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Old 22nd July 2009, 03:31 AM   #1
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Default Design Stable @ 1 Ohm Nominal?

Good evening all,

I am experimenting with a Frankenstein re-build of an old pro-sound subwoofer. The only voice coil I could find so far is from the car audio world, and is rated at a disturbing 1 ohms nominal impedance.

Do any of you know of a module or proven design which is stable at such a load? I thought of using a car audio amplifier, but it seems a shame to step the mains voltage down to 13.5 or whatever, only to have the power supply in the mobile amp step it back up. North of 500 watts RMS if possible!

Thanks for your help,

JF
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Old 22nd July 2009, 07:42 AM   #2
luka is offline luka  Slovenia
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I think that none of kit moduls are made for 1R operation, if you would make it yourself... but I would look into getting some cheap monoblock, and powerd it from PC supply or battery with charger on
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Old 22nd July 2009, 01:50 PM   #3
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Hi Luka,

Thanks for the post. Yeah, it might be a tall order. I wonder what constitutes 1 ohm 'stability'? I would imagine the limiting factor is the current rating of the mosfets. Perhaps this could be controlled by limiting the voltage across them?
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Old 22nd July 2009, 02:33 PM   #4
luka is offline luka  Slovenia
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well, input and output current is the most problem, and 2R stabil amp will work on 1R, at lower power, but depends on amp, there are some that will push 1R at full power too, not really good for amp, but they can. So if you get say 2.5kw amp stabil at 2R, it will work on 1R @ say 1.5kw easy...

But all depends on many factors, just to name few: your electrical system, speaker impedance raise, design of amp,...

I'm pretty sure you would be best off with buying second hand 1R stable amp.
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Old 22nd July 2009, 05:48 PM   #5
wingman is offline wingman  Denmark
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alot of digital car amps will do 1ohm and some 0,25-0,5ohm.

So why is it so hard to find one for out of car use ?
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Old 22nd July 2009, 06:12 PM   #6
back is offline back  Greece
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i don`t know what is your price range but hypex modules are stable at 1 ohm.

ucd700 or ucd2k will do.
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Old 23rd July 2009, 06:14 PM   #7
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Back: Thank you for the reference to the Hypex products. They look very interesting but however they are a little out of my price range.

Wingman: You're right, it's hard to find a 1 ohm capable design that is not intended for automotive use. That may be a product of those SPL competitions (uhg...) in the mobile audio world.

Luka, I agree, I think the cheapest way will probably be to purchase a used car amp.


Here's a question: could I take a massive automotive amplifier, and bypass its internal power supply, feeding it's amplifier section directly wit the voltage it expects? Instead of stepping the mains voltage down to 13.5 or so with a huge transformer, only to have the amplifier step it back up, could I skip this step and supply the higher voltage directly? For example, here is a picture of the inside of a Hifonics car audio amplifier. It looks like the high-voltage power supply section is at the far end, and the amplifier near the camera. I wonder if I could figure out what the high voltage power supply provides, then create my own power supply that uses AC mains voltages?

Has anyone here tried such a project?

Click the image to open in full size.
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Old 23rd July 2009, 06:38 PM   #8
luka is offline luka  Slovenia
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Answer is YES, if you provide all the voltages, you are I think good to go, since all rectiviers will block current going into trafos...

But note something, you will be using 50/60Hz trafo [I assume], so it won't hurt if you bring DC into amp, and have some capacitance outside amp, and I would settle for some 10-20v lower voltage then this amp runs at, coz in car, voltage for amp drops a lot on 1R load, normal trafo will hold this voltage better, but then again, higher voltage, less current for same power on output
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Old 25th July 2009, 03:19 PM   #9
judtoff is offline judtoff  Canada
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Quote:
Originally posted by J.R.Freeman
Back: Thank you for the reference to the Hypex products. They look very interesting but however they are a little out of my price range.

Wingman: You're right, it's hard to find a 1 ohm capable design that is not intended for automotive use. That may be a product of those SPL competitions (uhg...) in the mobile audio world.

Luka, I agree, I think the cheapest way will probably be to purchase a used car amp.


Here's a question: could I take a massive automotive amplifier, and bypass its internal power supply, feeding it's amplifier section directly wit the voltage it expects? Instead of stepping the mains voltage down to 13.5 or so with a huge transformer, only to have the amplifier step it back up, could I skip this step and supply the higher voltage directly? For example, here is a picture of the inside of a Hifonics car audio amplifier. It looks like the high-voltage power supply section is at the far end, and the amplifier near the camera. I wonder if I could figure out what the high voltage power supply provides, then create my own power supply that uses AC mains voltages?

Has anyone here tried such a project?

Click the image to open in full size.

I just wanted to say that is my amp :P
I was wondering why it looked so familiar.
Anyways I am using a computer PSU to supply a BXi1606D(that amps little sibling) current.(Oh I'm running it at 4 ohms...)

You could probably do that, but is it really worth it? There are more than one rail, there's low voltage rails for the op amps, high voltage for the H bridge.
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Old 25th July 2009, 03:33 PM   #10
luka is offline luka  Slovenia
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Quote:
Originally posted by judtoff but is it really worth it?
x2, is it?
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