How do I wire a dual opposed subwoofer?

[suttondesign]

Hi all. As you know, I am building a dual opposed 11” subwoofer using Scan-Speak 4-ohm (nominal) drivers. I use a MiniDSP plate amp in bridge mode. How do I wire this sub? Series? Parallel?

 

[sam_adams]

Series wiring gives you 8 Ω. Parallel wiring gives you 2 Ω. Choose wisely.

 

[staticV3]

??
There's really only one way to wire that setup.
Drivers in series and so the cones move opposite from each for force cancellation.
??

The drivers are mounted facing each other and the cones need to move in the same relative direction. Both series and parallel are possible here.

 

[suttondesign]

No, I'm afraid not. Since the drivers are mounted opposed the cones need to move in opposite directions to achieve the force-cancellation objective.
And, since he's using the amplifier in bridged mode, a parallel connection would yield an approximate 1-ohm load on each amplifier channel. Not good.
Series is the only wiring method.

This seems correct to me. What if I unbridge using the original 2-channel jumper config? The amp has a thermal protection circuit, so maybe a 2 ohm load could be okay?

 

[suttondesign]

If you operate the amplifier in the normal (non-bridged) mode, each channel will see a 4-ohm load. I see no issue with that. It's preferable, actually.

I don't know why you started another, separate, thread???????

Because it’s a different and very specific question.

 

[suttondesign]

If you operate the amplifier in the normal (non-bridged) mode, each channel will see a 4-ohm load. I see no issue with that. It's preferable, actually. However, slight differences in the amplifier channels/DSP-setup could cause some non-symmetrical operation.

I don't know why you started another, separate, thread???????

I also need a lot of power. I could just use the second plate amp too. Two of those amps, each in bridge mode, is a lot of power.

 

[staticV3]

No, I'm afraid not. Since the drivers are mounted opposed the cones need to move in opposite directions to achieve the force-cancellation objective.

Here's how I'd wire dual opposed subs in parallel:


The cones would move in the same relative direction, so both "out" at the same time and "in" at the same time.

If you flipped the polarity on one driver, then you'd get basically no sound, and a violently shaking enclosure.

Whether OP's Plate Amp can handle the 2Ω inpedance of a parallel config is another matter of course.

 

[Anonamemouse]

Here's how I'd wire dual opposed subs in parallel:
View attachment 309305

The cones would move in the same relative direction, so both "out" at the same time and "in" at the same time.

If you flipped the polarity on one driver, then you'd get basically no sound, and a violently shaking enclosure.

Whether OP's Plate Amp can handle the 2Ω inpedance of a parallel config is another matter of course.

I would do series, most amps really don't like low Ohm impendance.
And: Mono. Not stereo.

 

[somebodyelse]

If you flipped the polarity on one driver, then you'd get basically no sound, and a violently shaking enclosure.

You'd get a dipole with the wrong EQ, rather than the intended monopole. There will be sound, but not the sound intended.

 

[sigbergaudio]

Generally speaking, serial connection is not advisable, as minor differences in the drivers could lead to them not receiving the same amount of power.
The best solution due to the low impedance of the drivers is perhaps one channel per driver instead of bridging.

 

[mcdn]

I‘m not sure the ICEpower 250asx2 is a great choice for this application. You can either run each driver off a single channel so each channel drives a nominal 4ohm load, or put the drivers in series and run the amp bridged. Either way you only have 500w available, which is marginal based on what I recall of your plans. I would be aiming more toward 500w per driver if I were you, to allow some decent headroom instead of maxing out the amps. You can sim it all out in VituixCAD or similar to get a more precise answer.

 

[suttondesign]

I‘m not sure the ICEpower 250asx2 is a great choice for this application. You can either run each driver off a single channel so each channel drives a nominal 4ohm load, or put the drivers in series and run the amp bridged. Either way you only have 500w available, which is marginal based on what I recall of your plans. I would be aiming more toward 500w per driver if I were you, to allow some decent headroom instead of maxing out the amps. You can sim it all out in VituixCAD or similar to get a more precise answer.

thanks. yes, i am getting the larger minidsp plate amp, with double the power over the smaller minidsp amp. i have learned the minidsp software and would rather stick with those plate amps for now.

i want to get the thing working with what i have, then switch out when i get the other amp. based on the help in this forum.

 

[suttondesign]

Generally speaking, serial connection is not advisable, as minor differences in the drivers could lead to them not receiving the same amount of power.
The best solution due to the low impedance of the drivers is perhaps one channel per driver instead of bridging.

thanks. do you have the same concern if the drivers are identical, bought at the same time and newly manufactured?

 

[suttondesign]

That would be the "opposite" relative direction, not the same relative direction.
And for the reason I mentioned above, the effective load on the bridged-configuration amplifier channels would be 1 ohms, not 2 ohms. So, not an appropriate hookup.

i agree. bridged mode causes this problem. easy to solve by abandoning bridge mode, but i still end up at 2 ohms.

 

[sigbergaudio]

thanks. do you have the same concern if the drivers are identical, bought at the same time and newly manufactured?

I'm sure no puppies will die if you wire them in series, but theoretically parallell will be better.

 

[suttondesign]

got this dual opposed sub hooked up today. series wiring. tested polarity with a battery with wires soldered to each end, and cones behave the same. with initial ear tweaks, very good, but still need to run REW.

took the occasion to consolidate my 9” scanspeak cubes into one dual opposed, also connected in series, cutting down the long excursions I was pushing. plan to build a new, better, bigger version of those using the dual config. they’re very expensive drivers, and I’ve got plenty of baltic birch! those drivers have a -3db at 29hz in a 1.7 cu ft sealed enclosure.

 

[mcdn]

@suttondesign I did a quick sim of a pair of 28W/4878T00 drivers in a 1.26cu.ft (35.7L) enclosure. 250W per driver actually seems pretty much OK. It can't quite drive them to xMax but you get 99dB at 20Hz, so 105dB with the pair of enclosures, plus room gain. Basically at least you can't mess up and blow up the drivers or tear them apart with that power.

 

[suttondesign]

@suttondesign I did a quick sim of a pair of 28W/4878T00 drivers in a 1.26cu.ft (35.7L) enclosure. 250W per driver actually seems pretty much OK. It can't quite drive them to xMax but you get 99dB at 20Hz, so 105dB with the pair of enclosures, plus room gain. Basically at least you can't mess up and blow up the drivers or tear them apart with that power.

View attachment 309639

awesome! i have the larger minidsp plate amp on its way, and it’s 250w into each 4 ohm channel. thank you for this info.

 

[suttondesign]

early testing. 11” dual and 9” dual. Initial dialing-in by ear, using 24db slope crossovers in the 40hz region (plus or minus 5) yields far more bass than I've ever had in any setup. I can't turn the plate amps up to more than 12-o'clock. I can run the Bladerunner 2049 score unconstrained for the first time (I have to high-pass the Linkwitz 521.4 for that recording to avoid over-excursion of their open-baffle woofers).

The smaller 9" seem to be adding a little muddiness at about 65hz, something I need to address with either the Q of the boost or else the crossover. I don't have it when running just the 11" drivers. Could be a mode getting hit from the location of the smaller drivers.