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Cables for using combo as a speaker cab.

pingvuiini

pingvuiini

Feb 2, 2009
1,887
7,111
Antarcticus Maximus
www.randychow.net
#1
I have this current combo stack. Markbass 121P with New York 121 cabinet:
MBStack01.jpg


I am getting a new head and want to use the combo as just a cabinet. The speaker connection on back for the internal speaker is a 1/4" jack:
MBSpeakerCable01.jpg


So would I just need the following cable adapter to connect the new head to the internal combo speaker?:
SpeakonQFCable01.jpg

Hopefully it is as simple as that, but are there other potential issues to be aware of with this kind of setup?? Any info appreciated. Thanks!
 
#2
Speaker outs on combo are typically for adding an extension cab. You want to use the combo as a cab-only, so you will need to electrically disconnect the speaker from the amp. That means you will have to open it up.

However, I may be missing something. Is there a label or something in the manual that states the 1/4” is not only a speaker out, but rather is a switching jack and may be used to also run the unit in a cab-only mode?
 
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#3
Coolhandjjl said:
Speaker outs on combo are typically for adding an extension cab. You want to use the combo as a cab-only, so you will need to electrically disconnect the speaker from the amp. That means you will have to open it up.

However, I may be missing something. Is there a label or something in the manual that states the 1/4” is not only a speaker out, but rather is a switching jack and may be used to also run the unit in a cab-only mode?
Click to expand...

Gaugh!! I was hoping that I wouldn't have to open up the combo. I believe that unplugging the 1/4" jack is electrically disconnecting the internal combo speaker from the combo amp as you said (see photo) below. Then I just need to use the Speakon-to-female 1/4" adapter to connect the internal combo speaker to the new head. There is no specific mention on the combo or in the online owners manual that says the combo can be used as an extension speaker. Hmmmmm.

MBSpeakerCable02.jpg
 
#4
It looks like that loose line with the 1/4” is the actual speaker lead. My mistake, I didn’t know what I was looking at in the first pic. My Walkabout Scout is built like that.

The adapter in that first pic has the speakon that fits into a head, and the other end looks right. Depending on what your extension speaker cable looks like will determine if that adapter has the correct speakon on it or not.
 
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#6
Correct, that's the actual combo's speaker cable.

If you use the cable that you posted, it's critical that the metal shell of the connector does not touch any other grounded metal because many amps use a floating (non ground referenced) amplifier topology and grounding this can destroy an amp.
 
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#7
agedhorse said:
Correct, that's the actual combo's speaker cable.

If you use the cable that you posted, it's critical that the metal shell of the connector does not touch any other grounded metal because many amps use a floating (non ground referenced) amplifier topology and grounding this can destroy an amp.
Click to expand...

Would wrapping the metal female shell with some kind of cloth tape work to prevent the grounding that you speak of??
 
#11
I would refit the existing cable with speakon but much longer so it can be the daisy extension to your second cab.

Why? So you never can plug two amps into each other by mistake which is always a horrible risk if you leave the combo amp connected with an available daisy link on its cab.
 
#13
I have done this for testing purposes, and used a 1/4" female-female joiner to connect to the cable to the speaker.

However, I don't know why you would want to do this. The MB power amp is hella powerful (500WRMS) and I think that it has some "voicing" in it to better suit the cabinet and drivers that you will not get with another amp. Might be more trouble than it is worth. Any features you need can be added in the effects loop.
 
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#15
Coolhandjjl said:
It looks like that loose line with the 1/4” is the actual speaker lead. My mistake, I didn’t know what I was looking at in the first pic. My Walkabout Scout is built like that.

The adapter in that first pic has the speakon that fits into a head, and the other end looks right. Depending on what your extension speaker cable looks like will determine if that adapter has the correct speakon on it or not.
Click to expand...
I have done this with my WA 12 cab with just a 1/4" F to F adapter. One end on the cab 1/4" and then just a normal 1/4" speaker cable to the amp (or other cab I guess). A little fiddly but it worked fine on the occasions I used it that way. I'm guessing it would work the same on the MB cab too.

Easy to lose those adapters though, so its good to figure out some way to keep track of them.
 
#16
OK. The new amp head is scheduled for delivery today (yay!), so I am prepping my converted mini stack for the arrival. I got the Speakon to 1/4" female adapter already and I wrapped the metal case with cloth tape as suggested. As usual with mickey mouse setups like I am trying, these things never work out as intended: the adapter cable is only 6" long and won't even reach over the top of the cabinet when connected to the internal combo speaker cable, so I will have to put both cabinets and the head on the floor and hook them up that way. Should still be good enough to test things out though.

The Speakon cable connectors will simply go into the two Speakon outputs in the back of the amp. I believe this is a parallel setup yes?? The label on the one true cabinet says it is rated 400 watts at 8ohms and according to the Markbass website the combo appears to be the same. The new head is rated 800 watts at 4 or 2 ohms, so I should be ok right?? The new head has an ohm switch that I've never seen in an amp before. If this setup is indeed parallel then that would bring down the total ohmage to 4 correct??

Hmmmm. Something just occurred to me: the Markbass combo has a balanced XLR input on the front (top) control panel. Would it be possible to take a direct XLR out (pre-EQ?) from the back of the new amp into that XLR input of the Markbass?? Would that, in essence, create a bi-amp system?? If that would work, I might try that instead of mickey mousing with the speaker cables. And then I wouldn't have to deal with all the math which gives me a headache.

Eventually I do hope to get new speaker cabinets that will work very well with the new head but currently the budget does not allow. (Speaking of which, would a cabinet with a low freq response of 40Hz give me more beef than one at 45Hz??)

Just want to be sure that everything looks ok or if I'm headed for disaster so I don't smoke the new amp or blow the cones. Any advice severely appreciated. Thanks!
StackBack01.jpg
 
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#17
hmm, I checked the Markbass manual and it does not actually say much/anything about the XLR balanced In jack, so it's hard to say what it does ... if it's just a regular preamp input (like the unalanced 1/4 inch input) or a way to bypass the pre and just use the 121p power amp to push the signal from another pre (like your new amp ... don't recall seeing you say what amp it is).

No matter what it is (balanced pre input or balanced power amp input/insert) you won't get a "bi-amp" rig out of that combination. Bi amping is a whole other thing with crossovers splitting frequencies into different cabs usually to divide low frequencies from hi frequencies. Its more than just using 2 amps and setting the EQ on one to be more focused on highs and the setting the other to be more focused on lows.

Perhaps some more experienced MB user can tell you what the Balanced XLR Input actually does. (its odd that the MB manual does not say anything about it other than it's ohms rating).

sorry to hear about the adaptor cable being too short, but that happens when you don't measure the length you really need. bummer!

good luck
 
#19
Thanks for your helpful replies.

IT'S HERE!!! The new head is a Mesa Engineering TT-800. I ordered from Sweetwater and apparently it's quite new to the market and I had to wait several days before they could ship it out. The shipping box is quite stiff and strong, probably strong enough for two full grown emperors to stand on.
Box01.jpg


Checking the contents, there's the owners manual and documentation, a gig bag, an envelope with the power cable and headphone adaptor, a small Sweetwater catalog and some candy.
CheckContents01.jpg


Boy, the amp is light! I had a similarly sized Eden head many moons ago (before D class) and it was much heavier than this. I like the simple tone controls and everything seems quite straightforward, although still not too sure about the O/D symmetry control.
CheckFront01.jpg


If I can find a longer Speakon to 1/4" female adapter this will be the stack setup I am trying to achieve. But right now, for the sake of simplicity, safety and initial testing I am just going to plug the head into the one true cabinet, set the ohmage for 8 and give it a go with the uke bass and my Status Graphite 6 fretless.
Stack01.jpg

Wiring01.jpg
 
#20
I am not too sure what I am looking at. It looks like the adapter can reach from the combo cab to the proper cab, and the cable from the new amp is long enough to reach the proper cab when the amp is in the top and the cab on the bottom. So plug and play, no?!

Those cab inputs are also parallel.
 

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