Could be worse. Could be a pair of Visaton FRS8Ms. The only driver in the world that sounds better before its run in. 
😉
😉
At 400Hz you can get a pretty good 2nd order filter with just a series cap, but you'd need to compensate for the impedance spike at Fs. A better solution to the added parts would be a series network. You'd need to do 2nd order on the woofer and 1st on the tweeter (electrical) to get a target 2nd order overall slope. Don't forget the phase reversal of one driver to avoid a cancellation notch.
It'll take a little fiddling to optimize but you're going to be looking at something like 1.3mH across the tweeter, 60 uF across the woofer, and 1mH in series with the woofer (consider the 1mH as part of the woofer, so the 60uF would shunt the woofer-inductor combo).
These are approximate values of course, but will work fairly well with most 8 ohm (nominal) woofers.
Be sure to keep the DCR down on all parts, so if possible, big aircore inductors (14awg or even 12) and large physical-size caps (solens would be fine but no electrolytics). You can do cored inductors to avoid the pricey large-awg aircores, but why introduce magnetics artifacts if you can avoid it?
It'll take a little fiddling to optimize but you're going to be looking at something like 1.3mH across the tweeter, 60 uF across the woofer, and 1mH in series with the woofer (consider the 1mH as part of the woofer, so the 60uF would shunt the woofer-inductor combo).
These are approximate values of course, but will work fairly well with most 8 ohm (nominal) woofers.
Be sure to keep the DCR down on all parts, so if possible, big aircore inductors (14awg or even 12) and large physical-size caps (solens would be fine but no electrolytics). You can do cored inductors to avoid the pricey large-awg aircores, but why introduce magnetics artifacts if you can avoid it?
just built a nice crossover kinda like that for a fe138...
only 6db on mid, 18db on ribbon tweeter,
with a notch filter for the 138.
sounds nice.
with 12 ga foil in the crossover, 14 in the filter, & obbligato caps, the crossover components ran over $500...
yeah, good crossover components cost as much/more than drivers, but i don't think i'd want to get in that deep w/ a FF85k...
didn't know solen made non-electrolytics?
the obbligatos are smoother, more transparent than solen fast caps.
only 6db on mid, 18db on ribbon tweeter,
with a notch filter for the 138.
sounds nice.
with 12 ga foil in the crossover, 14 in the filter, & obbligato caps, the crossover components ran over $500...
yeah, good crossover components cost as much/more than drivers, but i don't think i'd want to get in that deep w/ a FF85k...
didn't know solen made non-electrolytics?
the obbligatos are smoother, more transparent than solen fast caps.
serenechaos said:
A couple points:
You went pretty extreme there! FF85k deserves quality components, just because it's affordable doesn't mean its quality is poor. Take a look at the impedance curve, damned near ruler flat. My measurements have borne this out as well. The frequency response is very clean too.
The design I laid out above could be done with very nice components for $60 a speaker.
The normal solen fast caps are metallized poly not electrolytic.
That's all!
badman said:
Do you have FR plots? People with bat ears have made comments about the top ens above 15k and i am investigating that. Up to there it is pretty flat (limit of my kmeasuring kit).
I have had the "opportunity" to dissect one of these (they don't like DC from the amp at least when it is a whole rail 🙂). Besides the surround that comes from the sigmas they sport a copper cap over the pole piece, which gives them as close to a ruler flat impedance above resonance.
dave
Hi dave:
I don't have a good driver measurement system for publishing, but it's good enough for a 'reality check' and to pinpoint issues on my end. We're talking a set of measurements done with Behringer DEQ units, but they're of high enough quality to judge overall trending and find nasty problems. No chance of me publishing any frequency response data until I get a serious measurement suite though. The 85k stayed clean on my test regimen, cleaner than I've seen from any other driver or combo of drivers in the range it was covering. (500Hz up, 2nd order filter)
But in any case, this is a superb little driver. I'm looking forward to putting an ear to a modded pair, but am refining my crossover a little bit first with the stock units (trying to improve phase-tracking, and steepen the woofer cutoff).
Dave, a driver you may wish to play with is the JBL 123A. There are a lot of them around (in varying condition), but it's a lot like a woofer version of the FF85k in some regards. Very extended and smooth bandwidth, large motor but higher Q (in this case, the cone is quite heavy, whereas the 85k loses some of its power via a larger gap to allow the copper).
Combined with the 85k, you can do near-textbook filter alignments, without any out-of-band challenges. It's also a very proficient bass driver, Fs of 25Hz and Qts of .5, which makes many subs look positively wimpy, given that it's also 90dB. It doesn't have the smooth impedance of the 85k but is reasonable through the midrange, with the bulk of the rise taking place above 2k. It was meant to play crossoverless, hence the clean top end.
I don't have a good driver measurement system for publishing, but it's good enough for a 'reality check' and to pinpoint issues on my end. We're talking a set of measurements done with Behringer DEQ units, but they're of high enough quality to judge overall trending and find nasty problems. No chance of me publishing any frequency response data until I get a serious measurement suite though. The 85k stayed clean on my test regimen, cleaner than I've seen from any other driver or combo of drivers in the range it was covering. (500Hz up, 2nd order filter)
But in any case, this is a superb little driver. I'm looking forward to putting an ear to a modded pair, but am refining my crossover a little bit first with the stock units (trying to improve phase-tracking, and steepen the woofer cutoff).
Dave, a driver you may wish to play with is the JBL 123A. There are a lot of them around (in varying condition), but it's a lot like a woofer version of the FF85k in some regards. Very extended and smooth bandwidth, large motor but higher Q (in this case, the cone is quite heavy, whereas the 85k loses some of its power via a larger gap to allow the copper).
Combined with the 85k, you can do near-textbook filter alignments, without any out-of-band challenges. It's also a very proficient bass driver, Fs of 25Hz and Qts of .5, which makes many subs look positively wimpy, given that it's also 90dB. It doesn't have the smooth impedance of the 85k but is reasonable through the midrange, with the bulk of the rise taking place above 2k. It was meant to play crossoverless, hence the clean top end.
planet10 said:
No problem. You can check out Troels Gravesen's FR measurements about halfway down this page
L100 upgrade kit
I've measured a number of these in terms of impedance, and they all exhibit fairly low inductance (by non-shorting ring woofer standards) in the range of .6mH (when the motors have demagged slightly) to .8mH (full strength). Fs is very consistent between 24-26Hz and Qts is between .44 and .57 (higher lost a little magnet strength).
badman said:
I've not had any of those exact woofers thru here but there are quite a few L100s kicking around. I did sell Troels a set of those tweeters thou.
dave
I think the JBL is a 12" and has a much higher Q which makes it more suitabe for OB...
Need to keep our eyes open for some thrashed Centurys with rotting brown foam grills... preferably $20 at a garage sale.
dave
Need to keep our eyes open for some thrashed Centurys with rotting brown foam grills... preferably $20 at a garage sale.
dave
One might do so, but there are a goodly number of reasons to keep the 225k as a widerange mid. While it plays well beyond its miniscule Xmax, it is still a level-limited driver. The Qts is very low due to the tiny MMs and huge motor, meaning you'll have a tough time (a big enclosure, backhorn or the like) getting anywhere near the bottom octave. If you're going to cross over at 400, you're better getting a driver that's less optimized as a pure mid or fullranger, and more optimized as a midbass.
Add to that the higher sensitivity (nobody needs 8dB of bafflestep) and it's just not really well suited for this task. The JBL comes in at 90dB and that gives about 3 dB of bafflestep, which is just about right to work with.
None of this is knocking the 225k, it's a spectacular driver that I very much enjoyed my time with, but it's just not a woofer.
I'd say even at the $150 one can expect to pay for just the woofers they're a bargain. I know of no other 12" at any price that's so flexible, between the clean and extended response, deep bass availability, and sound/build quality. If they have extended response on the top end they're usually lighterweight and don't have nearly the bottom end abilities of these monster woofers.
Add to that the higher sensitivity (nobody needs 8dB of bafflestep) and it's just not really well suited for this task. The JBL comes in at 90dB and that gives about 3 dB of bafflestep, which is just about right to work with.
None of this is knocking the 225k, it's a spectacular driver that I very much enjoyed my time with, but it's just not a woofer.
planet10 said:
I'd say even at the $150 one can expect to pay for just the woofers they're a bargain. I know of no other 12" at any price that's so flexible, between the clean and extended response, deep bass availability, and sound/build quality. If they have extended response on the top end they're usually lighterweight and don't have nearly the bottom end abilities of these monster woofers.
chrisb said:
difficult to design a dipole woofer fore that high sensitivity
But surely nice fore another design
badman said:
At this point, we'll just wait for a set to find us... our first goal is to do an MJK baffle for which we have the Eminence 15".
As well i have some 20+ 12" Foster woofers, althou not of the same build quality, will have similar Fs & efficiency (by the time i finish with them) and a touch higher Q that need to get used up & essentially cost nothing... HF response stock is smooth up to over 2k (but i'll lose a bit with mods)
dave
OK so what I've decided to do is use 4 of the Silver flute 5" per side ( I have 14 laying around) and wire them in 2 pairs paralleled and those pairs in series to get me about 91.5dB +/- and with the FF85K being slightly less efficient I wont have the urge to want to pad the FF85K. I've also opted to run them at 200Hz crossed 6db on the FF85K and second order on the midbasses. I should be good down to the 40's with the four 5" midbasses and in room well below that.
Now my main concern is getting an acceptable baffle width that will support 200hz and below without suck out from the FF85K and still be somewhat W.A.F effective. So I guess what I should be asking is what’s my minimum baffle width allowable for the FF85K OB. I'd love to stay 8 inches wide or less but having little experiences with OB arrangements I'd like some input her if at all possible.
I guess I could do a MMfullrangeMM configuration and leave the back of the FF85K section open at the back, but I worry about reflections off the cabinet, I guess I can guess as much as I want but I have to get down to some serious thinking here, Peace and happy listening.
Speaks
Now my main concern is getting an acceptable baffle width that will support 200hz and below without suck out from the FF85K and still be somewhat W.A.F effective. So I guess what I should be asking is what’s my minimum baffle width allowable for the FF85K OB. I'd love to stay 8 inches wide or less but having little experiences with OB arrangements I'd like some input her if at all possible.
I guess I could do a MMfullrangeMM configuration and leave the back of the FF85K section open at the back, but I worry about reflections off the cabinet, I guess I can guess as much as I want but I have to get down to some serious thinking here, Peace and happy listening.
Speaks
- Status
- Not open for further replies.