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#1 (permalink) Old 04-20-2005, 10:41 PM
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i've recently added a mono amp for my subs and this really doesn't make sense.

i have 2 12" W3v2 subs from JL - 300W rms 4ohm each. i took my multimeter to the pos . neg terminals on the sub enclosure and they -both- ohm out at 4.

the JL 500/5 amp they were running on is 250W max on a single channel.

i bought an Alpine MRD-M605 rated 600W rms @ 2ohm and 400W rms @ 4ohm.

i set everything up last night and the new amp can't even get close to the original power / sound of the 500/5. i don't understand it at all. i even jacked up the amp output signal to +16db and the head unit to +4 .. it sounds like shit but it was finally back as loud as before. =0

someone have ANY idea whats wrong here?

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#2 (permalink) Old 04-20-2005, 11:17 PM
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Quote:
Originally posted by EcianIce@Apr 20 2005, 08:41 PM
i've recently added a mono amp for my subs and this really doesn't make sense.

i have 2 12" W3v2 subs from JL - 300W rms 4ohm each. i took my multimeter to the pos . neg terminals on the sub enclosure and they -both- ohm out at 4.

the JL 500/5 amp they were running on is 250W max on a single channel.

i bought an Alpine MRD-M605 rated 600W rms @ 2ohm and 400W rms @ 4ohm.

i set everything up last night and the new amp can't even get close to the original power / sound of the 500/5. i don't understand it at all. i even jacked up the amp output signal to +16db and the head unit to +4 .. it sounds like shit but it was finally back as loud as before. =0

someone have ANY idea whats wrong here?
[snapback]335779[/snapback]
You have the right subs (dual 4 ohm). The gains between the 2 amps are two different animals. They use the rca's voltage differently, so 2 o'clock on each amp will be a different setting. A good rule of thumb: turn the sub gain off, turn the headunit to a volume where the mids are just reaching the point of distortion, back it off just a bit, turn the sub gain up until the subs just start to distort and back it off a bit, and as long as you dont go over that volume when listening, you shouldnt have any problems.

Do you have them wired in parallel? That is the way the should be wired for that amp, to do full power.



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#3 (permalink) Old 04-20-2005, 11:19 PM
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alpines website said 400w at 12v (most ratings at 14.4 are good, but the car usually doesnt give a constant 14.4 volts)



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#4 (permalink) Old 04-20-2005, 11:28 PM
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the ohms for both of the subs together are 4ohm, so yea in parallel.

i understand what your saying about setting it up so they sound good together, but the problem is that i HAVE to jack the gains way up before i can even begin to feel the bass comming through. the 500/5 had no problems shaking my seat with (i just measured this) 70W rms to BOTH subs.

the 400W amp must be broken. i don't know. it's in the wiring or something.

oh yea. according to the alpine amp i get about 13.2v - 13.8v while the subs are hitting. 14v at idle with no music on.

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#5 (permalink) Old 04-21-2005, 06:29 AM
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Cancel my first reply. Thats what I get for posting after my bedtime. You cant get the dual 4 ohm speakers to make a 2 ohm load at the amplifier. Since its a mono amp, the speaker leads (if it has 2, I cant find a good pic of the speaker hookups on the net) are wired in parallel at the amplifier. If you are getting 4 ohms at the amp, that is why you cant get much power out of it, your jl amp does more power at 4 ohms.

A dual 2 ohm would get more power. You can wire the voice coils at each speaker in series to get a 4 ohm load, then wire each speaker in parallel with each other getting a 2 ohm load to present the amp with, thus getting the 400w RMS. SOME Alpine amps are 1 ohm stable, even though the spec shet says no. I'm not sure if I would wire it in this way or not. You would get more power out of it, but you may have a chance of tearing it up (actually "I" would but I can get mine warrantied, and I dont push my system to its limits like I used to :P ). You will have to rewire your subs in the box to get this.

If its under warranty, talk to the people you bought it from, and ask them about the 1 ohm load, see if they've had any success doing it. If so, and they will warranty it, I'd say go for it.



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#6 (permalink) Old 04-21-2005, 07:18 AM
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but if im putting 4ohms from the subs, to the amp. i -should- be getting 400rms. if i knocked it down to 2ohms it'd be 600rms. so according to what you said it should work exactly how it's setup right now. =0

i think i'll run it by a sound shop later today.

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#7 (permalink) Old 04-21-2005, 06:27 PM
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Quote:
Originally posted by EcianIce@Apr 21 2005, 05:18 AM
but if im putting 4ohms from the subs, to the amp. i -should- be getting 400rms. if i knocked it down to 2ohms it'd be 600rms. so according to what you said it should work exactly how it's setup right now. =0

i think i'll run it by a sound shop later today.
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Alpines website says 250w on a 4 ohm load, which is divided between the 2 subs, 125w ea. The 2 ohm rating is 400w, or 200w ea.

I haven't messed with this amp in particular very much at all, but I've ran the 4 channels at 1 ohm and it performed pretty good and didn't get hot.



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#8 (permalink) Old 04-22-2005, 09:55 PM
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so i went to the shop today. this is so messed up.

at the connectors in for the enclosure im getting 8ohms. =0

the 250W channel is pushing through 8ohms like nothing. amazing. JL ftw.

but yea .. we took each sub out and were going to make sure it was in parellel and we found out that i have a blown voice coil on 1 and for some reason another coil ohms out at 60 or so. but they still work fine.

the guys at the shop had no idea what to think of it and all i got was a reccomendation that i start all over for subs and buy new.

W7's hehe.

guy: "W7's .. thoes are like the bad boy JL's aren't they?"
me: "yea, their highest rated sub"
guy: "if you go with that i'd reccomend only 1 12" in a ported box, otherwise if it's sealed that sub will blow the sides off it."

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#9 (permalink) Old 04-23-2005, 06:27 AM
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Quote:
Originally posted by EcianIce@Apr 22 2005, 07:55 PM
so i went to the shop today. this is so messed up.

at the connectors in for the enclosure im getting 8ohms. =0

the 250W channel is pushing through 8ohms like nothing. amazing. JL ftw.

but yea .. we took each sub out and were going to make sure it was in parellel and we found out that i have a blown voice coil on 1 and for some reason another coil ohms out at 60 or so. but they still work fine.

the guys at the shop had no idea what to think of it and all i got was a reccomendation that i start all over for subs and buy new.

W7's hehe.

guy: "W7's .. thoes are like the bad boy JL's aren't they?"
me: "yea, their highest rated sub"
guy: "if you go with that i'd reccomend only 1 12" in a ported box, otherwise if it's sealed that sub will blow the sides off it."
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Sorry to hear about your subs, thats a bummer.

Yeah the 8 ohms wouldnt give you much power at all. I thought that what you were describing was weird and you sound like you know whats going on. It should have done more power than that. I guess I need to start with the basics next time, instead of assuming the speaker is fine ghead :P . The W7 is a good speaker...if you have 800-1000w RMS to play around with, other than that, your speakers are a better match for your amp. Or the Alpine S-series would work well too, if your looking at new subs.

lol if that sub will blow the sides off the box, they need a new box builder. I can take a sheet of 1/2" mdf and make it perform better than most peoples 3/4" boxes. It's all in the bracing. Make the box where it doesnt move/flex when the bass hits. If the box moves, your wasting precious energy by flexing the box sides instead of using it to achieve more sound. Its minimal, but it does make a difference.

A ported box will typically give you a stronger low end, a sealed usually isnt as loud, but a smoother sound through all the bass frequency range.

Ive got 2 11" Focals in a sort of a bandpass I constructed, with all the energy being forced thru the ski hole in my 90 525i. It works well, and if I get tired if the bass I just fold the arm rest up and it knocks the sound down about 10db. I didnt want any trunk rattle, so I forced all the sound through there, it works really well.



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-If we ever forget that we are One Nation Under God, then we will be a nation gone under...Ronald Reagan
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