Howdy, I'm looking at adding a new sub, and I'll need more power from a new amp to push my system.

My HU pushes 20w/channel rms (Alpine 9847). My speakers are Polk Momo 6500 components in the doors and a JL 8w3v2 sub in a W Laurent enclosure. All the speakers have a 125w rms optimum power, and a 250w peak, so I'm looking for something that will push 150-200w continuous to the sub, and the components. Does that make sense?

Anyway, what are some good subs for the power I'm looking for? Fwiw, I'm looking for something I can mount to the back of my trunk to use a little space as possible.

 

I am assuming you are looking for an amp instead of a sub? If so....Rockford Fosgatte has a 200WRMS model (200.1 I think). What ohm load is the speaker wired for? Seeing as its the v2, I am assuming its DVC, and probably either 4-8 ohms. Need to know which one to see whether class D amps will work (2-ohm stable).
John

 

Yes, I have the sub picked out - JL 8w3v2 4 ohms I believe. It only has one connection set for + & - wires, so I don't think is DVC. I just need the power to push it now.

I am leaning towards pushing everything off one 4 ch amp, and bridging ch 3&4 for the sub. My current amp is an Alpine, 30Wx4, 4 ohm, and can't push the JL sub. Not sure I want a D-class amp...

 

Does anyone have any experience with the Alpine MRV-F345?

 

First you need to make sure about the sub. 8w3 "v2" means DVC. You should have more than one +, - inputs for the sub. Then you need to figure what the ohms are as ealier mentioned. Then everyone will be able to give you some amp recommendations. The Alpine MRV-F345 is a good amp, a co-worker has it in his truck and it sounds fine. If you get a JL slash amp you don't have to worry about the ohms as much because the amp will adjust accordingly for you.

 

If your sub is indeed a DVC sub (v2 kind of says that it is), I think the MRV-F345 can only be bridged for a 4-ohm load to a sub. So it will NOT work if the sub is indeed a DVC 4-ohm sub. You should look at their mono amplifiers (Class D). Most of those produce their peak RMS power at a 2-ohm load. If will be tough to find a 4-channel amp that will bridge into a 2-ohm load and still be stable. There are some, but I think they are a bit more $. I dont think Alpine makes one. I want to say that Audison makes one that senses the load, and adjusts output accordingly. But those are mega $.

I think they only adjust down to their stability point. JL is weird in the fact that most amps are rated at either 1 ohm or 3 ohm stability imediances. An AB class amp (2 channel) will still not work, like the 300/2 because its stability rating is only 3 ohms. If you wire up a DVC 4-ohm sub to that, you will either send teh amp into protect by the low load, or you can wire it to an 8-ohm load, but that would basically kill the power output. Best bet is to go with a mono amp.

According to the JL Audio website, you cannot push more than 250WRMS to any of the 8w3v2's without voiding the warranty. If you really want to hear the bass, you should upgrade sub to around 400WRMS as well as the amp.


You might not have much of a choice. Depending on the ohm load of the voice coils. If you got the 8w3v2-D2 each coil is 2-ohms, so it can be wired for a 4-ohm impediance. The 8w3v2-D6 could get the load down to 3-ohms, in which case a JL AB amp would work, but not an Alpine (most AB amps wire for 4-ohm impediances.

 

Okay, I checked, it is DVC, w3v2.

I'm guessing I want to wire it in parallel after bridging channels 3&4 from the amp. If I bridge channels 3&4, does that mean I'm running 4 ohm to the sub or 1 ohm (if the DVC's are wired in parallel)?

If so, is 1 ohm bad for my amp (will it burn it out)? My current amp is an Alpine MRV-F301, rated at 2 & 4 ohms (80w bridged at 4 ohm at 12V).

Also, I'm mainly looking for a low-end fill more than serious mind-shattering bass, so I'm not looking for a ton of power.

If the F345 won't work, what would be a good d-class amp I could wire to my existing amp?

 

I must have misunderstood the JL Audio website. I thought that the R.I.P.S technology in their slash amps allowed them to work within in 1.5-4 ohm range.

 

The big thing now is to find out the impediances of the voice coils in the sub. If you have the box (or it may be stamped / written somewhere on the sub) is should be on there. If it is a 4-ohm sub, it can be wired as either 2 or 8 ohm impediances:

Crutchfield Advisor wiring diagram

I dont know anything really about the specific technologies, but power is generally higher at the lower impediances. JL rates their amp at 250WRMS at a 3-ohm impediance. I would assume that this is the lowest it can go safely (of JL probably would have advertised a higher rating, and a lower impediance threshold).

As far as recommending an amp, what kind of bass are you looking for? Hard hitting (Hip-hop)? Overall strong low end (techno / electronica)? Definition (bass guitar)? What type of music do you listen to. Different amps provide different types of bass. For definition, I like Alpine, JL, Infinity, and Alphasonik. For hard hitting I like Rockford Fosgatte, some Alpines, Soundstream, and MTX. For the low end, you will just have to check individual amp specs as to the range.

John

 

JL's slash amps are stable between 1.5 and 4 ohms when used in stereo mode. When two channels are bridged for mono operation, the slash amps are stable between 3 and 8 ohms.