Matching amp with sub

[jeffsun]

hi im new to this forum and have a few questions about matching an amp with the sub.

Im pretty much deadset on gettin a JBL gt0804 for my stealth setup.

Problem is im having troubles finding a good amp to pair with it.

I was originally going to go with a 1000w clarion amp but I understand now that is overkill.

What should i be looking for to power this small sub?

My headunit pushes 4x65w Average Power, 4x45w RMS and i like how it made my stock speakers sound already, so i think ill be focusing the amp to the sub.

Any info appreciated

thanks

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[LosIsATool 5,000+ posts]

Your head unit my put out 10 watts.

 

[jeffsun]

so what amp should i get?

whihc specs should i be looking at?

specs for the jbl sub:

Power handling, RMS 200W

Power handling, peak 800W

Frequency Response 30Hz – 400Hz

Sensitivity 91dB

Impedance 4 ohms

 

[zinda 10+ year member]

First thing to consider is your application. You mentioned a stealth set up, so how much space do you have to work with? What made you pick the JBL sub? Where is the mounting location going to be, trunk under seat behind seat, hatchback, in door, rear deck? These are things that what will determine the sub to start with in the first place. If you are needing a shallow mount sub, a small enclosure sub, a free air or large enclosure, ported, sealed. So the first thing I would do is get the box made if you are limited on space, then determine the volume in cubic inches of room, then consider where it's to be mounted as far as how well it will be able to produce sound. There has to be nothing blocking the front of the speakers for at least 4 inches to properly form sound waves. The type of box you plan to make will be determined only if you have plenty of room to work with but since it's a stealth mount system I'm not even going to toss that into the options. I'm going to guess you will be looking at a small ported box if it's mounted any place other than under your seat, that means you will be looking for a sub that will work well within the parameters of your box and handle the power you will be applying to achieve the sound you need. If you're using deck power you will not need much power to match up with your speakers. That kinda makes all this searching and thinking about it needless, but at least I can give you some advice to use when you decide to upgrade. With that said I always advise anyone who is just thinking about buying their first amp to always buy a medium powered 2 or 4 channel amp 50w RMS per channel and can be bridged in mono either 4 into 2 channels or 2 into 1 channel. I say this so the amp can later be used as a mid/high amp for your speakers that are now on deck power. An active crossover on the amp would be advised also to make the transfer simple. I'm pretty sure that everyone who has ever visited this site has upgraded their system, even if they said they had no plans to do so, we all do, we all do not make the correct choices nor do we actually listen to what others have suggested. Mistakes are made and le$$ons are learned the hard way.

 

[zako 10+ year member]

I just googled it, and it appears that the subwoofer does not have that much power handling, which means you can buy a cheaper less powerful amplifier, like one of the lower end PPI Black Ice mono block amplifiers. The downside, the cheap amplifier will become a paper weight if you decided to upgrade the subwoofer.

I would recommend that you take a look at MB Quart REF1.800 that's sold by sonicelectronix for $110 right now. I believe they're just selling off their old stock. These were good, solid amplifiers, but I think discontinued by now. Another interesting amp is Boston Acoustics GT-2125. They sell for for $110. This was a high end brand, with this amp normally priced at $300, but BA has exited the car audio, and some vendors are just getting rid of old inventory.

Another possibility is to buy a 4-channel amplifier. You two channels to power the front speakers, and two other channels bridged for subwoofer.

 

[nas786 10+ year member]

your sub handles 200 watts rms at 4 ohms, so ideally that's what you're gonna wanna target. If you're a little over or under, its probably no big deal, u could probably be at 150-300 watts without having much issue. Just make sure you read up on how to properly set gains when u install it. That mb quart posted above seems to fit the bill pretty nice

 

[zako 10+ year member]

I personally recommend to always go over the subwoofers power handling, if you can afford it. A 200watt RMS amplifier means, if the rating is accurate, that you get audible distortion at the rated output. In fact, you can expect that such amplifier will behave well up to 150watt RMS output, and then the distortion will explode, reaching into audible range pretty fast. Just take a look at the picture, which is typical of what you get with a quality amplifier. The one on the picture gives 480watts RMS output with 4ohm load, but it's clearly starting running out of steam at 400watts. So if you need 200watts RMS, it's much better to have say 300-400watt amplifier. This way if you send 200watts to your subwoofer, those will be truly clean, low distortion watts. Of course, the downside is that this is more expensive, but what's cheap if you're building a good sounding audio system? Another thing is that amplifier ratings are often done at 14.4V, but in a lot of cars and installs the voltage seen by the amplifier will be lower, which means lower RMS output. This could happen due to flimsy factory wiring, battery, or poor amplifier power or ground wire.

 

[jeffsun]

ah okay so i need to match the rms power with the amount of ohms in the subwoofer.

yes right now i have the enclosure; its a ported enclosure which fits in the jack stand area of a mazda3.

the seller is also selling this amp; a Clarion DPX1001.2 amp

would this be a good amp for my setup?

it would seem to be good as at 4ohms it will push out 150x2

edit link to clarion amp specs: http://www.shopping.com/Clarion-DPX1001-2/info#keyFeatures

 

[prajeet 10+ year member]

@ Zako... best solution.

 

[n2audio 5,000+ posts]

I think Zako is having trouble reading that chart.

That particular amp is at 0.02% THD at 200, and jumps ALL THE WAY UP to about 0.06% at 400w!! (yes, that's sarcasm)

0.06% thd is still more than 10x less than what is generally considered to be the audible threshold of distortion (1%).

I'm all for head room, but this example is irrelevant.

Yes, distortion tends to increase as an amp reaches its power limit, but any amp that's even reasonably good quality will meet its power spec with no signs of stress -- certainly nothing audible.

All you need is a basic 2 ch amp that bridges to 200-250w rms at 4 ohms. They are everywhere. There are probably hundreds that would work well.

A really nice amp: Image Dynamics i2300 2-Channel Class AB i Series Car Amplifier

GOOD amp: Rockford Fosgate P200-2 Punch Series Compact 2-Channel Amplifier

Cerwin-Vega VEGA250.2 (Vega 250.2) Class AB 2-Channel Car Amplifier

Cheap but effective: Precision Power PPI S200.2 (S2002) 2-Channel Car Amplifier/Amp

The clarion you linked would be a HUUUUGE amp for your sub.

With a 2 ch amp you'd want to bridge it to eliminate left/right issues -- at 4 ohms bridged that amp is capable of around 600w rms. I think you might have overpowering issues at higher volume even with the amp turned all the way down.

I'm curious about your HU. The only HU I know of that will do more than 20-22w rms per channel would be an alpine with the power pack.

 

[jeffsun]

ah okay thanks n2 makes a lot of sense.

i knew clarion amp was overpowered but i didnt know what would happen if i put an overpowered amp onto the sub.

im looking at an MB Quart amp FX4.50

do you think this will work?

if anything i can bridge it and run 200w to the sub then i can run either all my speakers or just my fronts with the remaining channels

for my headunit, im using an eonon d5102 - google it for specs; seems like i cant post links or my reply wont go through