FBQ2496 delay/time sync issue - AVS Forum
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post #1 of 14 Old 10-31-2008, 04:48 PM - Thread Starter
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Hi,
I just got my FBQ2496 this afternoon!
Question is, once I set it up, being that its taking the analog signal from my Reciever/sub out, digitizing it, tweaking it, then re-analoging it, then sending it to my subs amp, then out to my subs; how can I adjust the delay in the rest of my system to accomodate the delay that will be introduced to the LFE after all this processing?

System:
Yamaha RX-Z1 (all speakers crossed over at 90hz and NO distance setting for subs)
Paradigm studio reference (40's,cc570,adp590's)
SVS cs25-31plus X2 / 1200watt samson 2ch amp
FBQ2496 EQ for subs (everything below 90hz)

Thanks for any suggestions you might have!
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post #2 of 14 Old 10-31-2008, 05:50 PM
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Typically the delay created by a BFD is ~1ms, and not many people find that problematic in the passband where a sub operates.

If your receiver doesn't have a delay setting and you're sensitive to this amount of delay know 1ms = 1ft of distance. That tells you how much you need to move things.
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post #3 of 14 Old 10-31-2008, 07:28 PM - Thread Starter
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Quote:
Originally Posted by NoBS View Post

Typically the delay created by a BFD is ~1ms, and not many people find that problematic in the passband where a sub operates.

If your receiver doesn't have a delay setting and you're sensitive to this amount of delay know 1ms = 1ft of distance. That tells you how much you need to move things.

Thanks for the info! I could move my subs a foot forward, but then I'd have to move my mains further apart and this would impede foot traffic in the hallway. One thought I had was to send back the FBQ2496 in exchange for the FBQ3102 link: http://www.behringer.com/fbq3102/index.cfm?lang=ENG
...which is analog which should interject no delay if I'm not mistaken?!?
It doesn't operate as a parametric EQ, but I allready know my problem frequencies and approximate the problem areas. It also has a handy little bass/sub output/low cut feature.
What would you suggest?
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post #4 of 14 Old 10-31-2008, 08:19 PM
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FYI - a 30hz wavelength is over 37 feet long. Thats why it does not really matter if there's a short delay in sub frequencies.
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post #5 of 14 Old 10-31-2008, 08:42 PM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

FYI - a 30hz wavelength is over 37 feet long. Thats why it does not really matter if there's a short delay in sub frequencies.

So, if my listening room is: 17(L) x 12.5(W) x 8(H), freq. in that range would essentially bounce off the wall behind the LP and collide with the forward waves and possibly cancel them, or distort them, or increase certain frequencies, such as my problem with the 60hz range?!

Aside from that, regardless of the wavelength, wouldn't speed of the wavelength/pressure reaching you be of more importance than the distance or length of the wavelength/pressure?

If the crest of one wave at 90hz hits you, and then the crest of a 25hz wavelength hits you at a different time, wouldn't that still be a delay? And possibly one that is noticable in the sound?

Also, since the wavelength of 90hz is considerably shorter, wouldn't this still be a problem since my cross-over is fixed at 90hz?

Thanks a bunch for the input!
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post #6 of 14 Old 10-31-2008, 09:00 PM
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Quote:
Originally Posted by tidan View Post

So, if my listening room is: 17(L) x 12.5(W) x 8(H), freq. in that range would essentially bounce off the wall behind the LP and collide with the forward waves and possibly cancel them, or distort them, or increase certain frequencies, such as my problem with the 60hz range?!

Sure, that's essentially the cause of room modes

Quote:
Originally Posted by tidan View Post

Aside from that, regardless of the wavelength, wouldn't speed of the wavelength/pressure reaching you be of more importance than the distance or length of the wavelength/pressure?

No - the speed of sound is fixed; at a specific barometric pressure.

Quote:
Originally Posted by tidan View Post


If the crest of one wave at 90hz hits you, and then the crest of a 25hz wavelength hits you at a different time, wouldn't that still be a delay? And possibly one that is noticable in the sound?

Also, since the wavelength of 90hz is considerably shorter, wouldn't this still be a problem since my cross-over is fixed at 90hz?

Thanks a bunch for the input!


you dont need the "crest" of a wavelength to hit you. This is why you can hear a 20hz tone in a small room.
Don't forget that if your crossover is set at 90hz, your sub is 6 db down at that frequency. Plus, it's at about 12 feet long; that's still not much of a phase delay.
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post #7 of 14 Old 10-31-2008, 09:36 PM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

Sure, that's essentially the cause of room modes



No - the speed of sound is fixed; at a specific barometric pressure.




you dont need the "crest" of a wavelength to hit you. This is why you can hear a 20hz tone in a small room.
Don't forget that if your crossover is set at 90hz, your sub is 6 db down at that frequency. Plus, it's at about 12 feet long; that's still not much of a phase delay.

So, the speed of sound being relatively constant, wouldn't that still put my bass sounds out of phase slightly with my above-90hz sounds? I understand that there won't be any cancellation due to the impossibility of 180 degree phase issue because the wave lengths are too long to allow that in these circumstances, but won't waves being even 20 degrees out of phase create excess's or peaks that would otherwise not be there?
Brings to mind the ole 3 phase home electricity wiring concept where you throw a few hot leads slightly out of phase to help create a long crest to a wave (EM in this case) which helps start electric motors and other large electrical devices. ;-)
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post #8 of 14 Old 11-01-2008, 04:57 AM
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interesting corellation, but with electricity remember you're dealing with only one frequency. With music, or sound in general, you're dealing with numerous frequencies so they're never really in phase with each other.
It's like when you change the phase on your sub 180 degrees; you are only affecting the specific frequncies that both your mains and sub are playing - making them louder by increasing the peaks or cancelling them by negating the peaks. But it's only a small range that's affected which is why there's not really a huge difference usually.
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post #9 of 14 Old 11-01-2008, 08:13 PM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

interesting corellation, but with electricity remember you're dealing with only one frequency. With music, or sound in general, you're dealing with numerous frequencies so they're never really in phase with each other.
It's like when you change the phase on your sub 180 degrees; you are only affecting the specific frequncies that both your mains and sub are playing - making them louder by increasing the peaks or cancelling them by negating the peaks. But it's only a small range that's affected which is why there's not really a huge difference usually.

So, depending on octave that your bass management crossover within, you would have a relatively narrow range of frequencies that overlap and that could have a phasing issue, right?
However, I notice that my mains will still produce stuff down to 10 hertz (at a dramatically lowered db level) along with my subs even though my mains are set to small (as are the rest of my speakers) and the LFE is set to "sub only". So, in theory, there may be many frequencies which end up overlapping, even if those coming from the mains are very minute - it may still adversly affect the sound stage/quality, wouldn't you think?
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post #10 of 14 Old 11-01-2008, 08:24 PM
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10hz? are your mains sealed?
nonetheless, my answer to your last question is, in a word, no; I don't think the 1ms delay in sub frequencies would adversely affect your sound. There are just too many other factors involved, and it's too small of an effect to have any noticible difference; in my opinion.
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post #11 of 14 Old 11-01-2008, 10:18 PM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

10hz? are your mains sealed?
nonetheless, my answer to your last question is, in a word, no; I don't think the 1ms delay in sub frequencies would adversely affect your sound. There are just too many other factors involved, and it's too small of an effect to have any noticible difference; in my opinion.

Thanks for the response! No, my mains aren't sealed (paradigm studio 40's), but the drivers are still moving at ten hz even though the system is crossed over at 90. The subs still produce intense vibrations at 10, but the mains are only moving their cones - no vibes or sound that low.

I guess in order for the mains to actually produce that long of a wavelength they'd have to be sealed, right? Otherwise they'd cancel themselves out via the port - i.e. the heavy long pressure wave would be negated from the opposite pressure wave via the port - depending on the ventricle length the port was routed thru - correct?
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post #12 of 14 Old 11-02-2008, 07:50 AM
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Well, sealed speakers roll off gradually (12db/octave), whereas ported speakers theoretically roll off at 24db/octave under the tuning frequency, but really anything under the tuning frequency is garbage since the driver is basically unloading at that point due to the port.

Your receiver crossover is likely rolling off the mains at 2nd order (12db/octave - does not include their own rolloff)
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post #13 of 14 Old 11-02-2008, 08:03 AM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

Well, sealed speakers roll off gradually (12db/octave), whereas ported speakers theoretically roll off at 24db/octave under the tuning frequency, but really anything under the tuning frequency is garbage since the driver is basically unloading at that point due to the port.

Your receiver crossover is likely rolling off the mains at 2nd order (12db/octave - does not include their own rolloff)

The studio40's (my mains) have a listed freq. response at 62 - 22k - which should be pretty flat as paradigms are pretty good about that. So anything below 62 is probably allready dropping quite fast. That combined with my cross over dropoff would probably render anything at or below 62 pretty undescernable. I think?!?

Man, now I really don't know if I should get the analog eq or stick with the digital. Do analog EQ introduce any delay? Namely the behringer analog EQ (FBQ3102)? I asked behringer on the phone the other day but they didn't know.
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post #14 of 14 Old 11-02-2008, 08:58 AM
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Quote:
Originally Posted by tidan View Post

Man, now I really don't know if I should get the analog eq or stick with the digital. Do analog EQ introduce any delay? Namely the behringer analog EQ (FBQ3102)? I asked behringer on the phone the other day but they didn't know.

There are issues involved with using any type of EQ (analog or digital) FAR more problematic than an inaudible 1ms of delay.

So do as you were told days ago, keep the FBQ2496. Parametric EQ is the only type of EQ that allows accurate targeting of the problematic frequencies and control of the filter 'Q'.

Now find something else to obsess about... PLEASE!
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