# Sensitivity switch on the BFD?



## Jerm357 (May 23, 2006)

So I been using an art cleanbox to boost the signal form my Onkyo receiver to +4dbu to feed my EP1500 pro amp. I also have a BFD DSP1124 in the chain. Receiver > clean box > BFD > Ep1500. Now what would you say the right sensitivity position for the switch be at -10 / +4? Rigth now Im not having any problems, I have the clean box at about 10 0'clock and the amp at 1 o'clock with the BFD set at the -10position and can achieve my desired spl level with out clipping the BFD like this. I was just wondering if I should be using the +4dbu setting because of the clean box boosting the signal to +4 dbu?


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## brucek (Apr 11, 2006)

> Receiver > clean box > BFD > Ep1500


Kinda backwards. The cleanbox should be after the BFD - not before it.

The receiver should have no problem providing sufficient level to satisfy the BFD when in the -10dBv operating range. Once you've reached and set this maximum input level, you can't increase the level any more even if you wanted to. So it's the BFD's *output* analog signal that you want to amplify, not the input signal which is easily set to optimum by your processor sub trim and master volume. 

The BFD's unity output (or less if filters are applied) can then be amplified to your hearts content with the cleanbox line amp. If the line amp can create 18dB gain, then it will 'all' be available to you, instead of being limited if you placed the line amp before the BFD.

brucek


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## Jerm357 (May 23, 2006)

The reason I have it set up like this is because the clean box, BFD and amp are in the basement right under the floor of the room the system is in.









_the knobs in the pic are when I was using the +4 switch_

Since both my knobs are about 50% (_now_) I thought I was in good shape ( I know the knobs on the amp is not a gain) I set the sub trim to -10db on the receiver (-12db to +12db) then set the level with the clean box to what the BFD likes at my reference point (using WOTW) then adjust the gain on the amp to 85db (using Avia). That way I have some control of my bass volume in the room Im in with the sub trim for when Im not listing at reference (which is realy never. Mostly listen at -20 to -15). Do you realy feel that there is preformance to be gained by setting it up like you said at the expenses of losing in room bass control? Or do you think I should measure how hot Im using the sub at -20 now then set it up like you said and adjust the sub to that spl level. I guess I could do that since I realy have'int changed my sub trim since Ive found the sub's spl I like at -20( I realy lack bass when the levels are level since I dont realy listen near reference, so my sub is 15db hot when I listen at -20 and under)


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

> The reason I have it set up like this is because the clean box, BFD and amp are in the basement right under the floor of the room the system is in.


??? There’s nothing that says you have to have it connected in the order it’s all stacked...



> Since both my knobs are about 50% (now) I thought I was in good shape ( I know the knobs on the amp is not a gain) I set the sub trim to -10db on the receiver (-12db to +12db) then set the level with the clean box to what the BFD likes at my reference point (using WOTW) then adjust the gain on the amp to 85db (using Avia).


With your receiver’s sub out turned almost all the way down, and the amps gains only at 50%, I have to wonder why you even have the clean box at all? :scratch: 

Regards,
Wayne


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## Jerm357 (May 23, 2006)

"??? There’s nothing that says you have to have it connected in the order it’s all stacked..."


I know, thats not why it hooked up that way. If I hook the receiver to the BFD > clean box > amp, Im going to lose in room control of the bass because the sub trim will be locked at the receiver (_instead of the clean box _) at a certain db and than the only way to adjust the level is to go downstairs and adjust the amp 'gain' when listing lower than reference.

"With your receiver’s sub out turned almost all the way down, and the amps gains only at 50%, I have to wonder why you even have the clean box at all?"

As it sits now I have the trim at +5db which is 15db hot over the mains but thats because Im only listing at -20 under reference. I just used the -10 so my levels are equal at reference if I ever want to go there. Does this make sence its kind of hard to explain?? I guess it all comes down to how much do I realy adjust the sub trim. Theres only been about one time that I need to lower the trim to play at -10 and with that I lowered the sub trim to -5db which is 5db hot over the mains. So the question is do you realy think Ill gain anything by hooking it up Receiver > BFD >clean box > amp ? It does sound great the way it is now.


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## brucek (Apr 11, 2006)

> Does this make sence its kind of hard to explain??


No, actually I'm lost with all the dB references. Every manufacturer uses different references with dB's, so best to explain without numbers. Tell us what the *problem* is without numbers. Just generally. 

Normally, you just set the sub level and from there it tracks the receivers master volume..

brucek


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

I’m with brucek, I’m not following your thought process, with the “trim” this, “gain” that, “dB” here, “level” there. Half the time you don’t identify exactly what it is you’re “trimming” or “gaining.” For instance, sometimes it looks like you’re sub “trimming” at the receiver (first paragraph), and at other times, elsewhere (third paragraph).

And...


> If I hook the receiver to the BFD > clean box > amp, Im going to lose in room control of the bass because the sub trim will be locked at the receiver (instead of the clean box )


Makes no sense to me why sub levels would be “locked” at the receiver – unless it has no sub adjustment capabilities, but you’ve already indicated that it does. :huh: Probably I’m not getting something...

And what is “room control of the bass?” Volume?

Plus, I still don’t see why you need the clean box. There is only one good reason to use one: If the signal going into the amp isn’t high enough to drive it to maximum output. I suppose it could be used in front of the BFD if for some reason your receiver had a really low sub output, but that would be the only other scenario making one necessary.

I hope this doesn’t come across like we’re just busting your chops – we’re just trying to understand the problem.

Regards,
Wayne


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

Maybe we should back the boat up. If this is all you’re trying to figure out...


> I was just wondering if I should be using the +4dbu setting because of the clean box boosting the signal to +4 dbu?


...We can just cut to the chase: There is no advantage to using one setting over the other. Use the one that keeps the BFD’s meters from hitting into the red.

Regards,
Wayne


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## Jerm357 (May 23, 2006)

"Makes no sense to me why sub levels would be “locked” at the receiver – unless it has no sub adjustment capabilities, but you’ve already indicated that it does. Probably I’m not getting something..."

I say locked because the subwoofer trim will be stuck at a given db so the BFD can get the needed signal. Right now the clean box is doing that with the sub trim at -10db and I can get the led bars on the BFD just barly max out at reference (mine is 85 on the main volume using Avia (1 to 100 is the MV range)) So if I ever listen at reference my speakers are level with the sub trim at -10db but with my normal listing I use +5db on the sub trim to make my sub 15db hot over the other speakers and never go over -20 from reference.

"And what is “room control of the bass?” Volume?" 

Since all my sub equipment is down stairs the only control I have on it is the subwoofer trim on the receiver once the clean box and amp are set.

"...We can just cut to the chase: There is no advantage to using one setting over the other. Use the one that keeps the BFD’s meters from hitting into the red more than momentarily."

Thanks thats all I realy need to know. Tell you what Ill try and hook it up the the way you guys are saying one of these days and report back the difference.


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## bigguy (Feb 26, 2007)

ok... Ill bite.. where do you get an ART Cleanbox? :dumbcrazy: 

This has gone from pastime to hobby to sickness... With that progression, I think that this is surely a disease of some form...

Boy is it catching.. :jump: 

Thanks
Dan


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## bigguy (Feb 26, 2007)

DOH... Never mind... Got one from eBay. 48.00 delivered. 

Sorry bout that.

Dan


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## Jerm357 (May 23, 2006)

Wayne A. Pflughaupt said:


> ??? There’s nothing that says you have to have it connected in the order it’s all stacked...
> 
> With your receiver’s sub out turned almost all the way down, and the amps gains only at 50%, I have to wonder why you even have the clean box at all? :scratch:
> 
> ...


Well Wayne you were right. I no longer need the clean box with the BFD. I can now get a good signal without it. It might be just because now I have the LED signal lights assuring me a full signal. Since the BFD at maximum level (when using the -10dBV switch setting) puts out 1.26volts I know Im good since my amp only needs 1.15volts for max power. Now every thing is fine with the receiver sub out set to 0db and the amp at 50% and one less piece of electronics in the chain. Also, I think I may have gained a little bit of sound quality too. I dont know why I did'int try it with out the clean box when I got the BFD, I just figured that I needed it.:T Anyways thanks for getting me thinking about it.


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

Glad so see it all worked out. :T Too bad you didn't figure it out soon enough to sell yours to Dan! :laugh:

Regards,
Wayne


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## Jerm357 (May 23, 2006)

No worries I already got rid of it on ebay.


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