Fostex FE207E MLTL Bipole?

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Please forgive me if this has been beaten into the ground, but I'm on a deployed Navy ship and the internet is too slow (it took me ~10 mins to open this page) to allow extensive searching. So I'm packing a little more in this post than normal.

I'm building a pair of 300B amps when I get back, have been ordering parts, and need to build some speakers also. I was going to build the single Lowther MLTLs, but figured I'd wait until I can put them in a proper back-loaded horn, and stick with Fostex for now. And I've always been interested in trying bipoles.

1. Are FE207E drivers a good candidate for Bipole MLTL cabinets? I've only seen fostex's 6.5" drivers in Bipoles, none of the 8"ers. Is there a good reason for this?

2. Assuming they would be good, could I just take Martin King's plan for single MLTL and double the cross-section to 11" x 19"? I would download his work sheets, but that isn't an option right now. And I want to have all the parts ready when I get back.

3. I understand baffle step wont be a problem, but would any other correction be necessary? I'm not super concerned with <70hz response, since I'm also going to build a Shiva sealed sub. But, I would like the most low end possible, just in case. The sub may have to wait.

4. This one is probably for a different forum, but if anyone here happens to know, how does Itunes EQ work? Is it DSP? Accurate? My setup is going to be "Mac Mini (lossless format)-> Lite DAC-Ah -> NAD Preamp -> JE Labs 300B". I was just wondering today if any tube people have tried using software EQ for "baffle step correction", "notch filters", etc.

thank you all in advance,

Jay Kickliter
 
Hi Jay

Don't think anyone's done a bipole MLTL with 8in drivers yet (though I speak under correctin of course). In answer to your questions

1) Yes, I don't see why not, though they'll be serious enclosures! I imagine the sheer box size is why you don't see them with the 8in drivers.

2) Mostly yes: if you have two drivers wired in parallel, Vas doubles, Sd doubles, Re & Lvc are half their original values. So doubling the CSA is fine -you'll probably have to make a few modifications to the vent though. I'm away to London tomorrow until Friday, but if I get chance I'll run a sim to check. Martin's actally got a new bipole sheet in the works, but that might come a bit late for you, as it probably won't be finished for another couple of months.

3) BSC is not an issue with bipoles, so no contour circuit is needed. The drivers will probably need a little series resistance though, as their Qt is still only 0.26 if memory serves. If you're building a pair of 300b amps, make sure it's got killer output transformers, or it might struggle a bit, especially if it's a low-powered variety.

4) Goodness knows. Digital Eq is a good thing though, and plenty of people who have valve amps use it.
 
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