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AUDIO FORUMS >> General Discussion and Support >> Can I use sub + two speakers with a SE84UFO25?
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Message started by Mr. Toy on 08/17/25 at 18:50:58

Title: Can I use sub + two speakers with a SE84UFO25?
Post by Mr. Toy on 08/17/25 at 18:50:58

Hi everyone,

The SE84UFO25 has posts for two speakers. Could I use that to power three speakers? Could I power my two main speakers (99dB sensitivity) and add a powered sub to the mix without using a pre-amp? My powered sub only has one RCA input by the way, not two.

If I were compelled to do this, how might I make that work? Connect my left and right speakers as usual. Then, for example, link the subwoofer's positive connection to the left speaker's positive post, and the negative subwoofer connection to the right speaker's negative post via an RCA "Y" connector. OR vice versa?

If that is how I would accomplish this, does it matter which posts I pick, or are they the same? Is there an advantage to doing it one way over another?

I'm curious if it is possible to temporarily use this amp without a pre-amp or a stremer with a "sub out" built in. I couldn't find an answer to this question for this particular amp, so I apologize if it's already been addressed. [smiley=beer.gif]

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by CAJames on 08/17/25 at 19:20:45

Quote:

Posted by: Mr. Toy Posted on: Today at 10:50:58

...The SE84UFO25 has posts for two speakers. Could I use that to power three speakers? Could I power my two main speakers (99dB sensitivity) and add a powered sub to the mix without using a pre-amp? My powered sub only has one RCA input by the way, not two.

Subwoofers aren't my thing, so other posters may be more helpful, but if your sub has an RCA input it sounds to me like it needs a line level input (from a preamp) rather than a speaker level input (from the speaker posts). It might help if you shared the model you have.

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by Donnie on 08/18/25 at 02:30:03

Mr. Toy,

Short answer, NO.

The RCA input on your sub amp is a "low level" input. It can handle around 2 volts or so input voltages. The volume of the amps output comes from the varying of the input voltages from your source (preamp, or maybe an output from a digital source with a digital volume).
So basically your sub amp is getting very small amounts of voltage that it amplifies to output more voltage.

Now if your sub amp had "high level inputs" (sometimes they look like 5 way binding posts) you would be able to take output from the speaker binding posts.

The reason is that the voltages from your speaker outputs are several times more voltage than the 2 volts that a low level input operates at.
If things didn't immediately blow up, your sub would be running wide open all of the time.

I hope that this makes sense.

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by MikeinMontana on 08/21/25 at 22:41:10

I use speaker level inputs on my old powered sub with the zen amp and it works perfectly. Apparently, your sub only uses rca's? It's unfortunate that many company's are doing away with speaker level connections on powered subwoofers. I am not familiar with using an rca to speaker level adapter....

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by 1stwattlife on 08/23/25 at 00:41:19

Long story short... YES, BUT...

Post the model of your sub, or a picture of its inputs... I am assuming it is self powered... but let's figure out what you are actually working with :)

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by Mr. Toy on 08/23/25 at 18:45:37

Thanks, everyone! I don’t need it! My UFO25 showed up earlier this week, and I don’t have to fuss with a sub or a preamp. :D

Short version: It’s a room problem.

Long version: I used to run a sub behind my listening chair just to sneak a little bass into the middle of the room, thanks to my living room’s ‘special’ layout. The real culprit is a fireplace that juts a foot into the room, parked right between my Klipsch Fortes. Since the Fortes have rear-firing passive radiators (and don’t quite hug the corners of the room), the fireplace ends up trapping the bass and stealing the articulation from the listening chair. If I stand up and walk to the sides of the room, suddenly the bass goes from shy to unruly.

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by 1stwattlife on 08/23/25 at 19:25:36

Room issue are such a bear... but, once you find it, you can tame it! So glad you found a root issue! It frustrates me when I find out I just spent time and energy focusing on sympathetic issues... good luck!

Title: Re: Can I use sub + two speakers with a SE84UFO25?
Post by MikeinMontana on 08/23/25 at 19:37:36

Bass is so hard to deal with in certain rooms/setups. Took me years to get some bass notes to sound 'pretty good' in our large, cathedral ceiling, windows everywhere room. I am not talking about boom bass. A no go to tolerate.. Friggen ridiculous... Best of luck and keep at it! [smiley=icqlite20.png]

~1stwatt on target