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hooking up sub to amp

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=40158
Printed Date: July 07, 2025 at 5:10 PM


Topic: hooking up sub to amp

Posted By: vbel
Subject: hooking up sub to amp
Date Posted: October 02, 2004 at 9:48 AM

I want temporarily to hook up my sub to my 4 channel amp by bridging (I guess) the rear channels together until my distribution block stuff arrives and then I will hook it up to a seperate amp.

The amp is a PG 8.0:4

4 ohm stereo 75x4
2 ohm stereo 125x4
4 ohm bridged 250x2

Minimum load stability: 2 ohm stereo/4 ohm bridged

The sub is 2 ohm. So how can I do this?


PS. I need it for tonight, so I hope someone can help me out fast. Thanks.



Replies:

Posted By: DYohn
Date Posted: October 02, 2004 at 9:58 AM
If your sub is SVC at 2-ohms, the only thing you could do is run it off ONE channel of the amp.  If it is DVC at 2-ohms, connect the coils in series for a 4-ohm load and connect that across two channels bridged.  Be sure to re-set your input gain for the new load.

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Posted By: vbel
Date Posted: October 02, 2004 at 10:14 AM
It is a DVC 4 ohm and is connected in parallel that gives me 2 ohm (that what I was told to do). Can I leave it in parallel (2 ohm) and run it bridged? 'Cause I already wired it in parallel and don't feel like redoing it. I will have then 4 ohm going into 2 ohm sub, is it ok?

And bridging...that means I take (+) from both rear outputs and connect them together to the (+) of the sub and do the same thing for (-)?




Posted By: DYohn
Date Posted: October 02, 2004 at 10:33 AM
No, it is not OK.  Your amp cannot handle a 2-ohm load if you bridge two channels.  The amp will go into protection or blow.  At 2-ohms use only one channel of the amp.  Your only other option is to re-wire the sub for 8-ohms and use the bridged output.

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Posted By: vbel
Date Posted: October 02, 2004 at 11:42 AM
Ok, I will just use 1 channel at 2 ohms. So all I have to do is take either rear channel and connect it to the sub? Will the amp adjust automatically for 2 ohm for that only 1 channel and the other channels will stay at 4 ohms? Or how does it work, I'm not sure...




Posted By: DYohn
Date Posted: October 02, 2004 at 12:09 PM

Yes, connect either channel to your sub.  activate the low-pass filter.  Leave the other channel un-used.  Amps don't care what load you connect them to and they do not 'adjust."  Any ohm load above their minimum loading is fine.  Connect too low an impedence (ohms) and too much current flows until they stop working.  The ratings on amplifiers simply indicate how they will perform based on specific speaker loadings.  But you can safely connect an amplifier to any load above it's minimum (in your case, 2-ohms per channel.)

Oh by the way, to "bridge" an amplifier, the connection is usually the + on one channel and the - on the other channel.  Check your owner's manual.  NEVER connect two outputs + or - to each other!



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Posted By: vbel
Date Posted: October 02, 2004 at 12:54 PM
Thanks for the explanation of the amp "adjustment" and "how to" bridge properly :) Good thing I asked...just in case sometime in the future I might have to bridge something... Manual by the way has nothing on how to bridge.


For the low-pass filter part, do I have to do it because the amp will feed my sub the whole frequency range (high notes like >1khz) or is it just 'cause my sub's range is upto 150 hz? Will it blow or anything if you give it more than 150 hz? And just for more information, my hu (pioneer) has seperate RCA outputs for subwoofers, so I will run another pair of RCA's and connect them to the rear channels of my 4ch amp, until I can hook up my mono amp. Is that seperate sub RCA output on hu is any different from the normal RCA outputs? Is it like filtered or something?




Posted By: DYohn
Date Posted: October 02, 2004 at 1:13 PM

On your Pacific Gold amp, look at the marking on the amplifier.  Under the connections for the rear output, it should be marked "Bridged" and indicate + under L+ and - under R-.  These are the two connections you would use for a mono bridged output.

You do not want to send high frequencies to your sub because you do not want to hear them from the sub.  It will waste power and sound bad. The sub output on your head should have a crossover setting in the head unit controls.  I suggest using 80Hz and see how it sounds.  Set the amplifier crossover switch to "BY."



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Posted By: vbel
Date Posted: October 02, 2004 at 1:22 PM
You're right, it does says "bridged" under the channel outputs. The hu has settings on it specifically for subs, so it makes sense now, why it got seperate sub rca's.

Thanks for all the help, I think I understand everything I need before I start the install.


PS. It's a Phoenix Gold amp, not Pacific...




Posted By: DYohn
Date Posted: October 02, 2004 at 1:37 PM
Oops, of course.  "Pacific Gold" is the brand of my favorite beef jerkey...  posted_image

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Posted By: forbidden
Date Posted: October 02, 2004 at 1:51 PM
Yes, get it straight, it's Kleenex Gold. posted_image

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Posted By: vbel
Date Posted: October 03, 2004 at 12:24 AM
Everything is done now, everything is working (that's great!). Now, this is my first time with a sub and is it supposed to sound so dull, muddy and simply like a mess of big, boomy noise?? I can't even tell the frequencies apart... Hm, I was thinking subwoofers would give me something else, but it is still pretty cool. Can't wait to give it 400 watts with a full signal, instead of the current 125 watts and only one channel.




Posted By: jeffchilcott
Date Posted: October 03, 2004 at 5:44 PM
sounds like you have the wrong enclouser size, or your low pass freq set wrong.    I would set the low pass on the radio to 120 or lower. also what type of enclosure are you running this sub in?

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Posted By: lophix
Date Posted: October 03, 2004 at 7:02 PM
sorry, not meaning to intrude or jack this thread, but i'm having sort of the same problem and I figure I might as well lay out what I have to work with and ask for the proper way to wire them up.

first: how do you wire a dual 4-ohm sub (rated at 600w r.m.s) on to a 4-channel amplifier rated at 75w x 4 @ 4-ohms (or 100w x 4 @ 2ohms)?

second: how do you wire a dual 2-ohm sub (rated at 600w r.m.s) onto a 4-channel amplifier rated at 75w x 4 @ 4-ohms (or 100w x 4 @ 2ohms)?

Other rms specs on the amps are:

200w x 2 @ 4-ohms bridged

75w x 4 @ 4ohms

By wiring, I mean which of the subs do I put in series, which in parallel, and what terminals on each amp should the connectors go for optimum/maximum output, and what mode should I leave each amp: 2-channel mode or 4-channel mode? There's also a 3channel mode but i don't think i need that. There isn't an option for mono.

Any help at all would be highly appreciated.

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Posted By: vbel
Date Posted: October 03, 2004 at 10:13 PM
After listening some more to my sub I think it is fine. The bass differs from song to song. The boomy bass usually is heard in rap songs, but other songs have a tighter, cleaner, more pleasurable bass. But I really thought I was gonna get a much clearer bass, but I guess there is no such thing. The enclosure is a sealed 11x11x13 for a 10 inch sub. The size is fine I think.








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