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Old 22nd February 2009, 02:24 AM   #1
tinitus is offline tinitus  Europe
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Default Strange XO behaviour

Hi

At the moment I am exploring the benefits of relatively simple "low-artefact" crossover
Apart from sounding very good Im strugling with phase issues, and about to give up on 3ways all together

But theres something strange going on, that I simply dont understand

When I make the mid 12uf series cap bigger, the woofers begin to play high midrange

Also quite strange that it actually sounds right with only 12uf series cap on mid

Is this something like with a series filter...but its a pure paralel filter

Does anyone have any clew to whats happening

Thanks
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Old 22nd February 2009, 07:07 AM   #2
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Default the woofer is not making more sound

when you use crossovers at the point of the crossover the frequencies are summed together and most crossover are chosen right before or after a peaking point depending on what part of the network is coming into play. The capapcitot in the midrange is the low end of the frequencies wanted and the coil is the highed cut off point. So it is possible that that you have come across a peak in the low end of the mid range drive FR thus increasing the bass end of the midrange driver go to this website www.diyaudioandvideo.com/faq/xover/ or ccs.exl.info/calc_cr.html and you use the calculators to figure how much you shift the crossover to the lower frequency.
I see a lot of familiar design characteristics in your crossover.
That is a regular midrange design with a peak series notch filter and and antenuation resistor series combination.
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Old 22nd February 2009, 03:59 PM   #3
tinitus is offline tinitus  Europe
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I do know how it works, but thanks anyway fore trying to help

But the issue here is WHY does the WOOFER play significantly more/higher midrange WHEN I make the 12uf cap on MIDDRIVER(SS15W) bigger

I have thought about phase being the reason, but it doesnt seem to be any acoustic interaction...its literally as if the woofer turns into a midrange

btw,
Mid cap 12uf should really be MUCH bigger
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Old 22nd February 2009, 04:19 PM   #4
SY is offline SY  United States
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How are you determining that the woofer is barking in the midrange?

Assuming you haven't made a wiring error, is your midrange a cone? Does it share a common volume with the woofer?
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Old 22nd February 2009, 04:50 PM   #5
tinitus is offline tinitus  Europe
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Quote:
Originally posted by SY
How are you determining that the woofer is barking in the midrange?

Assuming you haven't made a wiring error, is your midrange a cone? Does it share a common volume with the woofer?

"Barking" midrange thats a good way to explain it...its when listening very close

Midrange is ScanSpeak(SS) 15W...5" cone...with its own seperate volume

All drivers have the same polarity right now, but am about to try reversed pol on tweeters, and may help on phase issues
But it doesnt explain why the WOOFERS react so highly sensitive to changes on midrange series cap
I have experienced interaction between the drivers before, but not so significantly as I do now...its really a lot
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Old 22nd February 2009, 06:07 PM   #6
tinitus is offline tinitus  Europe
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Well, reversed tweeter pol cleaned up most of the phase issues, but still some left
I suppose there will always be phase issues with 3ways, if one is very critical...it has always been so, and nothing seems to have changed that

All along it has seemed whenever I achieved good phase I was left with artefacts
And everytime I get the artefacts cleaned up, Im left with phase issues
It happens every time
It a pitty, because the speakers does sound pretty good

As of now Im done with "standard" 3ways
Wont do it and cant recommend it

Next step will be 2.5ways, which I have never tried, but I have my doubts about that too

Alternatively one could go active

Fullrange with a Lyngdorf EQ, which also holds a 2way digital filter, rigth down from 6db and up ... well, Im not ready fore that yet, but right now its tempting


Still, the question remains
WHY is the woofer so highly sensitive to changes on MID series cap...and its not subtle
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Old 22nd February 2009, 06:46 PM   #7
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Quote:
Originally posted by tinitus

WHY is the woofer so highly sensitive to changes on MID series cap...and its not subtle
[/B]
Well... impossible regarding that the transfert function of the woofer cannot be affected by a mid-driver series cap in a // filter. You do obligatory hear something happening from the mid-driver, whatever it can be, lobbing or phase issues from the two drivers combo.
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Old 22nd February 2009, 08:21 PM   #8
SY is offline SY  United States
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Tinitus, it's not clear from your photo (nice work, BTW, very ambitious!), do your midrange and woofer share the same volume in the cabinet or are they in completely separate chambers?
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Old 22nd February 2009, 10:26 PM   #9
tinitus is offline tinitus  Europe
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Yes, seperate chamber fore mid

Yes, it seems to be phase issues all the way

I now have reversed pol on both mid and tweet
In this configuration theres no midrange problem with the woofers

NOW its possible to return to more "normal" components, without having any artefacts

schematic shows what I have changed

It all sounds really nice, but still minor phase issues

I started doing all this because a mate liked to buy them, and I just thought I would correct the very small issues I had with them
But it just seemed to turn crazy on me

The main difference now is that I have reversed pol on tweeter too...and some other minor changes
I might get it right or I may not, cant say really...maybe with some minor adjustments
As said, they sound really very very nice and its all really only phase issues that bothers me

edit...I have a supision that the phase troubles might come from driver/system ressonance impedance peak
I have had components to deal with that, but have removed them because they introduced artefacts
Hell, at this stage I can suspect almost anything, maybe even poluted mains power
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Old 23rd February 2009, 02:32 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

It is possible that by reducing the mid capacitor you are reducing
its interaction with the drivers resonance peak and as such you
are lowering its midrange output, not increasing it.

Try the demo version of Basta! http://www.tolvan.com/products/
for looking at crossover / driver interactions, it is good for this.

/sreten.
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