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Old 29th September 2013, 05:46 PM   #1
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Default Fostex Factory BR alignments

A FWIW post. When these drivers first came out I had a quick look at the various BR alignments they provide for them; as I was cleaning the HDD I ran across them & thought they might be of interest.

Some general points. This is from WinISD-pro, which I use for checking consistency of published T/S specs. Factory parameters, Vas may be slightly different as I derive it from the other values, since it's often the hardest to measure. Anechoic IB FR plots (obviously), assuming voltage sources unless otherwise stated. No damping assumed, so if the boxes are lined, then you'll get a little more LF damping. Ignore everything > 1KHz.

3in drivers = yellow
4in drivers = blue
4.5in drivers = orange
6.5in drivers = violet
8in drivers = green

One additional point. When we say the Factory cabinets were designed for the En series drivers, they're weren't. They were designed for the defunct E series units, which in several cases (officially) had somewhat different specs., but have carried over to the new drivers.

Last edited by Scottmoose; 29th September 2013 at 07:53 PM.
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Old 29th September 2013, 05:47 PM   #2
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FFxx5wk boxes.

General thoughts. The 85 box is likely to be irritating with that peak at Fb. The 105 box is also a bit under-damped so avoid boundaries. The 125, 165 & 225 alignments aren't bad; relatively well damped, should be fairly flexible in terms of positioning, amplifiers etc. How much of a shelving filter you'll need for step-loss (if any) will depend on the amps & placement, obviously. This isn't taking linear deflection into consideration; the smaller units will have less dynamic range for obvious reasons, although Fostex units tend to compress relatively gracefully compared to some other short VC drivers.
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Last edited by Scottmoose; 29th September 2013 at 05:51 PM.
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Old 29th September 2013, 05:52 PM   #3
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FFxx6En boxes.

Assuming a voltage source and typical room placement, the 166 cabinet doesn't look too bad (although the data-sheet dimensions are inconsistent, so YMMV), the others vary. The 83 cabinet isn't up to much as far as I'm concerned, but it's spec. isn't ideal for BR loading in any case (the slow rise will help with step-loss, but the dip between 100Hz - 200Hz & peak at Fb aren't great); the 103 box isn't pretty either with a dip through the upper & midbass & a peak at Fb; 126 box fairly classic EBS, the 206 a slightly underdamped EBS. Again, no damping assumed to adjust expectations accordingly; ditto for room-gain & system etc.
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Last edited by Scottmoose; 29th September 2013 at 06:10 PM.
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Old 29th September 2013, 06:08 PM   #4
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FExx6En series with SET amp (2.5ohms output impedance assumed)

What you'd expect really. The 83 box is technically no better, but arguably no worse & the initial rise may help correct for step-loss. Still hate the dip with peak at Fb, though since the room dominates < 300Hz, YMMV. In small Japanese spaces with thin-wall construction leaking LF, that peak at tuning might be brought into line. The 103 box still has a peak at Fb, so avoid boundaries & lots of damping needed I suspect. 126 box taken on a nicely damped alignment so probably not bad near boundaries with some help where needed for step-loss. 166 cabinet now near-QB3, so keep away from boundaries or increase damping & probably useable with help for step-loss. 206 box now approaching classic EBS (still slightly under-damped) so a bit more flexible. The 126 & 206 will likely do better with a slightly higher output impedance amp. or resistive speaker wire. ~4ohms perhaps.

Again, YMMV given amps, rooms, room construction, taste etc. Like the FFxx5wk, linear dynamic range = limited given the short VCs, although they overload more benignly than some others of this type.

FWIW anyway.
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Old 29th September 2013, 08:35 PM   #5
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Quote:
Originally Posted by Scottmoose View Post
FFxx6En boxes
Those are all pretty ugly IMHO.

dave
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Old 29th September 2013, 09:11 PM   #6
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TBH, mine too. I was trying to be generous, but my doctor has just informed me the shock to the system will be serious if I keep it up, so I shall revert to my old self from now.

Yep. Some of them are 'run for the hills' in alignment terms. But then, they weren't designed for these drivers & neither the old 6E or the current En series are particularly well suited for BRs anyway without a heck of a lot of help from the amp, and that's just in FR terms.

Last edited by Scottmoose; 29th September 2013 at 09:16 PM.
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Old 29th September 2013, 09:23 PM   #7
sreten is offline sreten  United Kingdom
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Hi,

The only one that looks half decent to me is is the original green in #2.
No wonder vented gets such a bad name, it is easily misused.
Used well though its hard to argue with.

rgds, sreten.
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Old 29th September 2013, 09:29 PM   #8
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Quite.
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Old 30th September 2013, 04:35 AM   #9
IG81 is offline IG81  Canada
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I've always thought the FFXX5WK boxes looked like fair recommendations. The response humps on the smaller units might be there to make then sound livelier before what would still be a steep cutoff. They might also assume usage with no step filter perhaps? Still, I like the 125/165 alignments most "on paper". Maybe I ought to try cheap prototypes for 85 and 225 as I have both drivers around. I'd probably prefer tuning at Fs for the 225 though. Or maybe a classic Vb=Vas, Fb=Fs (permitted by Qt~0.35) could be fun, but I have no pressing need for a box this size.

IG
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Old 30th September 2013, 02:44 PM   #10
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Depends on what's called 'lively', but an anechoic peak at Fb is pretty much death from my POV in alignment terms sans any extenuating circumstances.) Possibly they're aiming for reduced need for shelving filters & possibly assuming thin-wall Japanese room construction or similar leaking LF energy, as mooted above.

Yep, the 225 box would work OK Fb = Fs. Slightly less damping of course, but decent. Off the top of my head, Vb = Vas, Fb = Fs should give something vaguely approximating a EBS alignment, albeit with less of a shelf. Personally I don't much like EBS style alignments except for v. low tuned subs ( < 16Hz or so assuming appropriate driver[s]), but YMMV as always of course.
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