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Old 29th August 2009, 06:49 PM   #1
Dylanl is offline Dylanl  United States
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Default Please help with Dual SUB Setup!

Ok I set everthing up from the advice I recieved here on the forum. I am using a Denon AVR4800 receiver and running the LFE out split to the RCA to 1/4" inputs of a Behinger EP4000 (2 x 750 into 4 ohms). I am then running speaker cables to the passive subwoofers. With everything cranked up to max ( Denon LFE +12 and Behringer gain to max ) I still have very little coming out of the subs.
Also, the input light on the Behringer amp shows little to no signal coming into the amp and only turns on on heavy heavy bass.

I had an extra preamp around so I tried it and sent the Denon signal to that 1st then sent the signal to the Behringer. After setting the pre amp to max I now have sufficient sub output. I am however now getting Hum.

Is there an easy fix for this problem or should I send this amp back for a different amp that would match gains better?? Maybe a plate amp? Are they designed to match Home Audio better? Problem is I need the power for the dual subs!

FYI my speakers are High efficiency being Klipsch and vintage Altec.
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Old 29th August 2009, 06:58 PM   #2
Glowbug is offline Glowbug  United States
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Do you have a crossover on the Denon set somewhere it shouldn't be? Almost sounds like you have a HPF set too high...
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Old 29th August 2009, 07:32 PM   #3
Dylanl is offline Dylanl  United States
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No they are set correct.

SO i did this. I ran the leads out of my other SVS plate amp to my new passive subs and WOW now the bass is overpowering. I have to have a mismatch in the signal being recieved somehow? Same signal sent to the plate amp as to the Behringer.
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Old 30th August 2009, 12:39 AM   #4
Glowbug is offline Glowbug  United States
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I'd try the Behringer on its own, with another source...try to isolate any problems.
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Old 2nd September 2009, 09:41 AM   #5
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You are missing a subwoofer preamp/crossover! Plate amps have this built in, but with an external power amp you need to increase the gain.
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Old 3rd September 2009, 09:41 PM   #6
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EP4000 has 34dB gain (50x) according to spec.
Even a weak signal should produce a LOT of sound.

Signal indicators are usually 1W into 8ohm (2.83V) (not perfectly sure though but it makes sense)
That would mean 0.056V on the input with that gain.
So it should be fine without a preamp even if it won't be maxed at line level. (around 150W into 8ohm with 0.7V)

Unless I got it wrong some how.
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Old 4th September 2009, 05:22 AM   #7
Dylanl is offline Dylanl  United States
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Quote:
Originally Posted by paulspencer View Post
You are missing a subwoofer preamp/crossover! Plate amps have this built in, but with an external power amp you need to increase the gain.
I think you are dead RIGHT and everthing pointed to that!

Ok so i got a ebtech line level shifter
http://www.ebtechaudio.com/lls-2des.html and now I have more than enough head room. I was told by a pro audio gear head that the problem I was having is common and it takes the signal from -10db to +4 and makes unbalanced cables balanced. trying to run Pro gear from HT gear sometimes works and sometimes not. I am now running 1 line from the LFE out to the ebtech in, Ebtech to the Behringer and speaker wires to the dual subs.

Question: I also have a symetricx parametric 5 band EQ unit. http://media.musicalplanet.com/pdf/SYM014.PDF How could I use this in line to make these dual subs the best they can be?
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