# Is time delay significant?



## JoeESP9 (Jun 29, 2009)

I'm planning on getting and using a FBQ2496 to Eq my sub woofers. They are crossed over at 80Hz using an electronic crossover. 
My question is:
The high pass section of my crossover feeds a pair of tube mono blocks driving my ESL's. The low pass output from the crossover will go to the FBQ2496 for EQ and from there to two Crown XLS402's. Should I have any concern for the time delay caused by the FBQ. Will the time delay if any have any effect on the phase in reference to the main (high pass) signal?


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## Kal Rubinson (Aug 3, 2006)

Hard to say. I do not know what the latency of the FBQ is but figure that each millisecond of delay is roughly equivalent to a foot of displacement.

Kal


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## JoeESP9 (Jun 29, 2009)

Thanks for the confirmation Kal. I figured it was about a foot per millisecond. Now the question is how much latency is in the device and how much or little is audible. 

If it's audible what can be done to correct it?

Doesn't a delay cause phase differences?

How can I easily cause a couple of milliseconds delay in the feed to my main speakers?

Has no one else considered this before now?

If so, what was done to cure this?

Is this a problem that doesn't really exist?


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## Kal Rubinson (Aug 3, 2006)

JoeESP9 said:


> Thanks for the confirmation Kal. I figured it was about a foot per millisecond. Now the question is how much latency is in the device and how much or little is audible.


Should be in the specs but, if not, ask Behringer.



> If it's audible what can be done to correct it?


Either move the sub:heehee: or......



> How can I easily cause a couple of milliseconds delay in the feed to my main speakers?


set the distances on your main prepro/AVR for your sub a similar distance farther. Audyssey, for example, will do this automatically.



> Has no one else considered this before now?
> 
> If so, what was done to cure this?
> 
> Is this a problem that doesn't really exist?


Happens with almost every powered sub.


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## gsmollin (Apr 25, 2006)

With most AVRs, the setup will compensate for this. You should know that the delay through the subwoofer itself is worth about 19 ms, with or without an FBQ there. I didn't notics much of a change when I added the FBQ, about 1 ms perhaps.


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## JoeESP9 (Jun 29, 2009)

Why is there a delay through "almost any" powered subwoofer?

There shouldn't be any delay discrepancies in my two channel system. I don't use an AVR or have any kind of receiver. Although I have a Lexicon processor it's only used for MC and surround sources. My question refers to how much latency is inherent in any Behringer BFD.


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## gsmollin (Apr 25, 2006)

There is a delay through all speaker drivers, and it increases with the size and mass of the cone and voice coil. You can see the effect of this in some speaker enclosures where the front board is tilted back or stepped.

Sub woofer moving mass is usually many times larger than in the tiny "woofers" used in modern speakers. It has a longer time delay as well.


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## JoeESP9 (Jun 29, 2009)

The time delay your speaking of is not because of cone or voice coil delay. It's a result of different distances to the base of the cone (or dome) where the voice coil is located. The easiest illustration of this is Vandersteen, Dahlquist DQ-10's or Theil speakers. The physical positioning of the voice coils is such that the voice coils are all the same distance from the listener. The Vandy's and DQ-10's use stepped cabinet sizes and staggered positions for each driver. Theil uses a sloping front with a relatively complicated crossover that also compensates for crossover induced phase changes. 

With large cones and small dome tweeters on a flat baffle the difference in voice coil distance (from the listener) can be a foot or so. That's roughly 1 millisecond. If the latency (delay) in the Behringer is more than a few milliseconds (2 or 3) it's probably more than I'm willing to deal with.


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## gsmollin (Apr 25, 2006)

I don't think the time delay is more than 1 ms in the BFD. In a subwoofer, just the 80 Hz crossover introduces a time delay of 12 ms to the signal. I expect you are asking about any non-minimum phase effects that the BFD would add in addition to the linear phase effects caused by the filters and crossovers. Once again, my room equalization changed the distance to the subwoofer by 1 foot when I added the BFD, so that corresponds to 1 ms.


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## JoeESP9 (Jun 29, 2009)

That's the sort of answer I was looking for. A millisecond of latency is something I can deal with. It will apply only to my front subs. Everything else in my front signal chain from preamp outs is analog including an electronic crossover. There are no passive crossovers so I don't have any other latency issues.

A voice coil driven speaker should have no latency issues. Passive crossover components (caps and coils) are what causes delay in speakers. 

I'm thinking of building a ClassD Audio, Class D amplifier kit. It will be used to drive my ESL's. There is a certain amount of latency inherent in digital amplifiers. I'm guessing (and hoping) it will balance out the latency in the Behringer.


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