# Hypothetical 3 cab rig

Discussion in 'Amps and Cabs [BG]' started by tgriley62, Apr 9, 2012.

1. ### tgriley62

Jan 25, 2011
S.E. Mo
I have been trying to figure out how to set up a 3 cab rig based on 15" drivers, with all the drivers getting the same amount of watts & the only thing I can think of is this setup. If you were to daisy chain two 8 ohm 115's and then use one 4 ohm 215 cab each driver would get the same amount of watts. Also I know you would need a 2ohm stable head for this to work. Is this correct?

2. ### Dave WSupporting Member

Mar 1, 2007
Westchester, NY
Yes, but why?

3. ### Mystic MichaelHip No Ties

Apr 1, 2004
New York, NY
That is correct. But it's not the only such cab configuration that is possible. There is, for example, the possibility of running three (3) 1x15 cabs, each at 8 ohms, into a 2-ohm stable head.

In that scenario, each cab operates nominally at 2.67 ohms. Not a bad rig - at least in theory...

MM

4. ### tgriley62

Jan 25, 2011
S.E. Mo
Just always wanted to know how to set up an odd # of drivers without one cab getting more power than the others. I know even if you use the same size drivers but in two different cabs you will not be getting the most out of one. Example if you use a 4x10 with a 2x10 the 2x10 will be getting more power than the 4x10. Plus I just happen to like 15" drivers & think 3 would be killer

5. ### Mystic MichaelHip No Ties

Apr 1, 2004
New York, NY
It isn't a matter of the size of the drivers. It's a matter of relative impedances...

Strictly speaking, the 2x10 and the 4x10 would each be receiving the same amount of power - but each individual driver within the 2x10 would receive twice as much power as each individual driver within the 4x10. This all assumes, of course, that each cab has the same impedance rating. The way to get around that, of course, is to compensate with cab impedances, by using an 8-ohm 2x10 with a 4-ohm 4x10, for example. Or an 8-ohm 1x15 with a 4-ohm 2x15...

MM

6. ### tgriley62

Jan 25, 2011
S.E. Mo
Thanks. Would each cab get the same amount of power though?

Jan 7, 2008
YTZ
Yes

8. ### Mystic MichaelHip No Ties

Apr 1, 2004
New York, NY
Yes. Since each cab is rated at the same impedance level - 8 ohms - and each is running simultaneously from the same 2-ohm stable head, each cab will receive the same amount of wattage.

Note: This scenario presupposes your use of a mono-block (i.e. single amp) head. If using a stereo (i.e. dual-amp) head, things would become a bit more complex. You would have some some output-balancing to do...

MM

9. ### Jim CarrDr. Jim

Jan 21, 2006
Denton, TX or Kailua, HI
fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
Yes, they all get the same power.

I use a 4 ohm Epifani UL1 410 with an 8 ohm Epifani UL1 210. The drivers not only all get equal power, they are identical drivers in cabinets designed and built by the same company. Works fine as a 610. I do have a couple 2 ohm capable heads.

10. ### tgriley62

Jan 25, 2011
S.E. Mo
Thanks for the help. I know used 1x15's are not bad price wise for a first time budget rig

11. ### Jim CarrDr. Jim

Jan 21, 2006
Denton, TX or Kailua, HI
fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
12. ### BogeyBassInactive

Sep 14, 2010
Yes you would need a 2 ohm stable amp.

a 8ohm driver and 4ohm driver are still going to behave slightly different. Finding a single 4ohm 15 cabinet will be harder to find.
the sensitivity of 4ohm 15's is usually lower. At least among the common ones made by Eminence.

it would be easier to just run 3 matching 8ohm ohm drivers in Parallel. 3x8ohm parallel would be 2.6ohms.

13. ### tgriley62

Jan 25, 2011
S.E. Mo
Thanks. I actualy have that 2ohm head chart printed out. But I do have one other question concerning budget rigs. I may have the chance to join a group with 2 guitarist and drummer, playing classic rock i.e. REO, Doobie brothers type music and was wondering how 3 115's with a 300w head would do

14. ### 3rdcurveSupporting Member

Dec 26, 2008
Sullivan, MO
With 3 sensitive 15 inch drivers you wouldnt need much power at all. 3 Kappalite 3015s would have a sensitivity close to that of 2 ampeg 810s. I would think a mesa walkabout would be a great fit.

15. ### landau roofReupholstered User

Jul 29, 2010
Downstate CA
How about a Fender 400PS fully loaded with the three 18" folded horn cabs?

16. ### babebambi

Jan 7, 2008
YTZ
what kinda calculation gives you that conclusion?

17. ### Mystic MichaelHip No Ties

Apr 1, 2004
New York, NY
It's current as of three months ago - at least according to the information in the header. But there are some significant inaccuracies and omissions...

For example:

Missing is any mention of the Carvin B2000 - arguably the 800-pound gorilla of all 2-ohm stable bass heads currently in production.

Also missing is any mention of the Eden Nemesis RS700 & EN700, each rated at 700 watts @ 2 ohms, although both are now also out of production. Their predecessor - the Nemesis NA650 (also out of production) - is also 2-ohm stable (@650 watts)...but unfortunately shows up on the chart as the "RA700" - a model number that never existed in the Nemesis catalogue...

MM

18. ### tgriley62

Jan 25, 2011
S.E. Mo
So if I did run three 8 ohm 115's would all three cabs be dasiy chained to each other (A) or would two be connected with the third cab using the other output on the head (B)

\----cab

19. ### Jim CarrDr. Jim

Jan 21, 2006
Denton, TX or Kailua, HI
fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
Assuming the two outputs on the head are NOT separate channels, schemes A and B are actually the same.

20. ### Jim CarrDr. Jim

Jan 21, 2006
Denton, TX or Kailua, HI
fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
It is pretty likely you will have way more than you need in terms of speakers. Why do you want 3 15s? Not all speakers are created equally.

There are single 15 inch drivers that can out perform a dozen 15s. It all depends on the type of driver, cabinet design/execution, and fit to the application.

What type of cabs and amp are you contemplating?