Crossover for vifa 2 way setup - how can I find out what this crossover is doing? - diyAudio
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Old 1st May 2009, 10:07 PM   #1
Tino is offline Tino  Canada
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Default Crossover for vifa 2 way setup - how can I find out what this crossover is doing?

Hi guys, someone at a shop scetched up a crossover that I could use for a Vifa P17WJ series and a D27TG45 tweeter.

I'm guessing from looking at it that its a 12db / octave but some of the values look odd to me, at least compared to some numbers I get from some programs when I punch in points starting from 2000 and upwards to 4K. I know that what programs give and what happens in the real world are different but I'm at least trying to figure out roughly what the crossover point is.

Also I'm assuming that some of the extra stuff there is for padding down output and maybe some kind of extra filter on the woofer? Maybe some kind of notch filter? I'm a noob so please and thanks...any suggestions welcome.

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Old 1st May 2009, 11:43 PM   #2
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I am not that good at XO's but I can help a little, I think.

The cap coil and resistor parallel to the woofer are known as a series notch filter. This is usually done to control the ever increasing impedance of the woofer coil as the frequency rises although some also use it to create a notch filter similar to the parallel notch filters. It gets a little confusing because a series notch filter runs parallel to the driver whereas a parallel notch runs in series with the driver. They are named as such because of the orientation of the components to one another.

I can't tell you what the .47 cap and resistor are for, it's beyond my knowledge. It looks to somehow allow frequencies above 15K to enter the woofer circuit so I'm guessing there's more to it. The woofer looks to have a 1st order or 6dB per octave low pass.

The tweeter has 3rd order, 18dB per octave high pass.

I didn't look up the info on the drivers so I can't tell you what the XO frequency is.
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Old 2nd May 2009, 02:16 AM   #3
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Tino, I worked out a simulation for you (in very similar terms, and it looks very good). Drivers with same polarity as in the xover input.
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File Type: gif 2way vifa p17wj wo & t27tg tw.gif (21.1 KB, 387 views)
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Old 2nd May 2009, 03:28 AM   #4
Tino is offline Tino  Canada
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Wow thank you Inductor. I feel better now. I wasnt sure if the components would have been right just because it didnt seem to line up with what most programs were generating for standard component lists.

I should say that the shop I got the crossover setup from does custom speakers but I wanted to doublecheck because it just seemed to be so quick that the person came up with the crossover. I guess he's very familiar with the combo.

I'll let you guys know how the speaker turns out and I'll post some pics. I think I'll be done in a week.

...now to find out how to come up with high gloss black finish. I was going to paint the speakers black, then put clear on it and wet sand the clear and buff it. I'd think this should give me a black glassy look - kind of like a paino I hope anyway.
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Old 2nd May 2009, 01:37 PM   #5
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Quote:
Originally posted by Tino

I should say that the shop I got the crossover setup from does custom speakers but I wanted to doublecheck because it just seemed to be so quick that the person came up with the crossover. I guess he's very familiar with the combo.
Well, you can say that Tino, he is a genius. If this speaker is for a Solid S Amp, I wouldn't change a thing (the wo is phase aligned with the tw 100% in the xover band). If you want to make some tests and experiences (you can also) try this one, were you can change the attenuation on the L-Pad. (It's set for ~7dB on 6Ohms circuit). Feel free to Diy. Use audio grade quality resistors with enough power for your app. and non inductive for top freqs.
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File Type: gif 2way-diyaudio vifa p17wj wo & t27tg tw 2-order.gif (25.8 KB, 370 views)
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Old 2nd May 2009, 03:38 PM   #6
Tino is offline Tino  Canada
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Sweet. Thanks again Maybe I should go to the shop and ask them if they wouldnt mind me giving them some praise on this forum and their store details. I dont think they are very active on the web...they are more old school. They sell components and do custom speakers and studios. Long ago I heard someting they built and its left me floored still. It was a pair of Dynaudio 6.5" woofers and a Focal tweeter in some monster floor standing setup. It was 6' tall and the drivers were angled a little. Top driver was angled down a few degrees and bottom driver angled up and tweeter in the middle. Its the best speaker I've heard I think.

If these drivers were current production drivers, I'd feel guilty about posting it since it might have meant lost sales and stuff but when I was speaking to the main guy, he said they dont make these drivers anymore or something like that. Anyway he did sound really smart and now that I can see on the graph, teh approx freqency response and crossover points, I am happy
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Old 2nd May 2009, 09:54 PM   #7
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Probably (they were) it's a John Dunlavy design. He used it (tweeter D27TG-35-06 and D27TG-45-06) in the Dunlavy Audio Labs Signature SC-VI loudspeaker. Have fun.

Read about John
http://www.stereophile.com/interviews/163/
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Old 12th May 2009, 01:00 PM   #8
big1 is offline big1  Australia
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Default Help 2.5

HI
Can some body help me. I would like to use this xover in a mtm using 2- p17`s ,what would i have change?
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Old 16th May 2009, 12:29 PM   #9
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Default Re: Help 2.5

Quote:
Originally posted by big1
HI
Can some body help me. I would like to use this xover in a mtm using 2- p17`s ,what would i have change?
big1,
You can adjust the xover yourself from this one here.
1) If you feel that you need the midbass stronger right before and over the xover band give it a 0,82mH in the place of the 0,9mH.
2) If you want to reduce the 2 Vifa P17WJ a little, for 1dB or soo, place a 1,0mH instead.
Also use the thickest wire for the inductor that you can find, not less than 100W, 16AWG should be better than 18AWG.
Note: This is just a simulation and might not be exact.
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File Type: gif xover mtm.gif (24.9 KB, 208 views)
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Old 17th May 2009, 01:21 AM   #10
big1 is offline big1  Australia
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Hi inductor
I`am using jaycar 20awg 1,o mh that must be why the bass is soft,I have a 18 awg 1,0mh come in the post friday . Reading what you say ,all I can find is 0,9 mh18awg or 0,82mh 15awg may have to try shopping some were new.
ps can I unwind the inductors ?
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