Tweaking up some L100Ts

[mech986]

Hi mech986, this is Lansing Heritage not "AK"!

Thanks, getting confused in my old age.

[danfan78]

Hi danfan, welcome to LH!

Your situation does sound perplexing, and I know you have done a lot already but let me ask some basic questions so we're all on the same page.

these L100T units were worked on by the previous owner so let's start there.
1. Do you have the correct 2214H woofers, 104H-2 midranges, and 035Ti tweeters?

2. You mentioned the PO had refoamed them. Did the work himself, or sent out? Source of foams, thin or thicker foams, and mounted front or back of cone edge? In my experience, the correct foam is a thinner foam rather than the typical mid-thickness foam used on JBL 12" drivers like the 2203, 128H and similar. The thicker foams may fit, but will not allow the 2214H to resonate or extend as low properly, and may accent the upper midbass.
Some pics here and a push or pinch test may give some idea for us.

3. is it possible the woofer was actually reconed with aftermarket parts? There should be a five digit printed number on the cone for an OEM JBL cone.

4. if the 2214H has the faston connectors, then polarity should be correct with the crossover connection as is.

5. Assuming you have the correct 104H-2 mids, do they have any dents in the center cap? I'm wondering if they got misaligned and you're hearing distortion instead of clean midrange. The 104H-2 should have a black colored front frame.

6. Is all of the fiberglass lining intact inside the speaker cabinet? It needs to be there on all surfaces for the cabinet loading to be correct. should look like this, minus the dry cat food.

All drivers are correct and original except for one of the tweeters. One went out after a few weeks of playing them and it is probably an open connection involving the fine wire. I got a replacement genuine 035Ti that is identical to the other. The midrange drivers have rubber gaskets on them and the woofers have the fiber gaskets fully intact and glued to the cabinet. All insulation is in good shape and cabinet walls are padded. The original owner sent the woofers out to a shop for refoaming only. The foam seems to be the correct thickness when compared to friend's XPLs with the same woofers. The overall foam job looks good and is on the outside of the cone. The ports are original and flawless. The original crossovers that I took out were in mint condition. Honestly I can find no physical flaws with any component on these speakers. They are easily a 9-10. 1987 mfg date, consecutive serial numbers, and plenty of years left.

The L100T3 crossovers from fleabay needed a little work. I had an audio technician bench check them and every component was in spec except for two open resistors in one of the midrange circuits and a red wire needed to be replaced due to damage. I robbed a red wire off one of the original crossovers and one 2.4 ohm resistor that was bad. The other resistor that was bad was the 20 ohm and was a different style than the one on the original crossover. I got a similar package replacement from Parts Express and installed the new ones in the same location on both crossovers in the midrange circuits. When I got the T3 crossovers in, I could tell that there was definately some refinement and toning down of the tweeters. The lower midrange improved. The midrange for the most part sounds good but can begin to get hot around 3kHz--especially on good recordings. These speakers are anything but laid back, which I expected, but a slight attenuation in the midrange might just make them the fantastic, dynamic monitors I wanted.

[danfan78]

I need to correct a statement I made in my pervious post. The foam is on the inside of the woofer cones, not outside. I have no idea why I said that. Foam job is good, professional. It has the appearance and thickness of OEM and it was done by a certified JBL shop. Anyway, I have found that with the speakers moved back to about 20" from the back wall, they warm up considerably and this helps to tame the midrange. They are towed in at 2 1/2", raised up 6" and have about a 1/2" tilt back and they are pretty nice at that placement. The sidewalls of the room are only about 13" away from the outside edge of each speaker and this is reinforcing brightness issues through early reflections. There is little I can do about this due to the placement of all other equipment.


For anybody reading, the T3 crossover is an improvement and makes these speakers much better. However there are other JBL monitors out there that have a much smoother midrange. I have listened to XPL200A's and LSR 32's recently and they get a lot of things right.

[danfan78]

Last month, I was extremely fortunate to pick up a very nice pair of 120ti's from a small studio in Dahlonega, GA where they were being used as midfield monitors. I have heard a lot of praise for these monitors and had very high hopes for them to outperform the L100T (T3) that I have. So far, I can tell you that they are laid back compared to the L100t3. Even though the tweeter and midrange can be defeated by
-2db each, I find that at 0db (no defeat) they are still laid back by comparison. They are more directional (due to their compact mirror image setup) and it seems that they are a lot smoother in the upper midrange (where the L100T (T3) was too forward)--around 3kHz I think. There is something different about that poly midrange in the 120ti too. I think it is drier than the 104H-2 in the L100T. Plus it seems to be more airy than forward as well. The harsh upper midrange I experienced before is more tame and I'm not sure if it is refinement in the 044ti vs. the 035ti or if it is crossover refinement for the ti series--or both factors. I think the 120ti is more refined overall as a whole and with some more adjustment to their positioning, they may be a perfect new set of mains.

One thing I'd like to try: I'd like to temporarily swap the 104H drivers from the 120ti's to the L100T (T3) speakers and see if the midrange improves. I will eventually be taking the 120ti's down and pulling all drivers to oil the cabinets anyway so I could satisfy my curiosity during that time. Thoughts?

[johnlcnm]

Maybe some insight. I went through a similar issue with a pair of 4425s. Very rough in the upper mid range. Replaced the diaphragms in the 2416s with Radian aluminum diaphragms. Also replaced the 2416s with 2426s which had the upgraded phase plugs. Still had the upper mid range roughness. Ended up replacing the 2214h woofers with 2206h's. Changed the woofer crossover to 2nd. order Bessel low pass with woofer inductance compensation. Big difference!! Very smooth midrange, boomy bass gone. If you look at the response of the 2214h there is a massive breakup at 2kH. That probably was the issue. I know that your L100T3s have an improved version of the 2214h. Probably the "dash one" designation. Guess/Swag on my part.

Regards,

John

[johnlcnm]

Also wanted to add: I am not saying that 2206Hs would work in your boxes. They are larger in volume than the 4425s. I considered the 128h. This woofer has a much smother response up to it's rolloff. The woofer crossover in the 4425s is also a half octave higher then your L100ts. The 4425 boxes are probably tuned higher also. I measured them at 40 Hertz.

A response chart for the 128h:

[danfan78]

Maybe some insight. I went through a similar issue with a pair of 4425s. Very rough in the upper mid range. Replaced the diaphragms in the 2416s with Radian aluminum diaphragms. Also replaced the 2416s with 2426s which had the upgraded phase plugs. Still had the upper mid range roughness. Ended up replacing the 2214h woofers with 2206h's. Changed the woofer crossover to 2nd. order Bessel low pass with woofer inductance compensation. Big difference!! Very smooth midrange, boomy bass gone. If you look at the response of the 2214h there is a massive breakup at 2kH. That probably was the issue. I know that your L100T3s have an improved version of the 2214h. Probably the "dash one" designation. Guess/Swag on my part.

Regards,

John

One issue with swapping the 128H into the L100T is that it has a different sensitivity than the 2214 and the crossover low pass filter isn't tuned for it. I found that out when I tried the 4412 crossovers in the L100T. Their low pass filter is tuned for the 128H so the 2214 was boomy, among other issues. I didn't yet have access to a pair of 128H's to try at that time and I sold the 4412 crossovers months ago. Also, note that I have the L100T with L100T components. The only exception is that I'm running L100T3 crossovers in them. I would like to try the 104H midrange from the 120ti in the L100T because sensitivity and response are similar to the 104H-2, but the poly cone and aluminum dust cap just may smooth out the midrange. I really am beginning to think that the biggest difference between the L100T and the 120ti is in the tweeter and attenuation circuit in the crossovers.