randomsuper

basically i have a pair of 10' eclipse subs (8 ohm) that handle 200 watts rms per sub. if i hook them up to an amp that gives out 200 rms at 4 ohms per channel, is that what the subs are actually receiving?

burstaneurysm

100W RMS

randomsuper

500 rms at 2 ohm would equal what then? and could you give me the formula to how you figure this out? thanks.

IH8ONYU

500rms @ 2 ohm would be 250watts each. google "ohm's law" and you'll get all the info you need on how to calculate resistance.

tCizzler

Well thats partly incorrect. He said his amp is 4 ohms and the speaker is 8 ohms. Unless the speaker is 4 ohm stable ALSO, it will blow out the speaker because the amp is sending a bigger load than the speaker can handle. It might not blow immediately, but without a doubt, it will blow eventually.

Unless of course you hook the speakers up in parallel, that would make the load 4 ohms and would match the output of the amp. If you did that, you would only be able to use one channel (or bridge it if possible). And in that case you would get 100W rms as burstaneurysm stated.(not bridged) And 200W rms (bridged)

To help more, we need more info, how many channels(assuming 2)... model number....bridgeable....???
And like IH8ONYU said, you should google ohm's law and get familiar with it before meesing with a system. They are easy to blow up if wired incorrectly, and expensive to replace.

trdsparks

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tCizzler

No, that is how it works! Amps don't let you choose how much resistance you "want" to attach, they require a specific impedance. My amp doesn't work with 8 ohm speakers, it only has 4 (bridgeable)and 2 ohm (non-bridgeable) outputs.

It is not because "4 Ohms is the most common". It is because 4 ohms is a good efficiency. And that just so happens to make it the most common.

And also i bolded the part where you contradicted yourself. 8 ohms is more than 4 ohms, right? = more resistance (common sense) but at 8 ohms it puts out less power (50W compared to 100W) So no, thats not "just how it works" as you said and as i also bolded

trdsparks

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J1slim

with out starting a fight....two 8ohm subs wired in paralell will give you a 4ohm load on the amp. QUESTION...is the amp a 2 or 4 channel???
most amps will be able to handle a 4ohm load when bridged(mono)

some people need to take a breath....the ohm load from the speakers determins what the amp will put out.....ohms are like fractions, the smaller the number the bigger the load will be.

http://rockfordfosgate.com/rftech/wo...2&woofer_imp=2

trdsparks

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J1slim

you are very welcome....!!!!!!!!!!!!!!!!!!

randomsuper

the amp is an ma audio m700xe. specs below.

2-Channel Amplifier
250 watts RMS x 2 chan. @ 4-Ohm Stereo
500 watts RMS x 2 chan. @ 2-Ohm Stereo
1000 watts MAX x 1 chan. @ 4-Ohm Bridged
Variable High/Low Pass Crossover 50-250Hz
Variable Bass Boost 0-18db @ 45hz
3-Way Protection Circuitry
Full MOSFET circuitry
2-Ohm stereo stable
High/Low level inputs
Low level outputs


Amplifier Specifications:

Number of Channels 2
RMS Power (4 ohms) 250 watts x 2 chan.
RMS Power (2 ohms) 500 watts x 2 chan.
RMS Power (1 ohm) Not Stable
Bridged RMS Power 1000 watts x 1 chan. @ 4 ohms
Peak Power Output 1000 watts
Min. Impedance Unbridged 2 ohms
Min. Impedance Bridged 4 ohms
THD @ Rated RMS Power 0.05%
Channel Separation Yes

so will this amp work or not?

J1slim

you should have no problem running those subs bridged at 4ohms.....just dont turn it up all the way

UV7

Yes, but it will only be giving each woofer 125 watts RMS with each woofer on its own channel. If you were to wire the woofers parallel and bridge the amp, kiss the woofers goodbye! Wiring them series on the bridged amp would yield approximately the same wattage as stereo.

randomsuper

i guess i gotta get some new subs then. it's a shame because those eclipse's sounded really nice. oh well. thanks for the help guys. now i gotta figure out how to put 8' subs in a box already cut for 10 since i know exactly what subs will work with this amp with the air space i have. one problem after another.

UV7

There is nothing wrong with giving those woofers 125 watts of stereo bass. Why replace them? They should sound very good, clean, and will perform well. They may not be super loud, but at 200 RMS, the woofers are probably designed to optimize efficiency rather than be an SPL woofer designed specifically for tons of wattage.
I say hook 'em up. I think you'll be surprised. If they still aren't enough for you, then consider replacing them.

tCizzler

This is like talking to a wall that talks back And i'm really not trying to start a fight either, honestly i'm not. I just don't want randomsuper to damage any of his expensive equipment!

Thanks for the info randomsuper, its funny how it says 2 and 4 ohm but not 8 ohm..
And to j1slim... You said exactly what i said but in different words and now Josh is agreeing with you??? Except when you said the speaker will decide what the amp puts out. That is exactly true the way it is worded. But, not if the sub is not in the same impedance range as the amp. That link you posted is great!!! it says what i'm trying to say.
http://rockfordfosgate.com/rftech/wo...2&woofer_imp=2

Go there and select " Search by amp impedance"!!!!! It lists all the impedances of the amps. It doesn't say "just slap a sub on and this amp will magically adjust to ANY impedance you decide to throw at it".

And lastly for josh's quote "8 ohms is less not more in an audio system".
I'm not sure why you believe audio is different than everything else electronic, but it's not. 8 ohms is 8 ohms and 4 ohms is 4 ohms. Period
8 ohms is more resistive and less of a load = less power to sub
4 ohms is less resistive and more of a load = more power to sub

No matter what day of the week it is, that is how it goes

randomsuper

well, i appreciate the help everyone here has given me. i'm gonna hook them up and see how it sounds. if i don't like it, i'll just get some new subs better suited for the amp.

trdsparks

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tCizzler

Ok so which is it?? And thats when what you said became irrelevant to me!

And yes an 8 ohm sub will blow out (not blow up) with a 4 ohm amp powering it. Maybe not immediately if the volume and bass are turned down, but it will eventually, and who puts a system in their car and then turns it down.

The only exception is if the amp has "protection", which all NEW amps that i know of do have. Then the amp will shut down before anything blows due to the volume being turned too high and the subs can't handle the power being fed to them.