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AudioGeek 7th April 2008 08:45 PM

fe167e and Alpha 15a OB arrived
just got going a fe167e and Alpha 15a OB. Thanks MJK for your website.

sounds great so far and running them both fullrange till i get the x-over built. even with no x-over sounds very very good.

very open and airy. detailed. relaxed sound. bass is good for a passive ob.

probably go with the x-over MJK mentions if no one has anything that would work better.

maybe go with those phase plug things also.

any ideas for x-overs?

pictures to follow probably.

AudioGeek 7th April 2008 09:24 PM

2 Attachment(s)

AdamThorne 7th April 2008 09:56 PM


How much power are you giving 'em?

Look forward to hearing your thoughts once you get the crossover in...

AudioGeek 7th April 2008 10:16 PM

err pp 6b4g's so 12 or 14W.

not too much.

my amp is in the picture along with cd player and passive pre.

MJK 7th April 2008 10:38 PM

The only potential problem I see with your set-up is that the FE-167E is 94 dB/W/m efficient and the Alpha 15A is 97 dB/W/m as predicted in infinite baffles. My original design targeted a 90 dB/W/m finished system efficiency with a smaller full range driver. You will need to be careful with the crossover to get them to blend and produce a flat SPL response. Maybe allow the FE-167E to run full range and only crossover the Alpha 15A so it helps offset the open baffle roll-off. Or maybe pad down the FE-167E a few dB and crossover both in the 200 Hz range similar to the original design with the FE-103E. The default set-up in my three driver OB worksheet uses the FE-167E and two Alpha 15A drivers and it is predicted to work extremely well (see the pdf on my Models page). If you can handle the level mismatch correctly, I think your system will be outstanding.

skorpion 7th April 2008 11:32 PM

Or as Martin's OB 3 model suggests, crossover bass at 200, fostex at 300 and pad down treble 5 db ! ;)


AudioGeek 7th April 2008 11:51 PM

is that x-over points and padding down for 1 fe167e and 1 alpha15a per channel?

any ideas for what values of cap and inductor for the drivers?

or should i just use a notch filter on the fe1673 to reduce shout?

i want to filter the fostex for the bass.

listening right now i really do not feel that the fe167e is that more sensitive.

but padding down the fe167e might make it sound EVEN BETTER!!!

ronc 8th April 2008 03:41 AM

I totally agree with Martin. Please add an L pad.


skorpion 8th April 2008 10:44 AM

Crossovers are Linkwitz-Riley 12 dB/octave. You can use the lowpass part from MJK's design. For highpass I suggest you use my values from 'The Volks-OB' : , 30 uF Obbligato capacitor and 8 mH inductor. Obbligatos are available from DIY Hi-Fi Supply and are really good and cheap: The L-pad could consist of 3.3 ohms in series and then 11.5 ohms over the Fostex, that should give an unchanged 8 ohm impedance for the crossover.


AudioGeek 8th April 2008 12:20 PM

so for low pass use the 9mH and 68uF.

High pass use 8mH and 30uF. Use a l-pad of 3.3 and 11.5 ohms.

would these values work for my application?

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