# Getting started with a Behringer Feedback Destroyer PRO DSP1100P



## Andrew Mason

This thing is so powerful it's hard to get started, especially since I want out of the ordinary responce, not flat. Since it has 1/120th control I don't know where to start with Q... 60/120? Thats the default IIRC. I basically need to lower everything boosting nothing as I need to create a LP effect. I want 5Hz-10Hz to be 6dB above 11Hz-18Hz. I want 11Hz-18Hz to be 6dB above 19Hz-30Hz. I want 19Hz-30Hz to be 6dB above 31Hz-250Hz.

This is all guesstimation, obviousely not a 6dB drop between 1Hz increments... just to give an idea of what I am after. I may simply center at 45Hz and EQ down 24dB and vary my Q until I am happy, unless I get some good feedback.

Thank you for trudging through this post, trying to understand it, and if you even reply with help... thank you very very much.


KW


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## Moonfly

How do you plan on getting the particular eq applied that you want below 20hz. You can apply eq at 20hz with a wide Q and it will affect the response below 20hz, but how ideal that will be is hard to say.

Have you been using REW to try see the changes you want. It can predict the results of different filter setting as well, so if you havent tried using it, it might be a good place to begin.


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## Andrew Mason

Hey Moon, the only thing I have done with REW is sweep to see responce as well as test distortion at specific frequencies. I scanned through hooking the BFD properly to interact with REW, but I didnt go too deep into it.

What if I do a wide large boost at 20Hz, say 48dB with a wide Q, and another narrow cut at 20Hz with a small Q?


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## Andrew Mason

OK, I hooked the BFD back up... I cant sweep at the moment, we are relaxing watching internet TV. I set filter 1 to 20Hz, left the Q at 60, and boosted to max 16dB. I quickly played Bass I Love You to see how careful I need to be, it's very boosted.... we are watching at a very very low volume, -45dB master, but BILY was pretty loud, but 1/4 excursion at most during the 16Hz tone and unfortunately only 1/8 or less at the 7Hz tone.... so I am probably much better off already having done what i just did, but I would like to bring the 5Hz-10Hz up much much more and reduce that 15Hz-25Hz or however wide the Q of 60 is boosting.


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## Andrew Mason

alright, I know I need help setting the smoothing and limits so for now I defeated the EQ...also because my set up sweeps showed 20Hz too big and narrow, killing the ULF. These are all EQ flat, looking for an average 75dB, as well as a sweep where we usually listen/watch HULU and Netflix: -35dB master volume. 1st things 1st I think will be to EQ down at 42Hz where that spike is. That is what i think I am hearing that I dont like: It's loud with very little lows or ULF.


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## Andrew Mason

alright, I need to get to boosting, because I didnt like the sound before... was boomy... I EQed down 40Hz, taking the boomy boom boom out killed the subs altogether.


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## Andrew Mason

added 16dB boost at 20Hz with max width Q of 120


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## Andrew Mason

added another 16dB boost at 20Hz full width of 120 for Q


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## Andrew Mason

its working! another boost and cut, another boost and cut again


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## Andrew Mason

Filter 1: 40Hz -48dB Q 60
Filter 2: 20Hz +16dB Q 120
Filter 3: 20Hz +16dB Q 120
Filter 4: 20Hz +16dB Q 120
Filter 5: 20Hz -16dB Q 60
Filter 6: 20Hz +16dB Q 120
Filter 7: 20Hz -16dB Q 60
Filter 8: 20Hz +16dB Q 120
Filter 9: 20Hz -16dB Q 60
Filter 10: 20Hz -16dB Q 60
Filter 11: 40Hz -48dB Q 60


1st problem: as I was adding the last 2 filters I noticed rumbling got loud when I added dB, then i realized 1 side was doing it but not the other, before I saved it, though both engine lights are on. When I did the following cut it fixed it...but that doesnt mean they became symetric again. So I did sine waves at 6.5Hz, 10Hz, and 16Hz to make sure both sets of subs have the same excursion. They do. However, at 6.5Hz when I get it loud enough to get amplifier noise, it was on the same side that suffered rumbling. 

Anyway....

the 2nd -48dB cut at 40Hz killed it:










but then the last filter, 12, boost 16dB at 20Hz Q of 120 fixed it and I am happy for now.










Final sweep


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## Andrew Mason

I started to remove several filters as there was too much 5Hz-10Hz and everything else was dead, as I removed the 2nd 40Hz the buzz came back, and only on 1 side. Something is wrong so I took the BFD back out. Ran Audyssey for the 1st time, IDK who's system this is...but its totally different...instantly. 

Here's sweeps starting at -35dB in 5dB increments to -20dB and I still have a TON of headroom.


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## Andrew Mason

I see this got moved to its proper location, thank you! 

Audyssey set all speakers to negative something, the sub was -12dB. I swept it again with -9dB then -6dB and still have headroom, but not much, so i will leave them at -6dB


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## Andrew Mason

How does REW know how far down it can EQ? How can I get that spike at 5Hz, or at least make it flat to 5Hz?


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## Andrew Mason

I rewatched Caprica Season 1 : Ep. 16 The Heavens Will Rise over and over with Brandy. At 1:54, 1:56 - 1:57, and 2:06 - 2:10 I get that real awesome ULF I have been chasing...same as I got it with the towers, maybe a bit less. I had brandy lay on the platform, I would play sine waves starting at 5Hz up to 20Hz in 1Hz increments and let her get a good feel of what is what. 5Hz is barely feelable. 6Hz barely better. 7Hz starts to get easier to notice and the ceiling fan jiggles. From 5-7Hz at high volume for more than a few seconds the amp(s) starts to make noise. 8Hz on up is solid. Brandy is pretty set that those time stamps in Caprica are about 8Hz. I feel my port is pretty wasted down at 5Hz. I've had a bad null at 6.4Hz all along, it seems to fill it, but I can't break that 110dB mark let alone 115dB.

Before I do any cutting, I'd like to plug the port and re-run Audyssey, hopefully it will add more boost from 5Hz-9Hz that way, then if I unplugg it it will maybe be flat to 5Hz? Prolly not.

After doing so I am considering either running two divider boards front to back to make for 2 8.25"x21"x21" ports, or, cut the sides of the ports out...which will be uncalculable...and run sweeps to guess where tuning ended. 

I am considering raising tuning to 7Hz as I still have that sharp fall at 10Hz that i had with the towers. I want my single digits to peak above 10Hz on up and I just can't get it tuned to 5Hz.

Sure I still need to run 2x4s all around the door with weather stripping, a lot of air leaks, but even then and after bracing the rest of the ceiling.... IDK. 

I wish the EQ wasn't making 1 amp/channel run different than the other. I don't know what to do...tomorrow I can swap RCAs and see if the problem goes to the other 2 subs/other amp.


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## Andrew Mason

I used to get told using port dividers completely altered tuning, turning 1 port into multiple smaller ports. However, if I put 2 dividers from front to back off the center brace, which is 4.5" wide, taking up a 4.5"x18.5"x22" volume of air from the port: 1 cubic foot.... My tuning only changes from 5.11Hz to 5.22Hz. Plotting a single 21"x18.5"x22 inch long port VS two 8.5"x18.5"x22inch long ports



















So it looks like if I want to tune higher I need to cut.


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## Andrew Mason

I forgot about the sides...side port walls...being more for blocking cancellation through the port than for lower tuning. If I cut the sides out, they are right below the bottom subs, the air will flow right from the front of the subs through the port and cancel with the rear wave. I think i will try to get 6 more 9' 2x4s and weather stripping to seal the door/manifold off better and brace the ceiling more first. If I do cut the sides out, Ill prolly cut them in 1/2 and put a fin just below the bottom sub and another fin right at the top of the cut out to reduce cancellation by forcing the wave to travel a bit further over both fins.


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## JohnM

That set of filters you posted was pretty bizarre. Have you looked at REW's EQ window yet? REW will show you the effect your filters will have on the response, and you can see how different bandwidth settings change the response. Try playing with the filter settings in REW to get a feel for the effect they will have, that will let you come up with something suitable - start with a single filter. You can use the DSP1124P setting with the DSP1100.


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## Andrew Mason

Thank you John, I will have to check that out. I've got to figure out whats up with this BFD first, it introduces noise into 1 channel but not the other.


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## Andrew Mason

just ran another sweep with the entry way door sealed up. So much for retuning higer, work on more bracing and more sealing up and I should be golden to 5Hz.


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## Wayne A. Pflughaupt

Andrew Mason said:


> I basically need to lower everything boosting nothing as I need to create a LP effect.


The BFD is not a good tool for low-or high pass filtering of any kind, or EQing below 20 Hz. I’d suggest the Rane PE17 or Symetrix 551 for those capabilities.

Regards,
Wayne


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## Andrew Mason

Thank you Wayne, should I leave it as is since Audyssey did pretty well, then work on sealing up and reinforcing more?


Little vid i made of REW and a couple sweeps, a lot of people that subscribe to my vids have no idea what REW is, where I get my numbers or graphs.

110dB from 5Hz up REW Room Eq Wizard.AVI


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