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4313B
10-09-2004, 10:32 AM
Capacitors, inductors and resistors for building biased 250Ti networks.
All the components are from Solen.
Original L250 networks are at the top of the photo and will be used as templates.

Earl K
10-09-2004, 11:03 AM
Cool !

What about bypass caps ?

Who's the supplier of the laminate-core? inductor ?


<> EarlK

steveh
10-09-2004, 03:04 PM
Trying to find some information on the 250 series speakers. What is the difference between the "250 Ti Classics" and the "250 Ti Jubilee's"? Did one preceed the other in the 250 lifecycle? I understand that one of these models came with a charge coupled crossover, does anyone know which one that would be? What would a pair of "250 Ti Classics" in piano black lacquer, mint condition with original boxes be worth. Thank you for entertaining my questions.

4313B
10-09-2004, 03:19 PM
"What about bypass caps ?"

Undecided.

"Who's the supplier of the laminate-core? inductor ?"

Erse.

Earl K
10-09-2004, 04:43 PM
Hi Steve

Here's what I found in "trying to find information on 250 series speakers" (http://audioheritage.csdco.com/vbulletin/search.php?s=&action=showresults&searchid=107199&sortby=lastpost&sortorder=descending) . That search was called "250 Jubilee". One of its threads has 3 different pdf files for the 3 models sold in North America. These "tech-sheets" show you the different parts along with the crossover schematics. To my knowldege, there is no available tech-sheet for the 250 Jubilee. It wasn't sold in North America .

Here's another couple of hits after using the search engine to look for "250 lacquer" (http://audioheritage.csdco.com/vbulletin/search.php?s=&action=showresults&searchid=107201&sortby=lastpost&sortorder=descending)


Prices : eBay Germany apparently sells a lot of 250(s) per month. That's a good place to start - to get a value .

<. EarlK

steveh
10-09-2004, 05:51 PM
Earl,
Thanks for the information. Couldn't find exactly what I was looking for in the links that you provided. Reason for my questions, I have the opportunity to acquire a pair of 250 Ti Classics that were purchased and are currently in South America. I don't seem to be able to find much information on the "Classic" series. I have read in earlier posts provided by Giskard that some of the later production model 250's (Ti's,) came from the factory with "biased or charge coupled crossovers) and was trying to determine if this particular pair came with such. Do you know (or anyone else) if the 250 Ti Classics were available in the U.S.? If anyone has any information to share, on this model, it would be appreciated. Thanks in advance for any info.

Earl K
10-10-2004, 05:21 AM
Hi Steve

You're the first to mention this ( Classic ) variant .

It would be nice to know what model tweeter and midrange was in this 250 variant.

More up to date crossovers can always be built - as per the first post in this thread .

<> Earl K

steveh
10-11-2004, 11:11 AM
Earl,
Thanks for the additional information. I also have not been able to find information with regards to the "Classic" 250 Ti's. On the backs of the speakers are engraved brass plaques about 3 1/2 by 5 inches that say "250 Ti Classic, manufactured by JBL - Northridge California". I will get some digital photos posted as soon as I can. These were purchased new in Santiago, Chile so perhaps they were not available for the domestic market? They really are quite beautiful in the black (lacquer?) finish and are in pristine condition. Thanks again.

Steve

Earl K
10-11-2004, 11:33 AM
Hi Steve


These were purchased new in Santiago, Chile so perhaps they were not available for the domestic market?

Giskard is the expert on 250(s) around here. In an earlier thread he mentioned which 250 variants were released to the North American market. It does appear these "Classics" were a special off-shore release.

If you are going to take pictures, also include a pic of the crossover/plate/terminal connector area , found in the back.

As I earlier mentioned, the tweeter and upper midrange maybe unknown to the North American market - so - closeups up these parts would be helpful .

I'm guessing you don't yet own these 250(s) ? If and when you do - you might want to remove the above mentioned crossover - take a pic and post it. Look for a 9 volt battery in this crossover . If there is one then the crossover is DC biased ( Charge-Coupled ) .

regards <> EarlK :)

steveh
10-11-2004, 03:21 PM
Trying to figure out how to post some digitals but have the driver lineup, which is as follows; 035TlA-2, 104H, 108H, and LE14H-1's. Also, printed on the crossover (exterior) is; "Internally wired with MONSTER CABLE". Will include digitals of the crossovers.

4313B
10-27-2004, 06:02 AM
Obviously the new parts are considerably bigger in size than the stock parts. It is very easy to see why G.T. at JBL firmly suggested starting from "scratch" instead of trying the "retrofit" method which he labored through.

It looks like one solution would be to separate out the low pass, mount it on a separate board, and place that board on the bottom of the enclosure.

Two more considerations - this pair of biased N250Ti's will have the option for bi-wiring so a second pair of input terminals and bar straps will have to fit in the 3 x 5 cutout and there has to be room for mounting a battery. The battery will probably have to go in the larger cutout where the bar straps are located.

Jakob
10-28-2004, 04:57 AM
Giskard,

Am I right in assuming You are building a pair of biased networks for your 250tis? If that is the case, will you continue to post your progress in this thread with a lot of pictures and step by step information regarding the building? I would appreciate that a lot, and I think other 250 owners would as well.

B.R!

4313B
10-28-2004, 05:14 AM
Hi Jakob,

I planned on posting pictures and such. I suppose I should measure all the parts and draw them up so I can manipulate them on a computer. I'll think about that...

4313B
01-21-2005, 11:52 AM
Here are some photos courtest of jblnut. He will be replacing his stock N250 networks with biased N250Ti networks. :)

L250 250Ti bias biased charge-couple charge-coupled

jblnut
01-21-2005, 01:43 PM
Here are some photos courtest of jblnut. He will be replacing those stock N250 networks with biased N250Ti networks someday. :)



Yes, one day in the not too distant future I hope to replace my old N250 networks with something a bit more current. It would seem that there might be a correlation between between this thread and that activity :p .

Methinks the cat has finally left the bag...

jblnut

4313B
04-10-2005, 02:55 PM
Giskard,

Am I right in assuming You are building a pair of biased networks for your 250tis? If that is the case, will you continue to post your progress in this thread with a lot of pictures and step by step information regarding the building? I would appreciate that a lot, and I think other 250 owners would as well.

B.R!Things just didn't work out quite like I had envisioned. I did get a few pictures but then my digital went analog and that was the end of the photo shoot. :banghead:

A picture of the double tiered masonite boards and the 250Ti back template. I ended up going with 1" standoffs instead of 2". I also ended up mounting alot of the components on top the second tier instead of sandwiched between the tiers.

4313B
04-10-2005, 03:00 PM
Rustoleum paint - hammered finish
I believe these are the original 1/4" taps for the bus bars.
I think I ended up going with 1/2".

4313B
04-10-2005, 03:03 PM
Front and back of boards.

4313B
04-10-2005, 03:16 PM
The rest of the pictures are courtesy of jblnut.

Inside of L250 with stock network again:

4313B
04-10-2005, 03:17 PM
Inside of L250 with biased 250Ti network.

4313B
04-10-2005, 03:18 PM
Low pass section separated out.

4313B
04-10-2005, 03:20 PM
Side view showing extensive resistor pads. Bias resistors are mounted on the underneath of the second tier and can't be seen without taking the tiers apart.

4313B
04-10-2005, 03:22 PM
Back view installed. Battery not hooked up yet. That hammered finish is shiny!

Those bus bars are all level, they just don't look like it in the picture. :p

Mr. Widget
04-10-2005, 05:08 PM
:thmbsup: :applaud: :thmbsup:

Beautiful work!!!!

Widget

rek50
04-10-2005, 05:16 PM
Excellent Craftsmanship. The bends look like they were made with a tubing bender. The added insulation is a Nice touch. The layout looks CNC. Positive connections, blah :blah: I don't have to tell you, as you know already, but I must say: Attention to detail is the difference between superiority and mediocrity. Those are super. I'm a tradesman (tool/die/mold maker) and have worked with/along various trades. Your work displays many skills. Thanks for taking the time to share.

4313B
04-11-2005, 09:07 AM
Thank you! :)

Regis
04-11-2005, 04:47 PM
With a great writeup, excellent before-and-after pics and just superb craftsmanship. The new networks look like they'd blow away the old ones. The crossovers do make a diff and I'm looking forward to a test of what the new sounds like vs. the old.

Thanks!
http://audioheritage.org/vbulletin/images/smilies/applaud.gif

Regis
04-11-2005, 04:50 PM
Gotta ask. Reviewed the pics again and there was a 9V battery there! What does it do? Inquiring minds wanna know!

4313B
04-11-2005, 05:45 PM
Hi Regis,

The battery charges the capacitors. You can read about it here - Bypassed and Biased Capacitors (http://audioheritage.csdco.com/vbulletin/showthread.php?t=3555) in the biased portion of the thread.

jblnut
04-11-2005, 06:23 PM
Hi Regis,

The thread that has the reviews and the history behind this whole project is below. I started the thread two years ago and it's officially done (for me at least) now. As you can see, I did finally relent and decide to pursue upgrades although I was very happy with the L250's as they were.
And the solution was - as Giskard predicted - charge coupled networks. Custom, bi-wireable, adjustable charge-coupled networks actually :applaud: ...

http://www.audioheritage.org/vbulletin/showthread.php?t=289

jblnut



With a great writeup, excellent before-and-after pics and just superb craftsmanship. The new networks look like they'd blow away the old ones. The crossovers do make a diff and I'm looking forward to a test of what the new sounds like vs. the old.

Thanks!
http://audioheritage.org/vbulletin/images/smilies/applaud.gif

Regis
04-12-2005, 07:02 AM
OK, I understand now, the JBL literature gracefully explained the reasoning behind conjugate circuits (level the impedance out throughout a speakers range) and the bypass caps (allow fast transients through smaller caps without the delay of charging the bigger ones, thus affecting the music). I'll bet the battery is for "pre-charging" the big caps to a certain static or preset level to get rid of the charge-up time period. Am I correct in assuming this?

Don C
04-12-2005, 08:07 AM
Tha capacitors charge and discharge in a non linear rate as they cross the 0 volt level. This is called hysteresis, and it causes distortion of the signal. By charging them with a battery, they remain biased to above 0 volts, never crossing, and this eliminates that diistortion.

4313B
04-12-2005, 08:15 AM
Some people claim to be able to hear the negative effects of the battery in the circuit. Fortunately my hearing isn't that good so I can enjoy the positive benefits of biasing without any of the negative benefits. :applaud:

JBLnsince1959
04-12-2005, 08:27 AM
I have a question. Do the caps like Mundorf with their double windings also get rid of hysteresis and if so does it do it better than the charge coupled, or are we talking about two different things here?

Regis
04-12-2005, 09:30 AM
Tha capacitors charge and discharge in a non linear rate as they cross the 0 volt level. This is called hysteresis, and it causes distortion of the signal. By charging them with a battery, they remain biased to above 0 volts, never crossing, and this eliminates that diistortion.

OK, I get that part, but does an input signal being a sine wave and going from positive to negative voltage, still react to in a linear fashion with the cap biased above (or +) zero volts? I'm thinking sinewave crossing from positive to negative and back again across the zero volt level. If the cap being positively charged behaves differently than a non-charged cap, than I'll accept that, I'm just not sure I understand the mechanics of it with a sinewave input going through it. Or is it a current related issue?

Don C
04-12-2005, 12:18 PM
OK, I get that part, but does an input signal being a sine wave and going from positive to negative voltage, still react to in a linear fashion with the cap biased above (or +) zero volts? I'm thinking sinewave crossing from positive to negative and back again across the zero volt level. If the cap being positively charged behaves differently than a non-charged cap, than I'll accept that, I'm just not sure I understand the mechanics of it with a sinewave input going through it. Or is it a current related issue?
I'm not sure that I understand your question, but I'll make an attempt. The whole idea, as I understand it, is to make the capacitors react in a linear fashion. The caps pass AC signal (music) while blocking the DC component,(from the battery) so the DC bias does not appear at the input to be seen by the amplifier nor is it passed to the speakers. The only place that the DC bias is seen is right at the capacitor where it is applied. It does not affect the AC part of the signal passing through the cap, except to make the output look more like the input than would normally be possible.

Regis
04-12-2005, 01:38 PM
Thanks for the excellent explanation. I definitely have a better understanding and from the links to Techbots workup on Bypass caps, I'm going to be modifying the L-150 X-overs again.

Jakob
04-15-2005, 01:29 AM
Giskard,

Your pictures of the networks makes me wanna get right to building a pair of my own. Really awesome! Have You auditioned them yet?
Will You also post a network layout?

Regards: Jakob

MJC
04-15-2005, 07:20 AM
Great looking network. Now I am going to have to redo my L212 networks, the ones I did 2 year ago don't look THAT neat, or charged coupled.

4313B
04-15-2005, 08:53 AM
Giskard,

Will You also post a network layout?I'd have to think about that. The whole endeavor didn't go as planned. The thread was going to be fancy and the networks were going to be fancy. In the end I redid the networks a second time basically from scratch with a more utilitarian perspective and I didn't take nearly as many pictures or notes as originally planned.

4313B
04-15-2005, 08:55 AM
Great looking network. Now I am going to have to redo my L212 networks, the ones I did 2 year ago don't look THAT neat, or charged coupled.Could I talk you into trying a modified 3113B network before you go to the trouble? Would you care to A/B a pair of those networks with your stock N212 networks and see which you prefer?

MJC
04-16-2005, 08:21 AM
Could I talk you into trying a modified 3113B network before you go to the trouble? Would you care to A/B a pair of those networks with your stock N212 networks and see which you prefer?

I'm for trying anything that will improve an already great speaker.

Actually, I might have as many as 3 different networks overall in the 7 L212s.
The 3 I built have bypass caps, then there is the original pair and then there's the pair I bought last Sept. and they might have a different xover(haven't looked) being they have the foam inserts glued to the inside of the grille cloth that the originals don't have.

The 3 with the bypass caps are on the front and the other 4 are being used as surrounds, so I really haven't done a direct comparision. But I do know that the mirrored imaged boxes produces a better soundstage, and the bypass caps seem to make them more dynamic. I still haven't gotten any polystyrene caps for the 066, that from what I've read, should make them more airy.

FWIW, for HT, more subs are better. I'm using 3 12" subs, connected via speaker wire, to the center and side surrounds and the pair of 1500s connected to the HK 635 subout. I only use the 1500s when listening to music.

4313B
04-16-2005, 08:26 AM
Ok, PM me with your address and I'll get a pair of old 3113B networks out to you to try. They aren't charge coupled (we can talk about that later) so you should be able to get a decent idea how they compare with the stock N212 networks.

My only reason for suggesting this is because I think the 3113B or N96/N112/N150A do a bit better on DVD/LaserDisc playback than the N212 or N110A networks do.


FWIW, for HT, more subs are better.Agreed.

Jakob
04-23-2005, 02:07 AM
I'd have to think about that. The whole endeavor didn't go as planned. The thread was going to be fancy and the networks were going to be fancy. In the end I redid the networks a second time basically from scratch with a more utilitarian perspective and I didn't take nearly as many pictures or notes as originally planned.

Please, pretty please!!! It would spare me and others a great amount of time and work. I think they look great, and the design really deserve to get spread via the forum.

Thanks: Jakob

JuniorJBL
09-29-2005, 07:52 AM
How do the new networks compare to the old?
As soon as my shop is done, This will be one of my first projects "Changing from L250's to 250Ti's":bouncy:
Shane




The thread that has the reviews and the history behind this whole project is below. I started the thread two years ago and it's officially done (for me at least) now. As you can see, I did finally relent and decide to pursue upgrades although I was very happy with the L250's as they were.
And the solution was - as Giskard predicted - charge coupled networks. Custom, bi-wireable, adjustable charge-coupled networks actually :applaud: ...

http://www.audioheritage.org/vbulletin/showthread.php?t=289

jblnut

jblnut
09-30-2005, 12:54 PM
Every free second I get I still run to the 2-channel room to spin some vinyl. I'm used to the sound now so I can't give a lot of useful comparison info. I think my earlier posts are better in that regard.

all I can say is that there was plenty of room for improvement in those old L250 xovers...

jblnut


How do the new networks compare to the old?
As soon as my shop is done, This will be one of my first projects "Changing from L250's to 250Ti's":bouncy:
Shane

MJC
09-30-2005, 07:31 PM
Every free second I get I still run to the 2-channel room to spin some vinyl. I'm used to the sound now so I can't give a lot of useful comparison info. I think my earlier posts are better in that regard.

all I can say is that there was plenty of room for improvement in those old L250 xovers...

jblnut

I jump back and forth, as to wheather I like 2 channel, or multi-channel music best. Both being done on my L212 system. But at this time my vinyl just sits. I need to get a phono pre-amp to connect to my H/K AVR 635, or my Marantz 880 and L55s.
Do you know where I can buy one?

jblnut
10-01-2005, 06:47 AM
I jump back and forth, as to wheather I like 2 channel, or multi-channel music best. Both being done on my L212 system. But at this time my vinyl just sits. I need to get a phono pre-amp to connect to my H/K AVR 635, or my Marantz 880 and L55s.
Do you know where I can buy one?

Sure - just about anywhere. Ebay, audiogon, craiglist, your local audio shop, etc. I'd recommend doing some web research and reading before you purchase. You can spend $20 or $2000 - it all depends on just far into the vinyl realm you want to go...

jblnut

louped garouv
10-01-2005, 07:46 AM
Do you know where I can buy one?

http://www.needledoctor.com/s.nl/c.ACCT106601/sc.2/category.401/.f

Titanium Dome
10-01-2005, 07:57 AM
It's so obvious in this case: www.phonopreamps.com

These folks give you many choices at decent prices. You'll need to scroll down past the Paypal info, then you'll see a lot of choices.

Of course you can Google other sources with "phono preamp" and find $200 to $1500 units if you prefer. ;)

JuniorJBL
12-29-2005, 12:33 PM
Would you say that cc'ing the crossovers is a better way to go or would you suggest using better caps (or bypassing or both). I was reading the thread from Ian about his endeavors with cc'ing and see he has found some differances between the two. Also what would be your thought about having the crossover outside the cab? I would like your input as you have worked with the 250's alot.
Thanks
Shane

4313B
12-29-2005, 12:59 PM
I like the idea of crossovers outside the enclosures.

I, meaning me, would charge couple the N250Ti instead of spending huge sums of money on really expensive capacitors.

Examine the 40 uF series capacitor on the 108H, the 10 uF series capacitor on the 104H, and the 2.7 uF series capacitor on the 044Ti.

Solen:
PB270 = $1.89
PB1000 = $4.02
PB3900 = $10.44

Solen Biased:
PB510 = $2.54 + PB560 = $2.64 = $5.18
PB2000 = $5.75 + PB2000 = $5.75 = $11.50
PB7500 = $17.07 + PB8200 = $18.32 = $35.39

Sonicap:
2.7 uF = $8.00
10.0 uF = $17.60
20.0 uF = $27.25 + 20.0 uF = $27.25 = $54.50
And now Sonic Craft is saying all those Sonicaps were GEN I and should probably be bypassed with GEN II caps so add $4.60 for each 0.01 uF you add to each main capacitor.

The Sonicap is a revolutionary product! How is it revolutionary? It redefines the price-to-performance ratio for "audio capacitors". The Sonicap is the "entry level" of its design. However, the design is world class! The Sonicap will yield or exceed the performance found in the most prestigious of boutique caps, yet with a price conducive to that of "entry level".

Sonicap Biased:
Um, I'm bored now and want to do something else instead of adding that all up.

BTW, as Ian pointed out, Sonicraft has greatly expanded their offerings. - http://www.soniccraft.com/products/capacitors/film.htm - Their stuff is good and Jeff can be helpful if so inclined.

Unfortunately for you, you will have to make the determination yourself.

JuniorJBL
12-29-2005, 01:22 PM
I think I will go for the crossovers outside the box (think outside the bun:blink: )
Maybe I will try some of the solen-biased first. This should keep the cost of the crossover lower. This way I will have some sort of a baseline for changing/upgrading in the future.
Thanks again for your input.:)

4313B
12-29-2005, 02:57 PM
This way I will have some sort of a baseline for changing/upgrading in the future.Good idea. You should be able to build the networks so it is real easy to slip different capacitor types in and out.

JuniorJBL
01-20-2006, 12:42 PM
those cc'd networks, It looks like you still kept the autotransformer. Is this the case for all LMF/MF/UHF?

4313B
01-20-2006, 02:38 PM
What autotransformer? The L250 had one but the 250Ti did not.

JuniorJBL
01-20-2006, 03:31 PM
I'm sorry I ment the tapped coils:o:

Edit: Sorry I just found this http://www.audioheritage.org/vbulletin/attachment.php?s=&postid=2306

I had not seen this before.

My Bad :o:

4313B
01-20-2006, 04:24 PM
It looks like I will be building another pair of biased 250Ti networks after all.

lcsteve
04-11-2006, 01:59 AM
I wish to change mine to a biased network but have difficulty in removing the lower rear panel to access the crossover boards. I had unscrew all screws but it appears that the panel remain unmovable even applying some pressure to remove it. I don't want to damage the woodwork. Is the lower (big) panel stick to the box or for any other reasons? Alternatively, can I have access via the front by removing the bass speaker? Any suggestions appreciated.

4313B
04-11-2006, 04:03 AM
I finished the last pair of biased 1984 style N250Ti networks I'll ever build last night.

You remove the LE14H-1 and then unbolt the N250Ti from the back and bring it out through the LE14H-1 mounting hole.

spkrman57
04-11-2006, 07:35 AM
With all those parts you are purchasing.

Since I bought jblnut's old 250 crossovers I am still looking to breadboard the drivers before building the L250 enclosures.

I am starting on the basics first and then will upgrade when time and $$$ allows!

Ron

lcsteve
04-12-2006, 01:20 AM
I'll give it a try as recommended. Thanks for your advice.:)

jblnut
04-12-2006, 06:26 PM
Hmm..where have I heard that before...

:)

I think you could probably sell all of these you wanted to, if that was your intent. Who convinced you to do this again, or should I say what ?

Glad you didn't break the mold - these are too good to have all to myself. Can't wait to hear what the new owner thinks !

jblnut





I finished the last pair of biased 1984 style N250Ti networks I'll ever build last night.

You remove the LE14H-1 and then unbolt the N250Ti from the back and bring it out through the LE14H-1 mounting hole.

4313B
04-12-2006, 06:45 PM
Actually I did break the mold so you do have a unique pair.

I think you could probably sell all of these you wanted to, if that was your intent.These were my last.
Who convinced you to do this again, or should I say what ?A very nice lady said "Please?". Otherwise it never would have happened.