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Old 09-11-2013, 12:43 PM   #1
Suitedfingers
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Connecting My Head To My Cabinet

I am not too familiar with mixing and matching Ohms and I am not sure how I am supposed to connect my Vox Night Train 50 head to my Spider Line 6 cabinet.

On the head, there are two outputs that say, "1 x 8 OHM OR 2 x 16 OHM". There is an additional output that is labeled "16 OHM"

On the Cab, there are tow inputs. An "8 Ohms Right" and "8 Ohms Left" that are stereo. the Left side is also labeled "4 Ohms MONO (using this jack only)".

There are no switches on either the head or cabinet.

My question is: how do I connect my head to my cabinet? Do I run two cables or one?

Thanks!
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Old 09-11-2013, 01:00 PM   #2
Roc8995
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Unfortunately, none of those options allow you to properly match the impedance. Most amps can take a 2:1 mismatch, and some can take a 1:2. Your two options are these:
-Use the 4 ohm left input on the cab with the 8 ohm output on the head. This gives you a 1:2 mismatch, which may or may not cause issues long-term with your amp.
-Use the 8 ohm right input (only) with your amp's 8 ohm output. This gives you an impedance match but leaves one of the cab's speakers unused (or 2 if it's a 4x12). Since you're only using half the cab, it needs to be a 100 watt cab or better for this to work.

Ideally you should get another cab as the one you have just isn't matched properly to your head. Plus, most line 6 cabs use a flat-range speaker which probably doesn't sound very good with a non-modeling amp.

Please make sure you're using a speaker cable and not an instrument cable between cab and head.
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Old 09-11-2013, 01:42 PM   #3
Suitedfingers
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This is kind of what I thought. It's a 4x12, so I think I'll go the route us using half the speakers for now. I don't want to do any damage to my head. I came across this cab pretty cheap and it was only to be temporary, so I'm not too hesitant to part with it. I'll start to look for a cab that is a better match.

Thanks for your response!
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Old 09-26-2013, 03:27 AM   #4
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"An "8 Ohms Right" and "8 Ohms Left" that are stereo. the Left side is also labeled "4 Ohms MONO (using this jack only)"

Going by this, it sounds like you have 2 - 8 Ohm speakers in your cabinet. If you wired the two speakers in series, you would have a total of 16 Ohms and you could use the 16-Ohm output on your amp.
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Old 09-26-2013, 03:43 AM   #5
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It's pretty easy to rewire most cabs. Unless you want to only use half of your amp or risk damages to the head.
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Old 09-26-2013, 01:59 PM   #6
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Here is an idea, though i've never tried it so I'm not sure how this would work. If you could get a speaker cable with a Y in it, you could hook your head to both 8Ohm ins on the cabinet. Two 8's make 16 ohms, which would match up with your head and give you all the speakers...

The trick is finding a quality Y cable for speaker cables (i've never seen them... but its a theory).

EDIT: Definitely would go for the rewire of the cabinet though if you are able.
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Old 09-26-2013, 02:20 PM   #7
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Quote:
Originally Posted by cjb2293
Here is an idea, though i've never tried it so I'm not sure how this would work. If you could get a speaker cable with a Y in it, you could hook your head to both 8Ohm ins on the cabinet. Two 8's make 16 ohms, which would match up with your head and give you all the speakers...

The trick is finding a quality Y cable for speaker cables (i've never seen them... but its a theory).



Definitely DO NOT try this, your math is wrong.

If you split it like that it would not make 16 Ohms.

By splitting it like that, you create two paths in parallel. The impedance adds reciprocally in parallel leaving you with 4 Ohms total. Which is exactly why you have a 4 Ohm input for when you use the full cab, because it does that internally.

This would cause a 1:4 mismatch which is very likely to damage your amp.

Like everyone else is saying, probably should just stick to using half the cab for now and find a better cab when you get the opportunity.
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Old 09-26-2013, 05:02 PM   #8
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TJHague,
If the cabinet has two 8 ohm sections, that would combine to 16 ohms and be fine in the 16 ohm amp head slot I would think. I understand I don't know too much here so please explain so i can get the concept.

But yeah, either way just rewire the cabinet or save up for a new cabinet.
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Old 09-26-2013, 05:09 PM   #9
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Your idea was close, CJB, but the execution was backwards. You could rewire the stereo halves of the cab so that they were in series instead of parallel to get 16 ohms mono instead of 4. You would not have the option of using the cab in stereo, but it would indeed be a 16 ohm mono cab. A Y-cable is a really, really bad idea for speaker loads.

The problem with your thought is that you assume that two 8 ohm loads always yield a 16 ohm load. That is incorrect. In parallel, the load is expressed as:
(ohms of each load)/(# of loads), so two 8 ohm loads in parallel is 8/2=4.
In series, the load is expressed by the equation:
(ohms of each load)*(# of loads), so two 8 ohm loads in series yields 8*2=16.

Your Y-cable solution would put the outputs in parallel, so you can see where that idea went wrong. You could indeed rewire the cab to series, though, since as we can tell from the hints on the cab (two 8 ohm stereo or one 4 ohm mono) that it is currently wired in parallel.
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Old 09-26-2013, 05:41 PM   #10
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Quote:
Originally Posted by cjb2293
TJHague,
If the cabinet has two 8 ohm sections, that would combine to 16 ohms and be fine in the 16 ohm amp head slot I would think. I understand I don't know too much here so please explain so i can get the concept.

But yeah, either way just rewire the cabinet or save up for a new cabinet.



When you hook up speakers in Series you can effectively add the resistances up to tally a final resistance so two 8ohm speakers connected in series will produce a 16 ohm driver.

When you hook up a speaker in parallel you effectively reduce the resistance of the combined speakers. So in this case a pair of 8 ohm speakers connected in parallel will then provide you with a 4 ohm unit.

You could essentially spend a lot of time opening up the entire cab and rewiring it to create a proper resistance for your amp. Or you could just plug one side of your current cab into the amp. From what you said your amp is 8Ohm on the RIGHT and LEFT stating its a stereo cab. I can't see why you couldn't plug a cable into one of those channels and then into your 1x8 ohm output on the amp. Sure you will only be utilizing half of your cab, but on the up side you wont be causing any damage to your amp.
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Old 09-26-2013, 06:10 PM   #11
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Quote:
Originally Posted by ne14t
When you hook up a speaker in parallel you effectively reduce the resistance of the combined speakers. So in this case a pair of 8 ohm speakers connected in parallel will then provide you with a 4 ohm unit.


So basically the Y cable would need to be fit into a series instead of a parallel to do it properly. But yeah, I was more so thinking of ways he could utilize all his speakers instead of just one side, but one side would certainly work... just be annoying to lug around all the extra weight for a 2x12. I understand now.
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Old 09-26-2013, 11:02 PM   #12
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I think that if he were to make a box with this circuit in it, it would allow him to use the 16 Ohm output with the two 8 Ohm inputs in series. This just converts the line to two series outputs.

Everything MUST be plugged in if you were to use it, otherwise you would not have a complete circuit and would risk damaging your amp (same thing as running the amp without being hooked up to the cab).

I dunno, it might be overkill, but it's an option to consider. You would probably want to use wire with pretty good shielding on it.

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Old 09-28-2013, 01:08 AM   #13
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Using a Y cable, building a special box or any other oddball stuff is really a bad idea. Just rewire the cab using the impedance rules given above. Match the impedance of your head to the impedance of the cab. Label the jacks appropriately. Done.
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