OK.... A little OHM HELP ! ! !

[moeroncuban]

Hey everyone,

I need some OHM schooling here ! ......

I'm currently running a 4x10 cabinet @ 8ohms with a GK 1001 RB-II amp. I just aquired another 4x10 cabinet which is rated @ 4 ohms.

Is it safe to run both of these cabs together -OR- will I risk deep-frying my amp if I run these two cabs simutaneously ?

And if the latter is so, can I rewire the 8 ohm cabinet to make it a 4 ohm cabinet to balance the power output?

As always, I really appreciate all the input... opinions, thoughts, suggestions and instructions!

Thanks in advance brothers AND sisters out here in TB land !

peace,

moeroncuban

[mmbongo]

A) That would present a 2.6 ohm load on your amp = not good.
B) Even if the amp could drive that load, it would sound like crap because the 4 ohm cab would get twice as much power as the 8 ohm

In other words, trade the 4 ohm cab for an 8 ohm or just use the 4 ohm cabinet and sell the 8 ohm. You cannot rewire the cabinet.

[SurferJoe46]

There's no place like Ohm - huh?

What's the lowest Ohm rating of your amp? That's where you need to start - but I bet it's at about 4Ω - right?

A 4 and an 8 add up to 2.67Ω. But you're gonna be mis-matched at best.

So if your amp can do 2Ω, then you're in Fat City. If not, then your amp is in Smoke City.

[moeroncuban]

Either or......That's what I kinda figured ...

Thanks brother !

[SurferJoe46]

Well - it's POSSIBLE to rewire both cabs to 8Ω internally I bet and then together they will be 4Ω.

Let me rephrase that: IF you have, say 4 x 8Ω drivers in the cab, then you can get that cab to 8Ω by wiring pairs of drivers (1 x 8Ω +1 x 8Ω = 2 x 4Ω) in parallel - then wire both parallel pairs in series. (2 x 4Ω + 2 x 4Ω in series = 8Ω).

You need to see what the Ohm rating of the individual drivers in that low-Ohm cab are though first.

If you've got 4 x 16Ω drivers in that one cab - then you are at least partially screwed.

There are other combinations available - but they need to have the actual value of the drivers stated by you to make any firm decision for ya.

[Eric Moesle]

That's incorrect advice. If the 4-speaker cab is already 4 ohms, it CANNOT, under any curcumstances, be wired to be 8 ohms regardless of what the individual drivers are.

[SurferJoe46]

You can have 4 x 16Ω and get 4Ω or 16Ω

You can have 4 x 8Ω and get 2Ω or 8Ω

You can have 4 x 4Ω and get 4Ω or 16Ω

I understand that with 8Ω drivers, the numbers won't crunch right - but we don't know the real value of the drivers yet.

I think that's right - gotta get my medicine now.

But I concede your point if the cab is rated at 8Ω - it won't work.

[SurferJoe46]

EDIT : Ooops! I can see that if the drivers are 4Ω each, then they can be wired internally in parallel as pairs and then in series to get to 4Ω

So if we have 4Ω drivers =

2 x 4Ω in parallel = 2Ω, and then the two 2Ω in series = 4Ω

But you're still correct.

[kawika5150]

I was in the same predicament. Had a 410 4 ohm cab and wanted an 8 ohm 210 but figured more power would be going to the larger cab resulting in a mismatch or "unbalanced" sound. My amp could handle a 2 ohm load, but it was not in my best interest to run that configuration. I picked up another 4 ohm 210 and it was just fine.

All this being said, I'm getting rid of BOTH cabs for two 8 ohm cabs in the event I want to add another one down the road.

[Stumbo]

the Gallien-Krueger 1001RB-II 700/50W Biamp Bass Head. How about running the 4 ohm cab for the lows and the other for the highs. Might sound pretty good. Balance out the tone and there you go.

[GrowlerBox]

Originally Posted by kawika5150

I was in the same predicament. Had a 410 4 ohm cab and wanted an 8 ohm 210 but figured more power would be going to the larger cab resulting in a mismatch or "unbalanced" sound. My amp could handle a 2 ohm load, but it was not in my best interest to run that configuration. I picked up another 4 ohm 210 and it was just fine.

All this being said, I'm getting rid of BOTH cabs for two 8 ohm cabs in the event I want to add another one down the road.

You would actually have been better with the 8 ohm 210 in combination 4 ohm 410 (did we not have this conversation at the time??) -- the 410 cabinet would indeed receive twice the power output that the 210 did, resulting in even power distribution amongst all 6 speakers, which is far more important. All of this relies on your amp being able to handle a 2.7 ohm average impedance, of course.

[kawika5150]

Originally Posted by GrowlerBox

You would actually have been better with the 8 ohm 210 in combination 4 ohm 410 (did we not have this conversation at the time??).

Yes indeed, we did have this conversation.
The price for the NEOX was just too good to pass up. I've played with these in a live setting and they sound really good. It's also nice to know that I have a lot of spare headroom if necessary.

Btw, I was thisclose to getting an 8 ohm cab at the time after reading your advice.

[will33]

A LITTLE OHM HAARP..........


AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

Hey, I have to have 2 talkbasses open to do that, that must qualify as some sort of OMG!

Now back to what really matters, ....... mexican food.

[lbwdog]

Originally Posted by Stumbo

the Gallien-Krueger 1001RB-II 700/50W Biamp Bass Head. How about running the 4 ohm cab for the lows and the other for the highs. Might sound pretty good. Balance out the tone and there you go.

No good! Although it would match impedance wise, you would get nothing out of the 50w but 5kHz and above, which the 10" drivers could never reproduce.

Now, in the 800RB, you could benefit, since it has an adjustable crossover from 100 Hz to 1 kHz, plus a full range switch, which allows you to run an 8 Ohm cab from the "Hi" (100 w.) side, and a 4 Ohm from the "Lo" (300 w.) side.

[moeroncuban]

Ok brothers........ ( thanks fir ALL the input, it's all very educating! ... really ! )

I did think of another configuration...... So please hold ALL laughter until the show is over ! LOL :^)

Before getting rid of any cabinet, since I do split my cabinets on stage ( one behind me and another behind our drummer ) couldn't I just buy a smaller head, like one of those light weight GK's to run the 8 ohm cabinet and run in stereo out of my chorus pedal?
Sounds desperate I know.... But just a thought.....

Thanks SO much for ALL the information and technical bickerings..... HA ! :^)

Peace !

[lbwdog]

Originally Posted by moeroncuban

I did think of another configuration......

Before getting rid of any cabinet, since I do split my cabinets on stage ( one behind me and another behind our drummer ) couldn't I just buy a smaller head, like one of those light weight GK's to run the 8 ohm cabinet and run in stereo out of my chorus pedal?

You wouldn't even have to use the chorus pedal. You could run from the "effects (pre-amp) out" of the 1001, into "effects in" of the new amp. That way, you would be controlling volume and EQ with the 1001, and just using the power amp section of amp #2.

[DWBass]

Just cancel the order and re-order for an 8ohm cab. Problem solved!

[moeroncuban]

Lbwdog!
Bro........that makes awesome sense!!!!
I can just use a power amp with enough juice to run the 2nd cabinet and control it from the 1001. That's GENIUS !

Thanks ! :^)

[lbwdog]

Originally Posted by moeroncuban

Lbwdog!
Bro........that makes awesome sense!!!!
I can just use a power amp with enough juice to run the 2nd cabinet and control it from the 1001. That's GENIUS !

Thanks ! :^)

Aw Shucks! Now I've got a warm, fuzzy feelin'......

[moeroncuban]

no really... that's clever. I don't wanna get rid of any cabinets ,NOR my amp. So by just running another amp nothing fancy will suit my needs. (For now at least until G.A.S. rears it's ugly but welcoming head!)

I'm now in search of a pwr amp !

Thanks again bro !

peace