Kicker amp vs speaker power question

[Zxurian 10+ year member]

I'm putting a new system together, comprised of Kicker parts. I'm not exactly new, but I'm a little confused about power requirements and I'm hoping you guys can help out.

Now as far as I've been taught, you should match the RMS output of the AMP, to the RMS rating of the speakers.

I'm planning on getting a Kicker sx700.4 to drive my speakers, which has the following spec's

RMS Power @ 14.4 Volts4Ω Stereo, 1% THD - 85w x 4

2Ω Stereo, 1% THD - 175w x 4

4Ω Stereo, 1% THD - 350w x 2

Now I'm planning to run four separate speakers off of this amp. My question is, how do I know if I'm running at 4Ω's, or 2Ω's, so I know which speakers to get? Is that dependant on the speakers, or is it a switch on the amplifier itself?

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[lil azn 06 10+ year member]

it is dependent on the speakers. If the speakers are 4 ohms then the amp runs on 4 ohms.

 

[Zxurian 10+ year member]

okay, so depending on whether the speakers are 4Ω's, or 2Ω's, that's what power raiting I should use.

Thank you for the information, lil azn 06.

Based on that, I was looking at a set of Kicker SS56.2 speakers to match with it, and they have a listed Peak/RMS raiting of 180/90, except that it lists a "System Impedance" of 3Ω's.

What would the impact be of using those speakers? with 1Ω difference?

 

[DejaWiz 5,000+ posts]

Depending on what the birthsheet says, expect roughly around 100-120wrms per channel at 3 Ohms.

 

[Zxurian 10+ year member]

so I should actually get the SS65.2, which have a Peak / RMS raiting of 200w / 100w, becuase those will better match the power handling, correct?

Thank you for all the help by the way, you guys are awesome.

 

[fwb_1234 10+ year member]

Sorry to thread jack, but what exactly is a birthsheet?

Is that some slip of paper, shipped with each amp, that lists that PARTICULAR amp's power specs?

 

[DejaWiz 5,000+ posts]

Sorry to thread jack, but what exactly is a birthsheet?
Is that some slip of paper, shipped with each amp, that lists that PARTICULAR amp's power specs?

Correct.

 

[Zxurian 10+ year member]

would it damage the amp / speakers if you were to hook them together with speakers rated at 3Ω's, and an amp that's set to output at either 2Ω's, or 4Ω's?

 

[fwb_1234 10+ year member]

No. In fact it doesn't output 2 ohms or 4 ohms even when connected to 2 or 4 ohm speakers, because speakers aren't actually 2.000 or 4.000 ohms. That ohms is approximate. The actual impedance of the speaker could vary from 1.5 - 2.5 and still be labeled as a 2 ohm speaker. If you hook up a 3ohm speaker, the possible power will be somewhere between that given for a 4ohm and 2ohm impedance.

Does that make sense?

Hope it helps.

Edit: Actually, the whole concept an amp "outputing" an ohm load is incorrect. The amp produces a stream of energized electrons. It is a low current (not that many electrons in the stream), high voltage (very energized electons) product. If you have taken high school physics, you should be able figure out what voltage your amp should "output" to produce the correct power. This math is the same math that is featured in the gain setting tutorial, located as a sticky in the amplifier section.

 

[Zxurian 10+ year member]

(thank you for your patience here for this)

so, the ohm raitings on speakers / amp's are actually approximations / ranges that they can handle, and the only way to get the actual ohm raiting is to hook them up and measure at that point, then you'd adjust the individual gain levels to get the right output and not over/under power your speakers....

Did that come out right?

 

[DejaWiz 5,000+ posts]

(thank you for your patience here for this)
so, the ohm raitings on speakers / amp's are actually approximations / ranges that they can handle, and the only way to get the actual ohm raiting is to hook them up and measure at that point, then you'd adjust the individual gain levels to get the right output and not over/under power your speakers....

Did that come out right?

All speakers are advertised with nominal impedance, hence they are listed as 8 ohm, 4 ohm, 2 ohm, so on and so forth.

An amplifier can not be "set" to a particular ohm load, as it is dictated by the speaker itself. To get 2 Ohm power from an amp, a 2 ohm speaker must be connected.

To get a deeper understanding of how a speaker's actual impedance can change during playback, check out these graphs of various nominal Ohm speakers:

ScanSpeak Revelator 4 Ohm

ScanSpeak Revelator 8 Ohm

ScanSpeak Revelator 16 Ohm

 

[Zxurian 10+ year member]

okay, thank you for the information, I think I've got it enough where I can match speakers to the amp I want now. I appreciate the informaiton.

One last question though....

if I get a 700x4 amp, do I have to have the 'same wattage rating on all four outputs, or can I have one pair rated at 3Ω, 100w, and another pair rated at 4Ω, 150w?

 

[DejaWiz 5,000+ posts]

okay, thank you for the information, I think I've got it enough where I can match speakers to the amp I want now. I appreciate the informaiton.
One last question though....

if I get a 700x4 amp, do I have to have the 'same wattage rating on all four outputs, or can I have one pair rated at 3Ω, 100w, and another pair rated at 4Ω, 150w?

Hope you meant 70x4 amp!

Yes, you can mix loads on an amp as you have described.

 

[Zxurian 10+ year member]

heh, now you've got me worried.

I meant 700x4, the stats for the amp are listed in my original post.

Is there something wrong with that or information that I got screwed up becuse of it?

 

[DejaWiz 5,000+ posts]

heh, now you've got me worried.
I meant 700x4, the stats for the amp are listed in my original post.

Is there something wrong with that or information that I got screwed up becuse of it?

Ooooooh, I see what you did there. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

SX700.4 = Kicker SX line, 700w max TOTAL, 4 channels.

Here's an example:

You have a set of 3 Ohm components and a 4 Ohm subwoofer. Using the SX700.4 to power everything, you hook it up like so...

Front Channels (1 and 2) are powering the 3 Ohm components in stereo, so they should be getting around 125w rms per channel.

Rear Channels (3 and 4) are bridged and powering the 4 Ohm subwoofer in mono, so it should be getting around 350w rms.

Cool?