JBL L300 components in a restored L200 cabs bass issue

Oneoff

Oneoff

AK Subscriber
Subscriber
Hi everyone!
I recently restored L200 cabinets and installed L300 components which I bought in advance. I modified the cabs for only one port, sealed and dampened everything exactly as it should be.
I have the Nelson pass crossovers and everything is up to specs but… I’m not impressed with the low end at all. in fact I’m pretty sure that something is wrong with both 136a Alnico woofers. At this point my 10” JBLs from the 90’s have the same or better low end.
I double checked my wiring, the crossover boards against the Nelson pass schematics, polarity is exactly as it has to be (with only the horns polarity is the opposite to the woofers and the tweeters). The mids and highs sound just amazing, but these woofers should move much more air, i’m sure!
So where do I start with finding out what’s wrong without buying a new set of 15” woofers?
I’ve heard that these drivers can lose some power over time, but I doubt that it might be that much… I mean-
the mids and highs potentiometers are turned almost all the way down in order not to overtake the bass.
The woofers have newer surrounds and physically is a great, not abused condition. The cone that installed is the original 2231A.
I’m driving these with a powerful 250 WPC analog amp
(Not bi-amped).
I‘ve always dreamed of having my own L300 after hearing them in a shop.
This project has cost me a small fortune and took half a year of work to complete in my free time… it’s hard not to feel the disappointment right now.
I appreciate your tips of where should I try to debug this issue.
 
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You might try hooking up the Woofer directly to your amp
And Bypass the Xovers and mids n tweets.
Just to rule out something in the Xovers you might have missed are you sure your amp is healthy?
Don’t be afraid to feed the 2231 some power
If they still don’t put out any meaningful bass
They could have been abused by heat and or
Very high power causing the
weakened magnetic strength
This was stated by Jbl engineer Greg Timbers
I have 2231a’s and 136a’s the same woofers
and 136h ceramic versions
All have outstanding Low bass output .
If you were close by I would loan you one
 
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Thanks for the replies!
I will pull out the xovers and check again. these were made for bi-amping so I combined the inputs in order to feed it with my amp. The amp is fine. I have small JBLs that plays great.
The woofs are moving in with a 1.5 battery as they should.
Would it be a good idea to connect the 136a to the small jbl xovers (10”) woofs output?
where can I check the woofers? Or professionally recharge the magnets?
 
You certainly aren’t going to hurt the Woofers
By trying it
The 136’s directly to the amp is easier
 
BTW- the previous owner said that these were too ‘boomy’ for his taste. He had all of these components in a cabinet.
Judging from the clean physical shape of the woofers I tend to believe that the problem is probably with the xovers.
I will try it after work…thank you!
 
In my experience it is pretty rare for the big Jbl Alnico
Magnets to loose a high amount of their energy
Judging by the statement that you combined the Xovers components that are designed for Biamping
That’s probably the problem
You can also use them that way and test the woofers
On the LF circuit
 
So I couldn’t wait and hooked them directly to the amp. While there is a slight improvement, it’s definitely still lacking.
: / I will test it more later…
 
Foam surrounds are very nice and replaced by the previous owner. Everything is clean and looks centered.
I will check DC resistance and report back..
 
Another thought- are these large caps on the low end portion of the XO circuit need time to charge? Maybe days?
I’m running these speakers for just few hours of testing while I also unplugged everything a couple of times…
 
Oneoff said:
Another thought- are these large caps on the low end portion of the XO circuit need time to charge? Maybe days?
I’m running these speakers for just few hours of testing while I also unplugged everything a couple of times…
Click to expand...

Absolutely not, that should not be the case.

Bass turned down on your preamp? Have you tried a different amp?
 
I have no bass and treble adjustments on my amp. It’s a musical fidelity A5 integrated that pushes my smaller 10” JBLs Like a champ with a round punchy bass. It has significant amount of power 250 WPC at 8 ohms (just checked the spec sheet)

I don’t have another amp ATM..
 
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Oneoff said:
Hi everyone!
I recently restored L200 cabinets and installed L300 components which I bought in advance. I modified the cabs for only one port, sealed and dampened everything exactly as it should be.
I have the Nelson pass crossovers and everything is up to specs but… I’m not impressed with the low end at all. in fact I’m pretty sure that something is wrong with both 136a Alnico woofers. At this point my 10” JBLs from the 90’s have the same or better low end.
I double checked my wiring, the crossover boards against the Nelson pass schematics, polarity is exactly as it has to be (with only the horns polarity is the opposite to the woofers and the tweeters). The mids and highs sound just amazing, but these woofers should move much more air, i’m sure!
So where do I start with finding out what’s wrong without buying a new set of 15” woofers?
I’ve heard that these drivers can lose some power over time, but I doubt that it might be that much… I mean-
the mids and highs potentiometers are turned almost all the way down in order not to overtake the bass.
The woofers have newer surrounds and physically is a great, not abused condition. The cone that installed is the original 2231A.
I’m driving these with a powerful 250 WPC analog amp
(Not bi-amped).
I‘ve always dreamed of having my own L300 after hearing them in a shop.
This project has cost me a small fortune and took half a year of work to complete in my free time… it’s hard not to feel the disappointment right now.
I appreciate your tips of where should I try to debug this issue.
Click to expand...

I don't blame you. I did the same thing with the same results. I've also increased the internal volume by enclosing the base and opening it up to the interior. I've even gone back to the two ports and internally flared them. I've never been happy with the 2235 woofers and get more bass out of my JBL W10GTis in 2 cubic feet used in the four surround speakers. I gave up and moved on to my own creations (the Ethyl Mermans) that use the 2241H 18", 2251J 10", and Great Heil. But even more than frequency response, the Merman's present a soundstage and image in ways that the L200/300 can't hold a candle. JBL horn speakers were never acclaimed for their imaging.
 
toddalin said:
I don't blame you. I did the same thing with the same results. I've even gone back to the two ports and internally flared them. I've never been happy with the 2235 woofers and get more bass out of my JBL W10GTis in 2 cubic feet used in the four surround speakers. I gave up and moved on to my own creations (the Ethyl Mermans) that use the 2241H 18", 2251J 10", and Great Heil. But even more than frequency response, the Merman's present a soundstage and image in ways that the L200/300 can't hold a candle. JBL horn speakers were never acclaimed for their imaging.
Click to expand...


That sucks! But I remember listening to the L300 and even the stock L200, being so impressed with that punchy bass!
I mean.. something must be off here
 
Something's gonna be wrong. I ran L200B, and now run L300, with 136A in both, copious bass from both.

If only you had a second set of cabinets, or a second set of 136As, to swap around to try to isolate the issue.

Solder is all good on the crossovers? Internal speaker wiring is all OK?
 
I'd expect one woofer is out of phase of the other, thus room cancelling effect.
Or something major wrong with the crossover circuit (bad solder joint, shorted leg, etc)
You say you have the Nelson Pass networks. Who assembled them, you, or an outsider?
(no flames meant, just curious).
I got some Nelson pass networks from via ebay from a site in Nevada, but don't have cabinets yet,
and have not had time to check them. Yet.
 
Johnny_Law said:
Something's gonna be wrong. I ran L200B, and now run L300, with 136A in both, copious bass from both.

If only you had a second set of cabinets, or a second set of 136As, to swap around to try to isolate the issue.

Solder is all good on the crossovers? Internal speaker wiring is all OK?
Click to expand...
Agreed something is wrong…they should impress!
 
hjames said:
I'd expect one woofer is out of phase of the other, thus room cancelling effect.
Or something major wrong with the crossover circuit (bad solder joint, shorted leg, etc)
You say you have the Nelson Pass networks. Who assembled them, you, or an outsider?
(no flames meant, just curious).
I got some Nelson pass networks from via ebay from a site in Nevada, but don't have cabinets yet,
and have not had time to check them. Yet.
Click to expand...
I went over the Nelson pass XO schematics VS the actual board and all seems legit. I reflowed the solder joints after I got the XO shipped to me.
These XO are made by Jantzen Audio with nice components. The low freq. section is quite simple and I found only one difference - the use of one 10R resistor VS two 20R in parallel which gives the same value at this configuration…
BTW-
I checked the polarity of both woofers with 1.5V battery and both are going back with red-positive, black -negative polarity (as they should). The XO wired and assembled identically. Can’t see anything wrong at least after spending a couple of hours looking at them.
Bass sounds anemic with only one speaker plugged in, so I don’t think it’s a phasing issue.
 
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Should I just order a cheap 8 ohms 15” woofer to check it out against the orig.?
What would be a good candidate ?
 
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