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Guglielmo
10-17-2013, 03:44 AM
HI to all,

I own since new a pair of JBL L166 Horizon whose Xover has been modified to accept a bi-amp set up. In facts an electronic Xover cuts @ 1000Hz the lower way from the upper so a Solid State 50W amp drives directly the woofer while a Vacuum Tube 40W amp the mid/tweeter. Obviously the passive Xover @ 6000Hz is retained.

Since new the woofers performed very well with abundance of bass. After 15 or more years the bass become longer and boomy so I checked under the grilles and I discovered that both woofers were needing reboarding being the original board completely pulverized. A near technical lab took in care the woofer and so the bass started again to perform as new, just the time for the running-in to reach the optimal sound.

Again after 15 years the woofers needed reboarding so this time I got the service from another "specialist" who aesthetically done a good job but from the first hours the bass seemed "dry", absent", too short, so I guesses that it was just a matter of time to break-in the suspension. Unfortunately more that one year is passed without better results, the only hope is that nowadays I don't have much time to listen to these JBLs preferring headphone use.

I have to highlight too that few months ago I changed the 50W Solid State amp (woofer dedicated) to a 100W always SS but the bass results are poor: dry, lacking, dull without power even if I increase the bass amp gain or insist with the bass tones on the preamp...

Question: perhaps the reboarding has not been done as required? May be utilizing some wrong suspension material? What else?

Thanks a lot for help!

Cheers,

Guglielmo

BMWCCA
10-17-2013, 06:50 AM
Assuming this is an electronic translation and you are referring to replacing the speaker surrounds, perhaps the second repair did use suspension material that is too stiff for the woofer? And assuming you've not changed the room position since the repair, there are only a few ways to make sure:

1. Go back in time?
2. Replace the 122A/1 woofers with known "correct" ones from another L166?
3. Borrow a 128H or 128H-1 woofer from a donor L112, 4412/A, L150/A, or similar if you can find a willing owner and see what happens.

:dont-know:

Best of luck to you.

Guglielmo
10-17-2013, 07:54 AM
BMWCCA,

finding a willing owner for such a woofer is not easy, by the way the speaker position is always the same so may be you are right saying that the "new" suspension material is too stiff. A friend suggested me to insist in the "break-in" because till now the woofer worked not enough due to my preferred headphone listening...

SEAWOLF97
10-17-2013, 08:54 AM
I'm suspecting phase problems ... either internal or external. Correct L166's produce bountiful bass.

check phasing (polarity) with battery ? :dont-know:

BMWCCA
10-17-2013, 03:12 PM
I'm suspecting phase problems ... either internal or external. Correct L166's produce bountiful bass.

check phasing with battery ? :dont-know:


That's likely a much better guess. I tend to blow right past the obvious. :thmbsup:

script56
10-17-2013, 05:39 PM
Actually I believe some L166 were "phased" factory by Jbl in reverse to what is customary. I had a pair of l166 that I did the battery test on woofer and it pushed "out" with positive battery terminal to negative post on woofer. My guess would be your woofer is "frozen" where the voice coil is not in the gap. You can test it just by lightly pushing on cone and check it it's "free" moving.

BMWCCA
10-17-2013, 08:27 PM
Actually I believe some L166 were "phased" factory by Jbl in reverse to what is customary.

As long as both woofers share the same polarity response, there should be no negative effect on bass performance, reversed or not. :dont-know:

script56
10-18-2013, 02:15 AM
BMWCCA sounds right about stiff surrounds.

ivica
10-18-2013, 03:18 AM
HI to all,

I own since new a pair of JBL L166 Horizon whose Xover has been modified to accept a bi-amp set up. In facts an electronic Xover cuts @ 1000Hz the lower way from the upper so a Solid State 50W amp drives directly the woofer while a Vacuum Tube 40W amp the mid/tweeter. Obviously the passive Xover @ 6000Hz is retained.

Since new the woofers performed very well with abundance of bass. After 15 or more years the bass become longer and boomy so I checked under the grilles and I discovered that both woofers were needing reboarding being the original board completely pulverized. A near technical lab took in care the woofer and so the bass started again to perform as new, just the time for the running-in to reach the optimal sound.

Again after 15 years the woofers needed reboarding so this time I got the service from another "specialist" who aesthetically done a good job but from the first hours the bass seemed "dry", absent", too short, so I guesses that it was just a matter of time to break-in the suspension. Unfortunately more that one year is passed without better results, the only hope is that nowadays I don't have much time to listen to these JBLs preferring headphone use.

I have to highlight too that few months ago I changed the 50W Solid State amp (woofer dedicated) to a 100W always SS but the bass results are poor: dry, lacking, dull without power even if I increase the bass amp gain or insist with the bass tones on the preamp...

Question: perhaps the reboarding has not been done as required? May be utilizing some wrong suspension material? What else?

Thanks a lot for help!

Cheers,

Guglielmo

Many of the forum members have been satisfied with Ric Cobb ( e-mail: rcobb@tampabay.rr.com ) foams for JBL drivers...as

http://www.audioheritage.org/vbulletin/showthread.php?28013-Rick-Cobb-Looneytunes-Replacement-Foam-Rings&p=282407&viewfull=1#post282407


http://www.ebay.com/usr/looneytune2001

http://www.ebay.com/itm/BEST-Speaker-Foam-Surround-Kit-for-JBL-12-L112A-122A-128H-H1-2214H-H1-2203A-H-/170811267175?pt=Vintage_Electronics_R2&hash=item27c5251867

Regrads
ivica

Krunchy
10-18-2013, 05:50 AM
Many of the forum members have been satisfied with Ric Cobb Yep! I got a set from him for my 166s, it was my first refoam job, easy enough & they still sound great.

hjames
10-18-2013, 06:38 AM
Yep - did a pair of 2214s with Rick Cobb kits - had them upstairs so I could monitor them
when I played the test tones after gluing the surrounds to the frame last weekend

60401

BMWCCA
10-18-2013, 06:53 AM
BMWCCA sounds right about stiff surrounds.

But I'd like to hear back from the original poster with results of a battery phase/polarity test. That's an easy first step that might be taken for granted (by me).

SEAWOLF97
10-18-2013, 08:26 AM
they sounded good, then ...

they left the house for refoaming. no other changes. so ......

if they move in & out freely , then would look at speaker wire
connections to the amp, then connections to the binding posts, then internally
from the xover to the driver.

eliminate the obvious before going major .... :banghead: