# Boosting low ends with a BFD1124 ?



## smokarz (Apr 13, 2011)

so i am almost finished building 4 sealed subs and picking up a bfd1124 to help flat the response, but most importantly want to boost the low ends of the sealed subs.

i read Wayne's article on minimal eq and hard knee house curve article, but unfortunately much of it was over my head. but i really like the minimal eq with just 2 filters to help flatten the fr curve.

are there quick/easy way to boost the low ends? i think i will follow wayne's 2 filter approach to flat the repsonse but not quite sure how do achieve the low end boost.

thanks!


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## Zeitgeist (Apr 4, 2009)

smokarz said:


> so i am almost finished building 4 sealed subs and picking up a bfd1124 to help flat the response, but most importantly want to boost the low ends of the sealed subs.
> 
> i read Wayne's article on minimal eq and hard knee house curve article, but unfortunately much of it was over my head. but i really like the minimal eq with just 2 filters to help flatten the fr curve.
> 
> ...


I highly recommend reading the BFD Guide:
http://www.hometheatershack.com/forums/bfdguide/

If you're just looking to boost the lower frequencies, it should be very easy if you skim through the guide.

Setup is awkward at first but makes sense once you get the hang of it.


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## smokarz (Apr 13, 2011)

thanks, i did read the guide. actually twice now but still a bit overwhelmed.

the input level setting section is still unclear to me.

1 - set bdf1124 to bypass mode
2 - set avr lfe output level to 0db (no boost)
3 - set avr volumn to normal listening loudness (maybe a few notches louder)
4 - find a hevay base scene
5 - play the scene and see if the top yellow LED (near the red LED) is lit - *if top yellow LED is not lit, increase avr lfe output level and replay scene until this LED is lit?*

did i get this right?


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## Zeitgeist (Apr 4, 2009)

Setting the level is easy, normally you can leave it in the -4 setting on the back.

Really, the LFE output volume and the sub gain are what are important.

You just want to keep the level from peaking and hitting red, whether it's in green or yellow doesn't really matter.


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## smokarz (Apr 13, 2011)

thanks,

the guide said to set the operating level to -10dbv, is it really ok to leave the setting at +4dbu?

so, i can leave my avr lfe at 0db, 3db, or 5db, play a bass heavy scene at loud volume and as long as the bfd doesn't clip (Red LED) than i am fine?

than i just use the volume knob on my ep2500 to adjust the sub volume to match my mains?

if the above is true, i think the guide really need an upgrade as the new info is inconistent with the guide. also, does anyone really take manual measurement with an Excel sheet, now that we have REW? and i really didn't mean it with disrespect, but i think it would be a lot of help for the new guys like myself who comes here for help with eq and being pointed to the 'GUIDE' only to realize the info on the guide is a bit outdated.

thanks!


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## Zeitgeist (Apr 4, 2009)

smokarz said:


> thanks,
> 
> the guide said to set the operating level to -10dbv, is it really ok to leave the setting at +4dbu?
> 
> ...


Sorry, I meant -10 not -4. You want -10 for a lower noise floor. If you set the AVR to 0 and the LFE to 0 and play something, make sure it doesn't end up in the red. I think that you're worrying way too much about the level setting. You just need to make sure you don't see red. If you see red, change to +4.

You will need a db/SPL meter to compare a test done of the sub to the AVR, make sure that it's at the same level. If you have Audyssey, it will attempt to set the level automatically.

What AVR do you have?


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## smokarz (Apr 13, 2011)

thanks, and sorry i am just taking this all in and try to have a good understanding for when i actually sit down and to the setting up and eq so i won't have to be flipping back/forth between web pages and guides to find the info.

here's my system:

Integra 9.9 pre/pro
Emotiva UPA-7 => 2 Crites DIY CS-1 Speakers
EP2500 => 4x 15" MFW-15 DIY sealed subs

my next questions would be:

1) do i do the level setting before or after i run Audyssey? I am sure that Audyssey will readjust the lfe out when it's done.

2) do i apply the low end boost before or after i flatten the FR.

3) what is a generally good low end boost? i have been seeing +7db at 20hz?


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

Really, the only reason to apply a low-end boost is if your sub’s low end is sagging – e.g. it drops off below 25-30 Hz. With four 15” subs I doubt you have that problem. Do you have a graph you can show us?

BTW, the “two filters” is not a hard rule. It just happened to work in the example I gave in the article. You might need more, depending on your particular response curve. Basically I wrote the piece because lots of people (including myself) were going nuts with the filtering, using the equalizer like an iron, trying to get out every last little wrinkle in their response. Feel free to use as many filters as you need; just keep in mind that the _audible_ results will come from dealing with the worst peaks and troughs, not all the little ones. 

Regards,
Wayne


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## smokarz (Apr 13, 2011)

this is the graph for 2 subs, they're on the front left and right corners. i have yet to finish the other two.

they provide great bass for music, but it seems i am not getting enough oomph for movies. and from what i've heard, sealed subs could use some boost on the low end. thanks


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

You’ve got flat response down to 10 Hz, so you don’t need any low-end boost! That big hole on the 70 Hz area might explain at least some of the lack of “oomph.” You could definitely use some EQ to smooth that response, and perhaps dial in a house curve.

Regards,
Wayne


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## smokarz (Apr 13, 2011)

thanks much Wayne.

according to your article, i shouldn't be touching the area around 70hz if i want to crossover at 80hz correct?

if i boost the 70hz, then i should consider crossing around 100/120hz?

should i try to bring down the peak around 44hz?


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

Since your graph appears to be the mains + sub, and it looks like combined response is getting the 70 Hz trough, you might try EQing the sub in that range to compensate. You might try moving the crossover point higher, but that usually means the sub is too easily localized. Yes, the peak at 40 Hz should be addressed. :T

Regards,
Wayne


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## smokarz (Apr 13, 2011)

wayne, the previous graph shows the subs only.

here's the graph with subs and mains measured separately. purple is the mains.


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

Why is the sub flat out to and beyond 300 Hz? Doesn’t your AVR do low pass filtering? 


Regards,
Wayne


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## smokarz (Apr 13, 2011)

it does, but i set it to 250hz in order to get all the signal through the sub when i run the sweep from 10hz to 200hz.


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

Okay - well, for determining what filters to use, it's best to take the sweeps with the system as you'll use it - e.g. with the appropriate crossovers engaged.

Regards,
Wayne


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## smokarz (Apr 13, 2011)

thanks, i should finish building the 4th sub this weekend. once i got them all hooked up, run audyssey, and then i apply a boost (if necessary) and a housecurve.


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## smokarz (Apr 13, 2011)

finally, got all four of my subs in placed, ran some graphs.


and here are the graphs for the mains and subs crossed at various points (80hz, 100hz, 120hz.

what's the +10db boost between 25hz and 45hz? otherwise it looks like i am pretty much flat down to 10hz.

also, it seems that as i increased crossover point, i get a slight boost between 55hz and 110hz. is this how it suppose to behave?


i ran Audyssey and it sets my mains at -12db and sub at -15db.

it does seems to help flatten my response up to about 33hz and then steadily dropping off. not sure i like the Aud adjustments. any thoughts?


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

> what's the +10db boost between 25hz and 45hz? otherwise it looks like i am pretty much flat down to 10hz.
> 
> also, it seems that as i increased crossover point, i get a slight boost between 55hz and 110hz. is this how it suppose to behave?


With virtually any sub/room, the extension is a function of the sub, and the ups and down, peaks and troughs etc. are a function of the room. Or at least the place in the room you take your measurement.

Regards,
Wayne


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## smokarz (Apr 13, 2011)

thanks much wayne.

so do you think my response with audyssey is ok? should i proceed with a house curve?


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

If the purple trace is Audyssey, it looks like it’s already given you a house curve...

Regards,
Wayne


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## smokarz (Apr 13, 2011)

yup, that's the Aud curve. do you think i might benefit from a 'hard knee' house curve instead?

also, should i be concern with Aud setting my mains to -12db, and subs to -15db? thanks


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

> do you think i might benefit from a 'hard knee' house curve instead?


Best try one for yourself and see if you like it. :T

Regards,
Wayne


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