Confused! Sub 2 ohm vs 4 ohm [SOLVED]

My equipment is a single Rockford Fosgate 12" sub R2SD4-12 with Kenwood X802-5 amp.

Kenwood
https://www.kenwood.com/usa/car/excelon/x802-5/

Sub
https://rockfordfosgate.com/products/details/r2sd4-12/

My instructions sent by James (tech12volts) said to connect the sub at 2 ohm. However the Sub can supposedly accept 250W while the Amp will drive 500W at 2 ohms. If I use 4 ohms then the Amp can deliver 300W - seems like the latter is a better match. I emailed James and he confirmed that 4 ohms is indeed the best setting.

So I look at the Sub instructions, doesn't make sense. On the box it says the sub is a dual 4 ohm unit (assume because it's DVC = Dual Voice Coil.) Instructions show two sets of diagrams, one for 2 ohm and another for 4 home. Which one am I supposed to look at?

I want the sub to appear as a 4 ohm load to the Amp.

Thanks

 

You can’t get a 4 ohm load out of a 4 ohm DVC speaker. You’ll need to wire it up 2 ohm or get a different model.

 

So I read your post as James said both are right?
He sent the note saying 2 ohms but them emailed saying 4 ohms,is this correct?

Also look at the diagrams,they are identical and the only difference is the actual impedance of the speakers.

If you wire it for 4 ohms all will be just fine and that will be the lowest rightmost pic that I am seeing except that there is a problem with the math there too?
If the sub coils are really 4 ohms and you wire both coils in parallel as shown that will drop the load to 2 not 4 as is shown?

As long as you choose the higher impedance wiring the smoke should be safe in the amp and not release!

So I would wire as the sheet says for 4 ohms,should be more than enough power for the truck and also safer for the Amp.

 

Yeah, did a web search and found this page on James' website:
https://www.the12volt.com/caraudio/subwoofer-wiring-diagrams.asp?Q=1&I=42

So will the 2 ohm setting be "bad"? (I'm not an audiophile)

 

No I only have one sub, can't do the 2x diagrams

Doesn't seem like the right sub for the job IMO

 

You only have 1 sub bit 2 voice coils and in the pics and for 50 years doing this I calculate the load by the number of Voice Coils as they are the actual load,the diagram is confusing and somewhat misleading to say the least.

The real question is what is the impedance of each voice coil,without knowing that you can not correctly choose the right connection really.

On the other hand as long as you are too high it will be OK you just do not want to load the Amp with too low an impedance load.

 

You are correct that you have 2 4-ohm voice coils on your speaker. Your amp is 2 ohm stable so just wire it using the single sub, 2 ohm load diagram. And then just don’t crank the gain on the amp past halfway and you should be fine.

 

4 ohm dvc can only be wired in a 2 or 8 ohm configuration. In this case you want to wire it to a 2 ohm configuration. As long as the amp is 2 ohm stable, which it is, you’re fine. The ohm load has nothing to do with the quality of sound.

 

Sub-optimal (pun intended)

Seems like I'm up the creek without a paddle on this one. Searched all my local Best Buy stores for a different sub, they don't carry anything with a shallow mount, most are 5-6" deep. Right now I'm wishing I had the 2-ohm model of the same speaker instead.

Maybe I'll order from Amazon... get it tomorrow

 

Not really,as long as your amp is stable at 2 ohms and your load is at least 2 ohms which it looks like it is then you are fine with what you have.

The diagram is just confusing but I think you will be fine.

 

It’s better to over power a sub than under power it. Just don’t go more than a tick below half on the amp gain and let her eat.

 

So a 500W RMS amp driving a 250W RMS sub?

 

Yes

You just dont understand how the ratings work and this is not a factor in the real world with quality products.

Not trying to be insulting at all either but they way they rate this stuff is just silly mostly.

 

Maybe I don't understand but someone on the web does:
https://audiomention.com/2-ohm-vs-4-ohm-subwoofer/

And...
https://www.oznium.com/blog/2-ohm-vs-4-ohm/

 

You have a quality amp, so sound quality won’t be an issue with either load setting. But it’s your system and your money, do it how you want.

 

Ordered the 2ohm version of the same speaker, $70 shipped. Don't think I could sleep at night knowing that I'm off by a factor of two in the power ratings.

And I have two teenagers, I can just see it now. "Yes boys, I spent $2k on a new audio system. But see that piece of masking tape on the sub gain knob? Don't go past it or you'll blow the sub."

 

Install it like you were told by James. He does this for a living and knows what he is talking about. You will have no issues.

You are overthinking it. What did James tell you about the gain on your amp. The GAIN not to be confused with your little volume knob thing. That’s what sets your max levels, not the knob.

 

No talk about either of those. The amp itself has a ton of settings.

As for what you mentioned, they're likely both gain adjustments. One is meant to be a 'ceiling', the other is user adjustable on the fly (the 'knob')

 

To be honest you may be right. I’m not sure on your amp. That would be a good thing to research. But again, what James told you will be fine.

 

Masking tape on the sub level knob?
No offense but, you clearly don't what you're doing..
You'll set the sub gain on the amp, not by using KCA-RC01A wired remote control.
The KCA-RC01A just gives you a little leeway one way or the other.
You're not gonna blow the system turning up the remote knob if you set the amp gain correctly.
You need to do some reading on correctly setting amp gains.
Amp gains are inputs gains to match the output of the HU, for clarity and to avoid clipping, they aren't 'volume knobs'.

 

Lol. Why? You have exactly what you need to run the sub you have. You want to run it at 2 ohm. Not 4 ohm. You are thinking way to much into this. Once the gain is set on the amp, you’re not going to blow the sub with an external bass knob. That’s not how any of this works. Your speaker has a far greater chance of being damaged with the amp under powering it at 4 ohms.

 

Exactly. Some people need to just leave it to professionals. Or do a lottttt more research before they start taking things apart and hooking wires together. Next post from this guy is going to be, my truck won’t start, I’m blowing fuses, my truck is on fire, this system sounds like shit, etc etc.

 

Was talking about the 'knob' in the cabin

Ok, thanks for talking me off the cliff. I'll install what I have and adjust the amp gain accordingly (ie. not the 'knob')

 

^ Yes, run the sub at 2 ohms since the amp can do it.
I think the 2 ohm with more wattage will sound better than 4 ohm with lower wattage for the sub.

@BrakeDust you are overthinking this stuff.
I know, I do it all the time and usually my first idea was the one to go with..

At 2 ohms your sub is not going to OVERPOWER your other speakers.
More sub watts will give you cleaner sound not necessarily LOUDER sound.

 

But James lives in Georgia! Too far to drive.

 

The amp is rater for 2 ohm and so is the speaker because it has dual 4 ohm coils. Look at the wiring wizard on the fosgate speaker link. The top diagram is the same (1) speaker 2 ohm as the amp wiring you posted. (3rd image on the top from the left.) But, google wiring speakers and amps and ohms if you want confirmation. That amp and sub will handle 2 ohm all day long if you connect the wires right.

 

Thanks.

Some of you are saying "get a pro to do it" but I asked the pro himself and he told me to wire for 4 ohms. Not possible. (I'm going to chalk it up as a brain fart and leave it at that.) Cancelled the Amazon order, it's now installed @ 2 ohms per the diagrams.

 

You’ll be happy with this configuration

 

@BrakeDust
Just out of curiosity, are you running the stock or an aftermarket HU?

I know you stated you installed what you had and I think that's a good idea.
Let us know how it sounds..

Just my experience with this topic, in case someone later finds this thread:
Years ago I bought a JL Audio SB-T-TUNDB3/10TW3 Stealthbox, it contains 2 10TW3-D8 DVC 8 subs.
It is advertised as Wired for 2 ohm mono.
Running a Alpine PDX V9 4X 100 RMS / Sub is 500 RMS and 2 ohm capable.
It sounded like crap for years and I just lived with it.
It never had the umph and clarity a $1K sub enclosure should have.

I finally found the solution to fix it after researching it again last year;
I pulled the subs to find they wired the subs in series, that made the box 8 ohms.
I rewired the subs to parallel bringing it to 2 ohms.
It made all the difference in the world......
Lower ohms made it sound SO much better..


Link to a nice wiring chart..
Dual Voice Coil (DVC) Wiring Tutorial – JL Audio Help Center - Search Articles (zendesk.com)

And just to clarify:

When I stated 'I do it all the time' I wasn't talking down to you that I do car audio all the time, I don't.
I overthink everything all the time, I'm just like you......

 

Pretty much. What you set the gain at on the amp will be the max gain. The bass knob will not exceed that amount. Adjustments to the sub volume level on the head unit and the eq would effect the gain on the amp though.

Either way, theres nothing wrong or anything to worry about with the sub and amp combo you have. They are just fine. And on the comment you posted earlier about the sound quality/ware and tear on a 2ohm sub vs a 4 ohm sub, that really doesn't apply to car audio subs. Car audio subs are built to deal with heat and abuse. The sound quality difference would only be noticeable to someone who is trained to be able to hear such a tiny difference and thats in home audio. Car audio you will never hear that difference over the engine, the placement, ect of the sub woofer and road noise.

You're good man. Dont stress it.