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ohm load on Ma Audio amp


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ddsubman 
Copper - Posts: 70
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Joined: December 05, 2005
Location: United States
Posted: December 05, 2005 at 9:44 AM / IP Logged  
Hi everyone! I'm new to this forum and was hoping someone out there could help me. I am running an ma audio hk4000d in my 96' yukon. It is powering a 9515 Digital Designs sub in a 8.5 cubic foot ported box. Here is my problem..When I purchased the sub it was a 2ohm dvc model, I smoked it after almost three years of daily driving and competing in NSPL and Dbdrag. When I got it back from DD after they rebuilt it, I noticed they sent it back as a dual 1 ohm model. I wired the sub in series (vc1+to amp/ vc2-to amp / tied vc1- and vc2+ together) I am assuming this would make a 1 ohm load.  It seems a lot louder to me at 1 ohm, but Ma audio does not recommend running the 4000d at 1 ohm. Does anyone know what kind of power the amp may be making at 14.4v at 1 ohm, and will my amp hold up? Also would it be possible to parallel the vc's on my sub and pull a 1/2 ohm load?  How much power would it make?
Gettin' deafer by the day.......96' GMC yukon-Eclipse CD 5442HU
MA Audio HK4000D-Digital Designs 9515F
150+db with one woofer...DD rules!!!!
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 05, 2005 at 11:17 AM / IP Logged  
DVC 1-ohmvoice coils in series creates a 2-ohm load.  Two of these in parallel creates net 1-ohm, in series net 4-ohms.  MA amps are rated as stable to 2-ohms, so I recommend wiring for a net 4-ohm load.  Unless, that is, you don't care about possibly frying the amp due to overload and/or the speakers due to clipping.
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haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: December 05, 2005 at 11:25 AM / IP Logged  
I know little to nothing about that amp, but here goes...
If the VCs are in series, and the amp is a mono amp, you are running the amp at 2 ohms ( a safe oeration condition). If it is a stero amp, and you have it bridged, you are runnning at 1 ohm (an unsafe operating condition). If MA Audio does not recommend running at one ohm, but if you are actually running in the first configuration, you are safe.
If you wire the coils in parallel, this would make a 1/2 ohm load wich would be FAR into unsafe territory (4 TIMES the already unsafe load recommended by the manufacturer), and this makes me believe you don't understand enough about impedances and Ohm's Law. Please read as much of this website as you can...
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
ddsubman 
Copper - Posts: 70
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Joined: December 05, 2005
Location: United States
Posted: December 05, 2005 at 2:11 PM / IP Logged  

If you wire the coils in parallel, this would make a 1/2 ohm load wich would be FAR into unsafe territory (4 TIMES the already unsafe load recommended by the manufacturer), and this makes me believe you don't understand enough about impedances and Ohm's Law. Please read as much of this website as you can...

I realized my error about what ohm load I am running. I still want to know what kind of power the amp will make at 1/2 ohm load....I was hoping someone with Ma audio amplifier experience could let me know what experience they have had with their amps...As many people know, not all amps are created equal. I have had many amps that were only rated at 4 ohms that performed flawlessly at 1 ohm or less. I was just wondering if anyone else had tried it before and what experience they had before I rewiRED / fried a $750 amp. I would only be running the amp under these conditions long enough to get a meter reading at the next NSPL competition. It would be reverted back to 2ohm operation for ride around purposes. Thanks.

Gettin' deafer by the day.......96' GMC yukon-Eclipse CD 5442HU
MA Audio HK4000D-Digital Designs 9515F
150+db with one woofer...DD rules!!!!
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: December 05, 2005 at 2:26 PM / IP Logged  

ddsubman wrote:
 I still want to know what kind of power the amp will make at 1/2 ohm load.

Probably zero, as it will most likely shut down in protection or fry at that load.  Mobile Authority amps are not very robust, in general.

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ddsubman 
Copper - Posts: 70
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Joined: December 05, 2005
Location: United States
Posted: December 05, 2005 at 2:45 PM / IP Logged  
DYohn wrote:

[Probably zero, as it will most likely shut down in protection or fry at that load.  Mobile Authority amps are not very robust, in general.

Thats' funny.. After almost 2 weeks I finally received a reply from MA's tech department. The tech guy assured me that with the protection removed the amp would easily run all day a .5 ohm. The question remains the same now as it did 5 hours ago..Just pretend my Mobile Authority amp is a "robust" high end unit capable of producing 3600watts at 2ohms and 14.4volts. Now approximately how much wattage will it produce at .5 ohm load.

Gettin' deafer by the day.......96' GMC yukon-Eclipse CD 5442HU
MA Audio HK4000D-Digital Designs 9515F
150+db with one woofer...DD rules!!!!
stevdart 
Platinum - Posts: 5,816
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Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: December 05, 2005 at 2:56 PM / IP Logged  

You will have to measure it, as the answer is not a math equation.  Perhaps the MA tech can fill you in with that info too.

I'll explain it like this for those who will read this thread:  say, you have an amp that has been measured by the factory and rated at 2 ohms and at 4 ohms.  You can figure the output in between those ratings, and you can figure the output at a higher load than 4 ohms.  But to figure the output at a lower load is just guessing because you don't know what the limitations of the amp's rail voltage are.  You can't assume that if the rating at 2 ohms is whatever, that the output at 1 ohm is double that.  Or that the output at 1/2 ohm is double the 1 ohm rating.  You could find....by measuring....that the output at 1 ohm is the same as it is at 2 ohm or  maybe just a bit more.

Limitations imposed by the amplifier build.  And generally, putting a load on any amplifier that is lower than the lowest power rating given by the manufacturer is a bad idea.  Cheater amps, that is, those that are well known, are the exceptions to the rule.  But be sure.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
youngone 
Silver - Posts: 269
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Joined: September 28, 2005
Location: United States
Posted: December 05, 2005 at 3:09 PM / IP Logged  
4200 to 5000w at .5ohms. it will be very risky to pump that amp that high. And that amp is a good quality amp gust not for sq. it is gust designed to push a lot of power. i don't know about that much though. .5ohms is real close to the point that you will have a big problem with the system as a hole. that is a huge amount of power to draw from your car, even if it is made for that the AMP is not made to allow that much power to go throw it. And i don't really know how it would do under that condition. it is VERY risky to do. i do not recommend doing it. and if you do i would recommend having a fire extinguisher handy.
Want to know some good equipment- JL,Adire Audio,Mcintosh,Brax,Helix,Eclipse,JBL,RE,Dimoand Audio,Zapco, pritty much anything DYhon,Forbidden recommend
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ddsubman 
Copper - Posts: 70
Copper spacespace
Joined: December 05, 2005
Location: United States
Posted: December 05, 2005 at 3:17 PM / IP Logged  

Thank you, that is as close as I have come all day to getting an answer to my question...Would you be willing to tell me how I could measure it? I really don't want to wait another 2 weeks to get a reply from MA. In their last reply all they did was tell me it would work and sent me a diagram showing what resistors to remove to kill the protection. I came to this site for help, not to be told how dumb I am when it comes to car audio and how bad my choice of amplifier was......

"To be, rather than to seem.."

Gettin' deafer by the day.......96' GMC yukon-Eclipse CD 5442HU
MA Audio HK4000D-Digital Designs 9515F
150+db with one woofer...DD rules!!!!
stevdart 
Platinum - Posts: 5,816
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member consistently provides reliable informationspace
Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: December 05, 2005 at 3:30 PM / IP Logged  

Relax, David.  Your attitude is showing.

Measure the output at the speaker terminals in AC volts.  Use Ohm's Law to find power given the two knowns that you will now know:  voltage and impedance load.  P = E^2 / R

It's accurate to do this with a bench test, but doing it in the car will get you close.  And keep the sub unhooked while you do it.  Use a 50 Hz test tone recorded at 0 db.  But you should have first found the point of clipping with the tone and the sub hooked up.  Unhooking the sub to measure voltage just takes the strain off the sub while you're doing the voltage test, because it's not necessary to hear the tone at this time.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
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