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Question about adding a powered sub....


lyeerluna
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I'm contemplating adding a powered sub to my 2 channel NAD amp and Forte 1 combo using the sub's speaker level inputs. Has anyone tried this and how does it sound? Any recommendations as far as brand of sub? Would love to stick with Klipsch, but don't have much money to spend. More concerned with bang for the buck sound quality-wise. Was even considering building one from Parts Express. Also considering just using a Parts Express sub amp and making my own cab or even making a Sonotube sub. Just really want to cover the really low end that the Forte's don't quite hit.(not putting them down-they're solid performers. Love 'em!). Any advice would be greatly appreciated! Thanks!

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To use the powered in, you simply go from the amp to the in jacks of the subs, then the out jacks to the speakers. The $150 Parts Express sub uses a fixed 180Hz high pass capacitor for the speakers, and the sub channel is variable using the knob. This may not be the best thing for you with Forte's. Any sub you buy should have a variable high pass filter, or you should open up the PE sub, and change the capacitor to about 80-100Hz.

If you wouldn't mind giving us a price range, there are some very good subs out there that could be recommended. The best thing to do, is use a pre-amp that has a sub out, which allows the pre-amp to determine the LFE (sub frequencies), and the HPF (Forte frequencies).

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Since you are using a stereo NAD amp, I assume you don't have any built in bass management. I wouldn't worry too much, as your fortes can handle a full-range signal without any problems; feed 'em directly from the NAD. Use a y-splitter from the NAD's pre-outs, one end back to the NAD's main ins, and the other to feed the sub a line level signal (to avoid amplifying the signal, then stepping it back down to line level and re-amplifying it; high level inputs on subs are only to be used if you can't send them a line-level signal, and with your NAD you can do so). You'll probably want to get a bigger sub that is adept at the deepest bass, and cross it over ~40hz using the sub's built in low pass filter. Something like a Rhythmic FV15. (I mention Rhythmic because they're tight and dry, very 'musical' subs, and seem to do well with high sensitivity mains. There are plenty of other options.)

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See the garage sale forum. The Klipsch RW-12D is on closeout at Newegg with free shipping for $330. It is a $1,200 sub! The promo code is in the garage sale listing.

There is an SVS BEAST in the Alert! area for $700. It is in IL, so shipping might be cost prohibitive. That sub is an ANIMAL!

BTW, subs do not "step up" and "step down" anything. They are a simple pass through with a high pass filter. In many cases, it is a simple capacitor.

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There is an SVS BEAST in the Alert! area for $700. It is in IL, so shipping might be cost prohibitive. That sub is an ANIMAL!

When I sold my +2, I put it on a pallet, drove to the airport and shipped it through Forwardair. It really wasn't very expensive.

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subs do not "step up" and "step down" anything

The high input impedance of the sub's amp only lets the tinitest bit of signal trickle through, which is what I was referring to. (Sorry, electronics terminology is not my area of expertise, but I'll take blood dyscrasias for $1000 any day.)

Every NAD stereo integrated I've seen or owned has pre-outs, and the newer ones have two sets of pre-outs. By using speaker level inputs to the sub you end up with the signal going through both amps, unnecessarily. Why do it if you don't have to?

Also, why route the signal through the sub's high-level pass through? It's not really necessary when using fortes. They're not some puny bookshelf speakers that need the coddling, and they probably have distortion specs in the bass that is on par with, possibly better than, many subs. They only need help in the lowest octave, that's it.

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subs do not "step up" and "step down" anything

The high input impedance of the sub's amp only lets the tinitest bit of signal trickle through, which is what I was referring to. (Sorry, electronics terminology is not my area of expertise, but I'll take blood dyscrasias for $1000 any day.)

Every NAD stereo integrated I've seen or owned has pre-outs, and the newer ones have two sets of pre-outs. By using speaker level inputs to the sub you end up with the signal going through both amps, unnecessarily. Why do it if you don't have to?

Also, why route the signal through the sub's high-level pass through? It's not really necessary when using fortes. They're not some puny bookshelf speakers that need the coddling, and they probably have distortion specs in the bass that is on par with, possibly better than, many subs. They only need help in the lowest octave, that's it.

Point taken. I was in a round about fashion saying that using the high level inputs adds another "way" to a speaker setup. If you have a 3 way speaker, and use the high level inputs and outputs, you are making it a 4 way. Sub, Bass, Mid/Horn, Tweeter

Not using the high levels, and not having bass management, will cause a certain amount of overlap, and hence a possible cancellation of those frequencies. It could also flatten the response and add gain to those overlapped frequencies, I suppose. In that case an EQ may be neccesitated to reduce them, so they don't overwelm.

I am kinda debating with myself as to which is better in this case. Thoughts?

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Wow, sorry for being so combative with my previous comment.

Not using the high levels, and not having bass management, will cause a certain amount of overlap

There is going to be overlap when the cutoff frequencies are set correctly (they're not brick wall filters). Fortes roll off pretty steeply at ~35hz. Even with it's low pass filter dialed back to 40 hz (a typical lowest possible setting on many subs), the sub will still have output extending to higher frequencies, depending on the slope of the filter. For much of the bass, 40-80hz, there will be three sources of bass, giving a good chance of smoother response. Without more capabilites than the NAD had, its a matter of level matching and room placement to get the smoothest response possible. While not ideal, that's what we're working with.

an EQ may be neccesitated to reduce them, so they don't overwelm.

To run subs with proper setup and control, even if only for two channel use, an AVR or pre-pro with dedicated bass management and room correction features would do the trick. I also seem to recall Velodyne and SVS selling outboard room-correction devices of some sort. Even with such control, I would first try running the fortes 'large' or full-range.

I personally don't don't really feel the need for subs with fortes for my exclusively music listening. (Listening to Prayer Meeting with Stanley Turrentine and Jimmy Smith right now...awesome album!...lots of deep, rumblin' organ bass.)

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I am kinda debating with myself as to which is better in this case. Thoughts?

Just about everyone's room is a bass-response nightmare and could benefit from room correction eq. (But even discussing it seems like some foray into the dark side, somehow against the whole ethos of retro Klipsch analog super hi-fi...oh, shit, these aren't the cozy confines of the two channel forum, this is technical questions! ...runs from the light...)

I have a well calibrated 2.1 system (non-Klipsch), which after much fussing and fighting, barely hangs with the fortes sans subs. To do actively managed and room-corrected bass, with subs up to the task, would require spending about three times what I spent on my fortes to do justice to the music.

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You're right, I totally forgot I had the pre-outs (I dont look at the back of my amp much). Can you explain to me why I need to use a y-splitter and feed half back into the amp? Forgive my ignorance, I've never used pre-outs before so this is new to me.

The only way the signal gets to the power amp section of your NAD is through the main inputs (it's not connected internally). You would only need to use a splitter if your NAD is of the older variety with just one set of pre-outs. Some of the newer ones have two sets, so a splitter isn't necessary. So, if yours is of the first variety, after turning it off and removing those horseshoe connectors, connect a couple y-splitters to your one set of pre-outs. Now you essentially have two sets of pre-outs to work with. With one leg feed the sub, and the other back to the main-ins (you won't be able to use those horseshoe jumpers, but that's unimportant, just as long as the signal gets to the main-ins somehow).

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First of all, thanks for your response. I have a newer NAD with no jumpers. It's a c315bee that they made about 3 or 4 years ago. It has the tape in/tape out RCA jacks. So, does that mean I would just run RCA's from the tape out straight to the powered sub?

In that case, forget what I said. Unlike it's larger brethren, I don't think the 315 has pre-outs/main-ins. I know the 325 and up do. I suppose I should have asked exactly which NAD you were using. Sorry for the confusion.[:$]

You can still connect your sub using the amplified/speaker level signal, as your original post asked about. It's your only option. It should work just as well for all practical purposes. I don't think you would be able to hear a difference wheather the sub was fed a line level or speaker level input.

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