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View Full Version : Need crossover for LE14A, LE20, LE5-2



krandle37
01-22-2017, 12:16 PM
I need help to construct a crossover for the following drivers. Can someone give me the schematics for a crossover? I can build but I cannot design a crossover.

I also will be constructing a new cabinet. Do you recommend a ported or sealed enclosure and any dimensions?

In advance, thank you for any guidance.

krandle37
01-22-2017, 06:58 PM
I reviewed Troels Gravesen's website. I think I can use his cross over for LE20 and the LE5-2. Please confirm that this is correct or if I need something else.

What crossover do I need for the LE14A?

Earl K
01-23-2017, 05:38 AM
Interesting Project! Should be fun! ;)

As classic a combination that these older components are, I don't believe there's an actual off-the-shelf network for you to copy.

You'll have to get by with a bit of a kludge-up ( & all the compromises that follow along ).

I would think that the 240ti network (http://manuals.harman.com/JBL/HOM/Technical%20Sheet/240Ti%20ts.pdf) represents the best starting point for you ( with perhaps a couple of mods made by ear ).

I would add a variable LPad ( or maybe fixed ) to both the le20 and that le5 ( right before each driver ) > assuming the use of the 240t network.
- Adding that Lpad ( for the uhf ) means eliminating resistors R6-R9 & S1 .
- Adding the pads allow them to also work as impedance equalizers ( ie; Zobel, assuming some attenuation gets dialed in ).

You can certainly ( as you have mentioned ) try blending in Troels redesign of (the L100 network), with the le5 & le20. (http://www.troelsgravesen.dk/JBL_L100.htm#4310 Speaker)
- You'll need to pay attention to the polarities of the various components since I see that in the 240 network all components are wired for positive polarity ( while Troels flipped the woofer in relation to the other components ) .
- He's already accounted for the impedance curve ( in his redesign ) & lost some efficiency, so the variable Lpads will be of no use ( so, don't include them if you decide to use Troels L26mod, network ).

Having some measurement capability will help your blending process .

Do you have any?

Earl K
01-23-2017, 05:54 AM
Box Size & Tuning ?

The le14a has always worked well in a 3 to 3.5 cu' , vented enclosure ( net volume ) tuned to @ 30 to 32 hz .

WinISD (http://www.linearteam.dk/?pageid=winisdpro) will give you ducted-port sizes .

:)

PS; Remember your le5 mid will need its own sub-enclosure so that it's isolated from the le14's back-wave ( to avoid I.M. distortion ).
- The volume of this sub-enclosure has to be accounted for in your overall box volume .

http://www.troelsgravesen.dk/JBL-L26-3way_files/L26_01.jpg (http://www.troelsgravesen.dk/JBL-L26-3way.htm)

krandle37
01-23-2017, 04:21 PM
Hi Earl, Thank you for the advice on the enclosure and crossover. I would like to stick with Troels crossover for the mid and tweeter since he has gone to the trouble of flattening out the frequency between the drivers. From what I see, I am missing the crossover for the woofer. The 240ti Network seems to be a whole new challenge since the tweeter and mid are different drivers from the ones I am going to use.

From Troels frequency graphs, can you give me an idea of what crossover for the LE14A? I do not know how to determine this with my limited knowledge of circuitry and lack of testing devices. Once designed, what item in this LF crossover would get modified to fine tune the proper roll off? Or, is it the mid crossover that gets modified with a fixed LF rolloff?

Earl K
01-24-2017, 05:07 AM
Hi Earl, Thank you for the advice on the enclosure and crossover. I would like to stick with Troels crossover for the mid and tweeter since he has gone to the trouble of flattening out the frequency between the drivers. From what I see, I am missing the crossover for the woofer. The 240ti Network seems to be a whole new challenge since the tweeter and mid are different drivers from the ones I am going to use.

From Troels frequency graphs, can you give me an idea of what crossover for the LE14A? I do not know how to determine this with my limited knowledge of circuitry and lack of testing devices. Once designed, what item in this LF crossover would get modified to fine tune the proper roll off? Or, is it the mid crossover that gets modified with a fixed LF rolloff?

I've just reviewed Troels network design for his 3-way L26 & feel it's not quite "general-purpose" enough to use with your mids & tweeters.
- It has some very frequency specific LCR impedance EQs for the le5-12 ( calculated at 350hz ) which won't work as intended with your le5-2s ( since your's more than likely have a higher Fs at @ 450hz ).
- Here are Troels own measurements for four le5-2's.

http://www.troelsgravesen.dk/JBL_L100_files/A_imp_all_LE5-2_plus12dB_L100cab.jpg

Alternately, here's a thread on the L71 Verona (http://www.audioheritage.org/vbulletin/showthread.php?22937-Any-members-here-own-the-L71-Verona) for you to read.

Its network is something much more basic ( based on the L100 ) . There are two variants ( the L71 (http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L71%20ts.pdf) and the L71A (http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L71A%20ts.pdf).)

It wouldn't be a bad idea to start your project by using on of these two networks ( I'd probably go with the L71A version ).
- With the components you have on hand, you'd be then building a 4310/L100 with a larger woofer ( much like the Verona, which used a 15" woofer ).

These ( L100 variants ) are fun to listen to ( with a pretty forward all-cone sound ).
- Its a great way to get some audio memory before using a more refined network and get going on your project.
- All the components can be recycled into other networks ( meaning the expense isn't a dead loss when you want to upgrade to a custom network ).

Troels design by contrast, ( the only one with published LC values ) uses drivers that are different enough from yours to create pause ( they are newer generations with smoother responses ).

Here's a comparison of the ( le5-12 ) mid driver that he used vs what you have on hand.

http://www.troelsgravesen.dk/JBL-L26-3way_files/LE5-12vsLE5-2.jpg
The tweeters ( le20 vs le25 ) are compared here! (http://www.troelsgravesen.dk/JBL_LE20-25.htm)
- One can see that the le25 handily outperforms the le20 in bandwidth ( also in distortion specs ).
http://www.troelsgravesen.dk/JBL_LE20-25_files/LE20_1-2_0.25mtfb_-34.4dB_flush.jpg
http://www.troelsgravesen.dk/JBL_LE20-25_files/LE25-1-2_0.25mtfb_LE26-inv-faceplate.jpg
It needs to be stressed again, that anything you cobble together here is a lash-up of sorts.

If that unpredictability troubles you, sell what you currently have and then re-assemble a collection of the exact parts used by Troels in his designs ( & redesigns ).
- That would mean acquiring ( at bare minimum ) a pair of le5-12 mids and a pair of le25 ( or le26 ) tweeters.

:)