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Old 11th September 2006, 05:16 AM   #1
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Default Carver PM 1.5 and PM -1200 2 Ohms ?

Hello, i was wondering if it were posiible to modify these amps to be capable of handling 2 ohms in stereo and 4 ohms in bridged operations ?

Thanks...
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Old 11th September 2006, 09:58 PM   #2
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No takers on this ?
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Old 11th September 2006, 11:04 PM   #3
anatech is offline anatech  Canada
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Hi pjaneiro,
I think there was one model built as a mono amp to handle 2 ohm loads. One amp card with all the output positions used, possibly lowered B+ values.

Why one earth would you do it this way?? It doesn't make any sense.

Run 4 ohms one each channel not bridged. Man, that's going to be silly loud. You will also need a rock solid AC supply. You would with any amp, more so with the Carver.

-Chris
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Old 11th September 2006, 11:37 PM   #4
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I don't see any practical way to do this. The Carvers are pretty much designed for high voltage/low current (relatively) and are best suited for 8 ohms.

Unless the rail voltages were lowered, additional outputs paralleled, and the class 'G' rail switching diodes beefed up, there really isn't a decent way to do it.
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Old 11th September 2006, 11:45 PM   #5
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Hi DCPreamp,
The Carver amps will handle 4 ohm speakers just fine. I did mention the 2 ohm model had the changes you recommended. I actually worked on a few.

The main problem is that most people don't understand that those amps put out every watt they claimed to deliver. There are many dead pro woofers to bear witness to that.

Now bridging is another story again. 8 ohms min. and ungodly power out. A waste of time since you will get power compression as a result. Hot voicecoils are a waste.

-Chris
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Old 12th September 2006, 02:46 AM   #6
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The main reason for me wanting to know how to mod the amps is that I have ONE 4 ohm sub capable of handling just about 1000 rms, it's a dual voice coil where each coil are 2 ohms or if i were to run them in series it would give me of course 4 ohms, i had read somewhere that someone here tried to run a 4 ohm speaker when the amp clearly said 8 ohms minimum in bridged mode, and in the end burnt the outputs...So i just want to know if it would be safe to run my sub in bridged or if i need to do anything to the amp...

Thanks
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Old 12th September 2006, 02:53 AM   #7
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On another note, i noticed that the my pm 1.5 would "lower" it's volume when it played at a high and sustained volume with xtreme low frequencies, i would say that the amp was pushing just about 350w when i noticed that it started to lower it's volume, as soon as the music would relax on it's low freq, you could hear the volume go up, my pm-1200 does not do this..., should i replace the caps with larger ones ? or was it designed to do this ? The speakers were 18" eminence, i know that they handle the power, i peviously used a crown macro tech 2400 on those monsters...

Once again Thanks...
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Old 12th September 2006, 12:31 PM   #8
anatech is offline anatech  Canada
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Hi pjaneiro,
Some Carver amps have an optocoupler to mute the input as part of the protection. What you are saying is no surprise. I'll bet the chassis is pretty warm when this happens.

Do not bridge the Carver into 4 ohms. Your dual voice coil woofer is really a 4 ohm with less efficiency. There is a space penalty for a split voice coil.

At this point I'd have to say that the Carver and this speaker are not compatible. The Carver does not have to resort to any tricks to deliver power, and the speaker is using the low impedance trick for more power. Stop and think now. At 2 ohms you have far greater power loss in the connections and cable(s). Your damping factor is also compromised. It's the same with any amp. A loudspeaker array would have far greater impact and dynamics because each voice coil runs much cooler. Of course it's larger and that may be a problem for you. I'm guessing it's a portable rig?

Also, if you can achieve the same Xmax with 200W as this speaker does at 1000W (therefore SPL), where is the advantage? I don't know the specs, but I know when people get caught in the power handling trap.

-Chris
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Old 12th September 2006, 01:31 PM   #9
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for the issue with my 18" woofers, well, the chassis is just warm, well, actually when the 18" woofers were playing it was "normal" the fan were running at high and would speed up as the bass was pumping, they are 18" eminence 8 ohm running in stereo, when i use the pm-1200 it does not do that, it keeps playing at same music level all night, so i wonder what could be the difference between my pm 1.5 and the pm-1200

For my dual voice coil woofer i tried last night running it both coils plugged in series giving me 4 ohm on my pm-1200 running bridged, it works it pumps out power like i never tought it could and then.....silent, i could've boiled eggs on the casing i guess the carver can't handle that impedance load , so what's the mods that you said that were done on the cube to accomodate this ?, i have my eyes on two monsters from a canadian loudspeaker company they are single coils but they run at 2 ohms with a handling power or 1300 w rms 2800 peak, i love my carvers and i don't want speding money on other amps like the behringers ep2500 that actually say they run 2 ohms...

Thanks...
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Old 12th September 2006, 02:44 PM   #10
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Hi pjaneiro,
Quote:
what could be the difference between my pm 1.5
Your PM 1.5 is sick I bet. There are a pair of dual section capacitors that tend to fail. The replacements where unavailable, so Carver came out with a capacitor PCB to replace both. There is a member that performed a great modification on his amp for this problem. There is also a picture of his work. I just can't seem to locate it at the moment.

Quote:
so what's the mods that you said that were done on the cube to accomodate this ?
Those were not mods. That specific amplifier was designed that way and utilized the entire two channel chassis for a single channel with twice the outputs. There is no mod that will accomplish this. Also, it's mono, so not bridgeable. It's nice that it wasn't the typical cheat "bridge the lower powered amp for a high power mono" trick.

Quote:
i have my eyes on two monsters from a canadian loudspeaker company they are single coils but they run at 2 ohms with a handling power or 1300 w rms 2800 peak
Diminishing returns. I wouldn't go this way. You would be further ahead with a few woofers. Look carefully at the efficiency, both cold and hot. You will lose a good 2 dB hot. Don't buy a speaker on power handling, buy it on efficiency and SPL among other things. Power handling is only the speaker's ability to dissipate heat. It doesn't necessarily make it any better as a speaker.

-Chris
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