JBL Control 5 repair.

muertopvb

Novice Member
Hello Everybody. I'm a total amateur who enjoys picking up speakers when I see a good deal. I was given a pair of JBL Control 5 Studio Monitors 4 ohm. I wouldn't mess with these, but they look new. They virtually look like someone got them, blew them or whatever, then forgot about them. I've always wanted to have a pair of these, so I thought it worth my while to make an effort at repair. So there is sound coming out of both tweeters. No sound coming out of the woofers. They both also have not a mark on them. When I connected a 9 volt to the speaker wires, the woofers crackled. There is a fuse on the crossover circuit. I have not pulled the speaker apart yet. So two JBL Control 5, they look untouched. No sound out of the woofer. I would appreciate some education and advice.
 

BlueWizard

Distinguished Member
I would suggest you contact JBL to see if they can give you an estimate on repairing the speakers, or perhaps replacing the drivers.

https://www.amazon.com/JBL-CONTROL-Compact-Monitor-Loudspeaker/dp/B000U29P5O

If you feel you are handy enough, the remove the Bass Driver and look inside. You can test the individual drivers with a 1.5v AA or AAA Battery. Connect wires to the battery, and touch those wires to the Driver Terminals. If you hear a click, then in the most basic sense the driver is working.

Keep in mind this 'click' only occurs when the battery make and breaks contact, you will hear nothing with the battery connected. Though with the battery connected current will still flow, you want to avoid having the battery connected for any length of time. Again, make and break contact several times and you should hear the speaker "thud" or "click". That is a primitive test, but it gives you a basic sense of the drives ability to function.

Next, there many be a fuse inside, typically on the Crossover Board. Check that this fuse is still good.

Also, while open, check for any loose wires or broken connections.

Look at the Crossover components. Typically there is very little that can go wrong with a Coil of wire, but Capacitors can fail. If any of them are deformed or bulging, they probably need to be replaced, which can be done easy enough if we can determine the value of the Capacitor.

Here is an example of a typical crossover just so you have some idea of what they look like -

Speaker Crossover, 2 Way, 3500 Hz, Linkwitz-Riley, 4 or 8 Ohm, A-1303

The Yellow somewhat cylinder looking objects are the Capacitors. The Coil of wire is obviously a Coil. The Black Object with the Gray Bar through it is also a coil, an Iron Core Coil.

Capacitors can also be vertical or horizontal Cylinders like these -

https://www.amazon.com/Qianson-Ajustable-Frequency-Distributor-Crossover/dp/B01IZ7JF2I

https://www.amazon.com/2-WAY-Replacement-Speaker-Crossover-Watts/dp/B00AF021NY

Check those aspects out, and let us know what you find.

Steve/bluewizard
 

BlueWizard

Distinguished Member
If the woofer crackles, but does not give any level of sound, I would suggest that they have been dropped and the baskets have been knocked off centre - jamming the speaker. ...
This is somewhat easy to test, spread your fingers uniformly around the Bass Driver Cone and press inward. Their should be tension on the Driver Cone, but it should move, and it should move quietly with no scraping or rubbing. If it does scrape or if you can feel it rubbing, then the cone needs to be replaced. Best get the original cone, but it does not cost much to have the cone replaced. Certainly worth checking into.

Check with Wilmslow Audio, they do speaker repair, and can probably get original equipment cones to replace the existing one.

Speaker Repair, Speaker Kits, Loudspeaker Repair, Kits and Drive Units, Subwoofer Amplifier Kit

There are other place in the UK that do Surround and Speaker Cone Repair, but this is the only one I can think of off the top of my head.

Steve/bluewizard
 

muertopvb

Novice Member
Hello all,
Well, thanks for all the advice. I built up the courage to take the speaker apart. Everything looks good, except for the fuse. The fuse has a break in the filament. The woofer responds when connected to a 9 volt. Nothing on the crossover looks out of the way, as far as I can tell. I'm going to upload a picture oh the fuse. It was hard to get a good pic, but it is obvious that the fuse is blown. Maybe they were dropped. I don't know. Now the question is: Is it a big fix? Is it something I could do. I did find the fuse online. I think its an "sk3" fuse.
 

Attachments

noiseboy72

Well-known Member
Easy to replace, but I think you have to solder them in.

To test if the rest of the speaker is OK, just bypass the fuse with a bit of wire. If all works, happy days!! I only say this as it is quite rare for the fuses to blow unless the speakers have been seriously over-driven. If it works, then you can replace the fuses and restore the connection.
 

muertopvb

Novice Member
Okay, so I bypassed the fuse with a piece of wire. closed up the cabinet, connected the Miles Davis, and out came the sweet sound of both drivers, clear as a bell. I just about fell over. I could not believe it. Next step. Do I learn how to solder a new fuse? A fuse is less than $10. I hate to take it in at this point. Suggestions?
 

muertopvb

Novice Member
Apparently, the fuse is attached with some kind of paste. Can you cut the pigtail at the fuse leaving the tails? Then solder the pigtails on the replacement fuse to the tails that were from the blown fuse. I read on a prosoundweb forum that the paste is for vibration.
 

noiseboy72

Well-known Member
Yes, just cut and solder. You can then use either some silicone or just good quality tape to hold it in place.
 

BlueWizard

Distinguished Member
I don't think that is a fuse, I think it is a light bulb. This acts as a buffer to protect either the Tweeter or the Speaker in general. But you are right, it is bad, and needs to be replaced.

You say the fuse, and bulb or fuse, it servers the same purpose, is £10, is that directly from JBL?

Looks like a very easy problem to fix. It could have been worse.

When you looked up the fuse, is there any chance they gave you the specs. Typically just a current rating, and perhaps - standard or Slow-Blow.

If you want to fuss with it, you could probably replace it with a glass fuse like this -

glass fuse UK - Google Search

And there are holder for these glass fuses; a few different types -

https://www.amazon.co.uk/MultiWare-Inline-Holder-Waterproof-Connector/dp/B0773M6BKH

Inline fuse holder | 5 x 20mm - 6 x 32mm | Quasar Electronics

5PCS Panel Mount PCB Fuse Holder With Cover For 5x20mm Fuse 250V 10A ESUS _UK | eBay

Fuse Holder Chassis Panel Mount 5mm x 20mm AC Mains Glass Fuse Screw UK A305 | eBay

Using one of these various types of fuse holders would make replacing the fuse in the future much easier.

Steve/bluewizard
 

muertopvb

Novice Member
Looks like I better learn how to solder. It doesn't look that difficult to solder two wires together. There are countless videos on youtube. I think I'll do it myself. If I take the crossovers into an electronic shop, who knows what I'll be charged. I can buy a soldering iron pretty cheap. Solder and flux right? I can weld but never tried soldering. I'll let you know how it turns out. Looks like I missed a bullet with it only being the fuses. I'm shocked because nothing ever goes my way. Think I'll buy a lottery ticket.
 

muertopvb

Novice Member
Yes, you are right. They call it an "sk-3 protection lamp". That is it. The lamp is sold at a few places. SimplySpeakers, Ebay, etc. They say it is a genuine JBL protection lamp. Should I check into getting it from JBL?
  • Specs: Watts: 27W, Volts: 12.8V, Amps: 2.1A, Finish: Clear, Shape: T3, Base: 3" leads, Overall Length: 1.7", Filament: C8 / Single coil axial filament
 

Attachments

muertopvb

Novice Member
What I don't understand is if the protection lamp protects the high-frequency driver(tweeter). Why was it the low-frequency woofer that was not working?
 

noiseboy72

Well-known Member
I seem to remember that the fuse protects both drivers.

They work in 2 ways. No. 1 as a conventional fuse that will pop if the speaker is grossly overloaded and no.2 as a lightbulb - which increases in resistance as it gets hot. This reduces the power that the drivers can demand and provides long term protection against moderate over driving.

Replace it like for like to retain the same characteristics, as a fuse is zero ohms and these lamps are not.
 

muertopvb

Novice Member
Is there an alternative to soldering? In other words, can you connect the pigtails of the replacement lamp to the clipped pigtails on the crossover without soldering them together?
 

muertopvb

Novice Member
Okay, I get it. That's what I was trying to get at. Insert pigtail and tighten the screw. Should the connection be covered in tape or anything?
 

muertopvb

Novice Member
That is exactly what I wanted. A way around soldering. I've placed my order for the terminal strip, and the JBL protection lamps. Thanks to noiseboy72 & Blue Wizard I think you two have saved me a bundle of money. Thanks for helping me turn two lemons into lemonade. I will post pics once I've finished.
 

muertopvb

Novice Member
I wanted to get back to to the forum. I got the terminals that were suggested. It took a while to get here. Apparently, they come via Royal Mail/USPS. Anyway, they looked the right size. I took apart both Control 5's and snip. Installed the new protection lamps. I'm glad to report that the speakers sound flawless. Of course, I'm deaf in one ear and can't hear out of the other. But they do sound good. So I got a pair of JBL Control 5's free of charge. It cost less than $15 to repair. That makes them sound even better. Many Thanks to noiseboy72 & BlueWizard for your advice. I would not have even attempted the fix on my own.
 

Attachments

Kev181

Novice Member
Hi guys, I was experiencing the same symptoms as @muertopvb - And low and behold the very same issue. Upon checking the crossover, the lamp has blown. So want to thank you guys for the advice on here it helped me diagnose the problem within 5 minutes & have the parts ordered.
 

oldcootstereo

Active Member
Here's hoping that using lamps for "protection" is a thing of the past... turns out there is research on this, but I'm not paying for the paper (not my circus, not my monkeys). But the last sentence in the precis is fairly damning.
"Incandescent lamps have been used for over fifty years as loudspeaker protection devices, but a large amount of misinformation about them exists. The author measures static and dynamic parameters of over thirty types of auto lamps, as well as tests some types for consistency between manufacturers and production. The results contradict a lot of the common wisdom about using lamps for protection and show serious linearity problems even at low operating levels."
AES E-Library » Lamps for Speaker Protection

Nothing more fun than setting a cat amongst the pigeons. Ya, I'm a bit of a :devil:.

Considering there are so many threads about the finer points of impedance, timing and the like affecting sound, how does having a variable resistor in the circuit not affect the sound quality? Given these JBL's were designed to use bulb protection, perhaps the JBL engineers calculated/tested to be sure the negative effects were minimal. Or not? How would we ever know? I find it interesting that Toole never broached these items in his book/articles.

Could this be a loading factor that upsets some amps more than others, making "pairing" a bigger issue than it might otherwise be?

Inquiring minds want to know...
 

oldcootstereo

Active Member
From what I've been able to gather, turns out light bulbs are a common protection strategy in live sound reinforcement systems, hearkening back to when a shorted/open speaker or crossover component could then quickly fry tube amps or older semiconductor amps. Live reinforcement often involves massive power output, where compression/non-linearities in bulb dynamic characteristics is often not as much of an issue when compared to home reproduction systems.

Much of the debate/info I could find online on this revolved implicitly around "there wasn't anything better/cheaper", so bulbs were used and mostly not mentioned. But musical instrument and sound reinforcement amps/speakers are very different tech than stereo/AV/HT sound reproduction gear. Anyone who has tried to put an electric guitar directly through a stereo can tell you it simply doesn't work well, even if impedance is matched.

Again, given all the noise audio purists make about minimal component signal-path and avoiding any potential non-linearities in said circuitry, I find it interesting how little solid info is out there on protection bulb characteristics affecting sound quality. Light bulbs age with repeated heat/cool cycles, so the resistance/inductance/capacitance characteristics will change over the years. Maybe the design assumption was the whole speaker would wear out and be replaced before the bulbs aged so much as to be noticeable? And interesting that stereo/AV/HT speaker manufacturers aren't up-front about which products use bulbs as protection.
 

Similar threads

Latest threads

Top Bottom