4 ohm vs 2 ohm
 

So I replaced the stock alpine speakers in my sound bar last night with the Polk db651s's that a lot of guys seem to be using. They are 4 ohm, whereas I've seen the stock alpine amp is 2 ohm. The biggest thing I noticed is that the stock subwoofer is much less noticeable than it was when i had the stock speakers in the sound bar. Is there any way they could be drawing power away from the sub? I don't see how this install could have made the sub almost non-existent, which it seems to be now. Does a 4 ohm speaker draw more power or something?
BTW, for those of you who are just planning to upgrade the speakers, I'd go with something with a little more magnet. It'll fit. To my ear, the Polk isn't a big difference from what it was. I know it needs some time to break in a little, but aside from the addition of the tweeter, being a coaxial, I really can't tell the difference yet.

In a way, Yes. As you have found out, it takes more power to drive 4 Ohm speakers than it does 2 Ohm speakers. You only have ! amp that powers ALL your speakers. Power has to come from somewhere.

Most people who do only a speaker swap ( 2 Ohm for 4 Ohm ) actually think the sound is a little worse. Thats because they have to turn the volume up more to get the same sound. By the way, the sound will not change when they "brake in". Your only fix is to boost the power.

PS: I have the db651's and the db6501's. And they are very good sounding speakers when used with a good amp.

Right, but you probably have an aftermarket HU too, huh? I want to keep the stock HU. So should I stick with 2 ohm speakers for now? I will probably add something like the JBL MS-8 or JL Cleansweep at some point, so that I can add an aftermarket amp inline with the stock alpine amp, but it won't be for quite a while.

I think the speakers are out of phase. If you wired one or even both speakers "backwards" or electrically out of phase they will cause a HUGE reduction in bass. Try reversing the positive and negative on each new speaker, one at at time and see if the bass response improves.

The short answer is no, changing full range speakers will not "take power away" from the sub section of the amp. If anything, the sub should seem louder since the 4 ohm speakers you installed are causing about a 50% reduction in power supplied to them from the amp. Again, not 50% less to the sub, that part remained the same. I think you are having a phase cancellation of bass due to the sub being "in phase" and the new speakers, one or both, are "out of phase".

With regards to above statements... Sometimes the new 4 ohm speakers are actually louder than the less restrictive 2 ohm coils on the factory since the new speakers are more efficient.

Sent from the fast lane while driving one handed.

A quick test. Turn the fader all the way to the front. Then check left right balance and the effect on the bass. Then fade all the way to the rear speakers and check balance again. If the rears have "less bass" then they are both wired out of phase to the fronts and sub. If the bass is better from left or from right only but not when the balance is set to the middle (still faded all tithe rear, the sub is non fading) then the "better sounding" speaker is in phase and the no bass having side is out.

Try it.

Sent from the fast lane while driving one handed.

Oh. And for the record.


Left rear speaker + is grey/light green and - is grey/ dark green
Right rear speaker + is dark green/light green and - is dark green/ grey

This is confusing to most. But trust me. This is correct.

Sent from the fast lane while driving one handed.

I don't think they are wired backwards. I can definitely hear the tweeter behind my head now. I will try the test after work, though.

BTW, I saw that +/- wire color before, but mine weren't those colors. The driver side was green w/ a white stripe, and black with a white stripe. The passenger side was something like green w/ a white stripe and light blue or gray with a white stripe. What I did was look at how the clip was connected to the stock speaker. I assumed right-side wire going into the clip was positive, as the right side post on the Polk speaker is the positive side. So I reattached the left speaker wire to the negative side on the polk, and the right speaker wire to the positive side for the Polk.

I haven't seen a multi channel amp that doesn't reduce output to ALL speakers with each increase in speaker resistance. But I haven't seen them all. :dontknow2:

In doing this, you mean if the subwoofer clearly loses bass when fading from front to back and/or left to right balance in the rear? Or were you referring to the speakers themselves losing bass?

The 4 ohm speakers provide more resistance than the 2 ohm speakers. Since that amp provides it maximum power at 2 ohms, you will need to get 2 ohm speakers, or you will have to deal with a noticeable output loss do to not enough power to efficiently push them.