Hey Dave hows the FF85K OB at 400hz.....?

[chrisb]

Originally posted by badman
Hi dave:



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).

as might the FF225K be considered?

[planet10]

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

[badman]

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.

Originally posted by planet10
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

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.

[tinitus]

Originally posted by chrisb



as might the FF225K be considered?

difficult to design a dipole woofer fore that high sensitivity

But surely nice fore another design

[planet10]

Originally posted by badman
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.

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

[speakrsrfun]

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

[tinitus]

If you think you loose too much sensitivity below 500hz, just ad more SilverFlutes...now you have plenty of them

Its not by the book, I know

Maybe its possible with some kind of power taper with 2 different series inductors

[chrisb]

Originally posted by planet10
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

late to note - brain fart - I must have been thinking LE8T, and of course even at that, the two (LE8T / FF225K) are probably apples and oranges.