i just returned my 600w, 4 ohm, mono-channel Bazooka amp back to Circuit City, and they gave me store credit ($200 worth) what should i get?

oh yeah, and the reason i returned it was cause it kept over-heating and cutting out on me. i had it hooked up to 2 10" Sony Explode subs (4 ohms, 700w capacity each) and im just looking for something that produces the same sound (if not better) and that will actually work for more than an hour.

(pick from this list: )
http://www.circuitcity.com/frame1.js...ftchildcat.jsp

 

they have a few alpine amps there at CC...i bought an open box MTX8302..which is 425 x 1...not sure what it powers on 2 channels..but it was only 179.00....they also have some KENWOOD amps there at CC...they got that one 729s which runs at 600W max...300x1...150x2...its about 170.00 - 200.00 i think...but be careful with KENWOOD..they're known to overheat a lot...unless you have the excelon series which have built in fans...

 

ok, i have a question... i was told before that the reason my amp was overheating so much was because it had 4 ohms per channel (w/ only one channel) and my subs needed 4 ohms each, so when i split the connection, i was only putting out 2 ohms per sub, but the subs were trying to get too much power out of my amp that it could safely produce, thus over working itself and overheating.

so...should i get a 2 channel amp, instead of a mono channel? or, is it safe to just use the mono and use a different brand of amp that hopefully wont overheat as much...

 

uhh...some amps are prone to overheating....when i was there at CC...some guy wanted to buy a BAZOOKA amp and the salesperson discouraged him and said they were crap...just what i heard...i had a kenwood that overheated a lot..got rid of it and got a different amp...

 

ok, so are there any amps that are good at NOT overheating? i was thinking about the Sony Xplode that they had there, but i heard some bad stuff about them. the guy at CC suggested it, and i compared the stats of it to the others there and it seemed to be the best.

 

I wouldnt waste your money on a sony amp...IMO they are pure crap
no way those amps put out the power they claim....

 

yeah i know, the amp says 1000w on it, but when i checked the stats on it, it says like 500w max power output. so, if the sony's out, what should i get? one of the alpines?

 

ok, i keep looking over the CC website, and i have NO IDEA what to get! seriously, i need some help, i dont know whether or not to get a mono, 2 or 4 channel amp, how many watts per channel is enough to sound good, whether or not its a good idea to bridge a 4 channel amp to 2 10" subs, which ones will/wont overheat easily, what a "Class-D" amp is, etc etc. im about to just pick out the shiniest one and call it a day...


[Modified by i, 7:52 PM 3/26/2003]

 

Are your subs svc. If so then you need a 2 ohm stable amp. JBL 600.1 will work nicely. 600 watts at 2 ohms class D.

 

I don't see why you ever got store credit for the amp...that sucks. I also think who ever sold you that setup should be fired too....

Let me just explain a few things to you, becasue it seems like you have the nomeclature and concepts a bit askew when it comes to amplifiers and hooking up subwoofers - and that's ok...no one is born knowing this stuff

The first thing you have to know is that all subs are rated to have a particular nominal impedance. This number (often called the resistance or load) is used to help match the subwoofer to the amplifier. This number is measured in ohms (signified by the use of the greek uppercase letter Omega).

The next concept is that an amplifier simply reacts to the load that it "sees." It's very similar to something like a dyno plot...based on what RPM the motor is at, it makes different levels of power...the same is true for amplifier power and impedance. Generally, as impedance decreases, power increases. As a rule of thumb, when you half the impedance, you double power. Meaning an amp will theoretically make double the power at 2 ohms that it does at 4 ohms.

The absolute RULE of car audio (and there are very few of them) is that everything is a tradeoff!! So now that you have halved the impedance and you are making double the power, the amplifier needs more input voltage, produces more heat, and distortion has increased.

Here comes the magic rating numbers on each amplifier. After reading the above paragraph...you should thing..."Well great, let's get some 1 ohm subs, and we'll make TONS of power!!!" Unfortunately, it's not that simple. You can only decrease the load so far...as load decreases, so does stability....this would be analagous to increasing the FSB when you are trying to OC a computer...you can only push it so far.

So, if we keep the amplifier happy (by not forcing it to power a load the is too numerically low for it to handle) we can power as many subs as we want. To determine what load we are presenting to the amp, we need a few equations.

With n resistors in series:
Req = R1 + R2 + R3 + ... + Rn

With n resistors in parallel:
Req = 1/[(1/R1) + (1/R2) + ... + (1/Rn)]

So let's look at your two options with your 4 ohm subs. So in this example, with 2 subs, n = 2, therefore:

In series --> Req = 4 + 4 = 8
In pareallel --> Req = 1/[(1/4) + (1/4)] = 1/(1/2) = 2

So, you can only wire these subs to present two loads to an amp, either 8 ohm or 2 ohm mono....mono meaning you only need one channel.

Now, you Bazooka amp (let's assume it's rated to 4 ohm mono) would have been plenty happy at 8 ohm mono, and would have run all day without over heating. Unfortunately, it would have only made half it's rated power. At 2 ohm, you are exceeding the specs on the amp. There are some protection circuits to help keep the amp from blowing up due to extreme loads. This means that you were running the amp too hard, and it was shutting down to protect itself.

So, the moral of the story is that you need to find an amp that makes maximum power when bridged to a 2 ohm mono load.

I hope all that made sense btw.

Let's start with the classes of amps. There are many different classes, the most common are class a/b and class d. There are also class a amps and class t. The class signifies the circuit topography used in the amp. There are a few generalizations that are used when comparing them...let's just stick with the most popular two:

-- Class A/B - this is your "typical" full range amplifier. It's probably the most common ones out there. They come almost any channel config you want, 2, 3, 4, 5, 6 and even 7 or 8 channel models.

-- Class D -- these amps are relegated to subwoofer duty only. They are only accurate in a small range of the audible bandwith. This is why they can only be used for subs. Some people feel that Class D amps don't "sound" as good as a Class a/b amp...I'll let you decide. These amps are typically more efficient, so they can make more power while staying cooler and drawing less current from your charging system...they are also typically able to handle lower numerical loads then class a/b amps. It's not odd to see Class D amps to be rated at 1 ohm mono. These amps are also typically cheaper per watt then their class a/b counterparts.

Now, you can hook up a 4 channel amp to two subs, it's easily done, but for the sake of simplicity and your small budget, I would suggest you get a mono amp designed specifically for subs.

Because you subs when wired in parallel create a 2 ohm nominal load, you will be hard pressed (especially for your budget) to find a 2 channel amp that will power them.

If you can, use that 200 on something else at circuit city, go to Ikesound.com and go buy a JBL BP600.1 - that amp will give you the power you want (an honest 600W) at 2 ohm mono....perfect setup.

If you are stuck at Circuit City, your selections are REALLY limited...Probably either something MTX, Sony, or Alpine. Just make sure you look at the RMS power rating at 2 ohm. That's the number you should look at. Peak or Max numbers are worthless.

I hope that clears a bunch up for you...feel free to ask more questions if that doesn't cover it all...

 

thanks a bunch for all that info! some of the stuff im not sure i fully understand (like those equations, i mean wtf? ) but thanks for the detailed explanation, it helped a <U>LOT</U> now i feel like i can actually make an educated purchase instead of going into this blindly like i have been doing. i really wish i could have gotten money instead of store credit, cause that Jbl amp sounds real tempting