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-   -   hubbel type error HELP ! (http://www.diyaudio.com/forums/full-range/67604-hubbel-type-error-help.html)

tenderland 9th November 2005 11:05 PM

hubbel type error HELP !
 
Iam building the recomended enclosure fro the fostex 166





T he proble is i measured all pieces in metric, however the thickness of the wood is .5 inch not 15mm. This causes a 5mm differnence from for
example the top port to the one down the front . Any advice on how to approach this error

Jeff
:dead:fe166

Scottmoose 10th November 2005 09:04 AM

Oh boy. Well, if the wood is already cut, there's not a whole lot you can do about it I'm afraid. Perhaps a trifle of [extra] stuffing in the compression chamber might help. If it's not yet cut, then you're going to have to go about the tedious proceedure of modifying all the dimensions one by one, manually, to account for the different wood dimensions -not a task that would inspire envy, and I wish you luck. Just do it all first, and triple check you've got it right before getting the old saw out, or you'll screaming blue-murder when a couple of parts don't meet up! Trying to convert one pice, build it, then convert another and build that is just looking for trouble.

My take? I don't honestly think it will make a great deal of audible difference, if any. I could be way off the mark with that, other people here with more knowledge about these horns / series of expanding transmission lines etc can advise better, but I reckon that I'd just mutter an oath about the metric system that's caused the world so many problems when it collided with the established Imperial system, have a glass of something mellow and red, forget it ever happened and just get on with the construction and not worry about it.

My favourite example of dimensional problems? The Thor TL. Dr Joeseph D'Apollito rigourously followed a set of (Ausberger's now superceeded) TL alignment tables, then arbitrarily threw away a whole 1/3 of the cabinet volume the tables specified. Inevitable result -seriously compromised bass performance over what it could have been, a mistake disguised under the original measurements (I merely state, I imply nothing) of shorting out one of the two mid-bass drivers, which effectively doubled the cabinet volume temporarily. Yet most builders of Thor love it. Now, in comparision to that, although a very different cabinet type, the error you have is very small. Draw your own conclusions.

Good luck and enjoy!
Cheers
Scott

tenderland 10th November 2005 05:48 PM

solution
 
Thank you scott for the reply . Here is what i decided to do

the port on the top is 55 mm , the port along the front turned out to be 60 mm. 2.3 mm diifference from .5 inch to 15 mm.
i amd going to make piece 6, and piece 8 longer by 5 mm.
My reasoning is it is better to have the cavity a bit longer and
and have the cavitys the same volume. this does create 5 mm wider in the back cavity but all other dimensions are ok

Jeff

Scottmoose 10th November 2005 09:28 PM

Sounds sensible to me. Good luck with the project!

Best
Scott


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