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gerard
06-19-2005, 10:30 AM
Hello

Does anyone has a xpl200 crossover schematic .
I intend to use an xpl200 crossover on my 250txxxx clone I am building right now ( cut the wood yesterday ) .

I need to see the difference on the components ....

Gerard

johnaec
06-19-2005, 10:41 AM
Link courtesy og Giskard: http://manuals.harman.com/JBL/HOM/Technical%20Sheet/XPL200a%20ts.pdf

John

gerard
06-21-2005, 06:03 PM
hello

Schematic xpl200 :
Did i read c1=75 uf on bass

On 250 ti bq itis only 24 uf ?

Is there some expalnation for quite the same Hp ?

Thank's for comment .

Gerard

Zilch
06-21-2005, 07:24 PM
XPL200A is a two-pole filter. The 24 uF in the single-pole 250Ti is in a Zobel conjugate, not the LP. XPL200A has no Zobel:

gerard
06-22-2005, 06:26 AM
oK


If the speaker are moreless the same why should there is one xover with Mr Zobel and one not ?

Just would like to understand what will happen if I use the xpl200 Xover on the 250 speaker ( I am a novice .... )

Gerard

Zilch
06-22-2005, 11:11 AM
Let's think this through:

Generally speaking, the impedance of an uncompensated (no Zobel) woofer rises with increasing frequency.

For any given filter inductance, the crossover frequency increases with rising impedance.

Thus, it may be seen that, without a Zobel, the rolloff is flattened above the design frequency, and a first-order filter with a Zobel may perform similarly to a second-order filter without one, depending upon the filter frequency and impedance characteristic of the driver.

It's likely better to compensate for the driver's impedance characteristic rather than rely upon it, in filter design, as it is thermally sensitive. In either case, it must be considered. In this respect, at least, the 250Ti is the "better" design.

I'm a neophyte at this, too, just trying to make sense of it. Fortunately, when I'm WAY wrong, others here take sufficient offense to set me straight.

:p

gerard
06-22-2005, 11:57 AM
Zilch ,


Thank you and may I ask more questions ?

1. If the 250 Ti xover is better why Jbl would use such a design for a newer model ?

2. Would the Xpl200 would work anyway on a 250Ti design knowing those little difference !.

Regards

Gerard

Zilch
06-22-2005, 12:34 PM
1. 75 uF = $16.05, 25 uF = $5.90. Other considerations, such as actual performance in the total system, may prevail.

2. All else being equal, yes, very likely. I've only examined LF, tho.

3. Giskard knows these crossovers in and out. Alas, he's on sabbatical just now.... :(

gerard
06-22-2005, 02:36 PM
Ok Zilch ;)


I Go on my project and hope to finish the spakers next month .....
Then I may come back to you after the first test !!!!

Regards

Gerard

Earl K
06-22-2005, 04:05 PM
Hi Gerard,

Regarding your L250 wannabes ;

- What components are you planning on using ?

- Do you still intend on using your le8t(s) in place of the originals' 108H ?

- If so, you must design a custom crossover to properly integrate that full-range driver with the others. Don't expect the N250 or N200XPL to hit the "nail on the head" if you are making driver substitutions. A "plug & play" approach will definately be the wrong approach ( if not using the original components ).

- Also, you should experiment with some sealed test boxes for those le8(s). You need to determine the best internal box size / so that the network filters aren't having to fight some strange box bump or slump. Acquire some Box Tuning SIM software to help you with this process . WinISD comes to mind as a freebee.

- I'd recommend you do this necessary R & D before cutting more wood parts . Also get an inexpensive RTA ( with test mic ) to help you get started. Behringer comes to mind as one hardware based choice.
TrueAudios' TrueRTA is a software based solution / if you can meet the soundcard requirements ( you'll still need a test mic ) .

:cheers:

Guido
06-22-2005, 04:12 PM
Nice Spice plots Zilch ;)

DavidF
06-22-2005, 04:24 PM
I have some suggestions following on Zilch’s and Earl's comments above. I would like also to look at the response curves and the impedance curves to try to confirm what the design goal might be with the filters.

I think that the LE14 has a fairly flat response where the 2214 woofer has a rising response with increasing frequency. No doubt by design, the 250 network is trying to maintain a slow, consistent 6dB/octave rolloff on the LE14 woofer. Since the rolloff is extended well out in frequency, it will certainly be effected by the driver's impedance rise. I would expect a conjugate to diminish the effect of the rising impedance and provide a nice rolloff close to the predicted rolloff. One interesting thing about this circuit is the 6mH coil. That is high in value for a cutoff around 300-400. I suspect this is to provide a more tapered-down response in the upper bass/lower mids to flatten the power response, but this a guess. At some point the LE14 rolloff must increase beyond 6dB per octave due to the driver’s natural rolloff combined with the electrical filter, but perhaps this comes well after the xover transition and does not need to be considered.

So with the 2214H, if I am correct on the rising frequency response, we may have an added factor to consider. The coil value seems close to the textbook for a L-R second order, but still a little high. The cap value definitely seems high over the textbook model value. I suggest that the high-value of this cap would be to change the Q of the filter effect, accelerate the response rolloff, either to compensate for the rising response or to work with the coil to provide a tapered response out to the desired "knee" of the crossover and then modify the rolloff effect more towards 12dB per octave. Either way, I suspect that the 12 dB rolloff at this low frequency would not be significantly effected by the rising woofer impedance and therefore a conjugate is not needed.

As to swapping the crossover of the 250ti with that of the XPL, I am certain that it will sound different and almost as certain that it will not sound better. Consider that tweaking a production model in which professional designers have spent a vast amount of time and effort to call their best is always a bit ambitious. Small changes can be made to alter the response to suit taste, but swapping the entire crossover on a 4-way design?

DavidF

gerard
06-22-2005, 05:14 PM
OK

Very good advise , thank you so much .

I hope nobody will come angry about me about the following ...

1 ) this is my first project
2 ) I live In Morocco so it is not so easy to get parts in fact I get them in the US and ask a friend to send it to me .
3) I wanted my first project to be affordable
4) components are : le14a -le8t ( i have a pair ) - le5-5 ( could not find le5-11 and found the best was to get a le5-5 ) - 035ti
I bought the components on ebay ; le 14h was impossible to find .
Concerning the xover, 250 ti xover are hard to find and even I found that if I could find one I would have to change all caps ( old products over 20 years , caps are dead !!! ) and this would cost 250.00 $ (ebay+new caps ).
I found xpl Xover at a cheap price and I decided to go on .

If the result are good :blink: i can always change some components and make a complete new xover but I found it would not be the best to build one without having something to compare and no knowledge .

Concerning the box size , the idea is very good to make some R&D but i have to start from something may be some or less absorbant material inside fiberglass will change something !

May be I can build a bigger box for the le8t with wall inside to reduce or upgrade the internal size ?????

I know the 250 range are difficult and I may better go on a 4425 systems .
Well I have 434x so I wanted to test a 250 system .
If it does not work , I will have some nice ( I hope ) wood cabinet to look at ...

I am anyway optimistic , My first dog I had 4 years ago is a rottweiller , I am still alive and we live very well together in peace .

regards

gerard

DavidF
06-22-2005, 10:13 PM
OK


I am anyway optimistic , My first dog I had 4 years ago is a rottweiller , I am still alive and we live very well together in peace .

regards

gerard

That is a very good start!



I understand your intention to work with what you have, and you are looking to start somewhere. The tweeter and the woofer are the least likely to cause deviation in your use of the XPL200 xover. The real problems, and where you will find most of your attention needed, is making the mids work.



One thing I know to expect. The LE8 is much more efficient than the driver used in the XPL200. Maybe also the LE-5 vs the dome mid. I think you will want to insert a variable lpad on both drivers.

Ian Mackenzie
06-23-2005, 12:07 AM
Depending on the spread of the crossover points, designers often spread the crossover points as a result of mutual reactance of the filters.

Therefore, values may appear large than one might anticipate but when voltage drives are measured the result is correct for the required crossover points.

The Doctor

Don C
06-23-2005, 09:45 AM
In case it helps, here is a link to some charts that I made of the XPL crossovers.

http://www.audioheritage.org/vbulletin/showthread.php?t=2444