what is FF225K's real xmax? - diyAudio
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Old 8th July 2007, 04:08 AM   #1
freddi is offline freddi  United States
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Default what is FF225K's real xmax?

as in comparing its distortion with say 206E? which is cleaner up to 1.5mm stroke?
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Old 8th July 2007, 08:49 AM   #2
hm is offline hm  Europe
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hello Freddi,

o,3 mm to bad for bass,
http://www.fostexspeaker.de/fullrang...ie/ff225k.pdf,

compression and distrotion below 1 W also in a horn.
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Old 8th July 2007, 02:32 PM   #3
freddi is offline freddi  United States
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Hi HM -

for a 186 liter 2.5M BLH, 0.3mm would allow about 1/5 watt input to reach 0.3mm around 55Hz.

Eminence revised their ALpha 6 which had winding height ~equal to gap height and now calls it "3.5mm" using some distortion figure. I think they did the same with 12LT which is now called "12LTA"

some drivers have a pretty good fringe field - I think Altec 421 is one.

does 225K go out out control fast when past 0.3mm?

does too much stroke in a fullrange or wideband invite audible modulation distortion?

Best
Freddy

Simulation of 225K vs 206E wall + floor boudary

http://img146.imageshack.us/img146/3...hff225kpv6.gif
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Old 8th July 2007, 06:14 PM   #4
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In sonic terms they don't appear to loose it too badly at all -I was listening to a pair in Will's Jericho horns a few weeks back, and they sounded very nice indeed. They work well in pipe-horns too, as do the 165s, although I suspect the technical performance wouldn't look so hot, so YMMV as ever. Luckily, the distortion is going to be in the LF, where our hearing isn't great. From that, I suspect the distortion rise is pretty gradual. As Nelson commented elsewhere, probably best not to feed them the Jurassic Park soundtrack, but so long as you don't go crazy, they're a nice listen.
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Old 8th July 2007, 06:28 PM   #5
tinitus is offline tinitus  Europe
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Isnt it a midrange intended to be used with a big woofer ?
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Old 8th July 2007, 06:41 PM   #6
badman is offline badman  United States
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I use a pair loaded with Rethm The Second cabinets (Odd horn/acoustic labyrinth hybrid) and they can generate enough output for my small room, getting beyond xmax and do just fine there. People get way too hung up on specs, the arrangement of similar gap and voicecoil height looks bad on paper, but sure sounds good here.

It's a very smooth and clean sounding driver, I think they struck a good balance between bandwidth and linearity. hell of a motor on it.
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Old 9th July 2007, 07:47 AM   #7
chrisb is offline chrisb  Canada
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Quote:
Originally posted by badman
I use a pair loaded with Rethm The Second cabinets (Odd horn/acoustic labyrinth hybrid) and they can generate enough output for my small room, getting beyond xmax and do just fine there.
I continue to recall a pair of this Rethem enclosure heard at VSAC2003 with highly modified Lowther driver, as the most "unspeaker like" magneto-dynamic device I've ever experienced. Brilliant design.



Quote:


People get way too hung up on specs,
no effen kidding If you were to somehow compare "measurements" of a Stradivarius or Bosendorfer to a high school band instrument, would that make a performance by Perlman or Chick Corea on either of the latter suck?

Quote:

the arrangement of similar gap and voicecoil height looks bad on paper, but sure sounds good here.


It's a very smooth and clean sounding driver, I think they struck a good balance between bandwidth and linearity. hell of a motor on it.
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Old 9th July 2007, 10:03 AM   #8
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I just recently built a horn and installed an FF225K in it. I am in the process of aquiring the necessary equipment to be able to measure its response. The horn is tuned to ~ 35Hz, and is about 2.65m long. The Sd/St ratio is 4:1. I see that this driver (Going by eye) has no problem with 2-3mm of excursion. The speaker is very smooth sounding and has surprising good and low bass. All I can say until I do the measurements is that if I compare it to my FE208E Sigmas in the BK20, the bass is lower and it is louder when driven at the same wattage.

I kind of asked this question on the Fullrange driver website. If the SPL of the bass is really based on volume/velocity, couldn't a driver especially when horn-loaded make up for its xmax in the strength of the motor? Strong transient response resulting in higher compression/amplitude of a smaller volume?
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Old 9th July 2007, 02:58 PM   #9
badman is offline badman  United States
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That's what compression drivers are for awhite. If you want them to go low..... they're gonna be big and COST.

The FF225k has a great response curve compared to other high-efficiency fullrangers- relatively smooth without the brutal top octave breakups and whatnot, better to use a tweeter (or a supertweeter) than have to deal with those shennanigans. The bass response is also fairly good compared to 'rising response' style drivers (which are generally quoted as more efficient, but have less actual output)

Short version- this driver isn't meant to flop around, but this style of driver can be overdriven without horrible sonic penalties (anyone remember how unfounded people's concerns about the .5mm xmax of the Audax PR17OMO were? Lots of high efficiency and pro midrange drivers have limited Xmax, but don't misbehave the way you might expect when overdriven.
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Old 9th July 2007, 03:06 PM   #10
freddi is offline freddi  United States
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I think application of horn-laoding can make up to a point - especially vs direct radiator

looking at sims, some horn can interchange 6" and 8" drivers with little response change - but the smaller driver will have more excursion overall

how much excursion is permissible with fullrange say on a passage with flute and sustained electric bass notes before modulation and gargle become too much?

FF225 sim with ST,Sm ,CC fixed varying path length and bulk
http://img182.imageshack.us/img182/1...m25m35mvs7.gif

FF225 max ouput at 0.3mm, 1mm, 2mm & 3mm strokes
http://img182.imageshack.us/img182/9...aryxmaxfy9.gif
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