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Jbl l80 t to l80t3 crossover change

craig h

craig h

Active Member
I have a set of l80t that I have restored. They have the same upper end "shouting" that I had with the L100T that I traded a friend for.. I had a pair of l100t3 crossovers from a pair I bought new but the cabinets were wrecked in storage I put them in the 100t and they suddenly had that beautiful sound I remember. My question is, is there any easy way to change the values on the l80t crossover to t3 because I just can't seem to find any t3 for sale. I tried putting my 4410a crossovers in, lengthened the ports and added extra padding but although better they are lacking in clarity and detail compared to the t3 l100 that I have. Thanks
 
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Welcome, Craig! You can compare the two schematics here:

http://mail.audiokarma.net/forums/showthread.php?p=2659880#post2659880 Here's what I see, at a glance:

L1 goes from 2.2mH to 3.0mH.

R1 (39 ohms) gets replaced by R1 and R2 in parallel (82 ohms each)

C3 goes from 17uF to 9uF

L2 goes from 0.5mH to 0.6mH

R2 (now R3) goes from 3.9 ohms to 2.5 ohms

C5 goes from 14uF to 9uF

L3 goes from 1.0mH to 0.80mH

C7 goes from 3uF to 4uF

R4 (now R5) goes from 1.2 ohms to 4 ohms

Except for adding the new R2, it looks like the circuit is the same, so you'd just drop in the new bits and wire R3 on top of or next to R2, in parallel.

That's just what I see at a glance, though. You'd have to check each part to confirm.

Since it wouldn't be a bad idea to replace those cheap resistors and the old caps anyway, you'd really only be spending "extra" money on the coils and a resistor.

I would think about removing the old coils and testing their DC resistance with an ohmmeter. I think on Parts Express, when coil shopping, under the specs they may state the DCR of the coils. You could then look for a coil with about the same DCR as the originals, since I bet the T and T3 coils had similar gauges and DCRs.
 
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l80t to l80t3 crossover change.

Thank you Zonker. I compared the schematics and appreciate your step by step breakdown Have you ever tried a conversion? I'll get the parts and do one and compare it to the stock l80. Hope this works as I have three 100t crossovers that I would love to change over too. Right now I'm listening to a pair of 4312a that I saved from the dump. Looks like someone threw them . I repaired the cracks and actually repaired one 035tia that had a broken thread wire.I have fixed 3 of them to date. The 4312a had aftermarket woofers so I put in a pair of 123a3 as I couldn't get 2213h that fit in my fix it budget. The cabinets look decent now and they sound awsome. Run through yamcx800u with m70amp playing vinyl and FM on my yam tx1000u. Starting to get too many JBLs. Can anyone have too many? Thanks again, Craig
 
Happy to help! Also, the PC boards are probably well-marked as to each bit.

A man can never have too many JBLs. My dream house has a room full of them; one of each model from the 1970s, all on various pedestals like a showroom.

I rebuilt some L80Ts and installed the T3 crossovers in them, but I never played them with the original crossovers. My son has them now and they sound great. Thread here: http://www.audiokarma.org/forums/showthread.php?p=6216187#post6216187 I have no converted one crossover to the other type. I still have the L80T crossovers in my garage.

Kudos on fixing those tweeters. I broke two and on eBay got a third broken one; the wire on all three was too thin for me to fix, so they're also all sitting in my garage now. (Along with one L80T midrange and two L80T woofers; man, did that project go sideways.)

... 4312s in the trash. :eek:
 
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jbl l80t to l80t3 crossover change

Trying to fix them as you probably know is a real bear. I carefully pull up the paper film and locate the break in the wire. I use a powerful magnifying glass. The tiny wire is tough to get a bit of solder on. I have used a strand of speaker wire and after many attempts usually succeed in soldering them together. Then I put a small piece of monster tape back down over it and screw the diaphram back down. Don't know if these wires just break or burn out but it is quite common. The finished product is of course not factory original but I just can't stand a nice tweeter sitting in my garage that looks great but no sound comes out. I scooped up a mint pair of black 4312B on cl last year for 200 bucks but just can't get myself to use them much because I want to keep them near new. Silly, huh? However that beat up pair I fixed look OK and sound great so they are out in the mix and I don't have to worry about them getting a little dings or or scratches. I just located a pair of 118h woofers to finish up my old l56 that I am giving my son and I just restored a pair of l36 that look and sound good. I also bought a pair of pioneer hpm 60 cabinets for a buck, painted them black, covered the extra spaces and mounted 127h 104h2 and 035ti in them with my 4410a crossovers. Sound good but eventually would like the 4410a cabinets for better imaging. Also have that pair of 100t cabinets with t3 crossovers. Have always loved the l100t3 since I bought a new pair in 89. Well I guess I just like bringing them back to life because I love the JBL sound. I think I have too many hobbies but listening to quality stereo sound is one of the most rewarding. Thanks again Zonk.
 
I have a pair of L80t's, and I know I'm the odd one, but I purchased a pair of L80t3 crossovers, and yanked them in short order and replaced them back with the original crossovers, and that's how they still are today.
 
OK, that's it. I'm going to put them back together with the stock l80t crossovers. I originally only played them for a minute after the refoam and just figured that they would need the upgrade because man the t3 crossovers really make a big difference in sound quality to me in my l100t. Since I've never owned l80t before I should give them a little more time. What I did was try my 4410a crossovers in there but something is missing. Maybe because the l80t is a bigger cabinet? Or perhaps I was hoping for a custom sounding musical wonder speaker. I'll give it a go but at the same time I will continue studying on the crossover upgrade. Thanks for the input 89.
 
Better positioning changed those speakers dramatically. I used to find the a touch hot in the upper end in a smaller room, and also near the rear wall, but simply using them in a larger room and pulling them out about 3 feet from the side walls, and about 5 feet from the rear wall turned them into an entirely different, and much better sounding speaker.

Even if you can't leave them out that far permanently, you can put them in a more room friendly sport when you're done critical listening.
 
My impression of the L80t: Decent speaker for its time, a little thin on the bottom end. My original thought in reading this thread is to make subtle changes in tonality via EQ, and that this approach might be easier, but it can take the fun out of the hobby for sure. Never tried the T3 crossover so I don't know on this.
 
Zonker92 said:
Welcome, Craig! You can compare the two schematics here:

http://mail.audiokarma.net/forums/showthread.php?p=2659880#post2659880 Here's what I see, at a glance:

L1 goes from 2.2mH to 3.0mH. (Try to determine wire size and use similar)

R1 (39 ohms) gets replaced by R1 and R2 in parallel (82 ohms each)

C3 goes from 17uF to 9uF (replace with new Polyproylene, same voltage value or at least 50-100V)

L2 goes from 0.5mH to 0.6mH (replace with new, or maybe use excess or solder on new magnet wire leads and wind around the original core, measure)

R2 (now R3) goes from 3.9 ohms to 2.5 ohms

C5 goes from 14uF to 9uF (replace with new Polyproylene, same voltage value or at least 50-100V)

L3 goes from 1.0mH to 0.80mH (you might consider unwinding this slightly until you have the right value, assuming you have an inductance meter)

C7 goes from 3uF to 4uF (replace with new Polyproylene, same voltage value or at least 50-100V) or you could add a 1uf in parallel

R4 (now R5) goes from 1.2 ohms to 4 ohms

Except for adding the new R2, it looks like the circuit is the same, so you'd just drop in the new bits and wire R3 on top of or next to R2, in parallel.

That's just what I see at a glance, though. You'd have to check each part to confirm.

Since it wouldn't be a bad idea to replace those cheap resistors and the old caps anyway, you'd really only be spending "extra" money on the coils and a resistor.

I would think about removing the old coils and testing their DC resistance with an ohmmeter. I think on Parts Express, when coil shopping, under the specs they may state the DCR of the coils. You could then look for a coil with about the same DCR as the originals, since I bet the T and T3 coils had similar gauges and DCRs.
Click to expand...

My comments in bold. Double check the L80T3 schematic for resistor wattage sizes and be sure they are used in any replacement resistors.
 
Well for starters while talking to someone at the parts store I was told that putting two 82 ohm resistors in parallel as for the replacement of r1 the value would be 41 ohms and there is already a 39 ohm in place and was told that the difference is minuscule. Divide the product of the resistor values by their sum. 82x82=6724 divided by 82+82=164 6724 divided by 164=41 Now I'm wondering if r1 can be left as is. I'll keep studying.
 
Zonker92 said:
Good point. (Although I guess JBL found some improvement in doing so.) Dunno. Maybe they were doing it to improve power handling? If so, a decent Mills 40-ohm 12 watt resistor should serve:

http://www.soniccraft.com/mills_resistors.htm
Click to expand...

I think this is the answer, improved power handling and maybe easy to do if they already have the parts on hand for other projects. I agree, the difference between 39 and 41 ohms is miniscule, especially since the resistors are probably 10% tolerance anyway!
 
mech986 said:
I think this is the answer, improved power handling and maybe easy to do if they already have the parts on hand for other projects. I agree, the difference between 39 and 41 ohms is miniscule, especially since the resistors are probably 10% tolerance anyway!
Click to expand...

The other thing that the two resistors do in parallel besides handle more current is they greatly reduce the inductance of the resistors. It's hard to imagine that it would be a big deal but that is basically MILLS claim to to fame. Would one MILLS 39 Ohm resistor perform better than two cement wire wound 82 Ohm resistors as far as inductance goes?

Inductance in parallel
1/LT = 1/L1 + 1/L2 .... + 1/LN
 
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the shouty problem is mainly of mids high cutoff inductance coil and resistance. Inductance should be winded up 30 more turns and resistance to 3-4 ohm. semi-sealing them with socks filled with drinking straws fixes the boomy 50hz lump.
 
salvador.gol said:
the shouty problem is mainly of mids high cutoff inductance coil and resistance. Inductance should be winded up 30 more turns and resistance to 3-4 ohm. semi-sealing them with socks filled with drinking straws fixes the boomy 50hz lump.
Click to expand...

Explain this in a little more detail, please.

- Michael
 
The less the frecuency the more air needed to be displaced."Traped" air in cabinet balances and restores woofer from moving out to much air. Cut by halfs drinking straws, make a bunch of them just that fits speaker port, put them into a sock and gently seal it. Air stills flows out but with a bit of resistance. The more resistance needed put on another sock to add more resistance. let your ears decide.
 
salvador.gol said:
The less the frecuency the more air needed to be displaced."Traped" air in cabinet balances and restores woofer from moving out to much air. Cut by halfs drinking straws, make a bunch of them just that fits speaker port, put them into a sock and gently seal it. Air stills flows out but with a bit of resistance. The more resistance needed put on another sock to add more resistance. let your ears decide.
Click to expand...

Do you have pics?

:worthless
 
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