Amp for Infinity Kappas

[silentrecon487]

First, I wanna apologize for this thread, as I'm sure you get tons like this, but I'm really clueless at car audio and dont want to end up spending money on something that sucks.

I've got an 02 Ford Explorer. Everything is stock audio except my head unit, a Sony CDX-GT520. I'm thinking about getting some Infinity Kappa 682.7 speakers (6x8) for my car. Crutchfield recommended these, and they seem pretty good, so I hope I at least got that choice right. If I didnt, let me know.

Anyways, since the RMS on those speakers are 2-100w, and my head unit apparently on has 17RMS x 4, I most likely need an amp for these. I was also recommended by crutchfield this Alpine MRP-F550:

http://www.crutchfield.com/cgi-bin/Prodview.asp?i=500MRPF550

However, 300 is a bit pricey for me, so I asked for something cheaper, and he said this Profile AP200 :

http://www.crutchfield.com/App/Product/Item/Main.aspx?g=120&i=575P3252&tp=115

But I'm still pretty lost. The second amp just feels cheap to me, both price wise and quality wise. After seeing the $300 one, it just seems like that one wouldnt work well. But I'm clueless, so it might. And I dont get why some amps are like the same power but double the price.

So, any recommendations for a good, somewhat cheap amp? I'd say 200 is probably my max. I just want something that will power those speakers, but is also reliable and whatnot. Thanks

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[jblayz1 10+ year member]

if you have some patience, do some reading on here and check out the classifieds for better deals.

 

[Betrayer00GT 10+ year member]

You could get the one that is actually at your first link (a $150 RF Punch P325.2), or you could get the P550.2 for another $50, @ $200:

http://www.Crutchfield.com/App/Product/Item/Main.aspx?g=120&i=575P5502&tp=115

If you are set on buying at crutchfield, that is. I can see why, they have absolutely killer customer service, and with the amps above, are not much more than anyone else.

Or, just to see if you really think you need to spend as much as everyone else always seems to think you do, you could get a California-series 400SX for $45, straight from the manufacturer:

http://www.profilecaraudio.com/amplifiers.htm

I got a CA200, and a 400SX. If they do not do it for me, I am out all of $84 for both. If they do... well, I was going to spend $300 - $500 on Soundstream stuff before that. I still might. But I might not, too. If you can wait that long, I can eventually report back on how they work in my case. I have them both (got them 2-days after I ordered), but I have a tendency to drag projects out a bit. //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

Remember, this is supposed to be fun. It can be expensive, but it has to be fun. Enjoy!

 

[silentrecon487]

So why are there some amps that are $45 or $80 that can give as much power as a $200?

 

[Betrayer00GT 10+ year member]

So why are there some amps that are $45 or $80 that can give as much power as a $200?

Well, the amps I own were refurbs straight from the manufacturer, not new-in-box from a retailer, so that can account for some of any price difference. Not all of it, of course.

Well, I am not familiar (enough) with amp design, but I am with passive crossovers. So, from there, lets examine potential price ranges for the same component in rated value, but with different manufacturing method, tolerances, and brand:

12uF capacitor:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=027-742

12uF capacitor:

http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=027-342

Some say there is a difference in the sound of those two in a passive x-over circuit, but there is definitely a size/weight and longevity difference. No one can argue anything on those last two. Now, if you need a cap that is very stable in value with usage over more than a decade, don't get the $.4 one, although the $50 one could still be rather significantly past the useful price/performance ratio for your preference. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

And, since there not just capacitors in passive x-overs (or amplifiers, though I am less familiar with the values/tolerances needed there):

4.7mH inductor:

http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=255-748&DID=7

4.7mH inductor:

http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=266-566

Of course all this component cost doesn't even cover the passive x-over specific issue of using a 2.2mH inductor instead of a 4.7mH one (the lower value would be cheaper, no matter which mfg/type you used), and just running the woofer/mid a bit further up the frequency range. You may now be running it with more output at its primary break-up mode (in, say an aluminum cone 8" driver), but the x-over would cost less.

That is a (basic) passive x-over network scenario, but I guarantee you there are the same kinds of trade offs available to an amp designer vs a passive x-over designer, it is just I do not know exactly what they might be.

Then there is the "made by the cheapest bidder and the final product isn't even remotely close to what the circuit designer assumed in his design phase, as too many manufacturing corners were cut", and now it is impossible to maintain the full integrity of the design. All the way to made-by-hand, in the US, by a guy who has been building amps (or other high power circuits) for the last ~20 years, and who throws out one of those $100 4.7mH inductors because it appears to have a slight mfg defect that could possibly affect the reliability over time. Then, since he tests each component before placing it in any product, he throws out another because it is measuring @ 4.55mH (> a +/- 3% difference, which is the target his boss has him confirm each component complies with to ensure a top quality product, when +/-10% is typical in run-of-the-mill electronic components and the cheap stuff can be +/- 20%), so it will not be used.

So, still think that if one amp costs $90, and outputs just fine when it is tested leaving the factory (some might fail at first and need the problem corrected before trying to pass again, but not this one) there is a problem if another amp from a different line @ the same company has the same exact measured output, but cost $200? There is a lot that goes into cost. Also, what if one of the $90 units, after failing the first time through, gets "fixed" and is then sold at a refurb outlet for $45 because the guy who fixed it makes a couple dollars an hour? I don't know for sure how anyone operates, but these are all scenarios that are not out of the realm of possibility if the price is right to cover the expense involved.