2 or 4 Ohm amp/8 Ohm Sub

I hav e been trying to find info on hooking a DVC sub in an 8 Ohm configuration to a 4Ohm / 2Ohm stable amp.

Are there any pros, cons, dangers, and how does it change the amps performance?

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"In this bright future you cant forget your past"

when you have 8 ohms, there is more resistance than there would be if there was only 4. your sub will not be getting as much power as it was if it was only 2 or 4 ohms. if it is dual voice coil, you can hook it up to be 4 ohms and that is the way that i would do it.

  I have a 660 rms power acoustik fahrenheit amp and a 600W rms15" volfenhag sub in a 5.25 cu. ft. wedge box.

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"In this bright future you cant forget your past"

with a dvc subwoofer think of it as two 4 ohm subs just hook it up like you were hooking up 2 4 ohm subwoofers

yeah, just put the positive and negatives of each coil in the same spot on the amp

what's the model number of the amp?

The reason I asked is if it is a mono amp then you could wire the sub to 2ohms safely like this.


But if it is a 2+ channel amp then we'll need to figure out something else because most 2+ channel amps are only 2ohm stable Stereo and 4ohm stable Mono. Hard thing to do with a single 4ohm DVC (unless you want to risk independant wiring).

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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FARENHEIT Q21500

1500 WATT Amplifier

Heres the model # and specs on the amp. and the sub is a dvc but with each voice coil @ 300w rms I should be fine just giong with the plain jane 4ohm config. right?

Specifications

2 X 400 Watts @ 2Ohms RMS

2 X 330 Watts @ 4Ohms RMS

1500 Watts Max Bridged

Freq Response 10 - 30,000 Hz

THD: 0.02% S/N Ratio;: 97dB

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"In this bright future you cant forget your past"

Your amp is listed as being 2ohm Stereo stable, but not 2ohm Mono stable. Which means you can either wire each voice coil independently to its own channel at a 4ohm load on each channel giving apx 330RMS to each coil (which is not recommended though, read more here on the dangers of independent wiring), or you can wire the sub into a bridged 8ohm load which will give you apx 400RMS to the entire sub.

IMO, With your current equipment you would be better off (and safer) wiring to the bridged 8ohm load for 400watts. You would be underpowering the sub, but you wouldn't run the risk of it tearing it apart by using different input signals. Here's how you would wire it to an 8ohm load...


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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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Nestamarley, as wvsquirrel wrote, wiring the VC's separately is absolutely the last thing you should do...

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D148L0

  by underpowering the sub with the bridged config. how can i control overworking/cliping  the amp? just reduce the gain at the amp, or just watch the sub volume from my head unit? I got this amp because I thought it was properly matched to feed this sub, but it looks like I may have screwed the pooch on that. 

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"In this bright future you cant forget your past"

You wont be underpowering the sub too bad (somewhere between 100 and 200 watts), I've seen people do worse (like using a 200 watt amp to run a 1000RMS sub!). Adjust your gains as normal (gains all the way down, 3/4 volume on the headunit, then turn the gains up until you hear distortion, then turn them down a fraction of a turn), and you should be fine.

Don't feel bad. You matched the RMS pretty good, but you would have been better off getting a mono class D amp that was stable at 2ohms. Is it possible for you to return/exchange the amp?

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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  It may be possible for me to swap out amps, I would have to see. So if that was an option, I would need an amp that was 600 X 1 @ 2 Ohms Rms, right?

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"In this bright future you cant forget your past"

That's correct. Since you have a 4ohm DVC, you could wire it in parallel (like the pic I posted at the start of the thread) for a 2ohm total load on a 600 x 1 @ 2ohms amp. The JBL BP600.1 is an excellent amp from what I've read, and would do you quite nicely. Not sure of the $'s though.

Make sure when you choose an amp to look at the 12volt power (RMS) rating. Most companies are using 14.4volts to rate their amps now, and you have to do a little digging to find what you would actually get at 12volts. Based on the specs I've seen lately, a quick quess estimate is to subtract apx 50 to 100 watts from the 14.4volt rating to get the apx 12volt specs.

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com

  Hey, the company I ordered the amp from jacked up and sent me the Q21800 which is an 1800 max. This means Ive got a bit mor e power to play with. Also, my head unit has a mono sub out (split for left and right feed) so if I hook it up with each VC to to its own channel of the amp how would that cause problems if the siginal is the exact same on both sides of the amp? 

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"In this bright future you cant forget your past"

Nestamarley, check this tutorial from JL about DVC wiring.... thex explain in detail why it should not be done... hope it's useful man: https://www.jlaudio.com/tutorials/dvc/diffsignals.html

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D148L0

If you have a DMM, test the RCA outputs. It's very unlikely that they are exactly the same, but you never know. Even if the headunit is producing 2 exact signals, you still have the amp to worry about. Each channel has it's own gain controls, filters, etc. which is why it's not recommended for a 2+ channel amp. What's the make/model of the headunit?

Assuming the signal is the same from both channels of the headunit (and truely mono not stereo), and the amp is set up exactly the same for both channels, the specs I found on that amp vary. One site referenced 200 x 2 @ 4ohms, and another referenced 370 x 2 @ 4ohms. Power Acoustik doesn't even list that amp anymore, and most places I've found have it listed as discontinued.

If it would be possible to get another 4ohm DVC sub to match your current one, then you would be better off (you could wire in series/parallel for a bridged 4ohm load and get apx 960 x 1 @ 4ohms mono)

You still another option though.
I've found some sites that list that amp as being 2ohm mono stable. It highly unlikely, but possible. Turn the gains down and hook the sub up like this...

I said turn the gains down because you would get apx. 960 watts to the sub (which has an RMS of 600 watts). Adjust the gains like you normally would at that point. If the amp goes into protect mode or starts shutting off, then you know it isn't 2ohm mono stable and you're back to square one.

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com

  I think you guys got me in the right direction. I'm gonna try to get this thing hooked up and see how it works, I will keep you posted as to my results.  you have been great, love this site.

  By the way, what site was it that you found someone describing this amp as 2Ohm mono stable? I didnt find that in the spec sheet that came with the amp, but maybe they know somthing that I dont.

 

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"In this bright future you cant forget your past"

I wouldn't trust it too much, but here's the link.

It shouldn't hurt the amp or sub to at least try a 2ohm bridge. Just keep the gains turned down while you try it. I normally don't recommend trying an uncertain 2ohm bridge unless, like in your case, you already have the equipment on hand and aren't still waiting to buy something.

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com