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pathfindermwd
10-18-2010, 11:23 AM
I had posted awhile back about my L100t's which I had recently purchased, popping at high bass levels. I had received some advice to recone them, which I was hesitant to do because of the cost. I finally did get the recone done with genuine JBL cones, and while I can tell the bass is much tighter and punchier, they will still pop at higher volume/bass levels/sources. I am a little disappointed, am even more baffled. Though I really like the sound and have little doubt about the quality of these speakers, this popping has me really scratching my head. None of my other speakers has ever done this. CF100's, CF150's, and cheaper ones still.

I had hoped that reconing them would be the solution, thinking that and old suspension might be the problem. A few of my friends own these speakers and they report that they will also pop if driven (too) hard. A friend suggests that other speakers will just distort, while these will instead pop. Seems reasonable.

I was hoping someone here might be able to add something more to this, and my general knowledge.

The enclosures are original L100T's, with T3 crossovers, powered by a NAD C375BEE/150w/channel

Don C
10-18-2010, 02:09 PM
What signal source is in use when you hear the pop? A turntable?

Robh3606
10-18-2010, 02:18 PM
Turn it down a couple of dB if it happens with all sources.

Rob:)

pathfindermwd
10-18-2010, 02:19 PM
What signal source is in use when you hear the pop? A turntable?

No, any source. CD player, computer. This is an over-extension popping. Like when you hook up a 9v battery polarity check and a cone pops in and out to its limit.

pathfindermwd
10-18-2010, 02:23 PM
Turn it down a couple of dB if it happens with all sources.

Rob:)

Hi, thanks Rob, I know, it's what I am forced to do, I just don't understand why the suspensions aren't holding them back from doing this.

edgewound
10-18-2010, 05:32 PM
Check to see if the port tubes are still in place.

If they are, you can experiment with tuning the box to a leakage-damped port by stuffing some breathable open-cell foam in the port or some dacron fiber fill. This can prevent the cone from unloading below the tuning frequency of the enclosure...

Or...the spiders have torn loose from the voice coil former.

pathfindermwd
10-19-2010, 08:04 AM
Check to see if the port tubes are still in place.

If they are, you can experiment with tuning the box to a leakage-damped port by stuffing some breathable open-cell foam in the port or some dacron fiber fill. This can prevent the cone from unloading below the tuning frequency of the enclosure...

Or...the spiders have torn loose from the voice coil former.


Thanks Edgewound. I checked the spider and it's fine both to the frame and the voicecoil. The original tubes are in place. I will have try the stuffing to see if it helps. Thanks for the the advise.

Don Mascali
10-19-2010, 09:09 AM
Perhaps we are talking about the need for a high pass filter? :dont-know:

DavidF
10-19-2010, 11:26 PM
I had posted awhile back about my L100t's which I had recently purchased, popping at high bass levels. I had received some advice to recone them, which I was hesitant to do because of the cost. I finally did get the recone done with genuine JBL cones, and while I can tell the bass is much tighter and punchier, they will still pop at higher volume/bass levels/sources. I am a little disappointed, am even more baffled. Though I really like the sound and have little doubt about the quality of these speakers, this popping has me really scratching my head. None of my other speakers has ever done this. CF100's, CF150's, and cheaper ones still.

I had hoped that reconing them would be the solution, thinking that and old suspension might be the problem. A few of my friends own these speakers and they report that they will also pop if driven (too) hard. A friend suggests that other speakers will just distort, while these will instead pop. Seems reasonable.

I was hoping someone here might be able to add something more to this, and my general knowledge.

The enclosures are original L100T's, with T3 crossovers, powered by a NAD C375BEE/150w/channel

Is the "pop" sporadic or more of a machine gun rattle?
What is the woofer doing when the pop occurs? Is there considerable visable motion with the cone? Does the woofer shift in or out and seem to hang in that position?
Has the crossover been altered from original spec, that you are aware of?
Can you swap out amps to check on the power side to confirm the problem is the speaker?
Me thinks the NAD is behaving badly under this load for some reason.

pathfindermwd
10-20-2010, 09:28 AM
Is the "pop" sporadic or more of a machine gun rattle?
What is the woofer doing when the pop occurs? Is there considerable visable motion with the cone? Does the woofer shift in or out and seem to hang in that position?
Has the crossover been altered from original spec, that you are aware of?
Can you swap out amps to check on the power side to confirm the problem is the speaker?
Me thinks the NAD is behaving badly under this load for some reason.


Thank you for your reply David. Hmm, well It could be the amp, but a friends L100t does this as well on his own amp. When it pops I see the cone come out to a maximum level, so this leads me to believe that it is an elctronic sound, like when you use a 9v battery for a polarity check, and you get a pop or click. The crossovers came out of a L100s I also bought. The crossover wires to the speakers do not look original as the positive for the woofer is yellow and the negative blue. Whoever had the "S' had also switched the connectors on the tweeter itself. I caught theis one day and checked it against the "T" tweeters, the positive and negative spades on the tweeters were opposite! And you could see that the glue was messy suggesting that there had been some tampering. The "S" had always sounded terrible and we now think this is why. The "T" however sound great with the crossover, much less bright. Edgewound had hit upon something which I think has solved this problem, and I will reply to that in the following post.

pathfindermwd
10-20-2010, 09:41 AM
Check to see if the port tubes are still in place.

If they are, you can experiment with tuning the box to a leakage-damped port by stuffing some breathable open-cell foam in the port or some dacron fiber fill. This can prevent the cone from unloading below the tuning frequency of the enclosure...

Or...the spiders have torn loose from the voice coil former.


Edgewound, I am glad you mentioned unloading. Is the ventpole screen/filter part of the restrictive system? Mine was completely deteriorated, just being foam. So I made one of my own from some aluminum screen and thin foam and glued them together to the back of the vent hole. I used the screen just to support the foam, and made sure the foam was very breathable. Hard to believe but I think the problem has been solved! I cranked them up and got no popping! It may have affected the outright output at higher levels, but if it stops the popping, I'm happy.

robertbartsch
10-21-2010, 08:48 AM
...get the amp checked since it could be dumping DC into the outputs

DavidF
10-21-2010, 09:43 PM
...get the amp checked since it could be dumping DC into the outputs
Agree. The description of the cone maxing at limits of suspension is a telling symptom. I am no electronics guru but this sounds like a problem strictly with the amp. Is this an 15 year or so old solid state? It seems a coindence that your friends system does the same thing. Is he using an older model as well?

If you have a digital mutlimeter you should check for DC at the speaker terminals. No input or speaker connection, amp on, set meter to DC mVolts, probes to each of the speaker terminals on one channel at a time. A reading of more than 50mV is a concern. More than 100 mV a problem.

Chris Brown
10-22-2010, 07:48 PM
I've only had this happen a few times with my JBLs.

About 7 years ago I was using my L150's as mains in my home theater, watching Apollo 13 on Laserdisc (PCM audio track with NO dynamic range compression) during the Saturn 5 launch scene. Woofers popped a few times but you could tell the Pioneer SX-1050 I was using at the time was struggling via the faceplate lights dimming...

2nd time was when I had a loose connection on a cable I was using between my preamp and Yamaha P2201 amp, I touched it while the amp was on and it must have shorted for a second. The woofer did more than pop, what came out of my L100T's sounded like someone pushing a bookshelf (with books) down a staircase.

I have not had any issues during "normal" usage while supplying the speakers with good clean power, and I run the speakers pretty hard. My EQ settings are hardly flat (http://gotnorice.dnsdojo.com/eq.jpg), and I regularly measure as high as 133dBC with my meter.

pathfindermwd
10-28-2010, 10:08 AM
ok so I finally dug out an old amp, some old JVC receiver. Same thing, it pops. On the JVC I noticed that in loud mode the woofer movement is wild, talk about good vibrations...or err not so good. Given the inability of the JVC to control woofer excursion and the inevitable woofer popping, I think this might have something to do with an under-powered amp.

The NAD on the other hand is maybe a year old. I have not done a DC volt test on it because I am not sure how it is done. How can I test only one channel at a time with the positive and negative on the volt meter (I am going to feel stupid)? But I am kinda leary at the notion of it being a problem with the amp, my CF150's are the "B" channel and they never pop with the same power on the same music, even at 98db sensitivity (and that's brutal output for them). And they used to be switched around, so it shouldn't be that. Why is the notion that popping can occur not being readily acknowledged? Under what conditions is what I feel I am chasing, so I can perhaps address it.

The addition of the foam filter to the vented pole piece has greatly helped, I mean I really have to get toward abuse for it to pop now. I lean towards it being under-powering, though I know this cant be the whole story. These 2214's are kind of an interesting breed because they have a very deep cone. Is this design contributing to this? Does it cause some kind of instability at high excursion?

The ramblings of a mad-man! :banghead:

DavidF
10-28-2010, 01:46 PM
ok so I finally dug out an old amp, some old JVC receiver. Same thing, it pops. On the JVC I noticed that in loud mode the woofer movement is wild, talk about good vibrations...or err not so good. Given the inability of the JVC to control woofer excursion and the inevitable woofer popping, I think this might have something to do with an under-powered amp.

The NAD on the other hand is maybe a year old. I have not done a DC volt test on it because I am not sure how it is done. How can I test only one channel at a time with the positive and negative on the volt meter (I am going to feel stupid)? But I am kinda leary at the notion of it being a problem with the amp, my CF150's are the "B" channel and they never pop with the same power on the same music, even at 98db sensitivity (and that's brutal output for them). And they used to be switched around, so it shouldn't be that. Why is the notion that popping can occur not being readily acknowledged? Under what conditions is what I feel I am chasing, so I can perhaps address it.

The addition of the foam filter to the vented pole piece has greatly helped, I mean I really have to get toward abuse for it to pop now. I lean towards it being under-powering, though I know this cant be the whole story. These 2214's are kind of an interesting breed because they have a very deep cone. Is this design contributing to this? Does it cause some kind of instability at high excursion?

The ramblings of a mad-man! :banghead:

Yeah, it makes you wonder it isn't the speakers but I am still thinking amp issue. It seems less to do with the actual amp than what kind of demands are made on the amp. Can you remove any signal processors, swap out interconnects and speaker wire? Try your JVC on a clear FM channel, neutral Bass Treble, with some short ordinary speaker wires, same with the interconnect, and see what happens.

pathfindermwd
10-31-2010, 12:42 PM
Yeah, it makes you wonder it isn't the speakers but I am still thinking amp issue. It seems less to do with the actual amp than what kind of demands are made on the amp. Can you remove any signal processors, swap out interconnects and speaker wire? Try your JVC on a clear FM channel, neutral Bass Treble, with some short ordinary speaker wires, same with the interconnect, and see what happens.


Yeah, it makes you wonder it isn't the speakers but I am still thinking amp issue. It seems less to do with the actual amp than what kind of demands are made on the amp. Can you remove any signal processors, swap out interconnects and speaker wire? Try your JVC on a clear FM channel, neutral Bass Treble, with some short ordinary speaker wires, same with the interconnect, and see what happens.

Hi Dave, I don't listen to the radio on the system. Sources are a computer, a DVD player, and a CD player. If I turned down the treble and the bass to neutral levels, I doubt I would get the speaker pop on any input (now that I added the foam to the pole piece), without either playing the source near full blast, or unless that source had very substantial bass to begin with. Of course if the solution were to turn down the bass, I'm afraid I would become pretty uninterested in the speakers all together :D.

I have had a total of 5 pairs of speakers hooked up to (and cranked to) this amp at home, and ran the 250's on it so my friend could see if he liked the NAD. It has never popped another set of speakers. It's not the amp....or should I say it's not an amp problem. On the other hand since I became aware of this popping we have successfully popped a total of 2 L100T's and 1 L100S's using two different amps/systems, it's not a source problem. Listening tests point to a woofer problem. But now that I have replaced the cones, it's not just an old woofer problem, though my experience says that deteriorated vented pole piece foam could make it worse. Maybe poor engineering of the vented pole piece is the problem. Other vented pole pieces I have seen use a heavy screen, not foam, and it's visibly clear that the restricted air space is substantial compared to an open hole, at least on the one's I've carefully looked at. One of the other posters talked about restricting box venting, and I was curious to find out if changing the venting of the pole piece would have the same net effect, it seems to have.
I believe that it's possible to pop any woofer (though I have NEVER popped any other woofer), this woofer seems particularly sensitive to it. Empirically, I can come to no other conclusion than to point to the speaker. It's a very good speaker, but they have a acute sensitivity to bass comparatively. Why is the persistent curiosity.

DavidF
11-01-2010, 10:32 AM
" ...If I turned down the treble and the bass to neutral levels, I doubt I would get the speaker pop on any input ....if the solution were to turn down the bass, I'm afraid I would become pretty uninterested in the speakers all together :D..."

You are telling me that you are overdriving the amp, not the speaker.


" I have had a total of 5 pairs of speakers hooked up to (and cranked to) this amp at home, and ran the 250's on it so my friend could see if he liked the NAD. It has never popped another set of speakers. It's not the amp....or should I say it's not an amp problem. On the other hand since I became aware of this popping we have successfully popped a total of 2 L100T's and 1 L100S's using two different amps/systems, it's not a source problem..."

Amplifiers will react differently to speaker systems depending upon the loads.


" ...But now that I have replaced the cones, it's not just an old woofer problem...

I agree with ya there.


"...though my experience says that deteriorated vented pole piece foam could make it worse. Maybe poor engineering of the vented pole piece is the problem..

Completely disagree with you there.



" ...I believe that it's possible to pop any woofer (though I have NEVER popped any other woofer), this woofer seems particularly sensitive to it. Empirically, I can come to no other conclusion than to point to the speaker. It's a very good speaker, but they have a acute sensitivity to bass comparatively. Why is the persistent curiosity.

I honestly believe you are coming to the wrong conclusions. Everything you are telling me (you prefer high volume of sound, you use tone controls for significant emphasis of the signal, you don't think this popping would be a problem at more moderate sound more neutral sound levels) points to overdriving the amplifier when using this particular speaker system under your preferred listening style. You either need an amp capable of providing much more current or stick with speaker systems that don't stress out the amplifiers you currently use.

pathfindermwd
11-01-2010, 09:41 PM
You are telling me that you are overdriving the amp, not the speaker.



Amplifiers will react differently to speaker systems depending upon the loads.



I agree with ya there.



Completely disagree with you there.




I honestly believe you are coming to the wrong conclusions. Everything you are telling me (you prefer high volume of sound, you use tone controls for significant emphasis of the signal, you don't think this popping would be a problem at more moderate sound more neutral sound levels) points to overdriving the amplifier when using this particular speaker system under your preferred listening style. You either need an amp capable of providing much more current or stick with speaker systems that don't stress out the amplifiers you currently use.


Yeah, I see what you are saying Dave. And, I think you make a very valid point. I did'nt intend to gloss over it, but I see that I did.
It makes sense since the NAD is rated at 150 watts, and the other amp that we used to pop others was rated the same. I did turn on the clip protection on the NAD the other day, it didn't seem to complain while the speakers softly poped, though I am not sure if that means anything.

I guess I didnt slow down enough to think through what you were saying, but I also said the same thing myself too when I said I could be under amping it. Until your last post nobody had made it clear that this speaker has specific power requirements or load considerations, which some corroboration about I was hoping for on a JBL forum. Though I got some input, none of it spoke to the real-world operation of the JBL speaker itself, which to me was the question. Overdriving the amp is a better description of what is happening than under-powering, and the right terminology somehow helps me understand it better. If it's true it's difficult for me to test, I would probably need a amp considerably beefier than mine (say 250 watts) to test against, and that's just not that easy to find or to invest in for these speakers, without knowing for sure. But maybe I'll get a head start on the 250's I'll buy someday. Sorry about being frustrated, but I am glad you made your point so much clearer for me. Thanks for having the patience (or frustration) enough to make it.

Best regards,
Mike