Bumpin Balt

I have an Alpine MRD-M500 amp that is able to handle a 2 ohm load without getting overly warm. I'm wondering if I can use it to push 2 JL Audio 8w7 subs which are rated at 3 ohms each? I'm thinking that if I drop the input signal on my line driver I should be fine, but I want to find out for sure before I buy the subs.

Pully Police

Yes - if you wire them in series (but I bet you knew that already)

You *could* drop the input signal on your line driver - but that would just be a bandaid solution. You should either:

1. Get an amp that can handle a 1 - 1.5 ohm load.
2. Connect the speakers in series.
3. Get 4ohm subs that you can wire in parallel. No use patchworking it.

Bumpin Balt

It is a class D amplifier which is extremely efficient. Can't most class D amps handle a 1 ohm load? My guess is that Alpine only rates their amps down to 2 ohms just to be on the safe side and minimize warranty claims. A 1.5 ohm load is probably safe on a 2 ohm rated amp. A 1 ohm load would probably be pushing my luck. Does anyone else agree with my assumption?

Pully Police

Yes - to a degree.

A class D amp is very efficient - and it proabaly could handle the 1.5 ohm load - but the life of the amp will be shorter.

JRANGER

I would look in your manual. If it is 1 ohm stable it is usually mentioned in the guide. I will try to look this up. However, if you run it 1ohm and its not stable you could blow your amp.

Just checked into it and yes your amp is 1ohm stable so 1.5 ohms shouldnt be a problem

HackAbuse

I've ran amps at half their rated impedance without problems before

Bumpin Balt

Do you have the link to where you found the info saying it is 1 ohm stable?

JRANGER

cant find it now but scanning the forums they said most alpines can go down to .25ohm but almsot all mono b locks are atleast 1ohm stable

sorry i did a google search on it. Also you should check out ym fiberglass build pics and see the progress

https://www.cobaltss.net/forums/electronics-audio-video-49/jranger-starts-his-fiberglass-sub-box-69020/

EmperorJJ1

iTrader: (5)

ya lol put an alpine at a .25 ohm load daily and see what happens....

Bumpin Balt

Me thinks that would be pushing my luck! LOL. Seriously though, do you think my amp can handle a 1.5 ohm load and still produce clean sound?

JRANGER

I dont see any reason why It couldnt..and yea I didnt say i would do .25 just something I read...

DoMiStIc_RuSh_06

iTrader: (1)

Dont do it, you will over power the amp, where alpine amps are so efficient, they will shut down, due to overheating. Trust me, I had 2 mrd 1000 amps and they did this, as well as my 2 mrd 605's that I had. Find an amp thats 1 ohm stable (like rockford fosgate), Chances are that a 1 ohm stable amp wont be very efficient.

EmperorJJ1

iTrader: (5)

honestly i personaly have done worse on my fosgate mids amp but i normally wouldnt recommend it (and yes it got damn hot as hell) and .35 on my 1ohm sub amp for competition as well. If you have access to a meter test the actual ohm rating on each sub and see what it shows. Hopefully it will be slightly higher then 3 ohm (as alot of mainstream subs are) and if so then i wouldnt see a problem doing it in a ported box (ported boxes tend to have a but more impendance rise especially with a large port)

Ive delt with that amp and honestly its a really nice one and i belive it can handle a bit less then 2 ohms.

fyi efficency is the reason we are having this conversation. The power an amp gets that it cant convert to ac voltage for the sub turns into heat. Which is why a class a/b amp makes so much more heat and thermals quicker then a more efficent class D. If you amp is more efficient then going lower then the rated ohm level would effect the amp slightly less

DoMiStIc_RuSh_06

iTrader: (1)

You really know your stuff dont you. I dont know a whole lot about stereos, just the basics and what i'm told. Thats it. You keep making me look like an ass. I would appreciate if you didn't do that. I'm sorry that I dont know alot about stereos. Once again, i only know what I was told!! Thats why I dont have a stereo anymore, because most people down here where I live, dont have a clue about this stuff.

JRANGER

Domistic I hate to be an ass but if you don'tknow why input your advice. Obviously Emperor is just trying to make sure the correct information is provided so the best result can be achieved. Just as I am, I looked up information on his amp before I made any comments on this subject.

EmperorJJ1

iTrader: (5)

lol i could make you look like an ass since techniclly the info u looked up told u its a 1 ohm amp when its really a 2 ohm but i try not to do that

Bumpin Balt

I would probably put the 2 JL 8w7's in a double slot ported box. I need to upgrade my alternator and run 0 gauge wire from my alt to my battery before I even consider doing this though. If I ran this set up with my electrical system as is, the amp would probably shut down because it wouldn't be getting enough current. I may just try a single 8w7 first to see if it gives me enough output to satisfy me.

EmperorJJ1

iTrader: (5)

not if your running that 500w amp. My mids amp never turned off due to low current (800w) and all i upgraded was the battery itself and the ground

Bumpin Balt

I'm also running an MRD-M300 for my 8" Mid bass speakers and an MRV-F340 4-channel for a grand total of 2000watts max/1100-1200watts RMS. My 4-channel shuts off if I try to play my system while my car is parked and running.

Redberet

Emp is correct, it will run but it will make some serious heat.

That will also shorten the life of the Mosfets because you are baking them. They won't heat up until you really raise the volume, so if you drop the gain significantly or drop the line driver amplitude you'll be fine.

Also you can run those without upgrading your alt or the wiring. I run 1200 RMS through two batteries and a 1 Farad cap and its fine. I suggest you add a second battery though if your getting past 500RMS. The most I was able to draw from the battery while running was about 75Amps, adding the second batt allowed 120amps.

Not enough power or high resistance in the power wire. If its a new system then you need another battery, if its an old system I've seen it before where the power wires corrode and the system shuts off.

JRANGER

got a wiring diagram for a second battery? Will that work without upgrading the alt without killing the alt?

DoMiStIc_RuSh_06

iTrader: (1)

FYI, I didnt look up any information, I owned 2 of these amps, tried hooking them up as 1 ohm, but it kept cutting out on me, the tech that installed the stereo for me told me that these amps weren't 1 ohm stable.

Emperor-> I didnt not say that it was a 1 ohm amp, as I correctly remember, I said that its a 2ohm amp, and that it wont handle 1 ohm!!!

JRANGER-> All I was doing was giving you the info that I was firmilliar with, thats the reason that you started this thread(obviously). I was just trying to help you out with what I knew, so why would you be an ass to me. I'm not ranting or anything, I just dont like being criticized for passing on information that I was told!!

JRANGER

um...i didnt start this thread

Oh and last I checked you didnt his amp. You had a different model in the same series

DoMiStIc_RuSh_06

iTrader: (1)

My bad, I had the It was 2 mrd-605 amps, and before that I had an mrd-1000.

EmperorJJ1

iTrader: (5)

ya i wasnt talking to u in that post DR 06

that means somthing is wrong. An amp doesnt shut off until say 10v and if your getting that low then something is off. Test the voltage at your batt make sure its at least 12.5 (any lower is a weak or gone battery) test voltage at the battery terminals (cobalt terminals are built very shitty and tend to be very loose giving u a bad connection) Test the ohm difference between the batt ground any your amp ground at the amp ground location (if u didnt ground to the bat) and at the amp. if the resistance is high then u need to fix it