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?
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?
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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)
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)
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!
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!
it sure wouldn't. I know at least one person who has posted a wanted ad for these a couple of times!
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.
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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.
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.
Yea, I tried it stuffed and unstuffed.
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.
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.
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.
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.
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?
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.
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.
Yea, I tried it stuffed and unstuffed.
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.
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.
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.
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.
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?
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.
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.
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.
Hi Puffin, the FE206E and FE207E are like night and day. The FE207E has two smallish magnets in a bucking configuration sealed inside a black steel cap. Qts is higher than the FE206E so it goes into resonant cabs more easily, but rolls off at ~14k.
The FE206E has one huge magnet, a lower Q, more HF extension and is happier in a BLH than in resonant cabs. About the only thing they have in common is the same Fs 🙂
I've wanted to try the FE208E-sigma cab with the FE206E for some time. Glad to hear you are happy with it!
The FE206E has one huge magnet, a lower Q, more HF extension and is happier in a BLH than in resonant cabs. About the only thing they have in common is the same Fs 🙂
I've wanted to try the FE208E-sigma cab with the FE206E for some time. Glad to hear you are happy with it!
I am more than happy. I will never need another speaker!
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No it is not. It has to be considered as a completely different driver. It only shares a cone & a basket with FE206. The motor and (possibly the) spider are completely different.
dave
Sounds like an FE206 should have been my choice over the FE207E.
So what's the reason anyone would buy a 207 before a 206?
So what's the reason anyone would buy a 207 before a 206?
Ugh! If a 207 is "smoother" than a 206, then the 206 belongs in the trash bin, alongside rusty metal, sandpaper, broken glass, and other abrasive items.
Referring to the FE207E as a comparatively "smoother" driver pretty much did that.
However, in interest of maintaining an adventuresome spirit, I'm going the give the 207 another chance by implementing the step filter. If that doesn't help, I'll toss the horn/vented/sealed enclosures altogether and try it open-baffle with my dipole woofers.
Uh, what's a BR?
This sounds like a capacitor in parallel with the driver to shunt high frequency to get low-frequency emphasis. This would be a LP filter, not a step function. It also sounds like something you'd use with open-baffle (dipole) operation.
For horn, sealed, and vented, what are the recommendations?
Hi Kashmire, BR == "bass reflex".
You have to deal with baffle step in some fashion. There are lots of clever ways aside from a circuit:
1. At the design stage, deliberately (!) put a "hump" in the low frequency to coincide with baffle step.
2. Put a passive circuit between pre and power amp.
3. Digital EQ
4. Use really wide baffles.
5. Use a driver that has a hump in the response around baffle step (one manufacturer recently designed this into a driver)
6. Circuit of course. The bypass cap is optional and based on your taste. It just defeats the amount of cut provided by the coil and resistor.
Any of these would work for sealed and vented (any design, really) to some degree. The circuit is the classic choice if the box is already built. Without some kind of baffle step strategy, your speaker's bass will be 3-6 db down unless flush against a boundary or two (or three).
A horn like a BiB can have so much bass that you have the opposite problem -- you have to get rid of some bass. But even then, the width of the baffle will not always perfectly match up to the gain of the upward-firing horn, so you have to fudge a little by mounting the driver in a frisbee-sized disk (supra baffle) to dial in the exact width and thus control exactly where baffle step is kicking in.
You have to deal with baffle step in some fashion. There are lots of clever ways aside from a circuit:
1. At the design stage, deliberately (!) put a "hump" in the low frequency to coincide with baffle step.
2. Put a passive circuit between pre and power amp.
3. Digital EQ
4. Use really wide baffles.
5. Use a driver that has a hump in the response around baffle step (one manufacturer recently designed this into a driver)
6. Circuit of course. The bypass cap is optional and based on your taste. It just defeats the amount of cut provided by the coil and resistor.
Any of these would work for sealed and vented (any design, really) to some degree. The circuit is the classic choice if the box is already built. Without some kind of baffle step strategy, your speaker's bass will be 3-6 db down unless flush against a boundary or two (or three).
A horn like a BiB can have so much bass that you have the opposite problem -- you have to get rid of some bass. But even then, the width of the baffle will not always perfectly match up to the gain of the upward-firing horn, so you have to fudge a little by mounting the driver in a frisbee-sized disk (supra baffle) to dial in the exact width and thus control exactly where baffle step is kicking in.
BR = Bass Reflex
To make it a step (and to avoid getting 0 ohms at high frequencies & therefore encorouraging the smoke to escape from your amp), you need to add a resistor in series (you get what is commononly called a Zobel if tuned to cancel the rising inpedance due to inductance,
Usually BSC is executed with a (parallel coil & resistor) in series with the driver. This raises the impedance at low frequencies, instead of reducing impedance at high frequencies as the (series cap-R) in shunt.
dave
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