Playing around with Fostex FF85K

[Leffler]

First of all, thanks for putting all the info up on this forum! I read about quite a bit when selecting drivers for this project, I think a lot of people do as I did without actually posting anything, so thanks!

I ended up with a pair of Fostex FF85K, just for the fun of taking on a project.



The goals are:
-To try a full range speaker and see what all the fuss is about.
-No passive cross over to mess things up.
-to use the full range/ no crossover idea as a basis for trying various constructions in a simple way.

The first box was the shipping carton from FedEx. Not too bad, actually! Very open sounding, although of course lean on bass. It sounded best as per below, open.



Second box is the original Fostex bass reflex, executed in 16mm MDF (to be veneered).



I am completing it in steps, however. First out without rear, and then closed. They both have their advantages, the open box sound more open, closed has better bass control. They both sound a bit "boxy" however (sounding just like you expect a small box), even though I have some felt damping in there. It helped tremendously adding my sub (velodyne DD-10) to the setup. Obviously small speakers sound small due to the lack of bass. The mid bass is still lacking however. (The sub is crossed over as low as possible, my regular speakers are -3db at 28hz, so the sub is setup to play basically 25hz and below). Crossed over at 80hz, the worst butterfly fluttering is avoided, and quite sufficient volumes are achieved.

By the way, I live in an apartment, so this also goes to prove that there are no excuses!







Next step is bass reflex. Fostex suggests two different lenghts, perfect for this kind of try-and-see project.

Before cutting the port however, I wanted to ask you how much difference it makes to put the port in the front or rear - what is the default from Fostex, they don't actually state which side the port is on? For esthetic reasons, I would prefer to put the port in the rear.

Coming installments in this epic tale of tinyness are:
-Building a pair of microFonkens (of course!)
-Restoring my vintage 2x10w tube Revox amp
-building a SE 6V6 amp from parts lying around
-building an active cross over, and an 8" "sub", preferably small and sealed, suitable for bedroom/ computer use. I have a few vintage 8" drivers in the attic.

So how does it sound so far?
Well, the drivers have less then 10 hours on them, and they sound very detailed, very full overtones, distorted guitars and trumpet spit are really coming out of theses boxes! However, they are also a bit too harsh in the top, I hope that will improve. The current boxes are also lacking in bass, not that it is not there at all, but the end result with the prominent high end is decidedly lean.

[Jim Shearer]

If you want to try a vented enclosure that's really quick and easy (and perhaps better than a cardboard box), check out the Sprites I built for the FF85k:
The FF85K Sprite

I still can't believe how good they sounded for the cost and effort.

Cheers, Jim

[2litre]

Leffler,

Please continue with your plan of action as it's nice and logical.
I for one will look forward to reading your impression at each stage.

So far it seems that you've tried the FedEx container and a sealed version of the Fostex recommended enclosure, correct?

R/
Jim

[loninappleton]

Bigger Is Better - BIB, Outdoor Speakers | Rock Speakers | Garden Speakers | Patio Speakers | In-Wall Speakers | Ceiling Speakers and more!

The link shown is a calculator to make the Bigger Is Better design from Terry Cain. I have used the calculator for Fe127e. At least sample the measurements for a cabinet it gives.

once you download the file, it loads into Excel or Open Office spread sheet equally well.

The design will be tall and thin and placing near wall corner will improve dynamics. The reason for this is that the back horn of the BIB is meant to expand using the corner of the wall.

Plus the build is easy and instructions are shown for it.

[planet10]

A BIB would be best inverted & straight. Might also want to consider the alternate Zd position.

dave

[Ty_Bower]

Originally Posted by Leffler

They both sound a bit "boxy" however (sounding just like you expect a small box), even though I have some felt damping in there.

I built some small enclosures for a set of Fostex FE-87E. I thought they sounded pretty boxy at first, but after more than a few weeks they seemed to really open up. Maybe your FF85K will improve with age.

[planet10]

My uFonken don't sound boxy... they do have FF85KeN, one of the things that seems to get lost with treatment is the ability to localize the driver.

dave

[fishski13]

in no way are the 2 pairs of uFonkens i've built sound boxy. i'm still amazed by the soundfield these cute little boxes can throw. they make my much larger ATC SCM12 monitors sound shut-in.

i have 4 more FF85K drivers in transit to chez fishski.

[Scottmoose]

That's three. The uFonken is one of the most remarkable little micro-monitors I've ever heard.

[mikey_audiogeek]

Originally Posted by planet10

My uFonken don't sound boxy... they do have FF85KeN, one of the things that seems to get lost with treatment is the ability to localize the driver.

dave

Track and trace helps <grin>