The BFD and my HGS-15 sub in the new HT room...

**Pat** · 22 January 2004, 18:18 Thursday

Pretty smooth Sonnie :T
Nice job 8)

Pat's Page

**Glen** · 22 January 2004, 20:05 Thursday

I hadn't heard of BFD until I started reading hear. I'm going to have to look into one of these. I think it would make a big difference withmy system.

Thanks for the info Sonnie.

**David Meek** · 22 January 2004, 21:22 Thursday

Glen, you are in the right place. Sonnie, especially, seems to be quite the poobah with the BFD - at least from some of the associated threads from a year or so ago.

David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

**Sonnie Parker** · 22 January 2004, 21:50 Thursday

Thanks guys! It's fun piddlin' around with the BFD.

Here's the before and after measurements along with the filter settings I used:

I post this info because sometimes it helps to be able to see what filters are used to get a better idea of what other BFD owners can try.

Notice the narrow bandwidths I'm using. It is important to use narrower bandwidths for cutting peaks especially if you are working near a dip. On 25hz, 28hz, and 31.5hz I used narrow bw's so that I would not be fighting the boost I gave 40hz. 5/60 on 28hz was cutting it close as it would still have some small effect on 40hz but not enough to hurt.

Many of the small filters I inserted were really not a "dire necessity" (wasn't that from Jungle Book?). I filtered frequencies such as 20/25/44/71 just to get a few decibels smoothed out although they probably would not be that noticeable for sub performance. They were more to make the line look prettier. Had I really needed another more serious filter I could have eliminated any of those. I could go on and on and keep adjusting more but provided this sounds okay there'll really be no need.

I could have also cut 20hz-28hz a little more and brought them down to 85db but then I like the house curve sound for movies and this give me that little extra umphhh for the extreme low end. There's nothing like the "feel" of bass. This sub toys with 16hz like it's nothing during the test measurements. It's a great witness for those that want a sub to play flawlessly down low.

SONNIE

Cedar Creek Cinema

DVD Collection

BFD Comprehensive Setup Guide

**Trevor Schell** · 22 January 2004, 23:14 Thursday

Not bad for a talking goat!!
:rofl:

You have to come up and tweak my subs!! :yesnod:

Trevor
My HomeTheater S.E.
Sonically Enhanced
C5

**David Meek** · 22 January 2004, 23:46 Thursday

Originally posted by The BFD Master

This sub toys with 16hz like it's nothing during the test measurements. It's a great witness for those that want a sub to play flawlessly down low.

Yeah! Velodyne owners unite - especially the HGS and FSR group. ;x(

David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

**Andrew Pratt** · 22 January 2004, 23:55 Thursday

Glen I have one if you want to see what they're like. I couldn't see myself owning a subwoofer without one now.

**Sonnie Parker** · 23 January 2004, 01:46 Friday

lol Trev! I'm back to a hillbilly now... but I can still be a talking goat too! Angibug named that nanny "horny" because she is the only one we've ever had with horns. She saw my avatar the other night and got mad at me for using it so I decided I better remove it before she sends me back to the goat shed.

David... united we rumble! :-y

Glen... I'd take Andrew up on the offer. I don't think you will regret spending so little for such a noticeable improvement you will most likely enjoy. Maybe you can go ahead and take some measurements and see what your response curve looks like. And don't forget to share it with us. You can download the excel workbook from my BFD link and if you need someone to host the graph pic for you, just let me know. Or take the measurements and post them and I'll fix you up a graph pic to use.

This is getting easier by the hour for you Glen.

SONNIE

Cedar Creek Cinema

DVD Collection

BFD Comprehensive Setup Guide

**ThomasW** · 23 January 2004, 18:31 Friday

Sonnie,

If there's ever a danger of your site going down let me know, because I have linked to it on posts literally all over the planet.

You are a hero to the BFD users of the world! ;x( ;x( ;x(

theAudioWorx
Klone-Audio

**Glen** · 23 January 2004, 23:25 Friday

Thanks everyone.

Andrew, I'll be sure to get in touch with you when I have some free time. I would love to see ( and hear ) your set up. Works just been to busy lately (I'm actually just getting ready to leave work after another 14 hour day - I think that's 3 for this week alone ).

**Sonnie Parker** · 25 January 2004, 19:54 Sunday

Glen... I blame my gray hairs on too many of those 14 hour work days.

ThomasW... I'm flattered with what you say. Thank you. Of course, I couldn't have done it without the help of Ken Bruce (brucek) and a few others contributed as well (all mentioned on the site). I hope the site stays with me for quite some time. We have our domain paid up through 2012 so maybe we can keep it hosted somewhere for that long. Fortunately the fellow that owns our ISP is a good friend of mine and he has never charged me for hosting our site.

Update on the sub measurements:

We decided to rearrange our seating in our HT room by moving the Lazy-boy's to the back row on the riser and having the black gliders with ottamans on the front row.

I was curious as to what effect this would have on the room acoustics... especially the bass. I watched a few concert DVD's since they have constant bass and was pleased with the front row listening. It didn't seem like much changed. When I moved to the back row it sounded a little heavier on every DVD but more noticeable on David Gilmour and Pink Floyd (both good for a wide frequency range in the low end).

Measurements confirmed there was a substantial boost at 40hz.... hmmmm... filter 5 was boosted 12db for my initial dip at 40hz.

Here's the measurements between the front and back row with the BFD settings I had as previously posted above. I didn't take any raw measurements. (Blue line = front row.)

...

So I took the 40hz boost out and made a few adjustments which still left me a little heavy on the back row for now but it sounds better. The front row didn't seem like it is sacrificing that much with the 40hz dip. I haven't worried with the upper freqencies yet.

When I get more time I'm gonna move the sub around a little and see what results I get... then fine tune with the BFD again. Maybe I can get a a more equal level between the front and back. Strategically placed bass traps may be in order.

SONNIE

Cedar Creek Cinema

DVD Collection

BFD Comprehensive Setup Guide

**Aussie Geoff** · 22 February 2004, 03:49 Sunday

Sonnie,

Looking at the "after" SPL figures and graph, I notice what seems to be a significant slope down in level from around 88 db at 18-22 Hz to 78 dB at 80 Hz and lower still after that.

I noticed something similar (though not as drastic) in your older posts on HTF.

My questions:
1) Is this deliberate?
2) Can this kind of continuous change in level be corrected using the BFD?
3) If it is deliberate - why?

UPDATE - Hunting round a bit more on HTF I found references to "House Curves" here and it seems to me that this is what you are creating - a 10 db slope down to deal with the Fletcher-Musnon effect on volume? ....

If so - shoud the sub be calibrated at the 80hz level with the speakers then? so this is effectively a slow boose up from 80 Hz?

Might be worth you putting some info on his on your great BFD guide???

Thanks

Geoff

**Bam!** · 22 February 2004, 09:34 Sunday

HI Sonnie!

Quite impressive!

How much does one of these gizmos go for

Thanks!

Bam!

**brucek** · 22 February 2004, 10:10 Sunday

If so - shoud the sub be calibrated at the 80hz level with the speakers then? so this is effectively a slow boose up from 80 Hz?

Geoff has touched on an important issue. I think after you've established and graphed a smooth response curve for your sub using the BFD (with a house curve), you should ensure its upper end (i.e 80Hz) still smoothly transitioned to the low end response of your mains.

It's good to graph your sub standalone and then on the same graph add a second line of your mains standalone response. As you've pointed out, the sub and mains levels at the crossover (60Hz, 80Hz etc) better be coming together at the same level. You may have to adjust the subs power amp "wholesale" level to raise or drop its entire graphed response to re-match the mains. You certainly don't want to touch the processors sub-out level at this stage because you've previously set that level to match the A/D input of the BFD. :roll:

Once this is done you can then add a third line to your graph of the mains + sub to ensure they work in concert at the crossover point.

brucek

**Sonnie Parker** · 23 February 2004, 12:54 Monday

It's interesting that I didn't realize I had my mains on when I was taking the measurements on the second graph. That 100hz peak is from the mains. I was able to tame that with the 100hz tone control on the pre/pro.

Ken... that's a good idea on measuring the mains alone although I'd have to have another eq to do anything on the mains side. I might could adjust the sub somewhat to match the mains at the crossover point but the only adjustment I have on the mains is 100hz.

Bam... I believe you can find a BFD for around $120-$140.

Geoff... You got it right... it's deliberate for the purpose of obtaining the house curve. I do reference this on the BFD page with links to discussions. You must have missed it. I didn't elaborate on it too much as those discussions do a good job of takin' care of it. It's strictly an option... some like the house curve and some like it flat.

SONNIE

Cedar Creek Cinema

DVD Collection

BFD Comprehensive Setup Guide

**brucek** · 23 February 2004, 15:54 Monday

Ken... that's a good idea on measuring the mains alone although I'd have to have another eq to do anything on the mains side. I might could adjust the sub somewhat to match the mains at the crossover point but the only adjustment I have on the mains is 100hz.

No, I didn't mean you should adjust or eq the mains. The only reason I suggest a standalone mains measurement is to establish a reference point on your graph so you can do a final 'wholesale ' level adjust (if necessary) on the sub amplifier after BFD equalization to ensure a smooth level transition at the crossover. If you have a large house curve, I see no other way to set the final sub amplifier level.

Here's the reason I say this:

Normally, without a BFD it's a fairly easy task to set levels. You use the speaker level adjustment trims on your processor along with its internal tones and a RadioShack SPL meter. You start at an initial 'zero' dB on all the trims and then adjust a few dB up or down on your mains , center and surrounds depending on your room. Usually you'll leave the processors sub out level at zero and compensate for SPL level with the subs amplifier volume level. Easy.

Now add a BFD with its input level sensitive A/D converter and you have to use the method explained on your web site to trim the processors sub output level to compensate for this problem. I'll paraphrase what you said on your web site below for anyone interested - Sonnie, just skip over this section...

------------------------------ IN PART: -----------------------------
To take maximum advantage of the dynamic range provided by the analog to digital converter in the BFD or any ADC for that matter, you need to provide it with a maximum input signal level that takes advantage of the greatest number of bits to represent the resultant voltage samples.
If the range from your weakest signal to the strongest signal was only half the required maximum input level, you would be robbing yourself of dynamic range and subsequently increasing your signal to noise level. To get the most out of this system you would like the maximum signal sent to the BFD to "just" not turn on the red LED. If the yellow LED comes on in explosions etc, that would be fine. I know this to be true, because I have taken this unit apart and fed it signals and monitored the clipping levels in relation to the LED's - they're fairly accurate.

Since we are feeding the BFD a variable line level whose maximum is actually set by the volume control of the processor and not a "fixed" line level as from a CD player, careful setting of the sub out level of the processor is necessary. Every user is different. Some people like to listen at reference all the time, some like it lower. Each of these people will have different maximum levels being fed to the BFD. You need to use your highest dynamic range device, which would be a DVD and play it as loud as you normally would and when an explosion or loud bass scene occurs, check the LED level on the BFD. Set the processor sub out level to just be turning on the yellow LED once in a while. Now you know that at least when you are playing your system at this high level and you have a worst case DVD playing with its LFE plus redirected bass, that the maximum signal will not overdrive the digital input of the BFD. You'll also know the softest signals will have the least quantization error possible for the ADC system.

Note that the BFD IN/OUT switch will enable and disable your filters with its’ light "ON" and "OFF" respectively. In these two conditions the LED indicators are showing the BFD's output level. But, if you push and hold the IN/OUT switch and it begins flashing, you bypass the filter section completely and the LED indicators are showing input level. This is the condition to set it up in and that I am discussing above

Now once that's set, and your playing a quiet movie or you're watching satellite, you'll probably be operating in a nice -10db LED area.
---------------------------------------------------------------------------

Anyway, so now that you've set the processors sub-out trim, you have to use your subs amplifier volume to set your overall sub level. And that's fine, but if you now go through the process of equalizing the sub output with the BFD, (particularly if you have a large house curve slope), are you going to rely on the processor internal test tones to set that sub amplifier level?
I feel the large slope on the response of the subwoofers output will skew the results. I know this because I've tried it. If you have a large house curve and you use the internal tones to set your sub level, you can have a nasty jump in SPL level at the crossover.

To be sure that the audio SPL level at the crossover point between the mains and sub are smoothly matched, I think you have to graph it.

So after you've completed your initial processor trims, then you've set up the BFD input level, then you've equalized with your BFD filters, then I think to set the final level of your sub amplifier, you first do a 'mains only' response and graph it and then (without altering any volume levels), do a sub only response and graph it on the same sheet and see if at the crossover area the level is about the same. It may have a jump up or down and should be compensated by raising or lowering of the sub amps volume level. If you do this you'll have a very smooth transition over the entire low end............ :roll:

brucek

**Sonnie Parker** · 23 February 2004, 19:09 Monday

Very good info Ken and it makes good sense.

Thanks!

SONNIE

Cedar Creek Cinema

DVD Collection

BFD Comprehensive Setup Guide

The BFD and my HGS-15 sub in the new HT room...

The BFD and my HGS-15 sub in the new HT room...

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