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Connecting A Subwoofer Via the LFE Input


Peter P.
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I'm in the market for a new integrated amp to pair with my Heresy II's.

 

My SVS subwoofer manual implies that when connecting an A/V receiver/amp to the subwoofer using an A/V's single, LFE output and the subwoofer's LFE input, to turn the crossover control to maximum. I guess their thinking is the consumer would be using the source's subwoofer management capabilities.

 

I want to buy an integrated amp that has a single subwoofer output (not labeled LFE, just Subwoofer) with a fixed 90Hz low pass crossover. I want to use a lower frequency than that. It seems to me the crossover control on the subwoofer should still work with the single LFE input on the subwoofer (it has stereo inputs as well), up to the fixed 90Hz output of the amp. I'm hoping to cross over to the Heresy's in the 50-60Hz range.

 

What say the forum?

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If the integrated amp has a fixed LPF at 90Hz via the subwoofer output RCA, then I think you are stuck with that.  If your subwoofer has speaker terminals, you could bypass the integrated amps LPF by connecting to subwoofer via speaker level.

 

How about getting an integrated amp with L/R preouts and connect to your subwoofers inputs/s that way.  I do that with my Yamaha A-S1000, RSW-10d(when it worked), and RB-75s and with a subwoofer LPF at 60Hz and the results are seamless integration.  Tried it with my Heresy IIs and got the same results.

 

Bill

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I posed my question to SVS Customer Service and their reply is, I CAN use the single subwoofer output connection to the single LFE input on the subwoofer.

 

The only caveat is, the highest frequency being passed along that connection is what comes out of the amp's subwoofer output, in this case 90Hz. The crossover control on the amp will function up to 90Hz. I'd love to be able to control the high pass to my Heresy's but that's out of my price range. I currently have fixed 80Hz high pass filters on them, which is the best I can do- unless perhaps if I start a GoFundMe campaign. Hmmmm...😋

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  • 3 weeks later...
On 7/5/2021 at 4:32 PM, Peter P. said:

I posed my question to SVS Customer Service and their reply is, I CAN use the single subwoofer output connection to the single LFE input on the subwoofer.

 

Yeah you can, but, if you use a splitter or use two inputs you can get more out of the sub.  The problem with SVS is that their gain structure is very low, I've heard Klipsch subs are actually about 2.5 times hotter.  Basically what this means is that if you get an integrated amp with a weak subwoofer output, no way to boost it, and only use one input, the subwoofer level is often unsatisfactory.  Even if you do nothing but put a splitter on the inputs and use both it can help boost it up in this situation.  

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On 7/5/2021 at 4:32 PM, Peter P. said:

The only caveat is, the highest frequency being passed along that connection is what comes out of the amp's subwoofer output, in this case 90Hz. The crossover control on the amp will function up to 90Hz. I'd love to be able to control the high pass to my Heresy's but that's out of my price range. 

 

The _potential_ problem is that it doesn't really work like that.  Crossovers aren't a brick wall.  Content that is much higher than people realize comes through subs even with proper crossover points.  Low male voices and floor toms for example.  But, when you combine an internal subwoofer crossover with the internal integrated amp crossover, the slopes are additive, getting you closer to said brick wall.  It can sound funny to some, your upper harmonics in music can get robbed, all you get is the lower mushy stuff.  Car audio setups actually do use brick wall steep slopes like 24 db/octave at 65 hz I believe, maybe 60, somewhere close to that, but they do so because they take a stereo hip hop recording then boost the bass to high heavens.  Most home setups don't have super steep subwoofer slopes.  It could potentially work fine but it depends on how well you integrate it.  

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8 hours ago, Paducah Home Theater said:

 

The _potential_ problem ...

Thanks for both your replies! I have the new amp sitting on my coffee table, and the single RCA cable has arrived, I just have to get the motivation to unwire/rewire things!

 

I'll report back about the input level results and the crossover effects, if any, after I get motivated!

 

As an aside, the reason I bought the new amp is, every few years I wear out the on/off switch on my 28 year old amp and have to get it replaced. I'll get it replaced again and keep it as a backup. I hate to be without my music!

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Update: Today I installed my new amp, and replaced the speaker level wiring to the subwoofer with a 25ft. Monoprice cable. Since I listen mostly to FM radio, I turned on the new amp and things quickly went awry. My FM signal went to crap and I was picking up a lot of noise (not 60Hz hum) on the signal. When I would unplug the cable, the noise would go away.

 

Good thing I also bought a higher quality, Monoprice Onix Cable. I replaced the original cable with this one and the noise went away. This cable is double shielded. The original cable must have been transferring something to my FM antenna leads.

 

The only bad thing about the Onix cable is, it's not very flexible.

 

I can't tell any difference regarding the amp's fixed internal low pass subwoofer filter, as well as any level differences.

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