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Looking for help understanding my cab's wiring (Mesa 1516 content)

C

C_nut

Nov 22, 2015
183
113
Finland
#1
Hi all,

just got this beautiful Mesa Boogie 1516 for a bargain. The seller couldn't tell much about it, since he didn't ever really play it.

I'm still not quite sure which 1516 model this is. It has two inputs but no information on the back panel. Today I tried connecting an amp to the lower input after reading somewhere online, that it should be 4 ohms and power the full cab. With this input, only the upper half of the cab made noise.

Can you tell me from the wiring if this cab can be powered using only one input or if it's bi-amp only? If one input is enough, which one should I use? If it's the lower, then looks like the 1x15 is dead.

If it's bi-amp only, is re-wiring this mono and full range possible?

Is it safe to assume, that this cab takes 4 ohm or should I get a multimeter just in case?

Oh, and by the way. The grey wire from the horn goes to a switch that is attached to the front of the cab. I assume it's for turning off the tweeter.

Cheers!
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#2
Somebody has been inside the cabinet and totally screwed up the wiring.

Give customer service a call and see if they have access to the wiring diagram, it's earlier than any diagrams I have access to. Kris might be your best bet, he's more focused on bass product support. Note that customer service is closed on Fridays.
 
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#3
Just a bunch of wires. No help. In order to figure it out, you have to trace through the connections. There may be some sort of crossover board for the top part of the cab...or maybe just an HPF for the tweeter.

I found a couple of images of jack panels. There is variation by generation.
upload_2023-9-27_13-47-27.png


If the jack panel looks like this. The bottom right jack should connect to both sections.

Each of the left jacks should connect to half of the cab.

There is most likely a switching contact, so don't use both sets of plugs at the same time with two different amps. If you do you there is a good chance the amp will be damaged.

My guess is the right plug has the switching contact. So the cab is in stereo mode unless a plug is inserted into the mono jack.

I can't find an image of a jack panel with only two jacks.

I did find one with four jacks.
img_20160806_192119887-jpg.922603

The top right jack is a Thru for the bottom right jack (mono).

A multi-meter would be helpful.

I would start by disconnecting the 15 and check the voice coil. Make sure you document which wires go where, so you can put them back where they belong.
 
#5
Thanks for the replies, guys!

@agedhorse I tried getting help via the online customer service, but I'm not sure if my message will reach Kris since I reside in Europe. If it's not too much trouble (and allowed) would you like to PM his contact information?

@Wasnex thanks for helping out dude. This cab here actually has two inputs. I think they released a bunch of 1516 models in the past. Here is a pic of a similar cab. The difference here is that mine has been upgraded with speakon connectors. I'm waiting for the diagram but in the meantime, if you have time, could you explain what the switching contact does in a cab? I'm still learning.

mesa taka.jpg
 
#6
C_nut said:
Thanks for the replies, guys!
...if you have time, could you explain what the switching contact does in a cab? I'm still learning.
Click to expand...

Since your cab has been changed to speakON, it will not have a switching jack. 1/4" jacks can have a variety of different switching systems. When you insert a plug it changes the contacts to either break a circuit, form a circuit, or switch circuits.

Here is a page that should help you understand some of the possibilities:
Invalid Link Removed

NL4 speakONs have 4 connections. Musical instrument speakers usually only use two of the connections 1+,1-.

A couple of possibilities.
1. Both speakONs are wired to 1+,1-. One speakON is connected to the top section of the cab and one speakON is connected to the bottom section of the cab.
2. Each speakON is connected to both sections. 1+,1- is used for one section and 2+,2- is used for the other section.
 
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#7
Wasnex said:
A couple of possibilities.
1. Both speakONs are wired to 1+,1-. One speakON is connected to the top section of the cab and one speakON is connected to the bottom section of the cab.
2. Each speakON is connected to both sections. 1+,1- is used for one section and 2+,2- is used for the other section.
Click to expand...

Okay, so from my understanding it has probably been wired for bi-amping (possibility nr. 1), since plugging into the left connector only powered the top half of the cab? In which case I'm going to need to rewire the thing anyways if I'm going to use with just one amp. Using an amp with two outputs will probably out of question, right?

Thanks again.
 
#8
I notice that there is a red & black wire twisted together from I think the back panel, they go to a terminal block and then I can see a yellow wire from the terminal block that i can't follow. Where does it go ?
There is this old post that might give you an idea of how things should work, even if the schematic is not fully correct.
https://www.talkbass.com/threads/mesa-1516b-cab-upper-speakers-problem.1237217/

You might have to trace each wire and draw your own schematic of what you have, and please write what pin number that the wire is connected to in the speakon jack as well please, after that someone might be able to help you out with how you can rewire it correctly.
 
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#9
This is why I don’t recommend buying somebody else’s mess.

I believe the 10’s and the HF driver are one section and the 15” driver is the other section.

Is the crossover still present at least?

Does it have a tweeter level control?

Kris and others monitors the on line customer service portal. Give them a couple of days.
 
#12
C_nut said:
Okay, so from my understanding it has probably been wired for bi-amping (possibility nr. 1), since plugging into the left connector only powered the top half of the cab? In which case I'm going to need to rewire the thing anyways if I'm going to use with just one amp. Using an amp with two outputs will probably out of question, right?

Thanks again.
Click to expand...

Yes, you may need to reconfigure the wiring somewhat. Also, AFAIK, you have not confirmed whether the 15 is dead or if the problem is related to wiring.

If it was my cab, I would trace out the wiring and confirm all of the drivers are good. That way you have a good starting point.

Getting an official wiring diagram from Mesa would still be helpful.
 
#13
Tassieviking said:
It would be logical that the 15" is wired to it's own socket, but what worries me is that both Speakon jacks has 2 lots of wires running from them.
Click to expand...

How the speakONs should be wired depends on how the OP intends to drive the cab. Instead of guessing and getting anxious, the OP should simply trace out the connections and decide what can stay the same and what needs to be redone.

IMHO the most concerning part is what sort of crossover network the cab requires, and if it is properly connected. Hopefully Mesa can provide insight on this.
 
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#14
C_nut said:
Thanks for the replies, guys!

View attachment 5203557
Click to expand...

I used to have the 1st version 1516 for many years. The original version had only a toggle switch for the tweeter: hi, off, low.
And it had a single input jack: all the speakers were wired from the jack. The 1st version did not have a split, all speakers were on all the time.
If your cab has a spot for a tweeter toggle switch toward the upper right corner, then its one if these 1st version.

The 2nd version change in the early 90s got the large plate with the three jacks and the tweeter rocker switch.

From what I remember of mine (and the look of your vinyl texture pattern), yours looks like a 1st version.
 
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