Fostex FF125WK BR box build

[kinku]

Hi all,
After brief discussion and getting tips, I went ahead and build a FF125WK BR enclosure using datasheet measurements for enclosure provided by Fostex in Datasheet/Manual.
I was looking for a better midrange reproduction for vocals ,violin and male voices.I have to say I have not been disappointed with first few hours of listening.
As expected it has slight harshness at around 7KHz region but can avoid by keeping speakers off axis. Bass response is not bad for the tiny enclosure but may need help with BSC filter.
Very mellow to listen to vocals,not good for plays with lot of instruments playing and not for heavy rock.
I am wondering what should be the baffle step correction to use?
Please see the SPL response 1/1 octave smoothed for easy interpretation.

[ultrakaz]

Honestly, I haven't had much luck using any type of Bsc filters before, but you can try an inductor (around 1mH) and resistor in parallel (around 8 ohms) to flatten the treble response. Or for a more notch type filter to cut around that 7kHz region add a cap (around 4 mF) in parallel, so Lcr type filter. Perhaps, worth a try if you have the parts lying around.

However, I prefer to let the driver run unimpeded by any crossover components in the electrical path. Instead I would run a woofer at 700Hz as recommended in the Fostex lit that comes with the driver. Quite clever I may add for Fostex to sell more drivers, but with the smoothish response of the 165wk or 225wk plus the single inductor albeit largish, it should sound pretty good. Also, I do like how they leave the "main" driver unmitigated/pure. Overall a pretty good compromise for "singlish*" driver type speaker.

[kinku]

where did you find that 700Hz in literature?I totally missed it.
I am against any inductors or resistors too,but may be it needs it.
I would rather go with a Sub.

[natural sound]

Hello there . I have had 2 ta 3 pairs of this driver. I would say look at the paper work that came with the drivers. It's all in Japan but, there is a 3 way speaker in there for cabinet plans. They use a Fostex FT17H Horn Tweeter using a cap and a inductor. A 0.47 uf cap and a 0.18 mh inductor. FF 125WK Drivers running fullrange not cap or anything. Then for the bottom end the FF 225WK Drivers crossed over using one inductor at 3.8 Mh. I hope this helps. Also this driver has a better snap with drums and a higher range then my Fav. Fe 126en drivers. Enjoy N.S.

[ultrakaz]

Originally Posted by kinku

where did you find that 700Hz in literature?I totally missed it.
I am against any inductors or resistors too,but may be it needs it.
I would rather go with a Sub.

Yes, it is in Japanese. But, you can see 700Hz in the text, see the frequency traces (unfortunately no transfer function plots) and see the solitary 3.5mH inductor in series.

A "Sub" is not going to help that 7kHz rise/spike and the elevated mid/treble range. More likely to cause a dip in the lower mids.

[ultrakaz]

Originally Posted by natural sound

Hello there . I have had 2 ta 3 pairs of this driver. I would say look at the paper work that came with the drivers. It's all in Japan but, there is a 3 way speaker in there for cabinet plans. They use a Fostex FT17H Horn Tweeter using a cap and a inductor. A 0.47 uf cap and a 0.18 mh inductor. FF 125WK Drivers running fullrange not cap or anything. Then for the bottom end the FF 225WK Drivers crossed over using one inductor at 3.8 Mh. I hope this helps. Also this driver has a better snap with drums and a higher range then my Fav. Fe 126en drivers. Enjoy N.S.

Hello N.S., I'm curious to know if you have tried this? And if so, did you build the enclosure as described in the instructions?

[IG81]

Speaker-level BSC: Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

Line-level BSC: Baffle Step Compensation

IG

[xrk971]

IG,
Thanks for the link to the very simple line-level BSC circuit. I have all those small signal level parts already - saves me from buying a pair of pretty hefty speaker level inductor coils and high power resistors (which would end up costing more than the drivers) - not to mention fact that amp power is being wasted on heating the resistor at higher frequencies.

[chrisb]

a few observations:

I've built more than a couple of Fostex "recommended" enclosure designs over the years, and with the exception of the larger BLH for 6" & 8" FE series, most have been remarkable in their shortcomings in LF extension - which will certainly exacerbate the need for BSC in this size range.

Certainly there's no argument that as many things as a 3-4" FR driver can do very well, there are few that couldn't benefit from HP filtering and bass augmentation (call it FAST, or just 2 way with low XO - whatever you like)

Fostex FR drivers are beloved / notorious for long break-in periods ( as much as SEVERAL hundred hours) before they fully "open up / smooth out", but even then, for many folks the 4" size particularly retain some issues of narrow band peakiness / harshness in the upper midrange that are not well addressd by wide band BSC or EQ. While there are some physical cone treatment regimes that can mitigate those issues, in many cases narrow band digital EQ is the most expeditious method of correction.

BSC "balances" FR response works by attenuating above selected frequency, and certainly can't improve the driver's basic excursion limitations - regardless of whether at line level or passive, you'll lose overall SPL capablity

If kinku's application precludes larger enclosure volumes than the 9 liters of the "factory" BR design, there may be little option but careful EQ (i.e. more than just the BSC) with the resultant reduction of maximum SPL / excursion capabilities, which in very near-field situations is not necessarily a deal breaker.

If on the other hand there's space available to accommodate larger monitor size or even floorstanding enclosures, there are many designs that could substantially extend this driver's LF performance:


Floorstanders:
- MLTL similar to the Pensil for A7.3
- Woden Venom
- BLH such as the FH3 or Steve Deckert's interesting little DNA design that's currently getting some attention on another forum thread ( I'd suggest buying the plans and building with plywood, not foam-core, but that's just me)

"desk-top" / stand mounted monitors;
- any of several variants from

http://p10hifi.net/FAL/downloads/CGR...ree-090612.pdf

I've heard the FF125Wk in a couple of the above designs, and they are certainly capable of delivering well below 60Hz

[planet10]

Originally Posted by IG81

Line-level BSC:

Paul Joppa (of Bottlehead fame) article on PLL BSC

dave