Amp testing/comparison

Thanks, Stevdart! Though.. Shot in the dark? No. Guesstimate? Hell yes. Since a doubling of power is only 3dB, even if i had been 33% inaccurate, that would have been just one dB. Anyway, I realized that with the speakers I have (alphasonik 6.5" two way components, specced at 200w RMS).. I previously used them on the sony amp, the one that produces 2x160w RMS. That was plenty loud. With the woofers high passed around 70hz, I doubt they could really handle much more power than I was feeding it. (Not that 1000w peaks would kill them, but the cone won't move any further than the rubber surround allows no matter what you do).. Perhaps I should just be happy with my front stage. It sounds damn fine, anyway. And now I know, I can choose between the three amps simply based on size and looks! :) If I go for the smaller amp, I could use the extra real-estate for another amp for the tweeters (biamping) and that electronic crossover I never got around to using. Anyone wanna buy an Alpine MRV-1507 or a Sony XM-7547? :-D ///Leif

im curious to see if anyone  has a problem with that???.... i wonder if someone has or could make a subscription site with all of these rating on it....maybe you could get sponsered by manufactuers in an attempt for them to get more money.. or it would make them create better amps to see that people are figured out the real specs

I forgot to thank you for your reply, haemphyst, so thanks :-). Voltage is voltage whether you're looking at clipped kickdrum transients or a near-clipping sinewave - I'm glad there's other people here that understands this too :). Greenlantern, I have a feeling they would just repeat some of Stevdarts arguments (i.e. the test wasn't done properly, our amp works fine in OUR lab) :). ///Leif

ALtho I'm something of a noob here, I'm versed quite deeply in both analog electronics and test methodologies, as well as a tidbit I want to share about the recording industry. One thing I'd like to point out here (aside from the test methodology, which I'll gladly comment on later if desired), is that using prerecorded music for testing is a crapshoot at best. So much of the CDs out there now are clipped in mastering that you don't have a prayer of getting a clean waveform out of them when played back in your system. You'll see a clipped waveform at any level large enough to show you the nature of a kick transient. If you're serious about testing things, make your own CD of known good tones or buy a quality function generator. There's lots of good used Tek gear over on evilbay. -daveThis is not a sig. This is a duck. Quack.

And I differentiate you as a "newbie", not because that's a bad thing, but because if you had been around this forum for awhile you would have found that the people who take time from their lives here are just helping others with the problems they face with car audio installations, not taking the opportunity of widely-read bandwidth to elevate themselves.  So you can get down off your pompous perch and start helping others with tried-and-true solutions to their problems.  Or read and learn, as there is much to be learned from the posters on this site.  Even for you, leaf.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Take it easy, stevdart. I was hearing nothing in Leif's tone that warranted that kind of response. He may be a "newb", but you were once a newb too. (Relatively speaking, I am a newb to this board, but I am NOT a newb to electronics or electronics theory.) I am fairly certain that nobody jumped on you like that if you made any mistakes. The man is here, like everybody, trying to learn and provide some input. If he is a newbie here, that does not mean he is a newbie to electronics in general. I was an electronics technician (6 years) AND a high voltage electrician (5 years) in the Navy, a communications technician for the County of Kern (California) (2 years) and now I design and build home theaters for people (3 1/2 years) I can vouch for his testing. The results he received were sound. The "kick-drum transients" that you were so quick to dismiss IS a real method of testing the dynamic (as opposed to continuous) power of an amplifier. Granted, it is usually done in a lab with a pulse generator, but how many of us have one of those? It is a small function called headroom. An amplifier (depending on the quality and "stiffness" of the power supply) can supply MUCH more power (rated in dB over the continuous output) for a transient attack than it can for a continuous tone. Simply because somebody does not know all of the phraseology, it is not necessary to dismiss him as completely incompetent. I have read MANY of your posts, and you are a smart guy... I have generally respected your point of view. You have posted some valuable input, and you are part of what makes this board as good as it is. I have read things from everybody here that I was not necessarily in complete agreement with, but I was not in a huge hurry to flame them in front of the whole community. I am not saying you are completely wrong, please believe that, but I am simply asking for a little bit of tolerance from you. You might read your own post regarding knowledge, and humility. The way I was reading your last post, it seems you are not necessarily willing to heed your own advice. I think you should realize that you do not know everything, either, and listen a little bit more. I also do not know everything, I am 37 years old, and I have been interested in electronics or have worked in electronics related industry since I was about 6 years old. I knew Ohm's Law by the time I went to second grade. I read EVERY book I could get my hands on regarding electronics. I was building passive series crossovers (are you familiar with those?) by the time I was a freshman in high school. I have BUILT, from piles of PARTS, flame speakers, ribbon drivers, Tesla coils, VanDeGraaf, Whimshurst, and Mark's Generators, Quarter shrinkers, and many other high voltage and audio components. I repair amplifiers (both digital and analog) PC power supplies, and component level repairs on computer motherboards. I am STILL aware I do not know everything. I learn something new everyday. Take a chill pill, man. Read and heed your own posts. I am done with this thread. I will NOT reply to any response directed at me, but I will continue to post elsewhere on the board. I will continue to respect everyone here, so long as the respect is mutual. I will continue to offer advice, whenever I can, and I will continue enjoying doing so.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."

DPaton, ain't that the truth about CDs! It's been a pet peeve of mine for a long time now, and it really drives me crazy. The "Alicia Keys" cut I used for testing IS indeed clipped on the CD. However, enabling bass boost on the discman is a very effective way to round out the waveform. Yes, the odd order harmonics will still be here, but there won't be any flat edges anymore, so for this type of testing, it works. I did take this into account when doing the testing. Also, even if bass boost hadn't been on, CD players generally have some sort of high pass filter in the output amplifier.. The cutoff of this may be very low, but even if it's at 20hz, any squarewave (the clipped edge) on the CD is going to start tilting towards the center. (Only a completely DC straight signal path will be able to pass a squarewave without tilting the flat tops.) Thus, looking at the scope and ramping the volume up, it's still easy to see where the amp clips and where the source material was clipped. (I'd love to show you some screen shots of this, let me know if you're interested. Incidentally, there are Mix CDs that have evidence of this double clipping - they started with clipped source material, then ran it through a non-dc straight analog path, and then clipped it AGAIN to make the cd "loud enough to sell".. heh. Sounds lovely, I promise!) Stevdart, this board labels me a Newbie based on my post count. Having been here long enough to earn the fancy title of "Silver Member", one would think that you would understand this, and not make other assumptions based on it. Haemphyst, thank you. It wouldn't have been right for me to say what you did, but I'm very grateful that you said it. ///Leif