Any Thoughts on these Stripped Down L250 / N250 Crossover Drawings?

[Zonker92]

OK, submitted for anyone's comments are my first crude attempt, using Powerpoint, to draft a basic schematic* for the L250 without pads and without bypass caps, in the zero dB position for each driver. I still need to check again (for the third time) all the values and connections, but please point out any errors you see.

Here is the stock schematic. (http://www.audioheritage.org/vbulletin/showthread.php?31337-Recapping-L250s-Need-Schematic&p=316100&viewfull=1#post316100)

My thought was to upgrade the caps (at least those in the signal path), and dispense with bypass caps. I really don't use the bus bar attenuators. I might also put the woofer on a separate set of terminals so I can bi-amp them or bridge them as I choose. So I figured it would be easier just to build new crossovers from scratch, than to hack up the stockers. I would mount these on boards in the cabinets, where the stock boards normally sit.

(*Yes, I know I didn't use the conventional symbols, so this is not a real schematic, but please humor me.)

http://i1021.photobucket.com/albums/af333/Zonker92/Audio%20-%20Video/N250CrossoverWithoutPads-FirstDraft.jpg

Then here is the same drawing, except with the woofer circuit the same as the 250Ti (sans pads and bypass caps). Can anyone comment on why the woofer circuit was changed? I see the crossover point remained unchanged at 400 Hz. Would it be a good idea to adopt these changes? (I assume using the entire L250Ti crossover design is a bad idea, without going to 104Hs and 044Tis at the same time.)

http://i1021.photobucket.com/albums/af333/Zonker92/Audio%20-%20Video/N250CrossoverWithoutPads-with250TichangestoWooferonly-1.jpg

I'm not throwing out these drawings so much to debate the issue of bypass caps, although my mind remains open to using them; I'm more curious to see whether (a) anyone finds any mistakes or problems in these drawings; and (b) whether I should incorporate any of the 240Ti design changes, even if I keep my stock L250 drivers.

And hey, what's with the jumper at L3 on the schematic I linked above?

Thanks!

[JeffW]

I've never built them, but I think the bypass caps are kind of important. Even to the point where different material yields different sound characteristics, regardless of the main cap qualities.

There's threads around here someplace documenting it. But they're not that much more $$ and can just be jumpered onto the main cap leads. If I was going to all the trouble to rebuild crossovers, I'd sure put them in there. Actually, I'd probably charge couple the caps if I was going to all the trouble of building new crossovers, so adding bypass caps is chump change in comparison.

[Zonker92]

I've never built them, but I think the bypass caps are kind of important. Even to the point where different material yields different sound characteristics, regardless of the main cap qualities.

There's threads around here someplace documenting it. But they're not that much more $$ and can just be jumpered onto the main cap leads. If I was going to all the trouble to rebuild crossovers, I'd sure put them in there. Actually, I'd probably charge couple the caps if I was going to all the trouble of building new crossovers, so adding bypass caps is chump change in comparison.

Thanks, Jeff. I may use bypass caps. I was thinking of leaving them out because some people who are deeply into caps, like Troels Gravesen, suggest that if you use good caps in the first place, bypasses may not be necessary. Charge coupling would almost double my cost, I think; I believe I'd have to double up all the cap calues. :eek: But if anyone has any suggestions there, I'd be curious to hear them.

[Robh3606]

Here's a simplified version I used to look at the voltage drives in LEAP

Rob:)

[Zonker92]

Dude! You are my hero! Huge thanks!

My question now is whether it's safe and advisable to use the new and improved 250Ti circuit designs for the LE14H-1 and 108H, and the L250 design for the LE5-11 and 044-1, assuming I keep the original L250 low-pass (1.6mH) on the 108H so it crosses over properly to the midrange?

At that point, I believe the only issue would be whether the output levels on the woofer and midrange were unchanged from the L250 such that they continued to work properly with the upper drivers. I think they would be the same as before, since as far as I can tell the woofer output should be the same (it has no resistors in the signal path), and if the woofer output is unchanged, Greg Timbers must have left the 108H the same to keep them on the same level, I would think. Plus, both speakers are rated at 90 dB efficiency, suggesting that the driver output is the same top to bottom for both models.

Unfortunately, the schematic for the N250Ti is missing the value for the far-right resistor on the 108H ... ???

Hey: I just found this freeware for schematic design: http://www.expresspcb.com/expresspcbhtm/download.htm Cool beans.

[Allanvh5150]

Hi, just in case you have not finished you project, bypass caps are there to cancel the inductance, yes you heard right, of the capacitor. Regardless of how good the capacitor may be. A very small cap will do the job, usually 0.01uf.

Allan.

[Zonker92]

Hi, just in case you have not finished you project, bypass caps are there to cancel the inductance, yes you heard right, of the capacitor. Regardless of how good the capacitor may be. A very small cap will do the job, usually 0.01uf.

Allan.


I hadn't heard that about their function; that's interesting. I wound up with 250Tis and I'm recapping them, using .01 Audiocap Thetas for every bypass cap. I should finish up this week. I used Jantzen Silvers for the tweeters, Superiors for the mids and Claritycaps for the lower mids. The shunts have Jantzen Standards and Solens.

Thanks for the tip!