Subwoofer LFE adjustment questions...

**Darren** · **07-27-06, 11:03 AM**

Questions on Adjusting Subwoofer Signal
« Thread Started on Today at 8:56am »

Hi Guys,

I'm looking for a little clarity on adjusting the signal properly starting from the receiver and ending at the amp.

Currently I have my AV receiver LFE level at -10, my mains are in the neighborhood of -6 on average. I have my EP2500 set at about 12:00. At these settings the amp is clipping on scenes like Star Wars Attack of the Clones Scene 1 with the ship fly by etc... Also on LOTR FOTR scene 1 ring drop. I would think this amp should be able to be turned up significantly more than 12:00 at these settings before clipping. When it does clip the drivers definately let you know, they fall flat on their face.

4 RL-P 15's bridged mono for 4ohm load

How are you configured? Does my configuration and experience sound normal?

**Josuah** · **07-27-06, 11:10 AM**

The amp's gain is how much it adds to the input signal, not the maximum volume it will output. So if the gain is set at max, but you feed it a tiny signal, it will not play loud, and if the gain is set to min, and it feed it a huge signal, it will play loud.

Sounds like you just need more subwoofer for your listening levels. What's the SPL of the sub at your listening position at those scenes where you are having problems?

**Darren** · **07-27-06, 11:13 AM**

He he, 118db give or take... I'm just trying to tune my maximum output so I don't exceed the drivers capability and the amp capability...basically tuning for worst case LFE scenario

At normal HT listening levels I'd say the peaks are at 105db but an unexpectedly over-dynamic scene can clip the amp and the drivers still have much more headroom. That's what I'm a little worreid about. I want to minimize the possibility of excessive clipping at my normal listening levels.

I have four RL-P 15's with 1,500 watts in an IB.

It sounds like I just have a strong signal going to the amp through the BFD then... this is good, I need to learn about how the signal is treated and amplfied. I've always just went on what I was told without learning why...now I'm wanting to learn why.

**bobgpsr** · **07-27-06, 12:17 PM**

With pro amps IME you want to have their input gain levels cranked all the way clockwise. Big problems otherwise happen with the AVR clipping its LFE output. Unless you are trying to compensate for a SACD/DVD-A players' analog sub output level, I would set the AVR's LFE at 0 not -10.

I don't have a Behringer, but rather a Mackie M1400 and to get the input drive right I had to get an ART Cleanbox to get nominal +4 dBu pro level adequate drive. Home audio uses -10 dBV for nominal line levels.

Bob

**Darren** · **07-27-06, 12:20 PM**

I'm not sure I am understanding completely...

My LFE output in the speaker level settings is set to -10, if I move it to 0 the amp will be getting a HUGELY increased signal, wouldn't that really clip the amp? Then if I set the amp all the way clockwise I'd be opening that signal all the way up which would make the situation worse right? Am I not thinking correclty?

**bobgpsr** · **07-27-06, 12:27 PM**

I'm thinking of my Yamaha's case where it has both an LFE level (0 to -10dB) and a separate subwoofer channel level adjustment (with the other channel levels). What is your AVR again?

The LFE level that I am talking about is really only used for digital connections using DD or DTS and is not used for multichannel 5.1/7.1 analog inputs. Sorry for the confusion!

Bob

**Darren** · **07-27-06, 12:34 PM**

I have an Onkyo TX-DS777 AV receiver. I'm using the LFE out 5.1. I have the LFE level adjustment within the speaker level settings at -10 (can be adjusted up and down in 1db increments above and below 0). I use this to set the subwoofer level in balance with the speakers. The signal reaching my BFD is strong but the BFD never goes out of the green range, the EP2500 will clip on extremely dynamic scenes when set at 12:00 in this configuration. When I say clip I don't mean a flicker, I mean solidly lit for more than a second.

I might have it a little hot but I don't believe it should be clipping at these settings when listening at normal HT levels... Not sure what db I listen at, I have it turned up pretty well for HT listening.

**bobgpsr** · **07-27-06, 12:52 PM**

Oh yeah -- the BFD input level meter! Hmmm sounds like your AVR sub line level drive is OK then. I've read where the Behringer amps have a input that can handle home audio line levels (unlike other pro amps).

So the clipping is in the EP2500. IME I've just gotten occassional brief flickers of the red clipping LEDs on my Mackie for extreme bass scenes -- WOTW tripods, opening of Serenity, 1812 cannons, etc.
I'm driving a single 15" Tumult that is rated for 1000W at the voice coil with the Mackie bridged to output 1400W into 4 ohms. And I am able to bottom my sub when I run +10 dB over reference. So I set the Mackie's high pass rumble filter at ~18Hz and try to stay at reference level. Using it in a big 3000+ cubic ft basement room

Seems like your EP2500 driving 4 ohms is running out of oomfp before your 4 RL-P15's.

Did you think of/consider wiring your array to 8 ohms instead? Much easier for the amp to drive -- but half the drive current pulled from the amp.

Bob

**Darren** · **07-27-06, 01:02 PM**

Hm, I just did some calculations and I don't know where I came up with 4ohms... I have DVC 4 ohm drivers so the only possibilities for Bridged mono are 8ohms. So I'm actually running 8ohms bridged mono for 1,300 watts or 325 watts per driver.

I could 4 ohm stereo or 2 ohm stereo. I'm a little afraid of 2ohm stereo even though Behringer states it can handle it.

At 8ohms bridged mono I'm seeing 1,300 watts or 325 per driver.

At 4 ohms stereo I'd also be seeing about 750 watts per channel or 325 per driver

At 2 ohms stereo I'd be seeing 1,200 watts per channel or 600 per driver

I'm not sure if going 4 ohms stereo would be better or not. I could try 2 ohms but like I said... that seems like it would be harder on the amp even in stereo.

**bobgpsr** · **07-27-06, 01:08 PM**

Sorry to ask -- but just had to

. Is your "bridged mono" connection using the two + outputs of the EP2500 --- I'll bet you are --- but I have seen some set the bridge switch and not changed the speaker connections to the bridged configuration. Just a thought.

Bob

**Darren** · **07-27-06, 01:09 PM**

Yeah, I'm using just the two red outputs in the middle.

**bobgpsr** · **07-27-06, 01:11 PM**

I'd try 4 ohm stereo. It is simple and easy. Plus the extra wires needed might give you a lower IR drop/better damping

But it not likely to solve the clipping problem.

Bob

**Darren** · **07-27-06, 01:21 PM**

Yeah, it will be easy, I have both sets of wires coming to the amp right now and just need to separate the mono connection to stereo and flip the dip switches etc... I don't even have to get in the attic for that. I have pairs of drivers at 4 ohms on separate leads that come to the amp and I then put those leads in series and into the amp.

I'll have to do that when I get home from work.

**bobgpsr** · **07-27-06, 01:30 PM**

RL-P15 dual 4 ohm (D4)? or RL-P15 dual 2 ohm (D2)? Either way with four drivers I don't see how you don't have all possibilities (2, 4, 8, 16) ohms with the right series/parallel combinations.

Bob

**Darren** · **07-27-06, 01:32 PM**

Dual 4 ohm... Not sure how I could get 4 ohm bridged mono though. I don't think it's possible.

I'm beginning to wonder if my "normal" level for HT might be a bit above normal too

I'll take measurement so we have an idea of what db level I'm having the issue at.

**Sonnie** · **07-27-06, 01:44 PM**

With a dual 4 you end up with 2 or 8

... with 2 you get 1, 4 or 16

... with 4 you get .5, 2, 8, or 32

... I don't see a way to get to 4 with 4.

**Darren** · **07-27-06, 01:47 PM**

Those are what I came up with too Sonnie.

**bobgpsr** · **07-27-06, 01:55 PM**

Only use one 4 ohm coil on each driver? Have pairs of drivers at 8 ohms. Try 8 ohm stereo which would be the easiest load on the amp since your amp is running out of gas before your drivers.

Bob

**Darren** · **07-27-06, 01:57 PM**

Ah, but that would change the damping of the driver right? I could do that though but the amp really shouldn't be running out of steam so I'd rather deal with that end but I'll try the other wiring options.

**bobgpsr** · **07-27-06, 02:08 PM**

The amp might well be running out of current capability at low freqs. It may meet its specs at 1 kHz OK though. I seem to recall that it was a design copy of a QSC amp although the QSC had a much bigger power transformer. IIRC this was a criticism by QSC's Bob Lee. The QSC does cost a lot more though.

Bob

**Darren** · **07-27-06, 02:10 PM**

Bigger transformer? I can't imagine a bigger one than what is in this thing

It must be 7" in diameter. Interesting observation though. Others are using this amp successfully though in similar setups. I might just be expecting too much from it.

**bobgpsr** · **07-27-06, 02:11 PM**

Quote:

Darren wrote:

...Ah, but that would change the damping of the driver right?...

It gives you the option of changing the drivers Q factor - via shorts or loads on the unused coil. IIRC leaving the coil open does not change much. Adire has a tech paper on it.

Bob

Advertisement