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Old 15th September 2008, 11:57 PM   #1
Face is offline Face  United States
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Post Need input on a Vifa and Silver Flute 2 Way

I'm looking to make my own version of these speakers, the Gemme Tanto: http://74.59.244.35:9081/gemmeAudio/.../Products.html I recently demoed a pair and was floored by the sound. But since I'm handy with a table saw and don't have the kind of money they were asking, I thought I'd try to make a pair of my own.

They appear to use a Vifa XT19 and 6.5" Silver Flute woofer. From what I hear, the capacitor used is a Mundorf S/O. Also, the woofer has no x-over and is 8ohms, making the speaker closer to 6 ohms.

Since my room is a black hole for bass, I'd like to use one of the 8" versions of the Silver Flute woofer, specifically the W20RC38-S. It digs nice and deep, and from what little I know, it looks like it should work well with the XT19 since they're also close in efficiency.

Here is my WinISD plot: http://www.cleanandquiet.com/upload/...ilverflute.jpg

So does this look like a go or am I way off base?

Thanks for any help!
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Old 16th September 2008, 05:02 AM   #2
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Default Um, hmm...

Although I am a big fan of Vifa's concentric dome tweeters and Silver Flute's build quality, I have to say that design sort of files itself in my brain as "that doesn't really seem possible."

I dunno. I have only used the Silver Flute 5.5" midwoofer, which is quite good for the price. But I can't really imagine running it full-range, as there is cone breakup. The reason I haven't tried the 6.5" or larger is because I couldn't find a box alignment for any of them that was reasonable in size that got an F3 any lower than about 47 Hz. Now yours is almost 90 Liters, which is pretty huge for a 2-way. I'm not saying it wouldn't work... in fact, I'm thinking that's gotta be the minimum size to get a nice low F3.

However, you say you've heard these speakers and you really liked them, so I'm definitely not here to rain on your parade. In fact, I'd like to see this project work for you. So let me see if I can help:

I would not go for the larger Silver Flute woofer . I understand your craving for bass, but I just don't think it's going to make the leap all the way up to a 6 KHz crossover point. I'd try to match the original design using the W17RC38.

I'm not the best at box modeling, but I'm not terrible at it, either. I honestly don't know how to get much low-end extension from that driver's T/S specs--unless you put it in a pretty big box (45 L or so) and tune it to 35 or 40 Hz. This gets you an F3 of maybe 40 Hz, but the knee of the bass is a bit awkward. It's sort of verrry gradual taper off from 800 Hz down, then a bump at like 50 Hz before dropping off. But maybe the folks over at Gemme were doing something unorthodox. "Vflex turbo-charging sub-bass technology"

Anyway, the tweeter (a fantastic tweeter, by the way) needs a REALLY high crossover point if you're using 1st order electrical. Their literature says it's 6 dB down at 6000 Hz. A simple cap on the tweeter isn't enough, though. The roll off looks ugly, and I'm sure it sounds worse. Plus, the tweeter is definitely louder than the woofer. So I'd suggest at least an L-pad (though an LCR impedance filter would be even smarter with that particular tweeter).
I tried modeling up the XT-19, and it can actually hit a pretty accurate 1st order roll off with this XO:
(in series before tweeter) 6.2 uF cap->1 Ohm resistor
(in parallel w/ tweeter) 5 Ohm resistor
Would it sound like anything? Beats me. But you need SOMETHING to compensate for the large impedance spike in the tweeter, and it just so happens that a 5 Ohm resistor in parallel will do that. HOWEVER, this is a pretty brutal load @ 3 Ohms. Then again, that's not counting the 6.5" woofer running full-range... which could throw the system impedance an a whole new direction

I'm just trying to help. Not sure if I did
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Old 16th September 2008, 07:17 AM   #3
Face is offline Face  United States
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Default Re: Um, hmm...

90 litres isn't much when I'm used to staring at a pair of 15" Tannoys in 200 litre cabs.

As for their "Vflex turbo-charging sub-bass technology", from http://www.dagogo.com/GemmeTanto.html , it appears to be horn loading with a traditional port at the end.

Impedance isn't much of a concern here with my gear.

Thanks for your help.

EDIT: It appears I can't edit my original post, the woofer is a 4 ohm driver, not 8.
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Old 16th September 2008, 09:58 AM   #4
sreten is offline sreten  United Kingdom
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Quote:
Specifications:
Type: 1.5-way small tower speaker with Vflex turbo-charging sub-bass technology
Frequency Response: 18 ~ 30kHz
Sensitivity: 91.5dB
Impedance: 4Ω
Recommended amplifier power: 20 to300 watts
Drivers: 6.5" mid/bass driver in wool/paper cone,
0.75" Ring Radiator tweeter
Crossover: 6dB @6kHz,
single-capacitor crossover on Ring Radiator Tweeter,
no crossover on main driver
Dimensions: 36" H x 10" W x 16" D
Weight: 80lb each
MSRP: $5,495
:bs::bs::bs:, /sreten.
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Old 16th September 2008, 12:35 PM   #5
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there's a project here using the 8" including actual measure T/S parameters, they seem to vary quite a bit from those published : http://chadgray.info/projectdetail.cfm?ProjectID=24
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 16th September 2008, 03:44 PM   #6
Face is offline Face  United States
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Quote:
Originally posted by sreten


:bs::bs::bs:, /sreten.
I had a feeling that may be the case.

Thanks for your help everyone.

So any recommendations for a large two way using a Vifa ring radiator?
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Old 16th September 2008, 05:05 PM   #7
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Quote:
Originally posted by Face

I had a feeling that may be the case.

Thanks for your help everyone.

So any recommendations for a large two way using a Vifa ring radiator?

That IS a good question. I'm not completely sure where to point you, but this guy uses them a lot:
http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm

Also, this article details a design for it combined with a HiVi M8a
http://www.htguide.com/forum/showthread.php4?t=22862
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Old 16th September 2008, 07:29 PM   #8
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Another one that could be very good:
http://www.zaphaudio.com/ZD5.html

I haven't heard this particular design, but the 8530K Revelator is an amazing midwoofer, and this is a pretty "basic" 2-way floorstanding design--although the XO is pretty complex. For its size, the bass the 5.5" Revelator produces is miraculous. (don't get me wrong, the midrange and dynamics are outstanding too) I have never heard or seen anything else perform like it.
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Old 16th September 2008, 08:32 PM   #9
Face is offline Face  United States
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Thanks for all your help and suggestions.

I'm probably going to try something a little different...and bigger.

I've done some reading here on the Vifa XT25 in a wave guide and also of the Peerless 830669, it appears they make work together. I'll start a new thread in this section.

Thanks again for your help.
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Old 26th September 2008, 02:24 AM   #10
Face is offline Face  United States
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Going back to this...maybe.

After thinking more and more about OB designs, I may use the SF woofer as a mid and add a OB 15, maybe two.
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