3 x 8ohm cab with 4 ohm head?

Electricblue · #1 08-27-2011, 11:07 AM

Hey guys, I know that if I paralleled all these together, I would fry my amp.

Is there any way I can have a 410, 115, and 115 to the same amp? I was hoping to have the 410 getting half the power, and the 115's having a quarter of the power each.

I'm looking at some kind of impedance converted transformer thing. Am I right?

somegeezer · #2 08-27-2011, 11:10 AM

You can't convert an 8 ohm 115 to 16ohm, but you could change 4ohm 115s to 16ohm. I think you're best just using the 2 15s or a 15 and 410.
Your other option is going for a 2 ohm power amp. Or stereo 4ohm.

Electricblue · #3 08-27-2011, 11:15 AM

Quote:

Originally Posted by somegeezer

You can't convert an 8 ohm 115 to 16ohm, but you could change 4ohm 115s to 16ohm. I think you're best just using the 2 15s or a 15 and 410.
Your other option is going for a 2 ohm power amp. Or stereo 4ohm.

Yeah, my current setup is 4 ohm head, 8 ohm 410, and 8 ohm 115. I tried 2x115 today, and I loved it, so I'm probably going to get another matching 115. It's really cheap.

What about the two 115s in series, then the 410 in parallel with the 2x115 combination?

Warfender · #4 08-27-2011, 11:17 AM

That is 3.75 ohm and is below your amp rating. Wouldn't do it brother. Asking for it.

greenboy · #5 08-27-2011, 11:18 AM

the new math.

JimiLL · #6 08-27-2011, 11:19 AM

Absolutely not

Electricblue · #7 08-27-2011, 11:22 AM

Quote:

Originally Posted by Warfender

That is 3.75 ohm and is below your amp rating. Wouldn't do it brother. Asking for it.

Just wondering, how did you come up with that? 8 ohm + 16 ohm in parallel isn't below 4 ohms?

James Judson · #8 08-27-2011, 11:25 AM

Most musicians have very few technical knowledge. I would not take advice from this forum as you don't know who knows what they're talking about and who doesn't.

I reccomend you go to an engineering school and if that is out of the question find someone that has.

Best bet.....................owners manual.

Bufalo · #9 08-27-2011, 11:26 AM

Series-wiring the two 15 cabs would create a 16ohm load, which you could then run in parallel to the 8ohm 410 creating a 5.3 Ohm total load. Remember the math for two parallel wired loads is "product over sum" so product (8 x 16 = 128) divided by sum (8 + 16 = 24) is 5.3333333333333333333333333...

BassmanPaul · #10 08-27-2011, 12:03 PM

3 8Ω loads in parallel works out at 2.67Ω. This would be fine for a 2Ω capable amplifier. BUT remember we discussed the 4x10 + 1x15 pairing as being poor? This version of a connection scheme will put both of the 1x15s in jeopardy. Had the 15s both been 16Ω the system would work fine. To keep up to a 4x10, the 2x15 has to total the same impedance.

charlie monroe · #11 08-27-2011, 12:16 PM

Quote:

Originally Posted by James Judson

I would not take advice from this forum

BassmanPaul · #12 08-27-2011, 12:22 PM

Quote:

Originally Posted by James Judson

Most musicians have very few technical knowledge. I would not take advice from this forum as you don't know who knows what they're talking about and who doesn't.

I reccomend you go to an engineering school and if that is out of the question find someone that has.

Best bet.....................owners manual.

James, you have been a member here for long enough to know the credentials of some of the folk who post here. At least you should!!!

Electricblue · #13 08-27-2011, 12:26 PM

Quote:

Originally Posted by James Judson

Most musicians have very few technical knowledge. I would not take advice from this forum as you don't know who knows what they're talking about and who doesn't.

I reccomend you go to an engineering school and if that is out of the question find someone that has.

Best bet.....................owners manual.

That's an ignorant statement. My knowledge isn't the best, but I come here mostly to learn, and help people with the stuff I definitely do know. I try not to mis-inform with information that I don't know.

Have you ever encountered Bill Fitzmaurice, Line6man, Greenboy or SDG Lutherie? These guys know what they are on about, I've read up on the stuff they told me, it's solid info.

If this site is useless to you, feel free to logout permanently.

walterw · #14 08-27-2011, 01:47 PM

Quote:

Originally Posted by Electricblue

Yeah, my current setup is 4 ohm head, 8 ohm 410, and 8 ohm 115. I tried 2x115 today, and I loved it, so I'm probably going to get another matching 115. It's really cheap.

What about the two 115s in series, then the 410 in parallel with the 2x115 combination?

that would work (giving you a 5-something Ω load) but would be pointless.

the entire 2x15 stack would be sitting there getting only half as much power as the 4x10 was getting, so you wouldn't really even hear it over the 4x10.

besides, all diligent TB readers should know by now that mixing cab types is not that great an idea anyway.

if you liked the 2x15 sound (i sure do) just put the 4x10 in your practice place and use two 15s at gigs. if at all possible, get two of the exact same cab for best low-end efficiency.

keyboardguy · #15 08-27-2011, 11:04 PM

For future reference (From Carvin)

SPEAKER COMBINATIONS and OHMS ( Ω ):

Four x 8Ω cabinets = 2Ω
Three x 8Ω = 2.66Ω
Two x 8Ω = 4Ω
Two x 4Ω = 2Ω
One 8Ω and One 4Ω cabinet = 2.66Ω
Two 8Ω and One 4Ω = 2Ω
One 2.66Ω and One 8Ω = 2Ω
Two x 2Ω = 1Ω
Three x 4Ω = 1.33Ω
Two x 4Ω and One 8Ω = 1.6Ω
One 2.66Ω and One 4Ω = 1.6Ω

Regards,
Mike

**IvanMike** · #16 08-28-2011, 03:00 AM

there is the OHMS FAQ.....

FWIW, it's not worth building a series cable to be able to use all these cabs together. The advantage you gain by using all the cabs will be negated by the reduced wattage they get, not to mention some probably terrible phase response issues.

Wanting something to be so doesn't make it so.

and double FWIW, there are a ton of us on here who know our stuff.... I'd trust TB over advice from the FLMS any day of the week.

RickenBoogie · #17 08-28-2011, 08:05 AM

+1 I've received better advice here than ANY music shop I've EVER been in.

JTE · #18 08-28-2011, 12:51 PM

Quote:

Originally Posted by James Judson

Most musicians have very few technical knowledge. I would not take advice from this forum as you don't know who knows what they're talking about and who doesn't.

I reccomend you go to an engineering school and if that is out of the question find someone that has.

Best bet.....................owners manual.

I wouldn't take advice from someone who can't put together a coherent sentence. "... very few technical knowledge ..."

Nor would I take advice from someone with such poor knowledge of the expertise of of forum members (many of whom HAVE gone to engineering school) as to dismiss them all in one fell swoop.
John

Aussie Player · #19 08-28-2011, 01:02 PM

I like running 2 heads. Also acts as a safeguard if there is an issue with one.
My basic rig is a 500W head into an 8x10 box and a second 350W head into a 2x15 cab.

Balances nicely with separate volume controls and eliminates any issues. An extra head is not much more to carry.

gjbassist · #20 08-28-2011, 01:04 PM

Quote:

Originally Posted by JTE

I wouldn't take advice from someone who can't put together a coherent sentence. "... very few technical knowledge ..."

Nor would I take advice from someone with such poor knowledge of the expertise of of forum members (many of whom HAVE gone to engineering school) Hasbro dismiss them all in one fell swoop.
John

Yeah, I caught that too! My thoughts exactly!