2118H - very low output ? Help

[gerard]

Hello

I just bought two old - 2118H

One is working ok ;
The other one works but gives a very very low output .
Measure between red and black : 12 ohms .
Do not know what is the problem and if there is a way to solve .

Thank's for help .

Gerard

[pentictonklaus]

[quote=gerard;136483]Hello

I just bought two old - 2118H

One is working ok ;
The other one works but gives a very very low output .
Measure between red and black : 12 ohms .
Do not know what is the problem and if there is a way to solve .

Thank's for help

12 Ohms sound like 2118 J 16 Ohm version. Do you have a 8 Ohm and a 16 Ohm version by any chance ? That would give a mouch lower output for the 16 Ohm version. It also would give a totally wrong crossover. Check the other 2118 for impedance. It could have been reconed and the sticker is wrong.

[gerard]

hello

well the first one gives 11.1 ohm the other one 5.7 ohms about .!

Gerard

[Zilch]

Well the first one gives 11.1 ohm the other one 5.7 ohms about.That certainly points to J vs. H versions, however, just connected to an amp directly, they should have the same output.

Compare the compliance of the cone between the two of them. They're pretty stiff to begin with, but if you can feel a difference, the voice coil may be binding in the gap.

I have a pile of 2118s here (well, three or four, actually) with slipped magnets. Mine are going to require professional help....

[gerard]

Zilch

Yes the cone is almost impossible to move in the 2118 with a problem ! the other one moves .

Any way to solve it ?

Regards

Gerard

[Zilch]

One of the reconers here is going to have to advise you on that. I have two in similar circumstance.

It seems that even though JBL used these in road gear subject to routine physical abuse, they are not up to the challenge of what shippers do to them these days.

[OR, they're already messed up and that's why they're being sold on eBay in the first place.... :(]

[gerard]

Sorry , I did not get everything !

Do I have to recone ?

Gerard

[Zilch]

I am familiar with two things which would cause that:

1) The magnet has shifted making the gap eccentric or jamming against the voice coil. This may be visible/measurable from the present magnet location. It should be concentric with the frame.

2) The voice coil was overheated and the former deformed or bubbled such that it no longer moves freely in the gap.

There may be other causes I am not familiar with. I am not a reconer, but it sounds like your driver needs professional help, probably a recone, and possibly also a resetting of the magnet/pole piece.

I'd just buy more instead, until I got enough good ones. 2118x recones are WAY expensive.

Hence, my pile of defectives. :(

[mech986]

Hi Zilch,


From JBL Pro Transducer Price List, AS October 2006
http://www.jblproservice.com/pdf/Transducers%20Parts%20List/Transducer%20Parts%20List.pdf


2118H $82.00 C8R2118 62355 52316 4-P-6 S1 Wt 2


2118J $82.00 C16R2118 62355 52316 4-P-6 Wt 2

Don't know if these prices have gone up or down from before. Compared to the current $162 for the recone kits for the 2235, seems about right. Of course, the problem with the magnets will have to get fixed first.

Regards,

Bart

[Zilch]

:hmm: Not as expensive as I recalled.

Time to think about whether I want "Hs" or "Js," then.... :thmbsup:

[ratitifb]

Hi all, thanks for the forum.

I bought recently on ebay US a 2118J pair in great shape. These speakers are very well sounding in the midrange (at low and high power levels) and if we compare both all seems to be OK from the first listenning test :). Just one is sounding with a higher pitch than the other and after double checking (without enclosure) it shows a lower diaphragm elongation at low frequencies than the other :confused:. That can be seen with eyes by applying a sine wave signal at 10Hz (elongation pk-pk lower than 0.15inch) without hearing any rubbing problem or friction from the moving coil inside magnet air gap. The level at low frequencies is lower too (few dB below 100-150Hz) and compliance seems to be higher (evaluated with fingers with extrem care...). What's happenning ?
DC coil resistance is 9.8ohms for the "bad" and 10.4ohms for the good. Magnets are centered for both.

When I'll have time I'll measure impedance curves with resonant frequency.

Anyone can help me to understand:banghead: ? Thanks, François

[Thom]

In the world that once was that magnet bit would be a real problem but in today's world as long as it happens outside of warranty and it doesn't happen enough to cut the customer base that's not only not a problem but it may be a good thing because it makes a hole to be filled possibly by a new JBL speaker. I'm not trying to blame JBL for having created this world. They didn't But I believe some real quality companies have resisted the temptation to go that way, at least in one premium line and reputations are made that way. The other philosophy is that the name is only worth something if you can take it to the bank. Such as ford with ghia and I won't go on.

[ratitifb]

Please see the two impedance curves I measured from my 2 2218J (without any enclosure). That confirms that one of both is showing some problems in low frequency range (as I heard before). However, both show a resonant frequency higher than Fs = 85Hz specified by JBL, 115Hz and 155Hz, for the "good" and "bad" respectively.

Does any one can explain ?

May I use these 2118J as midranges above 250-300Hz ?

(remember that nothing like rubing, ,buzzle, rattle can be heard at low and loud level)

[Earl K]

Hello Francois


When I'll have time I'll measure impedance curves with resonant frequency.

- You've made nice impedance curves for all to see. Congratulations !
- I've converted your file into a .jpg for easier viewing by others .


I bought recently on ebay US a 2118J pair in great shape. These speakers are very well sounding in the midrange (at low and high power levels) and if we compare both all seems to be OK from the first listenning test .

- Do you still have the eBay # for this purchase ?
( I'd like to look it up to see if there are some hidden clues within the sellers descriptive text . )


Just one is sounding with a higher pitch than the other and after double checking (without enclosure) it shows a lower diaphragm elongation at low frequencies than the other . That can be seen with eyes by applying a sine wave signal at 10Hz (elongation pk-pk lower than 0.15inch) without hearing any rubbing problem or friction from the moving coil inside magnet air gap.

- I'd suggest that you "exercise" ( breakin ) these midbass woofers a bit more by applying 5 to 7 volts at 20 hz for a good 12 hours . ( Make sure the vent of the woofer is unobstructed when doing this / assuming the woofers are facing upwards . ie ; place the magnet on 2 pieces of wood split apart 25 to 50 mm / with this "gap" under the magnet vent . )
- Then remeasure the Fs and Zmax ( as you did ) and repost the results .
- After "exercise" the Fs will shift downwards somewhat and Zmax will increase at Fs .
- I'm thinking you have a pair of relatively new recones / which aren't yet broken in .
- Do you see any visible printed white numbers on the back of the paper cones ? If so, what are they ?



The level at low frequencies is lower too (few dB below 100-150Hz) and compliance seems to be higher (evaluated with fingers with extrem care...). What's happenning ?

- Because the Fs and Zmax is different for both woofers / the TS parameters will also be different . This shift in TS param(s) will effect the Frequency Response curve ( like you have noticed ) .



DC coil resistance is 9.8ohms for the "bad" and 10.4ohms for the good. Magnets are centered for both.

- I'm just guessing - but - those numbers appear to be close enough to be "in spec" / considering normal tolerance ratios .
- Hopefully, one of the senior reconers here will offer their thoughts .

[ratitifb]

Thanks Earl

regarding item #260075729767 - Pair JBL 2118J 8" Woofers 16 Ohms Speakers 2118 J

ebay link : http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&ih=016&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=260075729767&rd=1&rd=1

and the reply of the seller after suggesting he reads this thread on forum
"Those speakers are untouched since I have owned them. If break-in is an issue, it is because they were used only for vocal speaking in a PA application. I guess since you are such an expert I won’t have to explain the meaning of this."

I'll do my best to measure impedance after breakin test and let you know (same for printed numbers I have to read on)

[ratitifb]

After more than 12 hours breakin test @ 6Vrms/20Hz, impedance curves are exactly the same. Neither Fs neither Zmax have been increased or decreased after "exercise" so unfortunately I don't have to post my new results...

Regarding the printed white numbers on the back of the paper cones both have the JBL #62356.

[ratitifb]

Does anyone know the maximum voltage at 20Hz before damage due to cone excursion and/or voice coil moving limitation ?[/speaker in free field without enclosure load]

[Earl K]

Hi Francois,

- Too bad about the lack of extra breakin ( or in this case , this being a mature breakin ) .

- Now, I'd use these 2118J as is, if they are being put into a sealed sub-enclosure, passively crossed over above 225 hz .

- Everything looks original to my eyes . But then, only a reconer will recognize those parts numbers on the cone ( maybe one will weigh in to this , at some point ).
- You got a great deal on the purchase of these two / so I wouldn't let these "out of spec" stats bother you too much .

:)

[ratitifb]

Thanks a lot Earl for quieting my brain. Nothing is perfect ... in this world even with JBL !

I'll put that 2118J pair into a sealed sub-enclosure, passively crossed over above 250 Hz as suggested in another thread I have posted

http://audioheritage.csdco.com/vbulletin/showthread.php?t=14629

What about knowing the maximum voltage at 20Hz before 2118J damage due to cone excursion and/or voice coil moving limitation ? [speaker in free air without sub-enclosure load]

Does anyone could let me know ?