BFD Hookup Question

**rolyasm** · **07-13-06, 08:29 PM**

There are 2 inputs and 2 outputs on the BFD. Am I connecing one cable from my processor preout to the BehringerFD, and if so, does it matter what input, or am I using a splitter and connecting to both inputs? Next I am connecting my BFD to my Behringer 2500. Again, am I using one or two outs. If one out, do I run a y-splitter and connect to the 2 inputs on the amp, or just one input on the amp?
Roly

**brucek** · **07-14-06, 05:37 AM**

The answer depends on the situation.

If you are using two subwoofers and they require differing equalization, then you split the signal feeding the BFD and connect the two subwoofers to the two BFD outputs. This allows the two BFD channels to be used independently.

If you are using two subwoofers and they will be using the same equalization then you can feed one channel of the BFD and split that output BFD channel to the two subwoofers.

If you are using one subwoofer, just use one channel on the BFD fed to one channel of the subwoofer amplifier.

brucek

**rolyasm** · **07-14-06, 11:37 AM**

Sorry, my first question was vague. I am using 4 drivers. 2 drivers per channel off my Behringer EP2500, running a mixed parallel/series system for a total of a 2 ohm load per channel. The subs are all in the front of my riser, kind of installed in pairs. Each driver in the pair is about 8 inches apart, and then the next pair, mounted the same is about three feet from the other pair. I would have mounted them all next to each other equally spaced, but I might put stairs between them. Thanks .
Roly

**brucek** · **07-14-06, 01:06 PM**

Quote:

If one out, do I run a y-splitter and connect to the 2 inputs on the amp, or just one input on the amp?

Well, if you are using both channels of the 2500 amp (as you've indicated above) then you certainly need to drive both channels of the 2500 from the BFD.

You would then feed one channel of the BFD from your processor and then split that BFD's channel output to drive both channels of your 2500 amp.

brucek

**rolyasm** · **07-14-06, 01:35 PM**

Thanks Brucek. What is the purpose of having 2 inputs on the BFD? Is that for its actual purpose of destroying feedback ? Would I get any more EQ options by using both inputs on the BFD?
Roly

**brucek** · **07-14-06, 01:51 PM**

Quote:

What is the purpose of having 2 inputs on the BFD?

It's a two channel device with completely independant equalization for each channel.

If you were driving two subwoofers located at two different locations in your room and each required a different set of filters, the two channels are required....

Quote:

Would I get any more EQ options by using both inputs on the BFD?

Sure, you'd get 12 separate filters per channel. In your case you don't require them. One channel will suffice.

brucek

**lewdog** · **07-20-06, 09:07 PM**

My question is this--which would have a better output stage and be better able to support splitting a signal? I want to run two subs, with the signal starting from my receiver's sub-out (Denon 3802) and then being fed into the BFD and then to the subs. Is splitting at the receiver or BFD in terms of signal strength and low distortion better? I am going to apply the same filters, so I am not in need of two separate filter sets.

**brucek** · **07-20-06, 09:49 PM**

Quote:

Is splitting at the receiver or BFD in terms of signal strength and low distortion better?

No difference.

The reason though, that I would split before the BFD and send a cable from each channel of the BFD to each sub is that it provides you with the future opportunity of setting unique channel filters.

brucek

**rolyasm** · **07-22-06, 02:54 AM**

Thanks Brucek,
I just read the thread you posted for another loser, er I mean beginner, like myself. The step by step approach really helped me out. I will post some graphs tomorrow if I can figure it out. Here is where I am so far.... I have calibrated my soundcard (graph coming) and it looks fairly good. Quite a drop off around 10-15 hz, so I will let you decide if it is alright. I used my SPL meter and set my processor volume until the RS SPL read a "0" on a range of 80. My Sherwood is at -4 (starts at -50 I think). Then I disconnected my SPL. Next, I hooked up my mic, the ecm-8000 and loaded its calibration file. Then I ran my sweep. The message I got said something about my input level, or some level was low at -64 (dbFS) and should be reading at least -10. I will post the exact message when I get home from my graveyard shift. The message said to check volume controls, mutes, and those sort of things. My window control shows my volumes are all up. I increased the gain on my amp and soundcard and my level climbed to a -37, but still the message saying it should at least be -10. If this doesn't make any sense, I will post the graphs and exact message tomorrow. I thought you might be able to decipher my babble so I would have something to work on when I wake up later. Thanks for all.
Roly

**brucek** · **07-22-06, 06:53 AM**

Quote:

The step by step approach really helped me out

Good.

Quote:

Quite a drop off around 10-15 hz, so I will let you decide if it is alright

Yeah, that's expected. That poor response is of course why we need the soundcard calibration to file to make the response flat.

Quote:

I used my SPL meter and set my processor volume until the RS SPL read a "0" on a range of 80. My Sherwood is at -4 (starts at -50 I think). Then I disconnected my SPL. Next, I hooked up my mic, the ecm-8000 and loaded its calibration file. Then I ran my sweep. The message I got said something about my input level, or some level was low at -64 (dbFS) and should be reading at least -10.

No, I believe you have this a bit backwards. I only use an RS SPL myself, but I think I know how this goes - Sonnie can comment if I'm wrong.

(1) Hook up your ecm mic and load its calibration file. Then when you take the SET MEASUREMENT LEVEL you have your mic hooked up and then hold the RS meter beside your mic and adjust the volume of your receiver until the RS SPL meter reads 80db (then you can put the RS SPL meter down). Now the output of REW and your receiver are producing 80dB in the room.

(2) Now when you press SET INPUT VOLUME you have the level of your mic pre amp to play with to be sure REW is getting a level high enough to satisfy its input level requirements. This is where its different, because the RS SPL meter outputs a proper preset line level. You need to be sure your mic and preamp are doing the same thing. Adjust the pre amp and click Set Input Volume several times if you have to until REW is happy with the level.

(3) Once that's satisfied, you now have the output level in the room at 80db, and the input level to REW at the correct level, so you need to calibrate the REW SPL meter to match the needle on the RS SPL meter of 80db. Well you've already established that the room level is at 80dB, so you can go on faith the when you press CALIBRATE and REW asks you to toggle the icon until it matches the level of the RS SPL meter that you should set it to 80dB. get it?

(4) Now do TARGET LEVEL as normal

(5) Now do AUTOMATIC MEASUREMENT as normal..........

brucek

**rolyasm** · **07-22-06, 10:07 AM**

As usual, thanks again. I can't wait to get home and start playing. Next Question: I read that it is best to use the input/output level that I will be using to make measurements. Since I am using my XLR for the mic input and the 1/8" output through an RCA/1/8" connector like shown on your diagram, is there cable that I can make or buy that is XLR to
1/8" or XLR to RCA? I will check with radio shack on the way home today, but I don't believe in my 97 trips to the store I have seen anything like that. The way I calibrated my soundcard was to use the 1/4" in and outs. Is that adequate? Thanks again.
Roly

**brucek** · **07-22-06, 10:40 AM**

Quote:

Next Question: I read that it is best to use the input/output level that I will be using to make measurements.

Don't really understand this question. The levels that are set during the REW setup are specific to REW and have little to do with your usual system settings. REW is simply a tool we use to find the frequency response of speakers in a specific room environment - it requires one time specific levels to be set in order for it to work in harmony with a crappy computer and its soundcard. Your levels that you set for your speakers after that are up to you and don't interact with the REW setup....

Quote:

Since I am using my XLR for the mic input and the 1/8" output through an RCA/1/8" connector like shown on your diagram, is there cable that I can make or buy that is XLR to
1/8" or XLR to RCA?

I'm not familiar with the connector outputs of your mic preamp. I presumed they would be a simple RCA, that you would extend with an RCA cable - then plug that into a (stereo RCA to stereo 1/8" adapter) into the soundcard. Adapters are perfectly fine for this application. You don't need great cables here - just the correct adaption. What is the output connector on your mic preamp?

brucek

**rolyasm** · **07-22-06, 10:53 AM**

Sorry, it was poorly phrased. Lack of sleep I guess. I didn't mean to say input/output levels. I read that it is best to use the input/ouput jacks that I will be using to measure with to calibrate the soundcard. So most people would just connect a RCA from the 1/8" input to the 1/8" output. However, since I am using XLR (mic) input and 1/8" out for measuring, I was wondering how important it was to use the ports I will be using for measurement. So do I really need to use the XLR/1/8" to calibrate my soundcard, or will I get a good enough measurement using the 1/4"out and 1/4" input, which I won't be using again for taking any measurements. I just happen to have the 1/4 to 1/4 cables to calibrate it this way, and I am not sure if I can find an XLR to RCA adaptor. I hope this helps. Thanks.
Roly

**brucek** · **07-22-06, 12:08 PM**

Oh OK, I get it. I forgot you had an M-Audio soundcard.

You're kind of stuck then doing the soundcard cal the way you've done it with the 1/4" input to 1/4" output. The XLR to RCA wouldn't be possible here. Should be fine.

That reminds me that in the manual for your soundcard I see that the gain 1 control is for Channel 1 XLR and gain 2 is for the Channel 2 XLR. You'll need that gain control when you are setting the SET INPUT VOLUME I referenced in the post above. It would be the same as an external preamp gain control (I trust).
Be sure to know and connect the correct left or right 1/8" line output channel that corresponds to channel 1 or 2 XLR input that you use.....

brucek

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