Getting new R1200-1D Monoblock amp tomorrow, not sure how to safely pair ohms withsub

[Kadenj]

Firstly,

I have 2 RF P3-12s in a ported RF enclosure.

I had an old 1000 watt eclipse mono block amplifier that blew, and I ordered a new R1200-1D online and i'll be getting it tomorrow.

So i have the p3 12's that have the "kevlar" weave on the face, so i believe they are the old version (or new version i honestly don't know and really would like to!!!!) Which are rated at 400-600 rms. I believe it's a 4 ohm dependency but it is a dual voice coil. My question is, with the r1200-1d rated at 400-800-1200 rms at 1,2,4 ohms. How do i know what ohms my subs are, and how to setup my amp with the proper amount of ohms. Any help would be so much appreciated guys! Thanks!

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[AGame615]

dual 4 ohm voice coils like your p3's should be wired parallel to see a 1 ohm load. and to set the gain on your amp you need to volt match it with your head unit. if i were you i'd use this sites search function to figure out how to do all this correctly.

 

[Kadenj]

When you say, use the search function what should I search for? i'm sorry but i'm just not very fluent in this ohm load talk, and am a little clueless in what i'd search for.

 

[Kadenj]

When you say, use the search function what should I search for? i'm sorry but i'm just not very fluent in this ohm load talk, and am a little clueless in what i'd search for.

also, I'm asking about my specific setup, this is a very broad car audio forum and most people do not have my exact setup,

 

[The_Quiet_One 10+ year member]

You should have a model number to go by somewhere on the sub. If you tell us the entire model number it should help us. If you have a multimeter you can check the resistance yourself. Ideally you have 4 ohm dvcs so you can wire to 1 ohm.

 

[AGame615]

you can google subwoofer wiring diagrams and such and also how to gain match an amplifier..

 

[Kadenj]

You should have a model number to go by somewhere on the sub. If you tell us the entire model number it should help us. If you have a multimeter you can check the resistance yourself. Ideally you have 4 ohm dvcs so you can wire to 1 ohm.

I have two RF P3D4 12'' woofers. I just measured the ohms at the box, and it measured around 1.3 ohms. What does this mean?

 

[fatboytyler]

I have two RF P3D4 12'' woofers. I just measured the ohms at the box, and it measured around 1.3 ohms. What does this mean?

P3D4... The D4 stands for Dual 4 Ohm Voice Coils. Therefore run them in parallel and you'll be golden. Not exactly sure what you mean by measured it at the box.

 

[The_Quiet_One 10+ year member]

If you are getting 1.3 ohms depending on the multimeter you're using that means you're probably already wired to 1 ohm since most cheaper dmms read a bit higher than actual DCR. You should be fine just throwing the RF in there if it's 1 ohm stable. Set your gains properly and jam away.

 

[Kadenj]

If you are getting 1.3 ohms depending on the multimeter you're using that means you're probably already wired to 1 ohm since most cheaper dmms read a bit higher than actual DCR. You should be fine just throwing the RF in there if it's 1 ohm stable. Set your gains properly and jam away.

So with the new amplifier, for 1.0 Ohm should i use the V(voltage)=Root P(power of amp) x R(ohm) equation? If if i do it that way. The Rf1200-1d is rated at (at least) 1200 RMS. That being said, I should have V = Root (1200 x 1.0), V = 34.641. So if I poke the leads of my meter into the speaker terminals accordingly on the amp, with all adjustments at 0 except for Low pass (which i will have set at max), turn on the amp with a song playing and turn up the gain until i reach that desired ~34.6v will this optimize my setup?

 

[The_Quiet_One 10+ year member]

That may get you roughly there, but speaker output will be in AC current. It's not quite as simple as using Ohms law for DC current. You also will not be able to see if you are sending a distorted signal to your subs. Without access to a oscope or other gain setting tools the best you can do is try and get in the ballpark. I suggest being conservative with HU volume and EQ settings when setting your gain with a dmm.

 

[fatboytyler]

That may get you roughly there, but speaker output will be in AC current. It's not quite as simple as using Ohms law for DC current. You also will not be able to see if you are sending a distorted signal to your subs. Without access to a oscope or other gain setting tools the best you can do is try and get in the ballpark. I suggest being conservative with HU volume and EQ settings when setting your gain with a dmm.

What are you talking about? That formula is what is needed to set gains via multimeter. Using a clean test tone (I like -3 DB so I induce very slight clipping here and there) or some of your regular music you will put the multimeter leads on the speaker leads without the speakers plugged in, head unit volume at 75% with all EQs flat/off, you'll start turning your gain up until you reach your desired voltage.

Few things to note though... Your HU preout voltage needs to be 2+ Volts to be suitable. Your multimeter is likely not high end enough to accurately get a voltage reading on music because of the extreme and sudden drops so a test tone might be better. Your Lowpass filter needs to be set according to your box tuning. I would suggest aiming for the 34.0 to 34.5 range to help reduce chances of clipping and make sure you double check your numbers (I didn't, but make sure).

 

[The_Quiet_One 10+ year member]

What are you talking about? Do you not know there is a difference between AC and DC voltage calculations? There is a phase angle you have to take into consideration when dealing with AC signal (Speaker output of the amp is AC) The DC version of Ohm's law and the DMM method gets you in the ballpark, but isn't a great way to set your gains imo. It's better than just guessing, but leaves a lot to be desired. HU volume to set gains depends on HU and telling OP to trust the 75% mark to be distortion free could lead to trouble depending on the head unit. Also depending on his electrical the voltage reading may be reflecting a square wave. Everything else you suggested I agree with though and he shouldn't run into issues unless he plays tones or plays heavily bass boosted music. It's important for OP to know some of the possible pitfalls of using the DMM method and roll with those considerations in mind.

Op what's you head unit and electrical like?

 

[Kadenj]

What are you talking about? Do you not know there is a difference between AC and DC voltage calculations? There is a phase angle you have to take into consideration when dealing with AC signal (Speaker output of the amp is AC) The DC version of Ohm's law and the DMM method gets you in the ballpark, but isn't a great way to set your gains imo. It's better than just guessing, but leaves a lot to be desired. HU volume to set gains depends on HU and telling OP to trust the 75% mark to be distortion free could lead to trouble depending on the head unit. Also depending on his electrical the voltage reading may be reflecting a square wave. Everything else you suggested I agree with though and he shouldn't run into issues unless he plays tones or plays heavily bass boosted music. It's important for OP to know some of the possible pitfalls of using the DMM method and roll with those considerations in mind.
Op what's you head unit and electrical like?

i have a pretty low end sony head unit, but im using all stinger wiring, 2 guage power/grd

 

[n2audio 5,000+ posts]

What are you talking about? Do you not know there is a difference between AC and DC voltage calculations? There is a phase angle you have to take into consideration when dealing with AC signal (Speaker output of the amp is AC).

No - there's not. We want the power out of the amp to be close to clipping when the HU is close to clipping. There's no reason for it to be any more complicated than that.

We're measuring AC rms voltage. Do this with a tone and any functional DMM it will work out just about perfectly.

It is ridiculous that some people on this forum want to elevate setting a gain to some sort of precision laboratory project.

The DC version of Ohm's law and the DMM method gets you in the ballpark, but isn't a great way to set your gains imo.

Great is subjective, but adequate isn't. The DMM method is certainly adequate. Personally, I've been setting my gains by ear for years (and years), but a DMM and a test tone is all it takes for a total amateur to set a gain with plenty of accuracy to keep the speakers/subs from seeing excessive clipping.

It's better than just guessing, but leaves a lot to be desired.

If by "a lot" you actually mean "very little", then i guess it's "a lot".

HU volume to set gains depends on HU and telling OP to trust the 75% mark to be distortion free could lead to trouble depending on the head unit.

Not any head unit I've ever encountered, or heard of.

Besides -- so it clips a little...if you can hear at all, and the clipping is bad enough to present a problem at high volume it should be plainly audible. Just reset the gain with the volume a little lower -- problem solved.

This isn't rocket science.

Also depending on his electrical the voltage reading may be reflecting a square wave.

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I'm curious on how this might come about.

Everything else you suggested I agree with though and he shouldn't run into issues unless he plays tones or plays heavily bass boosted music. It's important for OP to know some of the possible pitfalls of using the DMM method and roll with those considerations in mind.

To summarize "possible pitfalls" -- essentially, none.