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New member Username: WandaddyPost Number: 1 Registered: May-10 | Hi. I am fairly new to the whole car audio thing. I had a little experience back in high school helping friends install their systems and everything, but I have no sort of professional or industry experience. I am a fan of Alpine and Boston Acoustics products though. I am in the military and live in Japan, so I have to order everything online, and I don't really get a chance to hear systems in other people's cars here(they only sell cheaper JVC and Kenwood products on base). I am going for more of a SQ setup and my car is a little 1996 Nissan Pulsar hatchback. I have already purchased the following for my system: Front Speakers: Boston Acoustics S50 components Rear Speakers: Boston Acoustics S55's I am also looking to buy the following eventually: Sub woofer: Boston Acoustics 12" G3 (I am unsure about single or dual voice coil as of right now) Head unit: Alpine CDE-102 or CDA-105 Amplifier: Something from Alpine preferably I bought the S55's and they are already installed in my car and am still waiting for the S50's to come. I only recently found this forum and discovered that a lot of you guys don't use rear speakers. I would prefer to keep mine, since I already bought them and everything. Also they are only being powered by an older Kenwood head unit at this time. Ok, here are my questions: #1 The first question I have is about using used amplifiers. I am on a budget ($200 USD or less), and I want to get a nice Alpine amplifier to power a 12" Boston Acoustics G3 sub woofer. I have been looking at used ones on Ebay and I am just wondering, is buying a used amp risky? I am just under the assumption that if it works, it works. Are there any internal parts or anything that get worn out over time and would cause the performance of the amp to deteriorate? I had one of those older (maybe mid-90s) Alpine V12 4 channel amps in high school, and it worked great. #2 What kind of setup would work best? I have seen a 5 channel amp from Alpine and Boston Acoustics that could power everything in my car. They are out of my current price range, so I would have to save up a little longer to buy one, but would that be better than a 4 channel amp pushing just my front speakers and a sub, and my head unit powering the rear speakers? I don't think my little car can support 2 amplifiers, and I don't want to have to upgrade the electrical system. Car parts are expensive over here, I just put a rebuilt alternator in this car and it was $400. Crazy, right? #3 If buying a used amp is not really a big deal, could anyone recommend a new or used amplifier (preferably Alpine) that would work for my situation? Anyways if anyone could give me some advice I would appreciate it. I think this is a pretty good site for getting information with a lot of knowledgeable people here. Thanks. |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13394 Registered: Dec-03 | You'e in Japan. You're in the home of Alpine! You should be able to find JDM Alpine products off-base there for reasonable prices. I'd love to be back there again to buy some of their domestic gear. haha OK, anyway, if you don't want to upgrade the electrical system, and you have a Pulsar (I feel for you on that one) I would suggest saving your money to get the right stuff. I don't mean buy expensive gear, I just mean I don't know current pricing, but I do know exactly what's going to work for you here. Get an Alpine deck with 3 pair of pre-outs (don't need any internal power) keep the Boston front and rear speakers. Get the G3 sub (375WRMS pwr handling) now for the important parts: Get an Alpine 500 watt class D sub amp to drive the Boston sub (don't worry about the power output being higher than the sub's rating. It won't matter. If you need, I can explain why but it depends on how much you really care about the details) order up a 2-amplifier wiring kit (4AWG should be sufficient) and a little extra 4AWG wire (maybe 12-15ft) and 6 ring terminals to do the "big 3" upgrade too (this will help your alternator last longer this time) and lastly, you want to look at an Alpine (or other) class T 4-channel amplifier (far more efficient then the typical class AB amps, so less current demand) in the 50 watt x 4ch @ 4 ohm range (40-60 watts range) for fronts/rears. Now what you want to do with that 4 channel amp, is run the fronts on channels 1 & 2 in stereo, then bridge the rear channels 3 & 4 to one channel. Next, you'll wire your rear speakers in series to that bridged mono channel. This will prevent the rears from destroying your sound stage and imaging, but still allow them to work as rear fill. You'll want to set the head unit's or amp's crossover (or use both together to accomplish this) for a bandpass filter, so the rears only do about 500Hz-5KHz range. cut out the lows and the highs. you want them to act as midrange drivers only. You'll just adjust the fader on the radio to attenuate their output till it's barely audible. That's how you run rear fill in a SQ system. As for used amps, the only risk is really getting an amp that's not banged up or damaged, but if it's advertised to be in good shape, and you look on ebay, then use paypal and a credit card to pay for it. If the amp does arrive in bad shape, you have recourse with both eBay/PP, and the CC company to get the money back if the seller is shadey. I've bought used amps though, and they've been just fine. Here are a few links that may help on some of this: (scroll down to "amplifier classes, class T) http://www.glasswolf.net/papers/ampspecs.html how to adjust your amplifier gains: http://www.glasswolf.net/papers/dmmgain.html what is the big 3? http://www.glasswolf.net/papers/big3.htm rear fill info http://www.glasswolf.net/papers/rearfill.html best of luck. |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13395 Registered: Dec-03 | http://www.amazon.com/Alpine-M500-MRP-M500-Amplifier-1-channel/dp/B0013TQ6FK alpine mrp-500 sub amp. $145 new http://www.amazon.com/Alpine-PDX-F4-4-Channel-Digital-Amplifier/dp/B003GFZ6RI Alpine 4 channel digital amp $342 |
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New member Username: WandaddyPost Number: 2 Registered: May-10 | Hey thanks a lot Glasswolf, you have been very helpful. I think I am going to take your advice and try for that set up. Thanks again. |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13405 Registered: Dec-03 | if the class T digital amp is too pricey just look for a 50x4 class AB alpine amp. tons of them on google shopping, ebay, and amazon |
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New member Username: WandaddyPost Number: 4 Registered: May-10 | Hey I have another couple of questions. What about running a 5-channel amp like an Alpine PDX-5? Would that be simpler than having 2 separate amps? And if I did run two separate amps, would a 4 gauge multi-amp wiring kit be enough? Also when you wire the rear speakers in series, doesn't that change the resistance? Thanks again... |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13416 Registered: Dec-03 | The PDX-5 would be a perfect solution. I just didn't think you had $650 in the budget for the amplifier 4AWG is sufficient for up to 125A of current. Your stock alternator can't supply that much current, so yes 4AWG is sufficient. http://www.glasswolf.net/papers/charging.html two 4 ohm drivers in series will present an 8 ohm load. a bridged pair of channels on an amplifier will "see" half the actual load, so the amp's rear channels will deliver the right amoount of power to the rear speakers. The point of bridging the rear channels and running them together in series is to get a mono signal instead of stereo. This helps to prevent the rear speakers from causing a "floating" effect that destroys the front stage stereo separation, and by doing so, draws your sound stage to the rear of the car, and ruins any hopes of good imaging. Using a bandpass filter on the rear speakers also squelches the treble to again prevent drawing the soundstage too far rearward, and eliminates bass to prevent the mids from bottoming out at high output. |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13417 Registered: Dec-03 | you really just want the rear fill speakers to "warm" the vocals a bit. Not be clearly audible. Ideally, the music should sound like it's coming from a stage in front of you, and slightly above you with clear stereo separation allowing you to close your eyes and be able to pick out the position of each instrument or vocalist. That's what soundstage and imaging are. |
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New member Username: WandaddyPost Number: 5 Registered: May-10 | Wow you are really knowledgeable about all this stuff. I think I may just go with the one Alpine PDX-5, even though I will have to save up a little longer. I have found some on Ebay new for less than $400, so they are not too bad on price. I guess I just prefer simplicity, so I like the idea of having one amp to power everything. Plus I really have no means available here to fabricate an amp rack or anything custom as far as mounting a couple of amps. So I guess I have 2 more questions concerning the PDX-5 (if you aren't tired of helping me already): Would the "Big 3" upgrade still be absolutely necessary? I know doing it would benefit my charging system and everything, but could I run that amplifier and maybe do the "Big 3" upgrade later without any problems? Is 300 watts RMS enough to push a Boston G3? From what I have read on this forum, it seems to me that under-powering a sub can be as bad as overpowering it. I know turning up the gain high is not a good idea because the amplifier can reach it's saturation point and you would lose sound quality among other things. So I am wondering if 300 watts RMS is enough. I don't need my system to be extremely loud, I just want a nice balanced sound that sounds clean and tight. Also would a DVC sub be better than a single-coil in this case? Thanks again, you have been very helpful in answering my questions. By the way, I checked out your homepage and I must say, I love your Charger. I am a big muscle car fan too. I've got a 1972 Mach 1 Mustang back home that I can't wait to drive when I move back to the USA in 2 1/2 years. |
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Silver Member Username: CwruckPost Number: 118 Registered: Feb-10 | glasswolf if you use a run of 15 ft of 4 ga wire thats only around 90 amps that can run through it, but if your using a shorter run of 6 ft or less then you will be able to draw 125 amps through your wire. but no the big 3 is not absolutely necessary, i think he just recommended that because you had problems with it before and it should help it from happening again, though i do not know the reason it went out on you in the first place. i honestly think you are throwing away some money buying a 5 channel amp, if you just buy a regular class a/b alpine 4 channel you will be fine and get the mrp-500 for the sub, you wont notice a difference in sq buying those amps but you will have more power for the sub so if you do the mrp-500 u will want either a svc 2 ohm sub or if they dont make that buy it in dvc 4 ohm so you can wire it in parallel (just connect the pos to the pos and the neg to the neg) and you will be at 2 ohms to get the most from the amp. the only thing about underpowering a sub is that it is easier to clip the amp which will cause distortion and blow the sub. its always nice to have a little more power than you need you can always buy used and you can get some better deals than buying new of course but lately theres been many people just selling stuff that doesnt work because they are broke and trying to get some money to pay their bills, it has happened to me even from people that have 100% feedback on ebay, so i just spend the little bit extra to buy new. it sounds like your going to have a nice sounding system, and im sure you will be surprised at how loud 400-500 watts of bass can be |
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Platinum Member Username: GlasswolfLexington, SC USA Post Number: 13434 Registered: Dec-03 | well you can do the big 3 whenever you like, or not do it at all. That's your call. It will help quite a bit with current demands though, and you will be taxing that stock charging system already. That's all up to you. I'm just giving you some guidelines for what should be done. There's nothing wrong with doing things in steps, too. 300W is a little weak for a sub, but that's the big issue with these 3 and 5 channel amplifiers. They rarely supplu more than 300W for the sub channel, which means if you want to run more than about a signle 10" ported sub, you''re going to need a separate amp to do it. You should be OK for a while, but eventually you will want more, I'm ppretty sure of that. The PDX5 is a good amp for installing a "better than factory" setup but it's probably not going to cut it if you really want a loud system. With 300W, I would go with a ported of 4th order bandpass box to optimize the efficiency of the box itself for more output with a fixed amount of power. You can't technically underpower a sub. What you can do is have too litle power and as such, ahve low volume output from the sub. What this causes some people to do is try to compendate by turning up the gain on the amp to "get more from the sub" and as a result, cause the amp to clip, and thereby burn up the coils on the sub. Keep the gain set right and at worst, you just won't get as much bass as you may want. No damage caused though. The number of voice coils only works for versatility. What you'll want for a single sub setup is either dual 4 ohm coils (wired in parallel for 2 ohm load) or a single 2 ohm coil (whatever Boston offers that sub in) to get a 2 ohm load at the amplifier for the most power from it. Mach 1s are nice. Japan is a great tour though. Enjoy it. I'm well aware of the length to current ratio for DC voltage in power line, which was why I added the link to the chart on the page regarding charging systems. However for the "big 3" wiring, 4AWG is going to be more than enough, and again, with his stock alternator, he isn't going to be able to supply enough current to cause appreciable voltage drop across 4AWG wire anyway, even to the PDX-5. Remember that even though that amp is rated for 75Wx4ch and 300Wx1ch, he's still using a class T (tripath) amp for all 5 channels which means about an 80-86% efficiency, with a reactive inductive load presented to the amp, from a dynamic input source, combined with factors like impedance rise from teh sub enclosure he's never going to see close to the full output of that amplifier if the gains are set properly. Additionally, factor in the power to volume ratio and at moderate volume levels, he'll see a mere fraction of the amp's available power at a sustained current draw. He's not going to have any issues at all with 4AWG even for power and ground runs to the amplifier. The car is 14 years old, so it's possible his alternator just died from age, which does happen. In any event, with the added current draw of an audio system, the big 3 upgrade isn't a bad idea. Remember the car chassis, battery, alternator and voltage regulator, and the audio system is all a part of one big circuit, and like pipes supplying water through the plumbing in a home, the amount of water available from a faucet is going to rely on the narrowest pipe between the supply and the tap. If he chokes current flow at the battery and alternator, all the fat wire in the world won't help at the amplifier. That's all I was trying to convey. between the MRP500 and the PDX5 he'd probably gain 2 to 3dB from teh sub alone. If he gets an alpine 4-channel amp that puts out the same 75x4 he'll have a bit more current draw but the output will be overall louder, and have more headroom as well. good point on the used amps. always a lot of them on ebay. I'd be wary of craigslist though unless you can test the amp before taking it home. |