# Will BFD increase input sensitivty similar to what a CleanBox does?



## myn (Sep 19, 2006)

I just finished my 14 cu foot IXL18.4 LLT sub tuned to 14hz. 

I am currently powering it with a Behringer EP2500 lead from a Panasonic XR-55 receiver. I am connecting my receiver to the EP2500 using the sub out (RCA) from my XR-55 into a 1/4 TS adapter into the EP2500.

It's pretty apparent the pre-out from my Panasonic XR-55 is rather low even with the gains on the EP2500 maxed. The sub sounds rather flat, as if it's missing something. Even comparing this to my previous Jamo sub which had 100 watts and a tiny 10" subwoofer.

I was thinking of doing some EQing anyways and was considering buying a BFD DSP 1224P. My question is, will the BFD raise the input signal similar to how a CleanBox will so the EP2500 can see a higher signal level?


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## brucek (Apr 11, 2006)

> will the BFD raise the input signal similar to how a CleanBox will so the EP2500 can see a higher signal level?


No, the BFD is a unity gain device.

brucek


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## myn (Sep 19, 2006)

Interesting.

So I am trying to understand. Why does the BFD have an "Operating Unit" boolean switch on the back -10 / +4 ? My impression of this was that the BFD would automatically adapt to the higher/lower signal and augment the level to an output signal matching a pro level output?

And when you say Unity Gain, how does this functionality differ from a CleanBox?

Hypothetically speaking if you were to set up shelfs on the BFD with a postive increase in an array of frequencies (say 10 - 60hz) would this not increase the level being sent to the amplifier? 

I really appreciate your help and guidance.


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## brucek (Apr 11, 2006)

> Why does the BFD have an "Operating Unit" boolean switch on the back -10 / +4 ? My impression of this was that the BFD would automatically adapt to the higher/lower signal and augment the level to an output signal matching a pro level output?


The two operating level switch settings are -10dBV and +4dBu. The switch doesn't change the level or affect the signal that it passes in any way through the unit. It simply changes the operating level. For example, if you sent a continuous peak signal sine wave from REW into the BFD with the switch set at -10dBV and then switch to +4dBu, you will see the LED indicators level drop quite a bit.... But there would be no change is volume of the signal. It only changes the operating level of the unit itself.



> And when you say Unity Gain, how does this functionality differ from a CleanBox?


Unity gain refers to a one to one relationship between input and output - no gain. The CleanBox device is a voltage amplifer - it has gain (at least some of the ART boxes do). You need a line level amplifier.



> Hypothetically speaking if you were to set up shelfs on the BFD with a postive increase in an array of frequencies (say 10 - 60hz) would this not increase the level being sent to the amplifier?


The BFD doesn't have shelf filters. If it did, you wouldn't use them as a wholesale gain device. You would use a voltage amplifer.

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

I was about to drop in a reply, but brucek beat me to it. I'll just add:


> It's pretty apparent the pre-out from my Panasonic XR-55 is rather low even with the gains on the EP2500 maxed. The sub sounds rather flat, as if it's missing something. Even comparing this to my previous Jamo sub which had 100 watts and a tiny 10" subwoofer.


Getting response graphs in REW for both subs would let us "see" what you're "hearing." Without that, it's impossible for us to tell you what the problem is based on what you hear, simply because we can't hear it. 



> So I am trying to understand. Why does the BFD have an "Operating Unit" boolean switch on the back -10 / +4 ? My impression of this was that the BFD would automatically adapt to the higher/lower signal and augment the level to an output signal matching a pro level output?


As brucek indicated, it's all internal, it doesn't change the output level. It merely gets the signal in the proper operating range, i.e., so the signal doesn't "live" in clipping or barely registering at all. Some pro audio gear has separate level switches for the input and output; those can boost the signal level if you have one in and the other out, but the BFD doesn't have that feature.



> Hypothetically speaking if you were to set up shelfs on the BFD with a postive increase in an array of frequencies (say 10 - 60hz) would this not increase the level being sent to the amplifier?


The BFD can't do shelving filters, but yes if you boost a plethera of filters it will increase the level being sent to the amplifier. However, using an equalizer as a level controller is poor form. It's best to leave the signal boosting to the proper component and use the equalizer for equalizing.

Actually, you may be worring for no good reason. The amp's gain controls are there to compensate for varying signal levels. The sub sounding "flat" has nothing to do with a signal level problem. Irrespective of the Panasonic's low output, if you can drive the amp to clipping with its gains all the way up, that's all you need. In lieu of that, if you can get as much level as you want out of the sub, that's good enough as well.

Regards,
Wayne


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## myn (Sep 19, 2006)

Great responses guys. Thanks.

Even with my pre-outs on my XR55 maxed and gains on the EP2500 all the way up I can never bring the EP2500 to clip .

So it sounds like my best bet now is to buy both a BFD and CleanBox, running the CleanBox after the the signal gets processed through the BFD.

As the CleanBox has a negative slope towards the low end of the frequency spectrum do you guys recommend something similar in price that is comparable or better performance wise?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Didja miss this part? :bigsmile: 



Wayne A. Pflughaupt said:


> In lieu of that, if you can get as much level as you want out of the sub, that's good enough as well.


If you're still convinced you need a signal boost, there's a sticky thread at our DIY Subwoofers Forum that can probably tell you everything you need to know.

Regards,
Wayne


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## myn (Sep 19, 2006)

Wayne A. Pflughaupt said:


> Didja miss this part? :bigsmile:
> 
> 
> If you're still convinced you need a signal boost, there's a sticky thread at our DIY Subwoofers Forum that can probably tell you everything you need to know.
> ...


Are you referring to the ART CleanBox mod thread or is there another? 

Ideally I'd like to have a dual purpose device that provided input gain, matching the pro input sensitivity as well as a lowpass crossover. 

I was looking at the Samson X-Over --> http://www.samsontech.com/products/productpage.cfm?prodID=1750

As you mentioned previously some devices have a unity gain. How can you tell if a device performs a unity gain versus what the CleanBox does?

Does this Samson use unity gain? or ? Would this fit my requirements?


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## brucek (Apr 11, 2006)

> How can you tell if a device performs a unity gain versus what the CleanBox does?


The manual on the url page you provide says it has 12dB gain. That should be enough.

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

For future reference:



> As you mentioned previously some devices have a unity gain. How can you tell if a device performs a unity gain versus what the CleanBox does?


 If there is no compensation for the input or output signal level that swings from a +/- dB value, either a knob or something that can be set internally (as might be the case with digital gear), then it's a unity gain device.

Regards,
Wayne


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