bipole transmission line fe167e problem / questions.
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 18th March 2005, 11:20 PM #1 diyAudio Member   Join Date: Jan 2004 Location: Minnesota bipole transmission line fe167e problem / questions. i want to build a bipole transmission line FE167e with 2 fe167e per channel. straight pipe similar to this: http://www.t-linespeakers.org/projects/tlB/index.html problem is i don't know what size of enclosure... first thing is to determine 1/4 wave length at drivers Fs correct? in this case it is 50Hz so the line should be around 5.5 ft high correct? stuffed it should bring it down to the 1/4 wave length to around 2.5 ft high? is this correct? so which do i use? the Sd of both drivers together is 40 sg inches.... so the pipe area should be around 48 to 80 (1.2 to 2 times Sd)... I tried D/L the mathcad worksheets and couldn't figure it out. can someone quickly run the numbers and tell me if I am on the right track? Thanks! __________________ It is not you... you are it.
 19th March 2005, 03:07 AM #2 diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. Greets! >first thing is to determine 1/4 wave length at drivers Fs correct? in this case it is 50Hz so the line should be around 5.5 ft high correct? stuffed it should bring it down to the 1/4 wave length to around 2.5 ft high? is this correct? ==== ~13560/4/51.5 = ~65.8" less the terminus end correction. No, it won't shorten it that much, but this much stuffing will 'suck the life' out of a FR driver if it's not a very hi-Q one so I don't recommend so much stuffing it shortens the line. ==== >the Sd of both drivers together is 40 sg inches.... so the pipe area should be around 48 to 80 (1.2 to 2 times Sd)... ==== It's a function of Vb divided by line length. Minimum Vb appears to be ~2.26ft^3, but some series R is required to flatten the response so assuming 4 ohms, we now ideally need ~12.23ft^3: L = 59.125" CSA = 323.329"^2 (~7.86 x Sd) driver down 26.21" stuff to suit No BSC should be required in a typical size room and spaced up like the example will get the drivers up to ear height. ==== >I tried D/L the mathcad worksheets and couldn't figure it out. ==== It's pretty simple really, what couldn't you figure out after reading his various docs? GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
 19th March 2005, 04:35 PM #3 diyAudio Member   Join Date: Jan 2004 Location: Minnesota well... i d/l the mathcad explorer 8 and the various files for TL and TQWT designs.. but when I tried to load those files the explorer 8 just went to its opening screen and no TL equations or data... 12 cu ft is a lot of enclosure... do you have the response curves?? i kinda wanted to run the 2 drivers with NO series resistance... also i was thinking of a straight pipe with the drivers at top and opening at bottom... similar to link i provided. can you provide me with the formulas you used? or did you use the mathcad worksheets? Thanks!!! __________________ It is not you... you are it.
 21st March 2005, 04:19 AM #5 diyAudio Member   Join Date: Jan 2004 Location: Minnesota well... hey thanks for the detailed reply. anyhow... i guess what i really care about is being able to run them as bipoles and fullrange. how would a ML-TL look for a bipole design? or perhaps just a simple BR design? maybe 2 "ports" one on front and one on back? Thanks! __________________ It is not you... you are it.
diyAudio Member

Join Date: Dec 2001
Location: Germany
Quote:
 how would a ML-TL look for a bipole design?
Iīd guess the simplest you could do is take Bob Brines FT1600 and just double the cross-section-area.
http://geocities.com/rbrines1/

Youīll find some ML-TL bipole examples here.
Examples with a FE-126/7 : diyAudio Full Range Reference Project

I just build a BR for the FE-167E (15l recommended) and have to say it was not really worth. Itīs nice but bass is a bit light (no problem in small rooms though and/or with a sub)and well, you need a stand anyway so could rather do a floorstander from the beginning on.
The BR would certainly be enough for a rear speaker in a HT-setup.(IMO)

greets
__________________
jens

diyAudio Member

Join Date: Jul 2003
Location: Seattle, WA
Quote:
 I just build a BR for the FE-167E (15l recommended) and have to say it was not really worth.
I did too out of curiousity and came to the same conclusion.

diyAudio Member

Join Date: Sep 2003
Location: Bay Area, CA
Quote:
 I did too out of curiousity and came to the same conclusion.
Oh wow, I'm just about to finish up a pair of these and now everyone is abandoninig these drivers in BR boxes!

Paul Joppa from Bottlehead gave up and now here are two more who are ready to throw in the towel. Oh well, it didn't cost me anything but time since I already had the drivers and some extra wood lying around. I'll finish them up anyway and give them quick listen and hopefully wlll come up with a "different" conclusion.

 21st March 2005, 08:11 PM #9 diyAudio Member   Join Date: Dec 2001 Location: Germany Donīt get me wrong I really like īem, itīs just that I donīt have a proper speaker stand and prefer listening to music without a sub. (which it needs in my room) Give yourself some time with the speaker. Depending on your room you might very much like it as it is. Try it with a sub if you have one. Quite a marvellous combo for itīs simplicity. I guess also that the Fostex recommended is not the last word on BR. If itīs supposed to be a BR, maybe it should be more like the Omega Grande 6 having more than 20l (>0.7 cu.ft). FT1600 is on the list as well... __________________ jens
 21st March 2005, 08:13 PM #10 diyAudio Member     Join Date: Jul 2003 Location: Seattle, WA They're not awful, it's just that they will definitely need low end support. If that's your goal then it will work well. AudioGeek: I think GMs numbers are good to go with (sure is a big box). You mentioned that you didn't like the idea of a series resistor but my experience has been that they can be quite beneficial. Another option would be to wire the drivers in series but in this particular situation I would go with parallel wiring and a series resistor first. Personally, I would shy away from a box that size but there's always a compromise. You could build a bipole with the WR125ST but you'd have to give up efficiency. Not a lot, but some. Add a super tweeter and you're in business.

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