Newbie Amp Questions

[badboyeee]

Okay everyone, I got my head unit, I got my door speakers, and recently just got my sub. Now I need the final piece to my audio system, the AMP! I've tried to browse as much as I could through older posts of this forum, and I've gained alot of knowledge. But I still some have questions...

Does gain control the amount of power output? (For example a 50W rms channel will put out 25W rms when the gain is set to half way?)

I know not to run RCA's and the power wire together. Is it okay to run everything else together? What about Speaker wire along power wire or RCA's?

For the P5, is it better to put the amp under the driver or passenger seat? (I'm guessing the driver's side is more convenient since the battery is on that side...)

What kind of crossover settings should I look for?

Is the bass boost option something I should opt for to add bass to my sub?

What size speaker wire should I use for the sub?
(I researched that the stock speaker wires should be able to handle 40-60 rms watts fine. So I will splice into the head unit's wiring harness for that.)

I've been looking at the Alpine line of 4/5 channel amps the most, since I've heard good things about them. However they are pretty expensive when bought brand new (except for the MRP-F240). I almost got the MRV-F340 used on Ebay, but lost the last 30 seconds of the auction battle. I was wondering what other brands/models I should look into. Also if there are discontinued but recent models I should look for such as the Alpine MRP-F320. The MRP-F320 or MRV-F340 would probably be perfect for my setup. I was thinking the MRP-F240 @ 40x4/100x2 might not be powerful enough (for my sub), unless Alpine usually understates their power ratings?? I really do want clean good quality sound and power.

Here are my speakers/sub:
Front: Alpine Type S 5x7's w/ 40w RMS
Back: Pioneer 6.5's w/ 40w RMS (I'm just using these as rear fill, so not really important to amp them, although I would like to if I can find a good deal on a 5 channel amp)
Sub: JL 10W0-4 with Sealed Enclosure w/ 125w RMS


ps.. i know i have asked alot of questions, hope you guys aren't annoyed yet! i really do appreciate the responses i've got so far...

 

[1sty]

Does gain control the amount of power output? (For example a 50W rms channel will put out 25W rms when the gain is set to half way?)

Yes and no.
A gain know adjust gain ratio. An amp essential just increases the voltage of the audio singal. If you send it a 2 volt singal from the head unit it will increase say 20:1 or to 40 volts. However amps have a limit to how much voltage they can produce so if the amp can only produce a maximum of 50 volts and you give it 3 volts as an input, what happens? This is when the gain comes into play. Without it the amp would aaply the same ratio fo 20:1 to the audio signal and attempt to make 60 volts that it can't do in our little example here. So the singal becomes very distorted called clipping. The gain allows you to tell the amp what voltage form the head unit it will get. So all the way to the right and this fictional amp applied a 20:1 gain ratio to the input signal. For a 3 volt signal you want to set it to about 16:1.

I know not to run RCA's and the power wire together. Is it okay to run everything else together? What about Speaker wire along power wire or RCA's?

It doesn't matter, I tend to run them with the RCA's or by themselves.

For the P5, is it better to put the amp under the driver or passenger seat? (I'm guessing the driver's side is more convenient since the battery is on that side...)

Be very cautious of the fuel lines under the drivers seat. It will take a long screw to hit them though. You can always just velco a peice of wood to the floor under the carpet and then fasten the amp to the board, through the carpet.

What kind of crossover settings should I look for?

For simple systems, 60-200 usualy does the trick but I like to have between 50-400 for amps that are doing more specilty work, or that will.

Is the bass boost option something I should opt for to add bass to my sub?

NO! It goes back to the gain. All the bass boost does is rasie the voltage of the audio signal for a small area of sound before its amped. So if you have a 2 volt signal, with are fictional amp again, and you bass boost to 3 volts where do you set the gain. Set it to the 16:1 and only the base boosted signal is at full power, set it to 20:1 and the amp is just clipping the bass boosted sounds.

What size speaker wire should I use for the sub?
(I researched that the stock speaker wires should be able to handle 40-60 rms watts fine. So I will splice into the head unit's wiring harness for that.)

For a single W0, 12 is more then enough, even 14 gauge would be ok. The stock wires will handle 40-60 watts rms without issue or perceivable loss.

I've been looking at the Alpine line of 4/5 channel amps the most, since I've heard good things about them. However they are pretty expensive when bought brand new (except for the MRP-F240). I almost got the MRV-F340 used on Ebay, but lost the last 30 seconds of the auction battle. I was wondering what other brands/models I should look into. Also if there are discontinued but recent models I should look for such as the Alpine MRP-F320. The MRP-F320 or MRV-F340 would probably be perfect for my setup. I was thinking the MRP-F240 @ 40x4/100x2 might not be powerful enough (for my sub), unless Alpine usually understates their power ratings?? I really do want clean good quality sound and power.

The alpine MRP-F356 was a great little 5 channel. If yuo can find one you should consider it. It went for about $270 new. Sir Nuke uses one and loves it. Theres a shop in town that still has new ones if your interested but they want basicly full price for it. A 4 channel will do the job though, just don't amp the rear speakers. Also even with a 5 channel you can always just bridge it to 3 channels and just power the front speakers and sibs. Eclipse has some good 4 and 5 channels aswell and JL has the "e" series 6 channel.

 

[badboyeee]

Yes and no.
A gain know adjust gain ratio. An amp essential just increases the voltage of the audio singal. If you send it a 2 volt singal from the head unit it will increase say 20:1 or to 40 volts. However amps have a limit to how much voltage they can produce so if the amp can only produce a maximum of 50 volts and you give it 3 volts as an input, what happens? This is when the gain comes into play. Without it the amp would aaply the same ratio fo 20:1 to the audio signal and attempt to make 60 volts that it can't do in our little example here. So the singal becomes very distorted called clipping. The gain allows you to tell the amp what voltage form the head unit it will get. So all the way to the right and this fictional amp applied a 20:1 gain ratio to the input signal. For a 3 volt signal you want to set it to about 16:1.

Hrmmm.. I'm not grasping this concept 100%.. Does volts = watts ?? Well lets just say if I were to get a MTX Thunder404 4channel amp that does 50x4 / 200x2 ..... since 200w would be too much for my 10w0 sub, I would able to adjust the gain lower, hopefully decreasing the volts to make 125w??? My head unit gives out 2v signal.

It doesn't matter, I tend to run them with the RCA's or by themselves.

Should I avoid the speaker wire from getting close to the power wire?

Be very cautious of the fuel lines under the drivers seat. It will take a long screw to hit them though. You can always just velco a peice of wood to the floor under the carpet and then fasten the amp to the board, through the carpet.

That sounds like a good idea. Do you happen to know what kind of wood I should look for and where to get it? Home Depot? 1/2 thick of wood would be fine?

For simple systems, 60-200 usualy does the trick but I like to have between 50-400 for amps that are doing more specilty work, or that will.

My Alpine door speakers has a frequency response of 35-30k... So does that mean I should look for a HP filter at 35?

The alpine MRP-F356 was a great little 5 channel. If yuo can find one you should consider it. It went for about $270 new. Sir Nuke uses one and loves it. Theres a shop in town that still has new ones if your interested but they want basicly full price for it. A 4 channel will do the job though, just don't amp the rear speakers. Also even with a 5 channel
you can always just bridge it to 3 channels and just power the front speakers and sibs. Eclipse has some good 4 and 5 channels aswell and JL has the "e" series 6 channel.

I thought Sir Nuke has the MRP-F320? Well I looked for both that one and the MRP-F356, but I can't find them new or used online.
I just looked into the Eclipse's and JL's as well, but they are too pricey for me. I found other brands such as MTX, Pioneer, Phoenix Gold, and Clarion that fit my budget. How are those brands?

 

[Poseur]

Hrmmm.. I'm not grasping this concept 100%.. Does volts = watts ?? Well lets just say if I were to get a MTX Thunder404 4channel amp that does 50x4 / 200x2 ..... since 200w would be too much for my 10w0 sub, I would able to adjust the gain lower, hopefully decreasing the volts to make 125w??? My head unit gives out 2v signal.

YOu can use the gain to accomplish this, yes. also, you might not necessarily have to backoff your power all THAT much, Just be careful with your gains, and if you hear any topping or bottoming out, back them off some more. One thing in general, don't pay as much attention to specs, yes they give you a generla idea of things, but they aren't everything.

Should I avoid the speaker wire from getting close to the power wire?

not as vital as keeping it away from your RCAs, but still best avoided.

That sounds like a good idea. Do you happen to know what kind of wood I should look for and where to get it? Home Depot? 1/2 thick of wood would be fine?

it really doesn't matter what kinda wood you use, just get anything, you might wanna keep it fairly thin, but you're going to be compressing some insulation under your carpet as well, so space isn't a huge concern. 3/4" would be fine. I'd just use scrap form whatever's around. Are you building a box? One thing to be careful of is your under-seat vents for the heater.. I've managed to simply run them over the top of my amps without a problem, but they are kinda an annoyance. SOMe ppl cut them, but Why defeat the purpose of having them, and shoot heat right at your amp.

My Alpine door speakers has a frequency response of 35-30k... So does that mean I should look for a HP filter at 35?

again, a matter of toomuch attn to specs. if you'll notice every manufacturer has a different listing for freq range. Realistically, 80hzish is the range you'll wanna be in.

I thought Sir Nuke has the MRP-F320? Well I looked for both that one and the MRP-F356, but I can't find them new or used online. I just looked into the Eclipse's and JL's as well, but they are too pricey for me. I found other brands such as MTX, Pioneer, Phoenix Gold, and Clarion that fit my budget. How are those brands?

MTX, yes, perhaps one of the better choices. old PG yes, but the new stuff's had some nasty things said aboutit including actual fires. Clarion, some of their stuff's reportedly made by some much higher end amp companies. Honestly, I'd realyl look into something youknow and trust. I got a sweet deal on some off-brand amps taht's been haunting me for wuite awhile now. Sofar I've sent them both back 3times. Fixed free mindyou, but it costs me shipping and a couple weeks each time.

 

[FoxPro5]

Well, first of all, a lot of good questions here. I have both my amps underneath my seats and have not had a prob yet (knock on wood). I put some velcro on the bottom of them to keep them from sliding around. However you do run the risk of someone stealn' your s*** pretty easily. I usually have the airflow set to the floor and the knob at about 1 out of 4 when running my system hard b/c my rockford amp tends to get hot.(argh)

I can personally vouch for Alpine and Eclipse amps b/c I have used them both. In fact, if you bid on a MRV-F340 in the past couple of weeks it may have been mine. lol. It sold for $207.50, if it was the same one. I had it brigged to my fronts at 110 watts rms and it was pretty exceptional. Then I swiched to my Eclipse that i previously had on my sub, and, gawd damn it was like night and day. You can not go wrong with the quality and sound production per dollar than Eclipse! If i were you I check your local car audio shops or on ebay to see if you can get your hands on one...you won't be disappointed!!

Forget about bass boost. You probably want a HU with sub level control if you don't already have it.

Lastly, you have already commited your time and money into the car audio experience so my advice would be to learn from the dudes on this forum because we have all been there before. Nearly everyone here will almost always tell you to spend more money for more power. Power, as you will learn, is grreeeeat. Having said that, you really have to decide on a budget and try to work within it.

Good luck and don't hesitate to ask more questions. Like i said there are a lot of smart guys here that can really help you make better decisions...i know they really helped me (tear rolls down cheek) as Cartman says...I love you guyyyyyz

 

[1sty]

Hrmmm.. I'm not grasping this concept 100%.. Does volts = watts ?? Well lets just say if I were to get a MTX Thunder404 4channel amp that does 50x4 / 200x2 ..... since 200w would be too much for my 10w0 sub, I would able to adjust the gain lower, hopefully decreasing the volts to make 125w??? My head unit gives out 2v signal.

Volts x Amps = Watts
So if the voltage goes up, so does the wattage.
Yes you can lower the wattage. There is a point in the gain ratio knob that will allow the amp to create 200 watts with out clipping. As you go lower then that point you will reduce the amps possible output. Something to mention is that the W0 is MORE then capable of taking 200 watts rms. JL DRASTICLY under rates their subs.

Should I avoid the speaker wire from getting close to the power wire?

Don't worry about it too much. To be save, keep the speaker wire near the RCA's side of the car.

That sounds like a good idea. Do you happen to know what kind of wood I should look for and where to get it? Home Depot? 1/2 thick of wood would be fine?
My Alpine door speakers has a frequency response of 35-30k... So does that mean I should look for a HP filter at 35?

Plywood, it will grab screws better then MDF which strips itself instantly.

No, you won't need any crossover lower then 50 hz. I have yet to EVER see someone use a crossover point lower then 50 HZ. With your setup you'll be around 70 hz.

I thought Sir Nuke has the MRP-F320? Well I looked for both that one and the MRP-F356, but I can't find them new or used online.
I just looked into the Eclipse's and JL's as well, but they are too pricey for me. I found other brands such as MTX, Pioneer, Phoenix Gold, and Clarion that fit my budget. How are those brands?

Eclipse EA3422. Its a great little 4 channel amp. $250 retail and has totaly adjustable crossovers.

 

[chuyler1]

I for one am not an advocater of more power. The most important thing is to match the power handling of your speakers and subwoofers with the power output of your amplifiers. Sometimes its good to have a little overhead on your amp but you certainly don't need to send 1500 watts to a subwoofer to get decent SQ. The bottom line is that you can get good SQ with 50 watts or 200 watts (150 or 1500 for subs). It all depends on your musical preferences and listening habits (how loud you listen, whether you drive with the windows open, etc). The second most important thing is setting the crossovers correctly. There is plenty of info about crossovers on this forum and the net so I won't go into details, but if you match your amps to your speakers, set the gains properly, and configure the crossovers you are well on your way to great SQ.

 

[badboyeee]

Thanks everyone for the wonderful replies. I understand fully now what the gain setting does. I think I will use velcro method to keep the amp down.

But anyways, I finally got an amp from Ebay! It's the 5ch Alpine MRP-F320, just like Sir Nuke's. I had no one to battle with this time, the auction ended at 1am PST, so I think I got a pretty good deal. Hopefully it's shipping soon.

Well the last thing that I need to get now is the amp installation kit. Is this something that I shouldn't go cheap on? Does brands make a difference? Or is it just the RCA's that need to be high quality? I was just gonna get the one at KnuKoncepts but their kits come with a blue power wire. I'm gonna go picky, and would like a red power wire instead to match my strutbar . I've been browsing around ebay for some. Would it be cheaper if I got cables seperately for goodguys or circuit city or soemthing?

How should I run the power wire inside the engine? If someone has a pic of how they did it, that would be helpful.

 

[1sty]

For an 8 gauge kit even Monster cable's without RCA and at full retial is under $30. The reason I use monster is becuase they are the only ones that use sealed crimp connections. Other then that it really doesn't matter.

I am pretty sure Nuke has a different amplifier. I'll have to look it up later to know for sure. I thought his was the MRP-F356 or something to that effect. I should know this as I suggested it.

 

[FoxPro5]

Thanks everyone for the wonderful replies. I understand fully now what the gain setting does. I think I will use velcro method to keep the amp down.

But anyways, I finally got an amp from Ebay! It's the 5ch Alpine MRP-F320, just like Sir Nuke's. I had no one to battle with this time, the auction ended at 1am PST, so I think I got a pretty good deal. Hopefully it's shipping soon.

Well the last thing that I need to get now is the amp installation kit. Is this something that I shouldn't go cheap on? Does brands make a difference? Or is it just the RCA's that need to be high quality? I was just gonna get the one at KnuKoncepts but their kits come with a blue power wire. I'm gonna go picky, and would like a red power wire instead to match my strutbar . I've been browsing around ebay for some. Would it be cheaper if I got cables seperately for goodguys or circuit city or soemthing?

How should I run the power wire inside the engine? If someone has a pic of how they did it, that would be helpful.

Good choice on the amp...should give you a nice improvement over stock. Hell you always have room for expansion if you want (wink)

I bought the knu amp kit and it worked great and never have had an issue with noise and RCA's. You could also try ebay for the kits??? It might be cheaper to buy the stuff seperately (speaker wire, rca's, power, ground, terminals, fuses,etc) if you want red power wire, however it can be a pain in the ass to piece it all together. Try www.partsexpress.com for that stuff...they have pretty fast shipping. I have also bought wiring stuff from www.sounddomain.com. and www.darvex.com

You may want to get some extra power wire to make yourself some ground wires to upgrade from the crappy stock ones. Do a search on "The Big Three" for more info on this.

Personally i ran 4 gauge from the battery to the passenger side electical grommet that is located towards the bottom of the firewall. Kind of a b**** to do. I think most guys go through the drivers side one instead. In retrospect, it seems that the latter would be the easier way to do it, but it is too late for me to switch it now. I mounted the fuse holder on the side of the battery cover.

 

[chuyler1]

Here is a photo of where I went through the firewall on the driver's side. Just carefully cut a second hole in the rubber grommet and feed your cable through it. It will come out a few inches above the brake pedal I think.
http://www.msprotege.com/forum/attachment.php?attachmentid=19373

 

[Poseur]

www.knukonceptz.com at least net-companies can't screw up wire.

 

[badboyeee]

hey everyone, if someone can answer ASAP I ended up getting the knukonceptz kit. the fuse holder kinda has arrows on it, does it matter which way I point them towards? towards the battery or amp?

 

[badboyeee]

hey everyone, if someone can answer ASAP I ended up getting the knukonceptz kit. the fuse holder kinda has arrows on it, does it matter which way I point them towards? towards the battery or amp?

nm i know the answer now... thanks poseur!

 

[Poseur]

notta problem man, how'd it all turn out? you pleased with it? The one thing I forgot to mention is that with this type of thing, just take your time and do it right. If you're anything like me, you'll inevitably be tempted to pull a "well this should work for now" kind of thing here and there, which'll never get taken care of in reality.

Now think about how some shops'll toss an amp in in a halfhour... granted they generally know most of what they're doing to start with, save for car specifics, but howmuch do you trust their halfhour of work to last for the life of your car? Sorry I guess I'm just trying to justify the hours and days everything I've done inevitably takes me *L*...

 

[badboyeee]

notta problem man, how'd it all turn out? you pleased with it? The one thing I forgot to mention is that with this type of thing, just take your time and do it right. If you're anything like me, you'll inevitably be tempted to pull a "well this should work for now" kind of thing here and there, which'll never get taken care of in reality.

Now think about how some shops'll toss an amp in in a halfhour... granted they generally know most of what they're doing to start with, save for car specifics, but howmuch do you trust their halfhour of work to last for the life of your car? Sorry I guess I'm just trying to justify the hours and days everything I've done inevitably takes me *L*...

Hey Poseur, thanks again for the tips. Unfortunately, I didn't get to finish the installation. Well I actually did test the amp but there were problems. I didn't have time to do troubleshooting, it was already past midnight and I was suppose to leave to go on a road trip to Arizona with family using my car (oh boy were they getting antsy lol). So I just stopped and pulled the amp out. I did take long even though I was rushing. It took way longer than I expected (I spent probably 11 hours total). It took me awhile to get the power wire thru the firewall via the rubber grommet. There were jus little problems such as wrong butt connector sizes, the knukoncepts kit gave me wrong size ring terminals, etc. I had to take two trips to Radio Shack. Sent another person to go get my some velcro. Another annoying thing was I didn't have enough space to move around in the garage, my uncle's benz was parked next to me.

Well the problem with the installation was that only the left side speakers were working. When I balanced them to the right, the left side was playing. When I balanced them to the left, nothing was being played. It also sounded like it wasn't even amped even with the gain all the way up. But the problem could have been different things. My ground wasn't that great, I probably screwed up the speaker wiring or possibly labeled my RCA's wrong, or the amp is defective (I did buy it used from ebay, but i really hope thats not it). I thought I did all the wiring right, but by then I was super tired and getting irritated. The only thing positive that happened was that the amp turned on lol.

Well now for a couple questions:

What size speaker wiring should I use when I run the speaker wires back behind the head unit to connect into the wiring harness? My kit only came with size 12g, and its a huge difference between that speaker wire compared to the wires of the head unit wiring harness (20g?). So I was thinking that may be a problem, causing a bad connection between those two wires. So maybe I should change those speaker wires to 16g?

For the ground, theres the seat, the bolt, and the metal floor. Should I put the ring terminal between the bolt and the seat metal? or put it between the seat and the metal floor? And just sandpaper everything especially any paint off, right?

This was my very first time taking the car apart like that and of course wiring for an amp. I did take apart the door panels before, but that was this past tues and wed .

I shall do some troubleshooting soon, tomorrow hopefully if I have time.

 

[FoxPro5]

12g is fine to the harness. That is what I run and it may be overkill but it works good. You may want to solder the connections as they can come apart over time, at least mine did after a while.

I grounded both my amps to the rear bolt on the e-brake handle. Yes you want to sand it down bare to the chassis. Put the terminal between the seat and the metal floor.

Don't worry it took me several times to get it right. It is definately a project where you really have to figure it out on your own with trial and error.

Also, fyi, I had to drill out the ring terminals that Knu included in their kit because they are not big enough for a lot of bolts to fit through. You just need a big drill bit and like a bench vice to hold the terminal still.

Let us know how it goes and we will help with your questions.

 

[badboyeee]

I grounded both my amps to the rear bolt on the e-brake handle. Yes you want to sand it down bare to the chassis. Put the terminal between the seat and the metal floor.

Should I sand the black paint off too thats under the metal seat part?

Also, fyi, I had to drill out the ring terminals that Knu included in their kit because they are not big enough for a lot of bolts to fit through. You just need a big drill bit and like a bench vice to hold the terminal still.

What I actually did was cut a few strands to make the 8g wires fit in the 10g terminals they provided, is that a bad thing to do?


Also, along the sides under the panels, there are loomed wires. Is it possible to pull those things up and out? I tried but I didnt want to break it. I wanted to get more access to underneath the carpet so I can slide a piece of wood under it.

Any tips on taking apart the center console?? I know it would be hard to explain on here..

 

[Poseur]

Should I sand the black paint off too thats under the metal seat part?

The seat bracket shouldn't mattermuch. The part your'e really trying to ground to is your car itself. I actually took my ground from under the center console. underneath the rear mount of it, I'll link you as soon as I can find it...

What I actually did was cut a few strands to make the 8g wires fit in the 10g terminals they provided, is that a bad thing to do?

Nope, perfectly fine, just make sure you don't have extra strands hanging where they might touch other terminals on your amp. Tape them off or whatever.

Also, along the sides under the panels, there are loomed wires. Is it possible to pull those things up and out? I tried but I didnt want to break it. I wanted to get more access to underneath the carpet so I can slide a piece of wood under it.

YOu cna pull them up, yes. there's a "clip" on each that run front to back. if you get 2 flat screwdrivers, you can push in on them and then sorta pry them up. if that fails, just yank 'em, they won't snap back secure if you do that, but there'll still be a post there. You can always find replacement plug-things at schucks or Kragen or whatever lateron if you really want them.

Any tips on taking apart the center console?? I know it would be hard to explain on here..

6 screws for the center console. First you remove your cupholders/shifter surround by pulling up/back on the cupholders themselves. Then your e-brake surround should just pop out, nad you'll see 2 screws side by side that hold the console down. Next, upfront right about where your right knee is, there's a buttonhead thing, pop that off and it's covering a screw, there's a matchingone on the pass side. then the final one, you'll have to fold your seat down and it'll be right beside wher ethe seatback normally rests. Again, both sides. from there it should manouver out. Kind of tricky, and you will likely want to slide both seats all the way back. it'll pull up/back and actually (unplug) from a couple spots upfront under the dash.

 

[Poseur]

Also, that factory speaker wire is sufficient for upto 60w, if you still feel the need for more, check the link in my sig for "14g wire to doors" or whatever. you cna test your speaker connections by taking them and touching the +to + and- to- quickly of a 9v battery, you shoudl hear the corresponding speaker "pop" I think a AA or whatever you have'll work as well, just be careful not to leave them like this very long, jsut a quick "pop" is all you need to make sure. I'd be wary of that used ebay amp actually. We've all had our problems. the other way to test is switch your amp channels with the RCA's first, see if that does anything. ifnot, switch the connections at the amp. if the other side only plays now then it's likely a prob with the amp.

Actually, also here's a link that may help you as far as a layout for putting an amp under your seat. I guess I never posted up a pic of the bracket I grounded under. THere's a drawing someone did of it on page3 of that. But really inder your seatmount should be fine. just sand your paint down (I tend to prefer to just scrape it off with a flat screwdriver)
http://www.msprotege.com/vbb225/showthread.php?t=59376&page=1&highlight=ground+bracket