1.2TL crossover design question

tugboat

As some here might know, I'm about to rebuild my XOs with Sonicaps and Mills resistors. I've gather just about every thread link, schematic and picture I could find to help with the process. I now have something driving me crazy after researching.

I know that the use of Sonicaps and Mills is an upgrade in sound quality and that's the reason I'm doing it. What is bugging me is the use of the PCB all these high end components will be connected to. Wouldn't it make sense (from a sonic point) to have the components directly connected to each other instead of being routed through the PCB? Wouldn't the limited pathway through the PCB hurt the signal flow? Couldn't all the componets be attached to a bread board, thier connections passed through and connected/soldered? Would this provide a better signal path? I know it would allow better layout of the much larger components.

Just wondering

Thanks!

Face

Yes, there would be a sonic benefit to it, I recently did this with my Tannoy HPD's. It cleaned up the highs a bit and overall detail increased slightly. But, most of the improvement may have been from removing the L-Pads from the signal path.

Before:



After(preliminary version):

tugboat

That's pretty cool.

I know the use of the PCB is for mass production. All my speakers from the 60s and 70s were hand wired crossovers. Caps were usually soldered inline with the speaker leads as were the chokes.

Of course, Polk probably took into account the PCBs affect on the signal and might have compensated for it. Hmmm.....

awe-d-o-file

and will not be using the PC boards. I am going to do point on point wiring on a large board, as large as will fit on the SDA metal mounting plate. I will also be deleting the molex type connectors although some have said this will not yield a benefit. I believe it will. I also plan on drilling holes and wire tying down components onto size cut deflex pads for anti-vibration. I will also be using the bypass caps and putting a switch on the outside of the front metal panel so they can be used or bypassed as some have had different opinions on their result. No money right now for the upgrade.

F1nut

So, you think that getting rid of the PCB's and the molex connectors will clean things up, but installing a switch for the bypass caps is a good idea? Save yourself the trouble, not to mention mucking up the crossover plate, the bypass caps are not needed and result in a whole lot of bad sound.

tugboat

F1nut wrote: »

the bypass caps are not needed and result in a whole lot of bad sound.

So do you think it a good idea to remove bypass caps whenever found? For instance, I want to recap my RT800s and looking at the schematics they have bypass caps as well.

Thanks

F1nut

It depends. If you are upgrading the original electrolytic and/or mylar caps to film/foil caps, then bypass caps are no longer needed.

tugboat

F1nut wrote: »

It depends. If you are upgrading the original electrolytic and/or mylar caps to film/foil caps, then bypass caps are no longer needed.

Cool. That's what I plan on doing (Sonicaps).

Thanks again

zingo

Feel free to include the bypass cap in your upgrade, but most of us who have done it in the past ended up pulling it because it sounded weird. The new caps that most people are using are of such a high quality that a bypass is no loner necessary.

ben62670

EF the bypass. You are running lower power to them so not so bad, but when you get an amp you will not want BP caps. Plus 1 to what Jake said.
Ben

tugboat

zingo wrote: »

Feel free to include the bypass cap in your upgrade, but most of us who have done it in the past ended up pulling it because it sounded weird. The new caps that most people are using are of such a high quality that a bypass is no loner necessary.

I'm going to be using Sonicaps for my CSi5, RT800 and (maybe) my LS f/x after my 1.2TLs are done next week. I'll leave the bypass caps out of all of them.

Gonna do a seach for more information on exactly what a bypass cap does and why it's used.

Thanks!

ben62670

tugboat wrote: »

I'm going to be using Sonicaps for my CSi5, RT800 and (maybe) my LS f/x after my 1.2TLs are done next week. I'll leave the bypass caps out of all of them.

Gonna do a seach for more information on exactly what a bypass cap does and why it's used.

Thanks!

Bypass caps IMHO let lower frequencies through in a smaller degree. I am not a total expert. Most of us regurgitate what we have heard on PF, but those that have tried both say...
Ben

F1nut

Here's an article that comments on bypass caps......near the bottom.

http://www.10audio.com/sonicap_oimp_multicap.htm

zingo

That's a great article Jesse and thanks for reposting it.

tugboat

F1nut wrote: »

Here's an article that comments on bypass caps......near the bottom.

http://www.10audio.com/sonicap_oimp_multicap.htm

Thanks. I know understand a bit more about what they are supposed to do. So far no person or other source recommends keeping them.

I read in a thread here about having to use a jumper for one of the bypass caps I'll be removing, but I can't seem to find it. When I try to search using more than a single word, the search engine finds nothing.

Do you remember, off the top of your head, where the jumper went? Or am I confusing that with something else?

tugboat

Oh, and I know I'm being a pain asking so many questions. Just don't want to mess this up. I've replaced a small cap here and there, but they were just drop in replacements. I've not tackled anything of this magnitude before.

I really appreciate everyone being so patient and helping.

zingo

Are you using the schematics when doing to mod? It helped me when I first started because I could reference on paper where everything went or needed to go.

Using a jumper to bypass the bypass cap just means placing a wire in place of where the cap was. Just desolder and remove the bypass cap, and solder a plain wire in it's place.

tugboat

zingo wrote: »

Are you using the schematics when doing to mod? It helped me when I first started because I could reference on paper where everything went or needed to go.

Using a jumper to bypass the bypass cap just means placing a wire in place of where the cap was. Just desolder and remove the bypass cap, and solder a plain wire in it's place.

I do have the schematics. As for the jumper, that's my main issue. I recall reading that you just leave one of them out (no jumper replacement) and you jumper for the other one.

I'm attaching a pic I saved from a thread here (credit to whomever I borrowed this pic from). If you look at the bypass caps, one is in the same area as the poly switch and a 12uf cap. Both caps connect to the larger section, so if I just remove the bypass cap, won't the signal path still be in place? The other bypass cap isn't so clear to me. Seems to be connected on one side to a jumper and 12uf cap. The jumper comes from the same section of the PCB as the other bypass cap.

I'm sure I'll figure it out eventually.

Face

You're correct, you only need a jumper to replace the poly switches.

tugboat

Face wrote: »

You're correct, you only need a jumper to replace the poly switches.

That's starting to make more sense to me. Must be what I read. I found the other picture that threw me off. If you look at it, this board doesn't have the 12uf cap going into the hole next to P3 like the unmodified board does. This also makes it easier to see that there is also a factory jumper going from R2 to the hole next to P3.

Well I've printed out the schematics and am about to measure the opening for the XO. With this info I'll be able to figure out the biggest XO board I can make and how to lay out the componets. The caps should arrive tomorrow and I hope to get started right away and be done by Sunday.

Oh, and credit to any and all whos pictures I use.

tugboat

Okay, another question. As I was trying to outline the new XO board layout, I noticed something looking at the attached picture. I've circled four things on the tweeter ouput side (in blue). One is the bypass cap, one is a jumper, one is the 22.5ohm resistor and the other is the 12uf cap. Now the jumper needs to stay as it provides the signal for the 12uf cap. But what about the 22.5 resistor? Once I remove the bypass cap, the link to the 22.5 resistor is broken. The 12uf cap goes directly from the jumpered section to the tweeter output.

Now also looking at the picture and schematics... The schematics show that all the caps and resistors are on the negative leads (for tweeter output), but the picture is marked with "+" for each output connected to a cap/resistor/inductor. The schematics show pin one of the output connector as being positive.

Thanks!

awe-d-o-file

F1nut wrote: »

So, you think that getting rid of the PCB's and the molex connectors will clean things up, but installing a switch for the bypass caps is a good idea? Save yourself the trouble, not to mention mucking up the crossover plate, the bypass caps are not needed and result in a whole lot of bad sound.

The more I read the more I won't fool with the bypass caps. Also I forgot there are three so no way. The switch was just an easy way to compare and could be deleted later. Also you can't get exact values anyway and most say don't bother using them with good film caps. You and I have disagreed before on the Molex connectors. They aren't good when new much less almost 20 years later. A big board with point to point wiring and good damping of the parts will also allow plenty of room for direct wire. Going from three connections to one is a good thing. Shun me all you want but I'm doing it.

tugboat

awe-d-o-file wrote: »

The more I read the more I won't fool with the bypass caps. Also I forgot there are three so no way. The switch was just an easy way to compare and could be deleted later. Also you can't get exact values anyway and most say don't bother using them with good film caps. You and I have disagreed before on the Molex connectors. They aren't good when new much less almost 20 years later. A big board with point to point wiring and good damping of the parts will also allow plenty of room for direct wire. Going from three connections to one is a good thing. Shun me all you want but I'm doing it.

Looking at the way the tweeters are wired on my 1.2TLs, I should be able to get rid of three connections. All four + connections go directly to the - input post. This means all four can be combined into one.

I'm looking for a good quallity connector. Actually, three connectors. I do want to keep the input separate from the outputs. For the mids I'm looking for a 4 connector, highs a 5 connector and input a 5 connector. I'm looking at the possibility of using weather pack connectors with higher conductive connections inside. Although, stock they would still provide as good or better connection than the molex. That and they'd be sealed from corrosion.

F1nut

awe-d-o-file wrote: »

You and I have disagreed before on the Molex connectors. They aren't good when new much less almost 20 years later. A big board with point to point wiring and good damping of the parts will also allow plenty of room for direct wire. Going from three connections to one is a good thing. Shun me all you want but I'm doing it.

I wasn't condemning your choice to remove the Molex's, although I don't feel there is any benefit. Rather, I was commenting on your choice to use bypass caps.

As for the Molex connections, a little Deoxit and Pro Gold and mine are happy.

No shunning from me.

Ricardo

tugboat wrote: »

That's starting to make more sense to me. Must be what I read. I found the other picture that threw me off. If you look at it, this board doesn't have the 12uf cap going into the hole next to P3 like the unmodified board does. This also makes it easier to see that there is also a factory jumper going from R2 to the hole next to P3.

Well I've printed out the schematics and am about to measure the opening for the XO. With this info I'll be able to figure out the biggest XO board I can make and how to lay out the componets. The caps should arrive tomorrow and I hope to get started right away and be done by Sunday.

[/COLOR][/B]

tugboat wrote: »

Okay, another question. As I was trying to outline the new XO board layout, I noticed something looking at the attached picture. I've circled four things on the tweeter ouput side (in blue). One is the bypass cap, one is a jumper, one is the 22.5ohm resistor and the other is the 12uf cap. Now the jumper needs to stay as it provides the signal for the 12uf cap. But what about the 22.5 resistor? Once I remove the bypass cap, the link to the 22.5 resistor is broken. The 12uf cap goes directly from the jumpered section to the tweeter output.

Those are my pictures (The original labeled ones, top and bottom).

You are correct in your observations:

My board is missing the jumper from R2 to P3, and has the 12uf cap connected directly into P3. When I did this I had no "model", and didn't notice it, but it seems someone made a mistake when assembling this board originally. The way it is layed out, the bypass and 22.5 ohm resistor are not doing anything for that 12 uF cap.

I'd suggest you look at yours, and I am sure it will have that jumper from R2 to P3.

tugboat wrote: »

Now also looking at the picture and schematics... The schematics show that all the caps and resistors are on the negative leads (for tweeter output), but the picture is marked with "+" for each output connected to a cap/resistor/inductor. The schematics show pin one of the output connector as being positive.

Thanks!

Yes, when I labeled these I just followed the (-) and (+) from the input pins. If you look at the schematics, the negative input in the tweeter section "magically" turns into to the (+) outputs, and vice versa. If you plan to modify/change the connectors, just make sure you leave things as they are.

tugboat

Ricardo wrote: »

Those are my pictures (The original labeled ones, top and bottom).

You are correct in your observations:

My board is missing the jumper from R2 to P3, and has the 12uf cap connected directly into P3. When I did this I had no "model", and didn't notice it, but it seems someone made a mistake when assembling this board originally. The way it is layed out, the bypass and 22.5 ohm resistor are not doing anything for that 12 uF cap.

I'd suggest you look at yours, and I am sure it will have that jumper from R2 to P3.




Yes, when I labeled these I just followed the (-) and (+) from the input pins. If you look at the schematics, the negative input in the tweeter section "magically" turns into to the (+) outputs, and vice versa. If you plan to modify/change the connectors, just make sure you leave things as they are.

Thanks, that explains alot. However, in the picture where you label each pin for the input, pin 2 and 3 are reversed, as are the labels for the driver's output. Pin 2 should be (-) and pin 3 (+) on the input. If you look at the picture and schematics for the driver's output, the large 16mH inductor is connected to pin 1 of the output, which is negative. In the picture it's marked as positive. Also, while the pins for the tweeter input are correct, the ouput pins should be reversed. The (-) input actually goes to the (+) of the tweeters. Guess it doesn't matter too much unless you're going to replace the connections as well.

Anyway, these pics have be a great help to me. Thanks for taking the time to take them and document your work. Can't tell you how much time they're gonna save me.

Ricardo

tugboat wrote: »

Thanks, that explains alot. However, in the picture where you label each pin for the input, pin 2 and 3 are reversed, as are the labels for the driver's output. Pin 2 should be (-) and pin 3 (+) on the input. If you look at the picture and schematics for the driver's output, the large 16mH inductor is connected to pin 1 of the output, which is negative. In the picture it's marked as positive. Also, while the pins for the tweeter input are correct, the ouput pins should be reversed. The (-) input actually goes to the (+) of the tweeters. Guess it doesn't matter too much unless you're going to replace the connections as well.

Anyway, these pics have be a great help to me. Thanks for taking the time to take them and document your work. Can't tell you how much time they're gonna save me.

You are right again; I reversed the polarities in the low frequency part of the diagram; I guess I was not paying attention.

Have fun with your project; you'll be very happy with the results.

tugboat

Ricardo wrote: »

You are right again; I reversed the polarities in the low frequency part of the diagram; I guess I was not paying attention.

Have fun with your project; you'll be very happy with the results.

Well according to UPS tracking, my new caps and resistors are on the truck for delivery! Once they get here I'm off the the local electronics store (not frys, but a real electronics shop). I'm going to get some shrink tube for the leads and resistors. Things might get so tight that a short is possible if something shifts.

Wish me luck!

F1nut

Do not put shrink tubing on the resistors, nor hot glue. They get hot and need airspace to help dissipate the heat.

tugboat

F1nut wrote: »

Do not put shrink tubing on the resistors, nor hot glue. They get hot and need airspace to help dissipate the heat.

Should have mentioned that the tubing is only for the leads and not the actual resistor. Do you think the leads will get too hot for the shrink tubing? If so, how about nylon type sleeving? I'm not sure exactly what it's called, but I've seen it on leads and wires routed in and around heat producing components.

Thanks!

tugboat

Ricardo wrote: »

Those are my pictures (The original labeled ones, top and bottom).

You are correct in your observations:

My board is missing the jumper from R2 to P3, and has the 12uf cap connected directly into P3. When I did this I had no "model", and didn't notice it, but it seems someone made a mistake when assembling this board originally. The way it is layed out, the bypass and 22.5 ohm resistor are not doing anything for that 12 uF cap.

I'd suggest you look at yours, and I am sure it will have that jumper from R2 to P3.




Yes, when I labeled these I just followed the (-) and (+) from the input pins. If you look at the schematics, the negative input in the tweeter section "magically" turns into to the (+) outputs, and vice versa. If you plan to modify/change the connectors, just make sure you leave things as they are.

I have the same setup as you. The bypass and 22.5 resistor go nowhere. They are connected to a section that has no other components or connections. My 12uf is connected directly to the output connection as well w/out a jumper. What I'm wondering is if this 22.5ohm is meant for the bypass only. Even with the jumper, the resistor wouldn't be in series with the 12uf like all the other outputs.

Hopefully someone here will chime in.

Thanks