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Can u do this with a BFD ?


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#1 of 22 OFFLINE   John-Tompkins

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Posted August 01 2004 - 11:24 PM

...It is a TWO channel eq right ? ..can you eq one sub on one channel and then eq another sub with a different set of parameters on the other channel and use them both at once ?. One channel will be getting an lfe signal and the other channel will be getting everything from 80 hz and down from the main l/r channel.

Im wanting to eq my main l/r speaker's woofer's (wired in paralell as one speaker) on one channel of the bfd and then the lfe sub (svs) on the other channel of the bfd...I was gonna get two bfd's but thought maybe I could do it all from one bfd.Any help would be apreciated.
Do I need one or two bfd's?

#2 of 22 OFFLINE   Brian Fellmeth

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Posted August 02 2004 - 01:05 AM

You can do this with one, two separate signal paths with 12 filters each to use.

#3 of 22 OFFLINE   John-Tompkins

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Posted August 02 2004 - 01:34 AM

Thanks much !

#4 of 22 OFFLINE   GrahamT

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Posted August 02 2004 - 02:01 AM

Yep, one BFD will do. Check out this site if you haven't seen it before. It helped me out a lot.
http://www.snapbug.ws/bfd.htm

#5 of 22 OFFLINE   Chris Tsutsui

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Posted August 02 2004 - 07:13 AM

That's not a bad idea... but if you wire your L/R Mains woofer channels together, what about the stereo bass that comes from them. (not that it's probably a big thing to lose)

But why not let the receiver crossover the Mains with the LFE, and leave out the BFD from the Main's signal path? I guess if there are some peaks in the freq. response that your mains play then "ideally" I'd get 2 bfds.

One BFD for your mains, and another BFD for the sub. This way you can EQ each main channel and maintain the stereo bass. Then use your 2nd BFD to EQ your LF sub(s).

Of course... you'd have to justify $100+ for that small difference.. heh


#6 of 22 OFFLINE   ChuckRG

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Posted August 02 2004 - 07:46 AM

Another question. I have an audio buddy who is not particularly technically saavy and would be interested in the Auto EQ function of the Berhinger.

Does the auto correct function of the Berhinger 24/96 create a correction using the parametric EQ function or the graphic EQ function (or both?)

#7 of 22 OFFLINE   John-Tompkins

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Posted August 02 2004 - 11:15 AM

Quote:
But why not let the receiver crossover the Mains with the LFE, and leave out the BFD from the Main's signal path? I guess if there are some peaks in the freq. response that your mains play then "ideally" I'd get 2 bfds.

My situation is a bit different and lends itself well to just one bfd I think. I have NHT T5 speakers for my main l/r channels. The T5 speaker consist of an M5 satellite and a B5 bass module and they are connected via an X1 controller ( active crossover with phase, adjustable cross point for low and high pass, boudary eg, volume control etc.) NHT did this for maximum flexibilty and it works great for room integration for a full range speaker.

The B5 bass module is only 12 ohms, so NHT reccomends that you run both b5 modules in paralell for a 6 ohm load ( remember that below 80 hz isnt locatable bass anyway)..Ive tried it both ways and couldnt tell any differences whatsoever.

Also I dont like to run the lfe svs's when I listen to sacd/dvd-audio or redbook, rather just run my T5s full range.So what I can do is:
Run main l/r full range from pre-pro to X-1 controller.
Send low pass (80 hz and below) to the BFD for eq.
Send 80 hz and above straight to my amps..The bfd never touches anything 80 hz and above.
Then just eq my lfe svs subs on the other bfd channel Posted Image
Everything should be good to go..for music AND movies

#8 of 22 OFFLINE   Greg Bright

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Posted August 02 2004 - 11:23 PM

Do your SVSs' have high pass outputs (not speaker level)? If so that would lend itself to yet another way of hooking up your BFD, as I have done.
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#9 of 22 OFFLINE   Wayne A. Pflughaupt

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Posted August 03 2004 - 12:03 AM

Quote:
So what I can do is:
Run main l/r full range from pre-pro to X-1 controller.
Send low pass (80 hz and below) to the BFD for eq.
Send 80 hz and above straight to my amps..The bfd never touches anything 80 hz and above.
Then just eq my lfe svs subs on the other bfd channel
Everything should be good to go..for music AND movies
Sounds like you have a handle on the connection scheme, John.

You’ll just have to keep in mind that equalizing multiple low frequency sources – by that I mean those that are placed at various places around the room – is difficult. You may well find that once you EQ the B5 and SVS separately, and then fire them all up together, that it’s a whole new ball game.

EQing both B5s with a single equalizer should be fine if you have symmetrical placement in the room, but if you don’t it may be a problem. Take my situation, for instance, I have one main a few feet from a corner, and the other next to an open doorway. Naturally, the former emphasizes the bass more so than the latter. In that situation you couldn’t expect a single equalizer to do the job.

Since you don’t use the subs for music listening, that will be to your advantage. This way you can pay the most attention to getting the B5s accurate. If you loose some accuracy when the SVS is kicked in for movies, it won’t be catastrophic. Most low frequency material there is merely booms and rumble from explosions and things.

Regards,
Wayne A. Pflughaupt

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#10 of 22 OFFLINE   John-Tompkins

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Posted August 03 2004 - 01:51 AM

Quote:
You may well find that once you EQ the B5 and SVS separately, and then fire them all up together, that it’s a whole new ball game.


Hello Wayne,
This is the 64,000.00 question. I orignally was gonna eq the b5's and svs's together (both on) But I was told that since the lfe is a seperate channel that cancellation wouldnt be much of a problem since both channels wouldnt be playing the same signal (lfe and main l/r bass)..and that I would be much better off eq-ing them seperately..Whats your take on this ?

Quote:
EQing both B5s with a single equalizer should be fine if you have symmetrical placement in the room, but if you don’t it may be a problem


Luckily (or unluckily really ) I have a 14X14X9 room which isnt good from a standing waves point of view..But it does make all my speakers have a rather symmetrical placement. My main L/R are both at equal distance from the back and side walls and since I have a projector Im able to place the b5's woofers inward pointed at each other.

#11 of 22 OFFLINE   Wayne A. Pflughaupt

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Posted August 03 2004 - 06:07 AM

Quote:
I orignally was gonna eq the b5's and svs's together (both on) But I was told that since the lfe is a seperate channel that cancellation wouldnt be much of a problem since both channels wouldnt be playing the same signal (lfe and main l/r bass)..and that I would be much better off eq-ing them seperately…
Well, someone’s a little confused. The only kind of cancellation the receiver can generate is electrical – i.e., polarity, if the (+) and (-) were inverted on one of the signals (there could out-of-phase signals originating further upstream in the program source, but that’s a whole ‘nother story).

Even if this “separate signals” assertion had some truth, the fact is that the low frequency signal from the LFE vs. the main channels is not appreciably dissimilar. In practice, cancellation has nothing to do with the fact that you’re dealing with two separate signals. It’s the frequency content of the signals that matters, primarily low frequency content.

For instance, consider a best-case scenario where the two signals are complete separate and distinct, from say, a bass guitar and an electronic keyboard duplicating the same notes. Reverse the polarity of one of the signals, anywhere in the signal chain, and you’ll have cancellation. Sure, you’ll still have the the distinct sounds of the two instruments that originate in the upper registers, that are responsible for the signature “texture” of the instruments - i.e., the harmonics and so forth - but the low frequency fundamentals will be lost.

When low frequencies go from the electrical to acoustical stage in the form of sound waves in the room, cancellation then becomes an acoustical issue, not an electrical one. The driving force then becomes room boundaries and the low frequency generators themselves.

To put it in simple terms, there is cancellation at the halfway point between a low frequency generator and a boundary. The physical distance between the two determines at what frequency the cancellation occurs (mathematical formulas and all that). This one reason why it is usually recommended to place a sub in a corner – it minimizes the number of interacting boundaries to the two farthest walls and the ceiling.

Similarly, the halfway point between two low frequency generators behaves like a boundary: There will be cancellation at a specific distance-related frequency. As you can imagine, the more low frequency generators you add, the more distance/boundary issues - both acoustical and physical - you have to reckon with.

Quote:
Luckily (or unluckily really ) I have a 14X14X9 room which isnt good from a standing waves point of view..But it does make all my speakers have a rather symmetrical placement. My main L/R are both at equal distance from the back and side walls…
That’s good – you should have no problem equalizing the two B5s with a single equalizer.

Regards,
Wayne A. Pflughaupt

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#12 of 22 OFFLINE   John-Tompkins

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Posted August 03 2004 - 07:33 AM

So would it be best to do the eq-ing with both the lfe subs and b5's active ? ..I guess this may be best for movies as this would be the only circumstance that would have both lfe and b5s going.
If I eq them seperately I may in fact be making my bass for movies worse and not better ?
I should add that my lfe svs subs are in the same corner as the right b5 woofer ( maybe only 1~2 ft or so away)

#13 of 22 OFFLINE   Wayne A. Pflughaupt

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Posted August 03 2004 - 10:10 AM

In your situation, since music and the B5’s are what’s most important to you, EQ them and the SVS subs separately. EQ both systems with the M5 L/R mains on - this will allow for the EQ to make some compensations for phase issues caused by the crossovers (typically these show up as response deviations in the first octave or so above and below the crossover frequency). Don’t forget to dial in an appropriate house curve.

At that point, when you add them both together, if new response deviations show up that weren’t there before, try do deal with them as best you can with the SVS EQ channel only (leave the B5 channel alone). You may not be able to get “perfect” combined response this way, but it does insure that you’ll be getting the best from the B5s when you use them alone.

After you’re satisfied with your combined response curves, you can adjust the respective gain levels of each system as accordingly.

Regards,
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#14 of 22 OFFLINE   John-Tompkins

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Posted August 03 2004 - 11:23 AM

Thanks Wayne that makes sense.

I would like to keep the svs's in one corner but Ive noticed by running sine waves that I get the flatest response having them split up with one 1/3 from the front wall and the other 1/3 from the back wall (it kinda evens out a fairly large 50hz valley I have...What it be dum to keep them in the corner (where I really want them) and just eq them...or should I split them up as to start with a better curve before eq-ing ?

Side question for anybody, How do you take the excel graphs and put them in your posting here on htf ?

#15 of 22 OFFLINE   Greg Bright

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Posted August 03 2004 - 01:01 PM

Quote:
Ive noticed by running sine waves that I get the flatest response having them split up with one 1/3 from the front wall and the other 1/3 from the back wall (it kinda evens out a fairly large 50hz valley I have


Russ Herschelmann of Ultimate AV is against corner placement unless you have only one sub. He would probably find that your results are correct. Corner placement does however maximize output. He believes that multiple subs should be located around the room essentially in the positions you found.
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#16 of 22 OFFLINE   John-Tompkins

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Posted August 04 2004 - 11:14 PM

Russ Herschelmann seems to have company in his opinions. Im gonna keep the svs's split up along the walls becuase the bfd cant do much about the valleys thats caused by stacking them in a corner.

I recieved the bfd and the interface seems fairly logical but I have a couple of questions or concerns.

I realize that there are valleys that cant really be corrected by the bfd but the really weird thing is I have a couple of peaks (28,45 hz) that no matter what, I cant seem to get rid of...Ive tried settings these freq's on the bfd, lowering the gain, messing around with the bandwidth but no matter what these two particular peeks just wont go away ???.... ( I should note that if I move the spl meter a foot up towards the celing or down towards the floor that the volume is waaay lower, but at sitting level the volume just stays the same (louder) no matter what I seem to do with the bfd )

Also Im not really clear after reading snapbug about how you process two different signals at once...Should I use couple mode ? or not use couple mode and set individually..The only time I can get both the L and R buttons lite at the same time is in couple mode, But the manual states that whatever the last individual signal that was edited will be COPIED to the other channel as soon as you put it in couple mode ?

#17 of 22 OFFLINE   Wayne A. Pflughaupt

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Posted August 05 2004 - 08:39 AM

Quote:
Russ Herschelmann seems to have company in his opinions.
Really? Think about it, John: Herschelmann is a professional home theater consultant. He deals in high-end installations in custom-built rooms where everything has been optimized from the ground up. If he feels he needs four more subs to get what he wants, I’m sure the client says, “I’ll have them here tomorrow.”

Does this situations relate in any way to yours?

Quote:
I get the flatest response having them split up with one 1/3 from the front wall and the other 1/3 from the back wall (it kinda evens out a fairly large 50hz valley I have...
How about the other important sub performance parameters, like output and extension?

“Flattest response” isn’t necessarily the goal to shoot for if you’re going to equalize. When equalizing, the goal, IMO, is “response that can best be equalized.” By that I mean peaks and dips that have a symmetrical shape. These are easiest to equalize because the bandpass filters of an equalizer also have a symmetrical shape. Response dips that are not symmetrical – for instance, fall gradually on one side of a peak, and rapidly on the other - are more problematic to equalize because they require at least 2-3 filters each.

It’s fairly well established that in most rooms you’ll get the highest output and best (lowest) extension with corner placement. Herschelmann doesn’t care if placing subs anywhere but the corner nets less output or extension. He can simply order more subs to compensate.

Response in the corner locations might not always be the flattest – in fact, you can expect a severe spike or two – but typically the response you do get is easier to equalize. In a perfectly symmetrical room, splitting the two subs into two front corners is viable, but co-locating them in the same corner will net an additional 3dB gain. That’s essentially doubling acoustical power.

Quote:
...becuase the bfd cant do much about the valleys thats caused by stacking them in a corner.
Sez who? Have you seen the response graph on Sonnie’s BFD Comprehensive Set-Up Guide web page?


Posted Image


Quote:
...the really weird thing is I have a couple of peaks (28,45 hz) that no matter what, I cant seem to get rid of...
Well, since you’ve gone with asymmetrical placement, the two SVS’s now have their own signature room response curves. You’re going to need an EQ channel for each of them.

You already have your work cut out for you dealing with the two B5s in separate locations, and the SVS’s. You’re only going to complicate things even more by splitting the SVS’s, especially if you go with asymmetrical placement. As you’ve already seen.

Regards,
Wayne A. Pflughaupt

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#18 of 22 OFFLINE   John-Tompkins

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Posted August 06 2004 - 07:01 AM

Wayne,

You make some good points and Im not saying I disagree..I am saying that now that Ive been messing around with the bfd that my head is spinning Posted Image

The freakin phase control and distance settings has a HUGE effect on where my peaks and valleys are to begin with...Im just not sure where to start the distance and phase out before bfd ??

There seem to be sooo many variables...

To your point, I have a small room and 4 subs so I dont really need the extra spls..but Im gonna go ahead and put them both in the corner as you suggested and go from there (It looks must more asthetic anyhow).

I got everything fairly flat BUT I think I had to increase the gain at to many spots,,instead of decreasing the other areas...plus I used 10 filters for the b5's..probably to many

#19 of 22 OFFLINE   Greg Bright

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Posted August 06 2004 - 09:38 AM

Yes, Wayne's reply was incredibly well thought-out. Fully through-composed with no repeats. My experience with the BFD has indicated that I should NEVER use the gain. Just a little bit and those nasty red lights start blinking. And I've heard it (distortion), too. My technique has been to turn the gain up on the sub until the valleys aren't TOO bad (except for the real for-sure nulls) and the lowest Hz the sub will reasonably produce is more or less flat with the rest of the spectrum. This may make your peaks unbearable when 20 Hz is at 70-80 dB. Then its cut, cut, cut. Doesn't stress out the BFD, and it gives you lots of breathing room to experiment and adjust more to your liking.

Greg Bright
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#20 of 22 OFFLINE   Eric:F

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Posted August 07 2004 - 12:45 AM

hi wayne and greg,
i have a svs pb2+ in the main ht room and a hsu vft3-mk2 in the family room set up.
i want to eq both subs independently with one bfd.
all gear is centerally located and controled via rf link so cable logistics aren't an issue.
can you describe the bfd set up that will allow this.
i don't think i want to be in "couple" mode.
the manual is a bit vague about using both channels independently.
thanks,
eric


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