What's up with my BRAND NEW speakers??

**tbird2340** · 10-19-2004, 11:30 PM

Me too.. At $250 (crutchfield price) for the 6X9's and $150 for the 5X7's (also crutchfield's price) I didn't think I would have any problems...

What about the included crossovers?

**tbird2340** · 10-20-2004, 11:23 PM

Ok.. Still planning on buying an amp but I'm still a little confused about the whole 2 ohm / 4 ohm.. I understand that if I get a 2 channel amp that is rated at say 50 W X 2 @ 4 ohms and I hook all four of my speakers up to this amp that it then changes the rating of the amp to 100 W X 2 @ 2ohms and it also makes the amp get a lot hotter. This is the conversation I had with a crutchfield rep about whether or not I should run them at 2ohm or 4ohm:

A Product Advisor will be with you in a moment. Please be sure to include their name as you checkout.
......
{Stephen} If you're driving full-range components or two-way or three-way speakers (anything but subwoofers), I don't recommend you work @2ohms. It's not as clean and you can hear the difference in regular speakers (you can't detect it with subwoofers because the frequency range is too low to hear the difference).
{Tom} So I should look for an amp that runs four channels at 4 ohms?
{Stephen} Yes, exactly. The Infinity Reference amplifier I gave you the link for is perfect.
{Tom} OK thanks for your time.
{Stephen} If your budget is too tight for that, don't go with a 2 channel amplifier, though.
{Stephen} On the low-end, I might suggest this Profile amplifier with 80 watts per channel --
Profile AP1040
80W x 4 car amplifier

http://www.crutchfield.com/cgi-bin/P...sp?i=489AP1040

So it sounds like he's saying that there is a big difference and that it may even be bad to do that?

**pimpJ** · 10-20-2004, 11:26 PM

that looks nice and a very reasonable price from crutchfield. I don't see any reason not too

**tbird2340** · 10-20-2004, 11:31 PM

Thanks for the reply but I'm not wanting to get that amp.. I'm wondering about the whole 2ohm / 4ohm deal...

**WhiteRabbit** · 10-21-2004, 12:03 AM

you dont choose to run an amplifier at 2 or four ohms. you merely hook up speakers to an amplifier, and the system runs.

all your kappas are four ohm speakers. thus, if you hook up just one per channel, it presents a 4 ohm load to the amplifier, and the amplifier responds to that load by producing, say 50 rms. this is the same 50 rms it would produce with a 4 ohm tweeter or 4 ohm subwoofer, doesnt make a difference, a load is a load.

now, if you were to hook up both front and rear speaker to the amplifier in parrallel, it presents a two ohm load to the amplifier. wiring in parrallel halves the resistance of two equal loads. thus, two 8 ohm loads become four, two two ohm loads become 1, two 400 ohm loads in parrallel become a single 200 ohm load. The amplifier now sees only 2 ohms worth of resistance (half the resistance to current flow) that it saw before, and responds by doubling the current (power) it lets through the speaker. in this case, 100 rms. each speaker gets 50 RMS, and you are back to where you started, on a per speaker basis.

you then lose your ability to fade form front to rear, if thats an important feature to you.

thus, in theory, you could wire all your speakers together in parrallel into a 1 ohm load, and double the power again from the amp, produce 200 watts from one channel, distributing it across all four speaker, each speaker recieves 50 watts again.

however, there are limits to current flow. the components can only handle so much current flow before heating up. at 1 ohm they would likely burn up. Thus, amplifiers have mimimum load limits. Usually for common amplifeirs this is 2 ohms stereo, 4 ohms mono.

if you chose to wire your speakers in series, you double the resistance. two 4 ohm loads become one 8 ohm load. per channel, the amp would see a single 8 ohm load, and respond by producing only say 25 RMS of power. distribute that among two speakers, each only gets 12.5 watts of power total!

so you see, the load an amplifier runs at is a function of how you wire the speakers together, rather than flipping switches on teh side of the amp or anything.

heres the quiz: lets say I have two 4 ohm subwoofers, and an amplifier that is at the most 4 ohm stable mono, a single channel amp, rated for 500 watts into its single channel at 4 ohms. how can I wire everything up, and how much power is each speaker getting? did I buy good equipment, or did I buy crappy equipment?

**tbird2340** · 10-21-2004, 08:11 AM

Answer to your quiz:

I would say you done screwed yourself... If you have two speakers to power and only a one channel amp that is only stable at 4 ohms you couldn't hook them up in parrallel because that would drop them amp down to 2 ohms (and wouldnt' be stable). But hmm.. Maybe you could wire them in series and make the speakers an 8 ohm load giving them 250 watts total or 125 watts each.

So.. Another example would be that if I used a 2 channel amp rated 100 X 2 @ 4 ohms and only hooked two speakers up to it my speakers would get 100 Watts a piece at 4 ohms. However, if I decided to run all four speakers off this 2 channel amp in parralel then it would change the rating to 200 x 2 @ 2 ohms which means all FOUR of the speakers would be getting 100 W's a piece but I guess it would drop them down to 2ohms? Which.. Why would that be bad?

**tbird2340** · 10-21-2004, 10:40 AM

Would this amp meet my needs?

http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWA:IT

**Snootch** · 10-21-2004, 12:01 PM

Originally Posted by tbird2340

So.. Another example would be that if I used a 2 channel amp rated 100 X 2 @ 4 ohms and only hooked two speakers up to it my speakers would get 100 Watts a piece at 4 ohms. However, if I decided to run all four speakers off this 2 channel amp in parralel then it would change the rating to 200 x 2 @ 2 ohms which means all FOUR of the speakers would be getting 100 W's a piece but I guess it would drop them down to 2ohms? Which.. Why would that be bad?

Yes, all four of the speakers would be "seeing" 100 watts a piece, but the only thing that is "dropping" is the resistance of the load on the amplifier, caused by the wiring of two speakers in paralell. The speakers are still four ohms each. In regard to the being "bad"part,I assume your talking about what the crutchfield rep said? The reason that he said that was because of a measurement of the performance of an amplifier called a "damping factor". The damping factor is the capability of an amplifier to control the cone of a speaker accurately. The more sloppy the output of an amp,the lower the damping factor. The cleaner an amp is, the higher the damping factor, the cleaner an amp is. The more stress you put on an amplifier, the lower the damping factor is going to be. So,when you run an amplifier at 2 ohms stereo, the damping factor is going to be lower than it is at 4 ohms stereo. HOWEVER, newer amplifiers are better that their older siblings, and the difference between 2 and 4 ohm stereo will be so small, it will be inaudible. Damping factor works the same way with low impedances on amps driving subwoofers, but the effects are inaudible due to the low frequency. Simply put, the guy was bringing damping factor up to try to wow you, and you would have so spend more $$ on a 4 channel amp. The only difference between using a 2 versus 4 channel amp will be the loss of your front/rear fader, less money spent, the amp runs a little warmer, and puts out more power per channel. Enough said.

**tbird2340** · 10-21-2004, 01:39 PM

Ok.. LOL.. One more question...

Say I got a 4 channel amp that was rated 50 W X 4 @ 4ohms and 100 W X 4 @ 2ohms. Which one would I want to run it at? 2 ohms so I could get 100 W per channel? How would this be done?

**Snootch** · 10-21-2004, 02:54 PM

Since your mid/high speakers are 4 ohms (as all car audio components are) you would be doing 50x4. That should be enough for your infinity mids/highs. Just because the amp will do 100 x 4 doesn't mean you gotta do it.

The only way you could run it at 100 x 4 @ 2 ohms, is to wire in another speaker in parallell at each existing speaker. There isn't any room for this, at not least in the stock door. I have a RF 800a4 amp running my mid/highs in my car. It will do 100 x 4 @ 4 ohms, or 200 x 4 @ 2 ohms. I run the front channels on a pair of tweeters, and the rear channels on a pair of 6-1/2"s. All the speakers are 4 ohm. The one amp I pointed out to you in the PM was a RF capable of 50 x 4 @ 4 ohm. The cool thing about the older RF amps, is that they "say" 50 x 4, but it's actually something like 65 x 4 @ 4 ohms.They were a little underrated. The reason I point people towards the used, old-school RF 4 channel amps, is because of this. also, if you so desired you could un-hook the rear speakers, put them in parallell with the fronts, so then you would get 100 x 2 @ 2 ohms on all four mids/highs. that frees up the other two channels, so you could bridge them, getting 200 x 1 @ 4 ohms for a subwoofer. This way you don't have to buy another amp,or any more wiring. This is great for a starter system on a budget. See how the 4 channel allows for flexibility?