More confusion on house curves and target levels... - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 15 Old 08-06-08, 10:42 PM Thread Starter
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Re: More confusion on house curves and target levels...

OK, I lied (about that being my last question)....

.... What would happen if the input voltage into the BFD was exceeded besides the pretty red clipping light coming on and the output being distorted? Would the BFD be physically damaged in any way? The reason I ask is that, prior to figuring out that the LFE test tones on HD-DVE are screwed up (5dB too low.... a determination that Roger Dressler of Dolby helped me with), I had calibrated the trim of the AVR 5dB too high (I forgot that the adjustment must be made to the sub's gain, and not the AVR trim). As a result, I bottomed out the subs, and buried the needle on the BFD output (I can only guess what the input looked like). The subs seem to have weathered the storm quite well, but what about the BFD? I see in the docs that the maximum input for the BFD is +2dBV, and my AVR (Denon 2105) has a rated output of 1.2V. I have no idea how these two quantities relate (different units), or even if I am comparing the same thing.

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post #12 of 15 Old 08-07-08, 01:39 AM
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Re: More confusion on house curves and target levels...

Quote:
The subs seem to have weathered the storm quite well, but what about the BFD? I see in the docs that the maximum input for the BFD is +2dBV, and my AVR (Denon 2105) has a rated output of 1.2V. I have no idea how these two quantities relate (different units), or even if I am comparing the same thing.
The term dBV is a consumer level term that relates directly to the actual RMS voltage (0dBV reference level is 1 volt). So, +2dBV calculates to about 1.26 volts RMS.

Quote:
What would happen if the input voltage into the BFD was exceeded besides the pretty red clipping light coming on and the output being distorted? Would the BFD be physically damaged in any way?
No, you won't damage the BFD. It is more important though in digital devices to pay attention to clipping levels. They don't respond the same as an analog device. The distortion in a digital device is immediate and quite extreme.

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post #13 of 15 Old 08-07-08, 07:27 AM Thread Starter
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Re: More confusion on house curves and target levels...

Quote:
brucek wrote: View Post
The distortion in a digital device is immediate and quite extreme.
When the subs bottomed, there was simply the extremely loud "clack", but what would the distortion caused by the clipping sound like? My first guess was that the "clack" was due to digital clipping, so I recalibrated the BFD back down (under clipping input voltage), and bumped up the sub's gain to compensate. This time they could not have clipped, but they bottomed again and it sounded the exact same (nasty sound, though!). Since the "clack" was not clipping, and you describe clipping distortion as "immediate and extreme", what would I hear from the sub (that I did not hear either way)... did I dodge a bullet?

Peace... Vader

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One sub to rumble them all. One sub to shake them. One sub to humble them all. And in the darkness break them....
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Last edited by Vader; 08-07-08 at 07:35 AM.
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post #14 of 15 Old 08-07-08, 07:53 AM
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Re: More confusion on house curves and target levels...

Quote:
Since the "clack" was not clipping
It may be clipping of the sub amp though.

Or you may be simply exceeding Xmech of the sub driver.

Either way, you should stop doing it...

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post #15 of 15 Old 08-07-08, 07:58 AM Thread Starter
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Re: More confusion on house curves and target levels...

Quote:
brucek wrote: View Post
Either way, you should stop doing it...
I re-calibrated back down below clipping, and the AVR trim back using the known correct tones of SD-DVE. That's when I enlisted the help of Roger Dressler in determining that HD-DVE was at fault. Obviously, it has not come close since. I'm just relieved I didn't do more harm than was apparent. Thank you for your explanation (yet again)!

Peace... Vader

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One sub to rumble them all. One sub to shake them. One sub to humble them all. And in the darkness break them....
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