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Old 19th August 2013, 07:23 AM   #1
inrank is offline inrank  United Kingdom
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Default Fostex FF225K

After a long search, I have managed to source a pair of Fostex FF225K drivers but not sure what to put them in at the moment.

I have previously had a pair in some Jericho Cabinets in another room, which were OK, although I found they had excellent mid-bass/bass they were really too big, size wise on the footprint. (height I can deal with)

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image0045u by RSdesignUK, on Flickr

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Old Hifi by RSdesignUK, on Flickr

Amplifier for FF225K
FF165WK/FF225WK/FE166en

At the moment, I have some Veravox 5S drivers, in a rough aperiodic enclosure:

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System by RSdesignUK, on Flickr

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Veravox 5S Speakers by RSdesignUK, on Flickr

I want to try something that is a bit more efficient (~96dB Vs ~92dB) to make the most of my DIY Decware Zen, and that has greater dynamics, attack and bass capability than the Veravox drivers.

For a smaller footprint, I guess a BiB is the way forward?

Doing some searching (on here) I found the following references, although I cant seem to find the original excell spreadsheet for the BiB calculator.

Quote:
Just for you mate: a Godzilla shortened BIB for the FF225K. 136in line for a 68in tall box. W = 10in, D = 14.5in (including a 0.75in thick internal baffle). Zdriver 29.5in.
Quote:
Fostex FF225K
L = (Line length) 78"
Zdriver = Driver 35.75" down from sealed end of cabinet
Sm = 126"^2
Are there any other cabinets that would be suitable, all I can find is either BiB, Jericho or some 'BK201' references.

Cheers, Rob
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Old 19th August 2013, 09:55 PM   #2
xrk971 is offline xrk971  United States
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Try a Karlsonator with the FF225WK. A Speaker that Kicks Butt in Large Spaces

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Old 20th August 2013, 06:38 AM   #3
inrank is offline inrank  United Kingdom
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Is that not modeled for the FF225WK rather than the older FF225K which has quite different specs?
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Old 20th August 2013, 08:02 AM   #4
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You've been seeking out a pair of FF225Ks, but not thought what to do with them?

OK, humour aside. As a very basic rule of thumb, as far as box alignments go, the FF225k will work reasonably in most enclosures designed for the FE206E, since F0 & Q were similar. Technically it needs a larger box (higher Vas) -how much so depending on what it is you're up to. But it'll work.

Depending on how big you're willing to go, a BIB is one obvious choice. It'll go into some of my designs also. There was an MLTL project on the 'net a few years back, but I believe the site has gone -no big deal, MLTLs are easy enough to do, although if you want to get the best from them a proper design is preferred. And a bass reflex is also possible, although in all cases the alignment should be adjusted to reflect the output impedance of your amplifier (?).

One point about the 225 is its miniscule Xmax. That's not quite as much of a big deal as it sounds, since the old FF series overloaded fairly gracefully, but it's something that should be kept in mind & worked with.
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Old 20th August 2013, 08:22 AM   #5
inrank is offline inrank  United Kingdom
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Well, I really liked them in the Jericho's but they would be too big to be practical.

Was the MLTL the Boozehoundlabs one, IIRC?

I have got about halfway through that 'A speaker that kicks butt in large spaces' thread but still none the wiser about Karlson enclosures advantages apart from bass 'punch'.

I am favouring the BiB as having made one for the Veravox drivers, they are very simple, and I dont mind big in terms of height.

Last edited by inrank; 20th August 2013 at 08:36 AM.
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Old 20th August 2013, 10:02 AM   #6
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Probably, I can't remember offhand, although I do remember thinking it was pushing the driver it bit hard. Not bad though.

Karlsons are BP variations, as GM & others have pointed out for years. The order depends on the specific box. As you'd expect from a BP, they focus most of the output over a narrow BW, so are very efficient & usually offer tight control over the drive unit across this region, but it often (usually) comes at the price of resonant / phase problems as frequency increases. They have an enthusiastic following though, and sometimes these issues can be negated, or partially so, while others put up with downsides because they like what they do elsewhere. YMMV.
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Old 20th August 2013, 10:39 AM   #7
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by inrank View Post
Is that not modeled for the FF225WK rather than the older FF225K which has quite different specs?
This is for the WK version. As far as Karlson K15 style enclosures (band pass variety) they are not really suited as much as the Karlsonator which is a mass loaded (ML) TQWT with a Karlson coupler. The advantage of the Karlson coupler is wide spatial directivity with less lobing. From what I have heard, the FF225WK needs help on top with a super tweeter. You might want to take a look at the 'Pappas' TL' where Jim Shearer made a large rear firing TL that has the general shape inspired by an FH3.
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Old 20th August 2013, 11:33 AM   #8
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The Karlsonator is still a BP variation, just a different one. An ML TQWT (current parlance) with a Fulmer / Karlson slot would imply a back loaded pipe with the mass-loading vent created by said Fulmer / Karlson slot. The Karlsonator provides some loading to both sides of the driver, a la a (rather foreshortened) double tapped horn popularised by Tom Danley. The precise order depends on the design.

Last edited by Scottmoose; 20th August 2013 at 11:39 AM.
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Old 20th August 2013, 12:20 PM   #9
IG81 is offline IG81  Canada
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For my part, I can say that the smaller FF125K's ridiculous 0.15mm Xmax can be exceeded by a good deal and still sound decent, so FF225K will be that much better if only because of the much larger cone. Horn-loading and/or low-damping amps is where it's at. Cool you could find a pair, I would have liked to grab some. Lots of mixed opinions on the old FF series and very few examples of their use outside of Japanese websites, save for the FF85K maybe. I like the 125 FWIW. The new FF's seem to be doing better with popular opinion, but they are much simpler to design for as well, now we can get away with fairly simple BR.

Can't say which model off-hand, but FF225K may do well in some 8"/10/12" variations of Karlson enclosure. Footprint may be larger than what you want though.

Good luck and I'll be following.

IG

Last edited by IG81; 20th August 2013 at 12:25 PM.
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Old 20th August 2013, 02:30 PM   #10
Greg B is offline Greg B  United States
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Quote:
Originally Posted by inrank View Post
Is that not modeled for the FF225WK rather than the older FF225K which has quite different specs?
Actually, the Karlsonator 8 was designed before the FF225WK came out. I did my kludged sims using the FE206EN with the older FF225K. I don't think I saved one for the latter, but it looked about the same.

These were done in MJK's 'sections' to get a ballpark idea of the response. Unlike xrk971's newer sims, it doesn't include the partial bandpass loading of the front, or the effects of the diffraction slot. (I was still working on the name)

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Click the image to open in full size.

Download scale plans here:
Karlsonator 8

If you post the specs for the FF225K, xrk might be talked into modelling it for you. If you don't have them, I have them on a backup drive in a cardboard box somewhere. Might take some diggin.

I'd like to note that aside from the different folding, this enclosure is fundamentally similar to the "Pappa's TL" just posted by Jim Shearer. The differences are the BP loading, convergent exit, and Fulmer/Karlson slot.

Last edited by Greg B; 20th August 2013 at 02:38 PM. Reason: typo
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