Open Baffle Project

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Ray P
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#1 Open Baffle Project

Post by Ray P »

I've wanted to try an open-baffle project for a while but have never quite gotten around to it but the recent mention of Nick's OB from a few years back on the sub-woofer thread got me thinking again...

Just for completeness, here's the general recipe, copied over from the sub-woofer thread;

> a)Fostex FE 167E
> b)Eminence Beta 15
> c)Crossover at 150-200Hz 6DB octave
> d)Series connection of drivers
> e)inductor bypassing Fostex (value still being tweaked but about 8mH)
> f)capacitor bypassing Eminence (value still being tweaked but about 80uF)
> g)Front of baffle 450mm wide 1350mm high sloped back 5 degrees
> h)sides 500mm deep and sloping in a constant line up to the top of the baffle (this isn't optimum - Quasar shape is but this works pretty well and is good for starters)
> i)bottom piece 450mm by 500mm with an air tight seal to front and sides (very important) - bottom shaped like Quasar is best but this is close
> j) Fostex mounted about 750mm above floor
> k) Eminence mounted about 100mm -150mm above the floor
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Ray P
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#2 Re: Open Baffle Project

Post by Ray P »

The aim of the project is to get some exposure to what OBs can do without breaking the bank so a well regarded but cost effective design, such as Nick's, seems like a sensible starting point.

The completed OBs will sit in front of alcoves either side of a fireplace, I'm assuming about 3ft out into the room.

Fortunately, there are only the two of us in the house, our sitting room is fairly large and my partner loves her music so I'm not overly constrained by WAF/family considerations.

Ray
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#3 Re: Open Baffle Project

Post by Ray P »

To get things rolling I've agreed a deal to purchase Phil's pair of Fostex FE167E drive units, which I plan to pick up at Owston in a couple of months. That means the project will take a little time to get rolling but in the meantime I can scout for a pair of the Eminence units and start working on the baffles and bounce a few ideas around.

Ray
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Paul Barker
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#4 Re: Open Baffle Project

Post by Paul Barker »

The only thing I will say is that the Briggs dimensions which emulate the Quad 57 dimensions give or take are where the magic lies. I don't (can't?) use those dimensions in general room at home. But I have used it in a man cave and the sound was my best ever. There used to be a far east blog (before the term blog was common language) all about these magic dimensioned OB's. Probably all gone now, unless its still on waybackmachine or similar. But I couldnt tell you the words to search to find it.
Last edited by Paul Barker on Fri Apr 14, 2017 7:41 am, edited 1 time in total.
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Ray P
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#5 Re: Open Baffle Project

Post by Ray P »

Greg was kind enough to post a picture of the open baffles on the sub-woofer thread so I've copied it below for reference;

Image

Nick's OBs are the inside pair with James D's Quasars outboard of them.

Ray
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#6 Re: Open Baffle Project

Post by Paul Barker »

Yes mine were the poundstretcher vesrion on the flank.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Ray P
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#7 Re: Open Baffle Project

Post by Ray P »

Thanks Paul.

How were they?
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pre65
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#8 Re: Open Baffle Project

Post by pre65 »

Ray, if you remind me before Owston I'll throw in the two inductors I was using.

They are only cheapies, but will establish the value before splashing out on expensive ones. I seem to remember Nick saying that the inductor value was not critical.
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Dave the bass
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#9 Re: Open Baffle Project

Post by Dave the bass »

Paul Barker wrote: Fri Apr 14, 2017 7:42 am Yes mine were the poundstretcher vesrion on the flank.
....Replete with "sound-pushing-forward-exposed-screw-threads" IIRC :)

That was my intro to you lot at Eggy. I thought to myself "I like this lot" :lol:
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#10 Re: Open Baffle Project

Post by Mike H »

Image

Watching.


.
 
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pre65
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#11 Re: Open Baffle Project

Post by pre65 »

Dave the bass wrote: Fri Apr 14, 2017 9:57 am
That was my intro to you lot at Eggy. I thought to myself "I like this lot" :lol:
Same here Dave, first time we met, you took a phono stage from memory ?
The only thing necessary for the triumph of evil is for good men to do nothing.

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#12 Re: Open Baffle Project

Post by SimonC »

Ray P wrote: Fri Apr 14, 2017 7:30 am To get things rolling I've agreed a deal to purchase Phil's pair of Fostex FE167E drive units, which I plan to pick up at Owston in a couple of months. That means the project will take a little time to get rolling but in the meantime I can scout for a pair of the Eminence units and start working on the baffles and bounce a few ideas around.

Ray
Hi Ray,

I have a pair of 15" Eminence Beta's you can have on extended loan to get you going if you don't manage to find any before Owston. My circumstances (both location and time to build anything with them) have changed since I acquired them and it would be good to hear someone making use of them. Eventually I'll beg them back, but it won't be for a few months/years. I need to put in a couple of RSJ's, remove a wall and build an extension first :)

Let me know and I can drop them in the car for Owston.

Simon C
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Greg
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#13 Re: Open Baffle Project

Post by Greg »

Yes, Paul's 'Poundstretcher' crossover within the rear of the 'Cabinet Maker's' baffle :D Just goes to show you can never have enough clip leads. Actually, all joking aside, as an experimental build, they sounded great and showed the potential for a proper solid build. I liked them :thumbleft:

Image
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#14 Re: Open Baffle Project

Post by Mike H »

That is one helluva air-cored choke :shock:
 
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#15 Re: Open Baffle Project

Post by Cressy Snr »

Twisted twin CAT5 speaker cable....anybody still using that?
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