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DBII Isobaric Wiring (Read 3586 times)
REDTHUNDER
Ex Member



DBII Isobaric Wiring
03/21/06 at 21:13:01
 
I am in the process of building a DBII for my two 12" Rockford subs.  I want to run them Isobaric (clamshell).  I understand that they need to be run 180 degrees out of phase.  

The subs are dual voice coil subs that I would like to run  combined at 1 ohm.  

Is it possible to do this off of 1 mono amplifier, and if so could someone help me out with how to wire it?

Any help would be greatly appreciated

Thanks
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« Last Edit: 03/22/06 at 16:32:52 by REDTHUNDER »  
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J_Rock
Ex Member



Re: DBII Isonbaric Wiring
Reply #1 - 03/21/06 at 21:19:40
 
first take a single sub.  Wire the voice coils in parallel.  this means, a wire goes from + to + and a wire goes from - to -.  two wires.

do the same for the other sub.

Now wire the two subs in parallel but with one in reverse phase.  

4 more wires are added.
- one goes from the first sub + to the second sub -
- one goes from first sub - to second sub +
last two connect to first sub + and - and then to amp + and - respectively.

so it should look like this:

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« Last Edit: 03/21/06 at 21:22:11 by j_rock777 »  
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DirtDawg
Ex Member



Re: DBII Isonbaric Wiring
Reply #2 - 03/21/06 at 21:20:26
 
So, you have 4 - 4 ohm voice coils? To get a 1 ohm load they would all be in parallel. To clamshell, both voice coils on one driver will be reverse phased, but still parallel.
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REDTHUNDER
Ex Member



Re: DBII Isonbaric Wiring
Reply #3 - 03/21/06 at 21:51:07
 
Thanks J_Rock!  That chart makes it easy to follow.  So if I follow the chart then my amp will be runnning at 1 ohm and the subs will be out of phase?  By the way if my subs can handle 400W RMS each, how much power should I be running to them in this configuration.  My understanding is that they need more power running this way.

Also, thanks DirtDawg for the info.
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DirtDawg
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Re: DBII Isonbaric Wiring
Reply #4 - 03/21/06 at 23:26:03
 
[quote author=REDTHUNDER  link=1142979181/0#3 date=1142977867]...  So if I follow the chart then my amp will be runnning at 1 ohm and the subs will be out of phase?  By the way if my subs can handle 400W RMS each, how much power should I be running to them in this configuration.  My understanding is that they need more power running this way.
[/quote]

The chart is correct for 1 ohm hook-up, clamshell. Just be careful using "out of phase" as an expression, because the drivers are out of phase ELECTRICALLY, but you are correcting that condition MECHANICALLY by turning one around and facing them together. In a clamshell arrangement the drivers have to work together as one unit. The only way to do that is to wire one of them electrically out of phase with the other.

I'm in danger of sounding like I'm nitpicking your semantics, but your drivers can't take much more power than their rating, although they do support each other against over excursion to some degree. If you read about needing more power in a clamshell arrangement, it's true, because by facing the drivers together, you have reduced your diaphram radiating area by half and lost 3dB of output as a result. So to get back to the same output in dB you need to double the power, but don't go too crazy and overpower your drivers. If your drivers are overpowered to the point of failure, it will most likely be heat that causes the failure in a clamshell loading.
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J_Rock
Ex Member



Re: DBII Isonbaric Wiring
Reply #5 - 03/21/06 at 23:31:03
 
you can run up to 800 wrms safetly without exceeding your ratings.  To do anymore will increase the chance of breaking something.
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Adrian D.
Ex Member



Re: DBII Isonbaric Wiring
Reply #6 - 03/22/06 at 11:47:06
 
2 subs in clamshell @ 800wrms (400 each) means you have the same spl as 1 sub @ 400wrms
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REDTHUNDER
Ex Member



Re: DBII Isonbaric Wiring
Reply #7 - 03/22/06 at 15:14:31
 
So basically, a person needs to add the combined rms rating of the subs to determine the amount of power needed to run them?   Is this true of this particular set up, or simply a general rule when powering multiple subs?

So if I were running three of these subs, lets say in a sealed enclosure, then I would need to run 1200W to them?


If I were to run single subs in two DBII's, the the power I would put to them would be the same as the isobaric configuration?

Thanks again for all the good informantion...I realize my ignorance is likely annoying, but I do appreaciate the education!
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Adrian D.
Ex Member



Re: DBII Isonbaric Wiring
Reply #8 - 03/22/06 at 16:12:44
 
well, if you have 3 subs in a box, you need to run 1200wrms to the box if each sub is 400wrms.
same goes to isobaric.
add the rms of each sub and that is the rms of the 'group'.
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J_Rock
Ex Member



Re: DBII Isobaric Wiring
Reply #9 - 03/22/06 at 16:45:28
 
basically you just mutliply the rms rating by the number of subs.  

things can change in certain very complex situations but most of the time its simply that.

Also, it only works if all subs are the same.  For instance a 200wrms and a 500 wrms if wired together could recieve 400wrms max before you exceeded the 200wrms rating on the smaller sub.
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Adrian D.
Ex Member



Re: DBII Isobaric Wiring
Reply #10 - 03/22/06 at 17:06:16
 
i was thinking about identical subs. forgot to mention that.
i still can't get it : how does wiring (series/parralel) affect the power distribution between 2 or 3 any amount of speakers ?
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« Last Edit: 03/22/06 at 17:06:31 by adi_ro »  
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REDTHUNDER
Ex Member



Re: DBII Isobaric Wiring
Reply #11 - 03/22/06 at 22:47:00
 
So collectively between my subs I need 800W, but my amp puts out 1400W, would there be a problem using the amp but simply turning down the gain?  

I ask this because I am trying to make use of the equipment I have.
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Adrian D.
Ex Member



Re: DBII Isobaric Wiring
Reply #12 - 03/23/06 at 09:09:14
 
it's actually very good if you have 1400w rms available, because you have headroom. try to adjust the gain so that the amp puts out 800w rms at about 75% volume on the HU
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