ohms and impedances and amps..

[NateS]

hey everyone,

through the magic of craigslist i landed myself a deal on an 8x10 that i couldn't pass up, so now i have...2 8x10s.

the only thing that i didn't do was think about power matching and impedances and all that good stuff (i don't even know if i'm spelling impedance right?)

so, my setup is:

behringer BX4500h 450 watt 1x4 ohm or 2x8 ohms
ampeg svt810 4 ohm mono 2x8 ohms stereo
crate bx-810e 8x10 8 ohm

the crate amp is my "new" one..

the behinger has 1 speakon out and 2 1/4" jacks, the ampeg has speakon and 1/4" galore, and the crate only has 2 1/4" jacks - so what i've tried is the running from the behringer to the ampeg with a speakon cable, and the behinger to the crate with the instrument jacks. it played, but i didn't really do it for more than a minute because i didn't want to mess it up accidently.

 

[Luke.Walton]

All of this information can be found in the Amp FAQs so don't be afraid to search

However,

Your Behringer has a minimum impedance of 4 ohms, and the combined impedance of both cabs is 2.67 ohms, so if you keep running both cabs together you will end up ruining your amp.

If you want to run two 810s with your current amp, you will need two 8 ohm cabinets.

 

[RickenBoogie]

+1 you cannot run both those cabs with that amp.

 

[NateS]

ok, well, that sucks, haha. i looked through the amp faq, but i wasn't sure about the numbers..
so basically because the ampeg has a 4 ohm impedance, it is trying to draw more power than the amp can put out?

is there any way to run these two cabinets together, with a different amp? i'm looking to get away from behringer anyway...

edit: could it work if i only use half of the ampeg? use one of the 2x8 ohm? then it'd be a 12x10 setup..

 

[knigel]

2 Ohm capable head, for example Carvin Peavey SWR.

 

[sleepytime]

Some heads run 2 ohms. Or use a stereo power amp.

 

[Luke.Walton]

Yeah, you could use half the ampeg, but then you would effectively be lugging around a box twice as big as you need.

Oh, and in that situation, each driver in the ampeg would be getting twice as much power as each driver in the Crate, which, as far as I know, isn't a good idea, but I'm not 100% sure on that

 

[NateS]

well, this setup would only be for at home right now, anyways, untill i get my next amp which will support 2 ohms and i can take them both to shows.

i'll just use one of them outside my house.

 

[Jim Carr]

Get a power amp that is 2 ohms capable on each channel. The effects send of the Behr can be your pre amp.

 

[jsbarber]

glockenklang makes an impedance doubling/halving transfomer which can be used to double the load that your amps sees, i.e. 5.34 ohms.

read this, for instance:
http://talkbass.com/forum/showpost.php?p=8693541&postcount=78

Since your amp produces 450 watts, it is within the limits of the transformer, which can handle up to 600 watts.

Jim

 

[IdealWay]

just curious, what type of music/venues do you play that you would need 2 8x10s??

 

[NateS]

just curious, what type of music/venues do you play that you would need 2 8x10s??

hehe, it isn't really necessary at all, really..for a long time i've planned in my head that i would have 2 8x10s one day, and it just happened alot quicker. my band is very very bass heavy, so it will be nice to spread the sound out more.

i'll look into that impedance doubler

 

[bikeplate]

HI

You need two 8x10's at your gig? WOW. My buddy plays for Bryan Adams and he only needs one.

You need another head or a stereo power amp to use both together

Rob

 

[Never_grew_up]

Or if you're handy with a soldering iron and making your own cables you could make a cable that let's you run the 2 halves of the Anpeg in series rather than parallel, then add the Crate in parallel. You'd end up with a total impedance of 5.33 ohms.

 

[ajota_di]

Sell the berringer and crate and buy yourself a nice svt and some headphones. Nobody, NOBODY needs two 810's.

 

[NateS]

so, the cable runs out of the amp, then splits in half and runs the 2 halves of the ampeg in series? how would i go about making the signal come out of one half of it and into the other half?

 

[NateS]

Sell the berringer and crate and buy yourself a nice svt and some headphones. Nobody, NOBODY needs two 810's.

well, that'd be no fun. i can't put the ampeg on one side of my body and the headphones on the other side and turn myself into jello, now can i?

 

[jsbarber]

You have a 450 watt amplifier, which is below the limit on either of your 810s. It's unlikely you'd generate any additional SPL with two cab's over what you'd achieve with the 4 ohm ampeg 8X10 alone, so why bother?

 

[NateS]

yes, see that it's totally pointless fun at this time, but that isn't going to make me sell or throw out one of them...

 

[TerrorRhythm]

just curious, what type of music/venues do you play that you would need 2 8x10s??

heh