MS2250 and 2 DVC 12w7 3ohm

[jrobinson]

Guys,
After sending both amps off to PG for cap replacement / tuneup,
I finally got my ms2250 and M44 installed by a local shop and purchased 2x JL 12w7 DVC subs with a custom enclosure from them.
Upon inspection of the install, i noticed (with my fluke meter) that each cone is wired internally in the box presenting a 3ohm load. I havent disassembled their enclosure so im not 100% sure, but thats the only thing that makes sense. If they were in parallel it would be showing me a .75 ohm load if each VC were 1.5 ohm (which i think they are).

With this in mind, im assuming the total impedance of the 12w7 is 1.5 ohm per VC and the voice coils are wired in series to produce a total of 3ohm resistance per sub. I have also noticed, they installed the ms2250 amp set to run in stereo mode with both channels wired to a seperate subwoofer.

My quesstions are:
What would be the ideal way to wire the ms2250 to the pair of dvc subs with the best performance considering these subs are 3ohm and DVC?

Would it be to present 1.5 ohm bridged to the amp by wiring the 2 subs together in series? ((cone1 - 2x 1.5ohm =3 in series)(cone2 - 2x 1.5ohm = 3 in series)= 1.5 ohm in parallel), bridged selector switch on?

Or would it be better to run the subs in stereo mode with each channel running at 3ohm? Currently i do not belive this is optimal, as im just not seeing the level of power out of the ms2250 that i would expect.
Also, a problem im seeing right now (in stereo mode) is the subs do not 'hit' at the same time, rather they alternate push / pull. If i stay in 3ohm stereo mode, should i reverse the phase on one of the cones?

Is the ms2250 going to be stable running bridged at 1.5 ohm?

[maxxsq]

Guys,
After sending both amps off to PG for cap replacement / tuneup,
I finally got my ms2250 and M44 installed by a local shop and purchased 2x JL 12w7 DVC subs with a custom enclosure from them.
Upon inspection of the install, i noticed (with my fluke meter) that each cone is wired internally in the box presenting a 3ohm load. I havent disassembled their enclosure so im not 100% sure, but thats the only thing that makes sense. If they were in parallel it would be showing me a .75 ohm load if each VC were 1.5 ohm (which i think they are).

With this in mind, im assuming the total impedance of the 12w7 is 1.5 ohm per VC and the voice coils are wired in series to produce a total of 3ohm resistance per sub. I have also noticed, they installed the ms2250 amp set to run in stereo mode with both channels wired to a seperate subwoofer.

My quesstions are:
What would be the ideal way to wire the ms2250 to the pair of dvc subs with the best performance considering these subs are 3ohm and DVC?

Would it be to present 1.5 ohm bridged to the amp by wiring the 2 subs together in series? ((cone1 - 2x 1.5ohm =3 in series)(cone2 - 2x 1.5ohm = 3 in series)= 1.5 ohm in parallel), bridged selector switch on?

Or would it be better to run the subs in stereo mode with each channel running at 3ohm? Currently i do not belive this is optimal, as im just not seeing the level of power out of the ms2250 that i would expect.
Also, a problem im seeing right now (in stereo mode) is the subs do not 'hit' at the same time, rather they alternate push / pull. If i stay in 3ohm stereo mode, should i reverse the phase on one of the cones?

Is the ms2250 going to be stable running bridged at 1.5 ohm?

12W7's are 3 ohm svc subs. I think best option would be subs connected series = 6 ohm mono load to amp.

[jrobinson]

Yes, so in fact the 12w7 is a SVC 3ohm as opposed to a DVC like i thought it was. That explains the 3ohm reststance from the sub.

Thank you for the correction, JL's documentation is pretty weak in that regard.
I did finally find this on their site:

"So why do the W7’s use a 3 ohm voice coil?
We’ll start by clarifying that the 8W7, 10W7 and 12W7 have single 3 ohm voice coils. The 13W7 has dual 1.5 ohm voice coils."

Why would i want to run 6 ohm load to both subs, this would decrease my power from the amp to approx 775 watts total in bridged mode?

Currently they are running at 3 ohm stereo with about 550 watts to each cone and its not enough power to drive those 12w7's. They barely get to bumpin with the amp gain on half, and bass boost on half, HU cranked up.

Is the ms2250 stable at 1.5 ohm bridged?
Can i get 1800-2000 watts from the amp at that load?

I am going to order some high flow fans for the fan shround since the 3 stock fans push very weak airflow. Ive found some 80mm x 1" fans that can put out 80CFM of airflow at 12v x .55 amp ea.

[maxxsq]

Why would i want to run 6 ohm load to both subs, this would decrease my power from the amp to approx 775 watts total in bridged mode?

Currently they are running at 3 ohm stereo with about 550 watts to each cone and its not enough power to drive those 12w7's. They barely get to bumpin with the amp gain on half, and bass boost on half, HU cranked up.

Is the ms2250 stable at 1.5 ohm bridged?
Can i get 1800-2000 watts from the amp at that load?

W7's needs power, I had one 12W7 first connected to modified ZPA 0.5 and later second half of MS 1000 TA. It was loud in both setups.

Maybe you'll need more powerfull amp for two subs. Anyway, MS 2250 can't handle under 4 ohm mono loads due to heat problems.

[bdubs767]

please save the ms2250 for something better


Give the each 12w7 a RSd1200.1 wired to 1.5 ohms.

[Haz]

please save the ms2250 for something better


Give the each 12w7 a RSd1200.1 wired to 1.5 ohms.

The 12W7 is a single voice coil sub at 3 ohms, its the 13W7 which is dual 3ohms (13W7 has 2 voice coils). And I wouldn't give the 12W7 more then 1000 watts max, they are not designed to handle much more then there rated power. The 12W7 is rated for 750 watts rms.

Haz

[jrobinson]

And so, using existing amp, the best wiring scenario is that of stereo at 3ohm both channel driven.

Is there any advantage to running one of the subs out of phase (ie reversing + and - on one of them) since i seem to be getting push/pull between cones if you know what i mean?

[majette]

And so, using existing amp, the best wiring scenario is that of stereo at 3ohm both channel driven.

Is there any advantage to running one of the subs out of phase (ie reversing + and - on one of them) since i seem to be getting push/pull between cones if you know what i mean?

yes, one may be wired out of phase. if you disconnect one and the bass gets louder, they are wired out of phase.

[jrobinson]

Success,

I wired up a single 12w7 at 3ohm bridged off the amp and im not seeing any heat issues with the amp.
Level of bass in the truck has effectively doubled, using only one sub.
I find it hard to believe this amp is not stable bridged at 3 ohm load. I ran it on max for over an hour with no thermal issues. It was hitting so hard all my lights were dimming.

With all 4 corners disconnected, i noticed the sub was also playing midrange frequencies so i rewired the ms2250 inputs off of the sub out on the m44. With active xover set at 80hz. Im getting twice the sound i was before, no clipping or overload on the ms2250 amp.
I have an alpine iva-w205 HU, and im not sure what the xover frequency and slope are on the sub out channel. It sems like there is alot of midrange in that output. Does anyone know what the sub out freq/slope is for that unit?

I will be looking to return the other 12w7 and dual sub box for a single 12" pro wedge. This seems to work alot better then 2 subs in stereo. It also takes up half the room in the back.

[mhyde71]

I am going to order some high flow fans for the fan shround since the 3 stock fans push very weak airflow. Ive found some 80mm x 1" fans that can put out 80CFM of airflow at 12v x .55 amp ea.

Where did you find some good fanz?? I'm looking for some just the same...