# 4ohm Amp into four 8ohm cabs?

Discussion in 'Amps and Cabs [BG]' started by bassdude123, Aug 2, 2021.

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1. ### bassdude123

Aug 2, 2021
Hi everyone,

I just bought the „Trickfish Bullhead 1k“ which is rated @4Ohm.

Now to the cabs:

Out of logistical reasons i thought about getting:
—-> this would be 4 8Ohm cabs

Is it possible to use 4 8Ohm cabs with the 4Ohm amp?
What are the downsides?

Im looking foreward to some replies
bassdude123

2. ### Wasnex

Dec 25, 2011
All four in parallel will be 2 ohms, which is below the amps minimum rating and should be avoided.

If you rig up cables that wire all four cabs in in series parallel, the impedance will be 8 ohms.

Two cabs in series (8+8= 16ohms). You will have two series circuits at 8 ohms. Put both circuits in parallel and your back to 8 ohms (16/2=8). ​

3. ### bassdude123

Aug 2, 2021
Okay, can you tell me how much percentage of the power each cab would get?

4. ### Wasnex

Dec 25, 2011
With four 8 ohm cabs in series/parallel, each cab will get 25% of the total power. The Bullhead 1K is rated for 1,000W at both 4 ohms and 8 ohms, so each cab will receive a max of 250W when the amp is producing its rated power.

If you had an amp that was rated for 2 ohms, four 8 ohm cabs in parallel would also share the power equally.

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5. ### bassdude123

Aug 2, 2021
I see.
Thank you very much

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6. ### Thunder Lizard

Dec 7, 2005
Calgary, AB
Great answers. There is the further thought that if you are combining identical drivers, then you will get an even spread of power, however when speakers of different impendences are paralleled together, the lower impedance driver will get more power... electricity always heads for the path of least resistance. This page explains that and a whole lot of related questions in a really approachable way, for my thoughs... https://geoffthegreygeek.com/multiple-speakers-share-power/

7. ### mmbongoRegular Human BartenderSupporting Member

Aug 5, 2009
Carolinas
Also remember that 1000 watts is the ‘maximum’ rating of that tamp with the actual power being around 750 watts.

Trying to do a series/parallel thing is going to reduce power as well. The simple fix is to get two 8 ohm cabinets.

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8. ### bassdude123

Aug 2, 2021
Yes i do not mind losing some power as i am getting portability in return.

As long as i am loud enough:
I play with 2 guitars, vocals and drums...
We are loud but no deafening metal here xD
The greatist gig without PA support would be 100people indoor

Do you think it will be still enough?

9. ### Wasnex

Dec 25, 2011

The specs say the amp produces the same power (1,000W) at either 4 or 8 ohms.

When you hold the power constant and double the speakers, you net +3dB from mutual coupling. This assumes identical speakers.

If you have two speakers at 4 ohms, each cab sees 500W. If you have four speakers at 8 ohms, each cab sees 250W. Cutting the power each speaker sees in half drops the SPL each cab makes by -3dB. However doubling the speakers gives you +6dB from mutual coupling. So -3+6=+3dB net.

The mutual coupling occurs only where the distance between drivers is within about 1/4 wavelength. In other words, you get more lows.

10. ### bassdude123

Aug 2, 2021
Okay i see, unlike most other amps, this has the same wattage @4Ohm and @8Ohm.

Another question:
As i dont want to buy all four cabs at once, more likely start off with just one of the 110s.... is there anything to keep in mind? (Cab has 300W, Amp has 1000Wpeak)

11. ### Wasnex

Dec 25, 2011

I suggest you try the cabs you are considering, choose the one you like best and plan to buy that cab only.

The idea is identical cabs will work with each other, because each cab has the exact some tuning. If you go with dissimilar cabs, the tuning may be different enough that they fight with each other rather than playing well together, and it does not matter whether you are mixing 15s, 12s, and 10s, or dissimilar 10s. The incompatibility relates to group delay and phase variances that occur around the port tuning frequency.

From what I have read, the group delay variances have more of an impact than phase variances. A good engineer can design 10s, 12s, and 15's that will all work well together, but just because two cabs are in the same product line does not guarantee that the engineering has been done.

Of course if if you can try both types of cabs together, then you can determine their compatibility before you buy.

As far as what to look for: The sensitivity ratings should be as close as possible. Higher sensitivity ratings are better, as you can make more volume with less power.

Keep in mind that if you use only two cabs, then each cab will see up to 500W. If you use one cab, 1000W will be available to it . Not a lot of 112 or 110 cabs can handle even 500W. So you probably want the highest power handling you can get if you plan to push the amp hard. Honestly, unless their is a specific need for really small cabs, the smallest I would go is 210s or 212s. I think it would be too easy to blow a 110 or 112 with this amp.

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12. ### bassdude123

Aug 2, 2021
I would use two exact same 110s.
Do you also see the potential of any tuning problems with the exact same model?

13. ### JeezyMcNugglesSupporting Member

Feb 23, 2018
Santa Maria, CA
I suck, but nobody really notices
The amp is 4 ohm minimum. You can run it at anything higher.

The downside is 2/3 power each time you double the impedance. The plus side is, that really doesn't mean anything volume wise.

14. ### bassdude123

Aug 2, 2021
It is rated 1000W peak @8ohm
So probably even more @4ohm

Less power means less air moving?

15. ### JeezyMcNugglesSupporting Member

Feb 23, 2018
Santa Maria, CA
I suck, but nobody really notices
Yes, because power cords move air when you plug them in.

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16. ### JeezyMcNugglesSupporting Member

Feb 23, 2018
Santa Maria, CA
I suck, but nobody really notices
So, it runs at 500 - 250w @ 8ohm

Depending on whether they state their "program" power as "peak" or not. Some double rms as "program", Peavey. Some double rms as "peak", ampeg. Others double program as peak, behringer.

If the peak is program, it's twice rms (which is its constant power rating). If the peak is peak, it's 4 times the rms (which is the constant power rating).

Last edited: Aug 2, 2021
17. ### bassdude123

Aug 2, 2021
But it is rated 1000 peak @8ohm

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18. ### JeezyMcNugglesSupporting Member

Feb 23, 2018
Santa Maria, CA
I suck, but nobody really notices
You're right. I can't argue with black and white printed truth.

19. ### JeezyMcNugglesSupporting Member

Feb 23, 2018
Santa Maria, CA
I suck, but nobody really notices
Although, what most people don't realize, is that's actually really loud. Like, it's really more than you need.

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20. ### bassdude123

Aug 2, 2021
I see, thats crazyy

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