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Discussion Starter · #1 · (Edited)
Hi guys,

I have been reading about what input level (button on the rear panel) you should be having it on. I have an Onkyo 876 going through the BFD DSP 1100 to a Behringer Europower 4000 pro amp onto two a dual 18" sealed sub. I have it currently in the IN position (-10dbv). I have the behringer set to 30db (almost max) and -9db sub trim level. I have applied all my filters to get the graph as attached. I had to boost the 20hz by 14 db to get the low end up as much as I could which sounds how I like it. I have boosted the 20-40hz areas slightly. I do also have a flat response filter set too which I flick from one to the other.

I was playing bassotronics at -20db and on the really low bass I noticed that the the input level lights on the BFD would go into the red as it played the low stuff and then go back into the green. My main concern is that the drivers still had alot more to give but the BFD didn't. I could probably go a bit further but I doubt much. Would changing it to the out position give me more input on the BFD or am I missing something.

Also how good is the Art Cleanbox 2 for getting rid of hum?

Many thanks

Graham
 

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If you change the button on the back to 0db or +4 whatever it is you will loose even more level to the BFD so you should leave it as it is.
 

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Discussion Starter · #4 ·
Tony

Thanks for the reply. I need to have another read of the BFD guide in setting up the input levels.

To be honest I have really done that as such. What I did was run a REW graph with no Audyssey with no BFD. Then I run Audyssey to set up my distances for my speakers/sub etc... I then ran another REW graph with no BFD to see how much Audyssey smoothed out the response. I then hooked up the BFD and adjusted with the filters for the two settings and ran new graphs.

I then double checked my sub to my spl meter so it was running 80db (slightly hot). I did notice that I had to increase the sub trim level after I added the BFD as it was quiter. So I didn't actually check the input level as such but made sure the sub was running at 80db with the onkyo test tone.

Does that sound about right?

cheers

graham
 

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I had to boost the 20hz by 14 db to get the low end up as much as I could which sounds how I like it.
Far too much of a boost. The red led on the VU meter is showing the output level, and the reason they're clipping is that filter.

Would changing it to the out position give me more input on the BFD or am I missing something.
Yes, switching to the +4dBu position will change the operating level allowing more input level swing, but the noise floor will probably rise a bit.

brucek
 

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My main concern is that the drivers still had alot more to give but the BFD didn't. I could probably go a bit further but I doubt much. Would changing it to the out position give me more input on the BFD or am I missing something.
How are the gain knobs on your Europower amplifier? Are they maxed out, or is there more room?

Regards,
Wayne

 

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Discussion Starter · #7 ·
Wayne,

I have the behringer mono bridged into the dual 18" sealed sub. The gain is set to 30db which is 2db from max. Behringer said I should have it on max. I originally had it on about halfway and then just turned up the sub trim level.

I have to say at -20db playing bassotronics there is alot of low end bass and in you can feel it coming through the kitchen units in the next room.

What are your thoughts.

If the subs are calibrated to 80db why would I be running into the red on the input level on the BFD. I could understand if the sub was calibrated to 95 or 100db.


cheers

graham
 

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The situation is that Behringer amps are a bit "insensitive," which means it takes a lot of signal to drive them. This is why the amp's gain settings are pretty well maxed out instead of sitting at say, 1 or 2 o'clock. In turn, the high signal levels required from the receiver's sub output means that it's easier to drive the BFD into clipping when its -10 dBu gain setting is used. So, your only options are what's been recommended: Either lose the 20 Hz filter (which I'm sure you don't want to do), or switch to the +4 dBu setting.

(My thanks to brucek for the information on the amplifier's sensitivity. :D )

Regards,
Wayne
 

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Discussion Starter · #9 ·
Wayne,

So changing to the +4 setting will playing the same bassotronics song at -20db with the same BFD filters make the BFD not go into the red clipping light. Sorry for the dumb question.

So is it a way of making the BFD think it has more input available.

cheers
graham
 

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In a manner of speaking, that is correct. Both operating ranges can be thought of as an internal gain structure. There is a 20+ dB difference in nominal levels between the +4 dBu and -10 dBV operating ranges, so one internal gain structure cannot be optimized for both. In other words it’s impossible to deliver, at the same time, the best headroom and the lowest noise floor from a single gain structure. The higher-level +4 dBu range will deliver the best headroom, while the lower -10 dBV range delivers the quietest noise floor, hence the switchable ranges. So if you’re topping out the -10 dBV setting, that means you need more headroom. So at that point the +4 dBu setting should be used.

Regards,
Wayne
 

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Discussion Starter · #11 ·
Wayne,

Thanks for that. The subs at that volume with 14db of 20hz boost still have quite a bit of excursion to go. I have two Q18" drivers with the BP upgrade and according to winISD at 2400 watts rms into 4 ohms bridged I am running only 22mm excursion which is still 5mm below max. At 40hz and over it was showing 127db onwards with 102db at 10hz without room gain. So I figured with that amount of spl at 40hz etc.. I would have no problems in boosting the 20hz region as the qtc of my sub is about 0.950 without stuffing. I have added 4kg to my 10cu ft box to bring it down a bit. I have to say I am very impressed with these drivers. They just seem so effortless.

Will I need to EQ or anything when I change the input switch?

cheers

graham
 
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