#1
Short rant: I needed a bass amp on really short notice and made a run to GC without doing any research (Doh!). After some testing I settled with a Markbass - Little Mark Tube 800 (500W RMS @ 8 ohm, 800W RMS @ 4 ohm). Because of back-surgery, I decided to get two of the light and small New York 121 cabs (400W RMS, 8 Ohm). I asked if the power and impedance were compatible, which the store guy confirmed and added that since I had a head that was 800W and two cabs at 400W, I would get the full 800W at my disposal, which sounded good to me.

After a little research, I’ve concluded that the guy in the store didn’t know what he was talking about, but I’m still confused:

1) I read in the bass FAQ that it is important that the cab wattage exceeds the amp. Does it make any difference if it's two cabs?

2) I also read that I can use the two 8ohm cabinets to draw the full output from the amp if I put them in parallel. On the back of the amp, I have two jack ports for output; one labeled speaker out and one labeled class 2 wiring. Would I use these two ports for parallel wiring?

3) Can I make this work without risking blowing the cabs, or do I need to go back to GC and find some different ones?

Any help would be much appreciated.
#2
Short rant: I needed a bass amp on really short notice and made a run to GC without doing any research (Doh!). After some testing I settled with a Markbass - Little Mark Tube 800 (500W RMS @ 8 ohm, 800W RMS @ 4 ohm). Because of back-surgery, I decided to get two of the light and small New York 121 cabs (400W RMS, 8 Ohm). I asked if the power and impedance were compatible, which the store guy confirmed and added that since I had a head that was 800W and two cabs at 400W, I would get the full 800W at my disposal, which sounded good to me.

Sounds good to me


After a little research, I’ve concluded that the guy in the store didn’t know what he was talking about, but I’m still confused:

...wait what?

1) I read in the bass FAQ that it is important that the cab wattage exceeds the amp. Does it make any difference if it's two cabs?
I have no idea what you are talking about, the guy in the shop was right.
(as long as the specs you have written out are correct)


2) I also read that I can use the two 8ohm cabinets to draw the full output from the amp if I put them in parallel. On the back of the amp, I have two jack ports for output; one labeled speaker out and one labeled class 2 wiring. Would I use these two ports for parallel wiring?


1: plug amp into one cab
2:plug cab into other cab
3:play bass with your 800watt amp
4:Profit!!!!!!!!

3) Can I make this work without risking blowing the cabs, or do I need to go back to GC and find some different ones?

Any help would be much appreciated.


again
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
Last edited by gilly_90 at Aug 9, 2010,
#3
Amazing.
Marshall amplifiers are the truest purveyors of rock and roll known to man.

"And give a man an amplifier and a synthesizer, and he doesn't become whoever, you know. He doesn't become us."

Holy crap, check this out!
#4
The concern of the TS is that if he wires his 2 cabs in a parallel circuit (2 8 ohms in parallel is 4 ohms), his amp will be pushing 800W to each cabinet that is only specced to support up to 400W. I thought that was pretty clear.

As for an actual answer, I don't have much experience so I can't tell you. I can tell you I would not fully crank that setup, as you could definitely cause some damage. However I'm not sure how to figure out how far is too far in this setup.
#5
Quote by Lazarus.Bird
The concern of the TS is that if he wires his 2 cabs in a parallel circuit (2 8 ohms in parallel is 4 ohms), his amp will be pushing 800W to each cabinet that is only specced to support up to 400W. I thought that was pretty clear.

As for an actual answer, I don't have much experience so I can't tell you. I can tell you I would not fully crank that setup, as you could definitely cause some damage. However I'm not sure how to figure out how far is too far in this setup.


but they are 400 each... so 800
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#7
which part of 2x400=800 aren't you understanding?

EDIT: that sounded harsher than I meant it. The 800watts of power will be shared between the two cabintes and there will be no power handling problem when they're just connected normally. I agree that it shouldn't be cranked, but I've never had the need to crank the 500W amp I've been gigging with (use it with volume between 3 and 4) so there's no problem there.
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
Last edited by gilly_90 at Aug 9, 2010,
#8
All you're saying is "i don't understand why you're confused" and "how can't you understand this." Feel free to elaborate instead of being brief and cynical.

Wouldn't each speaker be receiving 800w of power when they can only handle 400w?


Maybe I am confused from the research I've been doing on the Ampeg SVT-4 Pro. The specs list...

RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2

Doesn't this mean that if I have to 4 ohm speakers in parallel, working the amp at 2 ohms, both cabs will be receiving 600 watts of power each?
Last edited by Lazarus.Bird at Aug 9, 2010,
#9
Quote by Lazarus.Bird
All you're saying is "i don't understand why you're confused" and "how can't you understand this." Feel free to elaborate instead of being brief and cynical.

Wouldn't each speaker be receiving 800w of power when they can only handle 400w?


read my edit.

and, no. Equal sharing ftw.
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#10
Quote by Lazarus.Bird
All you're saying is "i don't understand why you're confused" and "how can't you understand this." Feel free to elaborate instead of being brief and cynical.

Wouldn't each speaker be receiving 800w of power when they can only handle 400w?


Maybe I am confused from the research I've been doing on the Ampeg SVT-4 Pro. The specs list...

RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2

Doesn't this mean that if I have to 4 ohm speakers in parallel, working the amp at 2 ohms, both cabs will be receiving 600 watts of power each?


the SVT has 2 power amps, which is where the difference lies
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#11
So the Mark amp is listed as "800W RMS @ 4 ohm" so any cabinet in that parallel circuit will share that 800W? How do they decide how much gets what, or is it evenly divided on each resistor (speaker) in the circuit? It's been a long time since high school physics

The Ampeg is listed at 600W x 2, so does this mean each cab will be getting 600W each? I guess this is because the SVT-4 has two separate power amplifiers?

Ah you answered this in your last post. I understand now. So the original TS should be fine with his rig Thanks for the info.
#12
That's my understanding of it. I'm unsure of the physics, just the practicality.
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#13
Thanks for the reply gilly_90 and Lazarus.Bird. I apologize for being slow, but I’m still slightly confused whether the cabs should be wired in parallel or series.

From the bass FAQ: “You can use two 8ohm cabinets to draw the full output from the head. To do this you would wire them up in parallel, using both the speaker outs on the back of your head”. So I get 400W to each speaker and things should be ok?

This is the back of the head:
http://www.markbass.it/immagini.php?id_pro=101&id_imm=61&lingua=en

I assume that the two speaker out connections is what I need for parallel wiring (I’m unfamiliar with the meaning of class 2 wiring)?

Alternatively, I could connect the cabs in series. From the FAQ “If you were to have the cabs in series, their impedance would be 16ohms and would only draw about 30-40% of the output of the head.” So I get less power, but also less risk of blowing the speakers?
#14
parrallel them by doing this:
Quote by gilly_90

1: plug amp into one cab
2:plug cab into other cab
3:play bass with your 800watt amp
4:Profit!!!!!!!!


there are 2 outputs that you can use depending on what type of speaker cable you are using. The 'class 2 wiring' hole is exactly the same as the one above it, just meant for a regular speaker cable.
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#15
I believe Class 2 wiring is just a term saying that it will support low voltage wires. As gilly said it is identical to your speakon output, just a different interface. Don't concern yourself with the class 2 description.

Guitar/bass speaker cabinets are not commonly wired in series, and unless your cabinets have both parallel and series inputs/outputs, the jacks are likely wired for parallel and wiring them in series would involve you rewiring your cabinets or creating your own patch box to run them in series.

Instead of doing what gilly suggested you can also take one output to one cab and the other output to the other cab, assuming the cabs have both 1/4" and speakon inputs. You have an ideal situation where your amp supports 4 ohms and you have 2 8 ohm cabinets. They are practically made to be run in parallel with each other.
#16
Quote by Lazarus.Bird
I believe Class 2 wiring is just a term saying that it will support low voltage wires. As gilly said it is identical to your speakon output, just a different interface. Don't concern yourself with the class 2 description.

Guitar/bass speaker cabinets are not commonly wired in series, and unless your cabinets have both parallel and series inputs/outputs, the jacks are likely wired for parallel and wiring them in series would involve you rewiring your cabinets or creating your own patch box to run them in series.

Instead of doing what gilly suggested you can also take one output to one cab and the other output to the other cab, assuming the cabs have both 1/4" and speakon inputs. You have an ideal situation where your amp supports 4 ohms and you have 2 8 ohm cabinets. They are practically made to be run in parallel with each other.


I agree with everything. The bit in bold is unlikely.
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#17
thanks for the clarification.... I actually thought that plugging amp into one cab
and plug cab into other cab, would be a series connection. I learned a lot today!!
#18
amp
+( )-
cab1
+( )-
cab 2

As stated before, most guitar cabinets have their jacks wired for parallel, as series is uncommon. The diagram above shows an amp connected to one cab, and the cab daisy chained to another cab. This is a parallel circuit, as if you removed cab 2 the circuit would still be complete and would function.

In series cab 2 would have a negative return feeding back into the amp, and if cab 2 died nothing would work, as everything is wired in a line looping back to the original power source.
#19
Quote by gilly_90
1: plug amp into one cab
2:plug cab into other cab
3:play bass with your 800watt amp



Wait isnt this way is connecting in series

shouldnt parallel be both cab connecting to the head
#20
nope, both parrallel
Quote by UraniYum
Fuck you I'm trying to be caring and shit


Quote by Cb4rabid
Okay guys, I have a confession to make. Not really a confession since it's something that's been bugging me for awhile but I've always been in denial about it.

**** you gilly, it's not what you think
#21
Quote by gilly_90
nope, both parrallel


cab->head cab->head is parallel
cab->cab->head is parallel too?

how to connect for series then
#22
Quote by bure82
Wait isnt this way is connecting in series

shouldnt parallel be both cab connecting to the head


If the cabinet jacks were wired for series this would be series, but as I stated most gear is not designed to be run in series. The jacks are wired for parallel. Daisy chaining one cabinet off another will result in a parallel circuit.
#23
Quote by Lazarus.Bird
If the cabinet jacks were wired for series this would be series, but as I stated most gear is not designed to be run in series. The jacks are wired for parallel. Daisy chaining one cabinet off another will result in a parallel circuit.


oh it's the cab design

i have mine like this right now
cab->head
cab->head

this is parallel right

you guys getting me worried
#24
Yes connecting one cab to one amp output and another cab to the other amp output is parallel. This is technically more ideal than chaining your cabs together as the full load isn't put on one wire at a time, but that is mostly a moot point. You also can still use cab 2 if cab 1 dies while playing.