bridging 4 channel amp

[o2cavyss]

I don't know much yet and am trying to understand how some of this stuff works before investing in a system. I've heard some talk about running the front comps and a sub off a 4 channel amp, but in my research about bridging they always talk about going from a 4 channel to a 2 channel. Can you bridge only 2 channels to run to the sub and run the other 2 channels unbridged to the components?

[The Architect]

yes you can, Ive done it with my zx350.4, used the second set of channels bridged to power a CVT8 sub.

[r3b3l]

Im not certain but I think it changes the ohm-age(ie 2 ohm to 4 ohm or whatever) of the output signal as well as gives the output more power. You cannot bridge any two channels i dont think. The amp if it is bridgeable should indicate where the bridge can occur. (the inputs will be marked). On a four channel amp the front channel and rear channel will be bridged together to make one 2 channel amp. Meaning on the front channel you would use either the left or right positive along with either the left or right negative on the rear chanel. Its confusing i know and I could be giving you misinformation as i said its been many years since ive used a bridge. I would just buy two amps to be honest with you.

[o2cavyss]

I'm trying to keep this as small an install as possible and I want the amp under the passenger seat. Also, won't the additional amp cause more strain on the electrical system than the single 4 channel amp?

[The Architect]

your electrical will be just fine up to 1000rms AND you aren't an ass to it.

[talnlnky]

I'm trying to keep this as small an install as possible and I want the amp under the passenger seat. Also, won't the additional amp cause more strain on the electrical system than the single 4 channel amp?

yes... but like said, you should be fine.

when you bridge two channels together you will go from being 2ohm stable to 4ohm stable.... For example. Most 4 channel amps can do 4 channels @ 4 or 2 ohm, or 2 bridged channels at 4ohm.

the power breakdown would look like this

75x4 watt amp:

37.5x4 @ 8ohm
75x4 @ 4ohm
150x4 @ 2ohm
or
(bridged mode)
150x2 @ 8ohm
300x2 @ 4ohm

so, depending on the type of sub you have, bridging may be a good idea, a bad idea, or a moot point. most subs have either a single 4ohm coil, or dual 4ohm coils (DVC 4ohm).

A single 4ohm coil would be perfect, a DVC 4ohm would require you to run 1 channel to each coil @ 4 ohm (total of 150rms), or 8ohm bridged (150rms) or run the amp out of spec @ 2ohm bridged (theoretically that'd mean 600rms, but really it won't be anywhere close to that cause of heat issues... plus you're bound to fry your amp some day.... if not soon).

If you had DVC 2ohm coils you could run 4ohm brdiged, or 2ohm on 2 different channels.. .both options give you max power out of that amp, and are safe.

like I said before however, most subs are either SVC or DVC 4ohm... and most entry level subs are SVC.

[o2cavyss]

So, just to clarify, the amp I was looking at looked like this (RMS)

4 ohms, 80 watts X 4 channels
2 ohms, 95 watts X 4 channels
bridged @ 4 ohms, 190 watts x 2 channels

So you're saying I would NOT be able to have 2 channels at 80 watts and 1 channel at 190 watts, right?

Originally my thought was to do that and run the bridged channel to a 10" single voice coil sub i had my eye on with 150 watts RMS. But if you're telling me I can't do that, could I still do the same set up unbridged and run the 2 rear channels to a 2 ohm dvc?

[The Architect]

show us the amp, i did to my 4 channel amp what you are looking to do.

[o2cavyss]

show us the amp, i did to my 4 channel amp what you are looking to do.

amp
http://www.sonicelectronix.com/item_9172_SPL+FX4-840.html

sub
http://www.sonicelectronix.com/item_8456_Kicker+C104+-07C104-.html

[The Architect]

well besides the fact that those numbers are likely to be a little inflated you can do what you want with that amp it appears.

When you bridge two of the 4 channels it'll do "190W" at 4 ohms while keeping the other 2 channels for speakers.

It's a good match for that sub though, I'd say go for it, not bad for a super budget system, you should be happy.

[o2cavyss]

the possibility of an inflated 190W at 4 ohms should not be a problem with a sub thats only at 150W at 4 ohms, right?

[The Architect]

yea and after very minor impedance rise it should level out to a safe area, you dont need to worry at all.

[o2cavyss]

Awesome, thanks for answering the rapid-fire questions. As I said, I'm new to this stuff and want to get it right. Don't have a big budget and don't need a super loud system. Right now, i've got the amp, amp kit, RE-Q, sub, box, components, and sound deadening for the doors priced at about $400 and I think thats all I'll need for now.

[The Architect]

sounds about right, not a bad price for a full system thatll make you happy.

[talnlnky]

as Arch said... will work fine... should do the 3 channel mode no problem.

since that amp has 40amps worth in fuses, and is most likely a class A/B amplifier... it'll be around 50% efficient... therefore do the math equation (efficiency * fuses* voltage = realistic rms value).

you get 50*40*14= 280rms TOTAL. so, a bridged channel on that amp will prolly do 140rms @ 4ohm. looks to be a good match to the sub.

thats a little rare for an A/B amp not to double power as you drop the ohm load by half... but that has to do with the power supply on the amp. It's not a bad thing, so don't worry, some amps are just designed that way.



Oh yeah... if you ever decide to make your own box (and want to go ported) pm me and i'll whip you up a ported box design really quick. You seem to be a doing a decent job and finding your self a very good "bang for the buck" setup.... which I have a lot of respect for.

[talnlnky]

dude.... was looking at that site.... the SPL amp for $89 and the Power Acoustic amp for $84 are virtually the same amp... the Heatsinks look similar, the fuses are the same rating (2x20 vs. 1x40)... and they have the same ratings...

I would be money they are 98% the same, and made in the same factory... not sure if $5 matters to you or not... I only have experience with one Power Acoustic amp. Was a buddies, his only complaint was that it had a turn-on thump... other than that he said it was reliable cheap power. Never worked with the SPL brand.

[o2cavyss]

there do seem to be some differences between those two amps

Maximum Input guage size
SPL-8
PA-4

Speaker Level Inputs
SPL-Yes
PA-No

Signal-to-Noise Ratio
SPL-98 db
PA-97 db

Fuse Rating
SPL-20A x 2
PA-40A x 1

Also, shipping on the SPL is free and the PA is about $16

The maximum guage input worries me now, I just ordered the Knu's Kolossus Fleks 4 Gauge 4 Channel Amplifier Installation Kit...does that mean I cant use the 4 guage wires with the SPL?

btw, its cool that you did that research. Much appreciated

[talnlnky]

there do seem to be some differences between those two amps

Maximum Input guage size
SPL-8
PA-4

Speaker Level Inputs
SPL-Yes
PA-No

Signal-to-Noise Ratio
SPL-98 db
PA-97 db

Fuse Rating
SPL-20A x 2
PA-40A x 1

Also, shipping on the SPL is free and the PA is about $16

The maximum guage input worries me now, I just ordered the Knu's Kolossus Fleks 4 Gauge 4 Channel Amplifier Installation Kit...does that mean I cant use the 4 guage wires with the SPL?

btw, its cool that you did that research. Much appreciated

I was talking more about internals of the amp... for example... in car terms... A dodge stealth was a rebadged mitsubishi (3000??).... same car... some very minor differences. Most audio products are build in one of a handful of different factories in the world.

The S/N is a stat that manufacturers can always tweak and 1dB is not a big difference at all
the fuse difference really isn't a difference at all. Both are 40amps. The speaker level input is really the only thing that sets them apart.

the 4awg vs 8awg input ehh... 4awg is nice... but not needed on an amp that size. Using ring/fork connectors (which you might have to trim with a drimmel or pair of snips) you can always fit bigger wire.

stinger and many other wire/connector companies will make either a 4awg Fork or 4awg Ring connector. Fork would probably be the easiest to work with.

http://www.grainger.com/Grainger/items/1A082

[o2cavyss]

Well, I have already ordered the amp kit, but not the amp yet. The Knu kit does include the ring and spade connectors. So, you think I could go ahead and use the SPL and just trim the connectors if need be, or would I be better off getting the Power Acoustic?

[o2cavyss]

actually, in looking at it more, the power and ground wires are 4 guage and the amp description matches that. The speaker wire that comes with the kit is 12 gauge...that's the wire they're talking about with the maximum input gauge size, right?

maybe i'm wrong...just trying to figure this all out

[The Architect]

the 12 gauge speaker wire is for the speaker inputs which is fine, the power and ground inputs are 4 gauge which is also fine.

the knu kits will have you covered 99% of the time for basic installs.

worst case youll have just to trim off some of either of the wire to make it fit but i think you'll be fine.