Help with Amp in $200 - $300 range

[sarge_in 10+ year member]

I am looking at getting the Focal 165KR components up front, and perhaps some coaxials in the rear. Would like to get your suggestions on a decent amp for this.

Trying to decide from these:

1. Alpine MRP-F550 ($210)

2. Audison SRX 4 ($250)

3. JBL GTO1004 ($250)

4. JL Audio G4500 ($250)

5. JL Audio 300/4v2 ($300)

6. MTX 704X ($250)

7. Rockford Fosgate T400-4 ($290)

As you can probably tell, I have just started out with car audio, so am limited in knowledge of different brands and their relative +/-.

Have heard/read good things esp about Audison, JL Audio and Rockford. How do these 3 compare?

Also, am not planning on a sub yet, but considering if I got one in future, I may prefer to have just 1 amp instead of 2. So I am thinking probably drive fronts and rears from the amp for now, and if I get a sub later move the rears to HU and drive sub from the same amp. What do you think of this? I realize I will not get a lot of power to the subs by this route, but I am not a huge bass fanatic //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Thanks!

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[S10DRVR 10+ year member]

Use this to compare:

Quoted from osixfrontier...

"Everything You Need to Know About Amplifiers:

Lets start off by saying that you can hook any amplifier to any speaker you desire as long as you do not exceed the minimum ohm rating of the amplifier. For example if your amp says the lowest ohm load you can run is 4ohm mono then you do not want to put anything lower than a 4ohm speaker(s) load on the amp. Yes a 10 watt amplifier will play a 5000 watt speaker.

Important: The speaker does not have the ability to tell the amplifier "I handle 1000 watts". The amp does not have the ability to read what kind of power a speaker can handle. So when you here someone ask or say "will that amp push that speaker", it is a dead end question. Of course it will push the speaker, it's just that if you have a 10 watt amp and 100 watt speaker, the speaker is just able to handle more power than the amp can deliver. This will not hurt the amp or the speaker but PLEASE PLEASE PLEASE read about clipping and distortion.

What the specs mean:

THD= Total Harmonic Distortion (measured in %, the lower the % the better. Lets say you are playing a 100hz note, THD is where you may encounter at 200hz note at the same time. Lets say your THD is .05%,

this means that only .05% of that 200hz note will play at the same time as the 100hz note, thus, the lower the number, the cleaner and less distorted the sound at any level.

S/N Ratio= Signal to Noise Ratio (Just like it says, how much true signal (audio) do you have vs. noise in the signal. The higher the number the better. For example, if the S/N ration of your amplifier is 100db, you will have perfectly clean signal.

RMS and PEAK power= (Let me start by saying that if you are looking at an amp that specs an amplifier in Peak power, beware, as an amplifier does not have a peak power, it just has power and nothing more. It's not like it can somehow pull extra power out of nowhere. They should be rated in "Power" or RMS Power, not Peak power. An amp will only do

what it is able to do and no more unless you drop the ohm load the amp sees from the speakers, then the amp will send more power but this is not "Peak" power. Read about rms and peak power in this tech page to fully understand this.)

Damping factor= This is how tight the sound is in a way. Imagine a big ol floppy rubber band, this is a low damping factor. Now imagine a tight rubber band, this is a high damping factor. The higher the

damping factor the better. When a signal is applied to a speaker, the speaker moves and then after the signal is finished the speaker moves back to it's setting position. The time it takes for the woofer to get back into setting and ready position is damping factor. Amps like old Kenwood basic or Adcom or Crown K1 or K2 (not the cheap junk on their bottom line) will have a damping factor of 1000 or so and that is awesome! A good damping factor is around 400 to 500. An average damping factor is around 200 and anything less is defiantly cheap. High damping factor is achieved through the use of extra output transistors in parallel. If the amp you are looking to buy does not spec THD, S/N ratio and Damping factor, beware because obviously the manufacturer doesn't even know anything about the amplifier they are selling. These are important specs and all amplifiers have them.

Headroom= just that "headroom" Some amplifiers are over built and that is a good thing. Like old Carver or Phase Linear or the Crown K1 and K2 series amps have massive headroom. Basically, these type of amplifiers use an over sized or n-regulated power supplies so that when there is a huge draw of power, the power supply can handle it. However, they must also have the output transistors to back them up. Extra transistors in parallel will give you the higher damping factor and an oversized power supply will give you the headroom. (please read about clipping in this tech page).

Frequency response and bandwidth= This is the frequency range the amplifier will play. Sound is in octaves and for example; when a 15khz note is struck and played through amplifier, the amplifier needs to be able to play out to 30khz because 30khz is one octave higher than the 15khz note that was struck. Most decent amplifiers should play out to

100khz.

Slew Rate= this is the measurement in milliseconds of how fast the amp can go from 0 volts to max volts (output). The slower the amp, the lesser the quality.

Matching ohms: This is so important and the cause of half of all blown amplifiers. So many people do not understand this and will tell you bogus information. If the amp can handle at max a 4ohm stereo load, that is the lowest ohm load you can put on it. If it says 4ohm mono or bridged (same thing), that is the lowest ohm load you can put on it. If you do otherwise, you run the risk of blowing the amplifier and nobody will warranty that kind of abuse.

Do's and Don'ts:

1. Always turn down the gains before you turn the amp on or off.

2. Never disconnect or connect electronics or speakers to the amp

while it is on.

3. Never get the amp wet or spill anything on it.

4. Never take the top off and mess around inside the amp unless you have been authorized by the manufacturer or it is just some old amp you bought used.

5. Don't plug the speakers into the "Inputs" of the amplifier, plug them into the speaker outputs.

6. Try to keep your amplifier in a well ventilated area.

7. Avoid driving the amp too hard causing clipping on output signal. You can't always hear clipping before it does damage. Clipping will damage both the amp and especially the speakers. In fact, it is the cause of 75% of all speaker damage. In fact most speakers are blown from using too SMALL an amp.

8. IF YOU HAVE A QUESTING ABOUT WHAT YOUR DOING, THEN ASK!"

And look on this link to look at specs and guts

http://www.realmofexcursion.com/ampguts/

 

[sarge_in 10+ year member]

S10DVR - Thanks for all the info. While I do have a good idea about most of these, it is a good reference to the most important terms and their descriptions! Actually, I did do a comparison of several of these (though not all), and while it may not be easy to read below because of no tabular format, here is the info I had gathered. BUT, these are just numbers - I am looking for real world knowledge that may not be reflected in these. E.g. RF amps are usually underrated, etc.

Still looking for suggestions from the list below - or entirely new one in the budget range.

# Make Model Sonic Woofers 4 ch @ 4 ohms 4 ch @ 2 ohms 2 ch SNR (dB) THD Sp Level i/p Preamp o/p

1 Alpine MRP-F550 $210 $250 90 125 250 100

2 Audison SRX 4 - $250 60 85 170

3 JBL GTO1004 $250 - 100 150 300 104 0.05% No Yes

4 JL Audio A4300 $190 $250 70 110 220 104 0.08% Yes Yes

5 JL Audio G4500 $250 $270 80 125 250 104 0.10% No Yes

6 JL Audio 300/4 v2 $400 $300 75 75 150 108.5

7 MTX 704X $250 - 70 105 210 75 1% Yes No

8 Rockford P400-4 $260 $250 50 100 200 85 0.05% No Yes

9 Rockford T400-4 $290 $286 60 100 200 85 0.50% No Yes

 

[speedfreak28 10+ year member]

I have a 5 month old srx4( The new model), mint condition, 200 shipped, shoot mea pm if interested

http://www.caraudio.com/forum/showthread.php?t=386863

 

[sarge_in 10+ year member]

Thanks speedfreak, but I am leaning to get something with little more power so I can perhaps run a sub off it as well in future.

The dealer recommended the Arc Audio KS300.4, which is 90W RMS x 4 @4ohm. What do people feel about this one, and how does it compare to other amps listed above?

Thanks!!