FE166e in Folded Voigt Pipe? - diyAudio
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Old 14th October 2005, 09:58 PM   #1
zBuff is offline zBuff  New Zealand
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Default FE166e in Folded Voigt Pipe?

I've planning to commence my first speaker building project for some time now, I was going to follow Fred's Voigt pipe design for the foxtex FE166e. http://fredt300b.smugmug.com/gallery/147575
I've got the drivers already.

But due to Wife Acceptablity factors I've got to have a less intrusive profile for it to remain in the house after I've built it. So how to I go about modifying the design so it is a folded Voigt pipe instead?
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Old 14th October 2005, 10:42 PM   #2
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Well, you can fold it. I wouldn't bother though: don't even think about using the FE166E in a TL is my advice. And avoid the 'traditional' Voigt pipe (created by the Lowther Club of Norway in what I can only assume was a moment of madness) like the plague. This is not a good driver / cabinet combination for a number of reasons. Have a look here for more information on this cabinet:
http://www.geocities.com/rbrines1/Pages/Voigt_Pipe.html

The cabinet coming to a point is not a good thing generally -you get a horrible and severe ripple effect. And the FE166E, with its low Q and naturally rising response thanks to the Lowther-like power of its magnet is going to need a high level of correction to bring it into line. Only Terry Cain has managed to combine a TQWT with the FE166E well to my knowledge, and the exact internal dimensions of his Abby are understandably kept quite close to his chest, it being a commercial product.

My suggestion: you obviously want a TL type enclosure, which is fair enough, but of a size and shape closer to a traditional floor-standing speaker, yes? OK, that's easy. Firstly, forget the FE166E, and go for its sister driver, the FE167E, which is much more suitable to resonant enclosures, and will need far less correction. You could build the folded version of Martin King's superb Project 2 ML TQWT from the plans Bob has put on his site here: http://www.geocities.com/rbrines1/Pages/Proposals.html I have built 3 pairs so far of the original, unfolded type, and they are superb. The folded version Bob has drawn should perform pretty much as well as Martin's originals.

Alternatively, splash out and spend $25 on a set of the plans Bob sells for his FT1600MK2, which is even better, and well worth the little money he asks for: Bob is the master of refining designs. You'll get a series of superbly detialed diagrams, cutting plans, and all the help you could ever need. http://www.geocities.com/rbrines1/Pa...MkII/Main.html

Either way, you'll get a much better speaker at the end of it, and one which will outperform most anything at twice or 3 times the price. In some ways such as transparency, they're pretty much as good as anything available, regardless of cost. Good luck

Regards
Scott
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Old 15th October 2005, 03:46 PM   #3
Tweeker is offline Tweeker  United States
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Another Terry Cain 166e pipe. I think the FE166 needs a big enclosure to work in a pipe. You might be able to get it to work in places more suited to an FE167 with some series resistance to raise its q.

Folding it you keep the relative position of the driver from the pipe end and total pipe length and taper similar, probably turning it upside down to do so. You end up with a smaller bafffle and driver near its top instead of in its middle, Im not sure how much effect this has.
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Old 15th October 2005, 09:29 PM   #4
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None, frequency response will be unaffected by a single fold, so long as the basic parameters are not changed. Like Bob, I personally wouldn't use any of the FE**6E series drivers in a resonant enclosure: they're for horns really. The FE**7E series need less correction to bring them into line, and the less correction needed the better in my view. They also generally produce better bass in these enclosures.

I know Terry's Bigger Is Better box well; it measures better than it simulates, but while we're on the subject, I'd make a few changes to make the most of the geometry. My version on the theme: Fostex FF165K (Okay, okay, a low Q driver, but we all have an exception to our rules, yes?!?). So=0.25Sd (one of the few occasions I'd use an area of less than Sd -it doesn't affect the predicted response), Sm=5Sd. 128" pipe length. Driver mounted at 28% of line length. 0.4 lbs to cubic foot of stuffing above the driver and a layer on the base. Mass load it rather than leaving the top completely open. A 2"x2" circular port will do the job. I leave the width and depth of the cabinet open to taste. They give an interesting response: flat from 25Hz to 100Hz, a sudden 6db lift at 100Hz, then pretty much flat again until the drivers roll off. Adding some series resistance (about 4ohms) will probably help there, along with a basic BSC circuit. With that, they should thunder.
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Old 15th October 2005, 09:57 PM   #5
Tweeker is offline Tweeker  United States
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I know the pipes response will remain quite similar, but would there not be at least a small degree of change in baffle step behavior?
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Old 15th October 2005, 10:12 PM   #6
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Not really, that's more an enclosure width feature than height. If there is, it'll be minimal.
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Old 16th October 2005, 02:07 AM   #7
zBuff is offline zBuff  New Zealand
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Thanks for the replies guys.

So am I out of luck with these FE166e I've already purchased? I would attempt the fostex design given with the speakers, but I think my woodworking skills would let me down. Or is it not as hard as it looks to get it all square? Or are there any more simple horn designs around that I could attempt? The problem with the profile is only it's height so going wider or deeper wouldn't be so much of a problem.
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Old 16th October 2005, 02:56 AM   #8
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Quote:
Originally posted by zBuff
I would attempt the fostex design given with the speakers
The Fostex designs aren't material efficient, but with only 90 degree cuts and no angles is really just a lot of pieces.

dave
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Old 16th October 2005, 02:58 AM   #9
GM is offline GM  United States
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Quote:
Originally posted by Tweeker
I think the FE166 needs a big enclosure to work in a pipe.
Greets!

Good, that makes two of us!

GM
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Old 16th October 2005, 03:04 AM   #10
GM is offline GM  United States
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Quote:
Originally posted by zBuff
So am I out of luck with these FE166e I've already purchased?
Greets!

That depends on how tall you can tolerate and what min. Fb suits your app.

GM
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