# LFE question



## tcarcio (Jun 27, 2007)

If I connect multiple subs to my lfe out of my Pioneer Elite will it cause impedance problems. I have two connected now but I was thinking of splitting it one more time for my buttkickers. If this is a problem is there a fix. Thanks......:dontknow:


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## jerome (Apr 24, 2007)

No, it shouldn't be a problem. Your receiver LFE output is not driving your sub speakers directly, it's connected to the sub amps (LFE output is not a speaker output, it's more like a preamp output).

Use splitter cables or daisy chain your subwoofers, whatever is easier in your setup. Remember to switch OFF the filter on the first sub if you're going to daisy chain them, otherwise you could have some problems adjusting the phases during calibration. Read your user guides for more info on this:reading:


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## tcarcio (Jun 27, 2007)

Thanks, I have been getting mixed answers on this question from different people ranging from the impedance problem to a problem with mid bass frequency's. I was told also that I would need to run an audio signal amp to avoid any problems. I wont be daisy chaining the subs as I run a splitter out of the reciever and then dedicated cables to each sub. What I was thinking of doing is after the split at the reciever split one of those cables again and run the extra line to my buttkicker amp. Thanks for your response I really appreciate it.:wave:


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## jerome (Apr 24, 2007)

You're welcome ! 

I know some people who have split their LFE signal 4 or 5 times. The only problem is that the signal level is divided by two every time you split it. This means that the signal/noise ratio gets worse but I don't think that it is a real problem in practice.

Remember to recalibrate your system (receiver and subwoofers) after adding your second split. Then you're ready for some shaking experiences :T


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## tcarcio (Jun 27, 2007)

Great, I put up some acoustic panels and so when I am done putting it all back together I will re-cal. Thanks again,............:T


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## brucek (Apr 11, 2006)

> The only problem is that the signal level is divided by two every time you split it.


Not so, since the split signals are in parallel, they remain the same voltage, and since the current is extremely low as a result of the rather large impedance mismatch between the preamp output (typically 100 ohms) and the subs' power amp input (typically 20K to 50K), you may split the signal multiple times without a noticeable change in volume.

This is known as a voltage bridge connection where the preamp is acting as a voltage source and very little current is drawn. A perfect voltage source would have an output impedance of zero ohms at all frequencies. This would result in all the output voltage from the preamp being dropped across its load(s) with no voltage being lost to the output impedance of the pre amplifier. Two loads will divide the load impedance by two, but there is still a large mismatch, such that the voltage divider can still be ignored. You can split many times before it becomes significant. Anyway, there's an old rule of thumb that says, the input vs output impedance of a voltage bridge interface should be a minimum of 10:1

brucek


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## salvasol (Oct 31, 2006)

tcarcio said:


> If I connect multiple subs to my lfe out of my Pioneer Elite will it cause impedance problems. I have two connected now but I was thinking of splitting it one more time for my buttkickers. If this is a problem is there a fix. Thanks......:dontknow:


Don't worry!!! ... you won't have any problem with this set up :yes::yes:

I have two subs (Infinity and Velodyne) and also a buttkicker amp running two LFE's ... and guess what: NO PROBLEMS!!! :bigsmile::bigsmile: ... I used a "Y" to split the signal at the receiver, and another "Y" to split the signal again for one sub and the LFE amp ... :yes::yes:

On a side note: you may have a ground loop after connecting the buttkicker amp, in that case just get a ground isolator (http://www.radioshack.com/search/index.jsp?kwCatId=&kw=ground isolator&kw=Ground+isolator ) to solve the problem (that's what I did) :T:T


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## tcarcio (Jun 27, 2007)

I did get the ground loop problem but I did exactly what you suggested. I think what I have decided to do is leave the splitter coming out of my reciever as is and run another cable from the lfe out on my A5-350 to the buttkicker amp and I should be good to go.


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## salvasol (Oct 31, 2006)

tcarcio said:


> I did get the ground loop problem but I did exactly what you suggested. I think what I have decided to do is leave the splitter coming out of my reciever as is and run another cable from the lfe out on my A5-350 to the buttkicker amp and I should be good to go.


:T :T :T


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