Tweaking up some L100Ts

[danfan78]

I have found a lot of helpful information here so I have decided to join and start a thread. I own a pair of JBL S38II that were being used for mains and a friend recommended that I get a pair of L100Ts (or T3s). I was wanting to achieve a big soundstage with good imaging. After some searching and patience, I found a nice pair of L100Ts with sequential serial numbers, refoamed woofers and good cabinets. The seller still had the original cartons and packing material saved--which I used to transport them. My friend and I re-oiled the cabinets, repaired a small chip in the veneer, fixed a speaker grill post, and replaced the grillcloth. They turned out looking like new but the sound--well that was something else entirely.

We tried them on the floor, raised them up, and experimented with tilt, toe, and moving them in and out from the wall and no matter what they are very bright--especially in the mids. I was able to curb this with use of an EQ (digital plug-in on JRiver) and it helped but they just didn't sound quite right compared to what I expected. From what I have read, the T3 crossover helps a lot...so again with patience, I found a pair on Ebay. They needed a little TLC, and a couple of components replaced. After a clean bill of health from an audio technician, I installed them and got better results overall but no "wow, that's a different speaker!" effect. Polarity was a concern, but it is correct.

After trying L100T3 crossovers, I tried a set of 4412 crossovers with L pads. These are very similar to the original L100T crossover design except for the addition of L pads. We thought that these would be the ultimate cure but to our surprise, the crossovers don't sound right at all--even after checking (and correcting) polarity and making incremental adjustments to the mids and highs.

Right now the T3 crossovers are back in and the speakers are raised up 6", slightly toed in, slightly tilted back and sound the best that I have heard them. However, on really good recordings, female vocals are a little too forward and there is still some harshness in the 3K range. I feel like placement alone will not give me the equalization I need. My next thought is to attempt temperorarily installing L pads in conjunction with the T3 crossovers to get these things tamed. I would like to hear thoughts and get some feedback from those who know these speakers or have had similar problems.

[DavidF]

The tweeter, the 035ti or -tia, has a foam plug sitting on the pole piece behind the metal dome. The purpose of the foam is to damp resonance and meant to actually contact the dome. Soooo, as foam it will deteriorate. At worst it can form into a sort of goo that can seep into the coil gap and impede the tweeter's ability to function. You can get some nasty response artifacts IF this is the problem.

This is one possibility but if the tweeters have never been touched, then a potential problem even if the foam has not moved down into the gap.

The face plate is removable but you need a little patience in reassembly. Best to have a signal (tone generator or CD with test tones) playing through to help get the coil centered. Reply if you want to explore this further.


P.S. ...welcome to the forum.

[SEAWOLF97]

The tweeter, the 035ti or -tia, has a foam plug sitting on the pole piece behind the metal dome. The purpose of the foam is to damp resonance and meant to actually contact the dome. Soooo, as foam it will deteriorate. At worst it can form into a sort of goo that can seep into the coil gap and impede the tweeter's ability to function. You can get some nasty response artifacts IF this is the problem.

this thread is about replacing foam in a 044Ti , but good info on the foam if you need to do the 035

http://www.audioheritage.org/vbullet...ght=044ti+help

[danfan78]

The tweeter, the 035ti or -tia, has a foam plug sitting on the pole piece behind the metal dome. The purpose of the foam is to damp resonance and meant to actually contact the dome. Soooo, as foam it will deteriorate. At worst it can form into a sort of goo that can seep into the coil gap and impede the tweeter's ability to function. You can get some nasty response artifacts IF this is the problem.

This is one possibility but if the tweeters have never been touched, then a potential problem even if the foam has not moved down into the gap.

The face plate is removable but you need a little patience in reassembly. Best to have a signal (tone generator or CD with test tones) playing through to help get the coil centered. Reply if you want to explore this further.


P.S. ...welcome to the forum.

Thanks for the welcome and reply. I have heard about this issue with the foam but I have yet to check the condition of mine. It is something that I do need to explore. I have two more additional tweeters of this type in a pair of L20Ts. I will say that the tweeters sound fantastic and crisp. The issue that I'm hearing is in the midrange--particularly in the 3K range. The driver chambers do have insulation pieces in them but there is a small hole where the wires are ported through. I had to dig out a little of the hot glue dab in order to swap out crossovers, I did not reseal these holes yet because I'm still experimenting. The small hole is acting as a tiny vent for the midrange driver but I doubt the difference between a sealed chamber and having the tiny hole is audible.

[DavidF]

Thanks for the welcome and reply. I have heard about this issue with the foam but I have yet to check the condition of mine. It is something that I do need to explore. I have two more additional tweeters of this type in a pair of L20Ts. I will say that the tweeters sound fantastic and crisp. The issue that I'm hearing is in the midrange--particularly in the 3K range. The driver chambers do have insulation pieces in them but there is a small hole where the wires are ported through. I had to dig out a little of the hot glue dab in order to swap out crossovers, I did not reseal these holes yet because I'm still experimenting. The small hole is acting as a tiny vent for the midrange driver but I doubt the difference between a sealed chamber and having the tiny hole is audible.

Swap out the tweeters, if they are the same model (input terminal location may be different). I have heard a tweeter with gap clogged. It tended to howl like some there were some resonances in the lower responses and the high end response was nil in comparison. So this would sound harsh in the tweeter's pass band from (4k Hz and lower).

If it is not the tweeters, then what? Can't say for sure. I would not think that the system voicing of the L100t would be all that different from the 3-way S38 you are used to. These mids are fairly indestructible if not abused.

[danfan78]

I don't see any issues with the tweeters from either speaker (L100T or L20T). The L100ts, even with the L100T3 crossovers, are still too forward in the mids. I might try replacing the insulation in the midrange chambers with some foam to help deaden them some. I still need to seal up the small holes in the back of the chambers from where I have swapped out crossovers too, but am waiting until I know that all modifications are permanent. I'm still entertaining adding L-pads in conjunction with the T3 crossovers but need some guidance on how do do it and maintain proper crossover function.

[speakerdave]

Suppressed bass could sound like aggressive midrange. If the new foams on the woofers are wrong--not as compliant as they should be--woofer cone movement will be impeded.

[speakerdave]

Also, I think you were right to consider the hole in the sub chamber. You might be right that it does not matter, but I would take the time to plug it temporarily with modeling clay, which would have to be redone soon, or duct seal which would be longer term.

[Chris Brown]

OP, i'm not surprised that the 4412 crossovers did not give you what you were looking for. I have a pair of 4412 speakers right next to my L100T speakers (with crossovers upgraded to T3 spec) and the 4412 speakers have considerably more mid-range. That is because they are studio monitors and are supposed to be as flat sounding as possible. The L100T speakers have a degree of that traditional "West-coast" sound, which involves somewhat of a recessed midrange (particularly lower midrange). I also have a pair of L150 speakers, and they exhibit more of that "west-coast" sound even compared to the L100T speakers. If you end up giving up on the L100T speakers, you might look for a pair of L150s, or maybe a pair of L110, L112, or other JBLs of that slightly older vintage.

There is no "sub" chamber in an L100T box? Not on any I have ever seen/worked on. Just a cup for the mid

There more than one version of this box?

He had to have meant "Sub chamber" in the context of the mid chamber being a subset of the main chamber.

[DavidF]

I don't see any issues with the tweeters from either speaker (L100T or L20T). The L100ts, even with the L100T3 crossovers, are still too forward in the mids. I might try replacing the insulation in the midrange chambers with some foam to help deaden them some. I still need to seal up the small holes in the back of the chambers from where I have swapped out crossovers too, but am waiting until I know that all modifications are permanent. I'm still entertaining adding L-pads in conjunction with the T3 crossovers but need some guidance on how do do it and maintain proper crossover function.

The LPad may work for you but not without some amount of re-wiring and unpredictable changes in the response. The introduction of the 8ohm load in the circuit may unbalance the filter response that was designed for the resistive load of the circuit plus the driver.

Anyway, I suggest inserting the LPads ahead of C5 and L3 in the midrange circuit, and ahead of L4 in the tweeter circuit. I think you want the ability to adjust both. The DC resistances of the mid and the tweeter suggests using a 4 ohm LPad, but you may want to use 8 ohm in this application.



L100t ts.pdf

[danfan78]

Let me explain a few things in more detail about what I have currently. My room is 13 X 20. I wish it could have been a little wider but when I finished the basement area I have, I am confined by exterior walls and a center load bearing wall so the dimensions are unchangeable. The walls are sheetrock, the floor is carpet, and the ceiling has accoustic tiles. The L100Ts are firing along the long walls. I tried to get the speakers as close to only 8 feet apart as possible in order to get them at a good spacing for their size but away from the side walls. Between them is my 65" TV with stand, audio rack, and a Klipsch SW-12 subwoofer. I have moved them between 1-3 three feet from the back walls and they seem to like being 2.5' away. However, the tweeter centerlines are only about 18" from each side wall. There is not much I can do about it. The speakers are toed in 2" each, raised 6" and tilted back a few degrees. I get good imaging, a big sound stage, and almost an ethereal three-diminsional sound from really good recordings. The T3 crossovers are definately a good improvement. I had hoped that the new crossovers would have provided some improved attenuation for the midrange, but it didn't.

It was noted that I had made small openings around the wires going into the back of each midrange chamber only so that I could swap between crossovers (T, 4412, and T3). If I had it to go over I should have just unsoldered the midrange wires from the original crossovers. Then I could have put on some temporary Faston connectors to connect them to the crossovers--which would have kept the chambers completely sealed. The drivers do have rubber gaskets and they are in good condition. However, I have yet to grab the hot glue gun and seal them back up. The holes are so small that I can only remove wires one at a time anyway. The foam job on the 12" woofers was done by a shop that the original owner sent them to some time within the last five years. It looks good to me. It's neat, centered, and on the outside of the cones. It makes a lot of sense that if the bass is weak for some reason, that the midrange would sound off more than it should, but I'll have to say that the T3 crossovers improved the bass some. Adjusting the speaker placement warmed them up some too. I feel that I am close to achieving great sound with them, but nocking down the midrange a couple of decibels will probably be required. I know that the L112 and 150 were mentioned and to their advantage they have L-pads. I think the L100T, as well as others in that lineup should have had them too. This way they are dialed into a room. I am currently looking to try some XPL 140s if I can get them, maybe some 4410s (original, not As), or the elusive 120Ti with its midrange attenuator. Until I either fix the L100Ts or find a replacement that I like, they are are not altogether bad or unlistenable--just forward in the upper midrange (around 3K).

[SEAWOLF97]

I know some will freak at the thought of damping material in front of the LE5, but hey, they've been causing pain and problems for decades, ergo "the West Coast Sound": translation? Too f'ing BRIGHT in a whole lot of typical, real world rooms
(what's the first thing a LOT of people do when they get a pair of L20Ts?

Thomas

I had some little Altecs. They tamed the tweet by making a small cloth cover over it ..OEM

[mech986]

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.

[mech986]

7. Is the port tube correct - my L100T3 port measures 4 1/8" ID x 5 1/4" long.

8. As you mentioned, seals around all drivers, and the midrange cup should be intact and sealed.

[Wagner]

Hi danfan, welcome to AK!

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