4301BE - How Do I Connect??

[gullahisland]

I'm the lucky winner of the 4301BEs that were (maybe still are) posted on Craigslist.

My question is...How in the world do I hook them up? On the back, they have the power cords for the built-in 10w amplifiers and two old-style screw terminals which say "low" and "high".

I tried hooking them up to the speaker outputs on my integrated amp and that didn't work.

Then I tried fashioning an RCA cable by cutting the end off and connecting one end to the preamp output on my integrated amp and screwing the bare wire onto one of the terminals on the back of the speaker. That didn't work either.

I promptly tried to log on to this website only to find that it's been down all morning.

I'm chomping at the bit to get these guys hooked up, so any assistance that you can provide will be greatly appreciated.

Thanks!!

[JuniorJBL]

I have never had a pair of "BE's" but try this:

http://www.audioheritage.org/vbullet...84&postcount=6

[gullahisland]

Thanks for the link, but all I got was the following:

I have set set of the powered 4301BE's. They have onboard 15 watt energizers and they absolutely KICK!!



They're supply sound for the garage.


Maybe JBLDog could chime in with how he has them connected?

[JuniorJBL]

That is what I was getting at!


You could send him a PM as well

[JuniorJBL]

I did find this while searching for "4301be" on google


http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5666426189

[gullahisland]

Uuhhh....

I'm pretty sure I could figure out how to hook THOSE up.

[JuniorJBL]

Uuhhh....

I'm pretty sure I could figure out how to hook THOSE up.

Sorry I did not mean to hi-jack your thread but I found it funny that when I did a search that I got a list of stuff that included "JBL 4301BE" and when I clicked on it there she was!

[duaneage]

GREAT WOOFERS!

[mech986]

Brochure:
http://www.jblpro.com/pub/obsolete/4301be.pdf

4301 regular crossover schematic (network 3103):
http://www.jblproservice.com/pdf/Net...%20Network.pdf

Without the 4301BE, schematic, I'm just guessing on the input. Can you find any ground point besides the "low" and "high" input? Can you take any pictures of the engergizer panel? Any power light to indicate power is getting to the amp?

Since it suggests 0.5V are needed for full input sensitivity, I would now suspect the amps aren't working. Check to see if there is any fusing and if so, if the fuses are good, check them for resistance as looking good is no guarantee. Replace if any suspicion at all, cheap to do.

If possible, would suggest unbolt the drivers from the baffle and disconnect from crossovers, noting the wiring color code/connections. Test each driver with output from your integrated amp at low volume, full range with the woofer is ok. For the tweeter, turn the integrated amp's bass control full cut or down and leave the treble control at normal. I suspect (hope?) each driver will be ok, just a hunch.

If the drivers are OK, then you need to check the connections between the amp and the crossovers. I believe the amps are driving the regular crossover of the 4301 but I have nothing to confirm that since there seems to be no link on JBL Pro to a schematic or exploded diagram for the 4301BE. The crossover will likely be mounted away from the amp a bit so look for some caps/inductors by following the wires from the drivers back. Then check for wires from the amp to the crossover, maybe they've parted ways.

Let us know what you find. BTW, did the seller demo the speakers to you and did they know how they were hooked up?

Regards,

Bart

[gullahisland]

Bart,

Thanks for the thorough reply. The speakers were only $40, so I didn't ask the seller to demo them for me, although I learned through our conversation that he had never actually used them. He was a retired engineer (lasers, not audio) and had taken the speakers with him from their usability test lab.

When I connected them to the speaker output on my amp, I got a tiny bit of sound if I cranked the volume up all the way. However, when I connected them using the spliced RCA cable, there was no sound.

Also, I know that the amps are working because if I touch the "high" terminal on the back of the speaker, I get a loud buzz. In that respect, I would say that the amps and the drivers are working.

My primary question is with respect to how exactly the speakers are supposed to be connected.

As I mentioned, they have screw terminals like you would see on an older pair of speakers. When I think of "powered" monitors, I picture a pair of RCA inputs or a 2.5mm or 3/4 inch headphone style jack.

Somewhere in the literature, I saw that the "energizers" (onboard amplifiers) were added to address the poor quality amplification that was used on mixing boards. I don't have any experience with professional gear, but is there some sort of unique cable that is used in this application that would come from the back of a mixing board and end in two small spades?

I'm stumped.

[Zilch]

The RCA output from your preamp has two conductors. One is the shield, and the other the center.

You connect the center to the speaker input terminal that buzzes.

You connect the shield to the other terminal.

Yes, it's an older, but common connection method.

Those are set up as broadcast monitors. They were typically low impedance hardwired....

Amp schematic is here:

http://www.jblproservice.com/pdf/Vin...s/JBL-6001.pdf

How many screws on that terminal strip? How are they marked?

Nevermind, I see now. Center conductor goes to "High."

[mech986]

Thanks for the .pdf of the 6001 amp. I figured it was there somewhere, just couldn't find it.

Agree, should be able to hook up the center (+) lead of a shielded RCA cable from the preamp output to the High input terminal. Then the shield lead would be go to the "low" or ground lead. No unique cable needed as the schematic shows a common, unbalanced + and ground input.

The amp is a nice, basic op amp front end driving a pair of output transistors. Don't much like the electrolytic coupling cap C1 at the input and as coupling caps between stages though (however, that was and still is a common practice in solid state amps). The C1 coupling cap should be changed out for a 5-10uf mylar.

gullahisland, Nice score for $40!!
When you get the hum output from touching the High input, I'd agree that the drivers are probably working. However, I'd bet the amp is working, but not properly, since when you inject signal from known good sources, it isn't "amplifying" them at all. In fact, as you mentioned, the high speaker level input (on the order of 5-15 volts) only came out as very little sound - so the amp isn't working properly for sure. Not surprising for a vintage piece of gear, you have to sort of expect that and perhaps especially since the seller never used it since he took it home.

Looking over the schematic, the first thing that jumps out would be the power supply. It's supposed to run at a nominal +/-24 volts rail but uses capacitors spec'ed at 25 volts - no voltage reserve so over time and age and use have likely failed and possibly shorted. If you are up to it, unbolt the amp from the cabinet and do some troubleshooting. Check to see if any parts look swollen, bent, cracked, or burnt.

Use a digital voltmeter to measure the DC rail volts from load ground (the two caps tied together C13 (-) and C14 (+) ) to C13 + and to C14(-). If they aren't holding at or near +/- 24 volts, the caps need replacing. Use 35 volt rated parts, , 5000uf to 7500uf would be fine and likely today will be smaller. The other caps that would likely need repalcing are C6 and C7 which help to provide zener stabilized power to the opamp. They are 4.7 uf 25 volt tantalum electrolytics and should be replaced with low esr aluminum electrolytics 35 V parts too. Value should stay the same. Observe polarity carefully on all these caps.

Before going any further, check this out and let us know. One advantage is that you could disconnect the internal amp from the crossove and still hook up the passive crossover to your amp and run the speakers.

If this is all too involved, consider sending them to me!! I'd be willing to take them off your hands!! Good Luck!

Regards,

Bart

[JBL Dog]

Thanks for the link, but all I got was the following:

I have set set of the powered 4301BE's. They have onboard 15 watt energizers and they absolutely KICK!!



They're supply sound for the garage.


Maybe JBLDog could chime in with how he has them connected?

Just come out of the "main output" of any preamp. You can also come directly out of a CD player with a variable output. Also, some receivers have a preamp out. Nice score, great little speakers!

[gullahisland]

Thanks for the help everybody.

I have them connected and working quite nicely. There was a switch that I needed to turn in order to activate the pre out.

I cut the ends off of a pair of RCAs and connected them as you all described and they're sounding fantastic.

It does look as though I'm going to need to refoam them as one of the surrounds is already beginning to deteriorate.

These are terrific little speakers with bass that is shockingly good for such a small speaker. Taut and fast.

Two-way designs are just so much more coherent.

Anyway...Thanks again.

[mech986]

Good Job! Be sure to have the refoam done with the foam behind the cone just like the original. Then they should be good to go for another 10 years at least.

You may still consider the power supply cap and electrolytic cap replacements as they are pretty old too and may need replacement eventually. Also, many here like to bypass the crossover caps with 0.1 uf mylars or polycarbonate/polypropylene caps. Otherwise Enjoy!

Bart