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Old 25th September 2006, 10:48 PM   #1
Rafal is offline Rafal  Canada
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Default Exciting project for CSS FR125s

HI All,

It's fall here in Canada and as it gets colder I start to itch for a DIY hifi project. I have a pair of CSS FR125s drivers and have tried them in an open baffle last year but I fpund a base a bit lacking.
Can anyone suggest a tryuly excellent enclosure design for these? Maybe a horn of some type (I'm not intimidated by difficult woodworking ). Maybe a nice BR (I read about miniOnken byt I'm not crazy about the shape and looks?

I anxiously await your suggestions,

Or, should I just sell them and get different drivers?

I want something really cool to build that performs way above the price of the project.




They will be driven by gainclone.
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Old 25th September 2006, 11:39 PM   #2
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These drivers seem to work well in BR enclosures. Dropping the numbers into WinISD, you get an almost flat response down to 50Hz in a 15 litre box with a 2" dia. X 4.8" long port.
Let your imagination determine the shape of the box.

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Old 26th September 2006, 12:07 AM   #3
Rafal is offline Rafal  Canada
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Thanks Jeff,

Does it matter where I put the port?
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Old 26th September 2006, 12:10 AM   #4
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Want bass? You could try a BIB:

Zilla's BIB page

I built a set out of cheap pine boards to try out the concept. In my 14' x 11' x 8' room, they go low enough to excite the (untreated) room's 40 Hz resonance. Total response in room is UP several dB at 40 Hz, there's way too much bass! On some recordings it can be a very fun effect (e.g. in the Overture on Joni Mitchell's album Don Juan's Reckless Daughter, Jaco Pastorius makes his entrance with a huge, deep bass note that he lets ring on. Through the BIB's it's !). Then sanity sets in, and I realize that my room really needs some bass traps.

The bass is not just plentiful, it's tuneful and articulate, and the woofer is well controlled enough that they don't flap around or bottom out.

I'm not entirely pleased with the midrange. The predicted responses for BIB's are always a bit ragged, and these seem to have a dip that robs voices of some of their proper weight. Probably not helped at all by the much-too-lively pine cabinet. I need to play with better damping materials in the bottom of the line. I'm also in the process of adding a 'supra-baffle' to one of the cabinets to see if that helps. I'll post on that in the BIB thread when I have had time to listen.

I have also listened to the FR125's in open baffles. The sound in the BIB is dramatically different - the mids are more colored, but there is real bass there. Since you already have a pair, it might be worth a try.
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Old 26th September 2006, 12:43 AM   #5
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I would suggest that you build my bipolar MLTL speaker design that uses a FR125S and a WR125S in each box. The drivers are mounted back to back (the WR on the back side) and you'll get really good bass in a relatively small, easy to build MLTL floor standing speaker. You can find plans and a write-up at:

CSS FR125S/WR125S Bipolar MLTL Loudspeaker

You might find a recent thread on the Audioroundtable forum of interest. It was started by Fred Thompson who built my bipolar MLTL FR125S/WR125S design. The thread starts at:

GPAF Treasure

and another bipolar MLTL listening impression thread on Audioroundtable at:

Bipolar Speaker Listening ImpressionsA

If you have questions, you can contact me.


Click the image to open in full size.
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Old 26th September 2006, 09:45 AM   #6
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Jims design is a nice one, I'd go with that if I wanted floorstanders and a little more max. SPL.

But the FR125s' are also perfect for little monitor like speaker, because of their great bass extension. I just heared a version in 6.5 Litres Closed Box, with a highpass to tame the basspeak. It's amazing what comes out of these little boxes, good & deep bass, nice mids and very smooth hights - bass is not as deep as in my double sized bass reflex version, but enought!

Here's a link to a german forum, where you find plans, filters and a messured FR - Cyburgs-Monitor

Great little drivers, I wouldn't sell them!

best, LC
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Old 26th September 2006, 01:35 PM   #7
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I have found that with a BR enclosure the FR125S does not give the bass performance I would expect because of air leakage past the phase plug.
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Old 27th September 2006, 12:09 PM   #8
badman is offline badman  United States
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A little sealed box of 9-15 litres will perform well with these, and makes it easy to roll a sub in without adding a crossover to the fullrangers.
"The dawn of Bose created the "Man Cave" and reduced testoterone levels worldwide by 18.5 per cent" Peteleoni
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Old 27th September 2006, 06:39 PM   #9
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Unlike every other driver i have played with, if you model for max bass, you will end up with too much bass. Lovechild's suggestion is interesting, small sealed will help limit the LF excursion, the cap will roll it off even earlier and adjust for too a high a Q. The cost of a decent passive cap could run almost as much as the drivers thou. This would be best implemented as a PLLXO in your amp.

My favorite box for the 125 is still the miniOnken. If the cosmetics don't grab you, the same tuning can be executed in other ways (i'm happy to help reshape them). The nature of the ports makes them close to aperiodic, so you can't just bang a round port into them.

10-13 litres sealed is good for an unassisted design (still wouldn't hurt to add a cap in the amp).

None of the ML-TLs i've heard for these -- including my own -- were completely satisfactory. I'd like to hear them in the GM bipole sometime -- just take the Griffin bipole and double the xSection (or just put one driver in Jim's box).

The 1 horn designed for the FR125s -- the PAWO -- never worked well with the CSS drivers (and is not really a horn, but daline-like with an expanding TL section). There is a suggested fix to make the FR125 work in the PAWO, but i don't know of anyone who has tried it.

The FR125 will never get you the mids of a Fostex, but it has its own strengths.

community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
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Old 27th September 2006, 06:52 PM   #10
badman is offline badman  United States
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The FR125 will never get you the mids of a Fostex, but it has its own strengths.


Seriously though, benefits of an underhung motor shine through in midrange. The XBL^2 motor is better when working hard, but within the 'happy' place, an underhung motor will slap an overhung motor around in terms of performance every time (all else being equal). Now, the FR125 does have a lovely motor design for an overhung, being excursion linear and having a shorting ring, but still at MOST volumes you use such drivers at (and before IMD becomes bothersome, which is the biggest excursion limiter in a small fullranger, IMO, NOT the motor) the underhung has a pretty good advantage.

All that said- the FR125 is a great driver and is the topic of my most current (running parallel with a pair of nifty stands) speaker project- little sealed sphere enclosures (at this size, the backwave can be effectively damped by the stuffing due to the high frequency)
"The dawn of Bose created the "Man Cave" and reduced testoterone levels worldwide by 18.5 per cent" Peteleoni
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