von schweikert unifield 3, an offshoot from "fullranger with helper woofer" - diyAudio
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Old 18th September 2008, 03:09 AM   #1
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Default von schweikert unifield 3, an offshoot from "fullranger with helper woofer"

Originally there had been some discussion both on the board, some emails, and some bbq side chat about how running full rangers sealed with a helper woofer.

Now it seems our good friends at http://www.vonschweikert.com/unifield3.htm seem to have thought along the same lines when designing their $15,000 Unifield 3.

With my back log of projects, looking for a house, and raising a toddler the timeline on this project can be considered "long", but thought it made for a great discussion.

and a way to build a speaker (by my estimate) that retails for 17.6 times the raw driver costs.

Looking at the just published images of the http://www.vonschweikert.com/unifield3.htm

Click the image to open in full size.

zoom in on the top "time aligned box"

Click the image to open in full size.

the tweeter looks remarkably like the fountek neo

Click the image to open in full size.

and our fostex fx120 fullranger

Click the image to open in full size.

The woofer might be the seas excel w22e

Click the image to open in full size.

Grand total on the drivers: 2*(89 + 232 + 102) = $846

So, to get the conversation started... are there better woofer options? With the fx120 easily running to sub 20o Hz, why choose a woofer that doubles up on the fx120? I would think a rolling a woofer gently into the fx120 around 150 or 200 would be optimal. Pad the tweet down, and bringing it in ~4k (phase dependent) covers both dispersion and the high frequencies.

Thoughts? Opinions? Guinea pigs who are going to build and test it?
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Old 18th September 2008, 05:43 AM   #2
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Default Re: von schweikert unifield 3, an offshoot from "fullranger with helper woofer"

Quote:
Originally posted by d to the g
So, to get the conversation started... are there better woofer options? With the fx120 easily running to sub 20o Hz, why choose a woofer that doubles up on the fx120? I would think a rolling a woofer gently into the fx120 around 150 or 200 would be optimal. Pad the tweet down, and bringing it in ~4k (phase dependent) covers both dispersion and the high frequencies.
I already have a similar concept (acyally 2 of them) running.

FE127 (in Fonken) XOed to a pair of CSS SDX7 in an aperiodic TL. Actuvely XOed 2nd order at 100 Hz. I have popped a pr of Aurum Cantus on the top but not tried to dial in the XO. I have FX120 on the bench.

The other setup is a single SDX7 XOed to at FF85 (which is a tweeter in its own right) at 333 Hz.

dave
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Old 18th September 2008, 08:29 AM   #3
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Default Re: von schweikert unifield 3, an offshoot from "fullranger with helper woofer"

Quote:
Originally posted by d to the g
So, to get the conversation started... are there better woofer options? With the fx120 easily running to sub 20o Hz, why choose a woofer that doubles up on the fx120? I would think a rolling a woofer gently into the fx120 around 150 or 200 would be optimal. Pad the tweet down, and bringing it in ~4k (phase dependent) covers both dispersion and the high frequencies.
Depends on your crossover points, slopes & what dynamic range you're hoping to achieve. Sub 200Hz is usually preferable from the POV of XO audibilty or lack thereof (we're generalising of course). But, for e.g., let us say, you're designing the speaker primarily for use on orchestral music at high SPLs in a large room. The FX is unlikely to have sufficient excursion to handle the sub-500Hz transient swings & power requirements. So if that's your goal, then you can run a larger bass driver up further to take care of them, insofar as it (usually) has greater power handling & excursion. There's no right or wrong answer really; we're back to what the design goals are, and which compromises you're willing to accept in order to attain them.
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Old 18th September 2008, 09:26 AM   #4
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The cabinets they are using look identical to the pre-finished ones available from Parts Express. I have a curved 1ft³ cabinet in red cherry that looks exactly the same as the one in the pictures. The sizes and finishes they offer are also available through parts express....
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Old 18th September 2008, 10:30 AM   #5
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From their website:

SPECIFICATIONS : UNIFIELD MODEL THREE
Frequency Range: 32Hz to 40kHz (-3dB down points are 25Hz to 50kHz).

Sensitivity: 88dB @ one watt/one meter in anechoic conditions, 91dB in-room.

Distortion: Less than 0.8% at normal listening level (5 watts).

Impedance: 8 Ohms nominal ( 4 Ohm minimum).

Dispersion Window: +/- 30 degrees horizontally at midrange/treble range.

Power Rating: 300 watts peak, 100-watts r.m.s. Minimum of 20 watts.

Connection: Bi-wire cables required, call for details on new VSA cables.

Available Finishes: High Gloss Piano Black or Cherry.

Weight: 190 lbs/pr including stands, woofer and midrange/tweeter modules.

Size: 40 (102cm) tall (on supplied stand) x 10 (25cm) wide x 14 (35cm) deep.
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Old 18th September 2008, 02:47 PM   #6
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Default driver matching to the 120?

So whadya think: Is the ribbon there for marketing purposes, or does the FX120 really want some help at the top?

I'd be interested to hear thoughts about the woofer choice as well.
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Old 18th September 2008, 03:17 PM   #7
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It's a wide-band midrange unit, like most FR drivers, so while it'll have decent treble on its own, 'decent' is not the same as 'excellent' & the Neo ribbon will likely be better & certainly have more HF extension, if you're bothered about stuff over 20Khz. Personally, I'm not a fan of ribbons matched to dynamic drivers, but if they've crossed up high enough (over ~8KHz), that shouldn't be too much of an issue. Again, ballpark figure, but it serves as a rough ROT.

As for the assumed Seas bass driver, looks exactly what you'd expect from them. Should be decent; nasty breakup mode high up, but that's far above the BW they're going to be using it in, so shouldn't be much of an issue assuming the XO design is competant. Personally, I'd prefer something substantially larger (as in a 15in woofer) with a good paper cone, but that's more a matter of taste. Probably a decent enough sonic match to the FX.
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Old 18th September 2008, 03:33 PM   #8
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Default FX120 Top End

hi,

well i'm pretty happy with the top end from the FX120.
Sound quite natural to me. And a crossover at rather high frequencies is not without it's own set of problems. The wavelength at 10KHz is only around 3.5 cm, so spacing between drivers could get a bit problematic.
But relieving it from low bass duties helps quite a bit...

Michael
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Old 18th September 2008, 04:14 PM   #9
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True enough. However, our hearing isn't so great up there, so one plays off against the other, to a certain extent.
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Old 18th September 2008, 04:22 PM   #10
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Default high crossover: difficulty?

"And a crossover at rather high frequencies is not without it's own set of problems. The wavelength at 10KHz is only around 3.5 cm, so spacing between drivers could get a bit problematic."

I've seen a number of single driver types talk about rolling in a tweeter real high, and so I've wondered about this issue before. Is center to center spacing the sort of thing you have to worry about with real high crossed tweeters ~10 khz? I wonder if the wavelength might be getting short enough up there that you can't extract phase info from it anyway. You'd never get away with tweeters helping out the larger FR drivers if you had to sweat that.

May be a can of worms, thought I'd ask anyway.

edit: ah, scottmoose chimes in whilst I type...
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