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  #1  
Old 05-09-2010, 08:47 PM
Bassphil Bassphil is offline
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Vanderteen Sub- Have You Built Your Own X-2 Crossover?

Hi everybody! I have a few questions about the X-2 high pass filters for Vandersteen subs. I've been scouring the internet, but haven't found many threads that tie in all of the information. Most are incomplete, so any advice you can offer here will hopefully help future generations!

I want to build my own X-2's primarily because I've read that you can use much better caps than what ship from the factory. I feel that since these X-2's are sitting squarely in the middle of the signal chain, I should use to best caps available.

In case you need my system's info, I have an Audio Research SP-11 MK2 running into a pair of Cary Slam 100 monoblocks, which power my upgraded Magnepan MG12's and a stereo pair of Vandersteen 2W subs.

Here is my two part question: What brand of caps are the best, and how are the X-2 high pass filters assembled.



First, let's talk about cap choices. I'm not exactly sure how caps work in this particular high pass situation, but what is important to me is that they don't color or alter the sound as the signal passes through them. I've installed Auricaps in my Magnepan MG12 crossovers, and they result was tremendous! However, I've read a few posts where people have used VH Audio TFTF caps in this situation and mentioned that they're the best. They're also twice as expensive.

For this situation, is there some kind of pass or fail threshold that you reach? In other words, is a more expensive cap going to do a "better job" (i.e. more neutral, less coloration), or basically as long as you have a quality cap (like the Auricaps) you won't hear a difference.

Oh, and I noticed that caps have volt ratings- 250V, 400V, 600V.... Which one would I pick?

Does that make any sense? Sorry to the newbie question, but I know there are a lot of people out there who've spent more time listening to the sonic differences of caps than I have with interconnects!



The second part- construction.

Okay, so I know that caps are directional. I also know that I'll need a male RCA and a Female RCA plug to wire the cap into. I also know that the one wire sticking out of each end of the cap will go to the center post of those RCA jacks.

What I'm wondering is, will I need to solder a wire between the sleeves of those RCA jacks. I'm guessing that I do, but I'd like a confirmation on that if anyone knows.



Right now, I'm still in the stages of figuring out the frequency I want the X-2's to be. When I've made a decision, I'm going to write to Vandersteen to get the cap value that I need.


Thanks in advance for any advice that you can offer!

-Phil
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Old 05-09-2010, 09:59 PM
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krikor krikor is offline
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I used to own a Vandy 2WQ that I used with my Maggie 10.1s and built the high-pass crossover using InifiCaps. To calculate what value to use, you need to know your amp's input impedance and what frequency you want to crossover at ... which with the 2WQ it is supposed to be right around 80hz since there is reverse EQ in the subwoofer.

From there its just a matter of calculating the cap value for a first order high pass filter. If I remember correctly, solve for "C" (capacitance) in the following equation (where R is your amp's input impedance):

Frequency = 1/(2piRC)

Actually, it's just easier to use one of the online 1st order high-pass filter calculators (such as this one http://www.the12volt.com/caraudio/crosscalc.asp). So for example, an input impedance of 20000 ohms and high-pass set at 80hz will result in about a .01uf cap

Hope this helps... I simply soldered the caps in line with the signal lead of my interconnects going to the amp.
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  #3  
Old 05-10-2010, 02:12 PM
Bassphil Bassphil is offline
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krikor! You are awesome! Thank you for taking the time to post!

If I could just bother you for a little more to make sure I'm doing this correctly...

I looked up the specs for my Carys, and I think that there may be a typo, though I can't imagine that they would make that kind of mistake. Under "Input Impedance", it has 150,00 ohms. Did they leave out a zero, put the comma in the wrong place (both of which I doubt), or is that how you write ohms? So, I would enter 15000 in the field of that calculator?

... Here's a link to the PDF of the specs:

http://www.caryaudio.com/pdfs/manual...e/SLAM_100.pdf

Now, just to make sure that I'm thinking of this correctly, I have a question about the WX-2 box that has the adjustable dip switches. If I understand this correctly, the dip switches are used to match the impedance of the power amp, NOT to adjust the frequency of where the bass crosses over, right?

That's the confusing part to me, since it seems like the more dip switches I turn on (the 200Kohm setting) the less bass there is in the front speakers, and the 5KOhm setting sends more bass to the fronts.

About your selection of InifiCaps. Did you try different brands? Are the InifiCaps supposed to be the best and/or most neutral? I Goggled them, but I can't seem to find a place to buy any, though I did read a post about how his caps are supposed to have an exceptional signal transfer.

What about the Volt rating on some caps?

And finally, about the construction, when you say "signal lead of my interconnects", are you talking about the wire that connects to the center post of the female RCA? If so, then what you are saying is the cap gets soldered into what would be the sleeve wire of RCAs?

Man, thanks again for your time!

-Phil
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Old 05-10-2010, 07:30 PM
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krikor krikor is offline
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No mistake... 150K ohms input impedance for a tube amp is likely. And yes, the WX-2 is designed to match the input impedance of the amp, not set the crossover (highpass filter) frequency. The sub itself is equalized internally to gradually INCREASE bass from 80hz and lower at 6db/octave. Therefore you want a filter before your amp that REDUCES bass from 80hz and lower at 6db/octave so that the net result is flat.

Of course, by setting the filter for a higher impedance amp you effectively raise the xover point (take more bass out than you need to) and reduce the amount of final bass output... or vice versa set it for a lower impedance amp and effectively lower the xover poiint (take less bass out than you need) which increases final bass output.

Using the first-order high-pass filter link I included previously, your amp would require .01uf caps for 80hz (.01326 to be exact). If you want a bit more bass output, use a slightly larger cap (.01768 for 60hz) or a slightly smaller cap for less output.

As for caps, I did not try a lot of different ones, partially because the InfiniCaps were already a pricey proposition and I didn't want to go through a lot of money as I needed several per channel to get the right value and I was using balanced interconnects which required on cap on both normal and inverted signal lines. Lots of good ones out there with varying reputations and opinions from users... can't help you a lot there. Voltage rating shouldn't matter since you are using these at line level, not speaker level voltages as you would in a speaker xover. You'll want to get them matched if possible to preserve bass balance between the two channels.

Yes... solder the cap to the center pin of the interconnect jack at the amp end and the center conductor wire to the other end of the cap so that signal goes through the cap (inside the "sleeve" of the RCA cable). Ground wire simply goes to ground (no cap).

Hope this helps.
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Last edited by krikor; 05-10-2010 at 07:33 PM.
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  #5  
Old 05-10-2010, 07:32 PM
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krikor krikor is offline
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By the way... unless I'm mistaken InfiniCaps are now called DynamiCaps.
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Old 05-13-2010, 10:38 AM
Bassphil Bassphil is offline
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Man, thank you soo much for the information! You have just created the only comprehensive resource on this. Now all I have to do is figure out what settings I like.

If you don't mind, I have one more question just to clarify the use of the calculator. You have to enter 80 into the frequency field no matter what frequency you enter into the impedance field, right? When you mentioned that switching the dip switches changes the crossover point, that got me to thinking.... Great explanation of that, by the way!

Soooo, if you have a lot of free time and love to type, my friends and I would love to know what's so special about Vendersteen's fancy high pass filter- the M5-HP (if you happen to know anything about it, and I'm guessing that you do :-) ).

The public opinion is that the M5-HP sounds better than the X-2, but it seems to me that if you make your own X-2 with high quality caps, then that should sound better since there's less crap in the signal chain. Also, using a 9 volt battery is a mystery to me. Is that there to reinforce the signal as it works it's way through the circuit?

Anyway, if you have time and feel like chatting, enquiring minds would like to know.

Thanks again for all of your help!!

-Phil
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Old 05-13-2010, 01:49 PM
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krikor krikor is offline
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With regards to the calculator and determining the correct cap value for your high-pass filter, you don't "have to" use 80hz as the roll-off frequency. But that is what the equalization inside the sub is designed to match. If you want more bass output, use 60 or 70hz... if you want less bass output use 90 or 100hz. However, either of these approaches may create an unwanted bump or dip in your bass response (not just more/less), so in that sense it should remain 80hz to match the design goals of the sub... no matter what you do with high-pass filter, the equalization inside the sub-amp is preset to reverse an 80hz roll-off (that can't be changed).

Likewise you should enter the actual input impedance of your amp in the calculator, and if you change your amp to one with a different impedance, you'll need to determine a new cap value for that amp to maintain an 80hz roll-off. You don't "have to" enter the actual value, but any change will affect the high-pass roll-off point just as it would with a change to the cap. It's all one big interrelated see-saw.

First thing... determine if 80hz is where you want it to roll-off. You can get some rough idea of higher/lower settings by playing with the X-2 DIP switches, but for finer control use some inexpensive caps and try those before spending a lot on pricey ones.

FYI - if you want to know what each DIP setting corresponds to in terms of capacitor value instead of input impedance, just use the calculator. Enter the impedance label for a given DIP setting and set frequency to 80hz, then record the corresponding cap value that results. You could then reverse calculate the roll-off of each cap value for your amp's impedance (not sure there is calculator for that, but the formula posted earlier is easy enough). [If you post the impedance values listed on the X-2, I might have some time to help you out with this]


As for the M5-HP, my dealer loaned me one to take apart years ago to see if I couldn't come up with a simple version of my own. As I understand it, the 9V battery is used to somehow provide a constant bias for the capacitors. Unfortunately, that's as far as I got and never figured out the exact circuit and never did any listening with it. I used to have a diagram for something similar from InfiniCap, but I lost that awhile ago.

Sorry I can't be more help on that topic and I hope I was making sense here, not rambling. I'm happy to lend a hand.
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  #8  
Old 06-07-2010, 12:02 AM
Bassphil Bassphil is offline
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Hi again!

Okay, so I'm almost ready to build my filters, but I have one more question. How in the heck does one find the right value caps? It seems like there's basically a few caps in the range that I need.

I thought I'd try three values to see which I like best:

150K, since that matches the impedance of my amps
100K, since that seems to be a nice setting according to the WX-2
75K, since that also sounds nice.

Now then, when I throw those values into the calculator, I end up with these cap values (rounded up):

0.013uf
0.012uf
0.026uf

When I sift through PartsExpress.com and various other websites, I can't seem to find close enough matches. The common cap values in that range seem to be 0.01uf, 0.022uf, and 0.033uf, which is about 190K, 90K and 60K respectively.

Is there a website that has a better selection of caps, or am I over-thinking things?

Thanks again for your time!!

-Phil
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Old 06-22-2010, 10:42 AM
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krikor krikor is offline
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I think your cao numbers are off a little. For an 80hz roll-off, I get the following for each amp input impedance:

150k = .01326 uf
100k = .01989 uf
75k = .02653 uf

Actually, now that I look at it, I think you just meant .020uf for the second number.

I would worry about getting exact exact, but in the ballpark. You are probably OK to try those listed and see how it sounds. You can also use multiple smaller caps in parallel to reach the value you need. For example two .01uf wired in parallel (not series) to get .02uf.

Also, tolerances of caps can range a bit so you may want to measure them before trying out, or get matched caps for your final build.

Also, the tolerances may be off by
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Old 06-22-2010, 10:45 AM
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krikor krikor is offline
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Other sites for caps:

http://www.partsconnexion.com/
http://www.percyaudio.com/
http://madisound.com/
http://www.soniccraft.com/
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Old 06-22-2010, 11:40 AM
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chadnliz chadnliz is offline
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Its funny this popped up, my dad just bought 2 new Vandy subs a few weeks ago and when I hooked them up they come with outboard filters that are label "for temporary use", well we dont need them as his Aesthetix Atlas amp has built in High pass filters. I was wondering about their use in either my M&k speakers that subs roll off at 80hz or giving them to anybody who needs them.
There is nothing "temporary" about them, they are adjustable and look of good quality, Vandersteen must prefer a more premium offering to make more money.
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