Fostex FE207E with Eminence Alpha 15 open baffle

[HiFiNutNut]

Using such a wide baffle moves the first dipole null lower that would be very difficult to deal with in an XO. You can simulate the baffle response from Edge, BSC and A B C Dipole.

[barackuda]

Hi folks....i am very interested in such design, like felixxx build him self.is there any proven or well known design that i could "copy"? i mean drawing, drivers used, wiring, etc etc.....you know, everithing allready done.I've searched the forum, but the search engine give strange results....

Thanks alot.

[sharpi31]

Well I have been enjoying the speakers for a month or two now, and am very happy overall. There is no shortage of bass weight or warmth, but the detail and imaging are also excellent.

[sharpi31]

I am currently using a series first order crossover (4.1mH air core inductor and 75uF caps). Today I received some new monster Russian military PIO caps from Estonia (below) and am keen to try pushing the crossover point down an octave or so to about 145Hz. Two of my new caps measure the same at 114.3uF, so I will first try 7.0mH inductors and take it from there.

Will the fostex be happy working down to to this point? With a 145Hz crossover the fostex will be 6dB down at 72.5Hz and 9dB down at 36.25Hz, which I hope should prevent over excursion of the driver.

Any advice would be appreciated :-)

[sreten]

Originally posted by sharpi31
I am currently using a series first order crossover (4.1mH air core inductor and 75uF caps). Today I received some new monster Russian military PIO caps from Estonia (below) and am keen to try pushing the crossover point down an octave or so to about 145Hz. Two of my new caps measure the same at 114.3uF, so I will first try 7.0mH inductors and take it from there.

Will the fostex be happy working down to to this point? With a 145Hz crossover the fostex will be 6dB down at 72.5Hz and 9dB down at 36.25Hz, which I hope should prevent over excursion of the driver.

Any advice would be appreciated :-)

Hi,

Hand waving I'd say it would not work well as the fostex is too
near the edge of the baffle, you will have substantial baffle loss
for it at 140Hz, but suck it and see. You may have to go series
capacitor on the fostex and higher 2nd order on the Alpha.

/sreten.

[Geoff H]

By all means give it a go. If sreten's warning is valid, and I think it is, a "shelf" above the main driver could be a solution.

I prefer the crossover to the main as low as 80 Hz. Can't always get there.

Have a look at: www.contrabass.com/pages/frequency.html

Good luck,

Geoff.

edit: the series xo is the way for passive use. You need to take into account the z at such low freqs, usually much higher than nominal.