Bridging an amp vs ohms...?

mbdyer12

Sorry about this, I searched through this forum and throughout the web but couldn't find a direct answer to my question... When wiring (2) 4 Ohm subs together to get it down to 2 Ohms, do you connect the wire on the + of one channel and the - of the other, aka bridging or to just one channel? ex:

L+ L- R+ R-
x x

(or)

L+ L- R+ R-
x x

In other words, I understand how to wire the subs themselves, just not how to attach them to the amp (in which connectors)

I could just be missing the concept all together, please help.. Amp is a small/no-name amp, Koiiler (I think). It's 2-ohm stable and is 300x2 Max Output (I'm assuming at 2 ohms?) How can I wire to GXR-12 subwoofers (365 watts max, 165 RMS) to take advantage of full output?

Thanks in advanced:

PoweredByDodge

well dude most amps are 2 ohm stable in STEREO and 4 ohm stable in bridged mode.

so i dunno.

but lets say your amp is 2 ohm stable in stereo (cuz i guess thats the assumption your working on).

wiring the speakers --- both positive terminals are wired together... both negative terminals wired together... so that now u have one pos going to the pos on both subs... and one neg going to the neg on both subs.

then.... wire that negative to your bridged negative terminal -- usually amp';s Right negative.

wire the positive to your amp's positive bridged terminal (usually the amp's Left positive)

leave the left negative on the amp and hte right positive on the amp UNHOOKED.

now.. this is normally how u do it... but some amps may be the other way... like left negative / right positive -- instead of left positive /right negative -=-- also your amp may have a button that must be pressed in order to make it properly operate in bridged mode.

mbdyer12

Thank you for the info, it seems to be working just fine...

I'm just curious but what is the difference between wiring 2 ohm stable in stereo and 4 ohms briged? It seems to be the same wiring config...

Thanks again,
Mike

PoweredByDodge

Originally posted by mbdyer12

I'm just curious but what is the difference between wiring 2 ohm stable in stereo and 4 ohms briged? It seems to be the same wiring config...

Its absolutely different.

your amp has two output channels ... a set of + and - for each left and right.

when you bridge it to a 4 ohm load, you, in effect, get three to four times the power into 4 ohms that you would have gotten into each 4 ohm channel in stereo mode. in effect, you run the channels at "2 ohms" each (for the sake of easy explaination).

to specifically answer your question on what teh difference is...

if you had 2 ohm subwoofers (dual 4 ohm coil or whatever) and u ran each one on one channel of your amp, you would get the same power that way as if you then seriesed those to subs and ran them off the bridge.

so in that case there would be "no difference" in power, even though the wiring would be obviously different.

if you wired two 4 ohm subs in stereo, and then parallelled them down to 2 ohms and bridged htem, you'd see that you got 3 - 4 times the power to EACH sub in bridged mode as you would in stereo... but this assumes you have an amp that is 2 ohm stable bridged. if not... you will not get this amount of power, and you may damage the amplifier. and obviously, as stated above, the wiring would be difft.

mbdyer12

Ohh wow, got it... Thanks buddy..


All the info I could find on my amp (because it was a hand-me-down and a no name along with that) was this :

Maximum power output@2omega 300Wx2=600W

Total channel output power: 130Wx2CH@2omega(260W) less then 0.5%THD

80Wx2CH@4omega(160W) less then 0.3%THD

bridged 260Wx1CH@4omega

...

Thats all the information it gives besides HP/LP filters, bass boost, remote on, etc... Would you say this was 2 ohm stable bridged in stereo? Would there be a way to tell if it was just by wiring it up and playing music?

automaticman

the problem is that amp really isn't desgned to run two 4 ohm subs. You have a couple different ways to hook it up. The only real way to wire them without exceeding the amps limitations is 4 ohm stereo - that is, one channel + and - to one sub + and -. If you wire the subs in parallel to get two ohms, adn then bridge that, the amp will be seeing the equivilent of a 1 ohm load. you can wire the subs in series to get 8 ohms and then bridge that, but that will drastically reduce the output of the amp. The amp would run one sub really well if you bridged it, or two 8 ohm subs wired in parellel and bridged

PoweredByDodge

ya dude... if its only 2 ohm stable stereo, it'll be 4 ohm stable bridged... 1 ohm stable stereo would imply 2 ohm stable bridged.

you shouldn't try to run it 2 ohm bridged.

use the amp for highs or sell or if u can and try to find a cheap mono 300 watt + amp.

mbdyer12

hmm ok those things are impossible to sell for anything really, oh well... thanks for all the help.

mbdyer12

I took your advice for buying a mono subwoofer amp and bought a Profile amp....

http://www.crutchfield.com/S-6ooAucRTsZG/cgi-bin/ProdView.asp?i=489CA400M I didn't buy from Crutchfield (found it somewhere else for a decent amount less)

Its 320 watts RMS x 1 at 2 ohms.. I hope its a decent one because the price was right.

For 165rms x 2 GXR-12 subs, 320watts rms at 2 ohms should be great right?

PoweredByDodge

320 @ 2 ohms is fine... i dont think u'e gonna find any profile fans in this forum, but hey... an amp is an amp, and for 100 bucks u can't go wrong. i think the profile will be a LOT better than your previous amp.

happy bassing.