# Setting up two subwoofers with BFD



## bittermelon (Apr 19, 2006)

I haven't found much information on this topic. If you want to set two different sets of filters,etc for two different subs, you can load the settings into the left and right channels. How do you send the right settings to the right sub? Do you have to use both input 1 and 2 and output 1 and 2? If so, which one corresponds to the left channel and which one to the right channel? Or could you use a stereo 1/4 plug on the output and have a separate left and right channel that corresponds to the filters? I'm trying to set up a HSU VTF-2 MKIII and use my Athena P4000 nearfield for more of a buttkicker type of sub. I have set the low pass filter on the Athena itself at 60Hz and, but I would like to cut one peak around 35Hz. The HSU has another profile when I measured it by itself. Thanks for your help.


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## Sonnie (Apr 11, 2006)

From the BFD Guide...


> Output/Input 1 = Engine L or the Left Channel, effects all "L" labeled LED's on the front of the unit.
> Output/Input 2 = Engine R or the Right Channel, effects all "R" labeled LED's on the front of the unit.
> 
> You will need either ¼ inch or XLR type connectors on your cables. If you already have RCA type connectors on your sub cable(s), you can pick up a couple of RCA to ¼ inch adapters at Radio Shack for temporary use until you can order some RCA to ¼ inch cables. The adaptors are cheaply made and they create another connection point for your signal to travel through, so I recommend purchasing some better complete cables.
> ...


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## bittermelon (Apr 19, 2006)

Thanks, Sonny

I actually read (one of the rare times) the manual today and couldn't find that info, thus the post. Your BFD guide and the REW guide was all I needed to get my first sub set up, but now I want to set up two, I needed to pull out the BFD manual. Thanks for the quick reply.


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## Otto (May 18, 2006)

Hi bittermelon,

You asked:



> Or could you use a stereo 1/4 plug on the output and have a separate left and right channel that corresponds to the filters?


If you are using a stereo 1/4" plug, it's still a single audio signal, but in a "balanced" form. There's no way to get L and R signals on a single cable when using this type of system. You'll have to use both halves of the BFD to EQ two separate signals.

Why Behringer decided to name them "Input/Output 1" in one place and "Engine L" in another is beyond my ability to understand.


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## bittermelon (Apr 19, 2006)

From the BFD Guide:
(NOTE: If both the "ENGINE L" and "ENGINE R" buttons are lit, this is "COUPLE MODE" and is okay, but you will be entering the filters for both left and right INPUTS/OUTPUTS if both buttons are lit. Initially both will be lit. Press both buttons simultaneously and "ENGINE L" button will be lit with the "ENGINE R" button not lit. You can now press either to activate or deactivate that channel. If you do cut off one channel, make sure the correct channel you are connected to, has the button lit. Warning: If you don't like lights then make sure you cut off the channel you are not using, this will eliminate LED's lighting up for that channel on the display.)

This has been confusing for some who use two subs and want to create different filters for each sub. Here is the section from the manual on coupling:

*Use the ENGINE L key to select the left audio channel.

*Use the ENGINE R key to select the right audio channel. If you wish to process the left and right audio channels simultaneously (COUPLE mode), press both ENGINE keys together. In couple mode both engine LEDs light up. Whenever you edit one of the two audio channels and then switch to couple mode, the parameters of the active channel will be copied to the other; i.e. if you press ENGINE L before ENGINE R, left will be copied to right.

I haven't actually made the connections and tested this, but as I understand it, by pressing both ENGINE buttons at the same time, both buttons with either light up or go out. When the buttons are lit by the pressing of both buttons at the same time you are then in COUPLE mode. Pressing both buttons at the same time again will turn off COUPLE mode and neither button will be lit. To make each channel work independently you will press both buttons to make them light, but don't press both at the same time.

You have to press them both down twice to unlight one then set the parameter for that sub by ensuring the correct Engine is lit. I get that part and have set each Engine L and R independently. Once they are set how do you activate both Engines? You can light either channel, but if you press both of them simultaneously, it will copy the filter settings from the active (lit) channel to the unlit channel? For two subs with different settings, is it not necessary to have each Engine lights on, the filters are on regardless if it's coupled? If they both need to be lit(coupled), then how does one get both on without it copying over the settings from the lit Engine? 
I don't if the Engine R filters (currently unlit - settings for the Athena) are working but I'm getting a smoother response than when I ran them both out of one channel and only using the HSU's settings :dunno: 

Does the BFD have to run in coupled mode to have the filters from both engines working if so how do you activate them both after you set them individually?


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## Sonnie (Apr 11, 2006)

I'm not at my BFD at this moment and I've not ever used but one engine, but you should be able to simply press each button. Once you enter your filters for both engines, are both buttons not lit? It seems like I remember that the engine LED must be lit for the filters to take, no?


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## brucek (Apr 11, 2006)

When both engine lights are on, you're in couple mode and one channel reflects the same filters as the other channel.

When one light is on alone, you are able to set the filters of that specific engine. 
When the other light is on alone, you are able to set the filters of that specific engine.

The single lights on only show which engines filters you are messing with. They're both active though.

brucek


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## Otto (May 18, 2006)

Hi bittermelon,

I used to use a BFD to EQ two separate subs. I agree that there are a few things that are confusing about the BFD, and this is one of them. Before I start here, I want to clarify about the different lights:


The main in/out light at the top right will, in general, turn processing on or off
Each channel has a button with a green light on it to select that channel
The 12 red lights, per channel, indicate which of the available filters you have programmed for that channel

Note: I may use the words "channel" and "engine" interchangably.

When I started doing this, I didn't get it either. I understood that the "couple" mode copies the filters of the first button you push to the other channel; that's pretty straightforward. Since I was trying EQ two subs differently, why would I want that, though? Right? I think when you do that, the red lights of the "copy to" location will change to match that of the other. If you are using 3 filters in Engine 1 and seven filters on Engine 2, and you "couple" Engine 1 to Engine 2 (i.e., temporarily "copy" 1 to 2 -- I say "temporarily" because you can de-couple them by pressing both buttons and still have your previous filters), then Engine 2 will now only show three red lights, which is the same at Engine 1, the one you just copied from. I'm not at home right now, so all this is coming from memory.

Still, I really wanted to have both of the "channel on" lights (#2 on my list above) so that I could be sure I was processing both channels. Never happened (well, unless I was in "couple" mode, which isn't what I wanted).

What I did was generated and loaded my filters for Ch 1 and Ch 2. Whatever they came out to be. Then, I selected either channel, doesn't matter -- just don't do the "couple" thing. Make sure general processing is "in" (#1 on my list). As long as you have filters for Ch 1 and Ch 2, you are processing both independently.

Here's how I verified it: 

Unplug Sub #2
EQ Sub #1, assign it to Ch 1, set filters and remeasure. You should get good results from REW.
Unplug Sub # 1
EQ Sub #2, assign it to Ch 2, set filters and remeasure. You should be good.
Then, all else being equal, measure either sub independently and you should still get good results.

That tells you that

you are still processing each channel and 
one set of filters didn't screw up the other

Note that if you turn off general processing (#1 in my first list), neither sub will be EQd. You should be able to hear and measure this independently as well.

Either way, you should have only one of the "channel" green lights on (#2 on my list) and you should have processing "in". That worked for me.

Good luck.


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## Sonnie (Apr 11, 2006)

So the Engine button LED has nothing to do with whether they are active or not... makes sense, since activating the engine is with the IN/OUT button. If you see the red LEDs lit on that channel (the red filter LEDs), then the engine is active, regardless of whether the Engine LED is lit.


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## Otto (May 18, 2006)

That was my experience. But, man, I really wanted both those lights on!!! I guess they are there primarily for the "couple" mode.


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## bittermelon (Apr 19, 2006)

Sonnie said:


> So the Engine button LED has nothing to do with whether they are active or not... makes sense, since activating the engine is with the IN/OUT button. If you see the red LEDs lit on that channel (the red filter LEDs), then the engine is active, regardless of whether the Engine LED is lit.


That's what's missing or not clear in the manual so thanks Sonnie, Otto, and BruceK for clearing this up. I thought that both Engine lights had to be on for it to be active but it's the IN/OUT button that controls that. I'm a glutton for punishment, but I want to use that Athena as a buttkicker located nearfield behind the couch, but as BruceK alluded to in another thread, it brings on a host of other problems. Once I lug my PC downstairs again, I'll post graphs on how it went.


Thanks for clearing that up.


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## Splotto (Mar 14, 2007)

Hello:

Wow. This is a great thread. Thanks to everyone who put this one together.

Should be a sticky.

Splotto


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