Fostex FE126E Recommended Enclosure

[CastleJohn]

I am new to full range drivers and I think the Fostex recommended enclosure for the FE126E looks a reasonable place to start. The outlay for the drivers is modest, and the rest is just woodwork. The size will sit nicely on my stands. This enclosure is a hybrid BR/BLH design, supposedly giving a more gradually extended bass. I shall use the newer FE126En driver which some say overcomes the shoutiness of its predecessor.

Question: has anyone out there actually built this design? Have you got any advice or tips on construction that you could give me?

I wonder whether I should use chipboard, MDF or birch ply for the woodwork. Is it best to just glue everything together, or use screws? Is any treatment required for the wood surfaces on the inside? Should the insides be sanded, painted, or left rough? Are any damping materials required? If I use grille cloth (to appease the good lady) can it go over the horn entrance? Are there any other important considerations I should be making?

Any help in this construction project would be greatly appreciated.

[planet10]

I hate to burst your bubble, but that Fostex recommended box (really a BR/TL hybrid) is not amoungst their best (and their best tend to me mediocre). 1st thing you start thinking about when you start listening to them is how to make the bass better. It doesn't go very low, and is mushy & fat. And if you are going to standmount them, then you'd be way further ahead just starting with a small sealed box & know that you need helper woofers. We ended up burning ours (a waste of nice BB plywood).

The FE126 really wants a horn, and they are best built with good ply. The best boxes for FE126 are Valiant, Frugel-Horn Mk3, Saburo, and RonHorn A126 if you don't want to delve into woofer support.

What amplifier are you planning on using? (amplification can be a big deciding factor on the most suitable speaker)

dave

[CastleJohn]

Thank you, planet10. I haven't got the wood yet, so it's not too late to change tack as far as the cabinets are concerned. But I have ordered the FE126Ens.

For amplification I currently use John Linsley Hood's class-A transistor design which provides 5W of surprisingly beefy, articulate and well-controlled sound into a pair of Audio Note Type Ks. These closed box speakers are a bit shy on the bass, and I would like something that goes a bit deeper, without being bass-heavy. My listening tastes are entirely accoustic - vocal, instrumental, choral and orchestral, and my prime concern is naturalness, detail and transparency, especially in vocals. Room size is modest - about 7m x 4m - speakers directed lengthways. The need for stands arises simply from the fact that there is a sofa between my listening position and the speakers. I should probably rearrange the room.

I wasn't sure from your reply whether it was just the last of your suggestions, or all four of them, that would be OK without woofers. I do not want woofers - surely the whole point is that you can do it with a single driver with a bit of care. I look forward to your further advice.

[planet10]

John,

The amp should be good as long as the damping factor isn't too high. The power is certainly right.

It is unlikely that even in the largest enclosure the FE126 will go lower than the ANs, but naturalness, detail and transparency it should also be all over the ANs. Imaging & efficiency too.

Most effortless and deepest bass is likely Valiant in corners, but Valiant on a wall, or RonHorn A126 in the corner, likely get close. The other 2 aren't far behind.

Unless you mount the speakers upside down from the ceiling you will need to rearrange the room, there are no decent boxes for the 126 that aren't floorstanders (and that assume the floor as part of the horn load). A126 may have the driver mounted high enuff to fire over the sofa, but anything between you and the speakers should be avoided.

Valiant can be found at the Woden site, the other 3 on the Frugal-horn site.

dave

[CastleJohn]

I'll check up on the damping factor.

Of the designs you mention, which would you recommend as a good compromise for being easy to build (no wood bending please) and good bass extension? I'm quite happy to have something 6ft tall.

[planet10]

None of them have wood bending. the A126 is the hardest to build, Valiant & Saburo have lots of bits but almost all 90 degree cuts, FH3 is simple but has some tricky bits.

dave

[CastleJohn]

Saburo looks like the one for me - I'll probably wall-mount it. Just got to find someone who will deliver me three sheets of 19mm plywood. Actually I'm having difficulty finding this in the UK. The nearest standard size is 18mm, which I guess I could use with a bit of care. Veneered MDF is available in 19mm but you say ply is best.

Just out of interest, what's the best way of routing (and securing) the cables from the driver to the terminal posts on the back?

[planet10]

18mm is fine. Scott's plans always start out imperial, despite having grown up metric.

To adjust the channels are kept the same width and (if you want to be anal) the depth is increased 1mm. You end up with a slightly shorter box.

dave

[chrisb]

Originally Posted by CastleJohn

Saburo looks like the one for me - I'll probably wall-mount it. Just got to find someone who will deliver me three sheets of 19mm plywood. Actually I'm having difficulty finding this in the UK. The nearest standard size is 18mm, which I guess I could use with a bit of care. Veneered MDF is available in 19mm but you say ply is best.

Just out of interest, what's the best way of routing (and securing) the cables from the driver to the terminal posts on the back?

After playing around with hiding input connector in the base plates of floorstanders and horns, which can make things tidy but a royal pain in the butt if you swap out a lot of different speakers in the same system, Ive reverted to keeping the internal wiring as short as possible, and mounting the terminals accordingly.

In the case of Saburo that would mean input terminals at the center of rear panel, with wiring a straight line through the deflector prism that forms the bifurcation. I'd use plywood rather than solid to form this triangle as it allows for easier mounting of your favorite terminals and dressing of wire - drill a small hole in the deflector and seal that as well as adhere the wire to the side panel with silicone.

[fandersen]

Originally Posted by CastleJohn

Saburo looks like the one for me - I'll probably wall-mount it.

Faced with similar requirements albeit a smaller room I also opted for Saburos. I don't have the room to move the speakers away from the wall but the bass is still quite good.

Originally Posted by CastleJohn

For amplification I currently use John Linsley Hood's class-A transistor design which provides 5W of surprisingly beefy, articulate and well-controlled sound into a pair of Audio Note Type Ks.

I'm using a Tubelab SimpleSE. I started out with EL34 tubes in triode which sounded nice. I changed to KT88s in ultralinear mode which to me was a significant improvement, more dynamic, tighter and deeper bass. I don't know if it's just the KT88s or the increased output in ultralinear -- estimated at 10-15W.

Originally Posted by planet10

18mm is fine. Scott's plans always start out imperial, despite having grown up metric.

To adjust the channels are kept the same width and (if you want to be anal) the depth is increased 1mm. You end up with a slightly shorter box.

If I remember correctly, this adds up to about half an inch shorter in overall length. The layout measurements on the plans would lead you to start assembling all the pieces starting from the ends. I suggest starting in the middle and working out. This ensures the channels are the correct size.

Originally Posted by chrisb

In the case of Saburo that would mean input terminals at the center of rear panel, with wiring a straight line through the deflector prism that forms the bifurcation. I'd use plywood rather than solid to form this triangle as it allows for easier mounting of your favorite terminals and dressing of wire - drill a small hole in the deflector and seal that as well as adhere the wire to the side panel with silicone.

I agree with Chris that the deflector prism should be made using plywood. The plans don't show the size of the deflector but the space between the deflector and piece A should be about 1.25 to 1.5 inches.

Since I wanted to put my speakers against the wall I used terminal cups. I installed them in the next channel down between pieces E and C. I ran the wire through piece D at the bottom of the speaker chamber, and then siliconed to the side to the back.

This is not a quick speaker to build, but it's not complicated. If you can, cut the width of all the internal pieces and baffles at the same time to ensure you will not end up with gaps between the sides. Take your time to build. You will be rewarded