custom 3-way JBL sounding really off!

[tuyen]

Hi guys,

I picked up this vintage custom built 3-way JBL speaker thinking it would sound amazing, but after refoaming the woofers, hooked them up and the sound is so 'midrangey' and just sounds really off in general. The drivers comprise of a JBL 124A Signature, JBL LE85 with horn + lens and JBL 077 slot tweeter. There's a custom built 2-way crossover inside (using Solen caps and inductors) that splits the woofer to the midrange horn, then there is a JBL N8000 crossover box for the tweeter.

My thinking was to rip all the crossover out and run the whole thing actively with something like a Behringer DCX2496, but that can make the system quite complex/messy?

Would there be any crossover circuits out there that would be suitable for this driver combo?

Some photos of the bits attached.

Thanks in advance for any tips guys! :)

I was hoping the speaker would sound like this!
http://youtu.be/iZRsgejPL9Y

[macaroonie]

Could be you put the woofs back in out of phase with the mid/ tops or also poss one of the woofs is out of phase with the other. Worth checking. The older JBL drivers were +ve at the black terminal.

Might be a plan to sketch up the wiring as you have it so the x perts can have a shufty.

[Mr. Widget]

I was hoping the speaker would sound like this!
http://youtu.be/iZRsgejPL9YSince I've never visited Japan or Kenji's listening room, I have no idea what "this" sounds like. That said, since both the LE85s and the 077s via the N8000 have L-pads, you should be able to turn them down to match the low sensitivity of your woofers.

Please realize the LE85 on one of those "fog horns" do tend to be a bit pronounced in the mids, but then the bookshelf monitors that appear to be playing in the video are also quite pronounced in the mids.

None of this is to say you don't need help with your networks or checking woofer phase as suggested by Macaroonie... but work with only one speaker first, try turning the LE85 down to virtually off and bring it up just a notch... then do the same with the tweeter.


BTW: Those are very nice looking DIY speakers!


Widget

[tuyen]

Thanks macaroonie and Widget!

Oh, I totally didn't think about the polarity. I know that they are matching though (ie. both sides I plugged the green into -ve and red into +ve of the woofers). Good chance that I have them the wrong way around. I will try swapping the polarities around tonight and report back!

I have tried playing around with the L-pads, but still can't get it to sound right.

But yeah, I know the sound of horns.. I run a 5-way horn system as my main system :)

[Mostlydiy]

I believe they would sound more like the L300 than the 4311 since they utalize most of the L300 drivers. They sure look good but I bet they have a hard time competing with your 5way goto system :)

/Mostly

[tuyen]

Yep, I am hoping it sounds like a L300! Not as strong impact as it only runs a 12" instead of a 15" on the L300.

Very well built cabinets on this one. about 30KG each speaker!


Can't wait to get home from work to switch the polarities around on the woofer and have another listen.


PS. /Mostly did you msg me on some other forum re GOTO horns?

[tuyen]

Ahh, I had the wires into the woofer hooked up the wrong way! I had just assumed red = +ve. But took a look at the wires going into the mid and tweeter and green wire was going to +ve of the driver and red into -ve!

I have now rectified this issue and the sound is more better now.


The next thing I'm stuck on is, I think this speaker was initially designed as a 2-way (hence the custom 2-way passive crossover), then later on the user wanted to add the tweeter into the mix, so just ended up wiring the N8000 box ontop of the signal going into the midhorn driver. But because the midhorn is more sensitive than the tweeter, I can't seem to get the tweeter response to play level with the midhorn. IE. as I turn the midhorn down, the tweeter response drops as well (even though the tweeter l-pad is on max).

Is there a simple thing I can do to make the tweeter independent of the midhorn? or maybe add a fixed resistance onto the midhorn driver to lower it to match the tweeter?


Cheers guys,
Tuyen

[4313B]

The 124A/H was an option with the LX300 network, as was the LE14A/H. The LX300 network was identical in function to the N300/N333 used in the L300 and the 3133 used in the 4333.

http://www.lansingheritage.org/images/jbl/catalogs/1979-comp/page08.jpg

Another option could be trying the Nelson Pass network for the L300 and attenuating the LE85 and 077 an additional two to three dB for use with the 124A/H.

[tuyen]

Thank you kindly 4313B.

I was just looking at the Nelson Pass L300 3-way passive circuit. Looks straight forward enough to build.

When you say 'attenuating the LE85 and 077 an additional two to three dB for use with the 124A/H', do you mean that I should be adding something extra to the circuit? Or is that the function of the l-pads shown on there already?


Cheers,
Tuyen

[4313B]

Thank you kindly 4313B.

I was just looking at the Nelson Pass L300 3-way passive circuit. Looks straight forward enough to build.

When you say 'attenuating the LE85 and 077 an additional two to three dB for use with the 124A/H', do you mean that I should be adding something extra to the circuit? Or is that the function of the l-pads shown on there already?


Cheers,
TuyenYou might be able to get away with merely turning the L-Pads down further.

[Lee in Montreal]

Seing how the original 2-way crossover was piggybacked with another crossover, I can assume you may have phase problems too. If you are into experimenting, why not disconnect the passive crossovers and use an active one? Your components are great, they currently just don't work with each others... :D

[tuyen]

Yep I will try 'activating' the speakers in the future to see what they can really do.

For the meantime, I have used Nelson Pass' modified L300 xo circuit. Sounds pretty good even in mono. But the woofer is just not sensitive enough compared to the 15" JBL 136a on the L300/4333a, so the l-pads are restricting too much of the sound. Thus I am thinking of wiring in a fixed -6db l-pad circuit on the mids and tweeters. (using 4ohm series with driver and 8ohm in parallel).

Makes sense?

http://i40.tinypic.com/231mia.jpg

[4313B]

Thus I am thinking of wiring in a fixed -6db l-pad circuit on the mids and tweeters. (using 4ohm series with driver and 8ohm in parallel).

Makes sense?Yes.

I often used a 3 dB fixed pad on the mid and high in these systems.