space would almost all be the colloration in fact butmy hope is that much less of this will make it to the listening position though i realise whether this will be the case or not will depend on the frequencies at which the horn collartion occurs.

By the way... It's not on the design but i'd also add felt wadding to the internal surfaces as well as well as some kind of interior baffle to prevent direct waves from each driver hitting each other.... I'm thinking this could be incorporated into some kind of brace between the drivers.

Chrisb-i understand your comment about the spl from the open baffle would be low but would the spl of the whole system but not comparible to astandard single driver TL?

At the end of the day I might just have to build it and see.
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Old 16th June 2012, 07:24 PM   #9
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Really interesting design, I say try it and see if you like. BTW, which driver are you thinking of using?
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Old 16th June 2012, 08:37 PM   #10
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I've got four fostex fe126en's i thought i might use... Not sure if they're the right one's for the job but i'll see what happens.
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