problem with twin popping while playing

david berzansky · Post by **david berzansky** » 27 Jul 2002 10:23 pm

so i just got my 73 fender twin back from the shop yesterday where they installed a 15" jbl d130 and the amp sounds just great and i mean perfect great but there is a problem. at an outdoor gig tonight it popped about twenty times. it happened when i played loud and only during picking. i also noticed it when i drop my hand on the strings. the guy i had do the work is very good and i am sure he can fix the problem on monday but if anyone has a suggestion for me, i have another job to pick tomorrow and if i could fix it myself that would be better. i dont know too much about amps but i could work on it easy if i knew what to do. if anyone has an idea in the next fourteen hours or so shout it out.
thanks much
david b

Jim Smith · Post by **Jim Smith** » 27 Jul 2002 10:52 pm

Off hand, I'd say either you've got a bad or no ground in your guitar or your pickups are too close to the strings.

Bill Crook · Post by **Bill Crook** » 28 Jul 2002 1:33 am

David......

Just a shot in the dark here.

You stated that you had replaced the speaker with another one,and that it was poping ONLY on loud passages.

My thoughts and experiences here has been that the speaker is bottoming out, in other words,the basket is hittimg the metal houseing, which is creating a mechanical plus a electronic noise !!

We can attempt to correct this problem by:

1) Reversing the leads to the speaker, thereby makin' the basket drive outwards instead of inwards (and bottoming out). the drawback to this is that over a period of time(years),this may cause the voice coil to rip itself from the dust sheild and/or cone. This isn't such a really bad thing, other than it may cause a slight buzzing sound which would be very hard to find,and notice durning soft passages.

2) The replacement speaker isn't really built for the wattage you are useing. Example:

1) Driving a 100 watt device with a 200 watt amp, at a loud volumne.
2) If the JBL speaker was reconed,(before you purchased it) was it's replacement cone at factory specs ??

I think that if you tried several speakers, you will find that the newly installed speaker may not be up to par.

Now, with all that said, I must say that if you drop your hands on the strings, there will be a loud "Thump" noise, This is not to be confused with with a sound pressure only !! There is a marked difference in the sound of a short,loud sound as opposed to a mechanical and electrical "Bottoming Out" of the speaker device.

I do not wish to infer that any Manafucture (brand name) speaker isn't a good one, only that the application may not be correct for the specfice amp. And also as Jim Smith said, your pick-up may be too close to the strings,thereby the strings actually hitting the pick-up as you pick hard. If you didn't have the problem before the change of the speaker, I wouldn't think this is your problem.
[This message was edited by Bill Crook on 28 July 2002 at 02:38 AM.]

Wayne Brown · Post by **Wayne Brown** » 28 Jul 2002 3:54 am

i agree with bill it sounds like your clipping the speaker not good if your not carefull you'll burn out the voice coil

wayne[This message was edited by Wayne Brown on 28 July 2002 at 04:55 AM.]

John Bechtel · Post by **John Bechtel** » 28 Jul 2002 6:25 am

I think you can relax on the idea of too much power for the speaker! A '73 Fender Twin Reverb amp. would only have been rated at approx: 50 to perhaps 80 Watts. I would tend to go with the 50 Watts on an amp. that old! If it's a black face chassis, you can be certain it's not more than 50 Watts! If your speaker wires are on the wrong terminals, this may cause the problem you have, but; if the wires are right, your problem may very well be at the guitar. Remember, when you look at the speaker from behind the amp, the + is on the left and the neg. is on the right or a red dot indicates + (positive) Hope this helps. To Edit Here; I recall having problems, years ago, first with a Fender Concert amp. Now this was a 40Watt amp. w/4-10s. I thought I would really knock everyone out by replacing the Jensens with 4-10" JBL's! The problem was that I got a lot of distortion because, I was over driving my pre-amp. trying to push 4-10" 100Watt speakers, and just didn't have the power to do it!I had an older Twin with a 15" JBL back when Lloyd Green was using one, that would also distort if driven too hard. I'm pretty sure they were 50Watt amps. at that time. I had a Fender Twin that I bought in Honolulu in 1980, and that's just about the time they went to,I think; 100Watts. I replaced the stock speakers with (2) K-120 12"JBLs and that was still, I believe; the best sounding amp. that I've ever owned. I still have a tape that I recorded on the job using that amp. about 1981 or '82. Hope this gives you hope! "Big John" Bechtel, Nashville, TN.[This message was edited by John Bechtel on 28 July 2002 at 09:14 AM.]

david berzansky · Post by **david berzansky** » 28 Jul 2002 8:19 am

thanks to all of you that responded. it definately is not the strings hitting the pickup although that is exactly what the popping sounds like.
i bought the speaker from a fellow forumite who assured me this application was perfect and that the speaker had been reconed to factory specs so i would hate to think it was the wrong speaker for the job. the amp does however say (where the speaker plugs in) 135 watts rms.
here is what i am hoping on. the speaker wires are connected as follows, white wire to black connecter, black wire to red connecter. someone tell me this is wrong and i will be very happy. thanks again
david b

Earl Erb · Post by **Earl Erb** » 28 Jul 2002 8:32 am

According to the Fender Amp Field Guide the Black Face Twins were made from 1963 to 1967 and were all rated as 85 watt amps.The Silver Face era went from 1968 to 1982.If you have a silver face between 1968 through 1976 the amp is rated at 100 watts.The power went up to 135 watts in 1977 through 1982.In 1983 to the present time Fender went back to the 100 watt configuration.Even the later Evil Twin from 1995 was only a 100 watt amp.The speakers Fender used in any of these amps were very efficient and could handle the load.
During my musical career I have owned a Black Face(1963)and a Silver Face(1968) and were both great amps.My Silver Face was equipped with JBL D120's.
I just recently bought the Black Face Fender Twin Reverb 1965 Reissue Amp with stock speakers and boy its as good as its grand daddy from that era.Fender has been making the reissue since 1995.
David,I think because your amp had to be completly disassembled to put in a new sound board to except the 15" speaker, my impression is there is a bad ground or loose connection or even a cracked or broken solder joint from the handling of the amp during the install.
I agree that if the D130 is a recone and was not done properly could be the problem but I am going to stick with the amp being the problem.
I own a 1973 Sho Bud Single Channel Amp equipped with the same JBL D130 and have never had a bit of trouble with this speaker after all these years.I just recently had this amp gone through and it works as well as the day I bought it in 1973.I will be anxious to hear what you find out what the problem is.

Earl Erb · Post by **Earl Erb** » 28 Jul 2002 8:44 am

Like I said earlier,if your amp says it is 135 watts than it's not a '73'. Fender did not up the watts to 135 until 1977.
I just checked the speaker wires on my Sho Bud with the D130 and the black wire is going to the black terminal cap on the speaker and the white wire,in my case its green,is going to the red terminal cap on the speaker.

Reversing the polarity on a speaker is not a good thing.

david berzansky · Post by **david berzansky** » 28 Jul 2002 9:03 am

yeaaaa! i will switch them out and hope that was it all along. i wont know if that fixes the problem or not until i get to the job and start pickin because i cant really turn it up that loud here at home. i will certainly let you guys know how it turns out.
the gal i bought it from told me it was a 73 but i guees she was wrong about that one. i understand its not easy to date these things either right? when i bought it there were two celestion vintage 30's in there and it sounded horrible for steel. i have never sounded as good as i did last night with the new speaker so i hope it all works out.
thanks again guys your the best!
david b

Earl Erb · Post by **Earl Erb** » 28 Jul 2002 9:59 am

David, according to my source the speakers you took out of your Twin were not being used by Fender which tells me someone put those in after purchase. I really wanted to by a 135 watt Twin but the people that have them want too much for them.It's a great amp,especially with the JBL's.Your amp definately is between 1977 to 1982 and finding the month and year of manufacture has to do with code numbers on the transformers,chassis amp serial number and sometimes on the tube chart inside the amp cab.It's a pain but it can be done.

david berzansky · Post by **david berzansky** » 28 Jul 2002 10:07 am

yes they were definately not factory speakers. she told me the previous owner had blown out the originals. you have narrowed down the years and thats good enough for me. all i know is that i finally have a really great tone and that makes me play better and thats all there is to it! thanks again
david b

Earl Erb · Post by **Earl Erb** » 28 Jul 2002 11:51 am

Your welcome.

John Bechtel · Post by **John Bechtel** » 28 Jul 2002 7:13 pm

Here's the kicker, as though enough hasn't been said, you can all have a good laugh, but; if all else fails, have your tubes checked. There is a possibility you may have a bad 12AX7! Now, go ahead and laugh at a guy who admittedly knows nothing about electronics! But don't ignore the possibility. Thanks, John

Earl Erb · Post by **Earl Erb** » 28 Jul 2002 7:41 pm

John,my long time friend,very good point.Yes,tubes can cause havoc and it wouldn't hurt to have them checked if all else fails.

Great seeing you at the jam and I enjoyed your playing.

Craig A Davidson · Post by **Craig A Davidson** » 28 Jul 2002 7:41 pm

The best way to check polarity is to touch a nine volt to the terminals. When the speaker jumps forward where positive is on the battery that's positive on the speaker. If the speaker jumps back it is just the opposite. I hope I explained this clearly. I use a 1501 widow with my rig and it works just fine.

------------------
1985 Emmons push-pull, Session 500, Nashville400, 65 re-issue Fender Twin, Fender Tele

Donny Hinson · Post by **Donny Hinson** » 28 Jul 2002 11:07 pm

I mention these hints only because no one else has...

Occasionally, the sockets on these old tube amps get loose and require "re-tensioning". It's not a difficult operation, but you might want to have a tech (some one familiar with vintage amps) do it. You have to take the chassis out of the cabinet, and then use a fine pointed instrument (like a knitting needle or ice pick) and add a little tension to the sockets by bending the contacts inwards, slightly. Loose socket contacts have frequently been known to cause noise problems, especially at high volumes.

Also, it could be a bypass cap going bad. These units (just small electrolyte capacitors) have also been known (albeit rarely) to cause the problem you describe.

david berzansky · Post by **david berzansky** » 30 Jul 2002 5:48 am

thanks again guys for all of your help but it still pops. i changed the polarity to what i thought was right and still the pop. everything else i will let the guy who did the work fix because i paid him to do it and its up to him to make it right. i hope he can make it right that is, i cant say enough about how good it sounds otherwise. i will let you know what i find out. i am sure one of you have guessed the right one.
david b

Larry Clark · Post by **Larry Clark** » 30 Jul 2002 6:56 am

This is an excerpt from the JBL enclosure information manual referring to the K130 JBL which was the replacement of the D130.

"Some musicians, however, prefer the sound characteristics of an open-back box. If a K series loudspeaker is installed in an open enclosure, the maximum power applied to the speaker should not exceed 50% of its RMS rating. For example, a K130, which is rated at 125 Watts RMS, should have no more than approximately 60 Watts RMS applied to it when mounted in an open-back box."

Ken Fox · Post by **Ken Fox** » 30 Jul 2002 7:56 am

A few things to consider:

A JBL is only good for about 60-80 watts, I read that on an interview on the net that was done with the original designer! There load test was a 60 watt amp, cranked, and that would burn them out! A 135 watt twin can kill this speaker. A 1501-4SB is more in order (350 watts continous).

Your guy had the polarity right! JBLs are phased backwards. Red is negative and black is positive. Use the 9 volt battery to prove this out. Battery (+) to black and battery (-) to red should cause a forward movement of the cone (reverse for a normal speaker)

Hope that helps. I have worked on many a 135 watt Twin amp. They can put out at least 100 watts cleans to a 4 ohm, 200 watt dummy load. Be careful! Another problem you will have is finding power tubes that can handle the 500VDC or more on the plates of these amps! Most new tubes can not take it! I tried the 6L6WXT+, Sovteks. They can handle the voltage, but I had a 50% fail rate on two sets in two different Twins. The Ruby tube, 6L6GCMSTR is touted as the tube that can handle the higher plate voltages at this time.
I have also heard that same sound when pushing Twins with 2-12" JBLS! I temporarily tried a 15" BW in a Nashville cabinet (via extension speaker cord and disconnecting the JBL's). The BW don't do that at all!

Ken Fox · Post by **Ken Fox** » 30 Jul 2002 8:02 am

The comments above about preamp tubes and sockets are very valid. I had to finally replace two tube sockets in my 1966 Deluxe, at high volumes the air pressure from the speaker would move the tubes and the dirty sockets would make that awful sound. Cleaning and retensioning did not help. These tube sockets would make the noise by just wiggling the tubes around. New sockets fixed it!

david berzansky · Post by **david berzansky** » 30 Jul 2002 9:04 am

here again thanks for the input guys. if it makes any difference, i didnt have the amp totally cranked but it was loud. i thought i had done enough searching and asking and had determined that it was the right speaker for the job. it sure sounds right man i would hate to hear the amp was giving too much power to it. at this point, there is so much info here i will have my amp doctor read this thread and sort it out.
thanks again
david b

david berzansky · Post by **david berzansky** » 28 Aug 2002 8:48 am

just a quick follow up for those of you that chimed in on this one. i had my amp tech read this thread and he thought there was a lot of good suggestions and he explored all of them. unfortunatly he decided the problem was the speaker. he says it is old and has been fatigued to the point that it is able to travel too far back and this is where the pop comes in. i did however buy the speaker from a fellow forumite and he has agreed to take it back so all is not lost. i am trying to find another 15" d 130 because that sound was it! thanks again
david b

Earl Erb · Post by **Earl Erb** » 28 Aug 2002 9:39 am

David, why don't you consider reconing instead of another speaker? It might be cheaper.

My Sho Bud Amp is almost 30 yrs old with a JBL D-130 and I had it reconed about 20 years ago and it plays just like the day I bought it.

Joe A. Camacho · Post by **Joe A. Camacho** » 28 Aug 2002 10:28 am

Hey David,
Take it to Tim Pinnel at Top Gear on University. He's an old friend and he just black-faced my '69 Twin and swapped out the 2-12's with a Weber 15, sounds incredible. His number is 619.464.4969 tell him that I sent you, he's definately the best fender amp guy in town.

david berzansky · Post by **david berzansky** » 28 Aug 2002 2:50 pm

earl,
when i looked into having it reconed, i found that they wanted more to recone as to pick up another one. if i dont have any luck finding another one then i certainly will have it done.
joe,
tim has had the amp for about two or three weeks now and your right, he's good. are you still pickin on that sho bud? the difference in tone when i changed the twelves out with the 15 in combination with the sho bud tone is night and day.
thanks guys
dave