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selecting amp

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=53577
Printed Date: May 11, 2024 at 3:20 AM


Topic: selecting amp

Posted By: vette00057
Subject: selecting amp
Date Posted: April 08, 2005 at 11:54 PM

Ok, I'm a little confused here, I have a friend who said that i need to get an amp that will not under power my speakers.  He said that it is easier to damage my speakers by underpowering them than by overpowering by burning out the voicecoil.  I do not understand why that is true or if it is. Could someone please explain?  Does this mean i have to get an amp that has more continuous power than what my speakers can handle and turn the gain down or does it mean that i can't get an amp that will grossly underpower (e.g. an amp that puts out 25W RMS to speakers that can handle 100W RMS)  my speakers?

About my system;  I have front components that can handle 140W RMS, rear 2-ways that can handle 80W RMS, I would like to get a sub like the JL 12W3v2 that can handle 300W RMS.  The amp i am looking at is the JL 500/5 that is 100W RMS x 2 at 4 ohms for the front, 25W RMS x 2 at 4 ohms for the rear, and 250W RMS x 1 at 1.5-4 ohms for the sub output.  would this amp work well with the speakers i have listed above?




Replies:

Posted By: geepherder
Date Posted: April 09, 2005 at 8:34 AM
Underpowering is actually safer as long as you're not driving the amp into severely clipping the signal.  Don't turn it up so loud that it distorts like crazy.

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My ex once told me I have a perfect face for radio.




Posted By: sedate
Date Posted: April 09, 2005 at 10:42 AM
Whoa Vette.

Man that JL Amp will knock ur socks off with that equipment.

If your friend thinks that JL Amp isn't 1000% badass you need a new friend. This guy doesn't understand equipment like this... also, please keep in mind that this series of amps from JL plays a right bit higher than rated.. I recall seeing several reviews of these amps putting out 20 and 25% more than thier rated power on a test bench..

Okay, the amp.

100x2 - Front Speakers
This is intended for your front channels, your componets will *love* 100 watts. They certainly do not need 140, (I don't care what kinda comps they are, 100 JL watts will run them fantastically) nor will you notice anything but perfectly clean sound. These speakers need to play the loudest and the cleanest for proper soundstage and imaging.

25x2 - Rear Fill
These channels are rated quite a bit lower, and I'm guessing somewhere your friend said that 25 was to low right? Any audiophile will tell you, 25 watts is *just* right. When tuning your system, you would never ask much volume from your rear speakers anyway, they are there to provide ambient fill... not produce any bulk volume. You would quickly find the coaxials in the rear would become much louder than the componets and do so sounding drastically worse... all while pulling all your imaging and your soundstage behind your head. Personal preference plays a role here, but most audiophiles will agree that the proper volume for rear speakers is *barely noticeable*

250x1

I can assure you from personal experience (i've used every woofer in JL's line) 250 watts from an amp like that will run the living snot out of a 12W3... "300watts RMS" or not. Running a single 12w3 of a really crappy Sony amp my friend's Eclipse can be heard a block off.


Vette, lemmie stress one thing.. this is a true audiophile amp. This series of amps from JL is absolutely amazing and the 500/5 is a great choice for that equipment. If you can afford it, that is a great way to go.

You know, waaayyy back 2 years ago when I started my system, that was the very first amp I looked at... I couldn't afford it at the time. posted_image

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"I'm finished!" - Daniel Plainview




Posted By: forbidden
Date Posted: April 09, 2005 at 12:22 PM

You can underpower a speaker all day long, provided the gain on the amp is set correctly and you are full aware that a distorted speaker is something that you have caused. This means that either the gain on the amp is too high and sends a clipped (distorted) signal to the speaker for it to reproduce, or the signal coming out of the cd player is clipped from either the cd itself in the recording process or the level it is being played at. Keep the bass setting a nominal and do not use bass boost settings if it can be helped. Do you have a cd player yet and if so, what kind is it. Great choice on the amp.



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Top Secret, I can tell you but then my wife will kill me.




Posted By: vette00057
Date Posted: April 10, 2005 at 12:37 AM

Thank you guys that really helped out! 

BTW my friend wasn't saying this JL amp is bad, in fact he said it looked really good.  We were just discussing what could damage speakers and he mentioned that underpowering them could.  I just wanted to make sure that the 25W RMS on the rear channel won't damage the 80W RMS coaxs'.  I am also the type of person that always wants to know how and why something systematically works.  I appreciate all of your responses.

forbidden - i have an alpine cda-9827 for my HU.

I currently have an Infinity Reference 7854a amp that puts out 111W x 4 RMS, however i am getting a lot of noise(speaker hiss and alternator wine) and am trying to figure out where its coming from.  maybe you guys could help me with this one as well. ;-)  i know its not coming from my HU because i can have the RCA's and the remote turn on unplugged and the speakers still make that noise. (i jumped the remote lead on the amp to the power wire to turn on the amp)  i tested my ground with a multi meter and i have continuity and shows .015 ohms on the ground which i think would be acceptable.  also my ground cable is the same gauge as the power wire (4 AWG) and its only 3 1/2 feet long.  i plugged in a much smaller amp i think only 40X4 and i didn't get any noise.  i then borrowed a friends infinity amp (exact same model) and hooked it up to my system and got the noise again.  is it possible that this model amp is eather crap or that it won't work on my system for some reason?

one last thing i promise!   i am one who really appreciates good clean sound, not how loud my speakers are or how hard my bass hits.  will this sub be a good choice for SQ or is it known high SPL, or with a 12 in woofer does SQ play much of a role?

sorry about the long post, and thanks again!





Posted By: sedate
Date Posted: April 10, 2005 at 1:42 AM
No, no, I always do run on posts I love it. Heck Vette, did you see how much I wrote about that amp? (Heh, gimmie a chance to write about *any* amp I've lusted over..)

Hmmm.. Yes, it is absolutely possible the Infinity Amp is total crap. The easiest way to tell if something is "Total Crap" is to check where you can purchase it. If the answer is "Circuit City" or "Best Buy" then yes, you have total crap. Sadly, in your case, you have total crap.
Comparing the JL 500/5 to *anything* sold at said stores would be comparing Stonehenge to an arrowhead.
I think you said it yourself when you left *everything* the same and plugged in a different amp.

On the 12W3:

Yea Vette, the 12W3 is a good all-around performer for the money. Personnally, I think there is *much* better stuff for the money but the W3 is a solid all-around choice. I vent about JL subs here from time to time.. to be totally honest, I'm left in *total awe* by JL's amps and componet speakers, but their subs always left me a little cold.. I dunno, I think they sound unnatural.
I swapped out a great pair of 12's for a 13W6 and *seriously* regret it.

And yea, you can get *incredible* sound quality from a properly installed 12-inch subwoofer.


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"I'm finished!" - Daniel Plainview




Posted By: vette00057
Date Posted: April 10, 2005 at 2:20 AM

thank you sedate for the info on the perfect kappas.  and yes i did purchase the amp from a mainstream place from a friend who worked there using his discount of course!  well i learned my lesson on trying to pinch the penny! posted_image

does anyone have expierience with the audiobahn subs?  i have heard some of their higher end stuff and it sounded great.  in fact my component fronts are audiobahn and i am very happy with them.  and why can i find a lot of audiobahn stuff for cheap on the internet.  for example the speakers i bought from carstereodiscounts.com and they were discounted because they where last years model and  a friend of mine bought some audiobahn stuff from there at a greatly reduced price.



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Alpine CDA-9827
Infinity Reference 7540a
111W RMS x 4
Front= Audiobahn ABC600T
6 1/2 in. Componant
140W RMS Power Handling
Rear= Polk MOMO MMC570
5x7 Coaxial 2-Way
80W RMS Power Handling





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