BFD 1124P: How to modify the high pass filter (?) (1 Viewer)

[Anthony_Gomez]

I remember reading sometime ago that the BFD had a high pass filter built into it somewhere between 22-16hz. I want to modify my BFD for an Fc around 10-12hz. Anyone know of what caps I should change? Also, can anyone think of a problem with this?

 

[Geoff L]

Man 16hz aint low enough..
What are you planning Anthony that would require filters that low.....

 

[Anthony_Gomez]

I run Linkwitz transformed subs. I just like my bass

 

[Geoff L]

So good audiable bass just aint enough,(20-hz-->up)
We now have to shoot for spl pressure in the in-auidable bass area.
Feel factor, Im for it! 12-hz at 115db, good god....Scary!
I can see the Crowns stacked now to power your LT'ed 15" Monsters.
Always fun to imagin
Sorry this isn't helping the real question you posted....:frowning:

 

[Anthony_Gomez]

nope...just running a pair of 12's right now. but later on when I will have 4 15's
lets see...4ohm drivers paralleled at 2ohms per side gives me 625watts per driver to work with
...ya....I think I need to move out of the apartment

 

[Geoff L]

Anthony, have you considered pro syke help!
Man your neighbors got to love you buddy!
Can't help you on the values, or where you might go to find something on it, sorry.
Maybe a call to Behringer.
You got a full schmatic (sp) of the guts?

 

[Will Orth]

Well this may be a neg reply but most recordings dont go below 20hz, most my material , I have 400 cd's and about 5 of theM do 20 HZ and those are all test discs. so if you get to 20HZ.... HATS OFF TO YOU.!

just my 3 cents...


Will

 

[Will Orth]

QUOTE:I remember reading sometime ago that the BFD had a high pass filter built into it somewhere between 22-16hz. I want to modify my BFD for an Fc around 10-12hz. Anyone know of what caps I should change? Also, can anyone think of a problem with this?

Well if you are trying a 6db-oct X-Over the coil would have to be about 30lbs and 8-10 guage, mag wire + a lot of dcr loss.. now far as a high pass filter dam i would have to dig in my archives on that one! 4- or 8 ohm? I would guess about 600 mfd but that is just a guess.

there is some one here I am sure that can help you quick
as it is just a table formula unles you are doing some 2-3 order net working..


Will

 

[Anthony_Gomez]

Will...the XO would be with an active filter, not a passive

 

[jeff lam]

Where is this HP filter you talk about? I read no such thing with the BFD. I would like to enable mine if it's in there. A 17Hz rumble filter would be nice.

Ant, got any more info on this HP filter?

 

[Anthony_Gomez]

I am trying to contact an INTELLIGENT behringer support member. My last email said this:

The DSP1124P has no built-in high-pass filter that you can switch off. The system frequency response is 20Hz to 20 kHz. There are no frequencies below 20 Hz.


talk about something you want to bust a gut on!

 

[Anthony_Gomez]

Dear Mr Gomez,
this roll-off is not an analog circuitry. The low-cut is caused in the A/D converter and cannot be removed.
Furthermore we do not recommend or give instructions for any modifications.

Thought you'd want to know. thought I am not sure I buy it. it is probably just a simple high pass filter. ...time to open up the BFD

 

[Anthony_Gomez]

Does anyone want to run a voltage sweep through the BFD against straight wire to see the attinuation? I may this weekend if I can get a chance...but I don't know if I will be able to.


Does anyone know the formula that relates a change in voltage to a change in Db.

Thanks

 

[Dan Pawlowski]

dB=20 log (V1/V2)

hey why not build 2 active filters (left and right) and insert at output of BFD before amplifier.

dan

 

[Anthony_Gomez]

hey why not build 2 active filters (left and right) and insert at output of BFD before amplifier.

thanks dan,...but I am not sure I understand what you are saying in the quote above. The BFD is not a single active filter, but rather a digital sound processer.

 

[Dan Pawlowski]

at any point does the BFD convert from a digital signal to an analogue signal??

 

[Anthony_Gomez]

on the output. but i am not sure of what filter you are talking about adding.

 

[Dan Pawlowski]

high pass filter built into it somewhere between 22-16hz. I want to modify my BFD for an Fc around 10-12hz.

my mistake

It looks as though somehow you would need to defeat the hi-pass filter first which being digital would require a code change of some sort(or crystal change depends). And if you could defeat it you can change it too. But i guess you already know this so i'm going to be quiet now.

dan

 

[Kevin Graf]

My DSP 1100 measured flat down to 10 Hz. It takes real good test equipment to measure low frequencies. The spec. was 20 to 20,000 but a spec. is just a spec.

Kevin

 

[brucek]

Anthony,

The BFD has no subsonic filter. The lower end continues to be linear until at least 5Hz. The output level drops off below that, but continues easily to 1Hz. I've tested this on my bench with my 1100. I have not read that the 1124 is any different.

brucek