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AUDIO FORUMS >> General Discussion and Support >> Powered sub hook-up.
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Message started by MikeinMontana on 12/06/21 at 19:25:46

Title: Powered sub hook-up.
Post by MikeinMontana on 12/06/21 at 19:25:46

Hi. I was wondering (IF I even hook it up at all.) the best way to ad a powered sub to an SE84UFO2. The sub is an Hsu vtf-3. The very first, front firing version. It does have both high level ins/outs and low level inputs. The source for now will be an Oppo player using analog outs. Thanks much! ~Mike

Title: Re: Powered sub hook-up.
Post by Lin on 12/06/21 at 19:53:21

Do you use a preamp?

Speaker wire hook up can be:
2 pairs of wire from UFO, one pair to speakers and other pair to subwoofer speaker input
or speaker wire to speakers, then speaker wire from speakers to subwoofer
or speaker wire to subwoofer, then speaker wire to speakers.

With a preamp you can also split the rca outputs with a Y connector.

Title: Re: Powered sub hook-up.
Post by Dana on 12/06/21 at 20:32:45

I use the speaker output for my sub from my SE84UFO. It worked out pretty easy. I use banana plugs from the amp to the sub and then direct connect the bare wire to the holes in the terminals.

I don't use the high pass filter in the sub so the mains are still running full frequency but that allows the sub to be crossed over lower and requires very little gain from the sub amp.

Title: Re: Powered sub hook-up.
Post by Tony on 12/06/21 at 23:42:01

Hi Lin, NIce summary, easy to follow.

Is there a preferred option in terms of SQ or are they the same?

Title: Re: Powered sub hook-up.
Post by __Jon__ on 12/07/21 at 00:14:30

The only other issue with connecting subs, I believe, is that you can only use high / speaker level connections when the amp has a true not floating ground. And I don't believe that the SE84UFO has a true ground. Steve could obviously advise. In terms of sound quality, both options can sound good. Some prefer the speaker level connection to give the same "flavor" to the sub. I prefer it at least when going long distances vs an rca.

Title: Re: Powered sub hook-up.
Post by MikeinMontana on 12/07/21 at 02:35:45

Thanks for the replies all. Very helpful! Does hooking up from this amp to (high level) deter sound quality / reduce power? I am brand new to tube amps. Well, not even new yet...it's on order, so maybe in a year. [smiley=wink.gif] Other than my own recent 3 posts, I have read a lot of posts on this forum the past few months and am impressed at the know how and genuineness of members here. This just ads even more value to the Decware brand in my opinion. I appreciate this! After I get it together and learn more, I hope to be of some help here as well. ~Mike

Title: Re: Powered sub hook-up.
Post by Lin on 12/07/21 at 02:40:37

Tony wrote on 12/06/21 at 23:42:01:

Hi Lin, NIce summary, easy to follow.

Is there a preferred option in terms of SQ or are they the same?

Thanks
I can't say there is necessarily a gain in sq, but my brain tells me to run wires separately to both the speakers and the subs.
Probably doesn't matter one way or the other.

Title: Re: Powered sub hook-up.
Post by Lin on 12/07/21 at 02:48:01

Subwoofers can be hooked up to amps with a floating ground, just a matter of whether you use 1 or 2 subs.
2 subs (L&R) can be wired as normal.

Title: Re: Powered sub hook-up.
Post by petrov on 12/07/21 at 17:12:01

I have 2 SE84UFO25s with 2 active subs wired directly from the speaker terminals to the corresponding high level inputs of the subs. This method was recommended as ideal for sound quality and does not reduce power to the speakers. Sounds great!

Title: Re: Powered sub hook-up.
Post by Lin on 12/07/21 at 17:37:57

petrov wrote on 12/07/21 at 17:12:01:

8-)

Title: Re: Powered sub hook-up.
Post by Edsonic on 12/07/21 at 20:11:36

Sending separate lines from amp to speakers and amp to sub(s) is parallel connection. This is the cleaner way.

Run in series, separate loads add arithmetically, e.g. 8 + 8 + 8 = 24 ohms. Run in parallel the load is the 'reciprocal of the sum of the reciprocals' of the individual loads; 1/8 + 1/8 + 1/8 = 3/8, reciprocal is 8/3 = 2.7 ohms.

The common active subs for sale rarely give the input impedance for speaker level, but through many searches I found one claiming 100 ohms and two stating 1k ohms. From one amp channel's speaker out to one 8 ohm speaker and also to one sub input, connected separately (parallel), this would show 7.4 or 7.9 ohms, respectively, to the main amplifier. Hardly an imposition on the amp either way. But with series connection, who knows?

Aside that, there is issue of the main speaker driver's back EMF that would be translated to the sub if connected in series (amp ->speaker->sub).

So, as related above: "[Parallel] method was recommended as ideal for sound quality and does not reduce power to the speakers."

Title: Re: Powered sub hook-up.
Post by Lin on 12/08/21 at 03:28:24

Edsonic wrote on 12/07/21 at 20:11:36:

What do you mean by a series connection?
I have never heard of anyone connecting a powered subwoofer in series with the main speakers.