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Matching Amps with Speakers RMS

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=38720
Printed Date: July 09, 2025 at 7:42 PM


Topic: Matching Amps with Speakers RMS

Posted By: hurtado_roberto
Subject: Matching Amps with Speakers RMS
Date Posted: September 07, 2004 at 2:29 AM

Why do amplifiers have different outputs at different ohm resistances?  Do you get better SQ at higher subwoofer resistance or are these two things irrelevant?

I have a RF P8002 amp with

200 W x 2 @ 4 Ohms RMS
400 W x 2 @ 2 Ohms RMS
800 W x 1 @ 4 Ohms Bridged RMS

I currently have 2 Sony Subs (XS-L121P5)

1200 watts peak, 350 watts RMS

I can not bridge them since my amp is not stable at 2 ohm bridged.  My amp is only outputting 400 watts then.

I was thinking that If I bought 2 more of these crappie subs and bridged them to 4ohm then I would still be giving 200 watts to each speaker.  What are the differences in performance?  My amp will be working harder and outputting more power right?

I'm going to upgrade my subs.  I was told that DVC subs do hit harder and I want to stay with RF and Best Buys warranty.  I looked at the P312D4 (1000 watts peak/ 500 watts RMS).  15" are mostly used for lower frequencies and require more space; Do you think these are not good for SQ?

Do you think my amp will suffice a pair of these subs?  It's better if I buy two so I can bridge them as bellow to a 4 ohm load right.

posted_image

If I want stereo sound do you think I can bridge them as bellow to each channel?  Will I still get the same power output from my amp?

posted_image

What set up will give me better SQ from your experiences?

No I realized that the set up I have right now with my Xploder's does not utilize the full power of my amp.  I think best buy needs better sales people.  Thanks for your time.



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Poly Dollies



Replies:

Posted By: /R7
Date Posted: September 07, 2004 at 8:12 AM
Why do amplifiers have different outputs at different ohm resistances? wiring your subs up in parallel will drop the ohms in half from what i read. when you 1/2 your ohms it increases the amount of watts that the sub can be fed. thus some amps will be stable @ 2ohm, some wont, some even as low as 1ohm.

Do you get better SQ at higher subwoofer resistance or are these two things irrelevant? i had the same question today, and have read SQ setups using 4 Ohm sub setups

I was thinking that If I bought 2 more of these crappie subs and bridged them to 4ohm then I would still be giving 200 watts to each speaker. i wouldnt buy another pair of those sonys, your amp can output 800x1 @ 40hm, i think to properly utilize this you need 1 DVC sub. i could be wrong, most likely ;p

15" are mostly used for lower frequencies and require more space; Do you think these are not good for SQ?
i guess its dependent on the brand, im sure the RE XXX has better SQ than a 15"RF, but from my guess RF and Bestbuy is your way of going, but your right 15's probably are not the ideal sub for SQ. if space is a requirement and you want SQ over SPL, then even a solid 10" could produce the sound you may look for.

anyways, HTH somewhat
GL :-)




Posted By: hurtado_roberto
Date Posted: September 08, 2004 at 4:15 PM

Can I power these 2 DVC 12 with the amplifier I have; P312D4 (1000 watts peak/ 500 watts RMS). 

If I connect each speaker to a channel droping the ohms to 2, does it mean that aech speaker now has 1000 RMS and 2000 Peak at 2ohms?  In that case my amp would not provide enough power for the speakers right.

Should I buy these speakers or get some P2's with less RMS watts?

Has anyone heard these at all?



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Poly Dollies




Posted By: DYohn
Date Posted: September 08, 2004 at 5:13 PM

DVC speakers do NOT "hit harder" than SVC speakers if they are the same type and handle the same power.  The number of voice coils available are only for wiring flexibility.

Amplifiers produce voltage and have a limit to the amount of voltage they can produce.  By placing this voltage onto a resistance load (your speakers) current flows.  Changing the resistance causes different amounts of current to flow.  See Ohms Law link in the left side of this site.  Since most laymen do not understand voltage and current, "watts" (a measure of power) is the commonly used way of describing this current flow.  So an amplifier's rated power output is the number of watts produced by the current that flows at the amplifier's maximum voltage output level.

In general, higher SQ is achieved by using higher impedence loads on a given amplifier.

In general, 15" woofers have less SQ than smaller drivers but can produce more SPL at the lowest frequencies.  There are exceptions to this.



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Posted By: MBZ oe
Date Posted: September 08, 2004 at 6:19 PM

DYohn

So running an amp at a 4ohm load is better/cleaner than running it at 1ohm load, right.?



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BOOM, BOOM, BOOM BOOM....




Posted By: hurtado_roberto
Date Posted: September 09, 2004 at 3:18 AM

So does this mean that If I wire my DVC as the second picture above, I will actually need 1000Watts RMS to power it a 2ohm?

If so then what about the first wiring option pictured above; the amp will be presented with a 4ohm load but will the speakers combined RMS be 1000 watts or 2000 watts?

If the RMS of the speakers does change with resistance then if would be wize to wire them as the first picture shows.  If not, then I could wire them so I could get stereo sound. ( although I don't really need my bass to be stereo only to show off with some sound effect cd's) 

What would be the best set up for this system?  Should I consider getting p2's instead?



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Poly Dollies




Posted By: stevdart
Date Posted: September 09, 2004 at 8:32 AM

I have a RF P8002 amp with

200 W x 2 @ 4 Ohms RMS
400 W x 2 @ 2 Ohms RMS
800 W x 1 @ 4 Ohms Bridged RMS

These are the specs you gave for the amp.  The specs do not increase because you add more speakers, they remain the same.  The amp will provide 400 watts at a 4 ohm load.  800 watts at a 2 ohm load.

You make the choice whether you want to run subs at 2 ohm or 4 ohm, then buy subs with coil configurations that will wire to the load you chose.

RMS of a speaker does not change.  A speaker with dual voice coils wired in parallel has the same RMS capability as the same speaker with coils wired in series.  The change occurs to the amplifier. A lower ohm load will cause the amp to produce more power, but not as clean as the higher ohm load.

And connecting a sub to each channel, yes, is a stereo setup.  But you won't hear sub frequencies in stereo.  It will still sound mono. Stereo sound begins to occur when the frequencies get high enough that you can pinpoint the location of the sound.  Frequencies below 80 to 100 Hz are omnidirectional, in that you can't locate where they are coming from.  They seem to be everywhere at once.



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: DYohn
Date Posted: September 09, 2004 at 9:51 AM
MBZ oe wrote:

DYohn

So running an amp at a 4ohm load is better/cleaner than running it at 1ohm load, right.?


Right.  In general.  Some amps can sustain low distortion and high S/N ratio at lower impedences, but not many.  I run my SQ setups at 8 ohms or higher.



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Posted By: MBZ oe
Date Posted: September 09, 2004 at 12:08 PM

DYohn] wrote:

/p>

Right.  In general.  Some amps can sustain low distortion and high S/N ratio at lower impedences, but not many.  I run my SQ setups at 8 ohms or higher.


DYohn, So does your SQ setup sound "Superb" at 8ohms?

I wonder how much my 1200.1 Kicker amps put out at 2ohm or 4ohms at 14.4v? Right now they are running at 1ohm. 



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BOOM, BOOM, BOOM BOOM....




Posted By: MBZ oe
Date Posted: September 09, 2004 at 12:20 PM

stevdart wrote:

And connecting a sub to each channel, yes, is a stereo setup.  But you won't hear sub frequencies in stereo.  It will still sound mono. Stereo sound begins to occur when the frequencies get high enough that you can pinpoint the location of the sound.  Frequencies below 80 to 100 Hz are omnidirectional, in that you can't locate where they are coming from.  They seem to be everywhere at once.

hurtado_roberto, What Stevedart said above is true but there is a difference when you set it up in stereo. Even though you don't hear what direction the bass is playing from, you do feel it  differently(provided you have monster bass) . When you play a stereo bass song you will fell your car shaking one way or the other. My second to last setup was in stereo and it would rock the car from side to side because of direction of woofers. For this to work though you cannot use your sub-out rca's from head unit because they are mono. You have to send a full signal and use your crossover/s to cut high fequencies. 



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BOOM, BOOM, BOOM BOOM....




Posted By: jeffchilcott
Date Posted: September 09, 2004 at 12:31 PM
i would say if you are really trying to achieve SQ.   go with a single 10 or a single 12.   For the time I am running one eclipse TI. running 800rms to the one sub and I can still blow everyone's doors off on the road and still achieve a great quality of SQ

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place




Posted By: hurtado_roberto
Date Posted: September 09, 2004 at 2:05 PM

A two channel amp is like two separate amps in one unit right, so if I bridge the two speakers or if I connect them in stereo each channel will still be presented with a two ohm load.

I think I finally understood.

Are multiple subs mostly used for SPL competitions?



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Poly Dollies




Posted By: jeffchilcott
Date Posted: September 09, 2004 at 4:58 PM
multiple subs are used for day to day head pounding to spl yes.    commonly i have only seen 1 sub maybe 2 in most SQ cars,    they arnt going for the pounding bass but a low end to compliment the mids and highs....dont get me wrong i always say 10's for SQ but I did see a memphis audio vehicle that was running 1 power refference 15     so you ever know

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place





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