Playing around with Fostex FF85K

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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.

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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! :D Very open sounding, although of course lean on bass. It sounded best as per below, open.

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

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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! :D

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

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.
 
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
 
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.
 
Finally an update!

First, let me comment on the boxiness, this has now disappeared completely. I believe this was due to very little bass due to the drivers being new, and insufficient damping of the boxes.

Let me first say that It sounds absolutely unbelievable now they've had a few weeks to wake up!

This is how it looks in front of me right now (unless you close your eyes, then you can clearly see Norwegian singer Kari Bremnes and her band…) :D

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They do look a lot better without the felt, but they gain quite a lot of clearness in the top when it is applied. Without it, they can be a bit too hot in the extreme treble. I'm trying to think of a good looking way to do this…
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In the middle of experiments with various port depths. Curiously, they sound more "open" with a port than without. I found the 12cm/ 70hz version to sound best.
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The NOS 8" on top of the speaker is intended to be tried as a small desktop sub. Very retro, lacks all thiel info, but without a box it sounds very promising and quite efficient. I'm planning a small sealed box and a small "chip amp" with built in cross over (maximum power is only 6w continuous, so this will be a small affair...)
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Current amp (waiting for focus to shift to the SE 6V6 amp I'm planning) is a Revox Modell 40. Very cool Swiss design from the '60s. It sounds surprisingly good, even in the main system!

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This is how I've added damping right now. There is a lot of polyester damping in there, but rolled in order not to bend the paper port…
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This is how they have sounded best so far. The porting actually made them sound more "open", so I clearly prefer this to the sealed version.


They sounds really good! These drivers are truly special, extremely spacious and open sounding (even though sometimes a little too high resolving for web based services, since overtones comes through with such ease. Compressied sources can truly sound awful…). The dynamics and correctness of timing is absolutely top notch, voices sound superb. I could go on…


However even though they are all right in the bottom, perfectly fine for acoustic music, I have a Velodyne SPL800r to be sold (I have a DD-10 in the main system now) and decided to give it a try, and with this great little sub added… WOW!!!

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The sound is crystal clear from deepest end to highest high and really engaging. These are truly little gems! Right now have cut them at about 120hz, and they can play seriously LOUD if required.

Now, next step is to see how the microFonken fares against Fostex' design. The plan is to add walnut veneer to the speakers that win! I also plan to test a miniature 10x10x10cm box as home theater surrounds.
 
Wonderfull amp that seems to be in a very good shape.

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I have one myself (that is very worn out - the previous owner used it as a bookshelf amp without ventilation).

The main amp amplifies just 15 dB! That might be a reason for the tight bass. It even sounds good on my Quad (but I myself need the extra power of an F5).
 
Update a few years later!

I found this old thread and figured it's time for an update!

I built the uFonken boxes for the drivers, and I added teak veneer to them (they were out of walnut...). They look really good, in a very cute way.

I ended up selling my very expensive and absolutely fantastic Marten Miles 3, because I moved to an apartment that made it impossible to get good sound and I lost the motivation to own them. The Velodyne DD10 that I have is actually so good that I let it take over from the awesome Marten speakers from 150hz down, especially in this very problematic room. So, I figured why have big speakers when I cut all the bass from them anyway? To make a long story short, the ufonkens with the FF85k are my main speakers since about 2 years, and I am very happy. :) I think I am lacking a little bit of mid bass, but with the excellent, tight and tuneful bass, and the really snappy, detailed and "stomp your foot" feel of these little gems, it sounds great.

The uFonkens are driven by a McIntosh MC7100 and a Nuforce AVP17 home theater pre amp that also provides D/A and crossover, currently crossing over to the sub at 200hz.

(Let's see if I can find a picture of how they look now...)
 
Ah, cool that they have been updated, I thought they had been discontinued. Now I can build the remaining five, I am using a 7.1 home theatre pre amp after all... Thanks by the way Planet 10, awesome pages you have that inspired me to take this on! Great work!

A few more pictures I dug up:

the build in progress:

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The veneer process was very simple, the veneer was cut to be somewhat larger than the surface to be covered, then regular wood glue was applied and the surface was ironed with a hot iron, and then put in press (using a pile of magazines) while it dried. Very quick, and worked very well! (of course the second speaker looks better then the first, heh)

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Electronics...

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Comparison with the Fostex box from the data sheet:

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There is a picture from a DIY-meet in Gothenburg too, but I can't seem to find it, and I'll take a pic of the current setup tomorrow.
 
Feel free to use the pics Dave, glad if I can help! Is there also a design that is lika a "real" Fonken? I think I saw pics on the forum, but can't see the plans on the planet10 site?

A few more thoughts. Someone might wonder about the felt used on the front on some earlier pictures, I felt it helped at first, but removed it after a while, I found that the sound was better without.
When the speakers were presented at the DIY-meet, unfortunately they did not come into their own put way into the room without bass support. They could work as detailed PC-spekears, but without a sub the magic is hidden behind the light-weight presentation. I really feel these are tweeters that go down into the mids, rather than mids that try to go up.

Also, links to the build threads on Swedish forum hififorum.nu, with a bit more details for those who read swedish or use Google translate. :)
HiFiForum.nu - Kan man bygga högtalare i lägenhet? (uppdaterat)
HiFiForum.nu - µFonken- smålådor med Fostex bredbandare
 
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