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How to Choose an Amplifier.


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larzzzz 
Member - Posts: 10
Member spacespace
Joined: December 15, 2006
Location: United States
Posted: December 19, 2006 at 3:12 PM / IP Logged  
With regards to amp ratings I assume that max power is generated with transient signals.... a hard crash of the cymbals or a hard bass note etc. The amp is not designed to reproduce such signal levels continuously but can sustain brief periods without distorting the signal or clipping. So I basically cut the max power rating in half to give me a continous power rating of what I think that the amp is capable of running all day at. Just adding another $0.02
i_know_nothing 
Member - Posts: 1
Member spacespace
Joined: February 11, 2007
Posted: February 11, 2007 at 10:55 PM / IP Logged  
first, im not real new to car audio, i just really know about the installing aspect of it, and have minimal Knowledge of the component aspect.
I have two Eclipse 88120DVC (year 2000 model) and i have been looking for an amp to push them.
specs: 500W RMS
1,000W Peak.
The FS - 27Hz,
Qts - 0.30,
DCR - 3.0ohm/coil,
originally i had 2 Alpine MRP-M450 pushing them and they just seamed like they where not doing the job.
the first thing i was looking at was 2 Alpine MRD-M1005.
second was the Audiobahn A12001DT
third was the Orion HCCA-D2400
but please help me...im not even shure if im heading in the right direction.
sethat 
Member - Posts: 2
Member spacespace
Joined: March 14, 2007
Location: United States
Posted: March 14, 2007 at 9:11 PM / IP Logged  
anthony71 wrote:
Here's a good site that discusses some more features necessary when purchasing a car amplifier: guide to car amplifiers. It has very good info. Helped me a lot.
First sentence from the above link: "Car amplifiers convert low-power signals received by car speakers to high-powered signals, improving their volume and sound quality."
Here's something to think about. Theoretically, I have never known of any amplifier in existence that actually improves the sound quality of a signal. This is why every amplifier has a certain percentage of THD. After a signal leaves a head unit, it's all downhill from there.   Every piece of conductor and electronics (even baffles and enclosures) that interfaces with the signal before it reaches your ear is going to cause an incremental decrease in quality.
Another factor that I consider when selecting equipment is distortion.    Start with a good high volt signal and use the least invasive equipment, pertaining to THD, that your budget will allow.
The signal is never cleaner than the moment it passes through the DAC and out of your head unit.
Hey, this post was probably overkill, but it motivated me to finally register.
stop82lp 
Member - Posts: 5
Member spacespace
Joined: March 21, 2007
Location: United States
Posted: March 24, 2007 at 10:11 PM / IP Logged  
haemphyst wrote:
I have seen several (ok, MANY) posts here lately, asking about how to choose an amplifier, with all sorts of "Is this good...?" types of questions.
Here is what I look at when choosing an amplifier, and in their order of preference:
1. Power. I know, this is where MOST people look first, but it's the very reason you are buying an amp, right? Also knowing Ohm's Law, and knowing that I will almost always load an amplifier with the maximum specified impedance (impedance - 4 ohms or higher, NOT load - 4 ohms or lower), I need to know exactly how much power I am looking at to start with. When loading an amp with a higher impedance, the amp will make less power, so I have to keep this spec in mind the whole time. My speakers are almost always chosen before I decide to start looking for an amplifier, I know the impedance and efficiency numbers when I start. This will help me decide how much power I need or want for that particular driver compliment. I will NEVER look at "Max Ratings". They are often worthless, generally overinflated, selling tools, designed by old-school, low-end amplifier companies, originally made to sell product. (You remember how it went (and still goes today)... This 800 watt amplifier is only 200 dollars, but the Nakamichi 160 watt monoblock is 1300 bux for the pair. Which were (are) YOU going to buy?) Ahhhh, the power of advertising... Classic Nakamichi, Alpine, Linear Power, Orion, Eclipse, etc., THEY never posted "Maximum Power" numbers, did they? Unfortunately, even the good products of today will state maximum power output, I just disregard the numbers posted.
2. Signal to noise ratio. This one I place a bit more weight on, especially when the amplifier is going to be used in a mid-bass (important), mid-range (more important) or highs (MOST important) application. The higher the better, and there is no exception to this rule for me. Amps with tube stages are typically less capable than their solid state stablemates in this area, but I do make exceptions for tube amps. It is NOT a terribly important spec for a bass amp, so when shopping for a bass amp, don't bother with this number. Dedicated bass amps, BTW, usually offer awful SNR numbers.
3. Efficiency. Here's where you will be able to tell a decent manufacturer from the crap. Let's say you are looking at an 250 watt (RMS) amplifier. The first physical thing I look at, is how big a fuse do they recommend (or what size fuse is in the end of the amp)? I know right now that 250 watts OUT will demand (and I use 50% efficiency to keep it simple) 500 watts in. 500 watts in, divided by the (car running) battery voltage (14.4v) is about 35A. If I look at the end of the amp, and see a 20A fuse, I'm walking away, as there is no way that amp can make 250 REAL watts, continuously. 14.4v times 20A, equals 280 watts in. 250 watts out, divided by 280 watts in, translates to an 89% efficiency. In a class A/B amp, this is an impossible number, and it even stretches the imagination for digital amps, as well. The theoretical MAXIMUM efficiency for class A/B is 66%, (95% for digital) so someone is lying. I don't care WHO the manufacturer is, if these numbers don't add up, I will start looking elsewhere... Now, if all the other specification look good, AND I can get in the vicinity of the RMS power I am looking for, I will buy an amp that's efficiency number might be stretching the truth a bit. My old Nak 160 watt monoblocks had 40A (that's 480 watts in - a 33% efficiency, people!) fuses in each one, and they ran hotter than a firecracker, even loaded at over 8 ohms. I liked that. How to Choose an Amplifier. - Page 7 -- posted image.
4. Terminals. A frequently overlooked part of an amp, this is a very important part of an amp to me. A car is a place frought with vibrations. A cheap or cheezy feeling connector in power or speaker terminals and most ESPECIALLY in the RCA inputs, will often cause problems in the future. Setscrews for power, quality terminal blocks for speaker outputs, and Tiffany style RCA connections (the type attached to the chassis, rather than a block of plastic soldered to the PC board.) The quality of the I/Os can be a direct indicator of the attention to detail paid to the rest of the piece. Translation? Overall Quality.
5. Heat sink. This one is simple. How does it look? I eventually chose Eclipse gear, because it looked like jewelry. Fine finish and appearance. Also, heatsink size and quality can be another indicator of quality of the amplifier as whole. A heavy heatsink will also provide better thermal stability, a nice thing in an amp.
6. Damping Factor. I used to place more emphasis on this spec, but my research recently (over the last few years, really) has, while not proven to me it is a useless spec, has not proven to me it is an extremely important spec. This is why this particular spec is a little further down the list. While I place a bit more emphasis on it for a bass or mid-bass amp, I, admittedly, place less weight here than I used to...
7. Price. Money rarely means much to me in an amp, (much like my computers - "Life's too short to build slow computers." - David Draper) it's something I am going to be keeping for a long time usually, so I will save if necessary to get EXACTLY (or close to) what I am looking for.
These are the things I look for when trying to decide on an amp. OBVIOUSLY, there are going to be VERY few amps on the market that will make me happy across the board, but then some of the physical characteristics listed above can be made to fit me and my desires with a little time, a couple extra bux, and some careful use of a soldering iron. All of the above things will cost more, but it will ADD more to the finished product as well... How to Choose an Amplifier. - Page 7 -- posted image.
stop82lp 
Member - Posts: 5
Member spacespace
Joined: March 21, 2007
Location: United States
Posted: March 24, 2007 at 10:12 PM / IP Logged  
i have a volfenahg 200 watt amplifier , i also have two 10in cerwib nega v max subwoofers. the amp isnt stable at 1 ohm. but i just want to know the best way to wire themn without blowing anything? please hep a rookie out : )
stop82lp 
Member - Posts: 5
Member spacespace
Joined: March 21, 2007
Location: United States
Posted: March 24, 2007 at 10:15 PM / IP Logged  
i forget they are 600 rms and 1200 watt peak per sub.
ender6456 
Member - Posts: 1
Member spacespace
Joined: March 25, 2007
Location: United States
Posted: March 25, 2007 at 8:50 PM / IP Logged  
Haemphyst, you offered some great information on choosing the right amplifier, but I being a lamen...ended up confusing myself with all that information.  I recently purchased two Audiobahn (yes...i know most people dont like Audiobahn, but they offered the best wattage versus mounting depth that I could find) ALUM10N Subs.  The subs are dual 6 ohms (someone already told me to buy a third one, but the box I have is specific for my vehicle and it only holds two 10's) and are rated at 800w RMS.  I plan on running these in parallel which means they would end up at 1.5 ohms, i think.  Now the difficult part, the amp I had planned on getting was an Audiobahn A2300HCT which is rated at 2400w rms @ 1 ohm.  If I can do math correctly, that means that I will get 1800w @ 1.5 ohms, plenty for my two 800w 10's.  After I found this thread, I tried to do the math and the calculations I got were not good, which made me think that either the amp was really bad or I screwed up the numbers.  FYI: the amp comes with four 40amp fuses.  Any help you can offer would be greatly appreciated, thank you.
haemphyst 
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Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: March 26, 2007 at 5:08 PM / IP Logged  
That amp won't do 2400 watts. It only get 2300 watts in, at 14.4 volts. That amp is probably 1100 to 1200 watts on a good day. I wouldn't run it at 1 ohm, either... 1.5? Close, but I think you'll survive with that.
But, yes, you'll have either 1.5, 6, or 24 ohms to play with...
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
kno88y 
Member - Posts: 5
Member spacespace
Joined: June 30, 2009
Location: United Kingdom
Posted: June 30, 2009 at 3:39 PM / IP Logged  
after reading this im alittle better on bits and bobs but still lacking the whole ohm bit lol, im gussing if an amp doesn't advertise rms/ohms per chanel its not worth buying ??
so if i buy a 1200w amp (600w,rms) and run 4 450w 6x9's (200w,rms) of each channel
this wouldnt work i would need a 2000w (1000w,rms), like i say they dont advertise these details ??
mightylight 
Member - Posts: 4
Member spacespace
Joined: October 18, 2009
Location: Colorado, United States
Posted: October 18, 2009 at 7:43 AM / IP Logged  
SO whats the difference of Load and Impeadance? I have a 3 OHM Subwoofer, would a 4 OHM stable amp work?
cj Lancaster
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