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gerard
11-15-2004, 02:26 PM
Hello

I finally choose to build a pair of L250Ti for my first dy project .
hesitate with 4425 but ....

I would need some help ( Giskard , Earl K , Class A )

Looking at the thread and jpg : http://www.audioheritage.org/vbulletin/showthread.php?t=3590&highlight=250ti+jubilee

I need to understand the following as I do not nothing about Xover !!!.

1- Uhf shows 4 capacitor ( 2 and 2 in serial ) this makes 6.3 uf If I am not wrong ????
Why not using a 6.00 and 0.3 capacitor then ????

Is is a 18db xover , so if it is 6 ohms this shouud give about 5.5 k ? ( wrong or not ) ?

The capacitor used are 100v and it seesm godd quality are rated over 400 v ? Why 100v

As I can't find used xover or pcb , I will have to make it , so I need ti understand what I am doing .

2. Cabinet

I can't see really if there is 4 separation ( thre is black and white for separation ) .
If yes then the woofer should be in a 13.5" high cabinet
Is the woofer in a close cabinet or is there an event behind ? ( can't see really ) .

I intend to use le14H , Le8T ( because I have a pair , I may change after for 108H , Le 5 or 104H , 035Ti .

I really would appreciate some help and that you understand I am not confident with but I really want to try and succed as it will be my first Diy .

regards

Gerard

Robh3606
11-15-2004, 03:39 PM
You couldn't have picked are more challenging speaker to build on your first time out. You will be able to do it just a bit harder with the network type and finding the correct drivers.

On the networks you need to do a search for Charge Coupled and that will answer many of your guestions. To put it simply if you had a 3uf cap in series to convert it to a Charge Coupled network you would put 2 6uf in series and add a bleed resistor between the two. The resistor is about 3 megohms and is connected to a 9 volt battery.

Don't try to work out the crossover points in the network. They are not cookbook networks. Just build to the schematic and pay attention to the Inductor DCR values,

100Volts is fine I think you are confusing Watt's/Power and Voltage. Not the same thing.

The cabinet is vented out the back with a reflex port.


If you don't use the stock drivers you will be forced to change the crossovers. Try to use the originals or be prepared for changes.

Rob:)

gerard
11-16-2004, 02:12 PM
Ok Robh3606.

Sorry I did not read the thread : http://www.audioheritage.org/vbulletin/showthread.php?t=3585&highlight=biasing.


About the 100 V capacitor ,I was tryying to say that high cost caps are rated about 400-600 vdc , low cost like dayton are 100 Vdc so I was wondering if I can use those low cost dayton or 400vdc solen ????.

About the 9V on the resistor , if I get it , I need a transfo 9v dc inside the cabinet ? wright ?

Now I get everything .... Of at least something .

Just need to know for the cabinet :I can't see really if there is 4 closed separation ( there is black and white color for separation ) or if the separation are open . ( sorry english is not my mother tongue ) .

If yes then the woofer should be in a 13.5" high cabinet ...

Thank you so much for support .

Gerard

CLASS A
11-16-2004, 08:20 PM
Hello

I finally choose to build a pair of L250Ti for my first dy project .
hesitate with 4425 but ....

I would need some help ( Giskard , Earl K , Class A )

Looking at the thread and jpg : http://www.audioheritage.org/vbulletin/showthread.php?t=3590&highlight=250ti+jubilee

I need to understand the following as I do not nothing about Xover !!!.

1- Uhf shows 4 capacitor ( 2 and 2 in serial ) this makes 6.3 uf If I am not wrong ????
Why not using a 6.00 and 0.3 capacitor then ????


Is is a 18db xover , so if it is 6 ohms this shouud give about 5.5 k ? ( wrong or not ) ?

The capacitor used are 100v and it seesm godd quality are rated over 400 v ? Why 100v

As I can't find used xover or pcb , I will have to make it , so I need ti understand what I am doing .

2. Cabinet

I can't see really if there is 4 separation ( thre is black and white for separation ) .
If yes then the woofer should be in a 13.5" high cabinet
Is the woofer in a close cabinet or is there an event behind ? ( can't see really ) .

I intend to use le14H , Le8T ( because I have a pair , I may change after for 108H , Le 5 or 104H , 035Ti .

I really would appreciate some help and that you understand I am not confident with but I really want to try and succed as it will be my first Diy .

regards

Gerard
Gerard

I have just read your post, but its way too late here....I will have a look inside my speakers for you tomorrow. What else would you like to know apart from the 4 dividers.
Cheers

gerard
11-17-2004, 01:03 AM
Thank you Class A.

I have lot's of questions ....

Apart from that as you are of the one who get experiences with 250 It would be nice to get some answers for :

1. Are the side of panel made of Mdf and what thickness

2. Are the front of the panel ( whre the speakers are ) is made of plywood ? or else and what thickness .

3. What should i choose finally for the xover .

a- ) Biaised xover with cheap caps ( can I use the 100v dayton )
or should I use 250v dayton

- do I need to bypass with this biaised technology ( i didi not saw any drawings with !)


see :
http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=61
they cost about nothing !!!

for this xover

http://www.audioheritage.org/vbulletin/showthread.php?t=289&page=3&pp=15&highlight=arrogant

b) standart xover with dayton 250v and bypass dayton fiim and foil 400v

4) if I try biased xover do you use a 9v battery or a transformer 115vac-9v dc ?
If using a battery how should I know the battery is stilll ok ? .

5) why not using regular Lpad ( like the one form parts express ) instead of this pad made in the xover where you have to move a wire or piece f metal form one side to another ?

May be I ask wrong questions ? I am not sure of everything as it is my first project .

I must go to work ... bye

Gerard

Jakob
11-17-2004, 03:23 AM
Hi Gerard!

Congratulations on choosing to build the 250 ti. Every time I turn mine on, I'm astonished over the quality of their sound!

If you feel like the biased network is too much work, go for the maybe easier to build network in the original 250 ti.

In my 250 ti's, the LE14H-1 plays in the whole cabinet. The 108H and 104H plays in sub cabinets.

The walls are 18mm's (MDF I think).

Good luck and keep us updated!

gerard
11-17-2004, 04:05 AM
Jakob


Are you sure the front panel Is Mdf ?

For xover since I start from nothiing they shloud not be much wrok to do it biaied ro normal .

The only thing is : sqtandart xover I need to use by pass high quality caps

biased : it seems there is no by pass ? do i need also high quality or dayton 100 vac non polarised are enough ?
I do not know ?

regards

Earl K
11-30-2004, 05:57 PM
Hi Gerard,

I saw your post a while back about your DIY 250ti. I've been swamped with work till now - so - I hope I'm not too late to make some suggestions .

Here they are;

(a) For ease of manufacture, consider making the single cabinet type 250 into two separate cabinets. This should be much easier to design and construct . I'd still maintain the cool-looking offset trapezoidal shapes. To get the correct volume in litres for the bass section - you'll need to make it deeper than the original 250 which as mentioned , has the woofer using the entire single box minus the sub-enclosure volumes .

(b) Use the 250Ti BQ crossover as your inspiration for a crossover . It's more simplistic in the padding section and therefore ought to be easier to properly implement . It is also more closely tailored to your existing 035ti tweeters ( you do have those - yes / no ? ). Charge-Coupling a crossover is probably best left to another project. If you use decent quality components you may never feel the need to DC bias ( Charge Couple ) a crossover .

(c) Use as many of the original ( proper ) components as possible since the crossover was designed with them and only for them . Once you deviate from the given components - not many people can help you "fix" sonic problems if they arise .

So;
(i) That means using the le14h-1 and not the le14h. My info shows the le14h is about 3 db more efficient in the midband. To use this woofer ( the le14h ) would require a crossover reworking that would likely mean adding another "pole" to the crossover - negating some of the builtin transient qualities of the original design .

(ii) Use the 108h if you can get a pair . If you can't and your stuck , then use your le8t(s) only as a last resort. If I had to use le8(s) I'd explore getting a paper dust cap put on instead of the aluminum cap ( I detest aluminum dust caps and all their "wizzzy-wige" distortion ). I'd also replace the highly compliant surround for a "stiffer" foam surround. This might be easy to accomplish since, apparently most of the aftermarket replacement foam will stiffen the compliance ( and raise the Fs ) to the more appropriate midbass value ( @ 65hz ) . Once the Fs was raised - I'd likely add a bit more dampening / weight to the cone - though a heavier paper dust cap might suffice .
The 708G , 8" midbass woofer may be a viable substitute for the 108H. It's been used on JBL systems on both sides of the Atlantic.

(iii) I'd suggest using the original 104H for the upper mid or if you can't find any then look for a viable standin/ substitution for it. The 104H has a polypropylene cone which will give it a unique "voicing" compared to a treated a paper cone.
The 104h-1 or 104h-2 are paper-coned. I'd try to maintain the polycone approach FWIW. This is cone material topic is a debatable question. There are many regular contributors to this forum who have a lot of experience with the various le5 variants. I don't have this experience so I really can't add a lot to this subjective discussion.

Having said that, here's where I would look for a substitute mid;

Since you're over in Europe , you might find it easier to obtain the JBL 705G midrange. According to the info I see - this transducer has a polypropylene cone. It's used in a bunch of JBLs' top Euro designs - so hopefully it is also available for you to purchase .
The "G" designation" suggests a lower working AC impedance than the 104H - so if you get a pair there will likely be a need to rework the LC values of that "himid" section of the crossover .

(d) Capacitor Working Voltages ; ( ie, You're questions regarding JBLs' use of 100volt caps instead of the typical 400 to 600 volt rating found in the more expensive "boutique" caps )
Well
- You have properly identified an area that is a mystery to most ( including me ) and will likely continue to remain a mystery . North Creek , Hovland, and a few others ( SonicCaps ) have 100v or 250 volt ratings for the larger value caps that act in the midrange areas. I can't think ( off the top of my head ) why a more permeable dielectric film ( ie lower voltage rating ) is recommended as being "better" for larger wavelengths.


hope something here helps your project <. Earl K

gerard
12-01-2004, 03:31 AM
Earl K

Thank you so much for your valuable informations .

a) I want to stick on single cabinet , a carpenter can do the job and in Morocco it is easy ...

b) I will use finally 250ti BQ , I did not understood clearly the biwiring process but I get it now .

c) I have already le14 and le 8T so I have to use them , i just got 035ti ; the proble is for 104H and I believe this speaker is may be the most imortant piece of the 250Ti .
On ebay there is only le5 and 104H2 until now ... I have to wai . I did not found any info on 750G or on ebay germany . I have read some thread on 093ti bu t no info and did not find any on ebay ...


Any more advise on this 104H would be nice , thank's again for support .

Gerard