Jbl l80 t to l80t3 crossover change
- Thread starter craig h
- Start date
This was somewhat popular in the 80's in Europe - packing a bass reflex port with straws or other partial air passing material (socks, fiberglass, polyfill). It converts the bass reflex design with the typical resonance peak, sometimes +3db bump in the low bass to an aperiodic type vent, a resistive vent if you will which usually brings down the bump and sometimes extends the LF response at the expense of efficiency. The impedence peak will usually move to a double bump IIRC.
Works for some speakers, Zilch famously plugged ports entirely with the Zilchplugstm on some JBL speakers (original L100, L200 type cabinets, and some large single woofer cabinets with more than one vent) converting them to an acoustic suspension design.
It all depends on what you're looking for and JBL mostly designs for highest efficiency in a direct radiator design, hence the bass reflex port rather than acoustic suspension. Very few have used a resistive port (Dynaco, Dynaudio) and to some extent the IMF Transmission lines and Fried resistive lines.
Socks to hold the straws work ok but look goofy, nylons might be less obtrusive. On the L100T pictured, the port though is in back. The 2214H woofer is pretty darn good though in the L100T-T3 type cabinets. I have less experience with the L80T.
Works for some speakers, Zilch famously plugged ports entirely with the Zilchplugstm on some JBL speakers (original L100, L200 type cabinets, and some large single woofer cabinets with more than one vent) converting them to an acoustic suspension design.
It all depends on what you're looking for and JBL mostly designs for highest efficiency in a direct radiator design, hence the bass reflex port rather than acoustic suspension. Very few have used a resistive port (Dynaco, Dynaudio) and to some extent the IMF Transmission lines and Fried resistive lines.
Socks to hold the straws work ok but look goofy, nylons might be less obtrusive. On the L100T pictured, the port though is in back. The 2214H woofer is pretty darn good though in the L100T-T3 type cabinets. I have less experience with the L80T.
craig h
Active Member
Put in the caps and resistors and did not use high end parts as I want a quick comparison. Did not do the inductors as I want to add or unwind but need a meter. First impression was a toned down top and mid but still detailed . Less Bass than the T crossover. I noticed 89 grand thought the same thing. My 100t3 crossovers I put in the 100t cabs were definitely better and no bass loss. I also ran in mono one channel at a time for comparison. I think I may end up liking the mod especially for vocals much better. I'm going to quick mod the other one tomorrow and see how they image. If good I will tackle the inductors later but don't know if they will make much difference. For now it's JBL on a budget. Talkie high end is definitely smoother and mids are smoother too.
craig h
Active Member
I could not find 9uf for c3 and c5 so replaced with 10 uf NP. Left 39 ohm in place. Removed R2 and R4. Moved R2 to R4 postion as change calls for 4 ohm but this is 3.9, close. Purchased a 2.7 ohm for R4 as could not find 2.5 ohm. Changed the values on these for 5 bucks. The sound? Incredible difference and I haven't even touched the inductors. So if you don't like the squaky mid and high on your LTs try this for a cheap quick fix. I was wrong about the bass. With both done the bass is low clear and sweet. Rolls off slightly but still the best you can hope for for a ten inch woofer. Mids are smoother and highs are silkier but speakers maintain good presence. I am thoroughly surprised! Will eventually figure out how to add or subtract wire on the inductors using a meter to the proper values and will measure number of winds to take off or add to make it easier for the diy enthusiast. This may actually smooth them off even more but not sure if it's necessary. I love these speakers.I think having a powerful amp and good preamp really makes them sing and they don't need to be blasted. I'm running at 2 to 5 watts on a Yam M70. PLEASED!
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craig h
Active Member
Interesting stuff on the 100t3 crossovers. Well I listened again to my cheap mod of the l80t. Played some Spyro Gyra vinyl and this is for real. I have 4312s and l100t3 and I am starting to like these L80t2 shall we call them better. I know one should use high quality parts and change everything out but this worked. $7.10 and a half hour. I don't think that I will even touch the coils. Also the more I listened the more I am amazed at the better bass response. Thought it would be worse but it is clean and detailed and it is going down low. I can't believe the 127h are getting close to my 2214H. Excellent.Took off the port tube extensions and took out my extra insulation and left the port with no plug of any kind. I'm glad I did. Many times these cabinet mods help but this time they are better left stock. These are in a carpeted garage with many things to dampen all around. Happy listening!
craig h
Active Member
I goofed on the c7 should be in parallel. I replaced with 4cf mylar. I unwound L3 to 0.08 and soldered on and wound L2 to 0.6mh. Wound up L3 to 3.0 mh. The sound is even smoother with the beautiful t3 mid and highs but the great bass was gone. I unwound L1 and kept testing till I settled on 2.6mh. I added a bit more fiberglass stuffing to the upper back cabinet and lengthend the ports about 1.5 inches. I'm super happy with these now. T3 qualities with even more bass that is detailed and goes down low. People always say these are great "rock" speakers but to me they are great on all types of music. Using Yamaha separates and vinyl I'm blown away by the jazz fusion sound they reproduce. Separation and detail is superb and bass is now outstanding. Custom home version of the 4410a and I think even better with the bigger cabinets.
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BMWCCA
Addicted Member
I have two pair and simply refer to them as L80T/3.
My modification path was a bit simpler after finding T3 original crossovers for $16 shipped (twice now), and doing Gordon W's port and stuffing mods. Still not the speaker my L96s are but then I have less than a C-note in one pair and I'm not complaining.
My modification path was a bit simpler after finding T3 original crossovers for $16 shipped (twice now), and doing Gordon W's port and stuffing mods. Still not the speaker my L96s are but then I have less than a C-note in one pair and I'm not complaining.
craig h
Active Member
That is much easier but the t3 crosovers are hard to find and $16 was a great price. I have about that much in my mod and the fun(soldering iron burns) of diy. I would recommend unwinding L1 on your t3 to get deeper bass. This will make your speakers even better. As I said I took it from 3.0 mh down to 2.6 mh and what a difference. My yam tx1000u tuner sounds almost tube like with the bass of these speakers.