Fostex FE207E - bad sound

[Kashmire]

Two years ago, I bought a pair of Fostex FE207E drivers for testing.

My first enclosure was a rear-loaded horn (pictured) per Fostex design instructions. I also built a vented cabinet for listening.

Both enclosures sounded awful. The sound was dry, lifeless, and with absolutely no soundstage.

I have tried a variety of amplifiers: the Pass Zen v4, a hybrid Akikdo/MOSFET amplifier, tubed amplifiers (i.e. monoblock EL84), commercial amplifiers, and even the S-5 K-8LS.

None of these configurations have sounded good.

Any suggestions?

[planet10]

That looks like a BK-20 horn (not a Fostex Factory Design). Even when built as intended from plywood, and using the appropriate driver (one of the 3 8" fostex suitable for horn loading), it is not stellar. And stuffed as shown, it is likely a badly tuned aperiodic box.

I would also be leary of the Fostex recommended BR.

Add in the material you built these out of, and i'm not surprised with your take.

The 207 is not without its problems, but i would not call it awful -- even in a stock state. How many hours on them?

If you don't want to try for 3rd times a charm and put them in a proven box, it shouldn't be hard to sell them. The boxes should go into the tip thou.(sorry if that sounds a little hard)

Have a read thru the Curvy Chang thread.

dave

BTW: i really like what you've done with your EL84 monoblocks (i'd be using ECC81 on the front end thou)

[rjbond3rd]

Hi Kashmire, that cab looks like a Fostex BK-201 variant which is more oriented to the BLH-friendly drivers like the FE206E. I'm not sure that combo can be saved.

I see on your site that you also did BR and sealed, and were not happy. (Sealed will not go very low, obviously).

1. Did you use a baffle step circuit on the BR? If so, did you use a bypass cap (FE207E rolls off above 14k).

2. What kind of music are you listening to? Certain genres are better than others.

I have heard this driver sound excellent in the two FE207E designs on this page: Products

EDIT: Oh planet10, you are too fast!

[d to the g]

Originally Posted by planet10

it shouldn't be hard to sell them. The boxes should go into the tip thou.(sorry if that sounds a little hard)

it sure wouldn't. I know at least one person who has posted a wanted ad for these a couple of times!

[steviedon]

I wouldn't give up on the driver quite yet. I have both a set of curvy changs, and a set of brines FB20 cabs that I built myself, both using the FE207. Both sound extremely good. The changs have phase plugged drivers (which I strongly suggest having heard the driver side by side with and without) and obviously throw a bigger soundstage. The brines cabs are also excellent in their own right, but really need a sub under them. I agree with dave in observing that your first problem is your cabinet material. It just does not add up........good drivers, good amps, and $5 a sheet cabinet material will always equal poor results. On a side note, if you're looking for a driver to put in a horn the FE206 is a much better choice, so maybe selling the 207's is best. I might be willing to grab from you them as backups, for the right price of course.

[Kashmire]

Hmmm ... surprising comments about the enclosure materials. It is a mixture of 3/4" resin particle board and MDF (the baffle, rear panel, and internal baffles are MDF). I wouldn't except the cabinet material in this case to be playing such a prominent role. In my opinion, there seems to be other obstacles to overcome before optimizing the cabinet materials.

I lost the build sheet for the horn cabinet a couple years ago. It was in metric, and it was a headache to translate all of the measurement to my english table saw. The prints were branded Fostex. The BK-201 looks awfully familiar. Maybe what I have is a simplified BK-201.

If that's the case, the FE207E isn't the best choice for horn loading.

However, I just haven't had much success with sealed or vented. I roughed up some boxes using particle board, MDF, and PVC pipe (for the vent) for testing.

It just does not add up........good drivers, good amps, and $5 a sheet cabinet material will always equal poor results.

I usually rough up a couple boxes using particle board and MDF for initial listening - stuff built from these materials should at least indicate promising performance. Many of my particle board creations have sounded excellent.

And stuffed as shown ...

Yea, I tried it stuffed and unstuffed.

Did you use a baffle step circuit on the BR? If so, did you use a bypass cap (FE207E rolls off above 14k).

Nope. Don't know about this. I'll have to do some reading. However, I need a paradigm shift to improve the situation, not an incremental improvement.

How many hours on them?

Lots. When I bought them, I put them in sealed boxes in the basement and let them pink noise for a week. Then I (attempted to) listen to them seriously for a while. Since then, they've been my amplifier test speakers because their high sensitivity and no crossover lets me judge power supply noise rejection, hiss, and hum, along with some other key behaviors.

What kind of music are you listening to? Certain genres are better than others.

Totally understand. I build Pass Zen and single-ended valve amplifiers. These things are picky to music genres. I was trying lots of simple but textured vocals, male and female, and some folky stuff, like Mark Knopfler or Alison Krauss.

BTW: i really like what you've done with your EL84 monoblocks (i'd be using ECC81 on the front end thou)

Thanks! The first build of the amp used a 12AT7 (ECC81), but I needed just a bit more gain. I wired the LL1540 primaries in parallel to create a 1:2 ratio (thereby using the input transformer to get gain), but I decided the LL1540 sounds better with the primaries in series. So to get the desired gain, I switched to a 12AX7.

I moved the amp to my main system. The preamp delivers a bit more voltage, so now I don't need as much gain. I'll be switching back to the 12AT7 soon. All it takes is a few resistor changes at the plate and cathode.

I like the 12AT7 more anyway, because I can run more aggressive and hotter plate currents than the anemic 12AX7 1.2mA.

The brines cabs are also excellent in their own right, but really need a sub under them.

Yes, I have a dipole woofer system at the ready, along with the necessary electronics to integrate them with the target loudspeaker. These are derived from the Linkwitz Phoenix system using Lambda drivers. I have no problems integrating them with the FE207E.

Thanks for your comments thus far. I'm coming to the opinion that the FE207E is not my friend, and maybe a different choice would have been more appropriate.

What about dipole operation? Since I'm already using dipole woofers, is the FE207E a complementary candidate?

[planet10]

Originally Posted by Kashmire

What about dipole operation? Since I'm already using dipole woofers, is the FE207E a complementary candidate?

If you can XO actively, and the woofers can get up high enuff.

dave

[Samppo]

Looks like a thick front baffle you have there. Did you round over the driver holes from behind?

[rjbond3rd]

Hi Kashmire, if you put the FE207E into a BR (or MLTL) with no circuit, it's not going to be balanced (i.e. it will be too forward, lacking bass unless the cabs are flush against the wall). The circuit compensates for the tendency of lower frequencies to "sneak around" the baffle, radiating in an omni pattern (thus dipping ~3-6 db depending on distance from the wall compared to the mids and highs which radiate all their energy forward due to the width of the baffle). Search for BSC or "baffle step compensation".

The FE207E will not have much bass in an undersized BR but in the right sized BR or MLTL, it can play down to and below its Fs of ~40Hz. But that circuit is key. Circuit is just a resistor and coil in parallel, optionally with a cap, which is placed in series with the + on the driver. It basically cuts above a certain frequency, but the cap eliminates the cut at very high frequencies (putting the sparkle back in).

It could be that you are missing the frequencies above 14k with this driver. The BSC gives you the opportunity to handle that as well -- cutting the midrange and then using the bypass cap of whatever value lets you effectively "boost" the treble in relation to the midrange. Still, a supertweeter is a better solution if you need to play up to 20k.

Don't let this one driver sour you on single-driver though! I'm playing with the Mark Audio CHR-70's and they are as different as can be, and only $70 a pair. Not as efficient but lots of fun.

[Puffin]

I thought that the 207E was just a shielded version of the 206E. The 208 Sigma cabinet is a good match. I made mine 3 years ago and will never need to build another speaker.