# FBQ2496 input clipping



## pierreye (May 6, 2010)

Guys need some help on the setup of BFD.

My equipment as below:
Receiver Onkyo 805 (volume at -5db and LFE level at 0db).
RCA cable with 1/4" Mono plug to FBQ2496 left channel input. -10db input switch is on.
BFD Output using 1/4" Mono plug and RCA cable to ED A7s-650 subwoofer.

I had manually EQ the sub and the main channel with a flat freq response. I try to run REW freq sweep from different listening volume and the response curve is consistent.

When I try out some scene, I found out the input level is over saturated (red clip is on). Example, Iron Man and Kung Fu panda skidoosh scene. I try to turn down the sub level input to -6db and it still show clip.

I found out another problem when the peak is overloaded, it'll overflow to the second channel. I'm using Left channel for my sub tuning and when it hit the peak too high, not only the left channel input light up RED (clip), the right channel also show the input signal going up (sometime hitting RED). Anyone encounter this problem? I suspect it's the ground shield that is connected to -ve wire. Will try out some custom cable with -ve disconnected at RCA end. I don't think my unit having problem as I had 2 units and both show the same behaviour. Please note that my FBQ2496 firmware is ver 1.1. Any newer version than v1.1?

Scene to test out: Iron Man in the opening scene where Tony is ambush. This scene will show major clipping.


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## Wayne A. Pflughaupt (Apr 13, 2006)

All you need to do is reduce the receiver’s sub output until you’re safely out of clipping, with the meter registering maybe -10 to -12. Then turn up the sub’s gain to compensate. :T

If that won’t work for some reason, just switch over to the +4 setting.

Regards,
Wayne


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## pierreye (May 6, 2010)

Thanks for the reply. I do try to reduce the sub level to -8db but it still occasionally clip my input but the gain on subwoofer is very high, around 2-3 o'clock. Sorry to ask but why +4db would help? I thought normally it should be -10db.

Also, do you have any idea when the clip happen, why the signal will overflow to the second channel (right channel as I use left channel for sub EQ).


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## Wayne A. Pflughaupt (Apr 13, 2006)

The rear-panel switches accommodates either professional +4 dBu or consumer -10 dBV nominal operating ranges. The +4 setting switches the operating rage upwards and can handle a signal that is 15+ dB stronger than the -10 setting (see graph below).

The two ranges can be thought of as an _internal gain structure._ Since there is such a severe difference between pro and consumer signal levels, one gain structure cannot be optimized for both ranges. In other words it’s impossible for the equalizer to deliver, at the same time, the best headroom and the lowest noise floor from a single internal gain structure. The higher-level (professional) +4 dBu range will have the best headroom, while the lower (consumer) -10 dBV range delivers the quietest noise floor. (The range settings on a SPL meter operate the same way, providing a balance between the mic pre amp’s noise level and the expected volume of the signal being measured.)

However, some AV receivers have sub output levels that are strong enough to surpass the capabilities of the -10 dBv setting. If that's the case you need to switch to +4.

Sorry, can’t tell you anything about the signal bleeding issue.







​

Regards,
Wayne


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## pierreye (May 6, 2010)

OK. Will try out the +4db settings. My understanding is either +4db or -10db position will still show the same clip level.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Not so, but you’ll see for yourself when you switch it over. 

Regards,
Wayne


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## pierreye (May 6, 2010)

Thanks Wayne. I try the +4db settings and it no longer clip the input.


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## Dr. Spankenstein (Aug 4, 2006)

I've been reading your issues on AVS and the eD website. Since we both have the 805 and an eD sub, thought I'd chime in.

I recently have been re-visiting my sub calibration via the BFD and have found a few things. It has been necessary for me to check the input level for multiple formats as they seem to differ in terms of signal.
Like you, I found that I was clipping the input to the BFD and was unable to reduce the sub trim enough. This was with: TrueHD, DTS and DTS-MA sources. Dolby Digital and PCM would not sound any good since they had their bass reduced too much. 

The solution is in the "Audio Adjustment" portion of the setup menu. Under "LFE Level" you are able to select a -10dB (or -20dB) trim to a particular format. I applied the -10dB to Dolby THD, DTS-MA and DTS.

Now I can have the main sub trim set to 0dB and they will all be close to the same level when sent to the BFD.

I found the noise floor too raised when utilizing the +4 setting on the BFD.

Experiment yourself and let us know how this works!


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## pierreye (May 6, 2010)

But setting -10db trim to Dolby TrueHD and DTS-MA will lower the sub output 10db lower than other channel. I had solved the driver clanking issue after getting the replacement driver.

FYI, I take the easy way out. I bought a AS-EQ1. One of the reason is I'm using dual sub and BFD doesn't had a build in delay for each channel so it's hard to integrate dual sub if it is not equal distance and same model of the sub. I still use BFD for my L,C,R speaker.


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