Modding A Crossover Part 2

VR3

Yes, back on the subject of modding crossovers!

Of course, I am giving my mains a 'make-over' as far as an enclosure goes, so why not the crossover to, right?

Well, now I am getting a bit more serious about taking this on, and am actually looking for replacement parts...

Here is the crossover -


I plan to replace all of the caps, I looked up the resistors and found that they looked the same and figured there wasnt any difference, so I won't even look into that unless someone mentions otherwise...

Here is another question, I am looking at Solen caps, and The only replacement for the 8 UF cap is an 8.2 UF Cap, will this difference make a huge difference or is it close enough that it wont matter?

Here are the values I have come across thus far - the small electro - says 8 UF --- 100 v --- BP+/-10
Larger Electro - 15 UF --- 100 v --- BP+/- 10
The green capacitor says - CL 21 --- 3.3 UF J --- 100 V
pink one says - 85 K --- 100 V ---D

I cant really seem to locate the pink caps value, but I cant really remove the crossover all the way that actually has the value visible... so I will have to look later...

Now comes the other question, I have been told the crossover wouldnt be to bad to mod, just take out the old caps, glue the new caps on top of the inductors (new cap wont fit between) and call it a day, but I am afraid it wont fit in the enclosure since a Port is directly above it!....

So now I ask, how hard is it to completely rebuild the crossover, and what would it take to do it? What would it take to save the inductors, etc?

Thanks!

PS: Here are the replacement caps I found...

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=027-544 - 3.3 UF

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=027-576 - 15 UF

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=027-564 - 8.2 UF

unc2701

With out you drawing out what the circuit looks like that's a tough call, but I'm guessing that you've got a 2nd order L-R crossover- The pink cap is probably about the same value as the green cap. Values of 3.3 uf on those would give you a crossover point of 3000hz- look in your manual to see if that's about right (i'm assuming 8Ohm nominal for the total hi & low impedence). The other caps & resistors are for a zobel network- i think. The ones that really matter are the primary caps for the hi & lo pass; the zobel ones don't affect sound as much (and you can probably get away with 8.2 vs 8).

I would highly recommend copying the circuit path & making your own from scratch rather than modding yours (and possibly destroying them). It's not that hard and you can get blank boards from parts express. If I'm right about the crossover point & impedence, then the inductors you need are .85mh. Generally you see one air core & one iron because it's easier to get an orthogonal configuration with those.

I doubt you're really going to see huge improvement, but for about $50, why not try?

VR3

The speaker actually is like around 6 ohms, they dont really specify, they say 4-8 ohms (which depicts to me as 6 ohms) - the crossover itself is a link-witz riley, not sure of the xover point.

They are *very* secretive of the actual design of all of their current products...

Thanks for the response

How do you copy a circuit path? Hell...how do you make a circuit path?

jcaut

You might reconsider replacing the resistors. They can make just as much difference in the sound as different caps, IMO---- more difference than better inductors will make. The stock resistors are probably equivilent to very cheap sandcast resistors. The one on the Zobel network might not be worth replacing, but if one of the resistors is for tweeter padding I'd replace it with an audio-grade, like Mills.

8.2uF vs. 8uf is not likely to make much difference. You can parallel capacitors together to add up to the value you need. IOW, use a 3.3 in parallel with a 4.7 to make 8uF.

The inductors shouldn't be too hard to re-use, if you remove them carefully. If you can de-solder them, you can just trim the ends a little and scrape off the coating then re-solder. I would try to re-use, rather than replace, the inductors. A hair dryer, used carefully, should soften that glue up enough that you can peel it off.

It's sure a lot easier if you can just replace caps and resistors on the existing board. Would the caps fit on the bottom of the board?

Jason

unc2701

follow the little lines on the board- they connect all the components- so start with where the positive comes in from the speaker terminals, trace that to the next components & so on.

You should google "crossover circuits"- You really have no business mucking about with components until you have a good idea of how they're usually laid out.


As for making a circuit board, you can get a kit from parts express that lets you etch your own traces or you can get a board that has a bunch of holes drilled in it & you make connections with short lengths of wire. You'll find fans of each- the conductor on a circuit baord is a thin layer of copper, which doesn't have the same electrical properties of a nice round wire, but soldering together a bunch of wires to go point to point can somtimes be a pain.

VR3

So who has the experience under the belt to mod these things that wouldnt mind modding these on a free afternoon for me (I'll pay for it of course) - I don't want to risk messing up the crossover with my inexperience, and at around 60 dollars for a replacement crossover, its not worth attempting because of what might happen....

And yes, there is room on the bottom of the board, infact... nothing is on the bottom of the board...

PolkThug

Looks like that crossover spent some time in a **** movie.

jcaut

Ewww...

Now I'm not touching it.

Thanks for the heads-up, Polk Thug!



Sid: I might be able to help you. There's a port right against the side where the components are located? But nothing in the way on the other side? How big is the terminal cup that the board is attached to, or rather, how big is the hole in the back of the speaker that the crossover has to fit through? E-mail me at jmec-at-cswnet- dot-com if you want to talk about it.


Jason

VR3

The hole is 3" wide by 4.75" tall

The terminal slides in from the bottom up (IE: the 'pc board' is at the bottom of the terminal)

Actually, now that I think about it... the crossover goes in vertically to the port, so nothing would interfere with it. However - everything would have to be mounted where everything is at now, or above everything...

VR3

Before Images Of Crossover

VR3

Crossover before pic 3...

After pics coming in 2 or so weeks!

VR3

JCaut sent me a teaser photo yall..

I'm STOKED!!

VR3

Difference between the 15 UF caps...

Check out the difference in resistence...

VR3

8 UF Cap differences..

VR3

Here is the highpass network...

Def Tech originally used a 6.7 (I believe) bypassed by a 3.3 UF cap to get a total of 10 UF - we took this a bit farther and did a 10 UF cap bypassed by a .01 Film & Foil cap...

Airplay355

what lines are what and what does that mean? interpret the graph for me lol

VR3

If you notice, Jcaut explained alot of about the graphs in captions under the pics...

Everything I know about them is what those pics tell me...

Airplay355

I did notice, and i still don't understand lol

VR3

Well..

The phase has a flatter response after 10khz more than the stock caps.... the aftermarket caps are alot flatter...

The vertical measurement is the overall I guess, and 2 of the 3 graphs is comparing it to the stock cap... as you can see, they are about spot on, so the values were hit spot on pretty much...

Then you have the resistence difference, the lower the resistence, the better -- and all of the resistences are MUCH lower.

audiobliss

By saying the resistances are lower now, are you saying that your speakers are now lower impedance and are now requiring more current from your amp? So the crossovers determine a speakers impedance? I sorta thought the actual driver determined the impedance....

jcaut

These don't tell anything at all about the impedance behavior of the speaker system as a whole. That's determined by the drivers, and how they interact with the crossover.

Most of these graphs are no-load impedance sweeps of the individual crossover components, showing the impedance of a capacitor (for instance) as the frequency changes. A cap's resistance (impedance, more correctly) goes up as frequencies go down. At high frequencies the impedance approaches zero. They also alter the phase of the signal by -90 degrees. An inductor is a curve the other way, with impedance going up as frequency goes up and the phase change is +90 degrees. A resistor should show a flat line and zero phase change at all frequencies. All those really show is that there is a slight, but measurable difference in the "good" quality capacitors, versus the stock parts.

The resistance that I'm measuring there is ESR, Equivalent Series Resistance. The "ideal" capacitor would have zero equivalent series resistance. In reality all caps have some; Better caps have less. This resistance causes a capacitor to behave like a capacitor and a resistor in series. It wastes a little power, but more importantly as far as sonics go it "slows down" the cap by making it take longer to charge and discharge.

Don't try to take too much from those graphs. I just sent them to Trey because I personally found them interesting and I figured he might as well. We don't hear measurements, and there's too many factors involved to say what effect the differences will have on the sound. What I can say with confidence is that his crossovers now have better parts, with lower tolerances so that the crossovers are more true to the original design and more closely matched with one another. That should be a good thing and should pay dividends in sound quality.

I enjoyed working on Sid's crossovers. I sent them back to him today and I'm anxious to hear what he thinks.

Jason

audiobliss

Wow; thanks for the explanation.

Airplay355

I'm sure he will be outside waiting for the UPS man.

VR3

Speaking of UPS...

I got a buttload of foam pads in today...

If anyone wants to argue with me about egg crate. vs. PE acoustic egg crate, fire away... the density is twice as much, different material, and much much different than egg crate - period, end. Cheap stuff, that looks good...looks good indeed...

And the spikes PE sells comes in a nice box too... got some vinyl wrap too...

Also Jason, will let you - and everyone know about changes, etc..

michael_w

Wow I wasn't expecting that was much of a difference in look than the stock xover... When I get some spare time I'd love to learn how to do stuff like that. Lookin good Sid and jcaut!

VR3

The odd ball thing was...

This is NOT as expensive mod. I believe the parts were like 40-50 dollars for both speakers. (correct?)

jcaut

Total parts cost, including the shipping, was $54.80. That's using the Dayton polypropylene caps from Partsexpress, throughtout, one film and foil bypass cap, and Mills resistors for the tweeter padding. I had to combine two resistors to get the correct value, so there's actually $14 worth of resistors there.

But, no, a cap and resistor swap, on the original board is not necessarily expensive. Inductors can get pricey, if you change them out, and then you usually can't use the original board. You can spend as much as you like on capacitors..., You can upgrade posts, new wire, etc.. So it could get expensive.

I feel like the Dayton caps we used are on the same level as the Solen caps, for a tad less money. You can go up from there, but it's my opinion that getting a little better than that costs a lot more. If you're working on a budget, you have to keep these things in perspective.

Jason

VR3

I got them plugged up and been playing for a few hours now...

But silly me, I installed one backards... (gotta plug it up from the front instead of the back) - I'll do it over when I finish my enclosure rebuilds, no reason to do all that mess again...

But anyways, I am impressed, but I will listen more (alot more) before I comment...

Jason is a solid polky, and he knows ALOT about crossovers, and he did a great job on my xovers..

VR3

Hmm...

First Impressions are a must so I can compare notes later on my thoughts I guess...

I dunno if caps burn in or not (don't really care)

But anyway...

I dunno if its been my 2 weeks full of mediocre speakers at work, or if I am really hearing a difference. But - to my memory, it does indeed sound different. For the better.

HOWEVER, I do have a slight problem with the change, it sounds larger... infact, almost to large for my room... the vocals are at a much higher height (nothing about the placement has changed) - the instruments are much larger sounding...everything just seems 'magnified'...

Now, this would be awesome in a larger room, but in a 10.5x10.5x8 area - it isnt that desireable (to me) - but it is neat.

Another thing, it dosnt seem as 'stressed' at higher volumes, seems as if it is at the same point as before, just with much more control and precision...not on its last leg in other words...

The high end is the biggest difference, and it should be - it is, infact completely different than before. And one should note that it does indeed sound different. The instrument's clarity and detail seems much richer, more real mind you...

The soundstage seems to be much deeper and 3-D than before as well, coming along with the 'larger' sounding ordeal, I like 3-D, but the eating the room thing I dont particular care for. But that is a semi-good thing, as it should even out in a larger room...

Anyways, Ill post more after more listening and evaluating...

I know some people wanted to know what I thought, and that is my first impressions.

audiobliss

Originally posted by Vr3MxStyler2k3
I know some people wanted to know what I thought

WHO would wanna know that?!?!?!?!

VR3

yo momma (JK)